FORMED PLATELET LINER

CONSTRUCTION FEASIBILITY

CONTRACT NAS 8-37456

PHASE A FINAL REPORT

September 1992

Prepared For:

National Aeronautics and Space Administration

George C. Marshall Space Flight Center

Marshall Space Flight Center, AL 35812

Prepared By:

W. a.(M_ygs /

Platelet Devi&s

Research and Engineering

Platelet Devices

Research and Engineering

Approved By:

W. M . 'B_- ffr'd_ -

Program Manager

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RPT/G0114.119 Seotember 30. 1992
TABLE OF CONTENTS

1.0 Introduction

2.0 Summary and Conclusions

3.0 Benefits Analysis

4.0 Platelet Stack Forming

5.0 Platelet Stack Joining

6.0 Fabrication Process Definition

7.0 Silver Aided Bonding

Appendix A - Platelet Design and Fabrication Processes

1

3

5

17

84

126

130

A-1

PRECEDING P:_GE P;LAHK _OT F!LtVED

_Pvoo,14._19 iii October 6.I992
Table No.

3.1

3.2

3.3

3.4

3.5

3.6

3.7

4.1

4.2

4.3

5.1

5.2

5.3

5.4

7.1

7.2

7.3

7.4

7.5

LIST OF TABLES

SSME, STBE and STME Baseline Geometry and Operating Conditions

Cycle Life Benefits - SSME

Cycle Life Benefits - STBE

Cycle Life Benefits - STME

Cycle Life Benefits - SSME With Bi-Metallic Wall

Cycle Life Benefits - STBE With Bi-Metallic Wall

Cycle Life Benefits - STBE With Nickel Liner

Regeneratively Cooled Thrust Chamber Parameters

Formed Platelet Liner Forming

Section Testing Results - ZrCu Coarse Pattern

Identified Joining Issues

Joining Parameters Investigated Using Simple/Linear Samples

Flat Joining Sample Configurations

Critical Processes For Diffusion Bond Joining

Silver Aided Bond Experiment - Taguchi Array

Factor's and Levels For Taguchi Array

Sample Processing Matrix, Bonding Post-Bond

Sample Processing Matrix, Post-Bond Age

Tensile Test Results

6

10

10

11

11

12

12

19

39

68

85

90

91

100

132

133

136

137

138

RPT/G01 I4.119 iv October 6, 1992
Figure No.

3.1

3.2

3.3

4.1

4.2

4.3

4.4

4.5

4.6

4.7

4.8

4.9

4.10

4.11

4.12

4.13

4.14

4.15

4.16

4.17

4.18

4.19

4.20

4.21

4.22

4.23

4.24

4.25

4.26

LIST OF FIGURES

Formed Platelet Liners Substantially Increase SSME Combustion 8

Chamber Thermal Margins

Formed Platelet Liners Substantially Increase STME Combustion 9

Chamber Thermal Margins

Formed Platelet Liners Have 25% Pressure Drop Savings Over 13

Conventional Milled Slot Combustor Liner

Thrust Chamber Geometric Parameters 26

Geometric Throat Station Parameters of Milled Slot Thrust Chambers 27

Superimposed on Formed Platelet Devices

40K Combustion Chamber Contour For Platelet Stack Forming 29

Single Step Forming Die 31

Two-Dimensional Forming Die 32

First Series Throat and Barrel Cross Sections of Panel Designs 34

First Series Coarse Pattern Platelet 35

Platelet Gas Side Wall 0.033 THK ZrCu 37

Two-Step Forming Process 42

OD Cracking Due to Use of Throat Springs, S/N 015 43

Removing Throat Springs From the Die Eliminated Cracking of Part SN 002 44

Tooling Modifications Were Necessary to Prevent Tearing of the Part 45

Parts Formed in 2 Steps Cracked the Close Out of the Part 46

Parts Formed in a Single Operation Remained Intact 47

Material Outside of 90 ° Chamber Section Was Removed to Study the Effect 49

on Channel Deformation

Fine Pattern Artwork Was Modified For T/R Study 50

Second Series Panel Designs T/R Ratio Studies 51

Second Iteration Panel Design 53

Second Iteration Platelet Design 54

Second Iteration Channel Design 55

Flow Data Results ZrCu Coarse Pattern Panels 58

ZrCu Fine and Stepped Patterns and Flow Results 58

Cold Flow Results ZrCu Stepped Pattern 58

Cold Flow Results Cres 304L Coarse Pattern 59

Cold Flow Results Cres 304L Fine Pattern 59

Cold Flow Results Cres 304L Stepped Pattern 59

RPT/G0114.119 V October 6, 1992
Figure No.

4.27

4.28

4.29

4.30

4.31

4.32

4.33

4.34

4.35

4.36

4.37

4.38

5.1

5.2

5.3

5.4

5.5

5.6

5.7

5.8

5.9

5.10

5.11

5.12

5.13

5.14

5.15

5.16

5.17

5.18

5.19

5.20

LIST OF FIGURES (CONT)

pa_0 

Spring Back in the Throat Section Increases With Panel Thickness 60

Results of Contour Measurements, 1st and 2nd Panel Design 61

Die Gap Varies Along the Chamber Axis 63

Second Iteration Design Showed Improved Edge Location After Forming 64

Skew of the Channel Along the Chamber Axis Increases With Part Thickness 66

Section Testing Results 67

Panel Joining Demonstration Platelet Design 74

Seam Channel Land Location Results 75

Formed Platelet Edge Deviation 3D Joining Demo Panels 77

Restrain Anneal Fixture 79

Radial Contour Comparison 80

Axial Contour Comparison 81

Task 1.4 Phase A Test Logic For Joining 86

Panel Joining Samples - Flat Samples 88

Weld Joint Configurations 92

Channel Weld Results 94

Land Weld Results 95

Photomicrographs of HIP Processed Samples 97

Comparison of As-EDM's and Hand Polished Surfaces 98

Process Flow of Diffusion Bond Joining of Formed Platelet Panels 99

Two Interfaces in the Chemically Machined Sample Achieved 103

100% Bonding

Diffusion Bond Edge Joining Process 104

Comparison of Wire EDM Processes 106

Etch Parameter Optimization Provided Complete Recast Removal 107

Initial 2D Sample Configuration 109,--

EBW Bead Dimensions 111

Sample Configuration 111

Photomicrographs of 2D Bond Samples 112

Bond Sample Radiograph 113

2D HIP Bond Samples W/Leak Test Capability 115

2D HIP Bond Sample Sections 116

Laser Welding of 3D Demo Panels 118

RPT/G0114.119 vi October 6, 1992
Figure No.

5.21

5.22

5.23

5.24

6.1

6.2

6.3

7.1

7.2

LIST OF FIGURES (CONT)

Joining Study - 3D Sample

Photomicrographs of 3D Demo SN 01 Joint, Forward End

3D Demo S/N 01 Assy - Throat Land Cross Section

Photomicrographs of Weld Sample of S/N 02 Closeout

Process Definition - 40K Liner 1/2

Process Definition - 40K Liner 2/2

Flowchart Legend

Bond Block Sample Identification

Comparison of Bond Aid Performance

119

121

122

124

127

128

129

134

139

RPT/G0114.119 vii October 6, 1992
1.0 INTRODUCTION

Environments generated in high pressure liquid rocket engines impose severe requirements

on regeneratively cooled combustor liners. Liners fabricated for use in high chamber pressures

using conventional processes suffer from limitations that can impair operational cycle life and

can adversely affect wall compatibility.

Chamber liners fabricated using formed platelet technology provide an altemative to conventional regeneratively cooled liners; an alternative that has many attractive benefits. A formed

platelet liner is made from a stacked assembly of platelets with channel features. The assembly

is diffusion bonded into a flat panel and then three-dimensionally formed into a section of a

chamber.

Platelet technology permits the liner to have very precisely controlled and thin hot gas

walls and therefore increased heat transfer efficiency. Further cooling efficiencies can be

obtained through enhanced design flexibility. These advantages translate into increased cycle

life and enhanced wall compatibility. The increased heat transfer efficiency can alternately be

used to increase engine performance or turbopump life as a result of pressure drop reductions

within the regeneratively cooled liner. Other benefits can be obtained by varying the materials of

construction within the platelet liner to enhance material compatibility with operating

environment or with adjoining components.

Manufacturing cost savings are an additional benefit of a formed platelet liner. This is

because of reduced touch labor and reduced schedule when compared to conventional methods

of manufacture.

The formed platelet technology is not only compatible with current state-of-the art combustion chamber structural support and manifolding schemes, it is also an enabling technology that

allows the use of other high performance and potentially low cost methods of construction for the

entire combustion chamber assembly. ---

The contract under which this report is submitted contains three phases. These are: Phase

A, feasibility study and technology development; Phase B, sub-scale fabrication feasibility; and

Phase C, large scale fabrication validation. This report covers the Phase A activities, which

began in December of 1988.

RPT/G0114.119 1 October 5, 1992
This contract activity was contracted by the NASA Marshall Space Flight Center under

sponsorship of the NASA Office of Aeronautics and Space Technology Earth to Orbit Propulsion

Technology Program.

The NASA/MSFC Program Manager for this program was Mr. Fred Braam. The Aerojet

Propulsion Division Program Manager was Mr. Wendel M. Burkhardt. Mr. W. A. (Bill) Hayes

was the Project Engineer and Mr. D. E. (Dave) Janke was the Lead Design Engineer. Significant

contributions were made by Ms. Sarah Tobin, the original Project Engineer and Lead Designer;

by Mr. Harry Mueggenburg, Platelet Design Section Manager; and by Mr. A. R. Scott,

Development Operations Producibility. Other key people who contributed to the success of this

program are too numerous to mention; their efforts are greatly appreciated.

RPT/GO114.119 2 October 5, 1992
2.0 SUMMARY AND CONCLUSIONS

The Phase A activities studied the feasibility of using platelet technology for the

construction of regeneratively cooled combustion chamber liners. Results of the study show that

such an approach is feasible and has many attractive benefits.

The study produced numerous technical achievements and technology demonstrations.

Included in these were:

1) Development and demonstration of liner panel forming techniques that produce

repeatable, consistent hardware. Also demonstrated were the functional characteristics of this hardware via destructive and non-destructive examinations.

2) Design techniques to allow the correlation of feature location in the formed vs. flat

panel states.

3) Application and demonstration of an APD-developed channel filling polymer that

allows forming of platelet panels with minimal internal passage deformation.

4) Analysis of the benefits obtainable through the application of formed platelet technology to regeneratively cooled combustor liners. These benefits include significant

cycle life, wall compatibility, pressure drop, and manufacturing cost and schedule

improvements over conventional technology.

5) Exploration of present, applicable platelet technology limits. Coolant channels with

15:1 aspect ratios and hot gas walls as thin as 0.008 inch were demonstrated.

6) Techniques for joining of formed platelet panels. A process in which the panel

mating edges can be diffusion bonded together to form an essentially monolithic

structure was demonstrated. This process, though successfully demonstrated, does

require further development to make it a repeatable process.

7) A study of the use of silver as a diffusion bond aid to increase the thermal conductivity of ZrCu platelet structures. The study showed that, at its current level of development, the silver aided bond system is not a viable substitute for the standard bond

system.

8) Development of a baseline plan for the fabrication of a 40K sized functional formed

platelet liner.

RPT/G0114.119 3 October 5. 1992
At the successful completion of the Phase A study a recommendation was made, and

accepted, to proceed into Phase B of the program. Phase B will demonstrate the developed

technology through the design, fabrication, and hot fire testing of a 40K combustion chamber

employing a formed platelet liner.

RPT/G0114.119 4 October 5. 1992
3.0 BENEFITS ANALYSIS

3.1 INTRODUCTION

An analysis of a Formed Platelet Combustor Liner compared to conventional milledslot liners was made to identify potential performance and cost benefits.

3.2 OBJECTIVE

Thermal, structural and cost analysis were performed comparing the Formed Platelet

Liner to the existing SSME Main Combustion Chamber (MCC), the proposed Space

Transportation Booster Engine (STBE) chamber, and the Space Transportation Main Engine

(STME) chamber. The specific objectives were to quantify the following items:

Performance benefits, including:

• Chamber cycle life improvements

• Potential chamber coolant pressure drop savings

Manufacturing benefits, including:

• Cost savings

• Schedule savings

3.3 APPROACH, PERFORMANCE BENEFITS

A thermal analysis was conducted first to establish a channel geometry for ptatelet

liners for SSME, STBE and STME. Several different geometries were studied, including

varying hot gas wall thickness, number of coolant channels and materials. The resultant

temperature profiles were then used in a structural analysis to find strains and predict the numberof cycles to failure. As the goal of this effort was to determine the relative reduction in wall

temperature and resultant cycle life improvement for preliminary designs, the predictions should

be viewed as a reference value only.

3.4 DISCUSSION, PERFORMANCE BENEFITS

The baseline SSME, STBE and STME chamber geometries and performance

characteristics are listed in Table 3.1. The total coolant flow rate was held constant for the

RPT/G0114. t 19 5 October 5, 1992
studies; pressure drop was allowed to vary. Limits on channel geometry were made to simplify

the analysis as follows:

Land width = Channel width

Channel aspect ratio (height/width) < 15

TABLE 3.1

SSME, STBE AND STME GEOMETRY BASELINE AND OPERATING CONDITIONS

Existing Geometry (1989)

Number of Channels

Channel Width, Throat (in.)

Channel Land; Throat (in.)

Channel Depth, Throat (in.)

Hot Gas Wall, Throat (in.)

Liner Material

SSME STBE STME

390 406 451

.040 .060 .050

.013 .040 .040

.113 .147 .187

.028 .032 .030

Narloy Z ZrCu ZrCu

Operating Conditions (1989)

Chamber Pressure (psia)

Recovery Temperture (°F)

hg (Btu/(in.2-sec-°F)

Coolant Bulk Temperature (°F)

Coolant Toal Pressure (psia)

Total Coolant Flow Rate (lbm/sec)

Coolant

Maximum Wall Temperature (°F)

Maximum Delta Temperature (°F)

3006 3150 2250

5925 6167 4732

0.01668 0.01170 0.0178

-254.3 -133.6 -261.7

5703 4241 2885

26.1 347.5 64.70

Hydrogen Methane Hydrogen

1200 1030 920

1436 1174 1176

Wall thicknesses evaluated vary from 0.0025 to 0.040 inch. Land/channel widths

from 0.007 to 0.025 inch were evaluated. Configurations beyond the current capability of

platelet technology were analyzed to establish performance trends.

The use of materials other than ZrCu for SSME and STBE liners was also

investigated. Materials investigated include:

RPT/G0114.119 6 October 5, 1992
SSME MCC:

ZrCu

CRES

ZrCu with a thin (0.001 or 0.002) CRES barrier platelet

STBE Liner:

ZrCu

Nickel

ZrCu with CRES barrier platelet

A parametric thermal analyses evaluated different materials and channel geometries

to obtain temperature predictions for the SSME MCC, STBE and STME chambers. Pressure

drop savings were also predicted for the STBE chamber.

The thermal analysis used an APD-developed thermal channel code to predict

maximum throat temperatures. The STBE and STME temperatures were based on predicted

chamber boundary conditions as of early 1989. The thermal conductivity values of bonded ZrCu

used were reduced approximately 11 to 20% to account for the presence of the diffusion bond

aid. The nickel and CRES thermal conductivites used were that of wrought materials, as any

bond aid used would be of a conductivity equal to or greater than the base material.

A structural analysis was conducted to determine cycle life. The approach was to

conduct a Finite Element Method (FEM) plane strain analysis on a throat cross-section.

Temperature profiles from the thermal analysis were used to determine strains at various points

in the thermal cycle of a liner. Manson-Halford low cycle fatigue curves were used to obtain Nf,

and the number of cycles to failure predicted by Nf/10.

A complete description of constraints, assumptions and analysis methodology can be

found in references 1 and 2. The predicted thermal margins and life increase for both SSME and

STME chambers are shown in Figures 3.1 and 3.2 for ZrCu platelets. Tables 3.2, 3.3 and 3.4 li_

the maximum wall temperature and resultant cycle life as a function of gas side wall thickness

and number of coolant channels.

RPT/G0114.119 7 October 5, 1992
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(.9

1400

1200

1000

800

600

4O0

0

Land Width (L) = Channel Width (W)

809 Channels -_

L = 0.020_,,,._

- 1472 Channels

L = 0.011 in.

I

0.020 0.030

Hot Gas Wall Thickness, in.

O

It-,,

z

L_

!

o_

14.

O

(/}

a)

m

O

500

400

300

200

100

0.040 0 0

! I I

Land Width (L) = Channel Width (W)

\ 1472 Channels

.011 in.

809 Channels

L -- 0.020 in. SSME

i •

0.010 0.020 0.030

Hot Gas Wall Thickness, in.

0.040

1_12-11

Figure 3.1 Formec_ Platelet Liners Substantially Increase SSME Combustion Chamber Thermal Margins
_O

1400

1200

O

21000

E 800

N 600

400

200

0

Land Width (L) = Channel Width (W)

STME

STME Throat Conditions

I [

o

o_

LL

O

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o

o

5OO

400

3OO

20O

100

0

0.010 0.020 0.030 0.040 0 0.010

Wall Thickness, inches

Land Width (L) = Channel Width (W)

1352 Channels

L = 0.007 in.

(365)'

(280)

811 Channels

L = 0.020 in.

1 I

0.020 0.030

WallThickness, inches

0.040

1.12.2.15

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TABLE 3.2

CYCLE LIFE BENEFITS- SSME

SSME Throat Conditions

ZrCu Platelets/STD Bond Aid

Gas Side

Wall No. Tmax, Delta Tmax,

Thickness, in. Channels °F °F

*0.028 390 1183 1397

0.020 809 871 1123

0.020 1470 689 942

0.020 2229 583 827

0.0135 809 754 1007

0.0075 1470 441 693

0.005 2229 265 477

*SSME Baseline

Gas Side

Wall No.

Thickness, in. Channels

*0.032 406

0.016 1122

0.016 1683

0.0145 808

0.0105 1122

0.0064 1683

*STBE Baseline

Maximum

Strain

in ./in.

0.0285

0.030

0.0186

0.0162

0.0200

0.0134

0.0116

TABLE 3.3

CYCLE LIFE BENEFITS- STBE

STBE Throat Conditions

ZrCu Platelets/STD Bond Aid

Cycles to

Failure

N._f/10

14

83

150

195

145

280

365

Maximum Cycles to

Tmax, Delta Tmax, Strain Failure

°F °F in./in. N_I 0

1004 1155 0.0212 160

639 772 0.0153 215

534 664 0.013 300

709 842 0.0167 200

555 688 0.0136 270

380 507 0.0097 500

10

RPT/G0114.119 October 5, 1992
TABLE 3.4

CYCLE LIFE BENEFITS- STME

STME Throat Conditions

ZrCu Platelets/STD Bond Aid

Gas Side Maximum Cycles to

Wall No. Tmax Delta Tmax, Strain Failure

Thickness, in. Channels °F) °F in./in. N._f/10

0.012 811 499 750 0.150 220

0.040 811 796 1050 0.0140 280

0.0072 1352 280 540 0.0106 440

0.040 1352 668 930 0.0122 365

Thermal analysis of the alternate materials show reasonable wall temperatures, as

summarized in Tables 3.5, 3.6 and 3.7. The alternate materials could provide better propellant

compatability than ZrCu. However, as a structural analysis was performed on the ZrCu

configurations only, it is not known how the cycle life of the other materials would compare.

