NASA/TMm2001-211205

Evaluation of Ti-48A1-2Cr-2Nb

Under Fretting Conditions

ASTM STP 1425

Kazuhisa Miyoshi, Bradley A. Lerch, Susan L. Draper, and Sai V. Raj

Glenn Research Center, Cleveland, Ohio

November 2001

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NASA/TM--2001-211205 ASTM STP 1425

Evaluation of Ti-48A1-2Cr-2Nb

Under Fretting Conditions

Kazuhisa Miyoshi, Bradley A. Lerch, Susan L. Draper, and Sai V. Raj

Glenn Research Center, Cleveland, Ohio

Prepared for the

Third International Symposium on Fretting Fatigue

sponsored by the American Society for Testing and Materials

Nagaoka-shi, Japan, May 15-18, 2001

National Aeronautics and

Space Administration

Glenn Research Center

November 2001
Acknowledgments

The authors are grateful to Dr. Gary R. Halford and Dr. Michael V. Nathal for very helpful discussions.

!

Trade names or manufacturers" names are used in this report for

identification only. This usage does not constitute an official

endorsement, either expressed or implied, by the National

Aeronautics and Space Administration.

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Available electronically at http: //gltrs.grc.nasa.gov/GLTRS
Evaluation of Ti-48Al-2Cr-2Nb Under Fretting Conditions

Kazuhisa Miyoshi, Bradley A. Lerch, Susan L. Draper, and Sai V. Raj

National Aeronautics and Space Administration

Glenn Research Center

Cleveland, Ohio 44135

Abstract: The fretting behavior of Ti-48A1-2Cr-2Nb a (7-TiA1) in contact with the nickelbase superalloy 718 b was examined in air at temperatures from 296 to 823 K (23 to

550 °C). The interracial adhesive bonds between Ti-48A1-2Cr-2Nb and superalloy 718

were generally stronger than the cohesive bonds within Ti-48A1-2Cr-2Nb. The failed

Ti-48A1-2Cr-2Nb debris subsequently transferred to the superalloy 718. In reference

experiments conducted with Ti-6AI-4V against superalloy 718 under identical fretting

conditions, the degree of transfer was greater for Ti-6A1-4V than for Ti-48A1-2Cr-2Nb.

Wear of Ti-48A1-2Cr-2Nb generally decreased with increasing fretting frequency. The

increasing rate of oxidation at elevated temperatures led to a drop in wear at 473 K.

However, fretting wear increased as the temperature was increased from 473 to 823 K.

At 723 and 823 K, oxide film disruption generated cracks, loose wear debris, and pits on

the Ti-48A1-2Cr-2Nb wear surface. Both increasing slip amplitude and increasing load

tended to produce more metallic wear debris, causing severe abrasive wear in the

contacting metals.

aComposition, at.%: titanium, 47.9; aluminum, 48.0; niobium, 1.96; chromium, 1.94;

carbon, 0.013; nitrogen, 0.014; and oxygen, 0.167.

_Composition, wt.%: nickel, 50-55; chromium, 17-21; iron, 12-23; niobium plus

tantalum, 4.75-5.5; molybdenum, 2.8-3.3; cobalt, 1; titanium, 0.65-1.15; aluminum,

0.2-0.8; silicon, 0.35; manganese, 0.35; copper, 0.3; carbon, 0.08; sulfur, 0.015;

phosphorus, 0.015; and boron, 0.006.

NASA/TM--2001-211205 1
Introduction

Adhesion, a manifestation of mechanical strength over an appreciable area, has

many causes, including chemical bonding, deformation, and the fracture processes

involved in interface failure. A clean metal in contact with another clean metal will fail

either in tension or in shear because some of the interracial bonds are generally stronger

than the cohesive bonds within the cohesively weaker metal [1]. The failed metal

subsequently transfers material to the other contacting metal. Adhesion undoubtedly

depends on the surface cleanliness; the area of real contact; the chemical, physical, and

mechanical properties of the interface; and the modes of junction rupture. The environment

influences the adhesion, deformation, and fracture behaviors of contacting materials in

relative motion.

