IVASA--C.R- 11ltf~51 NASA CR-174657 

Creare TN-371 

I NASA-CR-1746S7 

19850009775 

ANAL yrlCAL AND EXPERIMENTAL INVESTIGATION OF 

RUBBING INTERACTION IN LABYRINTH SEALS FOR A 

LIQUID HYDROGEN FUEL PUMP 

by 

Francis X. Dolan 

Francis E. Kennedy 

Erland M. Schulson 

CREARE R&D INCORPORA lrED 

prepared for 

,. 

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 

NASA Lewis Research Center 

Contract NAS 3-23276 

<ireare 

~ ", I.. ';~.J5 

LANGLEY RESEARCH (;I::NTER 

LIBRARY, NASA 

HAMPTON, VIRGINIA 

---"-----,----------------------------------------- Engineering Research and Development 

Computer Systems and Software 

1111111111111 1111 11111 11111111111111111111111 

NF00423 
No. 

I 

2. Government Accession No. 

4657 

1. Report 

CR 17 

4. Title al 1d Subtitle 

Analy 

Inter 

Fuel 

tical and Experimental Investigation of Rubbing 

'acti on in Labyrinth Seals for a Liquid Hydrogen 

Pump 

7. Author Is) 

Franc is X. Dol an, Francis E. Kennedy, Erland M. Schulson 

9. Perforr ning Organization Name and Address 

Crear 

Box 7 

Hanov 

'e R&D Inc:. 

12. Sponso 

NASA 

21000 

Cleve 

1 

er, NH 03755 

ring Agency Name and Address 

LeRC 

Brookpark Road 

1 and, OH 44135 

15. Supple mentary Notes 

3. Recipient's Catalog No. 

5. Report Date 

August 1984 

6. Performing Organization Code 

B. Performing Organization Report No. 

TN-371 

10. Work Unit No. 

11. Contract or Grant No. 

NAS 3-23276 

13. Type of Report and Period Covered 

Fi na 1 

14. Sponsoring Agency Code 

PI: oject Manager, Robert C. Bill, NASA Lewis Research Center 

Cl eveland, Ohio 

16. Abstrac t 

A com 

to th 

hydro 

Finit 

with 

they 

conta 

Therm 

geome 

situa 

reali 

Hi gh·-

geome 

evalu 

seals 

to be 

rub p 

rub p 

bined analytical and experimental program was carried out to address issues related 

e observed cracking of the titanium knife edges on the labyrinth seals of the liquid 

gen fue'l pump in the Space Shuttle main engine. 

e element analysis of the thermal response of the knife edge in sliding contact 

the wear ring surface shows that interfacial temperatures can be quite high and 

are significantly influenced by the thermal conductivity of the surfaces in rubbing 

ct. 

al shock experiments were carried out using a test specimen similar to the knife edge 

try. These tests demonstrate that cracking of the titanium alloy is po s sib 1 e ina 

tion involving repeated thermal cycles over a wide temperature range, as might be 

zed during a rub in the liquid hydrogen fuel pump. 

speed rub interaction tests were conducted using a representative knife edge and seal 

try over a broad range of interaction rates. Alternate materials were also experimentally 

ated. These tests provide information which can be used to design improved labyrinth 

for the HPFP of the SSME. In particular, plasma-sprayed aluminum-graphite was found 

significantly better than presently used aluminum alloy seals from the standpoint of 

erformance. Ion nitriding the titanium alloy knife-edges was also found to improve 

erformance compared to the untreated baseline. 

rds ISuggested by Authorls)) 

enic 

17. Key Wo 

cryog 

rub i 

labyr 

titan 

therm 

crack 

nteraction 

inth seal 

ium alloy 

al fatigue 

initiation 

18. Distribution Statement 

19. Security Classrf. lof this report) 

Uncla ssified 

20. Security Classif. lof this page) 21. No. of Pages 

Unclassified 

* For sale by the National Technical Information Service, Springfield, Virginia 22161 

NASA-C-168 (Rev. 10-75) 

22. Price' 
TABLE OF CONTENTS 

TABLE OF CONTENTS 

LIST OF TABLES 

LIST OF FIGURES 

SUMMARY 

1 

2 

3 

4 

IN'I'RODUCTION. 

PRELIMINARY ANALYTICAL MODELING OF RUB INTERACTION. 

2.1 Impeller and Wear Ring Analysi.s •• 

2.2 Labyrinth Seal Thermal Analysis •• 

2.2.1 Effect of Contact Length •• 

2.2.2 Alternate Materials Cases. 

2.3 Thermal Shock Analysis 

THERMAL SHOCK EXPERIMENTS • 

3.1 Background •••••••••• 

3.2 Experimental Investigation 

3.3 Test Results •••••••••••• 

3.3.1 Observations and Data Summary 

3.3.2 Discussion of Results. 

3.4 Applicability of Test Results. • 

RUB INTERACTION EXPERIMENTAL PROGRAM. 

4.1 Design Background ••..••• 

4.2 Test Program •••••••• 

4.3 

4.4 

4. ~) 

4.6 

4.2.1 Test Facility Design. 

4.2.2 Test Measurements and Data System •• 

Materials and Coatings . • • • 

Rub Interaction Test Matrix. • 

Test Procedures. • . • • . • • 

4.5.1 Instrument Calibration ••••••••• 

4.5.2 Test Preparation .•.• 

4.5.3 Test 
TABLE OF CONTENTS (Continued) 

APPENDIX C-l - MATERIALS CERTIFICATION 

APPENDIX C-2 - APPLICATION DATA FOR NITROGEN ION IMPLANTATION TREATMENT 

OF KNIFE EDGE DISK 

APPENDIX C-3 - TECHNICAL INFORMATION FOR ALUMINA COATING OF KNIFE 

EDGE DISK 

APPENDIX C-4 - TECHNICAL INFORMATION FOR TUNGSTEN CARBIDE COATING 

OF KNIFE EDGE DISK 

APPENDIX C-S - TECHNICAL INFORMATION FOR ALUMINUM/GRAPHITE 

COATING OF WEAR RING 

APPENDIX C-6 - TECHNICAL INFORMATION FOR YTTRIA STABILIZED 

ZICONIA COATING OF WEAR RING 

APPENDIX D -

APPENDIX E -

APPENDIX F -

STRIP CHART RECORDS FROM RUB INTERACTION TESTS 

A METALLURGICAL EXAMINATION OF A Ti-SAl-2.SSn DISK 

RUBBED AT -196°C AGAINST AN ALUMINUM PAD 

SEM PHOTOMICROGRAPHS OF WEAR SPECIMENS 

ii 
LIST OF TABLES 

TABLE 2-1 ALTERNATE MATERIALS CASES • • 2-14 

TABLE 3-1 THERMAL SHOCK TEST RESULTS 3-4 

TABLE 4-1 HEASURING INSTRUMENTS FOR RUB INTERACTION TESTS • • 4-13 

TABLE 4-2 KNIFE EDGE COATINGS . . . 4-16 

TABLE 4-3 ALTERNATE MATERIALS FOR WEAR RINGS • 4-18 

TABLE 4-4 LABYRINTH SEAL TEST MATRIX. . • . • • 4-20 

TABLE 4-Sa SUMMARY OF TEST RESULTS - BASELINE 

HATERIALS SERIES. . • . • . . • . • • . . • . • • . • . 4-26 

TABLE 4-Sb SUMMARY OF TEST RESULTS - WEAR RING 

:t-'IATERIALS SERIES. • . . . . .. ........•. 4-27 

TABLE 4-Sc SUMMARY OF TEST RESULTS - KNIFE EDGE 

MATERIALS SERIES. . . . . . . . . 4-28 

TABLE 4-6 STRIP CHART DATA CHANNEL IDENTIFICATION · 4-38 

iii 
LIST OF FIGURES 

FIGURE 2-1 FINITE ELEMENT MODEL FOR WEAR RING 

FIGURE 2-2 FINITE ELEMENT MODEL FOR IMPELLER. • 

FIGURE 2-3 DETAIL OF FINITE ELEMENT MODEL FOR 

LABYRINTH FINGERS. . 

FIGURE 2-4 COMBINED STRESSES ON IMPELLER FOR RUB CONDITION 

IMPOSING 260°C INTERFACE TEMPERATURE . 

FIGURE 2-5 COMBINED STRESSES ON WEAR RING FOR RUB CONDITION 

IMPOSING 260°C INTERFACE TEMPERATURE • 

FIGURE 2-6 FINITE ELEMENT MODEL FOR THERMAL ANALYSIS. 

FIGURE 2-7 DETAILS OF FINITE ELEMENT MODEL FOR THERMAL 

ANALYSIS . · · · · · · · · · · · · 

FIGURE 2-8 THERMAL ANALYSIS FOR LABYRINTH SEAL 360° 

CONTACT LENGTH . . . · · · · · · · · · · · · · · 

FIGURE 2-9 THERMAL ANALYSIS FOR LABYRINTH SEAL 180° 

CONTACT LENGTH . · · · · · · · · · · · · · · 

FIGURE 2-10 THERMAL ANALYSIS FOR LABYRINTH SEAL 30° 

CONTACT LENGTH • 

FIGURE 2-11 THERMAL ANALYSIS OF LABYRINTH SEAL WITH ODS 

KNIFE EDGE COATING . · · · · · · · · · · · · · · 

FIGURE 2-12 THERMAL ANALYSIS OF LABYRINTH SEAL ALUMINUM 

OXIDE KNIFE EDGE COATING 

· · · · · · · · · · 

FIGURE 2-13 THERMAL ANALYSIS FOR LABYRINTH SEAL MAGNESIA 

ZIRCONIA WEAR RING SURFACE · · · · · · · · · · · 

FIGURE 2-14 THERMAL ANALYSIS FOR LABYRINTH SEAL ALUMINUMPOLYESTER WEAR RING SURFACE. 

· · · · · · · 

FIGURE 2-15 THERMAL ANALYSIS FOR LABYRINTH SEAL HIGH PURITY 

COPPER WEAR RING • 

FIGURE 3-1 THERMAL SHOCK TEST SPECIMEN. 

FIGURE 3-2 SEM MICROGRAPH OF THERMAL SHOCK SPECIMEN 

CYCLED 3 TIMES 

FIGURE 3-3 SEM MICROGRAPHS OF THERMAL SHOCK SPECIMEN 

CYCLED 10 TIMES. • 

iv 

2-2 

2-3 

2-4 

2-5 

2-6 

2-8 

· · · 2-9 

· · · 2-11 

· · · 2-12 

2-13 

· · · 2-15 

· · · 2-16 

· · · 2-17 

· · · 2-18 

2-19 

3-2 

3-5 

3-6 
LIST OF FIGURES (Cont'd) 

FIGURE 4-1 ASSEMBLY DETAIL (PARTIAL VIEW) FOR HIGH 

PRESSURE FUEL PUMP . . . • 

FIGURE 4-2 KNIFE EDGE TEST SPECIMEN 

FIGURE 4-3 WEAR RING TEST SPECIMEN .. 

FIGURE 4-4 RUB INTERACTION TEST FACILITY ASSEMBLY DRAWING 

FIGURE 4-5 SCHEMATIC OF INTERACTION CONTROL SYSTEM 

FIGURE 4-6 DETAIL OF LN2 FEED RING ASSEMBLY . • . . 

FIGURE 4-7 TEST INSTRUMENTS AND SIGNAL CONDITIONING . 

FIGURE 4-8 TEST NUMBER CODE NOMENCLATURE. . . . . . • 

FIGURE 4-9 PHOTOGRAPH OF PERIPHERY OF DISK SHOWING DEPOSIT 

OF YSZ (TEST TIYZ03) • • • • • • . • . . . 

FIGURE 4-10 SEM MICROGRAPH OF KNIFE EDGE TEST TIYZ03 

FIGURE 4-11 SEM MICROGRAPHS OF ABRASIVE COATINGS ON KNIFE 

EDGE DISKS SHOWING CRACKS .•... 

FIGURE 4-12a STRIP CHART DATA FOR TEST TIAL03 •• 

FIGURE 4-12b STRIP CHART DATA FOR TEST TIAL03. 

v 

4-2 

4-4 

4-5 

4-7 

4-8 

4-10 

4-12 

4-29 

4-32 

4-33 

4-34 

4-36 

4-37 
This Page Intentionally Left Blank 
SUMMARY 

A combined program of analysis and experimentation has been carried 

out to address issues related to the observed cracking of the titanium 

knife edges on the labyrinth seals of the liquid hydrogen fuel pump in the 

Space Shuttle main engine. The cracking is believed to be caused by 

combined thermal and mechanical stresses in the knife edge which occur 

during rub interaction between the knife edge and mating wear ring of the 

labyrinth seal. 

A steady-state finite element analysis examined the thermal response 

of the labyrinth seal geometry with a steady heat flux in the contact zone. 

The heat flux was estimated from a surface plasticity model. The boundary 

condition for the seal configuration in the analysis assumed an infinite 

heat sink at the temperature of liquid hydrogen. This analytical method 

considered the effects of contact geometry (length) and material properties 

on the steady-state temperature achieved at the interface of the knife edge 

and wear ring. The preliminary analysis shows that this temperature can be 

quite high and is significantly influenced by the thermal conductivity of 

the mating surfaces. 

Thermal shock experiments were carried out using titanium test 

specimens with geometry similar to the knife edge. Individual specimens 

were cycled, 1, 3 and 10 times between two high temperatures and the 

temperature of liquid nitrogen. These tests demonstrate that cracking of 

the titanium alloy is possible in a situation involving repeated thermal 

cycles over a wide temperature range, as might be realized during a rub in 

the liquid hydrogen fuel pump. 

High-speed rub interaction tests were conducted using a representative 

knife edge and seal geometry. Tests were carried out with the baseline 

titanium and aluminum knife edge and wear ring material. Alternate 

materials were also experimentally evaluated. A total of 15 tests were 

conducted with the various material combinations, over a wide range of 

interaction rates. These tests provide information which can be used to 

design improved labyrinth seals for the high pressure fuel pump of the 

SSME. In particular, plasma-sprayed aluminum/silicon/graphite was found to 

be significantly better than presently used aluminum alloy seals from the 

standpoint of rub performance. Also, nitrogen ion implantation of the 

titanium alloy knife edge improved rub performance compared to the 

untreated baseline material. 

vi 
1 INTRODUCTION 

In modern high performance turbomachinery, clearances between the 

rotating components and the adjacent stationary structures are reduced to a 

minimum in order to maximize the efficiency of these machines. For 

instance, a labyrinth seal is used on the shrouded impeller of the High 

Pressure Fuel Pump (HPFP) of the Space Shuttle Main Engine (SSME) to 

prevent leakage of liquid hydrogen fuel from the pump discharge to the 

inlet of the pump. The close clearances are maintained between "knife 

edges" on the impeller shroud and stationary "wear rings" which are formed 

in the pump outer case. It has been estimated (Ref. 1) that a decrease in 

pump efficiency of 1 to 2% is incurred if the labyrinth clearance is 

increased by 0.127 mm (0.005 inch). 

Rubbing wear is a common occurrence in high speed turbomachines as the 

impellers and shafts are subjected to rapid transients and body forces 

during engine operation and vehicle maneuvers. The resulting impeller to 

wear ring relative deflections can be substantially larger than predicted 

for normal steady operation. As a consequence, the labyrinth knife edges 

will machine or "abrade" a groove into the opposing wear rings. If the 

knife edges are able to accomplish this in a manner such that most or all 

of the material removal is from the wear rings rather than from the knife 

edges, the net performance loss is minimized upon return of the rotor to 

its nominal operating position (Ref. 2). One quantitative measure for 

determining the acceptability of seal wear behavior is the volume wear 

ratio (VWR). VWR is defined as the ratio of the volume loss of knife edge 

material during a rub to the loss of wear ring material. Usually, VWR < 

0.1 would constitute an acceptable seal wear rate. 

During the course of such interactions, it is just as important that 

the knife edges do not pick up substantial seal material, known as 

"transfer" or "pickup", since this grooves the wear rings even deeper than 

the normal-length labyrinth would have. A seal that allows a knife edge to 

wear it away with minimal occurrence of transfer is known as "abradable". 

Various abradable seal materials have been developed in recent years for 

labyrinth and other gas path seals in turbomachinery. These include: low 

shear strength, plastically deformable materials (Ref. 3), porous sintered 

metals and fibermetals (Refs. 4, 5), and plasma-sprayed porous ceramics 

(Ref. 6). Although each of these materials was designed to abrade easily 

when placed on the stator component of gas path seals, it has sometimes 

been necessary to add hard or abrasive coatings to the rotor component of 

the seal to lessen the wear of the rotor component during seal rubs (Refs. 

7, 8). 

The HPFP was designed with such abradable seals. The stationary wear 

rings are made of 2024 aluminum alloy and are intended to be sacrificially 

worn by the Ti-5Al-2.5Sn alloy knife edges on the impeller shroud. 

However, as described in Reference 1, there is evidence of crack formation 

in the titanium alloy knife edges as a result of cyclic thermal strains 

imposed in the course of rub interactions with the wear rings. 

Creare R&D Inc. has carried out a program of analysis and 

experimentation which addresses some of the issues related to the observed 

cracking of the bill-of-materials (BOM) labyrinth knife edges, and which 

1-1 
examined alternate materials as candidates for the HPFP labyrinth knife 

edges and wear ring. The objectives of this program were to identify the 

role of rub interaction in the initiation of impeller knife-edge cracks, 

and to evaluate alternate seal material/knife edge coating systems. The 

alternate seal material combinations were assessed from the standpoint of 

reducing the incidence of cracking as well as retention of minimum 

clearances. In order to meet these criteria the alternate materials must 

exhibit low disk heating compared to the baseline combination, and the VWR 

must also be less than for the baseline materials. 

Finite element analysis was used to examine the first stage impeller 

and wear ring under combined centrifugal, pressure and thermal loads, and 

to examine the knife edges and adjacent regions of the wear rings with heat 

generation input from a rub. The basic analysis was extended to consider 

different rub geometries (contact length) and alternate wear ring materials 

and treatments to the knife edge. 

Experimental investigations of cracking of the labyrinth finger knife 

edge were carried out in two phases. In the first, test specimens of the 

titanium alloy were subjected to multiple thermal cycles between either of 

two elevated temperatures (593°C and 11500 C) and liquid nitrogen 

temperature (-196°C). These experiments provided a severe thermal shock 

simulation of a rub interaction followed by cooling of the knife edge in 

the surrounding cryogen. 

'1~he second phase experimental program involved actual rub interactions 

between rotating knife edges and wear ring specimens in a cryogenic (liquid 

nitrogen) environment. These tests were conducted with several different 

coatings and materials on the knife edge and wear ring in order to identify 

candidate materials for replacement service in the SSME HPFP. For most of 

the material combinations, tests were conducted at two rates of interaction 

betweE!n the wear ring and the knife edge. 

'1~he test specimens from the thermal shock and rubbing tests were 

metallurgically examined in order to characterize the extent and type of 

failure or wear of the materials in the different -tests. 

Section 2 describes the analysis efforts which were carried out in 

this program and presents results in the form of temperature and stress 

gradients for the HPFP labyrinth fingers and the wear rings. Thermal 

profiles for the alternate materials considered in the analysis are also 

presented. 

The experimental investigations are presented in two separate 

sections. The thermal shock experiments and results are described in 

Section 3 and Section 4 describes the rub interaction tests, the test 

hardware and procedures and a summary of test results. 

l\n overall summary and conclusions from the work carried out in this 

project and recommendations for additional work are presented in Section 5. 

l\ppendix A provides a report on the results of supplementary analysis 

and experiments carried out on this contract. That work included finite 

element modeling of the labyrinth fingers and wear ring for cases having 
rub lengths of 30° and 360°, and also considered aluminum and copper wear 

ring materials. Results for some low-speed rub tests and single-pass 

abradability tests are also presented in Appendix A. 

Appendix B provides a brief analysis of the contact angle and wear 

rate in a rub situation. 

Documentation for the materials used in the experimental phases of 

this program is provided in Appendix c. 

Test data for all rub interaction experiments are presented in 

Appendix D in the form of plots of the temperatures, forces and 

displacements of the test specimens during the incursion period. 

Appendix E describes in detail the metallurgical examination of wear 

components from one test. Micrographs of all wear specimens are included 

in Appendix F. 

1-3 
2 PRELIMINARY ANALYTICAL MODELING OF RUB INTERACTION 

Finite element methods were used in several stages to analyze the 

impeller and seal of the HPFP under conditions of normal pump operation and 

for an assumed rub interaction scenario. This section provides some 

background information on the models and assumptions used in the analyses 

and describes results for specific cases. 

2.1 ~_mpeller and Wear Ring Analysis 

Analyses of the first stage impeller and wear ring were undertaken 

using the steady-state ANSYS code to determine the levels of stresses under 

combined centrifugal (impeller only), thermal and pressure loads. Finite 

element models for the impeller and wear ring were based on pump geometry 

information provided to Creare by the NASA Project Manager. Pump 

environmental conditions (temperatures and pressures) were obtained from 

Reference 9. 

'l'he finite element models for the wear ring and impeller are shown in 

FigurE!s 2-1 and 2-2, respectively, with additional details of the element 

breakup in the labyrinth fingers shown in Figure 2--3. These models were 

used to calculate the combined thermal, pressure and centrifugal stresses 

durin9 a rub. 

In these calculations, the temperatures of the surface elements in the 

rub contact region of the knife edge and wear ring were assumed to be at 

260°C (500°F). This interface temperature resulted from a preliminary 

analysis oft.he thermal response of the seal components having an imposed 

steady heat i.nput of 330 kW/cm2 (2000 Btu/s-in2 ). That heat rate was 

calculated using a surface plasticity model (Ref. 10) that assumes shearing 

of the aluminum wear ring by the rotating knife edge. When compared with 

rub energy data from low-speed knife edge tests performed in support of 

this project (see Appendix A) this heat input rate appears to be high, 

al though temperatures measured in 'the wear ring during the rub tests 

(Section 4.6) are higher than this temperature for some tests. 

'l'he results of the finite element calculations are shown in Figures 

2-4 and 2-5 which display profiles of the combined stresses for the 

impeller and wear ring. The maximum stress level at the tip of the second 

labyr:i.nth finger is only about 270 MPa (39,200 psi) while peak stresses in 

the WE~ar rin9 surface at the point of rubbin9 contact are about 488 MPa 

(70,800 psi). Even imposed cyclically these stress levels are not high 

enough to initiate cracking in the knife edge. 

2. 2 ]~Iabyrinth Seal Thermal Analysis, 

A finite element thermal analysis USin9 the ANSYS code was performed 

to est:imate1:he steady-state tempera.ture distribution at the interface 

between the labyrinth finger and wea.r ring durin9 a rubbing contact. The 

analysis considered different rub contact lengths for the BOM titanium and 

aluminum materials, and also examined the effects of alternate knife edge 

and wear rin9 materials on rub temperatures. 
""T'I 

\I • 1\\\ -,,-

~ ~~- \\\\\\ ...... \ \\~~ \\\\\\\\ 

co-, \ \ \ \ \ \ \ \ 

c::: 1 \\\\\\\ 

;::c \\\\\\\ 

f'T'I \\\)'\\\ r-.:> , \ 

I 

""T'I 

:z: 

----t 

If'T'I 

N 

If'T'I I 

N .. rf'T'I 

Z 

f'T'I 

:z: 

----t 

Z 

0 

c::::J 

f'T'I 

.. 

""T'I 

0 

;::c 

~ 

f'T'I 

:> 

;::c 

;::c 

:z: MOD EL 

co-, Lx 

1.0.00E-.01 MODEL 

'\ 

",1\ 

,,' "'~ '\ ~ ..... ~ ..... 

.... ~ I" .... ~ 

r; -- - ... 

VIE\.I DIR.: ~ ___ 0_1~~_ 

VIEWING D1ST . t . 088E+20 --' ------- PLOT LIt'HTS 

--.---

X ~:~~~~:~~ 

0.03!3Ei-00 

Y 1.185E+00 ----~----.--

z 0.000E-t-0a 

0. BC0E+J()0 -------- JOB: RING1 

26-MAR-82 

09: 14:45 
.... 

FIGURE 2-2. FINITE ELEMENT MODEL FOR IMPELLER. 

2-3 

...J 

UJ 

Q 

o 

z: 

-
FIGURE 2-3. DETAil OF FINITE ELEMENT MODEL FOR 

lABYRINTH FINGERS. 

2-4 
KN I FE EDGE STR ESS 

270MPo 

0-

If) 

oN 

lSI 

(J"l 

>-

(J"l 

:z: 

a: 

ill 

'-"l 

...... 

(..'1 

>-

a:l 

Cl 

ill 

Cl 

...... 

> 

...... 

Cl 

'J 

en 

U.J 

u 

a: 

o 

'-'-

---

3: 

(J1 

o 

a: 

o 

_.J 

(J1 

~ 

,-" 

>-

IT. 

:-:: 

c:. 

a: 

LU 

_J 

w 

CL 

::?: 

FIGURE: 2-4. COMBINED STRESSES ON IMPELL.ER fOR RUB H 

CONDITION IMPOSING 260 0 C INTERFACE TEMPERATURE. 

2-5 
STEP- 1 ITER- 1· TIME- .00 38-RPR-B2 

NDDRL TEMPERRTURES --- FORCES PER RRDIRN 

PEAK STRESS __ __ 

488 M Po B 454 

iEARAING RNALYSIS SISE RNSYS 

FIGURE 2-5. CONB I NED STR ESSES ON 'lEA R RING FOR RUB COND ITiON 

INPOSING 260 0 C INTERFACE TENPERATURE. 

2-6 
The fini-te element model used in this analysis is shown in Figure 2-6. 

It is an axisymmetric representation of the labyrinth finger and knife 

edge, having 316 elements and 392 nodes. A detailed view of the element 

breakup in the contact zone is shown in Figure 2-7. 

The boundary conditions specified in the analysis were: 

1. Temperatures of the nodes at the bottom of the labyrinth finger 

and around the periphery of the wear ring model were specified to 

be at the temperature of the liquid hydrogen (-226°C). 

2. Heat was transferred by convection from the sides of the labyrinth 

finger and the sides of the wear ring adjacent the contact zone to 

the surrounding cryogenic fluid. The convective heat transfer 

coefficient was estimated 1:0 be 12 W/cm2 0C (0.04 Btu/s-in 2 -OF) 

which may be non-conservative, hence underpredicting the interface 

temperatures. Appendix A provides some further discussion of the 

effect of heat transfer coefficient on rub temperatures. 

A heat flux input of 82 kW/cm2 (500 Btu/s-in2 ) was assumed in the 

thermal analysis for a rub making contact on the full circumference of the 

knife edge. 'rhis value of heat flux is on the "high side" of expected rub 

energy dissipation based on previous wear test results provided by the NASA 

Project Manager and from low-speed wear tests at Dartmouth (Appendix A) and 

blade interaction tests at Creare. 

In the thermal analysis, the heat input was assumed to be applied to 

the surface elements of either the labyrinth finger or the wear ring with 

heat flow by conduction into the other member. With this approach it was 

possible to "bracket" the steady-stat:e interface temperature, without 

making any assumptions about a heat_ "split" between the two surfaces. 

2.2.1 Effect of Contact Length 

Three different rub contact length cases were considered: 

1. 360° contact length 

2. 180° contact length 

3. 30° contact length 

The full circumference contact length is somewhat unrealistic since it 

implies a "shrink-fit" situation. However, it does produce a useful upper 

bound estimate of interface temperature and provides a baseline for 

comparisons with alternate materials cases. 

The rub contact analysis in Appendix B shows that the length of the 

wear scar rapidly increases as incursion continues, approaching 130° of arc 

for an incursion depth of 0.25 mm (0.010 inch). Therefore, the thermal 

analysis case having a 180° contact length should produce a realistic 

estimate of interface temperatures. 

The 30° :rub case provides a base for comparison with the results from 

the experimental phase (Section 4) which used a wear ring specimen with an 

arc length of 30°. 

2-7 
.217 I.. 