TABLE 3.5

Gas Side

Wall

Thickness

0.020/0.002

0.020/0.001

0.010/0.002

0.010/0.001

0.010/0.001

0.005/0.002

CYCLE LIFE BENEFITS - SSME WITH BIMETALLIC WALL

SSME Throat Conditions

ZrCu/CRES 347 Gas Side Wall

Maximum Cycles to

No. Tmax, Delta Tmax, Strain Failure

Channels °F °F in./in. N f/10

2229 1127 1381 0.0286 32

2229 869 1118 0.0224 62

1470 1052 1306 0.0267 36

1470 788 1042 0.0206 73

2229 686 931 0.0182 94

2229 872 1125 0.0197 76

RPT/G0114.119

11

October 5, 1992
Gas Side

Wall

Thickness, in.

0.020/0.002

0.020/0.001

0.010/0.002

0.010/0.001

0.010/0.001

0.005/0.002

0.005/0.001

TABLE 3.6

CYCLE LIFE BENEFITS - STBE WITH BIMETALLIC WALL

STBE Throat Conditions

ZrCu Platelets/STD Bond Aid

No. Tmax, Delta Tmax, Maximum Cycles to

Channels °F °F Strain Failure

in./in. N_I 0

1683 1016 1150 0.0234 56

1683 813 944 0.0188 84

1122 973 1107 0.0224 60

1122 768 901 0.0177 94

1683 671 800 0.0156 125

1683 811 944 0.0189 83

1683 592 719 0.0139 160

Gas Side

Wall

Thickness, in.

0.016

0.008

0.0055

TABLE 3.7

CYCLE LIFE BENEFITS - STBE WITH NICKEL LINER

STBE Throat Conditions

Ni 200 Platelets

Maximum Cycles to

No. Tmax, Delta Tmax, Strain Failure

Channels °F °F in./in. N_f/10

1683 1436 1567 0.028 11

1683 988 1118 0.0168 150

1683 820 949 0.0158 250

Analyses were conducted to investigate possible savings in coolant pressure drop for

formed platelet liners. The pressure drop for various coolant channel designs was calculated

using the May 1989 STME chamber contour and operating conditions. ZrCu platelets and H2

coolant were used for analysis. Figure 3.3 compares the pressure drop for platelet liners to the

conventionally slotted liners, assuming a constant 0.030 width channel (baseline STME design)

and maximum temperature of 1000°F, 100°F below the STME baseline design. Using variable

width channels results in a pressure drop savings of up to 47% of the STME baseline value. A

constant width design was chosen for the baseline STME chamber design to simplify the

RPT/G0114.119 12 October 5, 1992
800 --

A

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600--

¢Z,

O

LCI

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L-

= 400 -- u)

u)

Q)

Ln

i,,,,

O

.Q

E 200 --

_3

J=

L)

I

200

STME (w=0.071")

@ Tw - 1100"F

ZrCuWith Silver Bonding Aid

,_ @Tw= 1000 F

Constant 0.030 Inch Channel Width

STME Design As Of 5/89

I I I

400 600 800

Number Of Coolant Channels

I I

1000 1200

F_ure 3.3. Formed Platelet Liners Have 25% Pressure Drop Savings

Over Conventional Milled Slot Combustor Liner
conventional liner fabrication. The use of variable width channel design when fabricated with a

formed platelet liner does not present any increase in fabrication cost.

3.5 APPROACH, MANUFACTURING BENEFITS

The manufacturing benefits analysis compared the cost and schedule of producing a

SSME combustor liner using formed platelet technology to the current manufacturing approach.

The cost of the support structure and manifolding are assumed identical for the two fabrication

approaches. Additional assumptions were made for analysis of the formed platelet liner:

A free-standing liner is constructed from four platelet panels.

25% manufacturing attrition of individual platelets.

25% manufacturing attrition of platelet panels.

A single step forming process would be used.

Platelet etching and plating facilities exist, thus requiring no additional capital.

Data and experience from similar Aerojet programs was used wherever applicable to

estimate costs and schedule. The cost per liner is based on manufacture of 22 units.

3.6 DISCUSSION, MANUFACTURING BENEFITS

The manufacturing costs were established from an estimate of touch labor hours for

recurring and non-recurring costs. Cost factors were applied to these hours to account for supervision, inspection and quality engineering. These cost factors, which are based upon Aerojet's

SSME Low Cost Study (NAS8-37503), are listed below:

Supervision = 1.65 * Touch labor hours * $75/hr

Inspection = 0.40 * Touch labor hours * $75/hr

Quality engineering = 1.41 * Inspection * $75/hr

calculated.

Material costs were then established, and total recurring and non-recurring costs

A summary of costs is as follows:

Non-recurring costs:

Platelet artwork

Forming tooling (design & fab)

Machining & welding fixtures

Material costs

100 hrs

760 hrs

720 hrs

$10K

14

RPT/G0114.119 October 5, 1992
Recurring costs, First unit:

Etch, stack & bond platelets

Forming

Machining & welding

Platelet Material

275 hrs

50 hrs

210 hrs

$2 K

Using the cost factors, the above costs are then broken into a first unit cost, and a cost

per unit, assuming 22 units and a 95% learning curve:

First unit cost:

Non-recurring cost

Recurring cost

$539 K

_181K

Total $720 K

For 22 units, cost per unit:

Non-recurring cost

Recurring cost

$25 K

$128 K.

Total $153 K

The present cost of an SSME MCC liner, based upon Low cost SSME studies and

Rocketdyne data, is approximately 18% of the $4.3 M cost per MCC, or $770 K. The cost of a

formed platelet liner is then 20% of the cost of a conventionally machined liner.

Fabrication time for the machining, slotting and close-out of a SSME MCC liner,

from fabrication schedules provided by NASA/MSFC, is approximately 19 months. Estimates

for the fabrication of a formed platelet liner are as follows:

Platelet etching, stacking & bonding

Platelet stack forming

Machining of formed panels

Welding of panels and HIP bonding

Total fabrication time

1.5 months

1.0 months

1.0 months

1.0 months

4.5 months

15

RPT/G0114.119 October 5, 1992
3.7 CONCLUSIONS

Combustor chambers made with conventional technologies operate with relatively

thick side walls resulting in high hot gas wall temperatures and limited cycle life. Design

improvements are difficult to make to conventionally machined channel geometry because of

tolerance control.

Substantial decreases in wall temperatures, as much as 400°F for the SSME MCC,

can be realized with an increased number of channels and thinner hot gas walls, which can be

fabricated using current platelet technology. Decreased wall temperatures result in order-ofmagnitude life cycle improvements. Using platelets, channel geometries can be tailored to

achieve 25% (STME) pressure drop savings, while still maintaining lower wall temperatures than

conventional technologies.

The cost of a formed platelet liner for the SSME is estimated to be 20% of the cost of

a conventionally machined liner. Fabrication time of a liner is reduced by two-thirds, from more

than 1.5 years to less than 5 months.

RPT/G0114.119 16

October 5, 1992
4.0 PLATELET STACK FORMING

4.1 INTRODUCTION

The platelet panel forming related tasks are described in this section. These tasks are

as follows:

1.1 Combustor Liner Sizing

1.3 Platelet Stack Forming Experiments

1.7 Panel Joining Demonstration, panel forming tasks only

1.9 Contour Forming Experiments.

Task numbers refer to contract WBS activities. The various tasks described involve

all aspects of the panel forming accomplished in Phase I, including the panel and die designs and

fabrication, panel forming and subsequent panel testing.

4.2 OBJECTIVE

The primary objective of the Platelet Stack Forming task was to establish a basic

forming process for platelet panels intended for cooled combustion chamber liners. This

included investigating various die configurations and panel designs in order to define the

behavior of complex panel forming. An additional goal was to develop a geometry prediction

technique to allow panel designs to compensate for the effect of forming on the channel

placement.

4.3 APPROACH

A three-step approach was taken to characterize platelet panel forming. The first step,

Task 1.1, was to evaluate combustor liner geometries from existing rocket engines and select the

contour to use for experimentation. Forming experiments were then performed in Tasks 1.3 and

1.9 to determine the method for forming and the tooling features required in panel and die "-

designs. The forming effects that different panel configurations have on the internal panel

geometry was also characterized in the second step. The third step, Task 1.7, was to demonstrate the feasibility of fabricating a free-standing liner by joining two panel segments.

The result of the platelet stack forming tasks was a basic characterization of how

different panel and die designs affect the forming of platelet combustor liners.

RPT/G0114.119 17 October 5.1992
4.4 TASK 1.1 COMBUSTOR LINER SIZING ANALYSIS

The first task was to determine the range of geometric forming parameters to

investigate. Parameters critical to forming were determined, and tabulated in Table 4.1 for 24

existing rocket engines combustor liners. Figure 4.1 illustrates the geometric parameters

tabulated in Table 4.1. The engines evaluated in the study included staged combustion, gas

generator and expander cycles. The engines varied in chamber pressure from 300 to 5000 psia,

and varied in thrust from about 3000 lbs to 1,500,000 lbs. Of greatest interest were the 11 rocket

engines with milled slot coolant channels. The pertinent design data from these engines include

chamber contours, wall thicknesses, and channel geometries. The remaining engines use tubes

for the coolant channels. Only the chamber contour data from these engines were used. The

table is not complete for every engine. This is due to the difficulty in obtaining some of the data

for the older rocket engine designs.

Aerojet analytical studies performed on platelet stack designs have confirmed that an

important variable in the forming process is the ratio of the thickness (t) of the platelet stack to

the smallest bend radius (R), or t/R, of the finished part. The data from Table 4.1 shows that the

smallest bend radius is usually just aft of the throat leading into the nozzle. As the t/R ratio

becomes larger, the forming process increases in difficulty.

The smallest bend radius data from Table 4.1 for engines using slotted cooling

channels is plotted in Figure 4.2 along with previous Aerojet forming experience. The ease of

forming a part increases when moving toward the upper left hand corner of the graph. The range

of bend radii and t/R ratios encountered in milled slot chamber engines vary as follows:

Lower Upper

Variable Bound Bound

Minimum Radius, in. 0.65 5.0

t/R 0.05 6.25

Other variables affecting forming include the coolant channel design, hot gas wall

thicknesses, and material of construction. The tooling design and any filler materials used in the

channels also affect formability. The most important forming issues are as follows:

18

RPT/G0114.119 October 5, 1992
TABLE 4.1

REGENERATIVELY COOLED THRUST CHAMBER PARAMETERS, SHEET 1 OF 7

:_ili _(_oc_:_i_ _n:e'ii_i!iiiill_iiiiii!iiil,i!i,!!!_ili iiiMi:il_iiiiii+_ii_iiiii_iiiiiiii_ii_+ii_iiii!iiii_i+_Ui!!ii iil i',i i':i_:iiii!i iiiiiiiiiii!S_B E iii_:ii:,!iiiiiii_i:_:_ii+iii::iliiiii:_::i!:_!i:l _::i+_iiiiiiiii!_ii_(R o ck etd y n e ) :

Pc NIM 2 (psia) 7.58 x 106 (1100) 6.89 x 10 6 (1000) 21.7x 10 6 (3150) 20.7 x 106 (300)

Thrust N (Ibf) 6.67 x 106 (1,500,000) 6.67 x 106 (1,500,000) 3.34 x 106 (750,000) 2.22 x 106 (500,000)

. : + +. ...... : ....................

Propellants Oxidizer Fuel .............. LOX/RP-1 LOX/H 2 LOXICH 4 LOXIH2

coolant : RP-1 : ............. H2 .................... ; H20r cH4 H2

,, , + .... :

Chamber Liner Mat'l Inconel X CRES 347 NARLOY-Z

................... J ......

Type Chamber Brazed Tube Brazed Tube Milled Slot Milled Slot

. . ....................................................................

L' cm(in) 74.93 (29.5) 38.1 (15.00) 35,56 (14.00)

C R 1.306 1.74 2.8 2.966

OChambe r cm(in) ................... ' ........101.6 (40i ' ......... I07.2 i42.2) .......'............. 53.34 (21.0) 45.06 (17.74)

RI cm(in) 15.875 (6.25) 22.53 (6.87)

(_! ................. 13= . ........ 10 ° 56' . ......... 30 ° _ 25 ° 25'

Ru cm(in) 15.875 (6.25) 13.09 (5.153)

DThroat cm(in) 88.9 (35) 61.23 (31.982) 31.75 (12.5) 26.18 (10.306)

_ , .......... ,.................. I ..................................... + ..........

02 6° 4' 33 ° 25 + 25'

.......... + ,, , • ........

Max. Regen Cooled Expansion Area Ratio 10:1 14:1 5:1

Gas Side Barrel cm (in) ....... .089 (0.35) .089 (.035)

Wall Throat 0.71 (.028) .071 (,028)

Thickness

Nozzle 1 (.063) .089 (.035)

Barrel 178 @ 1 3/32 OD .1 x .381 (.040 x .150) .157 x ,419 (.062 x .165)

Channel Throat .1 x .353 (.040 x .139) .1 x .335 (.040 x .132)

WxD

Nozzle " 3il 'i0':'IL'35_6"1'" OD ......................... :1 x .762 (.040 x .300) '.15 x .483 (.062 X .190)

B .............................. .239 (.094) .204 (.0802)

Land T .10 (.040) .109 (.0430)

N .251 (.099)

No Channels 178 to 3:1 300 Tubes 492 390

Formed

Platelet

Liner

t .978 (.385) .635 (.250)

t/RThroat ............. " " "-"-"" " " ......... "- ' ..................... .0616 " ....... .0485 __

Barrel _ : 2.66 _

Th'ro at 3.3

Nozzle 3.06 ._
FO

O

TABLE 4.1

REGENERATIVELY COOLED THRUST CHAMBER PARAMETERS, SHEET 2 OF 7

.................................................................................... ............................ ............................ 4:!..=....!06...,{..6.00! .............

Thrust N (Ibf) 9.96 x 105 (224,000) 9.11 x 105 (205,000) 7.56 x 105 (170,000)

Propellants Oxidizer/Fuel LOX/RP-1 LOX/RP-1 LOX/RP-1

Coolant RP-1 RP-1 RP-1

Chamber Mat'l Type "A" Ni

"Type- Chamber : Brazed Tube _ Brazed Tube

L' cm(in) 79.12 (31.15) 71.5 (28.15)

CR

DChambe r cm(in) 52.22 (20.56) 52.22 (20.56) 53.07 (20.9)

RI cm (in)

01 lO =

: = ....

Ru cm (in)

DThroat cm(in) 40.97 (16.13) 41.15 (16.2) 41.15 (16.2)

0 2 9.75°

Max. Regen Cooled Expansion Area Ratio

,, ........ = ...........

Gas Side Barrel cm (in)

Wall Throat

Thickness Nozzle i _ .102 (.040)

Barrel

Channel ............................................................................................................................................................................................................................................... Throat

WxD

Nozzle

B

Land .............. T

N

No Channels 292 292

t

tlR Throat

Formed _ Channel Aspect Ratio

Piatelet _ Barrel ........ Liner

Throat

Nozzle

Formed PiaL 1/31 07
TABLE 4.1

REGENERATIVELY COOLED THRUST CHAMBER PARAMETERS, SHEET 3 OF 7

i_ ii_i_R:ock _+t_e_+iiiiiiiiiii'ii i!iii!iiiiiiiiiiiiiiiii:ii'M?H_ii iiiiiiiiiiii!iiiiiiiii!iiiiil!i!iiiiiiii_iiiiiiiiiiilil _iii!iiiiiiii!iii iii!iiiiiiiii_iiiiiii i:_i _!_i iiii!ii ii!iiiiii_iiii!ii!ii_ i!:_ii!!!_!i!il il iii!!iiiili_(Ro c k e ld y n e)i __,

Pc N/M (psia)

Thrust N (Ibf)

Propellants Oxidizer/Fuel

Coolant

Chamber Mat°l

Type Chamber

L'

CR

3.6 x 106 (550)

1.33 x 106 (300,000)

LOXIRP-1

RP-1

Type "A" Ni

Brazed Tube

14.7 x 106 (2130) 5.4 x 106 (785) 5.4 x 106 (780)

1.07 x 106 (240,000) 1.05 x 106 (235,000) 1.02 x 106 (230,000)

Lox/H2 N204_AEROZmE50 LOX/L.2

H2 AEROZINE 50 _ H2

CU Alloy Nicro Braze/347SS CRES 347

Milled Slot Brazed Tube Brazed Tube

......... • ............ c ................................................. •_

DChambe r cm (in) 53.2 (20.95) 9.1 (3.50)

+ , , ,+,, ......

RI

{)1

Flu

DThroat

02

Max. Regen Cooled

Gas Side

Wall

Thickness

Channel

WxD

Land

No Channels

Formed

Platelet _.

Liner

cm (in) 51.3 (20.2) 46.94 (18.48)

2.57 1.72

55.32 (21.78) 46.99 (18.5)

cm (in) ....... 22.35 (8.8O)

25 ° 13.7 °

cm(in) 3.45 (1.36) 28.02 (11.03)

cm(in) 41.15 (16.2) 38.74 (15.25) 37.34 (14.7)

23 ° 4.2 °

Expansion Area Ratio 6:1

Barrel cm (in)

Throat

Nozzle

Barrel

Throat

Nozzle

: ...... : + _:

B

T

N

288 Baz'rc! 160 THT/Nozzlc 320 Barrel 360 540 Brazed

t

t/R Throat

Channel Aspect Ratio

Barrel 'l ....

Throat

Nozzle

-g

E
FO

FO

TABLE 4.1

REGENERATIVELY COOLED THRUST CHAMBER PARAMETERS, SHEET 4 OF 7

il;i!iiii!ii!iiiiiii!_i_!!iiiiii!!iiiiiii_::iiiiiii!!iiiiii;iiiiiiiiiiiii _!_i_ii_ii_i_!i_ii_iiii_i_:_ii_i_i_i_i_i_ii_i_ii_iii_ii_ii_ii_!_i_i_iMSFC_K_i_i_i_:_ iAer0jet/Proposed

Pc N/M (psia) 4.0 x 106 (585)

Thrust N (Ibf) 6.67 x 105 (150,000)

Propellants Oxidizer/Fuel

Coolant

Chamber Mat'l

Type Chamber Brazed Tube Brazed Tube

L' cm (in)

C R 2.0 1.77

4.8 X 106 (700) 20.7 X 10 6 (3000) 20.7 X 106 (3000)

3.56 X 105 (80,000) 1.78 X 105 (40,000)

LOX/RP-1 LOX/H2

RP-i H2 ...........

CRES 347 NARLOY-Z

1.76 x lO5 (4o,ooo)

LOXIRP-1 LOX/LH 2

..... = ............................... ........ :..

RP-1 H2

CRES 347 ZR-Cu

DChambe 31.12 (12.25) r cm (in) 55.3 (21.78)

RI cm (in)

01 15"

Ru cm (in)

DThroat cm (in) 38.74 (15.25)

02

Milled Slot

35.56 (14.00)

2.924

14.38 (5.660)

7.13 (2.808)

25 ° 25'

13.09 (5.153)

Formed Platelet

2.924

14.38 (5.660)

4.20 (1.655)

30 °

4.20 (1.655)

Max. Regen Cooled Expansion Area Ratio

Gas Side

Wall

Thickness

Channel

WxD

23.42 (9.22) 6.41 (3.31) 6.42 (3.31)

17.5 = 25 ° 25' 30 °

5:1

.089 (.035)

.071 (.028)

Land

No Channels

Barrel cm (in)

Throat

Nozzle

Barrel

Throat

Nozzle

B

T

Formed

Platelet _.

Liner

N

250

t

t/R Throat

Channel Aspect Ratio

Barrel i

Throat

.089 (.035)

.157 x .419 (.062 x .165)

.102 x .335 (.040 x .132)

.157 X .483 (.062 x .190)

•1996 1,07861

.1082 (.0426)

128

.635 (.250) .635

.151

2.66

3.3

(.250)

.151

Nozzle 3.06 !