Clean surfaces can be created by repeated sliding in vacuum, making direct contact

of the fresh, clean surfaces unavoidable in practical cases [2]. This situation also applies in

some degree to sliding contact in air, where fresh surfaces are continuously produced on

interacting surfaces in relative motion. Microscopically small, surface-parallel relative

motion, which can be vibratory (in fretting or false brinnelling) or creeping (in fretting),

produces fresh, clean interacting surfaces and causes junction (contact area) growth in the

contact zone [3-5].

Fretting wear produced between contacting elements is adhesive wear taking place

in a nominally static contact under normal load and repeated microscopic vibratory motion

[6-10]. The most damaging effect of fretting is the possibly significant reduction in the

fatigue capability of the fretted component, even though the wear produced by fretting

appears to be quite mild [10]. For example, Hansson, et al. reported that the reduction in

fatigue strength by fretting of Ti-47A1-2Nb-2Mn containing 0.8 vol.% TiB 2 was

approximately 20 percent.

Fretting fatigue is a complex problem of significant interest to aircraft engine

manufacturers [ii'i4]_ Fretting failure can occur in a variety of engine components.

Numerous approaches, depending on the component and the operating conditions, have

been taken to address the fretting problem. The components of interest in this investigation

were the low-pressure turbine blades and disks. The blades in this case were titanium

aluminide and the disk was a nickel-base superalloy. A concern for these airfoils is the

fretting in fitted interfaces at the dovetail where the blade and disk are connected. Careful

design can reduce fretting in most cases, but not completely eliminate it, because the

airfoils frequently have a skewed (angled) blade-disk dovetail attachment, which leads to

a complex stress state. Further, the local stress state becomes more complex when the

influence of the metal-metal contact and the edge of contact is evaluated.

Because titanium and titanium-base alloys in the clean state will exhibit strong

adhesive bonds [2, 15] when in contact with themselves and other materials, this adhesion

causes heavy surface damage and high friction in practical cases. Therefore, it is possible

that fretting will be a serious concern in this application.

The objective of this investigation was to evaluate the extent of fretting damage on

Ti-48A1-2Cr-2Nb (_/-TiA1) in contact with the nickel-base superalloy 718 at temperatures

from 296 to 823 K. Selected reference experiments were also conducted with Ti-6A1-4V.

There is a large experience base with Ti-6A1-4V, which has been used extensively as a

compressor blade material. The parameters of microscopic, surface-parallel motion, such

as fretting frequency, slip amplitude, and load, were systematically examined in this study.

Scanning interference microscopy (noncontact optical profilometry) was used to evaluate

NASA/TM--2001-211205
surface characteristics, such as topography, roughness, material transfer, and wear volume

loss. Scanning electron microscopy with energy-dispersive spectroscopy was used to

determine the morphology and elemental composition of fretted surfaces, transferred

material, and wear debris.

Materials

The Ti-48A1-2Cr-2Nb specimens were determined to be of the following

composition (in atomic percent): titanium, 47.9; aluminum, 48.0; niobium, 1.96;

chromium, 1.94; carbon, 0.013; nitrogen, 0.014; and oxygen, 0.167. The tensile properties

are shown in Table 1.

Table 1--Tensile Propen&sofTi-48Al-2Cr-2Nb

Temperature, K Modulus, GPa ] Ultimatetensile s_en_th, MPa

293 923 170 140 ] 410 460

The nickel-base superalloy 718 specimens were of the following nominal

composition (in weight percent): nickel, 50-55; chromium, 17-21; iron, 12-23; niobium

plus tantalum, 4.75-5.5; molybdenum, 2.8-3.3; cobalt, 1; titanium, 0.65-1.15; aluminum,

0.2--0.8; silicon, 0.35; manganese, 0.35; copper, 0.3; carbon, 0.08; sulfur, 0.015;

phosphorus, 0.015; and boron, 0.006 [16]. Superalloy 718 was solutioned and aged

according to Aerospace Material Specification AMS 5596G, SAE, Warrendale, PA, 1987,

yielding Rockwell C-scale hardness HRc of 36. The tensile properties [16] are shown in

Table 2. The ultimate tensile strength of superalloy 718 is greater than that of Ti-48AI-2Cr2Nb by a factor of ~3.5 at room temperature and -2 at high temperature (-1000 K).