.185 -

.154 -

\22 -

.11.190 -

.aS8 -

.026 -

-. ~~5 -

-.037 -

- "'69 -

o 

BOUNDARY 

MAINTAINED AT - 226 0 C 

CONVECTION TO LHz 

AT THESE BOUNDARIES 

LA B Y R I NTH FIN G E R 

Ti -5AI ~ 2.5Sn 

WEA R .RI N G 

2024 AI 

13-JUN-82 

BOUNDARY 

MAINTAINED 

AT-226°C 

y 

-.101 t. I I I I I I I I k 

3.16 3.1~ 3.22 3.25 3.29 3.32 3.35 3.38 3.41 3.45 3.48 

.Ra. FING"n WERriAING ~XISYH. MODEL - STATIC RNALYSIS 

FIGURE 2-6. FINITE ELEMENT MODEL FOR THERMAL ANALYSIS. 

2-8 
14-JUN-82 

tiS 

---------_.L 94 

18. 

r--

127 117 18 98 

128 118 11 Bl 9. 

63 

129 1111 tl 82 M 

49 

lSI 12. 11 93 6S 

131 121 11 a. 66 50 

132 122 11 85 67 51 

133 123 11 86 68 52 

13. lZ4 11 87 69 

53 

135 125 11 // 

136 126 ---

----- 29 

38 

4tl. n,~bi:H __ NtHHHlr.l> H~D'/'1. /'1UUtL - :>IHI!~ HNHL.Y!>D btUi'ltiHY HN:>Y:> 

FIGURE 2-7. DETAILS OF FINIlE ELEMENT MODEL FOR THERMAL ANALYSIS, 

2-9 
For the cases in which the rub energy was applied to the labyrinth 

finger, the heat input value was reduced in proportion to the total contact 

length (constant heat flux). 

Results of the thermal analyses for the three contact angle cases are 

shown in Figures 2-8, 2-9 and 2-10. Peak temperatures occur at the 

mid-plane of the contact zone and are not greatly different for the two 

modes of heat application. As expected, interface temperature decreases 

with decreased contact length. 

2.2.2 Alternate Materials Cases 

Several alternate materials were investigated as treatments or 

coatings for the knife edge and as abradable wear ring materials. The 

cases, materials and material properties considered in this phase of the 

analysis are presented in Table 2-1. Properties for the BOM aluminum and 

titanium alloys used for the wear ring and knife edge are shown for 

comparison purposes. 

Thermal analyses were carried out for each alternate material case for 

a rub contact angle of 360°. The material in the mating component of the 

seal was selected as the BOM material used in the HPFP---aluminum for the 

wear ring and titanium for the knife edge. 

Results for the 5 alternate materials cases are shown in Figures 2-11 

through 2-15. As in the other studies, the analysis considered heat 

application individually to the knife edge and to the wear ring. Also, the 

heat flux value assumed for these alternate materials cases was the same 

(82 kW/cm2) as for the baseline material cases. 

The most notable results are the cases with the magnesia/zirconia wear 

pad coating (Case 4, Figure 2-13) and the copper wear pad (Case 6, Figure 

2-15). In the former, the low conductivity coating results in a very high 

interfacial temperature, whereas the copper seal surface enhances heat 

transfer from the rub zone producing a reduction in temperature compared 

with the baseline case with 2024 aluminum (Figure 2-8). 

2.3 Thermal Shock Analysis 

A finite element analysis was performed on the test specimen used in 

the thermal shock tests (see Section 3 for a description of the experiments 

and the geometry of the specimen). This analysis examined the transient 

temperature field within the specimen for a step change in boundary 

temperature and with negligible thermal resistance in the boundary film. 

The specimen was assumed to be initially at a uniform 593°C (llOO°F) and 

then the boundary temperature was changed to -226°C (-375°F) at time t = O. 

The results of this transient analysis indicate that all of the "shocking" 

action takes place in the first few tenths of a second and t~e specimen 

is essentially at thermal equilibrium in less than one second. A similar 

thermal shock is expected to occur as the knife edge rotates out of the 

contact zone in a rub interaction and is quenched by the liquid hydrogen. 
15 roc 

360 DEG. RUB. HERT APPLIED TO HERRRING 

200 0 C 

36Q DEG. RUB. ~ERT RPPLIED TO LRBYRINTH FINGER 

FIGURE 2-8. THERMAL ANALYSIS FOR LABYRINTH SEAL 

360 0 CONTACT LENGTH 

7.-11 

TEMP RNSY S 

1 

TEMP RriS Y 3 
I 

Ira DEG. RUB. ~~~T RPPLIED TO WEARRING 

,20 DES. <:;'3. LfEo,T RPPL::cO TO LR8YRINTH fINGER 

I 

~ 

FIGURE 2-9. THERMAL ANALYSIS FOR LABYRINTH SEAL. 

180 0 CONTACT LENGTH 

2-12 
-----------------------------, 

I 

I 

I 

J 

30 !JEb. PUB. l-lERT RPPLl ED TO WERRRI NG 

- 170 0 C 

------------------------------, 

313 DEG. RUB. HERT RPPLl EO TO LRBYRINTl-l FINGER 

FIGURE 2-10. THERMAL ANALYSIS FOR LABYRINTH SEAL 

30 0 CONTACT LENGTH 

2-13 

! 

I 

I 

I 

I 

-.1 

TE~P '·".-:v.) 
TABLE 2-1 ALTERNATE MATERIALS CASES 

Material properties(l) 

Case No. 

2 

3 

4 

5 

6 

Materials and 

Application 

Plasma-sprayed ODS coating on knife edge; 

0.25 rom thick 

A1 2

03 knife edge coating 0.15 mm thick 

Magnesia-Zirconia coating on wear ring, 85% 

dense, 0.76 rom thick 

Aluminum-Polyester coating on wear ring, fully 

dense, 0.76 rom thick 

99.7% pure copper wear 

ring 

2024 Aluminum, wear ring 

Ti-5Al-2.5Sn, knife edge 

Density 

(kg/m3 ) 

8,040 

3,880 

3,600 

1,385 

8,865 

2,770 

4,490 

Specific 

Heat Capacity 

(J/kg-K) 

462 

752 

460 

962 

385 

870 

535 

Thermal 

Conductivity 

(W/m-K) 

14 

22 

0.82 

75 

396 

112 

7.9 

( 1 ) h . 1 . 1 . T e mater1a d' h . bl 1 d s propert1es 1ste 1n t 1S ta e are eva uate at or near room 

temperature. 

2-14 
'"" :::: '~L C(lSE 2R. HERT RPPLIED TO WERRRING 

1ATERIRL C~SE 28. HEAT RPPLIED TO LRBYRINfH FINGER 

FIGURE 2-11. THERMAL ANALYSIS OF LABYRINTH SEAL 

WITH ODS KNIFE EDGE COATING 

2--15 

TEMP RNSYS 
nYEAIAL CASE SA. HEAT APPLIED TO WEARRING 

~TE~. CRSE 3B. HEAT APPLIED TO LABYRINTH FINGER 

FIGURE 2-12. THERMAL ANALYSIS FOR LABYRINTH SEAL 

ALUMINUN OXIDE KNIFE EDGE COATING. 

2-16 

TEMP p~;s Y5 

TEMP ANSYS 
1883 0 C 

MRTERiRL CASE 4R. 4ERT RPPLIED TO WERRRING 

1340 0 C 

'RTERIRL rRSE 48. HERT RPPLIEO TO LRBYRINTH FINGER 

FIGURE 2-13. THERMAL ANALYSIS FOR LABYRINTH SEAL 

MAGNESIA ZIRCONIA WEAR RING SURFACE 

2--17 

TEMP RliSYS 

I 

I 
266 0 C 

MATERIAL CASE SA. WERT RPPLIED TO WERRRING 

4RTERIAL CRSE SB. HEAT RPPLIED TO LRBYRINTH FINGER 

fiGURE 2-14. THERMAL ANALYS IS FOR LABYR INTH SEAL 

ALUM INUM- POLYESTER WEAR RING SURFACE 

2-18 

TEMP RNSYS 
3PC 

·MATERIAL CRSE 6R. HERT APPLIED TO WEARRING 

1ATERIRL CRSE 6B. HERT APPLIED TO LABYRINTH FINGER 

FIGURE 2-15. THERMAL. ANALYSIS FOR LABYRINTH SEAL 

HIGH PURITY COPPER WEAR RING. 

2-19 

TEMP FlNSYS 
3 THERMAL SHOCK EXPERIMENTS 

3.1 Background 

In a rubbing situation, the labyrinth knife edge is heated locally due 

to energy dissipation at the wear interface. As the knife edge moves out 

of the rub zone (assuming that contact occurs over only a portion of the 

perimeter of the seal) it is subjected to rapid cooling by the surrounding 

cryogenic fluid (liquid hydrogen). Transient, non-uniform cooling of the 

knife edge will induce strains in the material which may result in cracking 

of the knife edge. 

A number of variables may be of importance in producing "quench 

cracks" in the knife edge. Among them are: 

1. temperature differential in the thermal cycle 

2. rate of cooling 

3. metallurgical condition of the specimen (e.g., grain size and 

orientation) 

4. mechanical properties (e.g. thermal expansion coefficient, modulus 

and ultimate strength) 

5. geometry of specimen 

6. thermal cycling (fatigue) 

Although assumptions can be made for certain of these variables and 

calculations can be performed which predict the probability for cracking, 

some uncertainty wfll still remain regarding thermal cracking for specific 

situations. In order to gain further insight to this problem, an 

experimental investigation was undertaken which provided direct evidence of 

cracking of the titanium alloy in a cryogenic quench. 

3.2 Experimental Investigation 

A series of experiments was carried out to subject specimens of the 

Ti-SAl-2.SSn to thermal cycles between either of two elevated temperatures 

and the temperature of liquid nitrogen (-196°C). Specimens were cycled 1, 

3 and 10 times from each of the elevated temperatures (593°C and l150°C) 

and were examined for evidence of cracking after each series of thermal 

cycles. 

The test specimens were fabricated by lathe-turning from a rod of 

annealed Ti-5Al-2.5Sn, as shown in Figure 3-1. The knife edge width (0.76 

mm) and taper approximately match the configuration of the full-size knife 

edge which should provide a realistic simulation of temperature gradients 

during quench. A copy of the certificate of analysis for the titanium rod 

is given in Appendix C-l. 

The lower of the two test temperatures (593°C, 1100°F) represents the 

maximum expected temperature of the knife edge during a "single-pass" rub, 

based on the high side heat flux estimate used in the thermal analysis and 

considering heat transfer to the wear ring and to the surrounding 

environment. The upper temperature (1150°C, 2l00°F) is slightly above the 

a-e transformation temperature for the titanium alloy. 

3-1 
.--2.S4mm 

If 6.35mm 1.57mm 

12.7mm 

~ __ r,_IA._ 10.550 

JLoo 762mm 

FIGURE 3-1. THERMAL SHOCK TE:ST SPECIMEN 

3--2 
Liquid nitrogen was selected as the quench medium for these tests 

because it was more readily available and has reduced handling risks 

compared to liquid hydrogen. 

The issues of hydride formation and possible effects of hydrides on 

thermal cracking in the HPFP environment were considered prior to 

undertaking these tests. The literature on the effect of long-term 

exposure of titanium alloys to a low temperature hydrogen environment 

indicates that hydride formation is unlikely (Reference 11) and therefore 

should not be a contributing factor in the cracking of the knife edge. It 

also seems unlikely that the short-term exposure of this titanium to 

hydrogen in the high temperature rub zones would result in any significant 

hydride formation. 

In the quench tests, the specimens were heated in a furnace having an 

argon gas atmosphere, allowed to hold at temperature for several minutes 

and then were dropped into a container of liquid nitrogen. After cooling, 

the specimens were removed from the nitrogen and then examined for cracks 

using a scanning electron microscope (SEM) at magnifications up to 1000X. 

3.3 Test Results 

3.3.1 Observations and Data Summary 

Despite the protective argon atmosphere during heating, oxidation of 

the specimens occurred. Its extent was limited, however, as evident from 

the gold to blue interference colors on the test specimens, indicative of 

thin «l~m) films. This result is not surprising given the propensity with 

which titanium getters oxygen. 

Grains were evident to the unaided eye after cycling to the higher 

temperature. After one cycle the grain diameter was around 0.7 mm; after 

10 cycles it was closer to 3 mm. Grains were not seen by eye even after 10 

cycles at the lower temperature, presumably because grain growth and 

thermal etching of grain boundaries were less extensive at 593°C than at 

. 1150°C. 

Quenching into liquid nitrogen resulted in a relatively slow 

extraction of heat from the test specimens. This point was evident from 

the observation that boiling occurred in the nitrogen bath for up to about 

5 to 6 seconds after dropping in the specimen. In fact, the bath bubbled 

for about 5 seconds, became quiet, bubbled again for about 1 second, and 

then ceased bubbling. These effects are probably caused by transitions 

through stages of film and nucleate boiling coupled with thermal conduction 

within the specimen. 

The test specimens which were cycled from 593°C to -196°C did not show 

any evidence of cracking even for the specimen cycled 10 times. After 

three of the more extreme shocks (1150°C to -196°C) cracks were seen in one 

area of the test specimen, near to but in from the periphery (approximately 

0.4 mm), Figure 3-2. Several cracks emanating from the periphery were 

observed in the specimen subjected to 10 of the extreme thermal cycles, as 

3-3 
shown in Figure 3-3. These cracks were distributed more or less uniformly 

around the circumference of the disk. The results of the thermal shock 

tests are summarized in Table 3-1 including remarks from the metallurgical 

examination of the test specimens. 

Th 

Qu 

Temp 

~rmal 

ench 

erature 

/-196°C 

C/-196°C 

TABLE 3-1 THERMAL SHOCK TEST RESULTS 

Number of 

Cycles Remarks 

1,3,10 no cracking evident at magnifications 

up to 1000X 

1 no cracking evident 

3 irregular cracks in one area away 

from periphery of knife edge 

10 numerous cracks up to 0.5 mm in 

length, emanating from periphery of 

knife edge, several locations around 

circumference 

3--4 
FIGURE 3-2 SEM MICROGRAPH OF THERMAL SHOCK SPECIMEN 

CYCLED 3 TIM ES 

3-5 

DISK 

PERIPH E RY 
FIGURE 3.3 SEM MICROGRAPHS OF THERMAL SHOCK 

SPECIMEN CYCLED 10 TiMES 

3-6 
3.3.2 Discussion of Results 

An order of magnitude estimate of the life to crack initiation based 

on the total strain range at the disk periphery suggests about 1000 cycles 

to failure even for the more extreme thermal cycle used in these 

experiments. This life calculation is based on (Ref. 12): 

where: 

~T max 

3.50 u 

E 

N -0.6 

f 

strain range = aT~T max 

thermal coefficient of expansion 

maximum temperature differential for thermal strain 

number of cycles to crack initiation 

tensile ductility 100 

ln ( 100-RA) 

RA reduction in area 

E elastic modulus 

o ultimate tensile strength u 

(1) 

Room temperature properties are assumed to apply over the entire range 

and metallurgical stability prevails over the temperature range. 

The observation of cracks after only a few thermal cycles implies that 

simple life prediction methods such as the one cited above may not be 

applicable in a situation involving complex thermal loading. 

In interpreting the cause of cracking, several points should be kept 

in mind: 

1. thermal strains, per se; 

2. contractive strains accompanying the body-centered cubic to 

close-packed hexagonal crystallographic transformation upon 

cooling the alloy below about 1000°C; 

3. the possible effect of grain size (and hence of holding time and 

temperature) on the susceptibility to cracking; 

4. oxygen-induced embrittlement (nitrogen embrittlement seems 

unlikely). 

The importance of thermal strain versus transformation strain could be 

determined through additional experiments in which quenching is done from 

just above and from just below the transformation temperature. The thermal 

3-7 
strain would be essentially the same in both cases, whereas the 

transformation strain would not. In the absence of experimental data, ~2 

is noted that thermal strains in these tests are est~mated to be a~T=lO , 

implying a tensile stress at the periphery of C1 < 10 MPa (145,000 psi). 

This stress may be high enough to nucleate cracks in coarse-grained 

material. Transformation strains (axial) are of a similar magnitude, but, 

because they are imparted at high temperatures, are probably relaxed by 

plastic flow before stresses build up to levels as high as that suggested 

above. It would appear, therefore, that thermal strains are of greater 

concern than the other. Further testing is required before becoming firm 

on this point:. 

If thermal strains per se are the main cause of cracking, then the 

absence of cracks upon cycling from the lower temperature can be explained 

on the basis of lower induced strains. The question which arises, however, 

is why cracking did not occur after the first high-temperature cycle. One 

answer is that insufficient deformation damage was generated to nucleate 

cracks during one cycle, implying the operation of a more complicated 

process of thermal fatigue. In turn, this implies that cracking may occur 

upon quenching from the lower temperature if enough cycles are realized. 

However, as pointed out earlier, conventional life prediction correlations 

grossly overE~stimate the fatigue life in this instance. Another possible 

explanation is that cracking is caused by a combination of thermal strain 

and time-dependent microstructural changes (such as grain growth, hardening 

through oxygen dissolution, and thermal strain induced cracking of a 

hardened surface oxidation layer) which occur during the heating, holding 

and cooling parts of the cycle. If this synergistic process underlies 

cracking, then heating in air to dissolve more oxygen and/or holding for 

longer times at 1150°C before quenching into LN2 should lead to crack 

formation in even fewer than three cycles. ' 

Clearly, the exact origin of the cracks cannot be ascertained without 

further work. 

3.4 Applicability of Test Results 

These thermal shock tests show that cracking of the titanium alloy 

knife edge is possible under conditions of repeated cycles over an extreme 

temperature range. The effect of increased numbers of thermal cycles may 

also result in cracking even from the lower knife edge temperatures 

expected in HPFP rub interactions. 

3--8 
4 RUB INTERACTION EXPERIMENTAL PROGRAM 

This section describes the rub interaction testing which was carried 

out on this project. Some background material is presented in order to 

establish the context for the design of the experimental hardware. Next, 

the test plan is described including the test facility and instrumentation 

design, materials selection and testing procedures. Results from the rub 

interaction tests are presented in the form of data measured during the 

tests, test observations and post-test examinations of the wear specimens. 

4.1 Design Background 

High speed sliding has been identified as the probable cause for 

cracking of the labyrinth seal knife edges in the SSME HPFP. The basic 

mechanism for failure is believed to be localized, thermally-induced 

stresses produced by a rub which combine with the centrifugal and pressure 

loads of normal pump operation to exceed the yield strength of the knife 

edge titanium alloy. 

The basic assembly of the SSME HPFP and details of the labyrinth seal 

under investigation in this project are shown in Figure 4-1. The seal is 

designed to reduce leakage flow of high pressure fuel (liquid hydrogen) 

from the impeller discharge region back to the impeller inlet. The total 

pressure drop across the 4 stages of the labyrinth seal is approximately 

11.8 MPa (1700 psi) and the fluid temperature is about 40K (-387°F) in the 

region of the seal. The design operating speed for the pump is about 

37,000 rpm. 

The labyrinth fingers in the seal are fabricated as an integral part 

of the impeller shroud which is made from Ti-SAl-2.SSn in a fully annealed 

state. The wear ring is fabricated from 2024-T3 aluminum alloy and was 

selected to be sacrificially worn during a rub interaction with the 

adjacent labyrinth finger. In the static, no-load condition, the nominal 

clearance between the knife edges and seal ring is about 0.35 mm (0.014 

inch). This clearance reduces to 0.18 mm (0.007 inch) during pump 

operation as a result of differential thermal contraction and pressure and 

centrifugal loads on the impeller and wear ring. 

A labyrinth seal rub can be induced as a result of transient engine 

operation, an unbalance condition or from body forces on the engine due to 

vehicle maneuvers. The rub is usually just a momentary contact between the 

knife edge and sealing surface over just a portion of the wear ring 

periphery. However, even a short duration contact can result in locally 

high temperatures and stresses and metallurgical transformations can also 

take place. 

High speed rubbing wear is a complex process which generally requires 

experimental verification of designs and materials compatability. Because 

in-service cracking of the labyrinth fingers has been observed (Reference 

1), a testing program was undertaken to provide data on the wear process 

for the bill-of-materials (BOM) labyrinth seal system, and to examine the 

behavior of candidate replacement materials or treatments for the knife 

edge and wear ring. 

4-1 
SHROUD 

LA B YR I NTH 

SEAL 

DETAIL OF LABYRINTH SEAL 

-DIMENSIONS SHOWN ARE 

PRIOR TO LOADING 

-TYPICAL' PINCHED' CLEARANCES 

ARE O.l71mm (O.007Inch I 

FIGURE 4-\. ASSEMBLY DETAIL (PARTIAL VIEW) FOR HIGH 

PRESSURE FUEL PUMP 

4-2 
4.2 Test Program 

4.2.1 Test Facility Design 

The basic test facility comprised a single knife edge rotating at high 

speed in an atmosphere of liquid and gaseous nitrogen, and a wear ring 

specimen which could be moved into contact with the knife edge at different 

rates of interaction and for a controlled interaction depth. In this 

section, the major components and assemblies which make up the rub testing 

hardware are described. 

Knife Edge Disk 

The knife edge disk is shown in Figure 4-2. It consists of a 1.59 mm 

(0.0625 inch) thick disk of Ti-5Al-2.5Sn alloy with its outer periphery 

machined to provide a knife edge configuration similar to that found on the 

labyrinth seals in the HPFP. The outer diameter of the disk (172.7 mm, 

6.80 inch) is approximately the same as the diameter of the first labyrinth 

finger on the impeller shroud, and is the maximum disk diameter which could 

be conveniently accommodated in the test facility. The width of the knife 

edge (0.762 mm, 0.030 inch) exactly matches the labyrinth knife edge and 

the tapered sides preserve the overall thickness and thickness distribution 

of the labyrinth finger. 

Surface treatments and coatings were applied to the knife edge for 

some tests in order to evaluate their resistance to wear in this rubbing 

environment. Section 4.3 describes these alternate materials and their 

selection. 

Wear Ring Specimen 

Figure 4-3 shows the details of the geometry for the wear ring 

specimens used in this experimental program. The wear ring "pad" has a 

radius of curvature of 86.49 mm (3.405 inch) and is 20.3 mm (0.78 inch) 

wide. The difference in radius between the wear ring pad and knife edge 

disk (0.127 mm, 0.005 inch) approximates the nominal "pinched" clearance in 

the HPFP at design operating conditions. 

The pad was machined as an integral part of a mounting plate which was 

used to locate the pad relative to the knife edge disk. As shown in Figure 

4-3, the wear ring specimen was instrumented with two thermocouples located 

below the surface of the pad and in the plane of disk interaction. 

The majority of the rub interaction tests were conducted with a wear 

ring pad fabricated from 2024 T35l aluminum alloy duplicating the basic 

wear ring material in the SSME HPFP. For some tests the aluminum pads were 

coated with abradable materials, and for one test the complete wear ring 

specimen was fabricated from 99.99% pure, oxygen-free copper. More will be 

said about the selection of these alternate materials in Section 4.3. 

4-3 
172 .72 mm D IA. 

I. 59 mm - ....... -N' .. _ 

KNIFE EDGE 

DISK 

TITANIUM 

FIXTURE 

FASTENER (3 ) 

I 

O.762mm - ....... 1.52 mm 

LOCAT IN G 

DOWEL 

PINS(3) 

~ 

TY PIC A L KN I FE 

EDGE IN HPFP 

FIGURE 4-2. KNifE EDGE TEST SPECIMEN 

4- 4 
0.38 mm 

86.49mm RAD. 

( RE F. ) 

0.64 m m 

,.....~-1.18mm 

D IA. 

TH ERMO COUPLE 

LOCATI ON DETAIL 

8 6.49 m m R AD. 

12.7mm -t~~~~~l 

FIGURE 4-3. WEAR RING TEST SPECIMEN 

4-5 

30' 

t 

63.98mm 

63.96mm 

DIA. 

15.2mm 
Rub Interaction Hardware 

A rub interaction test facility was assembled to provide high speed 

rotation of the knife edge disk and controllable interaction between wear 

ring specimen and a knife edge in a cryogenic environment. Figure 4-4 

shows a section elevation view of the test facility and some details of the 

liquid nitrogen injection system. 

In the setup of the test hardware, the knife edge disks were clamped 

between and pinned to Ti-6Al-4V side plates. The disks were concentrically 

aligned to the center of rotation of the assembly during the machining of 

the outer diameter of the knife edge and dowel pins were used to ensure 

repeatability of that alignment during setup of each test disk. This 

assembly was mounted on a drive shaft and was located against a shoulder on 

the shaft and held in place with a threaded nut which provided a clamping 

force of 13 kN (3000 lbf). The drive shaft was supported in two sets of 

angular contact ball bearings in a cartridge which was supported from the 

frame of the test fixture. 

The knife edge disk shaft was connected with a splined coupling to the 

shaft of the drive turbine in Creare's Medium Aerodynamic Component (MAC) 

test facility. This turbine is part of a standard turbocharger package 

having its own radial and thrust bearings and lubrication system. The air 

supply for the drive turbine was provided from laboratory air compressors. 

Turbine speed was controlled by regulating the air flow rate to the 

turbine. With this drive system, rotational speeds of 35,000 rpm were 

achieved in the checkout tests, but test speeds were limited to 25,000 rpm 

(prior to the initiation of a rub) in order to minimize bearing loads and 

to accommodate changeover of knife edge disks without re-balancing of the 

rotating assembly. At 25,000 rpm the tip velocity of the knife edge was 

225 m/s (742 ft/s). 

Wear ring specimens were mounted in a collar assembly on the top of a 

column support (see Figure 4-4). The collar located the wear pad under the 

center of rotation of the knife edge and prevented lateral movement of the 

specimen during a rub interaction. The column could be raised and lowered 

with a hydraulic piston acting through wedge plates at the bottom of the 

column. A linear ball bushing provided lateral support for the column and 

guided its travel during a rub test. Both the rate of travel and the total 

extent of travel of the column were controlled, thereby providing a range 

of interaction rates between the wear specimen and the knife edge and a 

known total interaction depth. 

The major components and subassemblies of the interaction control 

system are shown schematically in Figure 4-5. A brief description of the 

major components and their functions is given below: 

1. A hydraulic piston actuator formed the core of the drive system 

used to force the wear speeimen against the rotating knife edge. 

High pressure hydraulic fluid was supplied to the actuator at a 

controlled flow rate that established the rate of displacement of 

the actuator. The actuator was connected to a sliding wedge at 

the base of the column which translated the horizontal piston 

motion to vertical motion of the column. A range of displacement 

4--6 
~ 

I 

-.J 

LIQUID 

NITROGEN 

FEED RING 

TANGENTIAL FORCE TRANSDUCER 

HYDRAULIC CYLINDER ACTUATOR 

\ I I 7 I "s ....... I~ 

BEARING 

CARTRIDGE 

SUPPORT PLATE ~ 

SPLINED COUPLIN G 

DRIVE 

DISK TURBINE 

ASSEMBLY 

WEAR RING SPECIMEN 

TANGENTIAL FORCE 

TRANSDUCER 

NORMAL FORCE 

TRANSDUCER 

SUPPORT COLUNN 

LINEAR BALL BUSHING 

SLIDING WEDGE PLATE 

FJGURE 4-4. RUB INTERACTION TEST FACILITY ASSEMBLY DRAWING 
KNIFE 

EDGE 

D ISI~ 

HYDRAU LI C ACTUATOR 

WEAR PAD 

RETRACTION SPRING BUSHING 

PULL 

DOWN 

SPRING 

AIR 

SUPPLY DIRECTIONAL 

FLOW CONTROL-...-

VALVE 

t><::I~ n[ SLIDING 

ur====:=r==:7:1:7;7:7~7~~. VI EDG E 

LATCH I N G SO LEN 0 I D 

CYLINDER LATCH 

. 4 - WAY SOLENO I D VALVE 

~ HYDRAULIC 

'------4-------1 ~ 0 I L RES E R V 0 I R 

AIR POWERED 

HYDRAULIC PUMP (16: I) 

FIGURE 4-5. SCHEMATIC OF INTERACTION CONTROL SYSTEM 

4-8 
rates could be accommodated by using different wedge plate angles 

(ratio of vertical to horizontal motion), and by regulating the 

flow rate of hydraulic fluid to the actuator. For this test 

program a single wedge plate angle was used (4.435 degrees) and 

the oi~3f1ow rate was vaEled to pro~~de interactio~2rates from 

2.5x10 mm/s to 2.5x10 mm/s (10 inch/s to 10 inch/s). 