O
L_

TABLE 4.1

REGENERATIVELY COOLED THRUST CHAMBER PARAMETERS, SHEET 5 OF 7

iiii!i iB:_ i _2:0 i I iiiii!ii iAGE:NA:iiiii!Tii::iii!iil i::ii iiiiiii_i:.i RLII_II0:._ :

Pc NIM (psia) 20.7 x 106 (3000) 3.4 x 106 (500) 2,1 x 106 (300)

6.67 x 104 (15,000)

LOXILH2

H2

CRES 347

Brazed Tube

50.8 (20)

Thrust N (Ibf) 1.33 x 105 (30,000) 7.12 x 104 (16,000)

Propellants OxidizerFuel LOXILH 2 IRFNA/UDMH

Coolant H2 ............ !RFNA

Chamber Mat'l OFHC Aluminum

Type Chamber Milled Slot Drilled

L' cm (in) 69.72 (23.54)

CR 6.95 5.34 2.95

DChambe r cm(in) 16.2 (7.17) 27.41 (10.79) 26.06 (10.26)

RI cm (in) 11.68 (4.6)

01 45 ° 11 =

Ru cm (in) 13.46 (5.3)

Di.hroa t cm(in) 6.9 (2.72) 11.66 (4.67) 15.18 (5.975)

02 15° 25"7° 32"05°

Max. Regen Cooled Expansion Area Ratio 13:1

Gas Side B;zrrel cm !in! ........................ .25 !.098} ...................................

Wall Throat .1 (.0394)

Thickness Nozzle .3 (.118)

Barrel .370 x .36 (.146 x .142)

Channel ......................................................................................................................................................................................................................................................... Throat .12 x .21 (.047 x .083) WxD

Nozzle .38 x .35 (.150 x .138)

B

Land ................................

T .128 (.0504)

N

No Channels 90 360

.699 .275

t/R Throat .202

Formed _: Channel Aspect Ratio .........................

• _ _ :

Platelet _ I_arrel .97 Liner

Throat 1.77

Nozzle .92

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Cq
o_

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Face

L

I

I

I

I

I

---_-

I

I

I

I

I

Dc /

u= "/ _ _

_r

log 88.388

Dc = Chamber L' = Chamber Length

D T = Throat Diameter

R I = Throat Inlet Radius

R U = Upstream Throat Radius

e_ = Convergent Angle

02 = Divergent Angle

Figure 4.1. Thrust Chamber Geometric Parameters
t_3

"--3

15.0

n."

qD

ca 10.0

nqO

r-"

O)

m

5.0

3.0

1.0

Figure 4.2

cm, (in.)

7.0

6.0-

5.0

4.0

3.0

2.0

1.0

[T]750K

(_) ATC 2D Forming

Experience

ITISSME

(_) Radome El Rocket Engine Data

' _+%_Easler

- E]OMS

Monopropellant_ .... Injector

vNlaCk:I(_) [._-IPrat eld_]4OME

_Nl:k:l (_ Rad o m_e,_.Tra_nBt03 _ 0 (_) HED,

Nickel Vane

(_)HEDI (_)

ITI OTV

E]XLR-132

i i I a i

.1 .2 .3 .4 .5

Liner Wall Thickness _ _ (inches)

Bend Radius - R (inches)

Geometric Throat Station Parameters of Milled Slot Thrust Chambers Superimposed on Formed

Platelet Devices
i I

Gas side wall thickness

Channel geometry

Channel width

Channel depth

Land width

Panel land geometry

Platelet stack thickness vs. minimum bend radius

Secondary bend radii

Forming die design

Channel filler material

Metal movement characteristics - prediction techniques

Channel geometry changes along chamber axis

Platelet panel material

Chamber section arc-segment (number of panels per liner)

A comprehensive evaluation investigating all variables was not possible within

program constraints. Simple coupon experiments were considered as a means of evaluating

some forming parameters, such as t/R ratios. However, because simple coupons could not

reproduce the effects of forming panels with internal geometries into complex three-dimensional

shapes, the simple coupon experiments were rejected. The effort was focused on forming fully

three dimensional panels complete with coolant channels.

The decision was made to narrow the investigation to a single die contour and several

panel designs. The platelets within the panels could be re-arranged to provide different wall

thickness and channel geometries, as well as different panel thicknesses.

The contour selected for the die set and panel design, shown in Figure 4.3, can be

used at the Marshall Space Flight Center 40K test facility. This contour was a simplified version

of previous 40K contours. The die contour was symmetrical about the throat plane. A non- ,--

symmetrical contour complicates the die design, platelet panel design, and the actual panel

forming.

4.5 TASK 1.3 PLATELET STACK FORMING EXPERIMENTS

The basic process for forming panels was established in this task. Two forming dies

were designed and fabricated. Two series of platelet panels were designed, fabricated and

formed.

RPT/G0114.119 28 October 5, 1992
i 1.655 R

a

2.830 R

Figure 4.3. 40K Combustion Chamber Contour for Platelet Stack Forming
4.5.1 Forming Die Design

The first task performed in establishing a die design was to look at similar

experiences in industry. Although a large variety of textbooks and articles on forming processes

exist, little information could be found on forming panels with internal passages into threedimensional shapes. The best reference material was found at Aerojet, since we have had

previous experience forming "porous" platelet structures, such as the Radome and the HEDI

forebody, into simple two-dimensional shapes.

The original forming tool design offered several options for panel forming

methods. The first method was a single step process, taking the flat bonded panel to the formed

condition with one movement of the die. The single step forming die is shown in Figure 4.4.

The advantages of single-step forming were that only one die set is required, and no additional

processing is required between forming steps that may require removal and replacement of

channel filler material.

A two-step forming process was devised to provide constant support to the

throat section during forming. The first step uses another die, shown in Figure 4.5, which allows

only two-dimensional (2-D) forming of the panel to take place. Tooling pins hold a panel at the

throat plane and the first point of contact for the punch is the throat. The barrel and nozzle ends

of the panel are allowed to move toward the throat.

The second step is to complete the forming to the three-dimensional shape

with the same die used for the one step forming process. The two-step process did not produce

acceptable panels, as will be discussed later. Both forming processes were intended to restrain

the panel outer edges by using spring-loaded pressure plates at the panel sides. This restrained

outer edge was intended to prevent wrinkling of the hot-gas wall.

4.5.2 First Series Platelet Panel Design

Three platelet stacks designs and two different materials were established for

the first series of forming experiments. The designs included a coarse and fine channel pattern,

and a stepped fine pattern with changing channel depths. All three designs were nominally 0.250

inch thick, and made from ZrCu and 304L stainless steel. Thus several panel-design-related

forming issues could be evaluated with the first series designs:

Channel geometry, channel widths

Channel geometry, channel depths

RPT/G0114.119 30 October 5, 1992
ORIGINAL PAGE

8LACK AND WHITE PHOTOGRAPFi

31
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32
Changing channel geometry

Platelet panel materials

Twenty-five different platelet designs were used to make the panels. Key

design features of the panels were the channel widths, channel manifolding, and tabs across the

channels. Additional panel features included channels in the panel located outside the finished

part, a grid pattern on both sides of the panel, and tooling holes.

The coarse pattern design had 32 channels in a panel (128 channels per

combustion chamber), and a 0.033 inch hot gas wall. Each panel was one quarter, or 90 °

segment of a liner. The fine pattern and the stepped channel designs had 62 channels per panel

with a 0.012 hot gas wall. Cross-sections of the channels are illustrated in Figure 4.6. A plan

view of a coarse pattern platelet is shown in Figure 4.7. The minimum channel widths and land

widths were based on previous Aerojet platelet experience; 0.020 inch lands and channels had

been used successfully in other designs.

The coolant channels were manifolded into groups to simplify water flow

testing. The coarse pattern grouped the channels for manifolding in sets of three. This allowed

for flowing each set of channels separately, providing valuable data on flow distribution across

the panel. Manifolds for the fine and stepped channel designs fed five channels each. The inlet

of the manifolds alternated from the forward to the aft end in adjacent channel sets, allowing

space for flow tooling to seal against the panel.

Because individual platelets required handling during the fabrication process

and there were many long, small lands, tabs were placed about every two inches along the

channel. The tabs, which were approximately one-half the thickness of the platelet, connected

the lands together, prevented land bending and distortion during handling of the individual

platelets. While tabs in the experimental panels are often aligned platelet to platelet, an operative

chamber would stagger tabs to minimize pressure drop. Tabs have been used successfully in

similar platelet designs including Radome. Tabs may even be beneficial to the design; i.e.,

thermal analysis indicates that correct placement of tabs may enhance local heat transfer by

affecting coolant velocities.

Additional channels are placed in the panel outboard of the final part shape.

The extra channels provided a uniform mass density throughout the part, in an attempt to prevent

excess stretching in the throat. It was thought that these channels would also ensure uniform

deformation across the platelet stack, as a restraining force was to be applied to the sides of the

panel during forming.

33

RPT/G0114.119 .. October 5, 1992
.0589

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First Series Throat and Barrel Cross Sections of Panel Designs

34
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A grid pattern was placed onto the outer surface of the outer platelets of each

panel, as shown in Figure 4.8, to allow measurement of metal movement on the panel. The grid

was etched less than 0.003 deep and did not affect the forming process. The grid pattern is used

on experimental panels only; operational panels will have smooth hot gas walls and close-out

surfaces.

The platelet design also included tooling holes for stacking and forming. The

two holes at the throat were to be used during the first forming operation and the slots along the

chamber axis were used during the final contouring.

4.5.3 Channel Filler Material

An objective of the forming task was to evaluate the need for a filler material

in the channels to prevent land deformation during forming. The following filler materials were

considered:

Fine-Grain Sand

"Sera-Bend"

Paraffin

"Rigid-Ax" wax

Aerojet developed, proprietary polymer

After evaluating the candidate materials for possible channel contamination,

previous experiences, and ease of use, the Aerojet polymer was selected. The material is water

soluble with a melting point of 140°F, thus hot water can be used for removal. The polymer is

also fluorescent, meaning illumination by blackiight can be used to verify complete removal.

Panels were formed both with and without the polymer to evaluate its effectiveness.

4.5.4 First Series Panel Fabrication

Sixteen ZrCu coarse-pattern test panels were bonded, of which thirteen were

subjected to bond densification and aging in a HIP furnace in order to increase the material

structural properties. The three panels not HIP processed were used to evaluate the necessity for

the process. The coarse panels were 0.240 inch thick, not 0.250 inch thick as planned due to a

close-out platelet inadvertently omitted during platelet stacking. Six ZrCu fine pattern panels

and four ZrCu stepped channel panels were bonded and HIP densified and aged. Due to material

availability, the stepped channel design used 0.008 instead of 0.010 inch thick platelets. The

RPTIG0114.119 36

October 5. 1992
no-Jz )io!ql ggO" IleM eP!S seo leleleld "8"17eJn6!=l L

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thirty 0.008 inch platelets used in place of the twenty-four 0.010 inch platelets appeared not to

have affected the outcome of the experiment.

Thirteen CRES 304L panels were bonded and HIP densified. Four panels of

each of the coarse, fine, and stepped pattern design were fabricated. One additional coarse

pattern panel, 1204190-69 was fabricated. The panel had the platelet tabs between the quarter

liner and frame in the converging and diverging sections removed. The tabs were removed to

compare the effect of tabs on channel deformation during forming.

4.5.5 First Series Forming Experiments

4.5.5.1 Introduction

The forming experiments began with the forming of four solid copper

panels to proof the tooling. Coarse pattem ZrCu panels were then used to evaluate the one-step

and two step processes. The one step forming process was preferred because it was believed the

liner was workhardened after the first forming operation of the two step process causing the

second forming operation to be more difficult and resulting in tearing of the closeout wall near

both axial panel edges. After selecting the one-step forming process using no restraining springs,

modifications to the panels were found necessary to achieve repeatable panel throat location.

Once the forming process and required panel tooling features were established, panels of various

thicknesses and channel designs were then formed to evaluate the effects of forming various

panel designs. Water cold flows of panels before and after forming were also performed, as well

as sectioning to look at channel deformations. Results of the forming experiments are

summarized in Table 4.2.

4.5.5.2 Tooling Proof

The first forming took place with four 0.250 inch thick solid OFHC copper

plates. Both forming processes were performed, proofing both the 2D and the 3D die sets. The

forming results are listed in Table 4.2. Three plates were formed using the single step procedure,

all three exhibited undesirable coining in the throat area. One panel was formed with the twostep procedure, and no coining was visible in the throat area.

4.5.5.3 Die and Forming Process Evaluation

Coarse pattern ZrCu panels were then formed to evaluate the forming procedure. The first two panels formed, S/N 015 and S/N 002, were formed with the two-step

RPT/G0114.119 3 8 October 5. 1992
Hot Gas

Panel Part Channel Design Wall

S/N Number Material Pattern Number Thickness

DIE VERIFICATION PANELS

01

O2

03

04

FIRST

001

002

0O3

0O4

005

0O6

O07

0O8

009

010

011

012

013

014

015

016

SECOND

017

018

019

O20

021

022

023

024

025

026

027

028

029

030

031

032

033

034

035

036

037

O38

039

TABLE 4.2

Formed Platolot Liner Forming Summary

Stack Post- Leak Test Cold Flow

Height Bond HIP Flat 2-D 3-D Flat 2-D 3-D Filler

OFNC None Solid Plate w/ Grid 0.250

OFHC None Solid Plate w/ Grid 0.250

OEHC None Solid Plate w/ Grid 0.250

OFRC None Solid Plate w/ Grid 0.250

SERIES FORMING EXPERIMENTS

1204190-9 ZrCu Coarse 1 0.033 0.244 NO

1204190-9 ZrCu Coarse 1 0.033 0.244 Yes _

1204190-9 ZrCu Coarse i.i 0.033 0.242 Yes

1204190-9 ZrCu Coarse 1 0.033 0.243 Yes

1204190-9 ZrCu Coarse i.i 0.033 0.242 Yes

1204190-9 ZrCu Coarme 1 0.033 0.242 Yes

1204190T9 ZrCu Coarse 1 0.033 0.242 No

1204190-9 ZrCu Coarse 1 0.033 0.242 Yes

1204190-9 ZrCu Coarse I.I 0.033 0.242 Yes

1204190-9 ZrCu Coarse 1 0.033 0.242 Yes

1204190-9 ZrCu Coarse 1 0.033 0.242 Yes

1204190-9 ZrCu Coarse 1 0.033 N/A Yes

1204190-9 ZrCu Coarse 1 0.033 N/A No

1204190-9 ZrCu Coarse 1 0.033 0.242 Yes

1204190-9 ZrCu Coarse 1 0.033 0.242 Yes

1204190-9 ZrCu Coarse 1 0.033 0.244 Yes

SERIES FORMING EXPERIMENTS

1204190-19 ZrCu Fine 1 0.012 0_254 Yes

1204190-19 ZrCu Fine i.i 0.012 0.254 Yes

1204190-19 ZrCu Fine I.I 0.012 0.255 Yes

1204190-19 ZrCu Fine 1 0.012 N/A Yes

1204190-19 ZrCu Fine i.i 0.012 0.254 Yes

1204190-19 ZrCu Fine 1 0.012 N/A Yes

1204190-29 ZrCu Stepped i.i 0.012 0.256 Yes

1204190-29 ZrCu Stepped I.I 0.012 0.255 Yes

1204190-29 ZrCu Stepped 1 0.012 N/A Yes

1204190-29 ZrCu Stepped 1 0.012 0.255 Yes

1204190-39 CRES 304L Coarse i.i 0.030 0.250 Yes

1204190-39 CRES 304L Coarse i.i 0.030 0.250 Yes

1204190-39 CRES 304L Coarse i.i 0.030 N/A Yes

1204190-39 CRES 304L Coarse I.i 0.030 N/A Yes

1204190-49 CRES 304L Fine I.I 0.010 0.250 Yes

1204190-49 CRES 304L Fine I.i 0.010 0.251 Yes

_1204190-49 CRES 304L Fine i.i 0.010 N/A Yes

1204190-49 CRES 304L Fine i.i 0.010 N/A Yes

1204190-59 CRES 304L Stepped I.i 0.010 0.250 Yes

1204190-59 CRES 304L Stepped i.i 0.010 0.250 Yes

1204190-59 CRES 304L Stepped 1.1 0.010 N/A Yes

1204198-59 CRES 304L Stepped i.i 0.010 N/A Yes

1204190-69 CRES 304L Coarse i.I 0.030 0.250 Yes

Springs Forming 3-D Die

(3-D) Steps Used

Yes 1 Org 1-Step

Yes 1 Org 1-Step

Yes I Org 1-Step

Yes 2 Org 2D-3D

Y Y N Y Y N Y N 2 MOd II

Y N N Y N N Y/N * Y 2 Org 2D-3D

Y N N Y N N Y N 1 Mod II

Y Y N Y Y N Y Y 2 Mod II

Y Y Y Y Y N i Mod II

Y Y Y Y Y N 1 Mod II

Y - Y Y - Y N N 1 Mod II

Y Y N Y ¥ N Y N 2 Mod II

Y - N Y N Y N 1 0rg 3D

L - N N N Y N 1 Mod II

Y - Y Y - Y Y N 1 Mod II

Y Y R Y Y N R 2 -

y ..... y _ _

L - N N - N Y Y 1 Mod II

Y N N Y N N N Y 2 Org 2D-3D

Y N N Y N N Y Y 2 Mod I

Y - N Y - N Y N 1 Mod II

Y - N Y - N Y N 1 Org 3D

Y - Y Y - Y Y N 1 Mod II

Y Y - - N - -

Y - N Y - N N N 1 Mod II

N N ....

Y Y Y - Y Y N 1 Mod II

Y N Y - N Y N 1 Mod II

L - N - N -

Y N Y N Y N 1 Mod II

Y Y Y Y Y R i Mod II

Y N Y N Y N 1 Mod II

N N N - -

N N - N - - -

Y N Y N Y N 1 Mod II

Y Y Y Y Y N 1 Mod II

N N N . -

N N N - -

Y N Y N Y N 1 Mod II

Y N Y N Y N 1 Mod II

N N N -

N - N - N - - -

Y N Y N Y N 1 Mod II

Comments

Coining in Throat

Coining in Throat

Coining in Throat

No throat coining

Ripped at panel perimeter

.010 slip sheet tore and wrinkled, damaged part

Spl_t close-out down centerline, sectioned

EXCess channels removed before forming, improved channel tip

NO Tearing or cracking

Sectioned

Split close-out down centerline, sectioned

No Tearing or cracking, sectionned

Forming not completed

Sectioned to verify filling process

No Tearing or cracking

Ripped at panel perimeter, cracks on O.D.

Ripped at panel perimeter

Ripped at perimeter of part

Excess channels removed before forming

Not formed

Damaged during fabrication

Excess channels removed before forming

Reformed in original 3D die

Not formed

Ripped at perimeter of part

Not Formed

Not Formed

Not Formed

Not Formed

Not Formed

Not Formed

Tabs removed from conv. & div. sections

39

FOLDOUT FRAME c._ ,

FOLDOUTFRAME /"
TABLE 4.2

Formed Platelet Liner Forming Summary

(Cont.)