Table 2mTensile Properties of Nickel-Base Superalloy 718

Temperature, K [ Modulus, GPa Ultimate tensile strength, MPa

293 [ 200 1434

811 [ 171 1276

1033 [ 154 758

The reference Ti-6AI-4V specimens were of the following nominal composition (in

weight percent): titanium, balance; aluminum, 5.5-6.75; vanadium, 3.5--4.5; iron, <0.30;

carbon, <0.08; nitrogen, <0.05; oxygen, <0.20; and hydrogen, <0.015 [17].

Experiments

Figure 1 presents the fretting wear apparatus used in this investigation. Fretting

wear experiments were conducted with 9.4-mm-diameter, hemispherical nickel-base

superalloy 718 pins in contact with Ti-48A1-2Cr-2Nb fiats or with 6-mm-diameter,

hemispherical Ti-48A1-2Cr-2Nb pins in contact with nickel-base superalloy 718 fiats in air

NASA/TM--2001-211205 3
Sensor

_-- Oscillation

I

t

Sensor

Pin -_,., _

_ _ Test

_,, j__ specimen

_f_'_t__--- Oscillatio n

_De_ailThermOcOuple

Figure l--Fretting apparatus.

CD-01-81402

at temperatures from 296 to 823 K. All the flat and pin specimens used were polished with

3-I.tm-diameter diamond powder. Both pin and flat surfaces were relatively smooth, having

centerline-average roughness R a in the range 18 to 83 nm (Table 3). The Vickers hardness,

measured at a load of I N, for the polished fiat and pin specimens is also shown in Table 3.

NASA/TM--2001-211205 4
Table 3--Surface Roughness and Vickers Hardness of Specimens

Specimen

9.4-mm-diameter,

hemispherical, nickel-base

superalloy 718 pin

6-ram-diameter,

hemispherical Ti-48A1-2Cr2Nb pin

9.4-mm-diameter,

hemispherical Ti-6A1-4V pin

Ti-48A1-2Cr-2Nb flat

Nickel-base superalloy 718

flat

Centerline-average Vickers hardness", H v, GPa

roughness, R a, nm

Mean Standard Mean Standard

deviation deviation

40 8.9 5.52 0.44

42 7.1 4.12 0.42

83 2.0 3.85 0.092

35 3.3 3.78 0.57

18 7.2 4.78 0.21

"Load, 1 N.

All fretting wear experiments were conducted at!oads from 1 to 40 N, frequencies

of 50, 80, 120, and 160 Hz, and slip amplitudes between 50 and 200 ktm for 1 million to

20 million cycles. Both pin and flat surfaces were rinsed with 200-proof ethyl alcohol

before installation in the fretting apparatus.

Two or three fretting experiments were conducted with each material couple at each

fretting condition. The data were averaged to obtain the wear volume losses of Ti-48A1-

2Cr-2Nb and Ti-6AI-4V. The wear volume loss was determined by using an optical

profiler (noncontact, vertical scanning, white-light interferometer). It characterizes and

quantifies surface roughness, height distribution, and critical dimensions (such as area and

volume of damage, wear scars, and topographical features). It has three-dimensional

profiling capability with excellent precision and accuracy (e.g., profile heights ranging

from <1 nm up to 5000 lam with 0.1-nm height resolution). The shape of a surface can be

displayed by a computer-generated map developed from digital data derived from a threedimensional interferogram of the surface. A computer directly processes the quantitative

volume and depth of a fretted wear scar. Reference fretting wear experiments were

conducted with 9.4-mm-diameter hemispherical Ti-6A1-4V pins in contact with nickelbase superalloy 718 flats.

Results and Discussion

Observations

Surface and subsurface damage always occurred on the interacting surfaces of the

Ti-48A1-2Cr-2Nb fretted in air. The surface damage consisted of material transfer, pits,

oxides and debris, scratches, fretting craters and/or wear scars, plastic deformation, and

cracks.

NASA/TM--2001-211205 5
Adhesion and Material Transfer--Figure 2 presents a backscattered electron image

and an energy-dispersive x-ray spectrum (EDS) taken from the fretted surface of the

nickel-base superalloy 718 pin after contact with the Ti-48A1-2Cr-2Nb flat. Clearly, Ti48A1-2Cr-2Nb transferred to superalloy 718. The Ti-48A1-2Cr-2Nb failed either in tension

or in shear because some of the interfacial adhesive bonds (solid state or cold welding)

were stronger than the cohesive bonds within the cohesively weaker Ti-48A1-2Cr-2Nb.