2. The total depth of interaction was controlled by means of a 

pre-set limit switch. Prior to startup of a test, the wear 

specimen was placed in contact with the knife edge and the limit 

switch was adjusted to allow an additional 0.25 mm (0.010 inch) 

travel of the wear ring beyond the contact position. Actuation of 

the limit switch at the end-of-travel released a latch mechanism 

which caused the hydraulic cylinder to be rapidly retracted with 

the help of a spring, reversing the direction of travel of the 

piston and sliding wedge. Simultaneously, the column was pulled 

down with pre-loaded springs, breaking contact between the wear 

ring and the rotating knife edge. 

3. A linear variable displacement transducer (LVnT) measured the rate 

and extent of interaction of the wear specimen. The body of the 

LvnT was fixed to the frame of the interaction device while the 

center core moved with the hydraulic piston. The wedge plate 

angle provided a fixed ratio of 12.8:1 between the measured 

displacement of the actuator rod and the vertical motion of the 

wear specimen. 

Cryogenic Environment Control 

In the HPFP the labyrinth seal on the first stage impeller operates in 

liquid hydrogen at about 47°K (-375°F) (Reference 9). For the rub tests 

this cryogenic environment was simulated by cooling the rotating knife edge 

and the wear ring specimen using liquid nitrogen having a temperature of 

nOK (-321°F). 

Liquid nitrogen (LNZ

) was supplied from a pressuriz~d tank through 

double-wall, insulated 11nes to a feed ring which surrounded the knife edge 

disk (Figure 4-4). The LN2 was distributed in a manifold to four inlet 

ports located around the clrcumference of the feed ring. Four outlet ports 

were also located in the feed ring in order to drain away excess LN2 . 

Figure 4-6 shows some of the details of the internal arrangement of 

the LN2 feed ring and the means by which the knife edge disk was cooled. 

Each inlet port supplied the LN2 to two jets which directed the fluid at 

opposite faces of the knife edge. The LN2 filled the cavity surrounding 

the periphery of the disk, being held there and transported in the 

direction of rotation by the centrifugal "pumping" action of the disk in 

the small cavity. 

The feed ring did not enclose the disk over the 30° arc where it 

interacted with the wear specimen (see Figure 4-4). At that location some 

of the LN2 was allowed to escape from the feed ring cavity in order to cool 

the wear specimen pad. 

4-9 
BEARINIG 

CA RTR ID GE INSULATION 

LIQUID NITROGEN IN 

(DRAIN PORTS SIMILAR) 

FEED RING 

COOLING JETS (2) 

(2.54mm DIAJ 

DRAIN GAP 

NOM INAL CLEARANCE~2.3mm 

FIGURE 4-6. DETAIL OF LN2 FEED RING ASSEMBLY 

4-10 
In operation, the LN2 flow rate to the test hardware was manually 

controlled to meet two crlteria: 

1. the temperature of the wear pad was cold and stable, 

2. excess liquid nitrogen was seen to be escaping from the four lines 

which were connected to the drain ports in the feed ring. 

The design and operation of this system assured that the rub 

interaction tests were conducted in an environment which provided a 

realistic simulation of the conditions in the SSME HPFP. 

Test Fixture 

The interaction control device and the bearing cartridge were mounted 

on a heavy steel plate which was bolted to the MAC rig support fixture. 

This support fixture was very rigid and provided a convenient means for 

aligning the test hardware to the turbine drive. 

4.2.2 Test Measurements and Data System 

The measurements of major interest in these experiments were the 

forces and temperatures developed in the wear specimens as a function of 

the interaction rate and knife edge speed for the different materials 

systems investigated. Figure 4-7 shows a schematic representation of the 

instruments and signal conditioning used in these tests. Some additional 

information for each of the instruments is provided in Table 4-1. 

Temperature 

The wear ring specimen temperature was measured using two 

thermocouples located below the surface of the wear pad and in the plane of 

disk interaction (Figure 4-3). The thermocouples were made from 0.25 mm 

(0.010 inch) diameter wire and had a junction diameter of approximately 

0.64 mm (0.025 inch). One thermocouple was installed 0.38 mm (0.015 inch) 

below the surface of the wear pad while the second was at a depth of 0.64 

mm (0.025 inch). The thermocouple beads were firmly positioned at the ends 

of the drilled holes and were held in place by cementing the insulated 

wires where they exited from the installation holes. The small wires and 

intimate contact with the wear pad insured fast response and a temperature 

measurement which was representative of the local temperature beneath the 

wear scar. 

The thermocouples were connected to a reference temperature zone block 

and their outputs were amplified to 5V full-scale prior to input to the 

data acquisition computer. A calibration system was used to record the 

zero offset and voltage gain for the thermocouple amplifiers before each 

test. 

For some of the tests the thermocouple amplifier output exceeded 5V 

full-scale, which was beyond the input range of the analog-to-digital 

converter in the DAS computer. 

4-11 
WEAR 

RADIAL 

DISPLACEMENT PROBE 

11 

SPEED PICKUP 

POWER SUPPLY I 

AND SIGNAL r--.-----/ 

CONDITIONER I 

FREQUENCY TO 

VOLTAGE 

CONVERTER 

I 

I 

SPEC I MEtt 

THERMOCOUPLES 

THERMOCOUPLE ZONE BLOCK I 

---t 

, 

--

,-1--1- TANGENTIAL FORCE ,. RANSDUCER 

~ ~c;" IS 0" Q 

/) 0 

~Voi)1>6 

v 00' v1,voo 

LINEAR DISPLACEMENT TRANSDUCER 

'"" 

"V 

~ 

,.., 

...., 

,... 

,... 

ICE BATH 

REFERENC E 

.... 

THERMOCOUPLE 

AMPLI F I ERS -

AND GAIN 

CALIBRAT ION 

P IEZO E LEe TRIC 

I 

~ 

~ 

~ 

I~ 

I~ 

Ig 

CHARGE AMPLlFIEHS I~ 

I:=: 

I -8>------1, 

l~ i 

M __ -,-------------tPOWER SUPPLY I L, __ ,--------~--,__f AND S IGNAL ~---t CONDITIONER I 

FIGURE: 4-7. TEST INSTRUMENTS AND SIGNAL CONDITIONING 

I 

I 

4-12 
TABLE 4-1 MEASURING INSTRUMENTS FOR RUB INTERACTION TESTS 

Test 

Measurement Instrument Description 

Wear Specimen Thermocouple Bead-type grounded junction 

Temperatures (2) 0.25 mm wire diameter; Type K 

(Chromel-Alumel); Omega 

Engineering Catalog 

No. 5TC-GG-K 

Tangential Rub Force Load Cell Piezoelectric force 

transducers; resonant 

frequency - 200 kHz; 

load range 7.5 kN; Kistler 

Model 9001 

Normal Rub Force Load Cell Piezoelectric force 

transducer; resonant frequency 

- 65 kHz; load range 89 kN; 

Kistler Model 9041 

Interaction Rate Displacement Linear, variable differential 

Transducer transformer; 12.7 mm range; 

Schaevitz Engineering 

Model 250 DC 

Disk Speed Tachometer Magnetic pickup on hex nut; 

frequency-to-voltage converter 

Disk Radial Displacement Eddy current probe; 

Displacement Transducer Bently-Nevada Series 190-

3000 

4-13 
Force 

Tangential and radial (shear and normal) forces were measured during 

the rub interaction tests using two piezoelectric load cells mounted below 

the wear ring specimen. The normal force transducer transmitted the 

vertical load component from the wear specimen to the support column, 

whereas the tangential force transducer formed the link between the wear 

pad and the support collar. Both transducers were connected to charge 

amplifiers which converted the charge sensitive output to a voltage 

proportional to the applied force. 

The time constant of the force transducers and charge amplifiers was 

greater than 100 seconds during ambient operation and calibration of the 

force measuring system. However, the DC stability during actual rub tests 

does not appear to be that long. It is possible that the cryogenic 

environment affected the resistance of the transducer and cables, resulting 

in greater charge leakage during test operation. 

Interaction Rate 

The rate of interaction between the knife edge and the wear pad was 

measured with a linear variable differential transformer (LVDT) connected 

to the hydraulic actuator arm. The LVDT provided a DC voltage proportional 

to the change in position of the arm, which was translated to wear pad 

linear motion through the sliding wedge. The interaction rate was 

determined by calculating the rate of change of actuator position, divided 

by the. wedge translation ratio. 

Rotational Speed 

The rotational speed of the knife edge disk was measured with a 

magnetic pickup which sensed the rotation of a hex nut on the end of the 

high speed shaft. The pulse output produced by the probe was monitored on 

a digital counter and was input to a frequency-to-voltage converter for 

recording by the data acquisition computer. 

Disk Displacement 

The radial displacement of the knife edge disk was measured to provide 

an indication of test rig balance and overall "health" for the test 

operator. An eddy current probe was aligned to measure the change in 

clearance gap between the probe face and one of the side plates used to 

clamp the disk specimens. That probe produced a voltage output 

proportional to the clearance gap which was linear for the small gap 

changes experienced. 

Data Acquisition System 

All of the instrument outputs were conditioned to 5V full-scale level 

and were connected to Creare's data acquisition computer. The computer is 

a Digital Equipment Corporation PDP 11/70 with a separate microprocessor 

for control of data acquisition using a built-in multiplexer and AID 

4-14 
converter. This system was capable of recording data at an aggregate 

sampling rate (total number of AID conversions) of 12 kHz. For these 

experiments the force, displacement and speed measurements were recorded at 

1000 samples per second and the temperatures were recorded at 250 Hz each. 

4.3 Materials and Coatings 

As described earlier, the materials used in the HPFP are Ti-5Al-2.5Sn 

alloy for the impeller and 2024-T3 aluminum alloy for the wear ring.* The 

aluminum is expected to be abraded or worn away by the titanium labyrinth 

fingers during a rub interaction, but some cracking of the titanium has 

been observed during testing of the pump. Therefore, several alternate 

materials were considered as candidates for possible upgrades of the 

labyrinth seal to improve its performance in a rub event. 

In considering a change of materials systems, emphasis was given to 

low wear rate of the labyrinth fingers and structural integrity of the 

labyrinth components, even following repeated interaction. Many materials 

were considered for this experimental evaluation and a preliminary thermal 

and stress analysis was used to screen candidate materials. The selection 

of the final materials was based largely on expected success in favorably 

impacting the wearability of the seal system and availability of the 

materials for this project. 

Bill-of-Materials Knife Edge and Wear Ring 

The knife edge disks were fabricated from titanium alloy sheets with 

5% aluminum and 2.5% tin. A certificate of analysis for the material used 

on this project is included in Appendix C-I. All disks were made with this 

same material, even those which were later treated for wear resistance or 

with abrasive coatings. 

The wear ring specimens used in the baseline tests and for testing 

with alternate knife edge treatments were made from 2024-T35l aluminum 

alloy. The material certification for the aluminum bar stock is also 

included in Appendix C-l. 

Knife Edge Treatments 

Three alternate treatments and coatings were used for the titanium 

knife edge disks as described in Table 4-2. One of the treatments involved 

nitrogen ion implantation (ion nitriding) of the knife edge. This surface 

modification procedure is known to improve the wear characteristics of 

components in sliding contact (Ref. 13). The process of ion nitriding 

involves injecting high energy nitrogen ions into a shallow layer of a 

substrate material to effect both physical and chemical modifications of 

* One turbopump drawing provided to Creare----Rocketdyne Drawing No. 

RS007550 Sheet 2----shows the use of copper plating on the wear ring 

surfaces instead of aluminum. We are not certain of the in-service 

configuration of the HPFP seals, although the contract workscope specifies 

2024-T3 aluminum for the BOM seal evaluation. These comments are recorded 

here because of the adverse wear characteristic of the copper wear ring 

observed during our rub tests as described in Section 4.6.1. 

4-15 
* 

Treatment Code* 

TN 

AO 

'l'C 

TABLE 4-2 KNIFE EDGE COATINGS 

Vendor 

Spire Corporation 

METCO Incorporated 

Union Carbide 

Corporation 

(Linde Division) 

Description 

nitrogen ion implantation on 

knifI7edge; ion flux of 

2xlO /cm2 at 180 keV; see 

Appendix C-2. 

flame-sprayed alumina-titania 

(METCO 101B-NS) to thickness of 

0.2 mm on molydenum-nickel--

aluminum bond coat (METCO 447) 

thickness 0.075 mm; see Appendix 

C--3; outer diameter finished by 

grinding to final 101B coating 

thickness of 0.076 mm. 

Detonation-Gun application of 

tungsten carbide-cobalt-chromium 

coating (UCAR LW-15) to thickness of 0.23 mm; see Appendix 

C·-4; outer diameter finished by 

grinding to final LW-15 coating 

thickness of 0.076 mm. 

The TrE!atment Code is a mnemonic abbreviation which is used in the test number 

identification. 

4-16 
the substrate. For this specific application the nitrogen ion flux was 

2xl017 /cm2 at an energy of 180 keV. Based on the calculated depth profiles 

in Appendix C-2, the peak ion concentration is estimated to be 1022 

ions/cm3 at a depth of about 0.2 ~m. No post-treatment machining of the 

disks was necessary prior to their use in the rub tests. 

The other two treatments shown in Table 4-2 involved the application 

of abrasive coatings to the knife edge in order to enhance its resistance 

to wear in a rub situation. The alumina-titania coating (METCO 101B-NS) 

has found applications on clearance control surfaces in air-breathing 

turbomachinery, whereas the tungsten-carbide coating (UCAR LW-15) has been 

used in cryogenic pump applications. More details of the properties and 

uses for these two coatings are provided in Appendices C-3 and C-4. 

Wear Ring Alternate Materials 

Two abradable coatings for the aluminum wear ring and a pure copper 

wear ring were evaluated in the experimental program. These alternate wear 

ring materials are briefly described in Table 4-3. The coatings, a 

aluminum-silicon-graphite composite (35% graphite, 7% porosity) and an 

yttria-stabilized zirconium oxide composite (YSZ) having 21.5% porosity 

were selected on the basis of being readily abraded or worn away during a 

rub interaction. Both of these materials have seen use as abradable 

components, although no prior cryogenic applications are 'known. Because 

these coatings are considered by the vendor (METCO) to be developmental, 

detailed product information is not available. Some processing data and 

photomicrographs of the applied coatings are provided in Appendices C-5 and 

C-6. 

In addition to the coatings described above, a pure (99.99%), 

oxygen-free copper wear ring was evaluated as a possible replacement for 

the aluminum wear ring. The primary justification for selecting copper as 

a replacement seal is its increased thermal conductivity compared to 2024 

aluminum (about a factor of 2 higher conductivity at cryogenic 

temperatures). The thermal analysis discussed in Section 2 showed that use 

of a copper wear ring substantially reduced the rub zone temperature for a 

model which assumed constant heat input at the rub interface. 

4-17 
* 

Treatment Code* 

AG 

YZ 

co 

TABLE 4-3 ALTERNATE MATERIALS FOR WEAR RINGS 

Vendor 

MET CO Incorporated 

MET CO Incorporated 

Creare R&D Inc. 

Description 

flame sprayed aluminum-sili.congraphite composite; 35% graphite 

(METCO CE-2074A) to thickness of 

0.51 rom on METCO 447 bond coat; 

see Appendix C-5; coating 

finished to 86.49 rom radius of 

curvature-final coating thi.ckness 0.38 mm. 

flame-sprayed yttria stablized 

zirconia coating; 21.5% porosity 

(METCO CE-2l98A) to thickness of 

0.51 rom on bond coat of 

METCO 447; see Appendix C-6; 

coating finished to 86.49 rom 

radius of curvature-final coating thickness 0.38 rom. 

99.99% pure, oxygen-free copper; 

machined to same configuration 

as BOM aluminum wear ring 

specimen. 

The Treatment Code is a mnemonic abbreviation which is used in the test number 

identification. 

4-18 
4.4 Rub Interaction Test Matrix 

The rub interaction experimental phase was designed to meet two 

objectives: 

1. Evaluation of the performance of the labyrinth seal configuration 

under realistic conditions of speed, interaction rate, and 

operating environment (cryogenic temperature). 

2. Evaluation of alternative knife edge treatments and abradable wear 

ring coatings, for some test conditions. 

A total of 15 tests were conducted in a matrix of three series as 

shown in Table 4-4. The Baseline Series of tests compares seal system 

behavior using the BOM knife edge and wear ring materials over a wide range 

of rub interaction rates. The second series of tests examined several 

alternate wear ring materials. Only a single test was carried out with the 

copper and YSZ coatings because of the adverse wear performance experienced 

at the interaction rate shown in Table 4-4. Tests at two interaction rates 

were carried out with the aluminum graphite wear ring coating. For the 

knife edge materials test series, the BOM aluminum wear ring was used. 

Each test used new wear components, i.e. no knife edge disks or wear pads 

were used for more than a single test. 

Detailed descriptions and documentation of the alternate materials 

used in these tests are provided in Section 4.3 and in Appendix c. 

Besides the materials variations, the only other test parameter 

employed was rub interaction rate, I. The interaction rate is defined as 

the rate, in units of radial distance, at which the knife edge and wear 

ring are forced together. For the baseline tests the interaction rate was 

varied over 2 orders of magnitude while for the alternate materials tests I 

covered a smaller range. The range of I selected for these tests has been 

used in other experimental investigations of wear (Reference 6), in which I 

has been shown to exert a major influence on the relative wear between the 

rotating and stationary components. 

4.5 Test Procedures 

All of the tests conducted in this program followed the same basic 

procedures for setting up the test hardware, preparing the specimens, 

carrying out the actual rub tests and examining the test specimen after the 

rub. 

4.5.1 Instrument Calibration 

The instruments and data system used for recording test data were 

calibrated during the experimental phase of this project. 

1. The normal and tangential force transducers were calibrated, along 

with their respective charge amplifiers, by recording the 

amplifier voltage output with a known load (mass) applied to the 

load cells. 

4-19 
TABLE 4-4. LABY RINTH SEAL TEST MATRIX 

Test Knife 

Series Edge 

Material 

BaselinE BOM titanium(l) 

Wear Ri n g BOM titanium 

BOM titanium 

BOM titanium 

Knife E( ge ion-nitrided 

titanium 

alumina-titania 

coating 

tungsten-carbide 

(1) Bill--of-MatE!rials (BOM) knife edge 

B 

c 

a 

c 

y 

z 

B 

Wear 

Ring 

Material 

OM aluminum (2) 

.' 

opper 

luminum-graphite 

oating 

ttria-stabilized 

irconia coating 

OM aluminum 

B OM aluminum 

B OM aluminum 

Total 

Interact 

Rates 

(mm/s) 

0.0016 to 0.13 

0.025 

0.018, 0.15 

0.022 

0.021, 0.1 

0.018, 0.11 

o. all, 0.12 

No. of Tests 

material is Ti·-5Al-2.5Sn. 

(2) BOM wear ring material is 2024-T351 aluminum. 

(3) ThreE 

each 

~ tests at average interaction 

at 0.0016 and 0.13 mm/s. 

rate of 0.012 mm/s and one test 

4-·20 

No. of 

Tests 

5 (3) 

1 

2 

1 

2 

2 

2 

1'-,) 
2. Thermocouples for measuring the wear pad temperatures were 

standard commercial items with known temperature-to-emf 

characteristics. New thermocouples were used for each test 

specimen. The thermocouple amplifiers were calibrated for each 

test by voltage substitution. 

3. The LVDT used for measuring displacement of the sliding wedge in 

the interaction controller was calibrated by recording its output 

voltage for a known displacement of its center core measured with 

precision laboratory verniers. Conversion of LVDT displacement to 

displacement of the wear specimen was directly related to the 

angle of the wedge plate (horizontal to vertical ratio of 12.8:1). 

4. Calibration of the rotational speed signal involved comparison of 

the output voltage (proportional to speed) with the reading of a 

digital counter which was connected directly to the speed pickup. 

In addition, these speed signals were compared with the frequency 

of the vibration signal from the radial displacement probe, as 

displayed on a spectrum analyzer. 

5. The disk radial displacement probe was calibrated by recording the 

output voltage from its signal conditioner at several values of 

clearance between the probe tip and the outer periphery of the 

side disks which support the knife edge. The calibration was 

undertaken at ambient temperature (~ 20°C) over the linear range 

of the probe. 

6. Voltage meters and counters used for calibration and for recording 

test data were calibrated by Creare's Electronics Laboratory, 

which provides for annual calibration of primary measuring 

instruments by outside services, with calibrations traceable to 

NBS. 

7. The analog to digital converter in the data acquisition computer 

is calibrated by Digital Equipment Corporation on a semi-annual 

schedule. 

4.5.2 Test Preparation 

Prior to initiation of a rub test, the test specimens were inspected 

to insure that they conformed to the design specifications and the test 

facility was checked for proper operation. 

Other pre-test checkouts and verifications are listed below: 

1. Thermocouples in the wear pad were checked for polarity and 

relative response rate prior to installing the wear pads in the 

test rig. The thermocouples were connected to the data system and 

the pad was quickly cooled using ice. The outputs were checked 

for consistency and new thermocouples were installed, if 

necessary. 

4-21 
2. The diameter of each knife edge disk was measured prior to 

installation in order to determine the extent of knife edge wear 

resulting from the rub interaction. The diameter was measured 

by comparison with a reference bar using a precision height gauge 

having an estimated accuracy of 1.3 ~m. 

3. Following inspection of the wear specimens, they were installed in 

the test rig, all nitrogen (gas and liquid) lines were connected, 

instruments were connected to the data system, and the air supply 

and lubricating oil systems for the drive turbine were brought 

on-Line. 

4. The balance of the assembled hardware was checked at this point by 

operating the disk up to test speed (25,000 rpm) and monitoring 

the radial displacement of the disk and the bearing temperatures. 

It was our experience that the as-built tolerances on the knife 

edge disks did not significantly affect overall rig balance, and 

rebalancing with each disk would have provided only marginal 

decreases in the disk radial displacement. The peak-to-peak 

radial displacement of the disk was less than about 0.04 mm 

(0.0015 inch) for most of the tests; rebalancing would have 

reduced this to about 0.025 mm (0.001 inch). 

5. The interaction rate was checked before each test, and adjusted if 

necessary. 

6. The depth of interaction was set prior to each test, after the rig 

had been cooled using liquid nitrogen. This was accomplished by 

manually traversing the wear specimen so that it just made contact 

with the periphery of the knife edge disk (not rotating) and then 

setting the limit switch to permit an additional 0.25 mm (0.010 

inch) of travel of the specimen beyond that contact point. The 

traverse mechanisms and wear specimen were then retracted to 

provide approximately 0.13 mm (0.005 inch) clearance between the 

pad and disk prior to start of the test. 

4.5.3 Test Operation 

Initiation and operation of a test proceeded quickly once all 

preparations were satisfactorily completed. 

1. Thermocouple amplifier gains and offsets were checked using the 

built-in gain calibration system and were recorded on the DAS 

computer. 

2. The environmental chamber surrounding the test rig was purged with 

gaseous nitrogen to remove any moisture which could condense and 

form ice when the liquid nitrogen was introduced. 

3. Test rig speed was increased to the desired pre-rub value (25,000 

± 500 rpm), and the rub specimens were cooled by injecting liquid 

nitrogen (LN?) into the caliper assembly described in Section 

4.2.1. The LN2 flow rate was increased until excess liquid was 

observed to be issuing from the drain lines and the wear pad 

temperatures, monitored with digital volt meters, were stable. 

4·-22 
4. When the temperature of the wear pad had stabilized and with the 

disk speed steady at the desired pre-rub value, the interaction 

device was actuated, causing the wear ring to move toward the 

knife edge disk. At that same time the data acquisition computer 

started recording signals from the test instruments. Some test 

data were also manually recorded in the test log book, e.g. 

initial speed, pad temperatures, LVDT reading, and disk 

peak-to-peak radial displacement. 

5. The rub test proceeded until the limit switch reversed direction 

of travel of the interaction controller, breaking contact between 

the 'knife edge and wear pad and signaling end of test to the 

operator. 

6. Shutdown of the rig involved closing the air supply to the 

turbine, securing LN2 feed to the test section, terminating the 

computer data sweep and bringing other support equipment to the 

at-standby condition. 

4.5.4 Post-Test Inspections 

After shutdown, the test rig was allowed to warm back to ambient 

conditions before disassembly was initiated. The following describes the 

inspections which were routinely performed for the test specimens. 

1. Both the wear ring and knife edge were examined in-place for 

evidence of failure or abnormal wear. The components were marked 

with an indelible pen to indicate rub direction and orientation to 

aid in interpretation of wear patterns. 

2. The knife edge disk diameter was measured using the same method 

and apparatus as in the pre-test inspection. The depth of the 

scar in the wear pad was measured using a depth gauge. Other 

noteworthy observations of the condition of the wear specimens 

were recorded. 

3. Following these inspections at Creare, the test pieces were 

packaged and transferred to Thayer School of Engineering 

(Dartmouth College) for detailed metallurgical evaluation. This 

work involved optical and scanning electron microscope (SEM) 

examination of the wear specimens, energy-dispersive X-ray 

spectroscopy (EDX) to identify material transfer resulting from 

the rubs and more detailed investigations for some test specimens. 

4.5.5 Test Data Reduction 

Immediately following completion of each test, the raw data acquired 

by the computer were plotted in the form of strip charts (parameter vs. 

time). The time interval for the plots included the duration of the rub 

interaction period, plus a precursor period of steady, no-rub data and a 

short postscript following retraction of the wear specimen. Thermocouple 

amplifier gains were calculated from the pre-test calibration data, and 

initial and peak temperatures of the wear pad recorded during the tests 

were calculated. 

4-23 
The duration of the interaction was determined by examination of the 

strip chart data plots. Initiation of the rub was assumed to occur at the 

time when the load cells first indicated a force signal above their 

baseline noise level. The termination of a -rub was quite clearly marked by 

the step change in the output of the interaction position sensor (LVDT). 

The difference between these two times was taken to be the duration of the 

rub. 

Interaction rate was determined from the indicated change in position 

of the interaetion device during the time period of the rub. Because the 

rate is relatively constant throughout the interaction period, an average 

rate was calculated as the total displacement divided by rub duration. 

The volume wear ratio (VWR) between the knife edge and wear pad was 

calculated for each pair of test materials based on the measured disk 

diameter reduetion and depth of wear scar: 

VWR 

volume loss of knife edge 

volume loss of wear pad 

For the situation where the reduction in diameter and depth of wear scar 

are small relative to the radius of curvature, VWR can be approximated: 

VWR 

where: 

2nd wd (b.rd) 

1/67fr w (d) p p 

disk radius of curvature 

pad radius of curvature 

width of knife edge 

width of wear scar 

reduction in disk radius due to wear 

depth of wear scar 

This relationship can be somewhat simplified by setting rd = rand 

w = w , reasonable assumptions for the present situation. ThRn, d p 

VWR 6 b.D 

d 

where ilD = reduction in the disk diameter 

4.6 Test Results 

(2) 

(3) 

The data available from the rub interaction tests include the 

measurements of forces, temperatures, speed and interaction rate, total 

wear of the knife edge and wear ring. and the findings from the 

metallurgical examinations. This seetion provides a general overview of 

the test results, highlighting significant observations for specific tests 

and describes the "strip chart" and metallurgical data in detail for one 

test. Strip chart data for all of the tests are presented in Appendix D 

and the metaLlurgical data are found in Appendix F. 