Hot Gas

Panel Part Channel Design Wall Stack Post- Leak Test Cold Flow springs Forming 3-D Die

S/N Number Material Pattern Number Thickness Height Bond NIP Flat 2-D 3-D Flat 2-D 3-D Filler (3-D) Steps Used

040 1204435-19 ZrCu Fine

041 1204435-19 ZrCu Fine

042 1204435-19 ZrCu Fine

043 1204435-9 ZrCu Fi_e

044 1204435-9 ZrCu Fine

045 1204435-9 ZrCu Fine

046 1204796-9 ZrCu Fine

047 1204796-9 ZrCu Fine

048 1204796-9 ZrCu Fine

049 1204796-9 ZrCu Fine

050 1204796-9 ZrCu Fine

051 1204796-9 ZrCu Fine

3-D JOINING DEMO

052 1206530-9 ZrCu Fine

053 1206530-9 ZrCu Fine

054 1206530-9 ZrCu Fine

055 1206530-9 ZrCu Fine

056 1206530-9 ZrCu Fine

097 1206530-9 ZrCu Fine

058 1206530-9 ZrCu Fine

059 1206530-9 ZrCu Fine

N N Y - Y ¥ N 1

1.2 0.012 0.142 Yes "N N Y - Y Y N 1

1.2 0.012 _142 Yes N N Y - Y Y N 1

1.2 0.012 0.372 Yes N N Y - Y Y N 1

1.2 0.012 0.372 Yes N N Y - Y Y N 1

1.2 0.012 0.372 Yes N N Y - Y Y N 1

2 0.008 0.262 Yes Y - N Y - Y Y N l

2 0.008 0.262 Yes Y N Y - Y Y N 1

2 0.008 0.262 Yes Y N Y - Y Y N 1

2 0.008 0.262 Yes Y - N Y - Y Y N 1

2 0.008 0.262 Yes Y - N Y - Y Y N 1

2 0.008 0.262 Yes Y - N Y - Y Y N 1

1.2 0.012 0.142 Yes

Comments

2.1 0.008 0.258 Yes

2.1 0.008 0.257 Yes

2.1 0.008 0.297 Yes

2.1 0.008 0.257 Yes

2.1 0.008 0.257 Yes

2.1 0.008 0.257 Yes

2.1 0.008 0.257 Yes

2.1 0.008 0.257 Yes

MOO III/Shim t/R Study

MOD III/Shim t/R Study

MOD III/Shim t/R Study

MOD IIl/ 3/8 t/R Study

MOD III/ 3/8 t/R Study

MOD III/ 3/8 t/R Study

MOD III 3-D Joining Attempt

MOD III 3-D Joining Attempt

MOD III 3-D Joining Attempt

MOD III 3-D Joining Attempt

MOD III 3-D Joining Attempt

MOD IIl 3-D Joining Attempt

Y - N Y - Y Y N 1

Y - N Y - Y Y N 1

Y - N Y - Y Y N 1

Y - N Y - Y Y N 1

Y - N Y - Y Y N 1

Y - N Y - Y Y N 1

Y N Y - Y Y N 1

Y N Y - Y Y N 1

MOD III

MOD III

MOD III

MOD IIl

MOD III

MOD Ill

MOD III

MOD IIl

Panel Joining Assembly No 1

Panel Joining Assembly No 2

Panel Joining Assembly No 2

Panel Joining Assembly No i

4O
r

process, illustrated in Figure 4.9, in the as-designed tooling. Panel S/N 015, shown in Figure

4.10, cracked on the close-out wall of the part at the edge of a quarter panel chamber section and

tore at the perimeter of the part in the throat area during the final contouring operation. The part

was held around the entire perimeter with spring-loaded pads in the die. To eliminate the

cracking on the O.D. of the part, the springs were removed from the throat area for the next test

panel. Panel S/N 002 is shown in Figure 4.11. There is no cracking of the part within the

useable 90 degree sector but the part still tore in the throat region.

To correct the tearing at the edge of the parts the tooling was modified.

Figure 4.12 illustrates the rework of the die. The tooling modification was evaluated by forming

ZrCu panel S/N 016 using the two-step process. This part cracked in the same area as the

previous parts, indicating that further modification was required.

Two ZrCu panels were formed in the single step process to evaluate the

second die modification. Panel S/N 014 was formed with the restraining springs and panel S/N

010 was formed without springs in the die set. Both panels formed without any tearing or

cracking of the part indicating that the dies were satisfactory for continued forming experiments.

Three more ZrCu panels were formed to evaluate the two-step versus the

one-step processes, and the use of restraining springs. Panels S/N 004 and S/N 008 were formed

in the two-step process without springs. Both panels split the channel close-out wall down the

centerline of the part as shown in Figure 4.13. Panel S/N 006 was successfully formed in one

step without any tearing or cracking as shown in Figure 4.14.

After evaluating the panels formed to date, the single step forming process

with no springs was selected as the superior process. Panels formed in 2 steps had repeatedly

cracked the channel close-out wall. Use of springs to restrain the panels also caused close-out

wall cracking. Channel deformation studies showed that panels formed in a single step resulted

in channels that were more true to the desired contour than with panels formed in two steps.

Measurements of channel 'tip' are discussed in Section 4.5.7.6.

4.5.5.4 Panel Modifications

Inspection of parts formed with extra material around the perimeter show

that the outside channel, which was designed to be radial, is slightly skewed from radial. In

order to investigate the effect of excess material outboard of the last channel, a ZrCu coarse

41

RPT/G0114.1 It., October 5, 1992
ORIGINAL PAGE

8LACK AND WHITE PH.O*t'OGRA!-'Y*

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BLACK AN_ Wi-ii _E. • ,.-,,3__._,,_APH

Tearing at

the Perimeter

Figure4.10 OD Cracking Due to Use of Throat Springs S/N 015

43
Figure 4.11. Removing Throat Springs From the Die Eliminated

Cracking of Part SN 002

44
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Cracks

Figure 4.13. Parts Formed in 2 Steps Cracked the Close Out of the Part

46
_oe]ul pau!euJal:] uo!_eJadO allSu!s e u! pauJJo.-I sued t, L't, aJn6!:!
pattern panel, S/N 005 was machined to remove the excess material as shown in Figure 4.15.

The panel was successfully formed and found to have less channel skewing.

Four more panels were formed to further evaluate the modified panel

design. Two panels, fine pattern S/N 017 and stepped pattern S/N 026 were formed as designed.

Both parts ripped on the hot gas wall at the perimeter of the part. Two additional panels, fine

pattern S/N 019 and stepped pattern S/N 023 were machined to remove the excess material.

Both machined panels were successfully formed, which verified that the excess material is not

required for forming.

4.5.5.5 Forming Different Panel Designs

Forming experiments continued to evaluate the effects of panel design on

the formed panel. The three panel designs in ZrCu and CRES 304L were formed in the modified

(excess material removed) form using the one-step forming process with the modified 3-D die.

Panels were formed with and without polymer, and with and without tabs. Many Panels were

leak tested and water flowed both before and after forming. The results of the flow tests and

forming is presented in section 4.5.7.4. Several panels were sectioned to evaluate internal

deformations and platelet bond quality.

4.5.5.6 Die Modification III

Inspection of the grid pattern on the First Series Panels revealed a shift in

the location of the throat of the channel pattern from the flat to the formed shape by 0.050 to

0.100 inch. Tooling pins were added to the female die half at the throat plane. The pins engaged

with slots on the panel, helping to maintain throat alignment.

4.5.6 Second Series Forming Experiments

Panels of a modified original design were fabricated with different thicknesses to evaluate t/R ratios. An iteration of the first design was also made, in order to evaluate'-"

the effect of throat alignment pins.

Six modified original design fine pattern panels were fabricated in two different thicknesses. Three 0.142 inch thick panels and three 0.372 inch thick panels were made with

the configuration shown in Figures 4.16 and 4.17. The channel aspect ratio for the thick panel

was 15.5. A new female forming die half was made to accommodate the 0.372 inch panel. The

48

RPT/GII114.119 October 5, 1992
1

-----___-

1- !

[]

O

O

O

O

Figure 4.t5. Material Outside of 90° Chamber Section Was Removed to Study the

Effect on Chamber Deformation
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0.142 inch panels were mated to a 0.125 inch thick stainless steel shim and formed in the modified 3-D die with 0.250 opening.

A new panel design was made which was an iteration of the first fine-pattem

design. This panel was the first attempt to take the as-formed location of the outer channel and

re-position the channel on the flat panel design, such that when formed, the channel lies along

the 90 degree edge of the part. The contours of a formed fine-pattern panel were measured with

the Coordinate Measuring Machine (CMM) measuring machine. This data was put in a CAD

database by the machine.

The grid pattern on the hot gas wall surface, which locates the outer channel,

was then measured with the Optical Gaging Products (OGP) CMM. The OGP optically

measured the location of the intersection of the grid pattern, and the data entered manually into

the CAD database. The two pieces of data were then overlaid to find the three-dimensional

location of the channel, and the distance from the 90 degree edge. The location of the new

channel on a flat panel was then adjusted by this distance. The remaining channels were evenly

spaced between the two outer channels.

The new panel also incorporated an expendable forming frame as shown in

Figure 4.18. The frame is separated from the panel by a slot, to prevent channel deformations. A

slot was included in each frame at the throat. Tooling pins on the die set engaged in the slot to

help maintain alignment of the panel throat to the die throat. The tooling pins were added to the

die as die Modification III. Channel layout and cross-sections are shown in Figures 4.19 and

4.20.

The second series panels were formed using the one-step forming process.

Results of forming the thick and thin panels, as well as the remaining panels is presented in the

Formed Panel Evaluation section.

4.5.7 Formed Panel Evaluations

4.5.7.1 Introduction

Numerous evaluation methods were used to analyze the formed panels.

The evaluations were used to select the forming procedures and panel designs for best results.

The methods are as follows:

RPT/G0114.1 I9 52 October 5. 1992
L_3

+

D

Tooling

Pin Slot

_- Forming Frame

.100

II 4 Places

+

Separation

Slot

Figure 4.18. Second Iteration Panel Design
90°

Chamber

Section

+

Throat

Alignment

SIot

-- .100 Constant

Land

+

I

90 °

Chamber

.025

Thru Etch

Section

I

I

I

I

I

I

t_

Figure 4.19. Second Iteration Platelet Design
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Visual Examination

Inter-Channel Leak Check

Water Flow (Kw)

Flat Panel

Formed Panel

Dimensional Inspection

Contour

Grid Pattern

Sectioning

Metallographic Exam

Measurement

X-Ray

Ultrasonic

Eddy-Current

4.5.7.2 Visual Examination

Visual examination of panels after forming revealed the relative success or

problems associated with a given forming process. Cracking of close-out walls, as shown in

Figure 4.10, provided the basis for die and panel modifications, and showed that single step

forming superior is to the two-step method.

4.5.7.3 Leak Check

Most panels were inter-channel leak checked as flat panels. The panels

were leak checked between the groups of channels, a group of three course pattern channels or

five fine pattern channels. If a panel exhibited gross leakage, it would have been scrapped. No

panels exhibited gross leakage.

A small amount of interchannel leakage could be tolerated in a functional'-

panel. Three flat panels out of 43 indicated only a trace amount of leakage. The leakage was

attributed to scratches on the platelets. Some of the early panels formed were also leak checked

after forming. A leak after forming would indicate poor bond quality or tearing of the lands due

to forming. No leaks were found in any formed panel.

RPT/G0114.119 56 October 5, 1992
4.5.7.4 Water Flow Testing

Two panels of each design were water flow tested. Water flow data of both

fiat and formed panels was used to compare the effect of panels formed with and without filler,

as well as the channel deformation from forming. Because the channels were manifolded in

groups, 5 for the fine pattern and 3 for the coarse pattern, individual channel flow Variations are

'averaged' by the flows of adjacent channels. Flow results are shown in Figures 4.21 thru 4.26.

The results of flow testing show that forming does not adversely affect the

flow characteristics of the platelet panels. The changes in mass flow rate are minimal from flat

panel to formed panel. Changes in flow across formed panels previously filled with polymer

were approximately 2% for coarse and fine pattern ZrCu panels. CRES 304L panels exhibited

about 3% change in flow across the panel. Panels formed without polymer filler had mass flow

variations of about 10%, which showed the benefits of using a channel filler. These flow rate

variations are consistant with OME chamber data (a milled slot configuration), which also

approached in the 10% range.

Cold flow results show that 3D forming of the platelet panels does not significantly affect the flow characteristics of the part. Because of the part to part repeatability

between panels of the same design, any change in flow rate can be predicted and designed for.

Mass flow distribution across the panel can be controlled by using the polymer filler material.

4.5.7.5 Dimensional Inspections

The formed panels were inspected with a Coord-Ax Coordinate Measuring

Machine (CMM) and an Optical Gaging Products (OGP) CMM. The Coord-Ax touches the

panel with a small diameter ball at pre-programmed locations, and returns the actual X, Y and Z

coordinates of the locations to a CAD database. The OGP was used to measure optically the

cross-grid locations of the grid pattern, giving their X and Y coordinates. The dimensional data

was used to evaluate the contour, seam channel and throat locations of the formed panels. ....

The contour of the formed panels was measured using the Coord-Ax CMM.

The inspections showed that cold forming of panels with net-shaped dies does not result in the

desired contour, due to springback. The springback increases as the panel thickness increases, as

shown in Figure 4.27.

The results of the contour measurements are illustrated in Figure 4.28. The

data shows that the barrel radius was very close to the desired radius of 2.830 inches for all panel

57

RPT/G0114.I 19 October 5, 1992
(R

.450

Panel Centerline

.440

.43O

As Designed (Fig. 4.7)

"Q Near Net Design

e._

*- _ (Fig.4.15)

m Q.

n-

_ .420 } Flat Panel Range

0,1--

" _ No Filler u)

.410

.400

.390 1.12.2.13

Figure 4.21 Flow Data Results ZrCu Coarse Pattern Panels

Fine Panel Centerline

.370

Flat

.360

_o,-°° .350 - 3D, Near Net Form

,T _ Using Filler (Fig. 4.15)

.340 -

_3

.330 1.12,2.13

Figure 4.22 ZrCu Fine and Stepped Patterns Cold Flow Results

• Fine Pattern panels formed in near net configuration with filter material

maintained mass flow distribution across panel within 2%

Stepped

,,Q

.300

"_ .290

tZ.

o

Panel Centerline

Flat

.280

.270

3D, Near Net Form Using Filler (Fig. 4.15)

1,12.2.13

Figure 4.23 Cold Flow Results ZrCu Stepped Pattern

• Fine Pattern panels formed in near net configuration with filter material

maintained mass flow distribution across panel within 2%

58
Panel Centerline

Filled 4.15) .420 Formed (Fig.

o__ .410 Flat

I_ .400 1.12.2.13

Figure 4.24 Cold Flow Results CRES-304L Coarse Pattern

• Fine Pattern panels formed in near net configuration with filter material

maintained mass flow distribution across panel within 3%

Panel Centerline

.360

J_

m

._ca.350

_ _ .34O 0

_ .330

.320

Flat

Formed (Fig. 4.15)

Filled

1.12.2.13

Figure 4.25 Cold Flow Results CRES-304L Fine Pattern

• Fine Pattern panels formed in near net configuration with filter material

maintained mass flow distribution across panel within 3%

.310

.300

Panel Centerline

.260 -

.250

Figure 4.26 Cold Flow Results CRES-304L Stepped Pattern

Flat Panel

Formed with

Filler

1.12.2.13

• Fine Pattern panels formed in near net configuration with filter material

maintained mass flow distribution across panel within 4%

59
O_

O

Part No. SN

Die

Design 0.262

1204190-19 SN019 0.255

1204435-9 SN003 0.142"

Panel

Thickness

R

Barrel

R

Throat

2.83O 1.655

2.830 1.715 1st Iteration Fine Pattern

2.833 1.724 Thin Panel/Fine Pattern

120796-9 SN001 0.266 2.828 1.727 2nd Iteration Panel Design/Fine Pattern

1204435-19 SN001 0.376 2.837 1.832 Thick Panel/Fine Pattern

* Thin Panels Were Formed Using 0.125 Stainless Steel Shims.

Total Part Thickness While Forming Was 0.267

13.4.22

Figure 4.27. Spring Back in the Throat Section Increases With Panel Thickness
i :

OO6

i

011

014

i

OO5

0O5

i

0O9

027

027

039

Stack

He!ght

.242

.242

.242

.242

.242

.242

.25O

.250

.254

R barrel

i

2.876

2.866

i

• I

Rlhroal

1.666

ii

2.860 1.662

1.662

2.835

2.839

2.827

1.676

1.702

1.688

1.704

ml

1.696

2.825

2.834

Coarse pattern ZrCu

Not machined prior to form

.Secondary form with original 1 step die

Coarse ZrCu, Near Net

coarse, sS, Nea r Net, 1st Hit

Coarse SS, Near Net, 2nd' Hit

018

019

031

032

III I

021

023

i

024

035

i i i

Nominal Design

.254

.255

i

.250

.251

.254

.256

.255

.25O

2.826

2.818

2'.830

1.704

1.699

1.715

2.836 1.728

2.821 1.730

' 2.8'34

2.834

2.827

2.844

2.830

1.676

1.728

1.717

1.744

1.655

, C.o.am'.e.SS, Hear Net, Tabs Remov.ed

Fine ZrCu, Near Net

Fine SS, Near Net

ZrCu Fine, No Filler; Near Net

ZrCu Stepped, Near Net

SS Stepped, Near Net

VARIATIONS IN CONTOUR DATA IS DUE TO DIFFERENT PART THICKNESSES

Figure 4.28. Results of Contour Measurements 1st and 2nd Panel Design
thicknesses. All panels showed spring-back in the throat. Comparison of all panels indicates

that the amount of spring-back in the throat is a function of panel thickness. Thicker panels

show more spring-back than thinner panels. The 0.142, 0.255 and 0.266 inch thick panels all

have similar contours. Since the thin panels were formed using 0.125 inch stainless steel shims,

the total thickness of the part while forming was 0.267. Thick panels show a marked increase in

the amount of spring-back in the throat.

The contour of the forming dies was also measured using the Coord-Ax

CMM. The data indicates the alignment between the male and female dies is within about 0.002

in. The gap, however, varies from 0.253 to 0.256 inch in the converging section to 0.262 inch in

the throat, barrel and aft sections. This gap was shown to be acceptable. The die gap is

illustrated in Figure 4.29.

Seam channel and throat locations were determined with the OGP. This

OGP data, when coupled with the contour inspection data using the CAD, located the edge of the

seam channel in three-dimensional space. The distance could then be measured from the actual

edge of the channel to the desired location (90 degree sector.) This distance was then used to

adjust the flat platelet design layout to relocate the seam channel on the flat panels. The data

coupling method was used for panel designs two and three.

Subsequent improvements to the OGP software programs allowed all three

coordinates of a grid cross-pattern to be measured optically. This eliminated the need for the

Coord-Ax measurement step and improved the accuracy of the CAD database. Formed panels of

the third design were measured in this method.

To join four quarter panels properly the axial interface between the four

panels must be in perfect alignment along the entire length of the contour. Panel interfaces must

be flat and parallel to each other to accommodate a laser beam seal weld on both the inside and

outside diameter on each seam.

A comparison of the actual panel edge locations for the first and second

designs is shown in Figure 4.30. Although the second design had the panel edge closer to the

desired 90 degree plane, there was sufficient deviation to prevent joining of two panels.

4.5.7.6 Sectioning

Various panels were sectioned after forming to allow metallographic examination and dimensional inspection of the internal geometry.

RPT/G0114.119 62 October 5, 1992
L

s!xv JequJeqo eql 6uolv se!JeA deo e!Q "6_'b eJn6!_-I

£9_" i

_9_" ] ,

• _99_"

a!Q

I_JJe9 _JV
First Iteration Design

0 (Desired 90 ° Panel Interface)

4_

2 3 4

/

Second Iteration Design

Chamber

Location

1

2

3

4

5

Edge Location

Design Design

1 2

-0.1525 0.006

-0.0979 0.015

-0.212 -0.1105

-0.169 0.0394

-0.176 0.113

13.4.23A

Figure 4.30. Second Iteration Design Showed Improved Edge Location After Forming
Metallographic examination revealed quality bonds on all sections examined. No disbonds or delaminations were evident in any of the cross-sections.