C

a¢

O

O

50xl 03

30-

20

10

"n Ni

0

0

CF

Fe

-o II

i! i !ii iiil i !' i!l_ i_._

2 4 6 8 10 12 14

Electron energy, keV

Figure 2--Wear scar on superalloy 718pin fretted against 77-48Al-2Cr-2Nb flat. (a) SEM

backseattered electron intage. (b) X-ra), energv spectrum with EDS. Fretting conditions:

load, 115 3_;"frequency, 80 Hz; slip amplitude, 50ltm: total number of cycles, 1 million;

em,ironment, air," and temperature, 823 K.

NASA/TM--2001-211205 6
The ultimate tensile strength of superalloy 718 is greater than that of Ti-48A1-2Cr-2Nb by

a factor of -3.5 at room temperature and -2 at high temperature (- 1000 K). The failed Ti48A1-2Cr-2Nb subsequently transferred to the superalloy 718 surface in amounts ran_ng

from 10 to 60 percent of the superalloy 718 contact area at all fretting conditions in this

study. The thickness of the transferred Ti-48A1-2Cr-2Nb ranged up to -20 ktm.

As with the materials pair of Ti-48A1-2Cr-2Nb and superalloy 718, material

transfer was observed on the superalloy 718 flat surface after fretting against the Ti-6A1-4V

pin at 696 and 823 K in air. However, the degree of material transfer was remarkably

different and greater, ranging from 30 to 100 percent of the superalloy 718 contact area for

identical fretting conditions. The thickness ranged up to 50 ktm.

Fretting Wear--Figure 3 shows typical wear scars produced on the Ti-48A1-2Cr2Nb pin and the superalloy 718 flat with fretting. Because of the specimen geometry a

large amount of wear debris was deposited just outside the circular contact area. Pieces of

the metals (both Ti-48A1-2Cr-2Nb and superalloy 718) and their oxides were torn out

during fretting. It appears that the cohesive bonds in some of the contact area of both

metals fractured. Scanning electron microscopy (SEM) and EDS studies of wear debris

produced under fretting verified the presence of metallic particles of both Ti-48AI-2Cr-2Nb

and superalloy 718. In the central region of wear scars produced on Ti-48A1-2Cr-2Nb there

was generally a large, shallow pit, where Ti-48A1-2Cr-2Nb had torn out or sheared off and

subsequently transferred to superalloy 718. The central regions of wear scars produced on

Ti-48A1-2Cr-2Nb and on superalloy 718 were morphologically similar (Fig. 3), generally

having wear debris, scratches, plastically deformed asperities, and cracks.

Figure 3--Wear scars (a) on 77-48Al-2Cr-2Nb pin and (b) on superalloy 718flat. Fretting conditions."

load, 1 N," frequenc); 80 Hz; slip amplitude, 5011m," total number of cycles, I million; environment, air,"

and temperature, 823 K.

Figure 4 shows examples of surface damage: metallic wear debris of Ti-48A1-2Cr2Nb and superalloy 718, oxides and their debris, scratches (grooves), small craters,

plastically deformed asperities, and cracks. The scratches (Fig. 4(a)) can be caused by hard

protuberances (asperities) on the superalloy 718 surface (two-body conditions) or by wear

particles between the surfaces (three-body conditions). Abrasion is a severe form of wear.

The hard asperities and trapped wear particles plow or cut the Ti-48A1-2Cr-2Nb surface.

The trapped wear particles have a scratching effect on both surfaces; and because they carry

part of the load, they cause concentrated pressure peaks on both surfaces. The pressure

NASA/TM--2001-211205 7
Figure 4--Surface and subsurface damage in 17-48Al-2Cr-2?_79flat in contact with superalloy 718pin.

(a) Scratches. (b) Cracks in oxide layers. (c) Cracks in metal. (d) Fracture pits and plastic deformation.