4-24 
4.6.1 Data Summary 

Fifteen rub interaction tests were undertaken, providing data on 7 

materials systems (combinations of wear ring and knife edge materials) over 

a broad range of interaction rates, and including repeat tests for the 

baseline materials combination. A summary of results for these tests is 

presented in three parts: 

Table 4-5a: 

Table 4-5b: 

Table 4-5c: 

Baseline Materials Tests 

Evaluation of Wear Ring Materials 

Evaluation of Knife Edge Materials 

The Test Number used in these tables is a mnemonic description of the 

major test parameters--materials and interaction rate--and is used 

frequently in this report to identify the computer-plotted "strip chart" 

data and the SEM micrographs. Figure 4-8 provides a guide to the test 

numbering system. 

The data tables show the average interaction rate, the depth of the 

scar in the wear pad, reduction in disk diameter and the calculated volume 

wear ratio (VWR). The estimated uncertainties in the measurements of wear 

scar depth and disk diameter reduction are 0.025 mm and 0.0013 mm, 

respectively. Assuming these measurement errors are random, i.e. not 

systematically biased high or low, the uncertainty in VWR can be calculated 

from: 

where 

(llVWR) :2 

Ll VWR 

ll(llD) 

f\.d 

(4 ) 

calculated uncertainty in volume wear ratio 

estimated uncertainty in measured disk wear = 0.0013 mm 

estimated uncertainty in measured scar depth = 0.025 mm 

The uncertainty in VWR is also included in Table 4-5 for those cases where 

VWR could be calculated. 

Other tabulated data include the reduction in rotational speed during 

the rub (the air flow to the drive turbine was held constant throughout the 

interaction period of a test resulting in some change in speed due to the 

friction torque at the rub interface) and the total interaction time 

estimated from the strip-chart records. The column labeled "Test 

Observations" provides miscellaneous comments recorded by the test 

operators during the tests or during post-test examinations of the test 

specimens and data. 

4-25 
,j:>. 

I 

IV 

Cl' 

! 

I 

TABLE 4-5a SUMMARY OF TEST RESULTS - BASELINE MATERIALS SERIES 

I I I Wear 

Knife Wear Interaction Scar 

Test Edge Ring Rate,nun/s Depth 

Number Material Material (inch/s) nun (inch) 

TIAL02' BOO Titanium BOM Aluminum -2 

13xlO -2 0.33 

(0.5IxI0 ) (0.013) 

TIAL03 BOO Titanium BOM Aluminum. -3 

16xl0 -3 0.25 (est) 

(0.64xI0 ) (0.010 est) 

BOO Titanium BOM Aluminum -3 TIALl3 9.9x10 -3 0.25 to 0.30 

(0.39xI0 ) (0.010 to 

0.012) 

BOM Titanium BOM Aluminum -3 'l::':!:.A.L23 10.9xI0_ 0.25 to 0.30 3 (O.43xlO ) (0.010 to 

0.012) 

BOM Ti tanium BOM Aluminum -4 

TIALC4 16.5xI0_ 0.20 4 (0.65xI0 ) (0.008) 

(1) Disk diameter reduction not available so VWR not calculated. 

(2) Disk diameter increased due to pickup, so VWR not calculated. 

Disk , Volume , Disk 

Diameter Wear Speed 

Reduction Ratio Reduction, 

nun (inch) (uncer- rpm 

tainty) 

-2 0.13xI0_6 0.023 1,800 

(50x10 ) (±0.02) 

- NA (1) 3,000 

-2 0.13xI0_ 0.027 6 9,000 

(50x10 ) (±0.03) 

-3 8.89xI0_ 0.19 4,000 4 (3.5xIO ) (±O.l) 

-2 +2.16xl~4 NA(2) 1,000 

(+8.5xI0 ) 

! Total I 

Interaction 

Time, s Test 

Observations 

2.4 Peak temperatures 

reached at end of 

interaction 

9.1 Double-peak temperature and force 

measuremen ts; 

aluminum transferred I to knife edge 

34 Very high seal surface temperature; 

melting & cracking 

of aluminum in wear 

scar, smearing of 

aluminum 

Test data terminated 

early due to computer 

failure; peak temperatures not,as high 

as in Test TIALl3 

131 Cyclic temperatures 

and forces; small 

speed excursions; 

wear scar appears 

scuff~d; build-up 

of aluminum on knife 

edge disk 
"'" I 

~ 

-..j 

Test 

Number 

TICU03 

TIAG02 

TIAG03 

TIYZ03 

Knife 

Edge 

Material 

BOO Titanium 

BOM Titanium 

BOM Titanium 

BOM Titanium 

-----

TABLE 4-5b SUMMARY OF TEST RESULTS - WEAR RING MATERIALS SERIES 

Wear Disk Disk 

Wear Interaction Scar Diameter Volume Speed 

Ring Rate,mrn/s Depth Reduction Wear Reduction 

Material (inch/s) mrn (inch) rom (inch) Ratio rpm 

(uncertainty) 

Oxygen-free, -3 <0.05 (est) -2 25.4xlO_ >9 16,000 3 7.62x!g 

99.99% pure (1.0xlO ) «0.002) (3xlO ) (±2) 

copper 

Aluminum/ -2 0.33 est -2 

14.5xlO -2 0.13xlQ6 0.023 <500 

Silicon/ (0.57xlO ) (0.013 est) (50xlO ) (±0.02) 

Graphite 

Coating 

(METeO 

CE2074A) 

Aluminum/ -3 0.25 -3 

18xlO -3 3.2xlO -4 0.075 500 

Silicon (O.71xlO ) (0.010) (1.25xlO ) (±0.09) 

Graphite 

Coating-

(METCO 

CE2074A) 

-3 nil -2 Yttria- 22.4xlO_ »10 25,000 3 53.3xlQ3 

Stabilized (0.88xlO ) (21xlO ) 

Zirconia 

Coating 

(METCO 

CE-2198A) 

--------- -- ~---- - ----- _ .. _---- ------

Total 

Interaction 

Time, s Test 

Observations 

9.3 High temperature 

peaks recorded 

(>275°C); large reduction in speed; 

considerable reduction in disk diameter, material deposited in wear scar 

1.6 Very small forces & 

temperature changes; 

only slight speedreduction 

11. 5 (est) Very small temperature changes; speed 

and force changes 

small 

10 to 15 Large speed reduction 

-2 sec into test, 

speed dropped to 0 

at -10 sec; sample 

retracted at -15 sec; 

titanium deposited on 

wear pad; some-YSZ 

adheres to disk 

------- -- ----
.I» 

I 

N 

(X) 

Test 

Number 

I 

TNAL02 

TNAL03 

AOAL02 

AOAL03 

TCAL02 

Knife 

Edge 

Material 

Ion Ni trided 

Titanium 

Ion Nitrided 

Titanium 

Alumina/ 

Titania 

Coating 

(METeO 

101B-NS) 

Alumina/ 

Titania 

Coating 

(METeO 

101B-NS) 

Tungsten 

Carbide 

Coating 

(UCAR LW-15) 

TABLE 4-5c SUMMARY OF TEST RESULTS - KNIFE EDGE MATERIALS SERIES 

Wear 

Ring 

Material 

BOM Aluminum 

BOM Aluminum 

BOM Aluminum 

BOM Aluminum 

BOM Aluminum 

. Interaction 

Rate,mm/s 

(inch/s) 

-2 

10.4xlO -2 

(0.4lxlO ) 

2lxlO-3 

(0.S25xlO-3) 

-2 10.6xlO 

(0.417xlO-2) 

• 7 ~ • ~-3 .I. .:;>X.lV_3 (0.69x19 ) 

-2 l2.lxlO 

(0.477xlO-2 ) 

I 

Wear 

Scar 

Depth 

nun (inch) 

0.25 

(0.010) 

0.25 

(0.010) 

0.305 

(0.012) 

0.25 

(0.010) 

0.33 

(0.013) 

I 

Disk 

Diameter 

Reduction 

mm (inch) 

-2 +4.7xlO 

(+1.S5xlO-3 ) 

nil 

-2 

0.13xlQ6 

(50xlO ) 

~ • n-2 .:>X.l.U -3 

(1.2xlO ) 

-2 +6.47xlO 

(+2.55xlO-3)] 

. Volume 

Wear 

Ratio 

(uncertainty) 

NA(l) 

0 

(±0.03) 

0.025 

(±0.02) 

0.72 

(±O.OS) 

NA(l) 

Disk 

. Speed 

Reduction 

rpm 

2,500 

3,400 

700 

4,000 

1,000 

Total 

i Interactioni 

Time,s 

I 

2.6 

15.3 

2.45 

13.7 

2.6 

Test 

Observations 

Some aluminum buildup 

on disk periphery; 

very large surface 

temperature may be 

result of exposing of 

surface thermocouple 

during rub; T>320oC 

Temperatures & forces 

cycled 3 times during 

rub; thin (0.025 mm) I layer of aluminum deposited on segment 

of disk periphery 

Peak temperatures 

occur at end of 

interaction 

Disk coated with 

aluminum from wear 

pad; speed, temperature & normal 

force cycled during 

rub period 

Peak temperatures 

occur at end of inter 

action; buildup of 

aluminum on disk 

periphery 

-3 I -2 TCAL03 I Tungsten I BOM Aluminum I llxlO 0.25 1.lxlO 0.24 2,400 25.5 Temperatures & normal 

I Carbide I I (0.435xlO-3

) I (0.010) (4xlO4

) (±0.04) force c~cle during I 

Coating rub per~od I I WeAR LW-15) I I I I I 

(1) Disk diameter increased due to transfer so VWR not calculated. 
TEST NAME 

~ ~ * * 

Interaction Rate (Nominal) I -2 2 = 12xlO_ mm/s 3 3 = l2xlO_4 mm/s 

4 = 12xlO mm/s 

Replication Number 

0 = first test 

1 = first repeat 

2 = second repeat 

Wear Ring Material 

AL = BOM Aluminum 

CU = Copper 

AG = Aluminum/Graphite 

(METCO CE2074A) 

YZ = yttria-stabilized 

ziconia 

(METCO CE2198A) 

Knife Edge Material 

TI = BOM Titanium 

TN = nitrided Titanium 

AO = alumina-titania 

(METCO lOlB-NS) 

TC = tungsten/carbide 

(UCAR LW-lS) 

Figure 4-8. Test Number Code Nomenclature 

4-29 
Baseline Materials Tests 

A total of 5 tests were conducted using the BOM materials for the -4 

knife edge an~~2wear ring covering interaction rates ranging from 16. 5xlO 

mm/s !2 l3xlO . mm/s. Three of the tests were run at an intermediate rate 

('" 10 - mm/s). 

At the high interaction rate (Test TIAL02) there was only slight wear 

of the knife edge (VWR ~ 0.02), whereas the test at the lowest interaction 

rate (TIAL04) resulted in a slight increase in disk diameter due to pickup 

otlf aluminum from the wear scar. The tests at the intermediate rate 

(TIAL03, TIAL13 , TIAL23) showed a range of VWR from slight (VWR ~0.03) to 

moderate (VWR ~0.2). 

Cyclic temperature and force measurements were observed for some of 

these tests, i.e. for tests at the lower incursion rates, I <0.02 mm/s. As 

a rub progressed, the wear ring temperatures would rise to a maximum, 

followed by a rapid drop back to or near the starting (cold) temperature, 

followed by one or more repetitions of this cycle. The normal and 

tangential force signals exhibited the same cyclic behavior and in phase 

with the temperature cycles. Although not as clearly defined, the 

rotational speed also tended to cycle synchronously with the temperature 

and force measurements. The strip chart plots discussed in Section 4.6.2 

illustrate this periodic nature of the rub interaction between the knife 

edge and wear ring. 

The observed cyclic behavior might be related to a process of wear 

which involves plastic deformation of the wear pad accompanied by 

increasing pad temperature, followed by "tearing away" of wear pad 

material, perhaps due to plastic flow, fracture, melting or a combination 

of these. As material is removed, the interference between disk and wear 

ring is momentarily eliminated, reducing the rub forces and heat input to 

the pa.d, allowing the pad to cool down. The continued incursion of the 

wear ring specimen sets the cycle into motion again. 

At the high interaction rate, the pad temperature and force 

measurements did not cycle in the shorter time of incursion, suggesting 

that the wear proceeded more uniformly than in the tests at lower 

interaction rates. 

Wear Ring Materials Tests 

Four tests were conducted in the series to evaluate alternate wear pad 

materials and coatings. In two of the tests the knife edge suffered 

extensive wear (VWR » 1) when rubbed aga.inst a wear pad of copper (TICU03) 

and a wear pad coated with yttria-stabilized zirconia (TIYZ03). In the 

other two tests (TIAG02 and TIAG03) the relative wear rates were low 

(VWR < 0.1) and other test measurements (forces, temperatures, rotational 

speed) indicated that the aluminum/graphite coating has good abradabi1ity 

in this knife edge rub situation. 

Copper was proposed as a candidate seal material (and shows up as an 

alternate in some HPFP drawings-see Section 4.3) based on the preliminary 

thermal analyses, which predicted lower rub interface temperatures because 

of thE! higher thermal conductivity of copper when compared to aluminum. In 

spite of this better "heat-sinking" capability, the copper/titanium system 

4--30 
apparently is not compatible in a sliding wear situation. For the test 

reported here, the disk underwent a substantial diameter reduction (0.076 

mm) with some of the disk material being deposited in the wear scar. Also, 

the wear pad temperatures exceeded 275°C even with the larger thermal 

conductivity of the copper. (The maximum values could not be measured due 

to the limited range of the thermocouple amplifier for that test.) 

In the test with the YSZ coating, the wear rate of the disk was quite 

high. Nearly all of the interaction involved reduction in the disk 

diameter (0.53 mm), leaving a slight build-up of material on the wear pad 

surface. The rubbing loads caused the disk to cease rotating within about 

10 seconds after initiation of the rub. During disassembly of the test 

components, some material presumably YSZ, was found to be fused to the 

knife edge (Figure 4-9). Further evidence of the aggressive wear on the 

knife edge is seen in Figure 4-10 which shows several small cracks at the 

corner of the knife edge. 

Because of the adverse behavior of the copper and YSZ wear surf?ce 

materials only a single test was undertaken with each. Even though the 

Al/Si/C wear pad produced a favorable rub situation, there was still some 

loss of knife edge material in the two tests. At the higher interaction 

rate the change in disk diameter was only barely perceptible, but 

examination of the wear pad using SEM/EDX turned up evidence of titanium in 

the wear scar which had transferred from the knife edge during the rub. 

The lower interaction rate test produced a measurable diameter change with 

an estimated VWR of 0.075. The wear rates with the aluminum/graphite 

coating are comparable to those in which the titanium knife edge was rubbed 

against the BOM aluminum. 

Knife Edge Materials Tests 

The tests to evaluate alternate knife edge materials followed the 

original test plan, incorporating 3 different knife edge treatments, each 

at two interaction rates for a total of 6 tests. All of the treatments 

showed VWR < 1 with the minimum VWR, or pickup, occurring at the higher 

interaction rate for each material. The wear rate for each of these 

alternates is comparable to the untreated titanium disk when rubbed against 

aluminum at the high interaction rate. The nitrided titanium disk showed 

the lowest overall wear of the three alternate materials tested, and had 

even lower wear than the BOM titanium. 

Even though the two abrasive knife edge coatings (alumina/titania and 

tungsten/carbide) had favorable wear in the tests at high interaction rate, 

there is evidence of cracking of the coatings (see Figure 4-11) near the 

outer edge of the disk. These cracks were probably raised by combinations 

of thermal and mechanical stresses during the rub interaction tests. The 

presence of cracks calls into question the long-term structural integrity 

of knife edge coatings in this application. 

These tests showed the same cyclic behavior of pad temperatures and 

rub forces at the lower interaction rate as described earlier for the 

Baseline tests. At the higher interaction rate, the pad temperatures 

increased monotonically throughout the interaction period reaching a 

maximum value at the end of interaction. The maximum temperatures were 

higher than the peak temperatures measured for the same material at the 

lower interaction rate. 

4-31 
DEPOSIT 

DISK 

PERIPHERY 

FIGUIRE 4- 9. PHOTOGRAPH OF PERIPHERY OF DISK 

SHOWING DEPOSIT OF YSl (TEST TIVl03) 

4-32 
FACE 

OF 

DISK 

PERIPHERY OF DISK 

----------~~----------

FIGURE 4-10. SEM MICROGRAPH OF KNIFE EDGE 

TEST TrYl03 

4-33 

ED GE 
( a ) 

DISK ~",. E DG E 

( b) 

DISK EDGE 

~ , .... , 

~DISK EDGE 

, ~ DISK EDGE 

(a) TUNGSTEN CARBIDE COAliNG - TEST lCAL02 

(b) ALU~INAI TITANIA COATING - TEST AOAL02 

FIGURE 4-11. SEM MICROGRAPHS OF ABRASIVE 

COAT(NGS ON KNIFE EDGE DISKS 

SHOWING CRACKS 

4-34 
4.6.2 Strip Chart Records 

Time-dependent data from the rub interaction tests were recorded by 

the Creare data acquisition computer as described in Section 4.2.2. 

Following each test, these data were plotted in the form of "strip charts", 

i.e. plots of measured parameter as a function of time, for the duration of 

the rub interval. Some of the general observations from these records were 

discussed in Section 4.6.1. In this section, the results from one test 

(TIAL03) are presented and described in greater detail, providing a guide 

to interpretation of these data. Strip charts for all 15 rub interaction 

tests are available in Appendix D. 

Force, speed and displacement data from test TIAL03 are shown in 

Figure 4-12a, and the temperatures are displayed in Figure 4-12b. All of 

the test data are plotted in units of volts (measured at the computer) 

versus time in seconds. (Time = 0 at the start of the computer data 

sweep.) The strip plots are labeled with a data system channel number and 

an abbreviated instrument name. Table 4-6 identifies the measurements with 

their respective data system channels and provides conversion factors from 

volts to engineering units. Note that the temperature measurements in 

Figure 4-l2b do not have a simple conversion factor due to the non-linear 

output of the thermocouples, especially at the cryogenic temperature. 

Instead, the strip plots have been annotated with the pre-rub temperature 

and the peak temperature observed during the rub. 

Both sets of plots are marked with vertical arrows noting the 

beginning and ending of the rub (12.1 sec and 19.2 sec, respectively). The 

start of the rub was deduced from the response of the normal force 

transducer (Channel 100) wherein its signal level rapidly increased above 

the background "noise" level at the time the wear pad first contacted the 

rotating knife edge. The end of the rub is clearly marked by the step 

change in the output of the interaction device position indicator (Channel 

103). This step change accompanies the retraction of the hydraulic 

actuator which allows the wear pad to be pulled away from the disk. 

Several features of the data in these plots were common to many of the 

tests. For example, the force transducer (Channel 100) shows periodic 

"bursts" of high frequency oscillation over the interval of the rub. The 

disk speed also has a cyclic behavior--initially decreasing during the 

early rub time, then stabilizing, followed by another speed decrease during 

the second period of oscillatory rub forces. Wear pad temperatures (Figure 

4-12b) are also cyclic in many of the tests. The temperatures begin to 

increase shortly after the rub starts, reaching a peak just as the rub 

forces cease, followed by a period of cooling and then reheating as the rub 

continues. 

This cyclic behavior was described earlier with the suggestion that it 

may be caused,by a process involving thermal softening and material loss 

due to plastic flow, fracture, or melting, which briefly relieves the 

interaction forces, allowing the pad to cool down. Another possible 

explanation for the thermal cycling is a thermoelastic instability in which 

the interaction between thermal expansion and wear causes non-uniform 

contact between the knife edge and wear pad, resulting in localized "hot 

spots" which can move along the line of contact. Thermoelastic instability 

4-35 
START VOLTSXO.099~mm 

END 

~ .................. . 

OF 

RUB ~. __ ~~ ...... ~ ... ,.= .........,............. ROJsl 

i • _______ t 

_2~AL SPECIMEN DISPLACEM,E_N_T ___ • ____________ (_--1 

E.5 .1.02 PRDX PRB v LTSXO.216: mm 

DISK RADIAL DISPLACEMENT 

en 

I-: 

~-E .. 5.1...-.. ___ ---'-___ -'--____ ---'-__ , _____________ --1 

o 3 .. " 

> 

~ .. ll 

ROTATIONAL SPEED 

~------~------~----~----.----------~----~ 

.1 1iJ., iGSlJ~! 2 ViOL T5 X 0.445- k N 

NORMAL LOAD 

_ ..:1 L--------'--------'---------'----,-~---___::_~----_::J. 

jl 1~ 14 1~ 1B 2~ ~2 

Tl"E l.sec_} 

FIGURE 4-120. STRIP CHART DATA FOR TEST TIAL03 

4-36 
S TART OF RUB END OF RUB 

.4;17 5lJBT i 

SUBSURFACE TEMPERATURE 

1---~--'--~---lINITIAL TE~PERATURE 

C/) . - I I 5 '1 C 

~-~L-____ ~ ______ ~ ____ ~ ______ ~ ____ ~ ____ ~ 

..J 

~ ~ ~b 5.lJflfTj 

NEAR-SURFACE TEMPERATURE 

~ 1 

~ , , ······· ........ · ..·· .... · ..... · ....... T· .. · ... ·-...... ··········-·········l···· 

INITIAW TEMPERATURE 

-jIlIOC ~ 

-4L-____ ~ ______ ~ ____ ~ ______ ~ ____ ~ ____ ~ 

12 !Z 14 16 18 C£ 

TIllE (S8C.) 

FIGURE 4-12b. STRIP CHART DATA FOR TEST TIAL03 

4-37 
TABLE 4-6 STRIP CHART DATA CHANNEL IDENTIFICATION 

Data Channel 

and Name 

96 SURFT 

97 SUBT 

99 KISLRl 

100 KISLR2 

101 MAG PKUP 

102 PROX PRB 

103 LVDT 

Measurement 

Wear pad near-surface 

temperature 

Wear pad subsurface 

temperature 

Wear pad tangential 

force 

Wear pad normal force 

Disk rotational speed 

Disk radial displacement 

Seal specimen. displacement 

Conversion to (1 

Engineering Units ) 

(2) 

(2) 

kN = volts x 0.4448 

kN = volts x 0.4448 

RPM = volts x 104 

mm = volts x 0.216 

mm = volts x 0.099 

(l)The conversion factors apply to the voltage scales on the data plots 

:Ln Figure 4-12 and in Appendix D. 

(2)There is no single conversion factor for the temperature scales. The 

amplifier gain and offset must be accounted for, as well as the non-

_inear thermocouple outputs in order to convert volts to °e. In 

order to simplify data interpretation, the initial and peak temperatures for test TIAL03 are noted on Figure 4-l2b and on the temperature 

plots in Appendix D. 

4--38 
has been analytically examined in combination with surface wear for disk 

brake systems (Reference 15) and the existence of transient temperature 

patterns has been observed in other experimental investigations involving 

sliding contact wear (References 16, 17). 

In the 5 tests at the high interaction rate (I > 0.1 mm/s), thermal 

and force cycling were not observed. The strip plots for these tests 

(Appendix D) show that rub forces (peak-to-peak) remained relatively 

constant during the incursion period and wear pad temperatures continuously 

increased until the incursion was ended by retraction of the wear specimen. 

Apparently in these tests the wear proceeded as a more or less steady 

process, compared with the tests at lower interaction rates. 

4.6.3 Metallurgical Inspection Results 

The wear pad and knife edge specimens were inspected following the 

tests using optical and scanning electron microscopes to locate and 

document, if any, cracks in the rub surfaces. The SEM was also used to 

record topographic features of the wear specimens. Energy-dispersive X-ray 

spectroscopy (EDS) was used in conjunction with the SEM to find evidence of 

suspected material transfers occurring during the rub interactions. 

The specimens from the first interaction test (TIAL03) received close 

scrutiny, particularly the disk, because of the concern for possible 

cracking of the titanium knife edges. Reports on the as-found conditions 

of these specimens clearly describing and illustrating the transfer of 

aluminum to the knife edge, are included as Appendix E. Although numerous 

cracks were observed in the transferred material, detailed examination of 

the disk periphery produced no evidence of cracks in the titanium knife 

edge itself. 

Appendix F contains sets of SEM photomicrographs of the wear specimens 

from the remaining 14 rub tests. Each set includes several photographs 

covering a range of magnifications for both the wear pad and knife edge 

from a single test. The dominant feature seen in the metallurgical 

examination of the wear specimens was the transfer of materials between the 

rubbing surfaces. Except for the abrasive coatings discussed in section 

4.6.1, no cracks were observed in the knife edge disks. 
4.6.4 Comparison with Other Test Results 

Although the test results presented here are the only known published 

data from rub tests at cryogenic temperatures, most of the materials tested 

here had previously been studied by other investigators in rub tests at 

higher temperatures. Most of the results of this study were, in fact, 

similar to those of earlier, higher temperature tests. 

The poor rub performance of copper relative to aluminum in these 

cryogenic tests was similar to that found in room temperature and 900°F 

tests of seal specimens against Ti-6Al-4V alloy blade tips (Refs. 3 and 

is). As was the case in our cryogenic knife edge tests, the copper rub 

specimens caused much more blade tip wear than did aluminum rub specimens 

(Ref. 1S). After some of those tests a copper-titanium eutectic was found 

in the rub zone (Ref. 3); evidence that localized surface temperatures had 

reached at least 8SSoC. Although we have been unable to definitely confirm 

the presence of an eutectic on our copper rub specimen (test TICU03), there 

was some indieation that such melting may have occurred (Figures F-S, 

Appendix F). In any event, the metallurgical compatability between copper 

and titanium (~ould have been responsible for the large frictional energy 

loss and knife edge wear in the rub test of copper. 

It: might be noted that single-pass abrasion tests, in which a sharp 

abrader was rubbed once past a rub specimen, showed that copper abraded 

more easily than aluminum at both room and cryogenic temperatures (Appendix 

A). The difference between those results and our rub test results can be 

attributed to the difference in wear mechanism. In a knife edge/rub strip 

interaetion the primary mechanism for wear particle removal is one of 

p1astie deforInation due to shear tractions at the rub interface. In a true 

abrasion situation, as in the single pass tests of Appendix A, chip 

formation is the primary wear particle removal mechanism. This latter 

mechanism is less influenced by adhesive interactions than is the former. 

It appears that copper would fare well as a rub strip material only in 

cases where it saw chip-forming abrasive interaction with sharp abraders 

and such interactions would not be expected in labyrinth seals. 

The relatively mild rub behavior with the aluminum/graphite composite 

was similar to results of higher temperature tests by other investigators. 

It was shown in Reference 4 that plasma-sprayed aluminum graphite rub 

strips yielded considerable reductions in normal and friction forces 

compared with aluminum rub strips in knife edge tests at room temperature. 

The beneficial presence of graphite in the aluminum silicon graphite 

material may have facilitated near-:surface deformation during a rub and, 

therefore, made wear particle removal easier. Some wear of the titanium 

knife edge still occurs however (Ref. 4). 

The yttria-stabilized zirconia material used in test TIYZ03 is similar 

to that developed for use in the high temperature environment seen by high 

pressure turbine gas path seals (Ref. 6). Although they have better rub 

behavior than most other materials at those high temperatures, their room 

temperature abradabi1ity is known to be worse than that of low shear 

strength metals or porous metals (Ref. 2). Our tests show that their 

cryogenic temperature abradability is also relatively poor. 

4-40 
Room temperature tests of abrasive coatings for seal applications have 

shown that alumina and tungsten carbide coatings can result in small 

reductions in rub surface temperatures and rub forces over those obtained 

with uncoated rotors (Ref. 7). Such was also the case in our cryogenic 

tests. It was also noted by others (Ref. 7) that cyclic or intermittent 

rub behavior occurs with some of the coated disks, similar to that observed 

in many of our tests with coated knife edges. One potential difficulty 

with abrasive treatments is that they lose their effectiveness with time. 

As we found in our tests, transfer of rub strip material can load up the 

coating, much as happens with grinding wheels (Ref. 8), and that the sharp 

abrasive grits (of the alumina coatings) can be worn with time, making them 

less effective as abraders. 