Photomicrographs of typical bonds are shown in Section 5, Platelet Stack Joining.

Measurements were made of the channel orientation, channel geometry and

hot gas wall thickness. Skewing of the channels near the outer edges of the panels was observed.

The channels tended to tip, or lean toward the panel center at the O.D. of the panel, as illustrated

in Figure 4.31. Filler material reduced the amount of channel tip as shown in Figure 4.32.

The channel and land dimensions changed slightly after forming. In ZrCu

fine, stepped pattern panels the hot gas wall thickness at the throat increased about 0.001 to 0.002

inch, and the channel decreased in width by 0.001 to 0.003 inch. Measurements made of various

panel designs are presented in Table 4.3.

4.5.7.7 Additional Evaluations Performed

Several additional non-destructive test techniques were studied to determine their

effectiveness in evaluating the internal geometry of formed panels. X-Ray, Ultrasonic, EddyCurrent and CT-Scan inspection techniques were evaluated. The techniques were to be used to

determine the location of the outboard, or seam channel such that the seam land thickness after

panel trimming could be determined. The CT-Scan appeared to be the most promising of these

techniques, but further development would be required before using it to locate channels.

However, improvements in OGP CMM technique allowed direct measurement of the grid pattern

in X, Y, and Z coordinates. Thus the location of the seam channel was determined without the

need for additional inspections.

4.6 TASK 1.7 3D PANEL JOINING DEMONSTRATION

4.6.1 Introduction

Task 1.7 demonstrated the joining of formed platelet panels. A new channel

configuration was designed, panels fabricated and formed and two assemblies of two panels each

was made. Only the panel design and forming will be discussed here. The assembly procedure

will be discussed in Section 5, Panel Joining Demonstration.

RPT/G0114.119 65 C_,o_,5.199."
Pa_ Number

1204435-9 0.142

1204190-19 0.252

1204435-19 0.376

Panel

Thickness ellD

87.9

83.9

83.9

1

eOD

87.4

83,5

81.0

2

etD eOD

89.0 88.5

86.1 85.9

87.6 82.0

3

ejD eOD

85.8 84.6

80.1 78.6

78.2 77.6

4

eiD eOD

79.7 78.5

79.8 77.5

76.5 69.0

5

e0D eOD

87.0 85.6

81.7 81.0

78.6 78.2

G_

2 3 4 5

15-7-23

Figure _t.31. Skew of the Channel Along the Chamber Axis Increases With Part Thickness
MAX

CHANNEL

OFFSET

COURSE PA'I-I'ERN

FILLER NO FILLER

.006 .015

FILLER MATERIAL REDUCES DISTORTION OF CHANNELS DURING FORMING

Figure 4.32. Section Testing Results
k

c_

c_

TABLE 4.3

Nominal

Design

SECTION TESTING RESULTS ZrCu COARSE PATTERN, Page I of 5

:::'::::::::: ::::::: ::::::::::#:#:::::::i:::::::: :::-::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ::.::::::::::::::::::::::: ::::::::::::::::::::::;:: ::::::::i i!::i: ::::::::::::::::::::::: :::::::::: :::::::::::::::::::::::::::::::::::::: ::::::::::::::::::::::::::::::::::::::::::::::: .-'.::::::::: :::::i:::::: :::::::::::::::::::::::::::::::/::::i ::::;i::::::::::::::: ::::::::::i::

............ IIIIIITIIIIIiI'IIITII '"'"ill I1..,..v..=,-,.:....,,.,,v., v,v.v,,v.-,..v,v-:,.,.:.-,,....vv=,...... .......... ,....... ....., ,-,;.,.--:--;. ...... ...-...,,..,-.-.v...,-.-.......... ,. ,., • ............... ........

.030 .040 .040 .190 .020

Formed with

Filler

.032 to .033 to .035 to .197 to .021 to

.033 .035 .040 .198 .023

Formed

No Filler

Near Net

Formed with

Filler

Nominal

Design

.330 to .028 to .030 to .184 to .023 to

.0353 .030 .036 .190 .025

.029 to .035 to .040 to .190 to .019 to

.030 .038 .044 .195 .021

.030 .080 .080 .190 .020

Formed wtih .030 .079 to .083 to .187 to .020

I=iller .083 .086 .190

Formed

No Filler

.030 to .080 to .083 to .189 to .019 to

.031 .083 .086 .191 .020

Near Net

formed with

Filler

.031 to .078 to .084 to .190 to .018 to

.032 .081 .085 .191 .020
TABLE 4.3

SECTION TESTING RESULTS CRES 304L COARSE PATTERN, Page 2 of 5

::.-...'.'::.,.'.'::'?:.'; ?:." ":.'.'.'.M"..':.'; ".'.'.'.'.':.':.':.'.'::.'.','.':.':.'::.':.':.'.'.'. ...... .v.-.'.'::.':::M:.'.-" :.'.':.':.'.'.-::.'.'.'.'.':..'.'::.':.':.':." ::.'.'.':::.': __V.V:__`_::``._`_.`____:._:_`____::__._::`_._._`..`:`._.``___.:_._.`..___.`::`.```.:: :.'..'.':.','.'.'.':.-::::.-": .:::.'::.'.'.:.': .. :.-::.':.':.-::.:.'.'.'::.'.':.

".................. .VW, IIIr_D ............... _ ......................... ,.., ....... ,.................................. v:.v::::,.:::. -. ........ .......,.. ........ ::...v.v,.::::. ::::...v:::. ........ v •................ , -..:.....v:::

i.i.i.!.!.:..".:"$:_]N_.':_!i:?:i:ii i!:;!!i!ii!",: _..:_i.i.i.i.i.i.i.i.i.i.!.i.i.!.i.i.i_.i.i.).i.i.i.!.;.i.;.!.!.ii)iliiiii?E);i!iiE;iiii!iiiiiEiii! iEiEiiiiiiiii?i;):liii;!i??ii!?):ii:;Tiiiiii!iiii!i:FiiiTii!i?ii;iii?

•:.:.:.:. :.:.:.:.: :.: .:.: .:. :.:.:.: :.:. :.:.: .:.:. :..:. :.:. :.:.: .:.:.: .:.:. :.:. :.: .:.:.:.:...:.....:.:...:...:...:.:.. ..:.:. .:.:. .::.:.:...:.:..; .:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:.:. :.:.:.:.:.:.:.:. :-:-:-:.:.;.:.:.:-:.:.: T:-:.:.: .++:+:+: .:+:.:+:-: .+:.:..:+:-: +:.:+:.:.:+:.:+:.:.:+:+..:+:+:.:, :+:.: ..:.T+ :.:. :.:.:+:+:. :.:. :+:.:+ >:.:+:..:::.:.:+:+:+:+:+

I I I I IIII III I I II I I I IIII I I

Nominal .030 .040 .040 .190 .030

_0 Design

Formed with

Filler

.029 to .035 to .039 to .186 to .030 to

.032 .036 .043 .194 .032

Nominal

.J

LU Design

Formed with

Filler

I I I

.030 .080 .080 .190 .030

.031to .079to .082to .187to .028to

.032 .082 .085 .190 .030

/

i i i
"--.3

0

Nominal

Design

3D Formed

Filler

.013to .0138 to .0176 to .140to .096to

.014 .0155 .0199 .144 .102

Nominal

Design

3D Formed

Filler

.012 .050 .050 .184 .058

.012 to .0475 tO .0463 to .0186 to .055 to

.013 .0486 .0497 .0188 .057
,..j

Nominal

Design

3D Formed

Filler

TABLE 4.3

SECTION TESTING RESULTS CRES 304L FINE PATTERN, Page 4 of 5

i !GASiiiiSl D Eiiiiiiiii!iIiiiiiiiiii iii!iiii:iiiiiiii!i!iii!iiiiiiiiiii!iiiiiiiiii iiiiiiiiii!iiiiiiiiiiiiiiiiiii!!iii!i!:I:ii i!!ii_i!i!!i!iiii!i!i!:!i!i!!!i!!ii!iii!iii!i!!!i!iii!iii!i!iiiiii!!iiiii!iii!!!!!!_!!ii!!ii!!ii_*ii!ii!_!ii!!!i!

........ _li' ................... ,,_ _,'""'" ""'" ...... "_- "_" .......... _...................................................... i.......................................................... :+:.:.:.:.[.ji.i.llll_rlMlRI IL._T_ : ................ .=.'P...." ..'.'.'.v:.'.v.vv.'.'.',v.v.v.v.'.v.v.v......'...'.... "...'v."" ..."" v':.'.-.v'.v.v.v.v..'..'..v........."..'....v.."........... •...:..:..'.'."."".:............................................

_:_i_i:!_i:_:!_i_!:_:_:_!_! i:_i:_;i_i, :__:_:_ !_!_!_ii_i_i_i_!!_i_!_i!_!l _ii_!!:i_i_i_ii:_i_i_:!_!i_!i!_:!!i_i!_,_!_i_:i_ _i!:_i i_i_:!!!_i:i:i_!_!_!!!_i_i!!_!!iii:_!i_;!_:!!_!!!_i::i___!il i!i_i_ii!!ii:_i!!i!iii!_

I IIIIIIIIII

.010 .020 .020 .190 .050

.O09to .0176 to .0199 to .184to .051 to

.011 .021 .0121 .192 .052

..J

uJ

Nominal

Design

.010 .050 .050 .190 .050

3D Formed

Filler

.011 to .0497 to .0508 to .189 to .0474 to

.012 .0508 .0519 .190 .0496
t_

Nominal

Design

IFormed with Filler

TABLE 4.3

SECTION TESTING RESULTS ZrCu FINE PATTERN, Page 5 of 5

""_"i""ii__"_""i"I:"___ii__ '........... iiiiiiiii___....... i!il___iiii!i

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.012 .020 .020 .190 .050

.012 to .017 to .019 to .190 to .051 to

.013 .018 .020 .193 .053

Nominal

Design

_J Formed with

Filler

I

.012 .050 .050 .190 .050

.012 to .046 to .047 to .190 to .049 to

.014 .049 .050 .192 .050
4.6.2 Platelet Design

Eight panels, part number 1206530, were fabricated for this task. The channel design was an iteration of the second panel design from Task 1.3, part number 1204796. A

computerized method for predicting the location for the 90 ° located panel edges, known as the

Transformation Equation, was developed and used for the design of these panels, and is

described below. The panel design was similar to the Forming Experiment panel designs, with

the exception of the slots for the forming throat pins. The slots were closed, as shown in Figure

4.33, to prevent deformation (widening) of the slot during forming. Previous slot deformation

had led to misalignment of the panel in the forming dies, resulting in throat shift.

4.6.3 The Transformation Equation

The forming of a platelet panel to a three dimensional chamber shape from a

flat panel distorts the location of the channels. When designing the flat panel, the channels must

be placed such that after forming, they end up in the proper location to allow trimming of the

panels to a 90 degree segment. The desired panel design should have, after trimming, a .020

constant land width between the last channel and the edge of the part.

The channels in the first panel design were located assuming that the surface

of the hot gas wall does not deform during panel forming. After measuring the location of the

edge of the first panel after forming, the second channel design was modified to account for the

stretch and deformation of the panel during forming. In this second design, the location of a

channel station was changed by the distance from the desired to the actual location on the formed

panel. Although the location of the outer channel was closer to the desired location, the channel

position was still not correct. Figure 4.34 illustrates the edge locations of both panel designs.

A method was developed to improve the prediction techniques by accounting

for the stretch, or deformation of the panel due to forming. A set of transformation equations

was developed to predict the channel locations for new iterations. These equations related the'-

location of features on a formed panel to the desired feature location, and then predicted the

feature location on a new flat panel design compared to the old design.

The improved method of predicting channel location requires an initial panel

design from which to iterate. The panel edge data and deformed areas are obtained from OGP

measurements of the intersection of lightly-etched grids placed on the hot gas wall. A functional

RPT/G0114.119 73 October 5, 1992
L

u6!sao _,ala],eld uo!leJ_,suouJao 5U!:l.u!op laued "££'17aJnS!-I

J,olS 6up,eool
tn

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<

Z

:E

O

z

:E

O

E

O

O

_.I

LU

a

ILl

EXIT

i

--I 0

I

THROAT

CENTERLIIIE

T I F T

1 2 .3 4

AX_L LOCATON

BARREL

DESIGN #1

DESIGN #2

0#2. I'rE:R# I

Figure 4.34. Seam Channel Land Location Results
part can be made after the proper location of the channels is known by not etching the grid pattern on the hot gas wall.

4.6.4 Forming Results

Eight panels with the improved channel design were cold formed.

Measurements of the distance from the outer channel .edge to the desired 90 degree edge location

is shown in Figure 4.35. The channel was close enough to the desired location to allow trimming

and joining of two panels while maintaining the intended 0.020 inch minimum half land. The

trimming plane of the panel was slightly outboard of the 90 degree location, however, which

would prevent assembly of four panels of this design.

4.7 TASK 1.9 CONTOUR FORMING EXPERIMENTS

4.7.1 Introduction

Contour measurements of panels formed during Task 1.3 indicated springback significant enough to require a modification to the forming method. Two methods of

eliminating the springback were considered; over-forming and hot-sizing.

The fast method, overforming the panel to a bend radius sharper than the

desired radius, would require successive die contour iterations to achieve the correct contour.

Although the overforming approach may be appropriate for large-quantity production runs, it

was deemed too costly for the Formed Platelet Liner program due to the number of die

modifications anticipated.

An alternate approach to eliminating springback, hot-sizing, was pursued.

The hot-sizing method places a formed panel into a die set with the desired contour, and stress

relieves the panel in a restrained condition to remove the residual stresses from forming. Three

hot-sizing experiments were conducted to optimize the hot-sizing parameters.

4.7.2 Discussion

Eight new panels were fabricated for this task. The panel design used was a

modified first design fine pattern, part number 1204435. Five new platelet patterns were made

which decreased the channel height in the throat area. A decreased throat channel height is

reflective of a functional panel, and when used in the hot-sizing experiments, would yield more

RPT/G0114.119 76 O_,o_r 5, 1992
0.08

;3

0

Fz

0

0

GO

0

Q.

0

II

g.

w

0

Z

121

.06 .........................................................................................................................................................................................................................

0.04 ..............................................................................................................................................................................

-0.06 .............................................................................................................................................................

-0.08 , , , , , , , ,

-6 -5 -4 -3 -2 -1 0 1 2

AXIAL DISTANCE FROM THROAT

3

Figure 4.35. Formed Platelet Edge Deviation 3D Joining Demo Panels
pertinent data. The eight panels were cold-formed using the one-step process with the modified

die set.

Another set of panels was designed and fabricated during the same time, the

Panel Joining Demonstration panels. These panels also had a channel design with a reduced

throat height. In addition, the outer channel location in these panels had been relocated to allow

joining of two 90 degree panel segments after forming. Because the Panel Joining

Demonstration panels were completed before the hot-sizing experiments began, and as these

panels were to be used as a basis for iteration for the Phase B panels, they were used for hotsizing.

A hot size die was fabricated with the desired final contour, and is shown in

Figure 4.36. The die contours were measured with the COORD-AX CMM, and the die gap

calculated. The die gap was found to be 0.002 inch smaller than the panel thickness in the bah'el

region. However, the panels were also thinner in edges of the throat region by 0.007 inch.

4.7.3 Hot Sizing Experiments

Three hot sizing experiments were conducted. The parameters for the first

experiment allowed the panel to be annealed in the restrained condition. A 0.002 inch shim was

placed between the die halves at the periphery, the shim prevented excessive crushing, or creep,

of the panel. After the experiment was run it was found that a gap remained between the shim

and the die.

Inspection of the first panel after the hot sizing operation showed that in areas

where full contact was made the shape of the fixture was exceedingly well duplicated. In areas

where full contact was not made the contour was improved but not to the final desired contour.

The two subsequent experiments attempted to compensate for the thick areas of the panel, such

that in the thin (throat) areas the desired contour could be obtained.

The results of the second experiment showed an improvement over the first,

although full contact to the I.D. die was not yet made. The same panel was then run through

another hot sizing at increased time and pressure. This set of parameters allows the panel to very

nearly replicate the desired inside contour, as shown in Figures 4.37 and 4.38. The panel formed

with the third set of hot-sizing parameters is within 0.003 inch of the nominal contour.

78

RPT/G0114.119 October 5, 1992
_LACK AND WHITE _ ':< _ <"_' ::"-i

79
Restrained Anneal Results

I

I

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EXP. 2&3 r-Desired Contour

"_,./ 1.655 Radius

/ __._.

As Cold Formed J "" -._"__'_ ..

EXP. 1, 2, & 3 .-......_= /- Desired Contour

• ,,_ 2.830Radius ,

-.\

As Cold Formed -_'=" _'_

NOTE: Data Normalized at Throat,

Deviations Exaggerate_for Clarity,

Note Scale of Deviation

I

J

I

i

I

I

!

I

I

I

I

I

Scale: 0.025 = 0.001

Scale: 0.05=0.001

j s

Figure 4,37. Radial Contour Comparison
Restrained Anneal Results

I

J..___

I

I

I

I

/- Desired Contour s " J

.... !

EXP. 1 NOTE: Data Normalized at Throat,

Exaggerated for Clarity, Deviations

-As Cold Formed Scale of Deviation: 0.2=0.001

I

Figure 4.38. Axial Contour Comparison
4.8 FORMING EXPERIMENT CONCLUSIONS

The Phase A forming experiments demonstrated that flat platelet panels with intemal

coolant channels can be formed to a three dimensional shape suitable for use in a combustion

chamber. Although only panels which were symmetric about the throat were formed, the

forming information learned can be applied to other geometries. The basic forming process

includes the following steps:

1)

2)

Fabricate a flat platelet panel with a near-net shape. The channel locations can

be initially calculated based on actual geometry. Iterations to the channel locations are made with the Transformation Equation, which can account for the

panel deformation due to forming. Include slots in the panel design for alignment of the panel to the forming dies.

\

Fill the panel with the Aerojet polymer to prevent buckling of the lands during

forming.

3) Cold-form the panels in an hydraulic press in a single-step process, aligning the

panel to the die axis and throat center with pins which engage with slots in the

panels.

4) Hot-size the panels to remove spring back.

Additional conclusions can be drawn from the forming experiments:

1) The forming operation is a repeatable process which provides consistent parts.

2) The formed panel channel flow characteristics are predictable and acceptable.

3) Visual inspection of critical internal geometry dimensions of all cross-sectioned

formed panels (i.e. hot gas wall thickness, channel width) are not adversely ,-

affected by the forming process, and are acceptable for fabricating functional

parts.

4) Panels with a smaller thickness to bend radius ratio are easier to form.

5) Hot gas wall thicknesses of 0.008 to 0.033 inch can be successfully formed.

6) Panels with channel aspect ratios of 15.5:1 can be successfully formed.

RPT/G0114.119 82 October 5. 1992
7)

8)

9)

The Transformation Equation is a viable tool in predicting channel locations.

Hot-sizing of formed panels removes spring-back from cold-forming, and

results in panels with the desired contour.

The platelet bond integrity is unaffected by the forming operation. Visual

inspection of all cross-sectioned formed panels confirmed good platelet to

platelet bonding.

RPT/G0114.119 83 October 6, 1992
J

5.0 PLATELET STACK JOINING

5.1 INTRODUCTION

A regeneratively cooled combustion chamber liner made from formed platelet

segments may require that the segments making up the liner be joined together. The joint may

be required for functional chamber operation or to accommodate certain combustion chamber

assembly techniques. Methods to affect such a joint were investigated in this task.

There are two primary locations where a joint between adjoining segments Can be

made; in the land or in the channel. Both of these joint locations were attempted. Joining

methods investigated were laser and EB welding and diffusion bonding. Braze assembly was not

pursued but is considered to be a potentially viable process.