Fretting conditions: load, 1N; frequeney 80 Hz; slip amplitude and total number of cycles: (a) 501.tin

and 1 million, (b) 60[tm and 10 million, (c) 50 lan and 1 million, (d) 70glm and20 million; environment,

air; and temperature, 823 K

peaks may well be the origin of crack nucleation in the oxide layers and the bulk alloys.

Two types of crack were observed on the wear surface of Ti-48A1-2Cr-2Nb: cracks in the

oxide layers, and cracks in the bulk Ti-48A1-2Cr-2Nb.

Oxide layers readily form on the Ti-48AI-2Cr-2Nb surface at 823 K and are often

a favorablesolution to wear problems. However, if the bulk Ti-48AI'2Cr'2Nb is not hard

enough to carry the load, it will deform plastically or elastically under fretting contact. With

Ti-48A1-2Cr-2Nb, cracks occurred in the oxide layers both within and around the contact

areas (Fig. 4(b)).

Fractures in the protective oxide layers produced cracks in the bulk Ti-48AI-2Cr2Nb (Fig. 4(c)) and also produced wear debris; chemically active, fresh surfaces; plastic

deformation; and craters or fracture pits (Fig. 4(d)). The wear debris caused third-body

abrasive wear (Fig. 4(a)). Local, direct contacts between the fresh surfaces of Ti-48A1-2Cr2Nb and superalloy 718 resulted in increased adhesion and local stresses, which may cause

plastic deformation, flake-like wear debris, and craters (e.g., the fracture pits in the Ti48A1-2Cr-2Nb shown in Fig. 4(d)).

Cross sections of a wear scar on Ti-48A1-2Cr-2Nb revealed subsurface cracking

and craters. For example, Fig. 5 shows propagation of subsurface cracking, nucleation of

small cracks, formation of a large crater, and generation of debris. Cracks are transgranular

and have no preference to the microstructure.

NASA/TM--2001-211205 8
l

l

1

l

l

1

1

1

Figure 5--Cross-section view of wear scar on 17-48Al-2Cr-2Nb

flat in contact with superalloy 718pin. (a) Overview (b) Crack

growth. Fretting conditions: load, 30 N,"frequenc); 80 Hz; slip

amplitude, 701tm; total number of cycles, 20 million; environment, air,"and temperature, 823 K.

Parameters Influencing Wear Loss of Ti-48AI-2Cr-2Nb

Figure 6 shows the wear volume loss measured by the optical interferometer as

a function of fretting frequency for Ti-48A1-2Cr-2Nb in contact with superalloy 718.

Although there were some exceptions, the wear volume loss generally decreased with

increasing fretting frequency. A reasonable amount of material transfer from the Ti-48A1-

2Cr-2Nb specimen to the superalloy 718 specimen was observed at all frequencies. At

the lowest frequency of 50 Hz remarkable plastic deformation (grooving) and surface

roughening in the Ti-48A1-2Cr-2Nb wear scar were observed. At high frequencies wear

scars were noticeably smooth with bulk cracks in the Ti-48A1-2Cr-2Nb surface.

NASA/TM--2001-211205 9
O3

E

::k

o

E

=

6.0xl 0 4

4.0

[] Temperature,

K

O

[]

O

0 296

rl 823

[] []

O

O

2.0 l I I I

0 50 100 150 200

Frequency, Hz

Figure 6--Wear volume loss of 77-48Al-2Cr-2Nb flat in

contact with superallo), 718pin in air as function of

fi'etting frequenc): Fretting conditions: load, 30 N; slip

amplitude, 50/2m; total number" of cycles, 1 million;

environment, air," and temperatures, 296 and 823 I_:

O3

E

::X

o

_=

6.0xl 0 4

O

4.0 - O

2.0 <>

0 200

Frequency,

Hz []

O

50

[] 8O

o

120 Z_

160 <:>

I I

400 600

Temperature, °C

I I I I

273 473 673 873

Temperature, K

Figure 7--Wear volume loss of Ti-48AI-2Cr-2Nb flat

in contact with superalloy 718 pin in air as function

of fretting temperature. Fretting conditions: load,

30 N; slip amplitude, 50t.tm; total number of cycles,

1 million; em,ironment, air," and fretting frequencies,

50, 80, 120, and 160 Hz.