Implantation of nitrogen ions has proven to be effective in reducing 

the wear of a variety of metallic surfaces (Ref. 13). In our tests it 

appeared to reduce knife edge wear quite effectively. There is some 

question about long term benefits, though, because of the very thin 

implanted layer (Appendix C-2) and the tendency of some aluminum transfer 

to occur. These questions could best be addressed by further rub tests, 

perhaps using other rub strip materials, such as aluminum-silicongraphite, against ion nitrided disks. 

4~1 
5 CONCLUSIONS AND RECOMMENDATIONS 

This project has produced several important results in connection with 

the observed cracking of labyrinth seal knife edges in the liquid hydrogen 

turbopump and has identified a material which might be a candidate coating 

for the wear ring seal surface for improved wear performance. 

Major conclusions drawn from analysis of the finite element modeling 

and from the results of the experimental phases are: 

1. An aluminum/silicon/graphite wear surface coating exhibited the 

most favorable behavior in the rub interaction tests and should be 

considered as a possible alternate material for this application. 

2. Nitrogen ion implantation of the titanium knife edge improved the 

wear performance when rubbed against an aluminum seal. 

3. Finite element modeling of the heat conduction in the mating 

labyrinth finger and wear ring coupled with realistic heat input 

assumptions or with interactive models of the wear process can be 

useful to help screen materials for wear surface applications. 

4. Cracking of the titanium knife edge is possible in a situation 

involving multiple thermal cycles between an elevated temperature 

and the temperature of a cryogenic fluid. 

5. Rub interaction tests over a broad range of interaction rates did 

not produce cracking in the titanium knife edge, although cracks 

were observed in the layer of aluminum transferred to the knife 

edge. 

6. The cryogenic rub test results were similar in most respects to 

those compiled by other investigators in rub tests at higher 

temperatures for the various test materials. 

Several recommendations can be made for additional work in this area 

to apply the results for improving labyrinth seal wear behavior. 

1. Thermal analysis methods shoUld be used to screen candidate wear 

surface materials prior to their first use in seal systems. 

2. Presently available data from different wear situations--

geometries, speeds, environmental conditions, incursion 

rates--should be correlated with existing wear models or should be 

used to improve models in order to provide appropriate inputs to 

the thermal analysis. 

3. Additional rub interaction testing of the ion-nitrided knife edge 

and the aluminum/graphite wear coating should be undertaken with 

an expanded range of application parameters. Tests might be run 

with these two materials in combination, or with either one in 

combination with other seal materials. Other tests might be run 

in which the concentration of ions is broadened relative to the 

distribution in the specimens tested here (Appendix C). These 

tests are expected to provide data to design an improved labyrinth 

seal for the HPFP. 

5-1 
6 REFERENCES 

1. NASA; SPACE SHUTTLE MAIN ENGINE (SSME) LIQUID HYDROGEN TURBOPUMP 

IMPELLER SEAL PROGRAM; RFP3-365665, NASA Lewis Research Center, June 

29, 1981. 

2. Ludwig, L.P. and Bill, R.C.; GAS PATH SEALING IN TURBINE ENGINES; ASLE 

Trans., Vol. 23, Jan. 1980, pp. 12-22. 

3. Schell, J.D. and Schwab, R.C.; PROGRAM TO DEVELOP SPRAYED, PLASTICALLY 

DEFORMABLE COMPRESSOR SHROUD SEAL MATERIALS; NASA CR-165237, General 

Electric Co., Jan. 1980. 

4. Bill, R.C. and Wisander, D.W.; FRICTION AND WEAR OF SEVERAL COMPRESSOR 

GAS-PATH SEAL MATERIALS; NASA TP-1128, Jan. 1978. 

5. Bill, R.C. and Shiembob, L.T.; FRICTION AND WEAR OF SINTERED 

FIBERMETAL ABRADABLE SEAL MATERIALS; J. Lubrication Tech., Trans. 

ASME, Vol. 99, 1977, pp. 421-427. 

6. Shiembob, L.T., Stewart, O.L., and Bill, R.C.; DEVELOPMENT OF SPRAYED 

CERAMIC SEAL SYSTEM FOR TURBINE GAS PATH SEALING; J. Engrg. for 

Power, Trans. ASME, Vol. 101, Oct. 1979, pp. 549-555. 

7. Vogan, J.W. and Stetson, A.R.; APPLICATION OF ABRASIVE COATINGS TO 

CLEARANCE CONTROL IN THE GAS TURBINE; J. Engrg. for Power, Trans. 

ASME, Vol. 102, 1980, pp. 113-119. 

8. Hermanek, F.J., Jr.; COATINGS LENGTHEN JET ENGINE LIFE; Source Book on 

Wear Control Technology, Metals Park, OH: ASM, 1978, pp. 368-370. 

9. Lockheed-Huntsville Res. & Engrg. Center; HPFTP FIRST STAGE IMPELLER 

AND PUMP BEARING FLOW ANALYSIS; LMSC-HREC TR D697954, Section 3. 

10. Marscher, W.D.; A PHENOMENOLOGICAL MODEL OF ABRADABLE WEAR IN HIGH 

PERFORMANCE TURBOMACHINERY; Wear, Vol. 59, 1980, pp. 191-211. 

11. Williams, D.N. and Wood, R.A.; INVESTIGATION OF THE REACTION OF 

5Al-2.5Sn TITANIUM WITH HYDROGEN AT SUBZERO TEMPERATURE; NASA 

CR-128496, May 15, 1972. 

12. Manson, S.S.; FATIGUE: A COMPLEX SUBJECT - SOME SIMPLE 

APPROXIMATIONS; Experimental Mechanics, 5(7), 1965, pp. 193-226. 

13. Dearnaley, G.; THE ION IMPLANTATION OF METALS AND ENGINEERING 

MATERIALS; Trans. Inst. Metal Finish, Vol. 56, 1978, pp. 25-31. 

14. Mozolic, J.A., Engineering Products Div., Union Carbide Corp.; Letter 

to F. Dolan, Creare R&D Inc., [INFORMATION ON UNION CARBIDE COATINGS 

LW-1n20 AND LW-15]; Sept. 8, 1982. 

6-1 
15. Kennedy, F.E. and Ling, F.F.; A THERMAL, THERMOELASTIC AND WEAR 

SIMULATION OF A HIGH ENERGY SLIDING CONTACT PROBLEM; J. Lubrication 

~ech., Trans. ASME, Vol. 96, 1974, pp. 457-508. 

16. Santini, J.J. and Kennedy, F.E.; AN EXPERIMENTAL INVESTIGATION OF 

SURFACE TEMPERATURES AND WEAR IN DISK BRAKES; ASLE Preprint No. 

74-LC-IB-3, ASME/ASLE Lubrication Conf., Oct. 1974. 

17. Dow, T.A. and Stockwell, R.D.; EXPERIMENTAL VERIFICATION OF 

THERMOELASTIC INSTABILITIES IN SLIDING CONTACT; ASME Paper No. 

76-Lub-21, ASME Joint Lubrica.tion Conf., Oct. 1976. 

18. Bill, R.C. and Ludwig, L.P.; WEAR OF SEAL MATERIALS USED IN AIRCRAFT 

PROPULSION SYSTEMS; Wear, Vol. 59, 1980, pp. 165-189. 

6-2 
This Page Intentionally Left Blank 
APPENDIX A 

THERMAL ANALYSIS OF SEAL RUBS AND RESULTS OF 

LOvJ SPEED AND SINGLE-PASS RUBBING TESTS 

by 

Francis E. Kennedy 

A-l 
APPENDIX A 

THERMAL ANALYSIS OF SEAL RUBS AND RESULTS OF 

LOW SPEED AND SINGLE-PASS RUBBING TESTS 

ABSTRACT 

This report describes the results of analysis and testing carried out 

at Thayer School of Engineering, Dartmouth College, in support of the 

effort at Creare R&D Inc. to evaluate the wear processes in labyrinth seals 

in the high pressure fuel pumps of the Space Shuttle main engines. 

A.1 THERMAL ANALYSIS OF SEAL RUBS 

An analysis was conducted of temperatures in the components of the 

labyrinth seal in the second stage impeller of the NASA space shuttle fuel 

pump. The analysis modeled the second finger of that labyrinth seal and 

used Dartmouth's THERMAP (Reference A-1) finite element thermal analysis 

program. The geometry for the model was based on engineering drawings of 

the seal provided by Creare. 

Two seal rub cases were studied: a 360° rub and a 30° rub (see 

Appendix B for discussion of contact angle). For both cases the rotor 

including knife edge was assumed to be made of titanium alloy with 5% 

aluminum and 2~% tin. Two shroud materials were investigated for each 

case, the baseline 2024-T4 aluminum alloy, and a possible substitute, 

nearly pure copper. Temperature-dependent thermal properties for each of 

the materials were obtained from Creare. 

Finite element meshes for the two cases were created and are shown in 

Figures A-1 and A-2. For the 360° rub case an axisymmetric model was 

chosen (Figure A-1). A modified two-dimensional model (Figure A-2) was 

used for the 30° case. Although the equations for that model were the 

two-dimensional heat conduction equations, the various elements were given 

thicknesses which depended on their location. If a cross-section of those 

elements could be shown, it would look like the cross-section in Figure 

A-I. 

Boundary conditions for the analyses were based on information given 

by Reference 9 and by Creare personnel. The inside diameter of the rotor 

and the outside diameter of the shroud (3.17 in. radius and 3.767 in. 

radius respectively) were assumed to be held constant at -400°F. It was 

assumed that all of the free surfaces - the free edges in the 360° model in 

Figure A-1 and all the element faces (areas) in the 30° model in Figure A-2 

- were transferring heat by convection to liquid hydrogen at -375°F. The 

convection coefficient was estimated, based on known fluid velocities and 

properties, to be approximately 0.004 BTU/in2 secoF. Since Creare personnel 

had determined a convection coefficient of 0.04 BTU/in2 sec of for the same 

surfaces, it was decided to try a variety of convection coefficients in 

order to investigate the influence of that parameter on the results. 

A-2 
Heat flux was 

contact interface. 

of frictional heat 

generation rate is: 

assumed to be input to the model uniformly along the 

The magnitude of the heat flux, and of the total rate 

generation, is not really known. The total heat 

where Ff is the friction force and 

V is the rub velocity 

(AI) 

It is known that V = 1135 feet per second at operating conditions. The 

friction foree, F

f can be estimated using the results of our room 

temperature, slow speed rub tests (see Section A.2). !~is would give, for 

the 360° rub case~372 lbf at an interaction rate of 10 in/sec and 720 lbf 

at the rate of 10_3 in/sec. These values are quite likely high, however, 

especially the 10 in/sec number. A quick analysis shows that if no 

material were removed at all during a 360° incursion, resulting in a shrink 

fit situation, the maximum friction force would be only 200 lbf with a 

friction coefficient of 0.2. The force should be lower if material has 

been removed by wear. Because of the uncertainty in this heat flux value, 

a range of heat flux values were investigated for the 360° rub case. 

It should be noted that the heat conduction equations are different in 

the two cases, 360° and 30°. In the 30° case, one of the bodies is moving 

in its plane relative to the source of heat. This requires a solution of 

the heat conduction equation including a convective diffusion term for that 

body. In the 360° case, both bodies can be considered stationary relative 

to the heat source, so that the convective diffusion term is zero. 

A.l.l Results for 360° ~ub Case 

For any heat flux at the contaet interface, the maximum temperature 

occurs in the middle of the contact surface. If the heat flux was constant 

throughout the rub (Le. a constant incursion rate yielding a constant wear 

rate yielding a constant friction force), the temperatures were found to 

reach their steady state value < 2 seconds after the beginning of a 30 

second rub. Thus, a transient analysis of the temperature distribution is 

unnecessary since the steady state analysis accurately predicts the maximum 

temperature values. 

The magnitude of the maximum surface temperature is approximately 

proportional to the heat flux as ean be seen in Table A-I. The range of 

heat flux values in Table A-I covers the range of friction forces which may 

occur in a rub. For example, a flux of 1,000 BTU/in2 corresponds to a 

friction force of 450 Ibf, while 125 BTU/in2 corresponds to 56 lbf. It can 

be seen from the results that some melting of the aluminum surface can be 

expected for most of these rub conditions. An aceurate analysis of surface 

temperature does require, however. a good knowledge of actual rub forces; a 

parameter which remains unknown. The influence of convection coefficient 

on the maximum surface temperature is shown in Table A-2. It can be seen 

that the better the convective cooling (higher h) the lower the surface 

temperature. There is a substantial difference between the temperature 

predictions at h = 0.004 and h = 0.04, the range of values of h determined 

for this configuration. 

A-3 
A.l.2 30° Rub Case 

Solutions for the 30 0 rub case were less satisfactory than those for 

the 360° case. Two problems were encountered: 

1. the rub velocity was so high, and the resulting Peclet number was 

so high, that numerical instabilities resulted in the solution of 

the finite element equations (convective diffusion). 

2. The number of nodes was large, necessitating large computer 

storage requirements, therefore. limiting the number of runs. 

The temperatures predicted for this case were approximately 55% higher 

than those predicted for the 360° case under similar conditions (same heat 

flux, same velocity, same boundary conditions). There is some question 

about the validity of that number, however, because of some numerical 

oscillations which appeared in all results for the 30° case due to the high 

Peclet number. 

A.I.3 Influence of Material 

Analysis of both 30° and 360° cases were done in which the shroud 

material was copper instead of aluminum. Properties of a nearly pure, 

wrought copper alloy were used in the analysis. Results of the analysis 

showed that the maximum surface temperatures with the copper shroud are 

approximately 60% less than those with the aluminum alloy shroud. This 60% 

value was true of both 360° and 30° cases, and is primarily due to the 50% 

or more difference in thermal conductivity between copper and aluminum 

2024. 

A.2 KNIFE EDGE RUB TESTS 

Tests were run on three specimens of 2024-T4 aluminum on a knife edge 

rub tester. Flat specimens, approximately 2.5 cm x 2.5 cm x 1 cm, were 

rubbed against the outer diameter of a thin rotating disk (knife edge) of 

6.25 inch diameter. Two different disk materials were used, 304 stainless 

steel and Ti-5Al-2.5Sn. All tests were run in air at a constant applied 

normal force of 5 Ib and a constant rotor speed. Measurements were made 

of friction force ana incursion during the tests, which had durations 

ranging from 10 to 60 seconds. The test configuration is shown in Figure 

A-3. 

Test results are given in Table A-3, for the stainless steel disk 

tests and in Table A-4 for tests with the titanium knife edge. It can be 

seen that !~e tests with the stainless steel rotor showed that an incursion 

rate of 10 sec required a friction force of about 1.5 Ibf • Friction 

forces with the titanium disk were slightly larger, while ~ncursion rates 

were slightly smaller. The friction force values with the titanium disk 

should be used with caution, however, since the force calibration for those 

tests may be in error. It was found that higher rub speeds resulted in 

slightly lower friction forces, probably because of frictional heating 

effects. Sparking was noted in all tests with the titanium rotor and in 

A-4 
longer and/or higher speed tests with the stainless steel rotor. Surface 

temperatures in those tests must have, therefore, been close to the melting 

temperatures of the materials. 

A.3 INCURSION RATE - RUB FORCE RELATION 

The rub tests (~tiuminum flat vs stainless steel rotor) showed that an 

incursion rate of 10 in/sec resulted in a friction force of about 1.5 

1bf • Use of the incursion-contact angle analysis program (see Appendix B) 

showed that the contact angle on these tests was approximately 5° at the 

end of a 30 second test_gnd that the wear rate of the aluminum was 

approximately 1.35 x 10 inS/sec. 

If it is assumed that wear rate is proportional to the friction force 

for this material combination (a valid assumption und~4 certain conditions 

for many materials); then for an incursion rate of GO in/sec, the 

friction force-to-wear rate ratio is about 1.1 x 10 lbf/ins/sec. A 360° 

rub in the NASA seal for this combination would have a wear rate of: 

.. -4 5 

V = 2nrwI = 2n(3.5)(0.03)(10 ) = 6.6 x 10- inS/sec (A2) 

This would require a rub force of about 72 1bf . A 30° rU~6at the same 

incursion rate would have a volume wear rate of 5.43 x 10 inS/sec (from 

the incursion rate-angle program) and this_~ou1d require a friction force 

of about 6 1bf (at an incursion rate of 10 in/sec). 

Following the s~~e line of reasoning, it would appear that an 

incursion rate of 10 in/sec (10 times the above value) would require wear 

rates of 10 times the above value in order to remove the required amount of 

material. This would result in friction force requirements 10 times larger 

than the above values for the same rub angle, assuming the rub 

force-to-wear rate relation remains valid. This assumption is probably 

faulty, however, since our rub tests show that different rub conditions 

seem to have different rub force requirements. Insufficient data are 

available to determine the influence of various rub parameters (velocity, 

incursion rate, materials) on the rub force-to-wear rate relationship. 

A.4 SINGLE PASS RUB TESTS 

A series of abradabi1ity tests was run on a pendulum type single pass 

test apparatus recently built in the Thayer School laboratory (Reference 

A-2). The apparatus has a hard triangular abrader (a carbide cutting tool 

insert) attached to the end of a swinging pendulum, with a specimen to be 

abraded being fixed to the stationary bed of the tester. A given incursion 

(or interference) is set between abrader and specimen before the pendulum 

is released. Energy lost during a single abrasion event is monitored and 

weight loss measurements are made to determine wear. The temperature of 

the test material can be varied over a range of -196°C (liquid nitrogen) to 

+500°C. This type of test had previously been shown to give a good measure 

of a material's abradability in tests of a wide variety of materials. For 

these tests, a constant incursion of 0.1 rom was set. Two different 

materials were tested, 2024 T4 aluminum, and a free machining copper (99.5% 

A-S 
copper, 0.5% tellurium). Tests were run on both materials at -196°C and 

21°C. Test results are shown in Table A-5. Each of the results is the 

average of 7 to 10 tests run at each condition during July 1982. 

Past work with the test device has shown that the specific energy 

(energy loss per unit mass of material removed) is a good measure of 

abradability. Here it can be seen that each material is more abradable at 

room temperature than at cryogenic temperatures. This is probably related 

to the increased resistance to plastic deformation at low temperatures. 

Thus, rub tests performed at room temperature (or higher) do not 

necessarily give an accurate prediction of rub behavior at cyrogenic 

temperatures. 

It can also be seen from the results in Table A-5 that the copper 

material is more abradable than the aluminum alloy at both room and 

cryogenic temperatures. This conclusion holds even when translating the 

specific energy values from energy per unit mass to energy per unit volume 

(using the densities of the two materials) • 

TABLE A-I INFLUENCE OF HEAT FLUX ON SURFACE TEMPERATURE FOR 360° CONTACT 

Heat Flux (1) T 

max 

(BTU/in2 -sec) (OF) Comments 

1000(2) 7923 T > T melt to 0.1 inch deep in aluminum 

500 3927 T > T melt to 0.04 inch deep in aluminum 

250 1993 T > T melt to 0.012 inch deep in aluminum 

125 981 T < T melt everywhere 

(1) Heat Flux = Contact Pressure x Rub Velocity 

(2) For 360 0 contact, 1000 BTU/in 2 -sec corresponds to a rub force of 452 

Ibf acting on an area of 0.66 in2 (Area = ~ x 7 inch x 0.03 inch) and 

at a rub velocity of 1135 ft/s. 

A-6 
TABLE A-2 INFLUENCE OF THERMAL CONVECTION C~HFICIENT ON 

SURFACE TEMPERATURE FOR 360 0 RUB 

Convection Coefficient 

4.0 

0.4 

0.04 

0.004 

o 

(l)Heat Flux = 500 BTU/in 2 -sec 

(2)properties of the rub materials above 

assumed to be the same as at slightly 

phase was considered. 

T 

max 

(2) 

2417 

2784 

3927 

7551 

l3829 

their melt temperatures were 

below T 1. No change of 

me t 

TABLE A-3 RESULTS OF IN 

VS ROTATING 

CURS ION TESTS - FLAT SPECIMEN 

STAINLESS STEEL KNIFE EDGE 

• 2024-T4 aluminum specimen 

• 304 stainless steel knife edge disk, 6.25 inch. diameter x 0.05 inch thick 

• 5 1bf normal load 

• Room temperature 

Test No. 

1 

2 

3 

4 

5 

6 

7 

8 

Duration 

(sec) 

10 

10 

60 

60 

30 

15 

15 

30 

Ro tationa1 

Speed 

(rpm) 

1000 

975 

1025 

:LOOO 

1850 

910 

900 

900 

Friction 

Force 

(lbf ) 

1.5 

1.2 

1. 5 to 1. 2 

1.25 

0.86 to 1. 2 

1.45 

1.6 

1. 0 to 1. 5 

Notes: At lower speed (900 to 1000 rpl n) , 

required a friction force of ~ 

an incursion rate of 

1.5 1bf" 

Incursion 

_4Rate 

(10 inch/sec) 

-

-

0.5 

0.375 to 0.875 

0.35 to 1.65 

1 

1.1 

0.4 

-4 10 inch/sec 

At higher speed (1850 rpm), an 

friction force of ~ 1 1bf • 

incursion rate of 10-4 inch/sec required a 

Sparking noticed after 25-30 s econds for tests 3, 4, 5. 

A-7 
TABLE A-4 RESULTS OF INCURSION TESTS - FLAT SPECIMEN 

VS ROTATING TITANIUM STEEL KNIFE EDGE 

• 2024-T4 aluminum specimen 

• Titanium sAl-2.s Sn knife edge disk, 6.25 inch diameter x 0.05 inch thick 

• 5 Ibf normal load 

• Room temperature 

Rotational Fricti~~b Incursion 

Test No. Duration Speed Force -4 Rate 

(sec) (rpm) (lbf ) (10 inch/sec) 

9 20 950 2.1 0.3 

10 30 950 1.7 to 2. 0.4 

11 30 950 2 0.6 

(1) Friction force may be in error due to questionable calibration. 

Notes: Sparking of titanium (typical white titanium sparks as in grinding) -- was noted in all tests. 

Rub forces appear to be slightly larger than with stainless steel. 

TABLE A-5 RESULTS OF SINGLE-PASS ABRASION TESTS OF COPPER AND ALUMINUM 

Test Average Average Average 

Material Temperature Energy Loss Wear Energy Loss/Wear 

CC) (N-m) (mgram) N-m (N-m) (gram) ems 

, 

Al 2024 -195°C 1.35 1.14 1190 3300 

Al 2024 21°C 1.77 3.35 530 1460 

Copper -195°C 2.24 16.3 137 1225 

Copper 2l°C 1.65 15.0 110 985 

Notes: All tests run at a rub velocity of 5 mise --

All tests run with incursion depth of 0.1 mm (0.004 inch). 

A-8 
3.767 II 

I RAD. 

t- 0.03" 

EN LA R G E 0 E L EM E NT 0 ETA I L S 

IN RU B ZON E 

Figure A-l. Fini te E~ement Mesh for 360 0 RUJ: 

Case (158 nodes; 152 elements; 

A-9 
3 ./7 RAD. 

Figure A-2. Finite Element Mesh for 30° Rub Case 

(651 nodes; 562 elements; modified 

2-dimensionall 

A-IO 
ItOTAT~NG _..-..J 

lNIFE EDGE 

6.25· 01 AM ET ER 

O.05 I1 THICK 

Figure A-3. 

~TION .+ 

ALUMINUM TEST 

SPECIMEN 

Ff (MEASURED) 

__ Low-Sp ee d . Knlfe Ed g e Test Setup 

A-ll 
REFERENCES 

A-l. Kennedy, F. E., Jr.; SURFACE TEMPERATURES IN SLIDING SYSTEMS - A 

FINITE ELEMENT ANALYSIS; ASME Journal of Lubrication Technology, 

Vol. 103 (1981), pp. 90-96. 

A-2. Santini, J. J. and Kennedy, F. E, Jr.; AN EXPERIMENTAL INVESTIGATION 

OF SURFACE TEMPERATURES AND WEAR IN DISK BRAKES; Lubrication 

Engineering, Vol. 31, 1975, pp. 402-417. 

A-12 
APPENDIX B 

INCURSION CONTACT ANGLE ANALYSIS 

B-1 
APPENDIX B 

INCURSION CONTACT ANGLE ANALYSIS 

INCURSION-CONTACT ANGLE ANALYSIS 

The incursion of a rotating labyrinth finger with the stationary wear 

ring results in loss of material from both of the seal elements. The 

extent and rate of this wear are of concern in the analysis of seal 

designs. For instance, the energy dissipation in the rub will be related 

to the total volume of material worn away and the relative volume loss 

(called the volume wear ratio, VWR) between the finger and the wear ring. 

Also, the area for heat removal in the wear ring is directly related to the 

length of the arc of contact between the labyrinth finger and the wear 

ring. Figure B-1 illustrates the geometry of the incursion, and defines 

nomenclature for the analysis of contact angle 6

1 , and VWR. 

The contact angle 6 was calculated for the labyrinth seal 

configuration in the HPFP for a case where all the material loss occurs in 

the wear ring (VWR = 0) and for a case where the wear is equally split 

between knife edge and wear ring (VWR = 1). Figure B-2 shows that the 

contact angle rapidly increases with incursion and for a rub depth of 0.25 

mm reaches a value of ~ 130°. 

c ~ R2 - R, = R AD I AL CLEARANCE 

WORN AREA -A" 

---

Figure B-1. Geometry and Nomenclature for Rub Interaction 

B-2 
Incursion: I d-c 

Worn Area: A = ~[R26 -R2 6 +£(b-a)] 1 1 2 2 

Worn Volume: V = Aw (w = thickness of knife edge) 

Wear Rate: 

dV dA 

dt w dt 

dV .;: [Ri-R,-dT 

dt 2wI R12- 2d 

(I interaction rate) 

-1 a Contact Angle: 61 = 2 cos (R) 

1 

2 cos-ll·R~-Rf-d2] 

. 2R

l

d 

Volume Wear Ratio: VWR 

VWR 

volume removed from knife 'edge 

volume removed from wear ring 

B-3 
160~----~----~----~----~----~ 

-

: 120 

Q) 

Len 

Q) 

-c 

-- CD 80 ,. 

VWR=O 

---

.,---

----- r-- ~ VWR=I 

KNIFE EDGE DIAMETER= 88.85mm 

RADIAL CLEARANCE =0.165 mm 

OL-____ ~ ____ ~ ____ ~ ____________ ~ 

o 0.05 0.10 0.15 0.20 0.25 

INCURSION DEPTH, I (mm) 

Figure B-2. Incursion Contact Angle 

B-4 
APPENDIX C 

CERTIFICATIONS AND SPECIFICATIONS FOR MATERIALS USED IN 

EXPERIMENTAL INVESTIGA~'IONS OF LABYRINTH SEAL WEAR 
APPENDIX C-l 

MATERIALS CERTIFICATION 

• Thermal Shock Specimens 

• BOM Knife Edge 

• BOM Wear Ring 

C-2 
~jI<ueUuHM.taJ4 e~ 0/ ,q,M/Uca 

CERTIFICATE OF TEST 

CHEMICAL ANALYSIS' 

HIlA THO. e: •• H AL YA c. Mo H z. SN MN 0 - . 

CS 14 .026 ,36 .010 4.85 .0065 2.4 .14 

CS 13 .023 .36 .014 4.93 .0107 2.3 .14 

YTTHIUM LESS 'HAN 1 PPM 

BALANCE 'TITAN UM 

===--

HIlAT HO. 