Development and demonstration of the joining processes and techniques was made

using fiat samples, 2D samples and, on the selected process, 3D samples. Contract Task 1.4 covered the flat and 2D work; Task 1.7 covered 3D work. Concurrent with the development of the

joining process was the development of inspection processes to allow non-destructive evaluation

(NDE) of the joint.

5.2 OBJECTIVE

The objective of this study was to develop and demonstrate a process, or processes,

for the joining of the longitudinal seams that exist between adjacent formed platelet liner panels.

A further objective was to identify inspection or verification techniques that can be used to assess

whether or not a joint had been affected and to assess the quality of the joint.

5.3 APPROACH

The approach taken was first to identify the issues associated with making a joint

between liner segments. A list of these issues appears in Table 5.1, below. The next portion of'-

the task was to decide what type of samples and what basic processes would be used for the process development and process demonstration. Figure 5.1 is a graphical depiction of the logic of

the program plan. Due to the need to obtain joining data concurrent with the forming

experiments it was decided to first do feasibility assessments with platelet stock alone and then

use simplified flat bonded platelet specimens for further process assessment and development.

These investigations utilizing platelet stacks for further development were limited to ZrCu as the

material of interest.

84

RPT/G0114.119 --- October 5, 1992
TABLE 5.1

IDENTIFIED JOINING ISSUES

• Joint Location

• Joint Configuration

• Channel Aspect Ratio

• Gas Side Wall Thickness

• Land Width

• Material Weldability

• Contoured Weld

• Machining of Contoured Part

• Preparation of Joint

• Tooling

• Verification of Joint

• Sealing of Joint, if Required

At the completion of the feasibility and fiat sample studies a down-select of the most

promising process was made and then demonstrated on 2D specimens having a contour identical

to the Phase A panel forming specimens. This task also provided additional process

development and refinement. Successful completion of the 2D samples was intended to be

followed by demonstration of the process on 3D panels taken from the Phase A forming

experiments.

Techniques used to evaluate the samples included visual examination, dissection and

subsequent metallography, and scanning electron microscopy. For some samples, in process leak

check procedures were also developed. Radiographic inspection was also employed to detect the

presence of a bonded joint in those samples examining diffusion bond joining.

5.4 DISCUSSION "-

5.4.1 Joining Issues

The joining issues are identified in Table 5.1 and are those that were

addressed by the joining studies of Tasks 1.4 and 1.7. Each of the identified issues were

addressed as follows:

85

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Joint location: Evaluate whether to place the joint in the land or in the channel;

both were examined in this study.

Joint configuration: Evaluate the actual shape of the joint, i.e. straight, stepped

or contoured. In this study only straight joints that would simulate a radial joint

in a true assembly were considered.

Channel aspect ratio: Evaluate the impact of channel aspect ratio on panel

joining. Panels with high aspect channels may be more difficult to join, as seam

land machining and handling, and (weld) joint depth become more difficult. In

this study simplified flat samples that had lands sufficiently tall to simulate high

aspect ratio channels were used. A sketch of these samples appears as Figure

5.2. For the 3D joining demo of Task 1.7, the aspect ratio was 10.2.

Gas side wall thickness: The effects of hot gas wall thickness on panel joining

were studied. A thinner gas side wall would present more of a problem than a

thick wall, especially in joints made in the channel. Joint preparation limitations

and thermal mass considerations were addressed. Hot gas walls as thin as 0.008

inches thick were studied.

Land width: Thin lands can pose problems similar to that of high aspect ratio

channels. Panel joining can be further complicated by the decreased thermal

mass of thin lands that could affect the ability to make certain types of weld

joints. On the flat samples half-land widths as small as .010 were examined.

Figure 5.2 shows the three land widths of the flat samples examined. The 3D

demo had .020 lands.

Material weldability: The material of the formed panels must be easily welded

for processes employing welding as either an in-process seal or as the primary

joining method. Two materials were originally considered: 300 series CRES

and ZrCu. Early screening tests narrowed this down 304L CRES and ZrCu, two

readily weldable alloys. Further narrowing of the program eliminated the CRES

samples and all remaining work was performed on ZrCu.

Contoured weld: As the actual hardware employs a converging/diverging

nozzle contour, the ability to make a contoured weld was of prime importance.

This is further complicated by the fact that the gas side wall welds must be

made from the inside of the part. This concern was addressed by the fabrication

RPT/G0114.119 87 October 5. 1992
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of both 2D and 3D samples and by tooling that allowed welding from the ID of

a part.

Machining of contoured part: This issue deals with the initial preparation of the

joint. The means for accurately machining the joint to provide the desired

location, the land width, and the surface required for the subsequent joining

operation were evaluated. Methods investigated included wire Electrical

Discharge Machining (EDM), milling, and grinding.

Preparation of joint: For each type of joint considered there are different

requirements for the surfaces. For example, for a diffusion bonded joint the

cleanliness and the presence of a bond aid can be critical; for welding edge

rounding is not desirable. The study looked at processes of multiple pass

EDMing to minimize recast, lapping, chemical etching, electro-polishing, and

electro-plating and combinations of these processes.

Tooling: For certain processes special tooling is required. Machining or

trimming of the panel edges requires fixturing, as does assembly of the panels

edge-to-edge. Welding of the inside of the panels requires special tooling.

These issues were addressed by this study.

Verification of the joint: This issue deals with a means for detecting whether a

joint has actually been effected or not and means for evaluating the quality of

the joint. Methods investigated included radiographic inspection and

destructive metallography.

Sealing of joint: Certain joining processes, most notably HIP diffusion bonding,

require that a seal be effected around the entire joint periphery. To assure a seal

has been made and maintained requires a means for leak detection; such means

was evaluated and developed during this study.

5.4.2 Initial Joining Experiments - Task 1.4

Following initial screening of available processes and configurations, and

considering the above issues, a down-select of the desirable parameters was made. Table 5.2

defines the joint configurations, the land widths and the joining processes that were investigated

in the initial joining study.

RPT/G0114.119 89 October 5. 1992
TABLE 5.2

JOINING PARAMETERS INVESTIGATED USING

SIMPLE/LINEAR SAMPLES

2 Joint Configurations:

Joint in Land

Joint In Channel

2 Land Widths:

0.020

0.050

3 Methods of Joining

Laser Weld

EB Weld

Diffusion Bonding

- User Laser And/Or EB Weld for Sealing

- Use HIP

The platelet joining samples used in the initial study are shown in Figure 5.2.

They were designed to have a simple geometry to eliminate high machining and tooling costs

and to provide meaningful joining data early in the program. Table 5.3 lists the design part numbers and the configurations options of the basic design. All samples were ZrCu material, except

as noted. Note that the land width mentioned in the parameter list of Table 5.2 is a composite

land width made from two halves of a sample that had previously been cut in two.

!

90

RPT/G0114.119 October 5, 1992
TABLE 5.3

JOINING PARAMETERS INVESTIGATED USING

SIMPLE/LINEAR SAMPLES

Land Gas Side Wall

Pa_ No. Width "L" Thickness, tg

1204189-9A .020 .008

1204189-9B .020 .012

1204189-9C .020 .017

1204189-19A .040 .008

1204189-19B .040 .012

1204189-19C .040 .017

1204189-29A .060 .008

1204189-29B .060 .012

1204189-29C .060 .017

*1204189-39A .020 .010

*1204189-39B .020 .014

*1204189-49A .040 .010

*1204189-49B .040 .014

Figure 5.3 shows pictorially the two weld joint configurations investigated.

For the channel weld evaluations it was recognized that the kinetic energy associated with an

electron beam (EB) weld made it a high-risk candidate for a full penetration hot gas side weld;

therefore only laser welding was considered for this weld. Thermal input considerations, coupled with mechanical limitations when welding internal to an actual liner, eliminated EB as a

candidate for even the land weld option. Laser and/or EB were considered viable for backside

welding for either the land weld or channel weld configurations.

Laser welding technology has many distinct advantages for this type of

application, including the ability to direct the beam with prisms and mirrors into what might

otherwise be inaccessible areas. One definite disadvantage with the laser welding of copper

alloys is the high power required to melt the substrate resulting from its high reflectivity. This

limits practical depths of weld penetration to a few thousands of an inch, generally in the range'-

of .003 to .010. Increasing weld depth by increasing energy input seems to have a deleterious

effect on the weld surface as material vaporizes leaving a rough appearance. Further, a

phenomenon occurs wherein the energy reflected back from the part heats the focusing lens,

changing the focus (de-focusing) and therefore changing (reducing) the depth of penetration as a

joint is traversed. Means to overcome these problems were developed and are discussed below.

91

RPT/G0114.119 October 5. 1992
EB Laser Laser

Laser

LAND WELD

|

CHANNEL WELD

Figure 5.3. Weld Joint Configurations
An example of the results of the channel weld study is shown in Figure 5.4.

In this sample laser was used for both gas side and backside welds. This sample had an 0.008

inch thick hot gas wall, near the practical limit of laser weld penetration into copper. Considering

the difficulty with which such a joint is machined and handled, the criticality of the fitup of the

joint, and the penetration limitations of the only viable weld option, an in-channel joint of this

configuration has very limited application. It would, in fact, be viable only for very thin hot gas

wall sections.

Figure 5.5 shows the results of an in-land joint sample. In this sample laser

welding was employed for the hot gas wall welding and EB was used for the back side welding.

The half lands of this sample were nominally .010 thick, making for a total land width of 0.020,

nominally. This sample also had a 0.008 hot gas wall, and a 0.050 backside wall. These values

of demonstrated parameters are approaching the practical limits for fabrication and functionality.

Any increase in the numerical value of these parameters improves the producibility aspects of the

assembly. As such, this method of joining appears applicable to a wide variety of combinations

of land widths, hot gas wall and backside wall thicknesses. The disadvantage to this approach is

that full penetration welds cannot be obtained thus leaving a non-joined area between the welds

in the land.

The next series of joining specimens examined the concept of diffusion

bonding the half lands together. This approach would eliminate the non-joined area associated

with the above described process. The concept adopted was one of a self-tooling assembly

wherein the assembly itself provided a sealed joint. The sealing would be accomplished by the

welding processes developed and described above. The faying surfaces of this sealed joint

would diffusion bond together when subjectedto the environment of a Hot Isostatic Press, or

HIP, at the prescribed pressure, temperature and duration.

Again, the flat sample design of Figure 5.2 was employed for this series of

experiments. The first samples prepared were four in number and employed a 0.010 inch half

land. Wire EDM was used to machine the laying surfaces and obtain the 0.010 half land thick-"-

ness; these surfaces were then hand lapped. Two of the samples were plated with a bond aid and

two were assembled with as-lapped surfaces. The longitudinal seams of the joints, simulating

the ID and OD of a liner, were welded by laser. One end seam of each sample was also laser

welded. The opposite end seams were EB welded in order to obtain a vacuum in the joint. All

samples were processed in the same HIP run.

RPT/G0114.119 93 October 5, 1992
--Laser

Closeout

M101D9NG-2-1

.008 Gas

Sidewall

Figure 5.4. Channel Weld Results
.050 -_

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EB Weld

50X

Laser

Weld

125X

Figure 5.5. Land Weld Results
Sectioning of the four samples showed partial bonding in the aided bond

joints. Bonding did not occur in the unaided samples. Photomicrographs of the sample sections

are shown in Figure 5.6. In all samples there is evidence of a porous layer that exists below the

bond aid. It is felt that this layer, which is residual recast from the wire EDM operation, inhibits

the bonding process. Comparison of hand polished and as-cut wire EDM surfaces showed that,

with the method used, approximately half of the recast layer was removed; this comparison is

shown in Figure 5.7.

The above experiments illustrated the need for a complete understanding of

the roles the residual EDM recast layer and joint sealing were playing in the ability to affect a

diffusion bond in the samples. As such, a plan to look at different methods of removing the

suspect layer and improve joint sealing was developed. Figure 5.8 and Table 5.4 were developed

and used to identify and evaluate the critical parameters.

Concurrent with detailed evaluation of the critical parameters, eight additional joint samples, again using the sample design of Figure 5.2, were prepared. Four samples

had their faying surfaces mechanically milled and four had their faying surfaces chemically

milled. All samples had bond aid applied. Three sides of each joint were laser welded and the

fourth was EB welded. All welds were inspected visually and with the aid of both an optical

microscope and a Scanning Electron Microscope prior to HIP processing. This inspection

revealed that a possible leak path existed in two of the joints; one joint in each of the two groups

of four samples. All other welds examined showed no potential leak paths.

After HIP processing, each joint was sectioned and examined. Two of the

four chemically milled prepared samples showed 100% bonding, as shown in Figure 5.9. The

remaining two showed only partial bonding; one of these joints had the aforementioned suspect

weld, the other had a platelet surface defect that inhibited the original platelet-to-platelet bond

that was detected in the post bond examination. None of the joints in the mechanically machined

prepared samples bonded.

These experiments showed that a diffusion bond could be made between

mating surfaces of the edges of previously bonded platelet stacks, in a configuration consistent

with that required for joining formed platelet chamber sections at a land. These, and previous,

experiments also showed that further development of the pre-bond processing parameters was

required to improve the reliability of the bond process. Experiments to optimize the pre-bond

processing as identified in Figure 5.8 and Table 5.4 were next carried out to improve the process

reliability. The basic process is as shown in Figure 5.10. Experiments were designed to oPtimize

RPT/G0114.119 96 October 5, 1992
Unaided Joint

No Bonding

Aided Joint

Partial Bonding

Figure 5,6, Photomicrographs of HIP Processed Samples
• Appeared Visually Acceptable

• Unsuccessful In Completely Removing Entire Recast Layer

oo

.001 _ Recast Layer

Untreated Wire EDM Surface

!

.0o05 _ _ Recast Layer

Polished Surfaces

Fi_gure 5.7. Comparison of "As-EDM'd" and Hand Polished Surfaces
',D

Bonded

&

Formed

Platelet

Stack

Primary Prep Operation

.__ Mill i

Prep

Edges

• Fitup

• Smeared Metal

• Contamination

OR

Secondary Prep Operatlon

__ Chem i

Etch

Edges

• Masking - Comer Roundings (Fitup)

• Mat'l Removal Parameters

B OR • Chemistry/Concent

• ]]me

• Temp

-t I "t -

EDM (Wire) (_ (Sand)

• Fitup • Flatness • Masking - Comer Roundings (F_up)

• Recast • Grit • Marl Removal Parameters

• Parameters • Chem/Conc

• Speed • Contamination • ]]me

• Current • Temp

• Arrp4:12

c-13 Etch

Clean-up

• Marl Removal Para.

• Chem/Conc

• ]]me

• Temp

• Required If Mask

Platlng Operatlon Jolnlng Oper. 1 Jolnlng Oper. 2

(_ Storage = "A Plating I _ Storage _ Edges Laser Weld =_ A EBW Ends _ &Bond HipSTA _(_

I I

• Atrnos. • Atmos.

• Time • _me

• Cleaning • Fixturing • Fitup

I • Masking I I • Fltup I I • Parameters

• Activation I I • Gap W'_h I I • Penetration I • Fixturing • Parameters • Power

I " Plating Thickness I I • Penetration I I • Focus

• Plating Uniformity • Power • Speed/Travel

I I I oFoUs I I .Vacuum

3 L. s ( ava)y Lq Monito,ng

• Parameters

• ]]me

.Temp

• Pressure

!

FPL 2/14 Ol

Figure 5.8. Process Flow of Diffusion Bond Joining of Formed Platelet Panels
TABLE 5.4. CRITICAL PROCESSES FOR DIFFUSION BOND JOINING, SHEET 1 OF 3 /

o

Basic

Process

Edge Prep

Specific

Process

Mill Edge

EDM Edge

Lap Edge

Chem Etch

Edge

Nature Of Risk Or Concern

• Fitup of Matting Edges

Excessive Gap

Inabilityto Weld (Seal)

Excessive Deformation Req'd for Bond

Thinning of Walls

Breakthrough - Leaks

Inability To Seal For Bond

• Smeared Metal

Entrapped Contaminants

Inhibit Bondings

Fitup of Matting Edge

Excessive Gap - See Above

Thinning Of Walls - See Above

Recast Layer

Inhibit Bonding

Thickness

Consistency

• Flatness

Comer Rounding

• Material Removal Control

• Contamination Potential

• Comer Rounding

Masking Req'd (If req. a lot of mat'l removed)

• Contamination Potential

• Material Removal Control

• Preferential Etch of Elements

Criticality

1

2

2

2

1

2

1

1

Risk Reduction

Full Size Sample -

Process Control

Remove (Etch or E.P.)

Full Size Sample -

Remove (Etch or E.P.)

Samples - Set's

Control Parameters

Minimize Recast

Minimize Mat's Removal

Use Si Carbide Paper

Of 600 Grit or Finer

Consider Eliminate By

"finer" EDM cut

Minimize Mat'l Req'd To

Be Removed

Chem Etch Cleanup If Req'd

Samples To Define Process

& Req'd CTRLS

FPL 2114 02
TABLE 5.4. CRITICAL PROCESSES FOR DIFFUSION BOND JOINING, SHEET 2 OF 3

o

Basic

Process

Edge Prep

(cont'd)

Storage

Plating

Specific

Process Nature Of Risk Or Concern Criticality

Electro • Corner Rounding 1

Polish Masking Req'd (if req a lot of Mat'l Rem.)

Edge • Contamination Potential 2

• Material Removal Control 1

Chem Etch • Req°d If Mask For Etch Or Electro Polish

Cleanup • Material Removal Control 2

Storage • Contamination Or Oxidation 2

Vapor

Degrease

Caustic

ElectroClean

Rinse

Masking.

HCI

Activation

Plating

• None

• Adequate Cleaning 1

• Excessive Mat'l Removal 2

• Adequate Rinsing 2

• Req'd If Want Plate Only Edges

Contamination Potential

• Adequacy

May Not Be Adequate If Contam. (Mask)

• Thickness Control

Excessive - Potential Cracks, etc.

Not Enough - Weak Bonds

• Adhesion

Inspection Difficult

Risk Reduction

Minimize Mat'l Req'd to

be removed

Chem Etch Cleanup

Samples To Define Process

& Req'd CTRLS

Use Data From Chem Etch Of

Edges Expmt. To Define

Process & CTRLS

Cleaning For Plate S/B adeq.

Plating Expmts. to Verify

Samples to Define Process

& CTRLS

Investigate Eliminate Weld

Sample Req'd.

It n

Or Other Means of ACt.

Samples To Define Process

& CTRLS

Shielding May be Req'd

Consider Oven Bake of

Samples/Hardware

FPL 2114 03
TABLE 5.4. CRITICAL PROCESSES FOR DIFFUSION BOND JOINING, SHEET 3 OF 3

o

Basic

Process

Storage

Join

Edges

Joining Of

Land

Specific

Process

Storage

Laser Weld

EBW Ends

Monitoring

Of Vacuum

HIP Bond

&

STA

I

Nature Of Risk Or Concern

• Control Of Vac. Or Inert Adequate

Fitup - Fixturing

Excessive Gap

Inability To Weld (Seal)

• Weld Repeatability

• Rework Capability

Inspection to Identify Problems

Fitup -

Excessive Gap

Inability To Weld (Seal)

• Weld Repeatability

Rework Capability

Loss Of Vacuum W/O Recognition

InabilityTo Diff Bond

• Process Repeatability

• Inspection Of Bond

• If Concurrent w/Bond, May Degrade

Properties If Rework

• Rework

Criticality

2

Risk Reduction

Verify By Samples To Be

Welded/Bonded, Record

Actuals

Full Size Sample

"Flexible" Tooling

(See Vac Monitoring)

Samples To Define Parameters & CTRL To These

Parameters

W

Samples, Incl. Full

(See Vac Monitoring)

Samples To Define Parameters & CTRL

W

Need Special Program To

Address Issue

Process CTRLS & Verification

By Sample

Investigate Available NDE

FPL 2/14 04
Potential Leak Path

Detected by SEM

Prior to Bond

Parts Sectioned in

Two Locations

• _ Partial Bonding

/ 100% Bonding

14.01.12

100 X

Figure 5,9, Two Interfaces in the Chemical Machined Sample Achieved 100% Bonding

103
o

Bonded

&

Formed

Assy

Figure 5.10. Diffusion Bond Edge Joining Process

FPL_14 05
the edge preparation and laser welding of the platelet stack interfaces prior to HIP processing.