Temperature influences the adhesion, deformation, and fracture behaviors of

contacting materials in relative motion. It is "known that temperature interacts with the

fretting process in two ways: first, the rate of oxidation or corrosion increases with

temperature; and second, the mechanical properties, such as hardness, of the materials

are also temperature dependent [9]. Figure 7 presents the wear volume loss measured by

optical interferometry as a function of temperature for Ti-48A1-2Cr-2Nb in contact with

NASA/TM--2001-211205 10
superalloy 718. Also, SEM images and EDS spectra were taken from the fretted Ti-48A1-

2Cr-2Nb surfaces. The wear volume loss dropped to a low value at 473 K. The worn

surface at 473 K was predominantly oxide and relatively smooth. A protective oxide film

prevented direct metal-to-metal contact and ensured, in effect, that a mild oxidative wear

regime prevailed. However, fretting wear increased as the temperature was increased from

473 to 823 K. The highest temperatures of 723 and 823 K resulted in oxide film disruption

with crack generation, loose wear debris, and pitting of the Ti-48AI-2Cr-2Nb wear surface.

Figure 8 shows the wear volume loss measured by optical interferometry as a

function of slip amplitude for Ti-48A1-2Cr-2Nb in contact with superalloy 718. The

fretting wear volume loss increased as the slip amplitude increased. Increases in amplitude

tended to produce more metallic wear debris, causing severe abrasive wear in the

contacting metals. Figure 9 presents a three-dimensional, optical interferometry image of

the Ti-48A1-2Cr-2Nb wear scar at a slip amplitude of 200 _tm and a temperature of 296 K.

In the wear scar are large, deep grooves where the wear debris particles have scratched the

Ti-48A1-2Cr-2Nb surface in the slip direction.

Figure l0 shows the measured wear volume loss as a function of load for Ti-48A1-

2Cr-2Nb in contact with superalloy 718 at a temperature of 823 K, a fretting frequency of

80 Hz, and a slip amplitude of 50 _tm for 1 million cycles. The fretting wear volume loss

generally increased as the toad increased, generating more metallic wear debris in the

contact area, the primary cause of abrasive wear in both Ti-48A1-2Cr-2Nb and superalloy

718.

10 7

E 106

_o

E

105

"_- Temperature,

- K

O 296

[] 823

[]

D O

:- O

I I

O

104 1 I

0 50 100 150 200

Amplitude, pm 3

Figure 8--Wear vohtme loss of Ti-48Al-2Cr-2Nb flat

in contact with superalloy 718pin in air as function

of slip amplitude. Fretting conditions: load, 30 N,"

frequency, 50 Hz; total number of c),cles, 1 million;

environment, air," and temperatures, 296 and 823 K.

NASAfrM--2001-211205 11
lam

10.2

5.0

0.0

-5.0

-10.0

-15.0

-16.7

Figure 9--Wear scar on 77-48Al-2Cr-2Nb flat in contact with superalloy 718pin, showing

scratches. Fretting conditions." load, 30 N; frequenc3; 50 Hz; slip amplitude, 200pro; total

number of e),cles, 1 million; environment, air," and temperature, 296 K.

8.0xl 0 4

6.0-

:::L

4.0-

2.0 -

0

0

O

O

I

o

o

I I I

2 3 4

Load, N

Figure lO---Wear volume loss of 77-48Al-2Cr-2Nb flat

in contact with superalloy 718pin as function of

load. Fretting conditions: frequency, 80 Hz; slip

ampRtude, 50pro; total number of cycles, 1 million;

environment, air; and temperature, 823 K.

NAS A/TM--2001-211205 12
Concluding Remarks

The fretting behavior of y-TiA1 (Ti-48A1-2Cr-2Nb) in contact with nickel-base

superalloy 718 in air at temperatures of 296 to 823 K was examined with the following

results:

1. The Ti-48A1-2Cr-2Nb transferred to the superalloy 718 at all fretting conditions, such

that from 10 to 50 percent of the superalloy 718 contacting surface area became coated

with the Ti-48A1-2Cr-2Nb. The maximum thickness of the transferred Ti-48A1-2Cr2Nb was approximately 20 ktm. In reference experiments Ti-6A1-4V transferred to

superalloy 718 under identical fretting conditions. Compared with Ti-48A1-2Cr-2Nb

transfer, the degree of Ti-6A1-4V transfer was greater, such that from 30 to 100 percent

of the superalloy 718 contacting surface area became coated with the Ti-6AI-4V. The

thickness of the transferred Ti-6A1-4V ranged up to 50 _tm.