CS () 4 

CS 9 3 

TH •• I)ATK 

- - -. MECHANICAL. pnOPERTIES 

n.IT NO. .I%E 0" YIELD TENSILE ELONG. R. A. % HARDNESS BEND TEST GAUGE STRENGTH Sn'ENGTH 

,KSI KSI % BFTA TR1\Nf:l'~ 

ANNE f\LED 2 RS @ 15 OO°,F ACI 

CL 114 126 17 47 1855°F 

CL 120 130 18 41 .' 1835°F 

NOTC HEr> S'lRESS RU TURE OF 5 HRS ~ 150 P I 

MICI OSTRUC1TURE & ~!1ACROSTRUCTURE ~XAMINE 

IMMI RSION ULTRASOJICALLY IINSPECT,I D TO A 

sum ACE CONTAMINAJrON FR* 

AND }\CCE TJlBLF 

I I , 

May 7, 1982 

#2 FBB' 

RESULT. As A.OYE CERTIP'IED 

TITANIUM METALS CO,.,·ORATION 0" AMII!:"ICA 

o ,JUJ)ax-.. f.. fi&CMd 

Material certification for Titaniun Thermal 

Shock Specimens 

C-3 
Ti SAL-2.SSN Sheet to AMS 4910D & F~A S 4910-C 

E .0. #3359-3307 ~~M.t0J4 e~·o/,t/wwUca 

___ .. ~-:~!~~.' i c I ... M I A. 

CERTIFICATE OF TEST 

CHEMICAL ANALYSIS 

I VA c. I ,"0 

! 

I 

H 

52836 ! .0151 .30 I .019 I 5.4 I .010 

I ! 

I I 

I I 

I I Y'l'l'RILI-, 'LESS THAN 

! 

, 

! 

i 

BALANCE i'lITAN+uM 

, 

I 

I 

i I 

HEAT NO. I TEaT NO. 

52836 J0418 

1f PFM I , i i I I 

I 

I 

I 

MECH"NIC"L 

1 

PROPERTIES 

SIZE OR I YIELD TE"NSILE 

GAUGE J STRENGTH ' STRENGTH ELONG. 

i KS1 I KS1 

ANN~ALED 2 ~IN @ 

L I 131 ,'140 

T ',I 131 140 

L 129 

I 131 

I I 

139 

T 141 

, I 

i I I ; 

% , I 

1JOO O F Aci , I I . 

i 17 I 1 ~ _0 ! 

i 

19 i 

I 

16 I 

: 

i 

! 

CONTAMINATION FREE, 

! 

i 

I 

I 

R. A. !"o 

I~ 

j 

I 

I 

I 

I 

I 

I 

I 

I 

I 

i 

z • I SN MN 0 

! ! I 

12.4 .15 

i 

I I i 

! , 

i 

! 

I 

HARDNESS BEND TEST 

R/T @ 20X 

I 

I 

4.0 

I 4.0 

I 

I 

! 

! 

RESULTS As ABOVE CERTIFIED 

TH'. DAU __ 3--'/_2_6...;/'--S_2 ____ _ TITANIUM METALS CORPORATION 0' AM£~ICA 

Material Certification for Titanium 

Knife Edge Disk Specimens 

C-4 
."',;~ ::, 

2024T35l Aluminum Bar 

Copper 

"'.anganese 

Magnesium 

4.4 

0.6 

1.5 

Aluminum and Normal Impurities Constitute Remainder 

'i) 

; 

I;:.,,··· .) ;':l','"' 

Very truly yours i,'."· .) 

NORTHSTAR STEEL AND ALUMINUM, INC, /[' 

vrr- /1 fJ. . ,4 

ByL/1A?;t.d-aJ Ly. ~/ ~ ~1 . __ . __ .. __ !: ) 

Material Certification for Aluminum 

Wear Ring Specimens 

C--5 
APPENDIX C-2 

APPLICATION DATA FOR NITROGEN ION IMPLANTATION TREATMENT 

OF KNIFE EDGE DISK 

(Calculated density profiler7at 150 and 200 keV. Actual implant 

performed at 180 keV at dose of 2XIO ions/cm2 .) 

C-6 
12 o. 

~e -

Co> 

-

V) 

:z: 

~ 

8 NO 

:z: 

~ 

-...... 

<I: 

a::: 

...... 

:z: 4 

LU 

0 

:z: 

0 

0 

0 

(} 

16 

~e -

Co> 

en "" 

:z 12 0 

NO --

-:z: 

0 

...... 8 

<I: 

a::: 

...... 

:z 

LU 

c..:> 

::z 

0 4 c..:> 

0 

0 

I o .24 

DOSE (IONS/cm l )= 2.0x IO IT -:..:: 

RANGE (A) = 1710 ...J 

::;:) 

S TRAGGLI NG (A) = 57 I 0.20 c:a 

...... AVE.ATOMIC WEIGHT =47.9 :z 

ee 

DENSITY (G/ cm3). 4.54 ...... 

a... 

S.Y. (ATOMSIION)· 1.0 o .16 ~ 

- 200 keY 0 

!< o .0 8 a::: 

c..:> 

-::IE 

o .04 ~ 

I 0 

0.1 0.2 OJ 0.4 0.5 

I 

SPUTTER DOSE UONS/cm2 ). 2.0xI0 17 

SURFACE RANGHA) = 1343 

STRAGGlING(A) =521 

AVE. ATOMIC WEIG~T .. 47.9 

DENSITY(G/cm }"4.54 

S.Y.(ATOMS/ION)·1.0 

150 keY 

I 

0.08 0.16 0.24 0.32 

IlEPTH,(fL m) 

Figure C-l. Calculated Implant Profiles at Energy 

Levels of 150 and 200 keV 

C-7 

0.24 § 

:;::) 

c:c 

...... 

:z: 

<I: 

...... 

a... 

0.16 ~ 

0 

...... 

< 

a::: 

0.08 ~ 

0 

...... 

ee 

0 

0.40 
APPENDIX C-3 

TECHNICAL INFORMATION FOR ALUMINA COATING OF 

KNIFE EDGE DISK 

• Descriptive Literature - METCO 447 and lOlB-NS 

• Spray Parameters 

• Photomicrograph of Applied Coating 

C-8 
TECHNICAL BULLETIN , '\ 

Wkme &'ptatt-'&!aipmmt \." 0IJtd cY.upp&"t:6 .'.' MET COl NC. 1101 Prospect Avenue, Westbury,l.I., N.Y. 11590 . ... . ....... ~,J • .' ... 

METca 447 AND METCa 447NS 

SELF-BONDING MOLYBDENUM-NICKEL-ALUMINUM COMPOSITE POWDER 

SUPPLIES 

PO~IDER 

ISSUED: 1 Mar 82 

UPERSEDES: 1 Apr 81 

ILE: Section lb 

NOTE: METCO 447 and METCO 447NS are identical materials. For the sake of simplicity, 

this bulletin will refer only to METCO 447. The information it contains applies 

equally to METCO 447NS. 

Summary: METeO 447 is a Molybdenum-Nickel'-Aluminum composite powder. It was especially developed as a General Purpose material for producing medium 

hard coatings for hard bearing and wear resistance applications. This 

material offers two major advantages: "One-Step" spraying and HighIntegrity coatings. 

"One-Step" coatings offer these benefits: 

Eliminate the need for a separate bond coat. 

Less undercutting required. The allowance for bond 

coat thickness is eliminated. 

Less technique dependence. Reducing the number of 

steps required to produce the coating, also reduces 

the chance of err'or. 

More convenience. One-step coatings eliminate having 

to change materials and spraying parameters. 

METCO 447 was designed to produce moderately hard, low-shrink, high-strength 

coatings which are recommended for wear resistance, resistance to particle 

erosion, and for the salvage and build-·up of both machinable and grindab1e 

carbon steels. 

Coatings of METCO 447 are extremely tough, and exhibit good erosion resistance. They can withstand impact wi tllout cracking. Flaking and chipping 

are minimized. 

METeo 447 coatings can be ground to very fine finishes. Also, good machined 

finishes can be obtai!1ed with conditional technique. 

This revision includes 0 change in the argon/hydrogen plasma system parameter Set #4, which has been revised to ensure a more consistent, high 

deposition rate coating. 

SPECIFICATION CONFOR~ANCE: 

NF.TCO 447NS meets the AiResearch SpecificQtion FPS045, Type XVI, General Electric 

Company Specifi.ca·tion B50TF166, Avco Lycoming Division Specification M 3961, 

Perfect Circle Specification 110-265, and Rolls Royce Specification MSRR 9507/35. 

- Continued - 10-133 

C-9 
Page 2 METCO 447 AND METCO 447NS 

SELF-BONDING MOLYBDENUM-NICKEL-ALUMINUM COMPOSITE POWDERS 

FEATURES: 

METeo 447 can be sprayed with m1n1mum dependence on technique or need for temperature 

control. This allows for continuous spraying, and reduces chances of lamination 

occurring due to interruptions. 

Thick coatings can be applied without cracking. Thin coating~ can also be applied 

with minimum surface preparation requirements. 

The properties of the coatings produced with METCO 447 provide a number of additional 

benefits: 

High Bond Strength - Tensile bond strengths of 6,000 psi (4140 N/cm2) 

for ThermoSpray coatings, and 7,000 psi (4825 N/cm2) for Plasma 

Sprayed coatings are typical. 

Good Wear Resistance - Resistance to abrasive wear is better than 

coatings of METCO 450, METCOLOY 5 and combustion sprayed SPRASTEEL 80, 

and less than coatings of METCOLOY 2 and SPRABOND. 

Low Shrink - Coatings of unlimited thickness can be applied without 

cracking, which makes METCO 447 ideally suitable for machine element 

applications. 

High Interparticle Cohesion - Coatings exhibit excellent internal 

strength which provides high tensile strength over 15,000 psi 

(10,350 N/cm2), and good edge retention after machining. 

Toughness - Coatings exhibit high toughness and good erosion resistance. 

They can withstand impact without cracking. Flaking and chipping are 

minimized. 

Moderate Hardness - Coating macrohardness ranges from Rb75 to ~80, as 

compared with Rb65 for METCO 450 coatings. 

Good Finishil!9: Capability - Coatings can be ground to a very fine 

finish. Also, machining with conditional technique will produce 

good finishes. ME~rco 447 coatings are more machinable than coatings 

of METCO 450. Ground finishes are better than ground finishes of 

METCOLOY 2 or SPRABOND. 

Good Bond Coat Material - In addition to its capabilities as a single 

coat material, METCO 447 is equivalent to ~mTCO 450 as a bond coat 

material. 

METCO 447 can be sprayed with either the METCO Type 5P or 6P ThermoSpray Guns, and 

\'i'ith the METCO Plasma Flame Spray Systems. 

- Continued -

C-10 
TECHNICAL BULLETIN 

SUPPLIES 

POWDER 

ISSUED: 2 SEPT 77 

MET COl Nc.1l01 Prospect Avenue, Westbury, L.I., N.Y. 11590 SUPERSEDES: 30 APR 74 

FILE: Section lb 

METCD 101B-NS GREY ALUMINA POWDER 

Summary: METCO lOlB-NS is a grey alumina powder. It is identical in chemical 

composition to METCO lOlNS, but it is coarser and can be used in 

thicker coatings. 

Coa.ting PlOlB-lO is recommended as an abrasive coating for clearance 

control applications in jet engines. Considerable heat is generated 

in the first start of the engine after spraying. Coating PlOlB-lO 

resists heat to 2000 0 F (109S oC). It is used on the compressor casing. 

It will not scratch, chip or roughen the revolving titanium compressor 

bla.des, nor permit transfer of material between the mating surfaces. 

For further information, see the METCO Technical Bulletin on 

"Abradable and Abrasive coatings", and also 'Sections Fl and F2 of the 

ME1'CO Handbook of Coating Recommendations. 

********** 

This revision of the bulletin has been issued to add 7M System parameters. 

METeO lOlB-NS can be sprayed only with METCO Plasma Flame Spray Equipment. It 

cannot be sprayed with standard ThermoSpray Equipment. 

SPECIFICATION CONFORMANCE: 

METCO lOlB-NS meets the requirements of Pratt & Whitney Aircraft Corporation 

specification PWA 1311, and General Electric Company specification ASOTFS"'. 

APPLICATIONS: 

METeO lOlB-NS is being used in jet engines for producing abrasive machine element 

cleal:'ance control coatings. 

Use METCO lOlB-NS wherever a GE ASOTF87 or PWA 1311 material is required. 

ME'fCO lOlB-NS is recommf,nded for the following applications: 

Coating No. --.---

PIOlB-lO 

Coating Function 

Abrasive coating to 20000 F (109SoC) 

Jypical Application 

Jet Engine Compressor 

Casing' 

METCO lOlB-NS should also be considered and tested for applications on foundry 

equipment and the like, for thermal barriers, and for resistance to molten zinc, 

molten aluminum and molten copper. METCO lOlB-NS has been applied in coatings 

more thaP. .• 120" (3mm) thick with no evidence of spalling or laminating. 

- Cont.inued -

C-11 
Page 2 

P0I4DER CHARACTERISTICS: 

Typical Composition: 

Typical Size Range: 

Melting Point: 

TYPICAL PHYSICAL PROPERTIES OF THE COATING: 

Texture, as-sprayed (microinches aa): 

METCO lOlB-NS GREY ALUMINA POWDER 

Aluminum Oxide 

Titanium Dioxide 

Silicon Dioxide 

Iron (Ferric) Oxide 

Other Oxides 

-200 mesh +30 microns 

-75 +30 microns 

94.0% 

2.5% 

2.0% 

l.O% 

Balance 

Coating 

Pl01B-10 

700+ 

Finish, as-ground (diamond wheels) (microinches aa): 40-70 

Macrohardness: 

Cross Sectional Hardness: 

Density (glee): 

Weight (lh/ft2/.00l"l: 

(kg/m2/0.lmm): 

FINISHING: 

DPH300760 

3.3 

.017 

.33 

Coatings of METCO lOlB-NS can be ground to good-to-excellent finislles. Use the 

parameters listed in the METCO Flame Spray Handbook, Volume III, for grinding 

coatings of METCO 101 Alumina Powder. 

SAFETY MEASURES: 

Flame spraying is a completely safe process when performed in accordance with 

"METCO's Safety Measures". Familiarize yourself with local safety regulations 

before starting sprayi.ng operations. DO NOT operate your spraying equipment or 

use the spray material supplied before- you have thoroughly read the l1ETCO 

Instruction Manual. 

DISREGARDING THESE INSTRUCTIONS MAY BE DANGEROUS TO YOUR HEALTH. 

C-12 
W.O. ~f __ . ___ _ Sales Sample Report 

Field 

customer.. C (2,!:' P/r' C 

completed 

(;-V L- • 

Engineer ________ ~---

Appvd. for shipment ~-.2-~;,--v A-v-=-- ~b~~'~~~~)~~~------

GUN MAT'L. p, PORT ! wHeEL "1TRV NO_1 I RPM AIR CAP 

H/.:: H.(J 

7113 

I % '/'/7 P- '/ 6-11 ~ 

~:;t1"\ t leO 

l~-AB -ti:2.. 5/)0 \~'\!h!, GH 

-

£Eeparation and Spraying 

1. Coating th ickness 

PARAMETE~S 

CLICKS I SPRAY C 

v~~-\1! DIST 

AR 

FL 

RIll1 

OW 

)';'(,1 wr 6 37 

5]!: 7:- ,(I ]-( 7 

PRE.SSURE 

~( ,IZ--

/()() SO 

(00 s-cJ 

FLOW l''' , - /v:) /, 

'{( .. Zt:: 

2. Degrease _'Vu..;,:..-H~,-)o-.:;::, -->:!;;£::o;'-,I2.;;..::c...i,y:.:..,p::.:..,.:c,-'-'-,.:'_"""-_~_ ~r'I c.boc eywe. 

3. Mask___ Blast 5'1 {;I:I-r 

Max. 

-- SPRAY PSA VIBI?'\TD~ RATE 

-:; S Ii'< .... ) 

7'~ 

4. Preheat tempc ___ --=2:..;O::.-o ____ .Spraying tempc ______ Cooling _________ _ 

5. Sealed 

6. UndE~rcoat jV\e.T<..-u L-/Lt/ Thickness c? , 66 -3 -1: -d CJ I 

7. Finish . t---\.e."T c- 0 \0 \ l~- tV ,:, () CJ()'j ;t .CJCJ I Coat: Thickness 

8. Number of pieces completed 3 

9. Work Handling Equipt. ;1/~rJe 

10. Traverse speed RPl-1 No. passes 

SPRAY PARAMETERS FOR ALUMINA KNIFE EDGE COATING 

C-13 
METeO INC. PHOTO RECORD __ M.......:....f)~ __ DATE j(-I/- FeZSPEC. NO. :?;;-2?A MAG. 200 ~ 

ETCHANT _______ _ 

PROJECT NO. W?().J... 

SAMPLE DESCRIPTION __ _ 

/61 13 -I'( 5 

Micrograph of Alumina Coating Surface 

C-14 
APPENDIX C-4 

TECHNICAL INFORMATION FOR TUNGSTEN CARBIDE 

COATING OF KNIFE EDGE DISK 

• Union Carbide Letter and Specifications for LW-IS Coating 

C-lS 
UNION CARBIDE CORPORATION 441 SACKETT POINT ROAO. NORTH HAVEN. CT 06473 

Coatings Service 

LINDE DIVISION 

Creare 

P.O. Box 71 

Hanover, NH 03755 

Attention: Mr. Frank Dolan 

Gentlemen: 

TELEPHONE: (203) 288·3331 

September 8, 1982 

Enclosed is the information you requested on two Union Carbide 

Goatings: LW-lN40 and LW-15. Also enclosed is a quotation for applying 

these two coatings on your cryogenic pump disc. As we discussed, the 

as-coated thickness for either coating will be .008"/.010" per side to 

allow you to finish to .003"/.005" per side. Based on this finished 

thickness, we suggest you undercut the parts to the nominal .004" per 

side or .008" on the diameter. Because of the geometry of these parts, 

there is no effective way to mask the 11° bevel or either side of the 

knife edge. Full coating thickness will be present on these areas after 

processing. Any areas that are parallel to the coating flow will at 

most have smoke on them that can be easily cleaned by you when finishing 

these parts. 

As I indicated, the bond strength of these coatings is too high 

to be measured by ASTM method C633-69. However, special laboratory 

tests for these coatings estimates values in excess of 25,000 psi. Of 

the two coatings, LW-15 is the only one that has been used in a cryogenic 

pump application. The CTE of LW-1S at 139 0 R is 3.68 x 10-6 in/iniaC 

or 2.04 x 10-6 in/in/oF which is lower than the CTE of your base material. 

LW-lN40 is also recommended because we have had good experience with this 

coating on knife edge applications even though we have not had cryogenic 

experience with it. Because of the temperature excursions this part is 

going to experience, we strongly recommend that you test both coatings to 

determine if either one will work in your application. If after reviewing 

the technical data on both coatings you have additional questions, please 

call. 

JAM/cmc 

Enclosure 

Very truly yours, 

UNION CARBIDE CORPORATION 

Engineering Products Division 

~.~~ Field Representative 

C-16 
UCAR COATING: LW-15 

CUSTOMER SPECIFICATION: None 

TYPE: D-Gun, Tungsten Carbide + Cobolt-Chromium 

COMPOSITION: 86 WC-l0 Co - 4 Cr 

CROSS-SECTIONAL HARDNESS: 1000 minimum VPN300 

BOND-STRENGTH: .) 10,000 psi 

POROSiTY: l..5"{o Max .. 

IMXIMUM OPERATING TEMPERATURE:. Not Available 

MODULUS Of RUPTURE: Not Available 

MODULUS OF ELASTICITY: Not Available 

DENSITY: 14.0 gm/cm3 

COEFF. OF THERMAL.EXPANSION: 

ELECTRICAL RESISTIVITY: Not: Available 

Froduction UCAR Coating --.----------

Fhysical CharacteristicS 

SURFACE. ROUGHNESS: AS-COATED: 125-150 MU IN. RMS (RMS .= 1.1 AA) 

tAPPED: 1-10 MU IN •. RMS (Depending on part geometry). 

OTHER:. Nor Available 

EXTRA GRINOlNG STOCK REQUIRED:-.003"-.0Q4'" 

APPLICATIONS AND-MAIN fEATUr:tS:.: LW-T5appliccHons include: impe!lers andwaar rings 

forcenh"ifUgai pumpsr plunger.i"-and rads for reciprocating pumps and compressors, 

gates Clnd seal'S. foryalves used in the petroreum industry and foils for pcper-making machines. 

It is recommended for aprl ications in the chemical processing indlJstry where better corrosion 

resistance than the LW-l s"!ries inequired_ LW-15 has:htermediare weer resistance to LW-5 

and LW-T (best) In a labor~tory sane! abrasion test. 

Prelimincry teshi indicate that the modulus ofruptureond·modulos of elasticity are 

intelmediate to LVI-5 and lW-l, buraddil'ional tests are. required for confirmation. LW-1S 

nos been·llscd on wa~er blaster pump plungers opercting at 7500 psi and on ammonia com;:,ressors opera"Hng at 60CO psi. . 

G

e info;mo-tion prc~cntcd hcrein-j,; for gufcia-;:;-;:;c on y. Nothing stated or implied is 

to be token os 0 warranty regardinn .the use of our products Oi.prOCe$ses, nor as 

p~rmi~.:;ion eli a reco:nmendation to procti.:c ony pcten~ed rr;v~ntion. 

11/1/75 

Replaces page dated 1~/5/73 

C-17 

Page: 1.3.4-45 
lW-I5 (cont/d.) 

CORROSION RESISTANCE (Speedway Laboratory Data) 

Temp.. Corrosion Rate 

Environment 

50'% Sodium Hydroxide 

o . F* MiJ/year 

RT GAIN 

Rating** 

-1- .. It • ., 294 10 G 

5% Nitric Acid RT GAIN I 

" II· 213 10 G 

20% Hydrochloric: Acid RT 0.9 E n n' It· 22~ 22 U 

SOlo- Sui phuric Ac id RT ].8 E IL If I~' 215· 13 M 

Rdo:ttive CorrO$~on P.CSist:lOCC of D-Gu~1 Carbide Coatillgs 

CORROSrO!,1 RE$i$TANCE RATING"'" 

COM;>OSfTlON 50'% NoOH 5';'0 HI'103 i.e?;!' Ii Cl 

COATING- CARI.HDE (lINDER R.T. 294°F'" ---- 0 R. T. 226c R.T. 213F 'F 

LvV-ll'i30 we Co -1- -u- -1- -1-- -E-'"1t\ 

lW-1S WC Co-Cl:" I G: .( G E U 

LW-16· we Co-Cr E lJ I I E M 

LW-16N30' we Ca-C" E U r E- G U 

LI;V-5 (W,Cr}C Nt L G G G M U 

wr-t (W,.Tile Nt E' E. U U' U U' 

LC-1C Cr£Z Ni:..cr. r .. [. G U U' U 

"clevated: temperature t"s;S" ara at tt:e boiling point of the ,.;;rution~ 

'-R"ating- s'l'~CItr fur UCAR. ccctingot 

Excellent (1:):-:< 2: mH' penetra!ion/i.'eor 

Good(G)~ 

Mcrtlina[ (M); .> JU, ~20-

Unsatisfi::ctory (U): > 20. 

tnoetermmont- (I); ",elght'galn curi~g- corrosion· test 

The in-forr.:la.tiQn pn:sentea herein is for guidance ~~iy. 

Nothfng: st..ted or impiied is to he 100ken as a watr.lnty· 

reg:m:!ing the use- of our m-nctucts or processes, nor as 

. permission' Ot" a recommend .. tio:l to practice- <:.ny patented_ inventiol'r.. 

Nov .. !, 1975 

Replace.s page dated .~. bec~ 5 •. 1971. 

C-18 

s~;~ ;~ ... S() .. 1 

R. r::·JZ1SO'F 

t- ~ 

E M 

E G 

E G 

G U 

G U 

U U 

Pa>?e.: -1.3 .4-4SA 
APPENDIX C-5 

TECHNICAL INFORMATION FOR ALUMINUM/GRAPHITE 

COATING OF WEAR RING 

• Spray parameters for METCO CE-2074A 

• Photomicrograph of Applied Surface 

• Finishing Instructions 

C-19 
w.o.# __ ~ __ Sales Sample Report 

Field 

Completed'______ Engineer < 

customer_~C~T'...;e::;... :..:./J..;.rl::::.....:;.~~/_~...:;/.....::<...::.., _____ Appvd. for sh ipment ,&. F::::Oa '" d L.----

PARAMETE~S 

GUN MAT'L. P. PORT WHEf:L CLICKS I SPRAY CARRIEfi PRE:SSURE f:"LOW SPRAY MTflV NO:2 P5A VIe,£ATLlR RPM AMPS I DieT FLOW RATE AIR CAP VOLTSj ~ t·..;:' H 7,..- '71. 

ME Ito 

71-18 P'I Gil n~d sZ C; 37 ttlt' S'O - I/JU It) -. 2,- - '-' 

'1'17 6V"~ 

,"'l('1( tJ 

~tJ " 7M13 ,<3 .(-f"/ G~f/ t/ 1e7 4~\ .s/' 37 I()O 5t1 - 1ft! <0 - 9 - - E ;>~NH 

preparation and Spraying 

1. coating thickness ______ ~_,O __ 2_.~ ____ ~ ___ ·_O_o~z~ ______________________________ __ 

3. 

DegreaSe ____ V~,A~9~qr~c1~~~r.~~~~--1R~~,c~'~~~oc~eh~l~A~e~~~~~-------------------------------

Mask ____________ B1as t ___ S~Ly:....!G:iL:r'.Lr!c..J11-l_.L.J1,~~:_;..,2.~O:...;3r------ Max. 

2. 

4. Preheat temp. ___ .::2..;,.· ~ __ O---. ___ .spraying temp. ______ Cooling ________ _ 

5. Sealed -------------------------------------------------------- 6. Undercoat ....... e- ,GO W,4,,) Thickness o C)O~ or .()O ! 

. 7. Finish Coat I"'-Ei( (, (f ?() 7'( ~ Thickness o ,()20 t:.':;o I 

8. Number of pieces completed 3 

9. Work Handling Equipt. None 

10. Traverse speed RPM No. passes 

SPRAY PARAMETERS FOR ALUMINUM/GRAPHITE WEAR RING COATING 

C-20 
MI~TCO INC. PHOTO RECORD __ .... f11~[) __ . . DATE II-II~ l~ 

SPEC. NO. ~530 A MAG • .200 :;c 

ETCHANT ________________ . 

PROJECT NO. 

SAMPLE DESCRIPTION ____ _ 

Cr3- 2D71: A 

CICAflItITE:;.. "-' 21 -}6 "I.. 

(of20SITY= -v 6 - Y i/. 

Mi~rograph of Aluminum/Graphite Coating Surfac~ 

C-2l 
GENERAL HECOMMENDED FINISHING INSTRUCTIONS 

CE-2074A (Aluminum-Silicon-Graphite Composite) 

Procedure: Machine 

Tool: 5/16" carboloy AR5 Grade 78 

Set approximately .010" (0.25 mm ) above center 

Work Speed: 390 SFPM (120 m/min) 

Traverse Speed: .0025"/Rev (0.06 mm) 

Infeed: .010" (0.25 mm) 

Condition: Dry 

C-22 
APPENDIX C-6 

TECHNICAL INFORMATION FOR YTTRIA STABILIZED 

ZICONIA COATING OF WEAR RING 

• Spray Parameters for METCO CE-2l98A 

• Photomicrograph of Applied Coating 

• Finishing Instructions 

C-23 
w.O.4;\ ____ _ Sales Sampl~ Report 

customer Cl<.e"o/!·( 

Field 

Completed_______ Engineer 8Ji.L /lV5GiI 

!./v ( APpvd. for sh ipment J L~:.AA-Jl. __ 

PARAlv1 ETE P-.S 

MAT'L. P. PORT ! WHE.f:L CLICKS I SPRAY CARR1E~ PRE:SSURE ~LOW SPRAY GUN MTRV PSA YI e.1:A.TCR NO:2 I RPM AMPS I DIST FLOW RATE AIR CAP VOLTSi ii!,f H.., A 11, 

7M Mf..Tc-o 11 15 5"00 5 '/ /f)() 10 1?:' .--- - - G ~ 37 S"o 50 '1'17 21'1' i ~.; 701- !:til lit-. 