Special attention was given to minimizing the recast layer thickness during wire EDM, removing

the recast layer by chemical machining, and the bond aid application process.

A series of copper samples were machined by wire EDM to determine

parameters that would minimize the recast layer thickness. Reducing the recast layer insures that

a minimum etch time will be necessary to completely remove it. Results of the EDM samples

showed that the recast layer could be reduced to as little as .0001 inch. This is shown in Figure

5.11 that compares a previously prepared EDM surface to a surface prepared with the optimized

parameters.

Etch experiments were run on samples of diffusion bonded ZrCu platelet

stacks machined using the optimized EDM parameters. Solutions of HNO3 and HF of varying

concentrations and temperatures were used along with varying immersion times to determine the

best etch parameters. Figure 5.12 shows the results of the optimum parameters; these parameters

produced the least preferential etching and edge rounding while completely removing the recast

layer.

After determining the interface preparation methods, bond aid application

experiments were performed to optimize this process. Process parameters that were investigated

included caustic cleaning, activation time, plating time and plating current density. Evaluation of

the samples included adhesion testing, plating thickness, plating uniformity, and platelet stackplating interface examination using the Scanning Electron Microscope (SEM). Eleven samples

were machined per the processes developed in the previous optimization studies in preparation

for plating. After plating, the samples were baked for an hour at 625 degrees F to evaluate

plating adhesion. Plating thickness and uniformity testing was done using X-ray Fluorescence.

Each sample was measured in 12 places to determine plating thickness and to evaluate plating

uniformity.

Results of the plating experiments showed good adhesion for all samples ,--

tested. Optimum plating time and current density were determined from uniformity and

thickness testing. SEM results showed that caustic cleaning was unnecessary following surface

etching.

Laser welding experiments were next conducted to determine the effect of the

plated bond aid on surfaces normal to the weld. Prior to this time efforts had been made to completely eliminate bond aid from this area; the reasoning being that it could inhibit the welding

process. One of the problems noted in the initial laser weld experiments was that the high

RPT/G0114.119 1 05 October 5, 1992
• • • L

Optimized Wire EDM Technique Original Wire EDM Technique

Figure 5.11. Comparison of Wire EDM Processes
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As EDM'ed After Etch

Figure 5!12. Etch Parameter Optimization Provided Complete Recast Removal
reflectivity of the copper requires very high power densities to affect a weld. This energy

reflected from the workpiece causes heating of the laser optics and a resultant change in beam

focus. The change in beam focus in turn causes varying weld characteristics along the length of

the weld. This series of experiments was undertaken to see if the presence of the bond aid could

alter the surface reflectivity and improve the weldability of the copper alloy.

Results of the experiment showed that the bond aid could indeed improve the

weld. Weld penetration in the desired range (0.008-0.012 inches) was achieved with nominal

power densities. Uniformity of the depth of penetration along the weld was also improved.

5.4.4 2D Joining Experiments

Following the optimization experiments described above, bond samples

having a "2D" geometry were prepared. These samples were made from platelet stacks residual

from the forming studies of Task 1.3; specifically from stacks that had been through the first

forming operation of the two step forming process. The resultant samples have a "converging"

and "diverging" contour and essentially form a longitudinal section of the area of a joint between

adjacent panels in a 40K sized formed platelet liner. For simplicity, the samples were taken from

the frame portion of the panels and did not contain any channels. A photograph of a sample of

this configuration is shown in Figure 5.13. This sample configuration allowed evaluation of the

ability to laser weld a seam while traversing along the converging and diverging contours.

Two such 2D samples were prepared with the developed processes and laser

weld assembled. Previous laser weld experiments had shown the validity of welding in an attitude non-perpendicular to the surface as would be encountered in the convergent and divergent

areas. This greatly simplifies the motion, and therefore the complexity, of the laser head as it

does not have to articulate as it traverses the joint path. Such a motion was employed for the fabrication of these and all subsequent bond samples.

Following laser welding of the "ID" and "OD" longitudinal seams, the joint ,-

ends were welded by EBW and the samples were then HIP processed. Subsequent sectioning

and examination revealed that diffusion bonding had not occurred. Photomicrographs showed

that etching and plating parameters provided bondable interfaces. Laser weld depth was as

desired and weld quality was excellent. The quality of the EB welds at the sample ends was

questionable and considered to be the source of leaks that would have inhibited the bonding.

Problems with the EB welds were particularly evident at the comers of the part where the laser

and EB welds overlap. Cracks, pits, expulsions and excessive comer erosion were observed.

RPT/G0114.119 108 October 5, 1992
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109
AdditionalEB weldexperimentswereperformedto optimize the EB welding

process. Changes investigated included evaluating different types of EB weld machines and the

use of start-up and run-off tabs. All previous joint samples had been welded using high

voltage/low amperage type welders. The advantage of using this type of welder is that they have

line-of-sight capability and the interface can be easily located. This type of machine also

generally produces narrow, deep welds. No run-off or start-up tabs had been used to date. Weld

samples were prepared to evaluate a low voltage/high amperage EB welder and the use of run-off

and start-up tabs. The low volt/high amp EB welder generally produces a wider beam shape that

was thought to potentially provide better seal welds.

EB weld optimization experiments consisted of developing weld parameters

that would provide a bead of the nominal dimensions shown in Figure 5.14. Figure 5.15 shows

the sample configuration. Start-up and run-off tabs were used to eliminate the transient condition

at the edges of the part as the electron beam traverses the part. Visual examination revealed a

small expulsion at the trailing end of the joint at the comer of one sample. This was due to a

small gap between the run-off tab and the sample edge. Subsequent longitudinal sectioning

(Section A-A, Fig 5.15) showed excellent cross over of the EB weld with the laser weld, even at

the comer where the expulsion had occurred. The results of the experiment were considered

satisfactory and the feasibility of the approach demonstrated. All subsequent samples employed

start-up and run-off tabs for all welding, including laser welds.

Two additional 2D samples were prepared and welded with the improved

processes described above. The welds were inspected under high magnification and no potential

leak paths were identified. The samples were then HIP processed. These samples were subsequently sectioned and evaluated. One sample showed 100% bonding; the other showed no bond.

Cross sections of the samples are shown in Figure 5.16. Both samples had been processed at the

same time, using the same methods. No record of any anomaly exists that would explain the success of one sample and the failure of the other. Examination of the cross sections of the nonbonded sample showed that pre-bond processing was adequate to obtain a diffusion bond; this

lead to the conclusion that an undetected leakpath existed, preventing the HIP pressure from

applying a bonding load. These results lead to the conclusion that visual examination of welds

was inadequate to fully assess their integrity and assure leak free joints.

Concurrent with the fabrication of the various bond samples, a method was

being sought to non-destructively assess a bond joint. A method that proved very successful

was X-ray or radiographic examination. A radiogrfiph of the two 2D samples discussed above

appears in Figure 5.17. The joint in the non-bonded sample is readily visible, while the joint in

RPT/G0114.119 1 1 0 October 5. 1992
0.010,n. JEB ;;;In.

Figure 5.14. EBW Bead Dimensions

Start-Up Tab

EB Joint

Run-Off Tab

Laser Weld

(2 Places)

Figure 5.15. Sample Configuration

111
t_o

• Sample Shows Distinct Lack Of Bonding • Sample Shows 100% Bonding

(Relative Rotation Occurred During Mounting)

• Leakage Suspect

Figure 5.16. Photomicrographs of 2D Bond Samples
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the bonded sample is not. This method continued to be employed for detecting the presence of a

bond in subsequent samples.

In order to improve bond reliability, with weld joint leakage being the suspect

failure mechanism, a means to detect and measure leakage was required. Such a means is shown

in Figure 5.18, wherein a leak check port that connects tO the joint to be bonded has been incorporated in the sample. Two such samples were prepared utilizing the procedures previously

developed. Following laser welding of the longitudinal joints and EB welding of the joint ends,

a leak test tool was installed on the samples and connected to a mass spectrometer leak test

instrument. The samples were then placed in a nylon bag flooded with helium. Neither sample

showed any indicated leakage above the background of 2.0 x 10-10 scc GHe/sec. Closeout of the

leak test port was made by EB welding a small button of ZrCu into the port counterbore. This

final closeout weld was then leak tested. The EB weld chamber was back filled with He prior to

removing the samples. The samples were then immediately placed in a bell jar, which was

evacuated through a mass spectrometer. Both samples indicated a leak rated of 10-6 scc GHe/sec

initially, but it quickly decayed to 10-7 scc GHe/sec. Both samples had overlapping platelet

edges which could entrap He to give the initial indication noted. Since both parts reacted

identically, it was felt that both were leak free. At this point both samples were HIP processed.

Following HIP processing the two 2D samples employing the leak check

ports were sectioned and metallographically examined. Figure 5.19 is a reproduction of photomicrographs taken from each of the samples. As can be seen, 100% bond was achieved in both

of the samples. This experiment, and the ones preceding it, showed the importance of leak tight

seal welds to successful bonding. Of equal importance is the testing of the joints to assure that

they are leak tight prior to the HIP operation.

5.4.5 3D Panel Joining Demonstration - Task 1.7

This task was undertaken to demonstrate the ability to edge join 3D formed

platelet liner segments together, as would be required in the fabrication of a functional liner. Tlae

developed and demonstrated diffusion bonding techniques described above were selected as the

joining process to be used for this 3D demonstration. The 90 degree 40k basic panel design of

Task 1.3, the forming task, was chosen as the design of panels to be joined. For simplicity sake

two panels were to be joined, instead of the requisite four panels of an entire 40k assembly.

The design of panels produced and iterated in the forming experiments

provided an inadequate land for edge joining. Further iteration of the basic 40k panel design was

required to provide panels with acceptable lands. The design and forming of these panels is

114

RPT/G0114.119 October 5, 1992
Leak Test Po_

L_h

83

r _

o

Z dh

N :5'.::

rni _

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13.6.12

_Figure 5.18. 2D HIP Bond Samples With Leak Test Capability
Bonded Joint (100% Bond)

Sample 1 Sample 2

Figure 5.19. 2D HIP Bond Sample Sections
discussed in detail in the forming section of this report and will not berepeated here. The design

produced an acceptable land for the joining demonstration.

Eight formed panels of the iterated design (PN 1206530) were fabricated.

The panels were then setup on the edge trim/inspection/weld fixture and, with the aid of the

OGP optical CMM, a "best-fit" average cutting plane was established. Two mating panels were

then wire EDM trimmed along this established plane. The EDM process utilized the optimized

parameters established in the 2D joining studies. Post EDM measurements confirmed the cuts

were made as desired, with a resulting minimum "half-land" thickness of .020 in.

Following the trimming process, the panel edges were etched and the

bonding aid applied. Again the previously established procedures were followed. The panels

were then fixtured and the edges laser welded together. Figure 5.20 shows the laserwelding in

process during the assembly of the two panels.

The laser weld joint, which provides the primary seal, was helium leak

checked through it's leak check port with a mass spectrometer type leak detector. The leak check

port design was identical to that of the previous 2D samples as shown in Figure 5.18. Following

leak testing of the primary seal weld the leak check port was closed out by EB welding in a disk

shaped closure. Visual examination of the weld showed an area of the joint that was not fully

consumed and large depressions caused by a staking operation used to keep the closure from

moving during welding. The non-consumed area was rewelded; the depressions remained a

source of concern over potential leakage. Following the reweld operation, the EB chamber was

backfilled with helium. The assembly was then removed from the EB chamber and placed in a

bell jar connected to a mass spec leak detector. No indication of leakage greater than

background (5.0 x 10-8 ccs) was noted. The assembly then underwent the prescribed HIP bond

process. Photographs of the assembly are shown in Figure 5.21.

Upon return to APD the part joint was radiograph inspected and the joint was

visible, indicating bonding did not occur. As a result of the previous work, leakage was the sus;_

pected cause of the failure to bond. To assess potential leakage, a hole was drilled through the

leak check closure into the leak check port circuitry; a tube was brazed into this hole. This

allowed leak testing of not only the primary seal weld (laserweld) but also the closeout port EB

weld as well.

The leak check revealed a leak in the port closeout weld. The leak coincided

with a small circumferential crack in the center of the EB weld. The crack was not visible after

the original welding of the joint. Two leaks and coincident cracks were also detected on the ID

RPT/G0114.119 1 17 October 5, 1992
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Assembly O.D.

Figure 5.21. Joining Study-3D Sample
laserweld downstream of the throat region. These cracks were not visible immediately after the

leak check tube braze operation, the last time the welds were inspected. The part saw

considerable handling, including an edge milling operation and numerous show-and-tell exposures during this period. It was conjectured that the cracks on the ID laserweld were a result of

handling damage and were not present during the HIP operation.

The crack noted in the EB closeout was conjectured to have occurred during

the HIP operation. It was believed that the closeout button was not fully seated, allowing the EB

weld to be stressed during the HIP. This coupled with potential residual stress in the weld itself

led to the formation of the crack. When the crack formed, allowing the HIP gas to enter the joint,

the pressure differential causing the stress was eliminated and the crack propagated no further.

When the HIP gas entered the joint the forces required for diffusion bonding of the joint interface

were also eliminated, thus the joint did not bond.

This assembly, which became known as 3D Demo SN01 assembly, was subsequently reworked by laser weld repairing the noted cracks and EB weld closeout of the leak

check tube. The assembly was taken through a repeat of the HIP operation.

Visual inspection of the SN01 assembly showed a positive indication of the

success of the HIP bond operation in the collapse of the wails of the leak test tube and of the

walls of the leak test port. X-ray examination revealed the joint line to no longer be visible.

Metallographic specimens were removed from the forward end and from the throat area of the

joint. Copies of photomicrographs of these specimens appear as Figures 5.22 and 5.23. Review

of these specimens indicate an estimated 90 to 95% bond. This is considered exceptional when

considering that the part saw four thermal cycles beyond 1700-F; these being the first HIP process, which included the solution treat operation, and the three braze cycles required to successfully braze the leak test tube in place.

Figure 5.23, the section through the throat of SN01 assembly, shows an offset

in the joint between the two panels making the assembly. The panel edge on the right of the .._

photo is the nominal (planned) 0.020 inch thickness; the panel edge on the left is 0.018 inch

thick, thus causing the offset noted. This is consistent with the expected joint prep machining

tolerance. There is another offset of note in the vertical, or radial, direction. This measures to be

.003 inch and again is consistent with expected assembly tolerance.

Concurrent with the evaluation and rework of 3D Demo SN01, a second

assembly, designated SN02, was fabricated. Processing of this assembly was identical to SN01

with some notable exceptions. A change made in the edge prep process made for improved bond

RPT/G0114.1 I9 1 20 O_'o_r 5, 1992
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cq
Land

Joint

Platelet Bonq

Joint (Typ)

Laser Weld

Gas

Side Wall

Figure 5.23. 3D Demo SN01 Assy - Throat Land Cross Section

122
aid application. The change dealt with combining the edge etch operation with the bond aid electroplating operations. This change was incorporated in the Fabrication baseline.

As a result of the problems encountered with the SN01 leak check port closeout button, a change in configuration was incorporated. The button contained a counterbore to

better accommodate the residual stress of the weld and to provide compliance during the HIP

operation. Additionally, greater care was taken in the deburring operation to assure that the button could fully seat in the port. The effective EB weld depth was also increased in an effort to

increase the strength of the joint. Even with these efforts some "rocking" of the button was still

evident after installation and prior to welding.

The assembly was processed through the HIP operation and subsequent!y

examined. Visual inspection of the walls of the leak check port did not show collapse. This led

to concern over the success of the HIP bond operation. Inspection, under magnification, revealed

two small cracks in the EB weld of the leak check port closure. No cracks were visible in the

laser seal welds of the joint itself. As all the welds were 100% inspected prior to the HIP operation, it is again conjectured that the cracks in the closure weld occurred during the HIP process.

The changes made to the joint configuration between assemblies SN01 and SN02 were not

effective in solving this recurring problem.

A metallographic specimen made from the pre-weld sample of the closeout

weld of SN02 revealed cracks at the root of the EB weld. Figure 5.24 is a copy of photomicrographs taken from this specimen. The cracks visible indicate that the weld is less ductile than

originally believed. While these cracks were of concern, as they affect the ability to successfully

complete the bond operation, they are not in the functional portion of the assembly and, in

themselves would not impair the function of a formed platelet liner.

A decision was made to repair SN02 assembly and reprocess it through the

HIP bonding operation. As the known cracks were in the closure weld and these were believed

to be the only cracks, an attempt was made to just weld over the cracked weld areas. This was ,--

not successful; the added shrinkage from the reweld caused a crack to appear in the adjacent laser

weld joining the two panels of the assembly. At this time it was decided to remove the closure,

re-leak check the assembly, repair the laser welds and re-install a new closure prior to HIP processing.

Review of the closure cracking problem and the alloy involved led to the

recommendation to replace the ZrCu closeout button with OFHC material. It was felt that the

ZrCu-to-ZrCu EB weld previously made was brittle due to the presence of the zirconium in the

123

RPT/G01 I4.119 October 5, 1992
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c_
alloy and its migration to the weld zone and HAZ. Replacement of one of the components contributing to the weld melt with OFHC could reduce this susceptibility to cracking.

The SN02 assembly was reworked per plan and again HIP processed. Post

HIP inspection, including both visual and X-ray, revealed that again bonding did not occur. It

was believed that again a leak in a weld was the cause of the problem, though this time no visible

crack in any weld was apparent post HIP.

Because of the success of SN01 3D demo, and a presumed understanding of

the causes of the problems with closeout welds, a decision was made to place the SN02 assembly

on hold and use it for future process development work. This would be on an as-required basis.

As a result of work performed during this task, the preceding task and other

related APD efforts numerous changes were incorporated in the Phase B 40K design. These

dealt mainly with improved methods for leak checking, making the leak check port closeout and

for assuring that the assembly was leak tight prior to the HIP operation. The basic processes

required for affecting the edge diffusion bond were incorporated as they were developed during

the Phase A effort.

5.5 CONCLUSION

The study resulted in the selection of diffusion bonded land joints obtained by sealing

the prepared surfaces of the joint periphery with laser welding and subsequently Hot Isostatic

Processing (HIP) the assembly. This provides an all-diffusion-bonded assembly that is essentially a monolithic structure. Processes developed to affect the panel to panel diffusion bond

included surface preparation, ZrCu laser welding, the means for leak checking the laser seal

welds, the final closeout of the leak check circuitry, and an NDE method (X-ray) suitable for

detecting the presence of a diffusion bonded joint.

At the conclusion of this study it was felt that the process chosen, though demonstrated with flat, 2D and 3D samples, had not been developed to the full extent required for reli-'-

able implementation. Questions associated with maintaining leak tight seal welds throughout the

HIP processing remained. Planned work on the next program phase was intended to further the

understanding of the problem and its resolution.

RPT/G0114.119 125 October 5, 1992
6.0 FABRICATION PROCESS DEFINITION

6.1 INTRODUCTION

The processes developed in the forming and joining Phase A tasks provide the basis

for the fabrication of a formed platelet liner. The process definition task took the information

provided by the previous tasks and combined it with other necessary processes to develop a process baseline for the fabrication of an operational 40k sized formed platelet liner. The actual fabrication of this liner was performed as part of Phase B of this contract.