2. The wear scars produced on Ti-48AI-2Cr-2Nb contained metallic and oxide wear

debris, scratches, plastically deformed asperities, cracks, and fracture pits.

3. Although oxide layers readily formed on the Ti-48AI-2Cr-2Nb surface at 823 K,

cracking readily occurred in the oxide layers both within and around the contact areas.

4. The wear volume loss of Ti-48A1-2Cr-2Nb generally decreased with increasing fretting

frequency, increased with increasing temperature, and increased with increasing slip

amplitude.

5. Mild oxidative wear and low wear volume were observed at 473 K.

References

1. Miyoshi, K., "Foreword: Considerations in Vacuum Tribology (Adhesion, Friction,

Wear, and Solid Lubrication in Vacuum)," Tribology International, Vol. 32, 1999, pp.

605-616.

2. Miyoshi, K., "Aerospace Mechanisms and Tribology Technology: Case Study,"

Tribology International, Vol. 32, 1999, pp. 673-685.

3. Tallian, T.E., "Failure Atlas for Hertz Contact Machine Elements," Fretting Wear,

ASME Press, New York, 1992, pp. 141-154.

4. Waterhouse, R.B., "Plastic Deformation in Fretting Processes--a Review," Fretting

Fatigue: Current Technology and Practices, ASTM STP 1367, D.W. Hoeppner, V.

Chandrasekaran, and C.B. Elliot HI, Eds., American Society for Testing and Materials,

West Conshohocken, PA, 2000, pp. 3-18.

NASA/TM--2001-211205 13
5. Waterhouse,R.B.,"Occurrenceof Frettingin PracticeandIts Simulationin the

Laboratory,"Materials Evaluation Under Fretting Conditions, ASTM STP 780,

American Society for Testing and Materials, West Conshohocken, PA, 1982,

pp. 3-16.

6. Kusner, D., Poon, C., and Hoeppner, D.W., "A New Machine for Studying Surface

Damage due to Wear and Fretting," Materials Evaluation Under Fretting Conditions,

ASTM STP 780, American Society for Testing and Materials, West Conshohocken,

PA, 1982, pp. 17-29.

7. Satoh, T., "Influence of Microstructure on Fretting Fatigue Behavior of a Near-Alpha

Titanium," Fretting Fatigue: Current Technology and Practices, ASTM STP 1367,

D.W. Hoeppner, V. Chandrasekaran, and C.B. Elliot III, Eds., American Society for

Testing and Materials, West Conshohocken, PA, 2000, pp. 295-307.

8. Lutynski, C., Simansky, G., and McEvily, A.J., "Fretting Fatigue of Ti-6A1-4V

Alloy," Materials E_,aluation Under FretthYg Conditions, ASTM STP 780, American

Society for Testing and Materials, West Conshohocken, PA, 1982, pp. 150-164.

9. Bill, R.C., "Review of Factors That Influence Fretting Wear," Materials Evaluation

Under Fretting Conditions, ASTM STP 780, American Society for Testing and

Materials, West Conshohocken, PA, 1982, pp. 165-182.

10. Hansson, T., et al., "High Temperature Fretting Fatigue Behavior in an XD y-Base

TiAI," Fretting Fatigue: Current Technology and Practices, ASTM STP 1367, D.W.

Hoeppner, V. Chandrasekaran, and C.B. Elliot III, Eds., American Society for Testing

and Materials, West Conshohocken, PA, 2000, pp. 65-79.

11. VanStone, R,H., Lawless, B.H., and Hartle, M., "Fretting in Ti-6A1-4V at Room

Temperature," Proceedings of 5th National Turbine Engine High Cycle Fatigue

(HCF) Conference, 2000, Session 4, paper 1.

12. Chakravarty, S., et al., "The Effect of Surface Modification on Fretting Fatigue in Ti

Alloy Turbine Components," JOM, Vol. 47, No. 4, 1995, pp. 31-35.