1ft{ A/~1VV if. 113'0 400 (;,5 " 37 50 75" lS- I))!: - - 1.-rf".A 'Iff G- n 56 fir, -

Preparation and spraying 

1. coating thickness ----------------------------------------------------------- . 0 3 6 ~ .:i: .0 oS ~ 

3. J.1ask S7t£L. .~:::' TIIIC,/( Blast C - 16 S 6-0 j's..Z'G- _ Max. q 

4. Preheat temp. __ 1 Z 0 ~_spraying temp. 3 Z. 0 F cooling ________ _ 

5. Sealed ____________________________________________________________________ _ 

6. Undercoat £,;; lev 4 if 7 . :::'+,002" Thickness .003 -.000" ----------------~~=~~-----

7. F in ish coa't ;1/£1(;0 Ci 21 78 A ... + ,Q/a:' Thickness ______ ._C/~L~O ____ --_4,~O~C~,~('_~ ______ __ 

8. Number of pieces completed ____ ~-3=_ _________________________________________ ___ 

9. Work Handling Equipt. _____ ~~O~IJV~~~ _____________________________________________ __ 

10. Traverse speed ____ ~ __ L_O_·_nl __________ RPM~ ____________ No. passes ___________ __ 

SPRAY PARAMETERS FORYSZ WEAR RING COATING 
l\llETCO INC. PHOTO RECORD __ ..,I;f11--,-,P,,-_ DATE II-It £2 

SPEC. NO. ~>J.I A MAG. oZOQ.)( 

l~TCHANT ______ _ 

PROJECT NO. tV 70.z.. 

SAMPLE DESCRIPTION __ _ 

@ CG- :211 f AMicrograph of YSZ Coating Surface 

C-25 
GENERAL RECOMMENDED FINISHING INSTRUCTIONS 

CE-2l98A (6-8 wt. % yttria stabilized Zirconia Powder) 

Procedure: Grind 

Wheel: Silicon carbide wheel (GC 100-Gll VGE or 

similar type wheel) or Diamond Wheel D120-

NlOO-87 or similar type wheel. 

Wheel Speed: 5500 - 6500 SFPM (1700 - 2000 m/min) 

Infeed: .002" (.050 mm) rough cut 

.0005" (.0l3 rom) finish cut 

Work Speed: Cylindrical - 70 - 100 SFPM(20-30 m/min) 

Flat -30-50 SFPM (8-15 m/min) 

Cross Feed: Flat - .030" per pass (.75 rom) rough cut 

.010" per pass (.25 rom) finish cut 

Traverse Speed*: Cylindrical - l2"/min (305 rom/min) rough cut 

6"/min (150 rom/min) finish cut 

*Amount of wheel width advance per revolution of work 

Roughing = 1/4" - 1/2" (6-13 mm) 

Finishing =1/2" - 1/6" (2-4 rom) 

C-26 
APPENDIX D 

STRIP CHART RECORDS FROM RUB INTERACTION TESTS 

D-l 
APPENDIX D 

Strip Chart Records from Rub Interaction Tests 

This appendix contains the computer plotted strip chart records from 

the 15 rub interaction tests. Each set of data displays the temperatures 

on one page and the 5 high response rate instruments on a second page. The 

data are plotted vs. time into the test, as in the sample data discussed in 

section 4.6.2. 

The thermocouple amplifier gains and offsets were adjusted several 

times during the course of the experimental phase in order to increase the 

temperature measuring range and still maintain adequate measurement 

sensitivity. Table D-l provides a listing of the pre-rub wear pad 

temperatures and the peak temperatures indicated by each thermocouple 

during each incursion test. Other intermediate temperatures can be 

calculated using the tabulated amplifier gains and a table of thermocouple 

emf values for the Type K thermocouples used in the wear pads. 

D-2 
TABLE D-l WEAR PAD TEMPERATURE DATA 

Test Name 

TIAL02 

T1AL03 

T1ALl3 

T1AL23 

T1AL04 

T1CU03 

T1AG02 

T1AG03 

T1YZ03 

TNAL02 

TNAL03 

AOAL02 

AOAL03 

TCAL02 

TCAL03 

Near-Surface Therm o 

Pre-Rub 

Temp. 

(OC) 

-151 

-111 

-179 

-187 

-190 

-103 

-175 

-158 

- 99 

-167 

- 82 

-186 

-124 

-l34 

-124 

Maximum 

Temp. 

(OC) 

314 

72 

560(1) 

265 

87 

274 (1) 

- 29 

-146 

126(1) 

313 

267 

234 

197 

317 

182 

Am 

(v o 

4 

4 

2 

2 

2 

4 

4 

4 

4 

4 

4 

2 

4 

2 

4 

couple SubSurface Thermocouple 

plifier Pre-Rub Maximum Amplifier 

Gain Temp. Temp. Gain 

Its/volt) ( °C) ( °C) (volts/volt) 

83.7 -147 213 479.4 

80.0 -·115 182 480.0 

40.4 -·176 437 240.4 

41.5 -·187 283 239.6 

40.3 -·187 82 239.1 

81.5 -·103 269 482.2 

83.7 -·176 - 79 479.6 

83.0 -·155 -151 480.0 

84.4 _. 98 23 479.8 

83.7 -·173 123 478.7 

84.4 _. 82 197 479.6 

40.2 -·184 119 240.0 

83.9 -·125 212 478.9 

39.8 -·132 134 239.8 

83.3 --124 181 478.9 

(l)These temperatures correspond to the m aximum full-scale voltage (5V) input to the 

computer. Wear pad temperatures were 

be determined from the data. 

actually higher, but the peak values cannot 

D-3 
t:1 

I 

"'" 

147° 0 

NEAR·SURFA:CE TEMPERATURE 

6.4 

RUB Test TIRL02 

7.2 7.4 7.6 

TIME (sac.) 

Reduction Dote: 38-AUG-B4 

Teat oota: 22-FEB-B3 

8.4 9.2 
o 

I 

\J1 

0. 5 SEAL S:PECIMEN DISPLACEMENT (mm ) 

0.0 L 

_ 1\ c: 

V.V 

0.2 r-DISK RADIAL DISPLAC:EMENT(mm) 

0.0 L ..... . 

/ I ~~~==t=~~=====Im . 

-0.2~c--~--__ ~ __ ~ __ ~ __ ~ __ ~ ____ ~_-~ __ ~ __ ~ __ ~ ____ ~ __ ~ __ ~ 

30§J DISK ROT A TI ON AL S P£ED I~ .... ... I 

(krpm) 

0~1 ~ __ ~~~~ __ ~~_~ __ ~~~~ __ ~~ 

~:: ~NO_RMtF~~~~MW~~*'!~~\~'~ 

0.0 I .. 

0.4 1 TANGENTIAL ifORCE kN) 

0.2 I ""'!"!+!~~W~ij~~~~4~' 

0.0 I 

6.4 6.6 6.8 7.0 7.2 7.4 7.6 7.8 8.0 8.2 8.4 8.6 8.8 9.0 9.2 

RUB Test TIRL02 

TIME (ssc.) 

Reduction Dote: 30-RUG-84 

Tast Dote: 22-FEB-B3 
t:J 

I 

0'1 

SUBSURFACE TEMPERATURE 

NEAR-SURFACEfEMPERATURE; 

10 

RUB Test: TIAL03 

14 

TIME (sec.) 

R8duc~ion DQ~8: 38-RUG-84 T8a~ DQ~8: 21-DCT-82 

22 
CI 

I 

-.J 

0.5 fEU SPECIMEN DISPLAfEMENT mm) I 

0.0[- .• ~ 

- 0.5 I • I 

o . 2 ....... D-IS-K-R-A D-~-A L-D"""'-]S-PL-A-C E=-M-'-E-N T--=-(-m-m )

o .0 . , j "i JI "' I II' " 16 I • .; ; . bil nt. 

-0.2~r ____ ~ __ ~ ____ ~ ____ ~ __ ~ ____ ~ ____ ~ __ ~ ____ ~ __ ~ ________ ~ 

30 I .. I I 5 '~SK RO rATI ~ N~iL S~EED[ ( krp~) 

o I . . . . I 

o .4,NORNAL FO.RC~ ~~rarl~ " .... 1[(JilIit~~i i 1 . I 

o. 0 r·mmmm:. ..........mmmj ............. m.]YQMMPliU.mU . . ............. ····~ .. 1'~.I.~bLlI , · ' I' , " 

-

0.4 

0.4 k-! 

FTANGENTIAL FORCE (kN) 

0.0 1 " ", 

-O.4r I 

1Il .11 12 13 14 15 16 17 18 19 210 21 22 

RUB Test :TIAL03 

TIME (sec.) 

Reduction Dote: 30-RUG-B4 

Teat Dote: 21-DCT-B2 
t:1 

I 

OJ 

NEAR -S URFACE TEMPERAT URE 

15.0 

RUB Test TIRL13 

(o9C. ) 

Reduction Dota: 39-RUG-84 

Teat Dote: 24-FEB-B3 

45.0 50.0 
t:J 

I 

\D 

0.2 rDlSK RADIAL DISPLACEMENT tmm) 

0.0 

-I.Sc~ ____ ~ __ ~ __ ~ ____ ~ __ ~ ____ ~ ________ ~ __ ~ __ ~ ____ ~ __ ~ ____ ~ __ ~ 

0.4 FTANGE:NTlAl FORCE (lkN) ! t : 'F« t: ~ Era. I .! + t I 

0.01. . 

-0.4, I 

15.0 17.5 20.10 22.5 25.0 27.5 30.0 32.5 :15.0 37.S 40.0 4E.5 45.0 47.5 50.0 

RUB Test :TIALi3 

TIME (ssfe.) 

R.duct i on !lot.." 3I!l-AtJG-'B4 Teat Dote= 2>4-F£B~B3 
t1 

I 

I-' 

o 

NEAR-SURFACE TEMP£RATU R;E 

20 

RUB Test TIRL23 Heduction Dote: 30-AUG-84 

Test Dote: 2S-FE8-83 

28 29 30 32 
t:J 

I 

r 

r 

0.5 rsm. SPEC I NEN DISPLACEMENT (mm ) 

0.0 I .. . ...... . 

-O.5LI __ ~ ____ ~ __ ~ ____ ~ __ ~ __ ~ __ __ I 

I 

0.2 rDISK RADIAL DilSPLACEMENT (rom) 

-:::t, , "" ,,,.. · ' -1 

3~ iO'Sk 'RQTATIONAL SPE~O (krpm) I 

I 

o 

~ 

I 

I ' , ., 

I 

0.8 

~-I 

0.0 ~ __ ~ ____ ~ __ ~ ____ ~ __ ~ ____ ~ __ ~ __ ~ ____ ~ __ ~ ____ ~ __ ~ 

0.4 FTANGENTIAL FORCE (kN ) 

0.2 [ 0.0 [ )~.. .''#1'''' 'Ijr·~~JiU!A\4\li.WIV'_'lliiiW~dtlh~IM J 

20 22 23 24 25 ~, 

RUB Test TIRL23 

TIME (sec.) 

R.duct i an !lot... 3f/j-RUG-'B4 

'Test DoTa~ 25-FEB-S3 
tJ 

I 

f-' 

N 

SUBSURFACE TEMPERATURE 

NEAR - SURFACE TEMPERATURE 

190 22:0 

TIME (sec.) 

RUB Test TIRL04 Reduction Dota: 30-RUG-B4 T.~t Dota: 01-MAR-B3 

330 
tJ 

J 

f-' 

W 

0.5

1 

SEAL SPECINfN DISPLACEMENT (mill) fl 0,0 I . 

-0.5 I .. I I 

0.2 rOISK RADIAL DISPLACEMENT (mm) 

0.0 

-0.2~r--~--~~~--~--~----~-----~--~--~------------~~ 

30 I· · , . 

15 . DISK. R.OTATIO~ALSPEED (k r~ m) . . •... 

I . 

ol~ ~ __ ~~ ____ ~ __ ~ __ _ i 

I 

0.4 ~ TANGENTIALlFORCE kN) 

0.2 I I 1 I r h : .• 11 b'p 1'*:.1--" I "111I~ . . . •• h71 ": •• .......,. rill I Of 

0,0 .. , 1'90 200 21 ~ 220 230 240 25~ 21\0 270 280 290 3;)0 310 320 330 

RUB Test TIRL04 

TIME (S9C.) 

R.ductlan Dote: 31-RUG-B4 

Test Dote: 01-HRR-B3 
t:1 

I 

f-' 

"'" 

SUBSURFACE TEMPERATURE 

.---- -103°C 

NEAR-5URFAC E TEMPERATURE . . 

r---~---;;;;;;;;':::'---..;.... -103 0 C 

10 II 

RUB Test 

12 

TICU03 

14 

TIME (sec.) 

Reduction Dote: 30-RUG-B4 

T.st Dota: 83-FfB-B3 

20 21 22 
U 

I 

r 

lJl 

G.5, SEAL SPECIIIE~ DISPliACENE~T (mm)' . Y1....... 

0.0 I • I - 0.51 . 

0.2 rDISK RADIAL 0 SPLACEMENT (mm) 

0.0 

-0.2e. __ ~ ____ ~ __ ~ __ ~ __ ~ ____ ~ __ ~ __ ~ __ ~ __ ~ __ ~ __ ~ 

::IDISK ROTATIONAlSPEED(~ .~, d 

O.O~I __ ~ ____ ~ __ ~ ____ ~ __ ~ __ ~ ____ ~ __ ~ __ ~ __ ~ ____ ~ __ ~ 

0.4 

D.2[ ' •. , .. , .. _' ,.....,."...~ .... n iQ J¢#ilU 

O.O[ ... . 10 "~ 

RUB Test TICU03 

TIME (sec.) 

Raduct;on Dote: 30-RUG-B4 Tast Dote: 03-FEB-83 
t:1 

I 

i-' 

(J\ 

SUBSURFACE TEMPERATURE 

-17 

I 

6.4 

RUB Test 

SURFACE TEMPERATURE 

TIRG02 

TIME (sec.) 

Red~c~ion Do~e: 3e-RUG-S4 T&s~ DO~8: 22-F£S-S3 

B.2 B.4 8.6 

-291' C 

L 

B.B 9.0 
t1 

I 

t--' 

-...J 

0.5 SEAL SPECIMEN DISPLACEMENT (mm) 

O. 0 cl·······-==~==-:--:--=~~~~.-L /i l ------~···-----'n . -il !=i, _--'. ___ ~ ___ --'. ___ ----'. ___ ----" ___ ---' ~. v L! ________ ~ ________ ~ ________ ~~ __________________ ~ ________ ~ ________ ~ ____ __ 

0.2rDISK R~DIAL DISPLACEMENT <:mm) 

0.0 

-0.2~~ __ ~ __ ~ __ ~ ____ ~ __ ~ __ ~ __ ~ ___ ~ __ ~ __ ~ __ ~ ______ ~ 

30 DISK ROTATIONAL SPEED 

! 5 I . 

o I'--------'-_~~ 08 F- -',--- -,'.---'- -'.--- -I '-'--'-"1- I N/: fIiI ... Iif

U 

i/i""~1II jjIIr 4IiI""'. t/fjli.' iliul"~"""""'III;"I1Il\."I"lIiwi '''''~IiW\WI''~ . I NOR N AL fO R C E (k N) : \ Ii '"i! ", ii, .. ,.. I, ! I iii • "". ' 

0.4 F 

I 

I 

0.-0 IL------.,;_--'-_-----'-_------'-_-----'-_-----'-_-----'-__ --'-_--'-_--'-_-'-__ ----' 

0.2 ' 

0.1 ,', ol, ~~~~~~~~~~ 

RUB Test TIRG02 

TIME (sec.) 

Reduction Dota: 3e-RUG-84 

Tast Dote: 22-FEB-B3 
tJ 

I 

I-' 

(Xl 

SUBSURFACE TEMPERATURE 

NEAR ... SURFACE TEMPERATURE 

7 8 11 

TIME (sec.) 

RUB Test TIRG03 ~aduction Dota, 30-AUG-84 

Test Dota, 10-FE8-83 

- 146 0 C 

I 

18 19 
t:J 

I 

f-' 

'.0 

0.51 mL1PECIN~N DISPLACENENT<mm) I I 

0.0 I' ') 1 

-O.SLI __ -L __ ~ __ ~ ____ L-__ L-__ L-__ ~ ___ ~ __ ~ __ ~~ __ ~~ 

0.2 DlSK RADIAL DISPLACEMENT (mm) 

0.0 , ! i • l 

-0.2~ __ L-__ ~ __ ~ __ ~ __ ~ __ ~ ____ ~~ __ ~ __ ~ ____ ~~ 

:: I DISK ROTAT'OrLSPITO(krpr lH I • v I • . . ; I 

o I ' , . , I 

:'.: fNORN1LFORCE(kNil . ., I 

0.0 I . 

o . 41 TAN G EN TI A L fO R CE ( k N 1 

0.2 

0.0 r--t ..---..........----· ........ , ---------..~---- J 

7 8 10 12 13 14 15 16 17 18 19 

RUB Test TIRG03 

TIME (sec.) 

Reduction Dote: 30-RUG-84 

Test Dote: 10-FEB-83 
tJ 

I 

tv 

o 

SUBSURFACE TEMPERATURE 

N EA R _is U R FACE-TEMPERA T U R E 

--. - 9S':C 

8 11 12 

TIME (sec.) 

RUB Test TIYZ03 Reduction Dote: 30-AUG-B4 Te~t Dote: 11-FEB-B3 

20 
t1 

I 

tv 

f-' 

O,SISEAL SPECIMEN DISPLACEMENT(mm) 

0.0 r ..- - O.5~1 __ ~ ____ ~ __ ~ ____ ~ __ ~ __ ~ ____ ~ __ ~ __ ~ __ ~ ____ ~ __ ~ 

2.0 FriISK RADIAL DISPLACEMENT (mm) 

0.0 __ [:! I ;; : : s .n : IF nimH_ttl III - 11 d r. 

- 2 0 ; 

3'~ IDISK BpTATIONiAL SPEFD (krpm ) _ . .... . ....... . ....•. .1 1:[- : ..... _m ••• ~ I 

1.2 ~NORM.ATrORC£ mIT --~: - - : ~-- ---- - -- -- -~--~- -I 

0.8 -.i'.'_~"'''''' , •. """, ... ~" .......... ~!!'-.llli'" H .... ' , .... 11 1 "..:----

n JI : - : ; : : 

u.~ [- - - - - I 

0.4 rTANGENTIAl fORCE (~N 1 

0.2 

0.0 ! I 

B 9 10 11 12 13 14 15 16 17 18 19 20 

RUB Test TIYZ03 

TIME (sec.) 

Reduction Dote: 30-RUG-B4 

Test Dote: 11-FEB-B3 
t) 

I 

tv 

tv 

SUBSURFACE TEMPERATURE 

NEAR-SURFACE TEMPERATURE ' 

9.6 9.8 

RUB Test 

/ -J - 167° C 

10.0 10.2 10.4 

TNRL02 

TIME (sec.) 

Reduction Dota: 31-RUG-84 

Tast Dota: 23-FEB-B3 

,/ 

'" t23°C 

II. 2 12.0 12.2 12.4 
t:J 

I 

N 

W 

O.S/SEAL SPECIMEN;OISpLACENENT (mm) - -c I I 

~.~ t ) . -O.jl~ __ ~~ __ ~ __ ~ __ ~ __ ~ __ ~ __ ~ __ ~ __ ~ __ ~ __ ~ __ ~ __ ~ 

0.2 rOISK RADIAL O[SPLACEMENT ( 

0.0 

-O.2cc __ ~ ____ ~ __ ~ __ ~ ____ ~ __ ~ ____ ~ __ ~ __ ~ ____ ~ __ ~ __ ~ ____ ~ __ ~ 

3 ~ I DISK RiTiONAL SPEED Ik'@m'l 

I ~ I . , . , I 

o I I 

1.2 NORMAL FORCE (kN). iii . : : I 

0.8 . . . '~~~~~j~~J"'l.~~~l;;;.I'I4~";"'~I.Mi~.I\ .. J' .m 

0.4 I O.OL---~ __ ~ ____ ~ __ ~ ____ ~ __ ~ ____ ~ __ ~ __ ~ ____ ~ __ ~ ____ ~ __ ~ __ ~ 

0.2 1_ ••• __ ..... ----- •• " .• 

0.1 

O.O·~~~'·I;H~. 9.6 9.8 10.0 10.2 10.4 10.6 10.8 11.0 ~~~~~~~j~~ 11.2 11.4 11.6 11-8 12 . .0 •• ~ 12.2 

RUB Test TNRL02 Reduction Dote: 38-RUG-84 

Test Dota: 23-FfS-83 
t:I 

I 

tv 

..,. 

13 

SUBSU RFACE TEMPERAT URE 

NEAR~SURFACE TEMPERATUR.E 

-i 82-oC 

14 15 18 19 

TII'tE {sec.) 

RUB Test TNRL03 Qeduction Oct.: 38-AU&-84 

Test Dote: B4-FEB-83 

20 23 27 28 29 
0.5 rsE1L SPEC U~EN- D! SPLACENENT (mm ) , 

0.0 I . I -o.51~ __ ~ __ ~ __ ~ __ ~ __ ~ ____ ~ __ ~~ __ ~ __ ~ ____ ~ __ ~ __ ~ __ ~ __ ~ __ ~ 0.2 

0.0 

_ 0.2 ~ [ i 111-lIIE I d II Iltll.'I,' us 11111 1111111 III r ' III 1.IIIUIt •• , alum tUM 11 • 11111 [ ; 

30 i . ' : 

H I nl~K RO:TATIO~AI ~p~pn (Iunm \ T i .." \i " I ; •• , •• •• r ,~ \.i. ~ ~.,. " n I r' 'r' , ~ ~ 

~ I: r'T'r!": ......... . 

0.8 

0.4 

a'OLI ____ ~ __ ~ ____ ~ __ ~ ____ ~ ____ ~ __ ~ __ ~ ________ ~~ __ ~ ____ ~ __ ~ ____ ~ ____ ~ __ _ 

O.2tTANGENTIAL FORCE (kH) . : · . • · 0.1 ~,-".,,"., • '" t'_ ,l""" .. " IH "'w" .w" ... ~ m"'" W.O ". ,. ''',' .... , T'" ' ... " u .... " 0' "" '" "" ".. ,'--", ,'", 

o .0L 13 1:-----:-':--~-___:_'_:_-__:_':::_-___:_'::_-____:_'::_-~- 14 15 1 IS a7 1 8 1 9 211 -::'7----:::'::---:::";;---::-:---;:';:---::'7----;:';:---~____;: 21 22 23 24 25 26 27 28 

RUB Test : TNRl03 

TIME (sac.) 

JledUC"t I on IlooT a: 3I1HWG-84 

'eaT IlooT9= &4-FEB-83 

I 
tJ 

I 

10 

(J\ 

SUBSURFACE TEMPERATURE 

NEAR -SURFAce TEMPERATURE 

8.8 9.0 9.2 9.4 9.8 

TIME (sec.) 

RUB Test RORL02 Reduction Dote: 30-RUG-B4 Test Dote: 23-FEB-B3 

11.6 
o 

I 

N 

-J 

o.s I SEAL S PECINE ~ 0 ISPL~CE ME N T (m m ) I 

00 I ) 

-O.S LI ____ ~ ____________ ~ __________ ~ ____________ ~ ____ ~ ____ ~ ____ ~ ____ ~~ ____ ~ __________ ~ 

o .2 r DIS K R A D I A L DIS P LAC EM EN T (11\ m ) 

0.0 

_ 0 . 2 rl'UIli~jll!!ftlli\\I1IIIIIIIII'1'\1!4. )1\1M~_!IIMIII\"'IloIiiI\nl~IIiI!I!~'IIM!II!i4I.III"'J~~~\~I!i~.'i'"\""U~~~,~. l\¥Ii,. ; II' "!"'I~ "" I,.,.., _-'--____ ~ ____ --'-____ ~'---____ -'-____ -'-____ ~ 

30 I . . " : I ~ .. DI~~mRO!~~IONA~SP~~Pm( kr~~:) I V I . . . . 

ol~ __ ~ __ ~~ __ ~ ___________ ~~ __ ~ __ ~ __ ~~~~ __ ~ 

0.2~TANGENTIAL FORCE(kN) 

0.1 

o.o,.......r ....... '''·'....... '''j.....,,·''jj~~''~w+~~-~~ I 

8.8 9.0 9.2 9.4 9.6 9.8 10.0 10.2 10.4 10.6 10.8 11.0 11.2 11.4 11.6 

RUB Test RORL02 

TIME (sec.) 

Reduction Dote: 3a-RUG-84 

Test Dote: 23-FEB-83 
o 

I 

tv 

CO 

SUBSURFACE TEMPERATURE 

1---~~-12S0C 

SURFACE TEMPERATURE 

1fl 11 

RUB Test 

12 

RORL03 

TIME (sec.) 

Reduction Dote: 30-RUG-84 

TesT Dote: 14-FEB-83 

17 21 24 25 
0.5 ISEAl SPECIMEN DISPLACENE,NT (mIlI)/ I 

_: ::1 L_-----'-· __ .i-· _----'. __ -'--_-'--_-----'-__ -'--_ .) .... .....m ... 

0.2 FmSK RADIAL DISPLACEMENT (mm) 

0.0' 

-O.2~t----~--~----~ __ ~ ____ ~ __ ~ ____ ~ __ ~ __ ~ ____ ~ __ ~ ____ ~ __ ~ ____ ~ __ ~ 

~ ~ ~: 0 I IDISK R~TATIO~Al . . SP~ED . (kr~m . )·1 

I 

~.:! t NO~_NUA.~t;;lE.It~~ ~N) ! ............... mmi .. ,~ .. ~~ldlj~.i~~!:J!t •• W,~~ ~r;il . . II 'lWJllr1 I" t.. . ,I •• .,11 ..... ml 

0.4 ~ , , . 0.0 I : . , 

0.4 t=TANGENTIAU FORCE [kN) I 

0.2 I 

0.0 1 ! 

III 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 

RU8 Test AORL03 

TIME (sec.) 

Reduction Dota: 38-RUG-B4 

Test Dota: 14-fEB-B3 
t:J 

I 

W 

o 

SUBSURFACE TEMPERATURE 

NEA R ... SURFACI TEMPERATURE 

8.4 

TIME (sac.) 

RUB Test TCRL02 R.duction Dote: 30-AUG-84 Teet Dot.: 24-FEB-83 

1340 C --:-

11.0 11.2 
0.5 ~AL ~PECINE~ DISPL~CENfNT (n\IlIl1 -- I I 

0.0 I ) 

- O. 5 L-______ ~ ________ ~ ______ ~ ________ ~ ________ ~ ______ ~ ________ ~ _______ ~ ________ ~ ______ ~ ________ ~ ______ ~ ________ ~ ______ ~ 

o .2 r DISK RAD I A L DISPLACEMENT mm} 

0.0 

-0.2 ~c ____ ~ __ ~ ____ ~ __ ~ ____ ~ __ ~~ __ ~ __ ~ ____ ~ __ ~~ __ ~ ____ ~ __ ~ __ ~ 

30 I ;: I ~ 15 IDlSK_RtTATlON~L SP_E~D (krp~) I 

o I I 

~:: t N 

0 

R~~: ~~:~'IO""~''''W''tl!0I1!1_'''''' ...... io.l.1Ii ~ .. !.,.!lwlll.n"'II'ilfft~~*"'iIltl!"_1IiIIW.1 I 

0.4 ~ 0.0 I I 

0.4, TANG~NTlAL FORCE (kNl 

0.2 

0.0 I I 

8.4 8.6 8.8 9.0 9.2 9.4 9.6 9.8 10.0 UiL2 10.4 10.6 10.8 11.0 11.2 

RUB Test TCRL02 

TIME (sec.) 