13. Hoeppner, D., Adibnazari, S., and Moesser, M.W., "Literature Review and

Preliminary Studies of Fretting and Fretting Fatigue Including Special Applications to

Aircraft Joints," DOT/FAA/CT-93/2, Defense Technical Information Center, Ft.

Belvoir, VA, 1994.

14. Hutson A.L. and Nicholas, T., "Fretting Fatigue Behavior of Ti-6AI-4V Against Ti6A1-4V Under Flat-on-Flat Contact With Blending Radii," Fretting Fatigue: Current

Technology and Practices, ASTM STP 1367, D.W. Hoeppner, V. Chandrasekaran, and

C.B. Elliot [II, Eds., American Society for Testing and Materials, West

Conshohocken, PA, 2000, pp. 308-321.

15. Miyoshi, K., et al., "Sliding Wear and Fretting Wear of Diamondlike Carbon-Based,

Functionally Graded Nanocomposite Coatings," Wear, Vol. 225-229, 1999,

pp. 65-73.

16. Hunt, M.W. (Ed.), Materials Selector 1993, Materials Engineering, Penton Publishing,

Cleveland, OH, 1992.

17. Donachie, M.J. (Ed.), Titanium and Titanium Alloys, Source Book, American Society

for Metals, Metals Park, OH, 1982.

NASA/TM--2001 -211205 14

J

f

REPORT DOCUMENTATION PAGE FormApproved

OMB No. 0704-0188

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1. AGENCY USE ONLY (Leave b/ank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED

November 2001 Technical Memorandum

4. TITLE AND SUBTITLE

Evaluation of Ti-48AI-2Cr-2Nb Under Fretting Conditions

6. AUTHOR(S)

Kazuhisa Miyoshi, Bradley A. Lerch, Susan L. Draper, and Sai V. Raj

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

John H. Glenn Research Center at Lewis Field

Cleveland, Ohio 44135-3191

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546- 0001

5. FUNDING NUMBERS

WU-708-24-13-00

8. PERFORMING ORGANIZATION

REPORT NUMBER

E-13006-1

10. SPONSORING/MONITORING

AGENCY REPORT NUMBER

NASA TM--2001-211205

ASTM STP 1425

11. SUPPLEMENTARY NOTES

Prepared forthe Third lnternation_ Symposium on Fretting Fadguesponsored bythe American Society forTesting

and Matefials, Nagaoka-s_,Japan, May 15-18,2001. Responsible person, KazuhisaMiyoshi, organization

code 5160,216-433-6078.

12a. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified -Unlimited

Subject Category: 26 Distribution: Nonstandard

Available electronically at httv://dtrs.t, rc.n_sa._ovlGLTRS

This publication is available from the NASA Center for Ae_oSpace Information, 301-62t-0390.

13. ABSTRACT (Maximum 200 words)

12b. DISTRIBUTION CODE

The fretting behavior of Ti-48AI-2Cr-2N-b (y-TiAl) in contact with the nickel-base superalloy 718 was examined in air at

temperatures from 296 to 823 K (23 to 550 °C). The interfacial adhesive bonds between Ti-48A1-2Cr-2Nb and superalloy

718 were generally stronger than the cohesive bonds within Ti-48AI-2Cr-2Nb. The failed Ti-48A1-2Cr-2Nb debris

subsequently transferred to the superalloy 718. In reference experiments conducted with Ti-6A1-4V against superalloy

718 under identical fretting conditions, the degree of transfer was greater for Ti-6A1-4V than for Ti-48AI-2Cr-2Nb. Wear

of Ti-48A1-2Cr-2Nb generally decreased with increasing fretting frequency. The increasing rate of oxidation at elevated

temperatures led to a drop in wear at 473 K. However, fretting wear increased as the temperature was increased from 473

to 823 K. At 723 and 823 K, oxide film disruption generated cracks, loose wear debris, and pits on the Ti-48A1-2Cr-2Nb

wear surface. Both increasing slip amplitude and increasing load tended to produce more metallic wear debris, causing

severe abrasive wear in the contacting metals.

14. SUBJECT TERMS

Materials; Ti-48AI-2Cr-2Nb; Fretting wear; Fatigue; Oxidation;

High temperature; Ni-base superalloy 718

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Unclassified

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Unclassified

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Unclassified

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20

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