Heduc~ion Do~e: 30-RUG-84 

TeST DOTe: 24-FfB-S3 
tJ 

I 

W 

tv 

SUBSURFACE TEMPERATURE 

NEAR- SURFACE TEMPERATURE 

22 

RUB Test TCRL03 

28 32 

Reduction Dote: 3B-~UG-84 

Tast Dote: 14-fEB-83 

48 
t:I 

I 

W 

W 

~.~ I SEAL $PECIN~N D ISP~ACE NE~T (mm ) n 

_: .. ~:m . ·11 

0.2 

0.0 

-0.2 =c __ ~ ____ ~ __ ~ __ ~ ____ ~ __ ~ ____ ~ __ ~ __ ~ ____ ~ __ ~ __ ~ __ ~ 

~: /DISKRGTATIONAt SPEED (krp~ ) . :1 

I .. . I 

o I I 

I. 2 t NOR MAL FORCE (k N) 

0.8 ) &'1'''''"*'1#1*': .. • .. *'tdhh, '1Yjj.ij.·".ll' lIul'I'f'l* C1> HIli •• HII." UN 

0.4 

0.0 

0.4 

0.2 

0.0 I I 

22 24 26 28 30 32 34 36 38 40 42 44 46 48 

RUB Test TCRL03 

TIME {sec.) 

Raduction Date: 30-RUG-84 

Test Date: 14-FEB-S3 
This Page Intentionally left Blank 
APPENDIX E 

A METALLURGICAL EXAMINATION OF A Ti-SAl-2.SSn DISK 

RUBBED AT -196°C AGAINST AN ALUMINUM PAD 

FURTHER OBSERVATIONS OF A Ti-SAl--2. SSn DISK 

RUBBED AT -196°C AGAINST AN ALUMINUM PAD 

by 

E. M. Schulson 

E.,..l 
A METALLURGICAL EXAMINATION OF A Ti-5Al-2.5Sn DISK 

RUBBED AT -196°C AGAINST AN ALUMINUM PAD 

ABSTRACT 

Scanning electron microscopy revealed extensive transfer of aluminum to 

titanium during the rubbing of a Ti-5Al-2.5 Sn disk at -196°C against a 

cooled 2024 (T35l) aluminum pad. The examination also revealed that the 

transfer was greater on one side of the disk than on the other. The 

transfer layer was cracked. 

E.l INTRODUCTION 

The purpose of this report is to summarize some observations of 

rubbing damage incurred by a Ti-SAl-2.5 Sn disk (No.1) when rubbed at 

25,000 rpm at -196°C (-320°F) against a 2024 (T35l) aluminum pad cooled to 

around -112°C (-170°F). The disk and pad were rubbed at Creare (at an 

interaction rate of 0.025 mm/sec (0.001 in./sec) and were submitted by F. 

Dolan for examination. 

E.2 EXAMINATION PROCEDURE 

Observations at magnifications up to 30X were make using a binocular 

microscope. Observations at higher magnifications (up to 3300X) were made 

on the disk only, using a scanning electron microscope (SEM) equipped with 

energy dispersive and wavelength dispersive spectrometers (EDS and WDS). 

SEM/EDS analyses were performed to estimate chemical compositions and, 

thus, to determine whether material was transferred from the pad to the 

disk during the rub. 

To facilitate the SEM examinations, four pieces (~ 1 em in length) 

were cut from the peripheral region of the disk at 90°, 180°, 270° and 360° 

(arbitrary co-ordinate system). One piece was cut from an un-rubbed disk, 

for reference. 

E.3 OBSERVATIONS 

E.3.l Pad 

Examination of the pad at 30X revealed extensive ridging (i.e. 

aluminum build-up) on the non-turbine side of the wear scar, along the full 

length of the track. On the turbine side, ridging occurred only at the 

entrance, over a distance of approximately one-quarter of the length of the 

scar. Curiously, a thin (~ 0.1 mm) tongue of material (presumed to be 

aluminum) ~ 0.3 mm in length, formed at the base of the scar at its 

entrance. These observations are illustrated in Figure E-l. When coupled 

with those by Dolan, who noted that the depth of the scar is deeper at the 

entrance than at the exit, they suggest that the rubbing occurred unevenly. 

E.3.2 Disk 

Examination of the disk at low magnification (30X) revealed that 

material transfer had occurred all along the periphery on the turbine side 

E-2 
of the blade near its periphery. Examination at higher magnification, made 

with the SEM, clearly revealed the transfer layer, Figure E-2. Moreover, 

they showed that in many places the layer was cracked, mainly in a radial 

direction, Figur~ E-3. Furthermore. these observations indicated that part 

of the transfer layer furthest from the periphery of the disk may have 

broken off, as suggested by the rough edge parallel to the periphery (heavy 

arrows, Figure E-3) and by the hairline cracks within the layer and 

parallel to the rough edge (fine arrows). 

On the opposite side of the disk (i.e. opposite the turbine side) 

clear evidence of material build-up was not seen. Instead, the peripheral 

region on this side contained dark patches within which superficial cracks 

appeared, Figure E-4. Unlike the cracks within the transfer layer on the 

turbine side of the disk, those on the opposite side had the appearance of 

an incision (Figure E-4b). Moreover, they appeared to have formed within a 

very thin surface skin of material, so thin that topographical features of 

the underlying disk were imaged through the "skin", Figure E-S. The last 

point, when combined with SEM contrast theory, suggests that the skin was 

less than a fraction of a micron in thickness. As suggested below (Section 

E.4) the skin is most probably a thin film of aluminum which transferred to 

the disk during an early stage of the rub. 

SEM/EDS analyses revealed that the transfer layer on the turbine side 

of the disk was rich in aluminum. Titanium was also detected, indicating 

either that the layer was sufficiently thin (~ 1 llm) to allow the transmis-· 

sian of X-rays, generated within the underlying disk by the incident 

electron beam (25 kV), or that the layer was an alloy of titanium and 

aluminum. Analysis of the thin, dark, cracked regions on the opposite side 

of the disk revealed titanium and a small amount of aluminum; in this case, 

the respective X-rays were most probably generated within the underlying 

disk, and are thus of little use in identifying the film. 

Concerning the periphery of the disk per se, striated features running 

in the direction of the rub were observed, all along the specimens examined, 

Figure E-6. In addition, pock marks (arrow, Figure F-6a) were noted. 

Striated features were evident on the periphery of an unrubbed blade, 

Figure E-6b, due to machining, but pock marks were not. Again, SEM/EDS 

analysis revealed strong X-ray peaks from aluminum and from titanium, 

indicating that the transfer of aluminum had occurred and either that this 

layer, too, was thin enough to allow the penetration of Ti X~rays generated 

within the disk below, or that alloying had occurred. 

E.4 DISCUSSION 

A number of questions arise from these observations. Do the cracks 

within the transfer layer on the turbine side of the disk extend through 

the layer and into the disk? Is the transfer layer alloyed with titanium? 

If not, does alloying occur at the layer/disk interface? What is the 

thickness of the layer? What is the nature of the very thin film on the 

side of the disk opposite the turbine? How do the cracks arise, and what 

is the structure (elongated grains? recrystallized grains?) of the transfer 

layer? And, does material transfer occur all along the periphery of the 

disk? 

E-·3 
Concerning the first question, conclusions cannot be drawn until 

additional metallography has been performed (now under way) on sections 

perpendicular to the plane of the disk and the plane of the cracks. 

Tentatively, however, it appears as though the cracks do not enter the 

disk. This point is deduced from the fact that the radial cracks terminate 

where the transfer layer appears to have broken off (Figure E-3). It is 

also in keeping with the incision-like appearance of the cracks on the 

opposite side of the disk, if one assumes that the skin is really comprised 

of aluminum or of an aluminum/aluminum oxide composite. 

Regarding the chemistry of the transfer layer and of the layer/disk 

interfacial region, meaningful comments are not possible until the sections 

noted in the foregoing paragraph have been prepared and subjected to 

SEM/EDS analysis. Similarly, good judgements about the thickness of the 

transfer layer must await such sectioning. 

Concerning the thin film, the only possibility that makes any sense is 

that it is comprised either of aluminum or of an aluminum/AI 03 composite, 

as alluded to above. The oxide of titanium, formed under amBient conditions 

prior to rubbing, is relatively thin « 150 A) and uniform; not patchy as is 

the skin observed here. Unambiguous identification, however, is not possible 

at this stage. If ambiguity is unacceptable, then an examination by Auger 

electron spectroscopy is recommended, preferably using a system which is 

equipped with an ion gun which can sputter away the first few atomic layers 

of "dirty" surface material. 

That cracks form in the aluminum-rich transfer layer and in the 

(assumed) aluminum skin may indicate either severe thermal shocks, a rather 

brittle aluminum-titanium alloy, or both. The globular character of parts 

of the transfer layers, evident in Figures E-2b and E-3b, suggests that the 

aluminum may have been molten when undergoing transfer onto the cold disk. 

If so, then the cracks could have arisen during the sharp quench which 

followed. To test for this possibility is not easy: examinations of the 

structure of the layer using transmission electron microscopy would be 

informative, but, because the layer was probably subsequently rubbed after 

being deposited, may not provide unambiguous evidence concerning the 

process of build-up. 

Finally, concerning the periphery, there is no reason to suspect that 

the transfer of aluminum is restricted to localized regions, for it was 

quite uniform along' the sample (albeit small in relation to the circumference of the disk, ~ 1 cm vs. ~ 75 cm). Certainty, however, would 

require examination of the complete periphery; an easy but time-consuming 

exercise. 

E.S CONCLUSIONS 

It is concluded that: 

a. During the first trial at -196°C, rubbing occurred more heavily 

on the turbine side of the disk. 

b. During rubbing, aluminum was transferred to the periphery and to 

the peripheral edges of the disk. Owing to (a), more material 

transferred to the turbine side of the disk. 

c. Cracks formed at localized sites within the transferred material. 

E-4 
FURTHER OBSERVATIONS OF A Ti-SAI-2.SSn DISK 

RUBBED AT -196°C AGAINST AN ALUMINUM PAD 

'l'his note summarizes some additional observations concerning the 

transfer of material from the Al pad to the Ti disk. The observations were 

made to determine whether the radial cracking noted in the transferred 

layer enters the Ti disk. 

~:he specimen examined was one of the four pieces mentioned earlier. 

It wa~l mounted on end in epoxy (cold-mounted), and then mechanically 

polished (to the level of 0.3 ].lm Al20

3 ) to reveal the AI/Ti interface. To 

prevent tensile stresses from developl.ng normal to the interface, all 

polishing was performed in a direction parallel to this interface. 

Metallographic examination was performed using a Reichert MeF2 metallograph 

at magnifications up to lSOO times. 

Clear views of the transferred layer and disk, together in focus, were 

not possible, owing to a rounding of the softer transfer material. 

HowevE,r, by focusing on the disk and then on the layer the following 

observations were made: 

L Cracks were not detected within the Ti disk, neither at any point 

along the AI/Ti interface (approximately S mm examined) nor away 

from the interface. They were seen in the Al transfer layer, 

Figure E-7. 

2. At several points along the interface, the layer had separated 

from the disk, Figure E-8. 

3. The transfer layer is approximately 3 to 4 ].lm in thickness. 

~:ha t cracks could not be seen wi thin the disk, but could be detected 

within the transfer layer, strongly indicates that crack propagation from 

the layer to the disk did not occur. This point supports the earlier 

deduction which was based upon the observation that the radial cracks 

within the transfer layer terminated at points where this layer broke free 

from the disk. 

It is not clear whether the separation at the layer/disk interface 

occurred during the rub (or immediately afterwards) or during the 

preparation of the specimen (even though care was taken to avoid such 

effects). The significant point is that the interface appears to be 

relatively weak. This point implies that tensile stresses which are 

induced within the transfer layer ahead of or in the plane of the crack are 

probably sufficient to promote decohesion. In turn, the decohesion acts as 

a crack stopping mechanism. Why decohesion occurs so easily cannot be 

determined without additional work. 

In conclusion, the evidence strongly suggests that the cracks which 

form within a layer of Al transferred from an Al pad to a Ti disk during 

cold rubbing at -196°C do not propagate into the disk. 

-------------

E--S 
(a) 

(b) 

Figure E.l Optical Macrographs Showing the Wear Scar in 

an Aluminum (2024 T35l) Pad. Cal the entrance 

to the pad, and (b) the exit. 

E-6 
(a) 

(b) 

Figure E.2 SEM Micrographs Showing a Transfer Layer on 

the Turbine Side of the Disk (Periphery of 

disk at or above top of photo) 

(b) higher magnification view of 

circled region in (a) 

E-7 
(a) 

(b) 

Figure E.3 SEM Micrographs of Transfer Layer on the 

Turbine Side of Disk Showing Cracks in the 

Layer. (Two separate locations, about 180 0 

apart, near the periphery of the disk. 

E-8 
(a) 

(b) 

Figure E.4 SEM Micrographs Showing Cracks in Thin Films 

on the Side of the Disk Opposite the Turbine 

(Two separate areas) 

E-9 
Figure E.5 SEM Micrograph Showing Incision-Like Crack 

Within a Thin Film on the Side of the Disk 

(Note the transparency of the film) 

E-10 
( a) 

.. ... fO 14m 

(b) 

Fig-ure E.6 SEM Microgra.l2.0.s: a) showing the periphery of. 

disk No. 1 after rubbing (2200X) Note the poc~ ~ __ (arrow)i (b) shOwing !he periphery of a 

disk which was not rubbed (lOOOX) 

E--U 
I I IOpm 

Ti 

Figure E.7 Optical micrograph showing the interface between an 

Al (2024) transfer layer and a Ti(SAI-2.S Sn) disk. 

Note the cracks (fine arrows) within the transfer 

layer (heavy arrows) . 

Figure E.8 As Figure E.7 but at a different location along the 

layer/disk interface. Note the crack (arrow) which 

lies along the layer/disk interface .. 

E-12 
APPENDIX F 

SEM PHOTOMICROGRAPHS OF WEAR SPECIMENS 

F-l 
APPENDIX F 

SEM Photomicrographs of Wear Specimens 

This Appendix contains photographs of the rubbed knife edge and wear 

ring surfaces taken with a scanning electron microscope. SEM micrographs 

from 14 of the rub interaction tests are displayed here; photographs of the 

titanium and aluminum wear surfaces from test TIAL03 are shown separately 

in Appendix E. 

The photographs in this Appendix are grouped to show the mating wear 

ring and knife edge surfaces from one test as parts (a) and (b) of each 

figure, respectively. Most figures have views of the wear surfaces at 

several magnifications and with common magnifications for many of the 

specimens. A length scale is included on each photograph as an aid to 

measuring surface features and for comparison of features on different 

specimens. The test materials, interaction rate and test number are also 

identified on the figures. 

Following is a compilation of brief comments recorded during the 

examinations of the wear components. The dominant feature observed is the 

evidence of melting of the aluminum and copper wear surfaces, indicative of 

high surface temperatures during the rubs. Also, the 

aluminum/silicon/graphite composite wear ring surface appeared to be least 

damaged as a result of the rub interaction tests. 

F-2 
Test 

TIAL02 

TIAL13 

TIAL23 

TIAL04 

TICU03 

TIAG02 

TIAG03 

TIYZ03 

TNAL02 

TNAL03 

AOAL02 

AOAL03 

TCAL02 

TCAL03 

Summary of Comments from SEM 

Examination of Wear Components 

Comments 

• wear scar filled with tiny cracks transverse to 

rub direction 

• evidence of melting on pad and disk 

• wear scar filled with "mud flat" type cracks 

• evidence of melting 

• smearing on pad and disk 

• cracks in scar but fewer than TIALl2 and TIAL02 

• again melting and smearing on pad and disk 

• found no cracks in scar 

• smearing on pad and disk 

• evidence of melting on pad and disk 

• cracks in scar 

• evidence of melting in scar 

• smearing on disk 

• clean scar, but smeared; no ridges along edge 

• titanium transferred to pad 

(determined from SEM/EDS) 

• similar to TIAG02 (no SEM/EDS) 

• pad badly cracked 

• deposit, presumed to be YSZ at one position 

on circumference of disk (see Figure 4-9) 

• cracks in scar 

• evidence of solidified metal droplets on pad and 

disk; smeared droplets 

• crack in base of scar; smearing but fewer than 

TNAL02 

• again evidence of melting on pad and disk 

• melting and smearing on pad and disk 

• cracks on disk 

• cracks in scar on pad 

• melting and smearing on pad and disk 

• cracks in scar 

• flaky and cracked ridge along edge of scar 

• melting and smearing on pad and disk 

• no cracks found in scar 

• melting and smearing 

• aluminum transfer to disk 

(determined from SEM/EDS) 

F-·3 
WEAR RING MATERIAL: 

2024-T351 ALUMINUM 

KNIFE EDGE MATERIAL: 

T i - 5 A 1- 2.5 Sn ALLOY, ANNEALED 

INTERACTION RATE: 

1.3x 10- 1 mm/sec 

FIGURE F-la.SEM MICROGRAPH OF WEAR RING SURFACE 

TEST NO. TI AL02 

F-4 
WEAR RING MATERIAL: 

2024 T 351 ALUMINUM 

KN I FE EDGE MATER IAL: 

T i - 5 A 1- 2.5 S n ALLOY, ANNEALED 

INTERACTION RATE: 

1.3x 10- 1 mm/sec 

FIGUREF-Ib. SEM MICROGRAPH OF KNIFE EDGE SURFACE 

TEST NO. TIAL02 

F-5 
WEAR RING MATERIAL: 

2024T351 ALUMINUM 

K N I FEE D GEM AT E R I A L: 

Ti - 5AI-2.5 Sn ALLOY, ANNEALED 

INTERACTION RATE: 

0.99 x 10 -zmm/sec 

FIGUREF-2a.SEM MICROGRAPH OF WEAR RING SURFACE 

TEST NO. TIALl3 

F-6 
WEAR RING MATERIAL: 

2024 T 3 51 A LU MIN U M 

KN I FE EDGE MATER IAL: 

Ti - SAI- 2.5 Sn ALLOY) ANNEALED 

INTERACTION RATE: 

0.99 x 10- 2 mm/sec 

FIGUREF .. 2b.SEM MICROGRAPH OF KNIFE EDGE SURFACE 

TEST NO. TIALl3 

F-7 
WEAR RING MATERIAL: 

2024T351 ALUMINUM 

KNIFE EDGE MATERIAL: 

Ti -5AI-2.5Sn ALLOY) ANNEALED 

INTERACTION RATE: 

1.09 x 10 - 2 mm/sec 

FIGURE F-3a.SEM MICROGRAPH OF WEAR RING SURFACE 

TEST NO. TIAL23 

F-8 
WEAR RING MATERIAL: 

2024 T 351 ALUM INUM 

KNIFE EDGE MATERIAL: 

T i -5 AI· 2 .5S n ALLOY, ANNEALED 

INTERACTION RATE: 

I. 09 x 10 - 2 m m / se c 

FIGURE F-3b. SEM MICROGRAPH OF KNIFE EDGE SURFACE 

TE S T NO. T I A L 2 3 

F-9 
WEAR RING MATERIAL: 

2024T351 ALUMINUM 

KNIFE EDGE MATERIAL: 

Ti -5AI-2.5 Sn ALLOY,ANNEALED 

INTERACTION RATE: 

1.65 x 1O-3mm/sec 

FIGURE F-40.SEM MICROGRAPH OF WEAR RING SURFACE 

TEST NO. Tr'AL04 
WEAR RING MATERIAL: 

2024 T351 ALUMINUM 

KN I fEE DGE MATER IAL: 

T i - !;AI- 2.5 S n ALLOY, ANNEALED 

INTERACTION RATE: 

I. 65 x 10 -3 mm/sec 

FIGUREF··4b.SEM MICROGRAPH OF KNIFE EDGE SURFACE 

TEST NO. TIAL04 
WEAR RING MATERIAL: 

99.99 OJo PUR E CO PPER, 

OXYGEN FREE 

KNIFE EDGE MATERIAL: 

Ti -SAI-2.SS n ALLOY,ANNEALED 

INTERACTION RATE: 

2.54x 10- 2 mm Isec 

FIGURE F-Sa.SEM MICROGRAPH OF WEAR RING SURFACE 

T EST N O. TIC U 03 
WEAR RING MATERIAL: 

99.99 "lo PURE COPPER, 

OXYGEN FREE 

KNIFE EDGE MATERIAL: 

Ti - 5AI-2.5Sn ALLOY, ANNEALED 

INTERACTION RATE: 

2.54x 10- 2 mm/sec 

FIGURE F-5b.SEM MICROGRAPH OF KNIFE EDGE SURFACE 

TES T NO. TIC U 03 

F-13 
WEAR RING MATER IAl: 

ALUM I NUM I SILICONI 

GRAPHITE COATING, 

METCO CE-2198A 

KNIFE EDGE MATERIAL: 

T i -5AI- 2.5Sn ALLOY, ANNEALED 

INTERACTION RATE: 

1.45x IO- Imm/sec 

FIGURE F-60.SEM MICROGRAPH OF WEAR RING SURFACE 

TEST NO. TIAG02 

F-H 
WEAR RING MATERIAL: 

A LU MIN U M / S I L I CON I 

GRAPHITE COATING, 

METeo CE - 2074 A 

KN If E EDGE MATER IAL: 

Ti-5AI-2.5Sn ALLOY,ANNEALED 

INTERACTION RATE: 

1.45x 10- 1 mm/sec 

F I(;URE F-6b.SEM MICROGRAPH OF KNIFE EDGE SURFACE 

TEST NO. TIA.G02 

F-15 
WEAR RING MATERIAL: 

A LU MIN U MIS I Lf C ON I 

GRAPHITE COATING, 

METCO CE-2074A 

KN I FE f DGE MATER IAL: 

Ti - 5A ,- 2.5 Sn ALLOY, ANN fALED 

INTERACTION RATE: 

1.8 x 1O- 2mm/sec 

FIGURE F-70. SEM MICROGRAPH OF WEAR RING SURFACE 

TEST NO. TIAG03 

F-16 
WEAR RING MATERIAL: 

ALUMINUM /SILICON I 

GRAPHITE COATING, 

METCO CE-2074A 

KNifE EDGE MATERIAL: 

Ti -5 AI-2.5Sn ALLOY I ANNEALED 

INTERACTION RATE: 

\.8 x 10- I m m / se c 

FIGUREF-1b.SEM MICROGRAPH OF KNIFE EDGE SURFACE 

TEST NO. TIAG03 

F-17 
WEAR RING MATERIAL: 

Yttrig - STAB ILiZED 

ZIRCONIA COATING, 

METCO CE-219BA 

KNIFE EDGE MATERIAL: 

Ti -5AI- 2.5 Sn ALLOY, ANNEALED 

INTERACTION RATE: 

2.24 x 10 -2 mm/sec 

fiGURE F-Bo.SEM MICROGRAPH OF WEAR RING SURFACE 

TEST NO. TIYZ03 

F-18 
WEAR RING MATER tAL: 

Yttrio -STABILIZED 

ZIRCONIA COATING, METeo CE-2198A 

KN I FE EDGE MATER tAL: 

Ti -5AI-2.5 Sn ALLOY, ANNEALIED 

INTERACTION RATE: 

2.24 x 1O- 2mm/sec 

FIGUREf~8b.SEM MICROGRAPH OF KNIFE EDGE SURFACE 

TEST NO. TIYZ03 

F-19 
WEAR RING MATERIAL: 

2024-T351 ALUMINUM 

KN I FEE DGE MATER IAL: 

Ti -SAI-2.S Sn ALLOY, ANNEALED 

INTERACTION RATE: 

1.04 x 10- 1 mm/sec 

FIGUREF-9a.SEM MICROGRAPH OF WEAR RING SURFACE 

TEST NO. TNAL02 

F-20 
WEAR RING MATER IAL: 

2024 - T351 ALUMINUM 

K N I FEE D GEM AT E R I A L: 

Ti -5 A 1- 2.5 Sn ALLOY) A NN£ALED 

INTERACTION RATE: 

-I I. 04 x 10m m I sec 

FIGURE f-9b.SEM MICROGRAPH OF KNIFE EDGE SURFACE 

TEST NO. TN AL02 

F-21 
WEAR RING MATERIAL: 

2024 - T35 I ALUM I NUM 

KNIfE EDGE MATERIAL: 

In NITR' OED TITAN IUM ALLOY 

INTERACTION RATE: 

2. I x 10 -zmm Isec 

FIGURE F-IOa.SEM MICROGRAPH OF WEAR RING SURFACE 

TES T NO. TNAL03 

F-22 
WEAR RING MATERIAL: 

2024-T351 ALUMINUM 

KNIFE EDGE MATERIAL: 

In NITRIDED TITANIUM ALLOY 

INTERACTION RATE: 

2.1 x 10- 2 mm /sec 

FIGURE F -lOb. SEM MICROGRAPH OF KNIFE EDGE SURFACE 

TEST NO. TNAL03 

F-23 
WEAR RING MATERIAL: 

20 24 T 3 51 A LU MIN U M 

KNIFE EDGE MATERIAL: 

ALUMINA ITITANIA COATING, METCO IOIB-NS 

INTERACTION RATE: 

I. 06 x 10 - I m m I sec 

FIGURE F-lla.SEM MICROGRAPH OF WEAR RING SURFACE 

TEST NO. AOAl02 

F-24 
WEAR RING MATERIAL: 

2024 T351 ALUMINUM 

KNIFE EDGE MATERIAL: 

ALUMINA/TITANIA COATING, 

METCO 10IB-NS 

INTERACTION RATE: 

I.06x 10-lmm/sec 

FIGURE F-llb. SEM MICROGRAPH OF KNIFE EDGE SURFACE 

TEST NO. AOA L02 

F-25 
WEAR RING MATERIAL: 

2024-T35IALUMINUM 

KNIFE EDGE MATERIAL: 

ALUMINA ITITANI A COATING) 

METCO IOIB-NS 

INTERACTION RATE: 

1.75x IO-2mm/sec 

FIGURE F-120. SEM MICROGRAPH OF WEAR RING SURFACE 

TEST NO. AOAL03 

F-26 
WEAR RING MATERIAL: 

2024 T 351 ALUM INUN 

KN I FEE DGE MATER IAL: 

ALUMINA/TITANIA COATING, 

METCO IOIB-NS 

INTERACTION RATE: 

1.15 x 10 -2 m m / se c 

FIGURE F·-12b.SEM MICROGRAPH OF KNIFE EDGE SURFACE 

TEST NO. A-OA L03 

F-27 
WEAR RING MATERIAL: 

2024T351 ALUMINUM 

KN I FE EDGE MATER IAL: 

TUNGSTEN CAR B 10 E + 

COBALT - CH ROMI U M COATING, 

UCAR LW-15 

INTERACTION RATE: 

1.2IxIO- l mm/sec 

FIGURE F-13a. SEM MICROGRAPH OF WEAR RING SURFACE 

TEST NO. Te AL02 

F-28 
WEAR RING MATERIAL: 

20241351 ALUMINUM 

KNIFE EDGE MATERIAL: 

TUNGSTEN CARBIDE + 

COBALT CHROMIUM COATING, 

UCAR LN-15 

INTERACTION RATE: 

1.21 x 10-l mm Isec 

FIGURE F-13b.SEM MICROGRAPH OF KNIFE EDGE SURFACE 

TEST NO. TCAL02 

F-29 
WEAR RING MATERIAL: 

2024T351 ALUMINUM 

KNIFE EDGE MATERIAL: 

TUNGSTEN CARBIDE+ 

CO BALI - CHROM I U N COATI NG, 

UCAR LW-15 

INTERACTION RATE: 

1.1 x 10 -2 mm/sec 

FIGURE,F-140.SEM MICROGRAPH OF WEAR RING SURFACE 

TEST NO. TCAL03 

F-30 
WEAR RING MATER IAL: 

2024 T351 ALUM INUM 

KNIFE EDGE MATERIAL: 

TUNGSTEN CARBIDE+ 

COBALT - CHROM I UM COATING} UCAR LW-15 

INTERACTION RATE: 

1.1 x 10- 2 mm/sec 

FIGURE F-14b.SEM MICROGRAPH OF KNIFE EDGE SURFACE 

TEST NO. TCAL03 

F-31 
End of Document