6.2 OBJECTIVE

The desired outcome of this task was a baseline fabrication approach that could be

used for the production of a hot fireable 40K formed platelet liner.

6.3 APPROACH AND DISCUSSION

The basic formed liner processes were developed from the results and recommendations of the Phase A forming and joining studies. These were combined with standard processes

for the fabrication of platelet hardware and conventional chamber liners. APD engineering, manufacturing and materials and process specialists were enlisted to develop the overall plan and to

provide required process details.

A standard APD manufacturing flowchart was chosen as the vehicle for displaying

the required processes for the fabrication of the 40K formed platelet liner. This flowchart

appears as Figure 6.1 and 6.2. A legend explaining the nomenclature of the flowchart appears as

Figure 6.3.

The flowchart displays the life of the liner from the design stage through assembly of

its segments, including heat treatment to obtain optimum properties. The operations following

those shown are those that are required to complete the assembly of the platelet liner into a st_-

turally adequate and properly manifolded combustion chamber.

: 126

RPT/G0114.119 October 5, 1992
LINER ASSEMBLY

t_

..j

..............,. . ,,.......,..................,............

::::::::::::::::::::::::::::::::::::::::::: :::::::-:::::::: ::: :::::::::::::::::::::::::

010 I

DESIGN

PLATELETS

Apo I

PRODUCE I I FABRICATE L

NEGATIVES _-_ PLATELETS F

,,._. I ] I ,.'o I /

olo I

ISSUE PLATELET

STOCK

APo I

HIP

PANELS

APD I

II

_ J I I - i

POLYMER I I COLD

_.. I I FORM

rILL _1 PANEL

A_o I I I ,.0 I

oo i /

CLEAN & APPLY BOND I--

AID /

,_° I 1

%'ow FORMING

FRAME

APD I

ASSEMBLE

PANELS

APD I H

DIFFUSION

BOND

APD I

110 I

REMOVE

POLYMER

& CLEAN

Ap° I

12o I

RESTRAINED

ANNEAL

APD I

Figure 6.1. Process Definition - 40K Liner, Sheet I of 2
LINER ASSEMBLY

__ 13o I

MACHINE

LEAK CHECK

PORT

APD I

H .o I t

WIRE EDM

PANEL EDGES

O.P. I

ETCH

EDM'ed

EDGES

APD I

1. I

CLEAN &

APPLY BOND

AID TO EDGES

APD I

t,J

0o

,70 I

ASSEMBLE &

LASER WELD

PANEL EDGES

o.P. I

/

1. I loo I II I

EB WELD HiP BOND

PORT

CLOSEOUT LINER ASSEMBLY

O.P. I O.P. I

.o I

NIP SOL'N TREAT

AND AGE

o.p. I

Figure 6.2. Process Definition - 40K Liner, Sheet 2 of 2
FPL 40K CHAMBER ASSEMBLY

FLOW CHART LEGENDS

TYPE

1 RECEIVING

2 IN-PROCESS

3 RNAL

4 SOURCE

RESPONSIBILITY

MAKER @

EXAMPLE

2

DM# PT°

FIT"

MEANING •

MAKER RESPONSIBILITY

IN-PROCESS INSPECTION

SAMPLE DIMENSIONS

100% PENETRANT

INSPECTION

100% RADIOGRAPHIC

INSPECTION

INSPECTION/TEST

PT PENTRANT

FIT RADIOGRAPHIC

AT ACOUSTIC EMISSION

ET EDDY CURRENT

LIT ULTRASONIC

MT MAGNETIC PARTICLE

PF PROOF

LK LEAK

BT DURST

VC VISUAL

DV DATA/OPERATOR VERIRCATION

DM DIMENSIONAL

WS WITNESS

EL ELECTRICAL

CL CAUBRATION LAB

Wl WELD INSPECTION

SH SHIPPING

LT LABORATORY TESTING

HT HARDNESS

ET ENVIRONMENTAL TESTING

GA GAGING

FL FLOW

_'THOO

* 100%

# SAMPLE

& WITNESS

~ SPC

@ AUDIT

Figure 6.3. Flowchart Legend
7.0 SILVER AIDED BONDING

7.1 INTRODUCTION

Diffusion bonding of ZrCu platelets requires the use of a bond aid at the platelet-toplatelet interface. An aid is required due in large part to the reactive nature of the zirconium in

the alloy. Zirconium oxide readily forms on the free surface of the platelet and will inhibit the

diffusion bonding phenomenon. In order for effective diffusion bonding to occur, the surface

oxides must be removed or chemically reduced in a cleaning operation and the oxide-free surface

protected. This surface is most easily protected with a material that can be readily deposited on

the surface. This material, or "bond aid" as it is known, must in itself form surface oxides that

are easily reduced in the bond furnace environment or that are soluble in the bond zone. It must

also be soluble to some extent with the base material. These are the basic requirements of a bond

aid; additional considerations include affects on the base material. An example of these

considerations are bond zone alloy constituents, concentration and phase which in turn affect the

mechanical and physical properties of the bonded assembly.

One of the physical properties of concern with a cooled combustor liner is the thermal

conductivity of the liner material. When a liner is constructed of diffusion bonded platelets the

thermal conductivity perpendicular to the bond lines must be considered. The presence of a bond

aid with a conductivity lower than that of the parent material will lower the conductivity of the

bonded part. Depending upon the ZrCu diffusion bond process and bond aid parameters

selected, a reduction in conductivity from that of wrought ZrCu of as much as 10% to 15% is

witnessed perpendicular to the bond lines. Parallel to the bond lines there is no reduction in

conductivity.

Employing an alternate bond aid could reduce or negate this thermal conductivity

reduction. Silver was thought to be a viable candidate because of its solubility in copper, its high

thermal conductivity and readily reduced oxides. As such, silver was selected as the bond aid for

this study.

7.2 OBJECTIVE

The objective of this study was to identify and develop the processes required for diffusion bonding ZrCu platelets utilizing silver as a bonding aid. This development included prebond, bond and post-bond processing to allow optimization of bonded material properties. The

130

RPT/G0114.119 October 5, 1992
study was intended to provide sufficient data to allow design of combustor liners with this new

bond process.

7.3 APPROACH

A program was adopted based on the design of experimentation philosophy. In this

program quality optimization techniques were utilized. A Taguchi array was defined to reduce

the number of test specimens required to evaluate the multiple processing alternatives of interest.

The key parameters which were investigated were bonding temperature, bond aid thickness, and

thermal post processing. The levels, or number of variations, examined for each of these

parameters were three, two and three, respectively. The chosen selection criteria was tensile

strength at room temperature and at 1000-F; with a higher value considered better.

7.4 DISCUSSION

7.4.1 Taguchi Array

A modified L 18 Taguchi array was chosen for evaluating the selected process

factors. A copy of this array is shown in Table 7.1. The factors and their selected levels are

defined in Table 7.2.

7.4.2 Sample Preparation

Six different bond blocks, designated Blocks A through F, were fabricated for

this study. The blocks were constructed from 60 pieces of 5.0 inch x 5.0 inch x 0.017 inch ZrCu

platelet stock sandwiched between two 4.5 inch x 4.5 inch x 0.90 inch CRES end plates. The

end plates provided grip length for tensile specimens subsequently taken from the bond blocks.

All platelet stock and end plates were plated with the appropriate thickness of silver for that

particular block as specified by the test matrix.

Following plating, which was performed by an outside vendor, a cleaning

operation was required to remove visually apparent surface oxides. Considerable effort was

required to identify and test an adequate cleaning method. The selected method utilized a commercially available tarnish remover: Noxon Quick-Dip silver cleaner, American Home Products

Corp., Cranford, New Jersey.

After plating and cleaning, the six individual bond blocks were assembled

and bonded per the test matrix. The blocks were then cut into 1/2 inch x 1/2 inch x 3 inch pieces.

Selected pieces, identified by their block letter and location in the block as shown in Figure 7.1,

RPT/G(I114.119 131 October 5, 1992
rn

C_

C_
TABLE 7.2

FACTORS AND LEVELS FOR TAGUCHI ARRAY

Factor Level

1 AgThk Thick

2 Bond Temp Low

3 Diff Cycle? Yes

4* Diff&SOLI'N A

5 Age Temp Low

Thin

Med High

No Yes (2 Levels)

B C

Med High

6 Age Time 16,8,4 hr 8,4,1 hr 8,4,1 hr

A Long With HIP

B Long Without HIP

C Short With HIP

RPT/G0114.119 133 September 30, 1992
J_

4 1/2" Ref

/////////

1 2 3 4

8 9 10 11

15 16 17 18

22 23 24 25

8 7J

12 13 14 /

19 20 21 /

26 27 28 /

29 30 31 32 33 34 35

36 37 38 39 40 41 42

43 44 45 46 47 48 49 /

1_8,14"//////i///

_--I_ 1/8"- 1/4

Typ

M7/D59/FPFR-1

Note: "X" Indicates Block Letter Designator

Figure 7.1. Bond Block Sample Identification

134
'L

)',

went through the post-bond processing as specified by the test matrix and summarized in Tables

7.3 and 7.4.

7.4.3 Tensile Tests

Samples from the as-processed specimens were machined into tensile bars

and subjected to either room temperature or 1000 degree F tensile tests. The results of this

testing are displayed in Table 7.5. Ultimate strength, 0.2% yield strength, elongation and

reduction in area are tabulated for each sample tested. Several samples broke either during

machining or setup and thus no data was available.

In summary, the Taguchi analysis indicates that a low bonding temperature is

preferred with a thin silver bond aid thickness and post-bond thermal processing should include a

long diffusion cycle and a HIP during the solution ageing. The greatest influence on tensile

strength was the bond aid thickness. Some questions were raised concerning the handling of the

high bonding temperature samples. Numerous samples exhibited low ductility and inconsistency

in the data obtained.

Although the Taguchi analysis provides information for the understanding of

influencing factors for process optimization, it does not in itself indicate whether the results are

acceptable or even promising. To assess this it is necessary to compare the results to the known

standard. Comparison of tensile strengths developed by the two systems show a significantly

lower strength for the silver aided bonds. This effect is illustrated in Figure 7.2 which shows a

comparison of silver aided v.s. typical standard aided bond ultimate tensile strengths at 1000

degrees F. The very best silver aided bond exhibited only 80% of the strength of the standard

process. An even more striking comparison is the ductility provided by the two systems. The

best silver aided bond tested at 1000 degrees F had a reported 1% elongation. This compares to

12% for the standard aided bond. The reason for the poor performance is evident from

microstructural analysis.

7.4.4 Metallographic Analysis

Specimens were sectioned, polished and analyzed. Unstained samples were

subjected to microprobe line scan analysis to characterize the distribution of copper, silver and

zirconium. Fractography was conducted on a scanning electron microscope. Additional

characterizations of the fracture surface oxides were accomplished using the wavelength

spectroscopy capability of the microprobe. After optical microscopic examination, the

specimens were etched to show the underlying structure.

RPT/G0114.119 13 5 octo_r 5.1992
TABLE 7.3. SAMPLE PROCESSING MATRIX, BONDING POST-BOND

c_

,

LOW LOW

3 LOW

4 MED

_ MED

-'6 _ MED

7 HIGH

8 HIGH

9 HIGH

10 ILOW

11 LOW

12 LOW

13 _ MED

15 _ MED

16 HIGH

17 HIGH

18 HIGH

Diffusion/Solution

None A "'" B L c

A-09, A-12, A-30, A-33

A-10, A-13, A-31, A-34

A-17, A-20, A-38, A-41

B-09, B-12, B-30, B-33

B-10, B-13, B-31, B-34

C-17, C-20, C-38, C-41

B-17, B-20, B-38, B-41

E-10, E-13, E-31, E-34

E-09, E-12, E-30, E-33

E-17, E-20, E-38, E-41

F-09,F-12, F-30, F-33

F-10, F-13, F-31, F-34

F-17, F-20, F-38, F-41

C-10, C-13, Co31, (2-34

C-09, C-12, (2-30 (2-33

D-09,D-12, D-30, D-33

D-10, D-13, D-31, D-34

D-17, D-20, D-38, D-41
i!  ̧

ID

1

2

3

4

5

TABLE 7.4. SAMPLE PROCESSING MATRIX, POST-BOND AGE

A

LOW / 16 LOW / it LOW / 4

A-09, A-12, A-B0, A-33

6

7

$

9

I0

11

12

13

14

15

16

17

B-t?, B-20,B-3_B-4_

C-17,C-20,C-B_C41

E-10, E-13, E-31, E-34

9

10

11

12

13

14

15

16

17

15

_ ID"

1

2

3

4

5

6

7

15

16

17

15

F-17, F-20, F-3$, F-41

M_D / 8 MED / 4 MED / 1

D-17, D-20, D-3_, D-41

HIGH / 8

B--09,B-12, B-30, B-33

HIGH / 4

$

9 C-09, (3-12,C-B0, C-33

10 D-09, D-12, D-30, D-3B

11

12

13

14

F-09, F-12, F-30,F-33

E-17, E-20, E-38, E41

HIGH / 1

A-17, A-20, A-M,, A-.41

137
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ellill

I'-

ill

.Jm

(/) Z

uJP

uJ

-Im

loo

t"¢3
u]

eO_

eU_

U)

e"

p.

4.e

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m

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LI=

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C3

20.0

15.0_

10.0_

5.0_

o0 _- ¢0

¢O <¢ ¢O

I I I

UJ U.

Ag Aided -""--_Ni Aided M7/D59/FPFR-1

Bar Graph Comparison of 1000°F Ultimate Tensile Strength of Best

Ag Aided Bond Development Samples With Typ STD Aid Block

Figure 7.2. Comparison of Bond Aid Performance

139
Typical room temperature tensile tests exhibited two failure modes corresponding to ductile and brittle failure. All room temperature samples which failed in a brittle

manner separated along the platelet bond interface. The ductile failures showed no tendency to

fail along these planes.

Metallographic sections of typical high temperature tensile specimens after

testing showed a single failure mode, that being a brittle failure. All IO00-F specimens exhibited

two common features: the bond interface is characterized by a line of particles along the interface

and many small cracks exist along the edges of the samples.

These particles appear to be residual intermetallics or oxides that create a

connected weak boundary across the sample and are thus susceptible to failure. This condition

appears to exist in all of the silver aided bond specimens produced. Note that no similar condition has been found in nickel aided bond assemblies or specimens.

7.5 CONCLUSIONS

The Taguchi analysis performed did provide an indication of the influencing

factors in silver aided bonding of ZrCu. Bond aid thickness appears to have the most influence,

with a thinner bond aid layer preferred. Bond temperature appears best at the lower values. Post

bond treatments under HIP conditions provide an increase in elevated temperature strength.

Tensile tests and subsequent metallography indicated a lack of strength and ductility

at elevated temperatures. This condition appears related to the micro-chemistry of the bond and

may be an unavoidable result of the combination of constituents of the parent material and the

silver bond aid.

Another disturbing condition was witnessed with this bond study. A high degree of

variability and poor bonds were seen for no apparent reason. This leads one to assume that standard processing techniques that are adequate for the current bond system may be inadequate for

the silver aided system. Further extensive development may be required to understand this prolYlem.

It is felt that improvements in the bond properties could be made with further experimentation and investigation of the silver aided bond process. However, the results to date, when

compared to the standard aided system, indicate that significant improvements are required

before silver can be considered a viable diffusion bond aid for ZrCu.

Rr'r/Go,,4z,9 140 October 5.1992
APPENDIX A

Platelet Design and Fabrication Processes

A-1

RPT/G0114.119-Aor) October 5. 1992
The platelet concept is a design and fabrication technique that can create compact

monolithic structures containing thousands of intricate, precisely located fluid flow passages.

Aerospace applications include high performance propellant injectors for large and small rocket

engines, complete multiple liquid rocket thruster assemblies, cooled nosetips for reentry vehicles,

transpiration cooled forebodies and radomes for hypersonic interceptors, sealed aircraft leading

edges for the National Aerospace Plane, fluidic circuits for aircraft engine controls, high

performance heat exchangers, and regeneratively cooled combustion chamber liners. Aerojet has

fabricated hundreds of different platelet devices since the technique was developed in 1964. A

summary of the thirteen different types of platelet cooling devices fabricated by Aerojet is shown

in Table A-1.

TABLE A-1.

AEROJET HAS FABRICATED THIRTEEN DIFFERENT TYPES OF COOLING

DEVICES USING PLATELET TECHNOLOGY

Device

Transpiration Cooled Chamber

Cooled Turbine Blade

Transpiration Cooled Nosetips

Heat Pipe Wicks

Heat Exchangers

Metallic Radome

Scramjet Strut

Flame Arrester

Convectively Cooled Chamber

IR Windows

Forebodies

NASP Panels

Leading Edges

Application

Rocket Engine Cooling

High Temperature Turbine

Re-Entry Vehicle Nosetip Cooling

Low AP, High Flux Wicks

Cooling or Heating 02 or H2

Interceptor Vehicle Cooling

Cooled Structures in Hypersonic Airstream

H2 Tank Flame Arrester

Rocket Engine Cooling

Hypersonic Interceptor Vehicle Cooling

Hypersonic Interceptor Vehicle Cooling

Convective Vehicle Cooling

Cooled Structures in Hypersonic Airstream

Da_

1964-1990

1967

1968-1992

1968-1970

1976-1992

1983-1992

1983-1991

1984-1986

1985-1992

1985-1992

1986-1992

1986-1991

1988

Platelets are thin metal or ceramic sheets covered by a pattern of intricate through and halfdepth features. Structures are formed by stacking different sheet designs in a pre-determined

sequence, then diffusing bonding (in the case of metal sheets) or sintering (in the case of

ceramics) the assembly. Features line up vertically between platelets to form fluid distribution

and control circuits. The design concept is shown in Figure A-1. Materials used successfully in

. RPT/G0114.119-A0p A-2 October 5, I992
Depth Etch

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Figure A1. Platelets of Different Designs are Stacked and Bonded to

Create a Single, Monolithic Fluid Control Device

A-3
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platelet devices include 304L and 347 stainless steel; Inconel 600; Nickel 200; 1100, 3003, and

5052 aluminum; commercially pure, 6A14V, and Beta 21S titanium; copper; zirconium-copper;

Narloy Z; molybdenum; beryllium; and silicon nitride.

Platelet designs are not limited to flat, 2 dimensional applications. Metallic platelet

structures can be post-processed after diffusion bonding to form more complex shapes. For

example, the flat formed platelet liner chamber panels are pressed in a forming die after diffusion

bonding, to create final combustion chamber curvatures.

Platelets are formed in one of two ways. In the photo-chemical machining process, patterns

are transferred onto a photo-resist coated sheet stock surface using photographic techniques.

Sheets are then spray etched with acid to remove platelet regions previously exposed to light.

Etching from one side only results in partial penetration, depth-etched features, while etching

from both sides creates through-holes. In the laser cut process, a high intensity laser beam erodes

material and creates through-holes. A schematic of each process is shown in Figure A-2. Both

processes are currently used by Aerojet and have certain benefits. Chemical etching is fast since

all features are created simultaneously. In addition, chem-etching allows depth-etched design

features. Laser cutting advantages include smaller holes in thicker platelets, straight edges and

angle holes.

Platelet fabrication begins in the CAD room (Figure A-3). After defining flow feature

geometries by design and analysis techniques, exact platelet dimensions are defined on Aerojet's

CAD system. Design files are then electronically transferred to the negative photo plotting

station. An engineer translates platelet dimensions into laser scanner commands (Figure A-4).

Regions of platelet exposure are light on the negative; masked platelet regions must be dark. The

laser beam scans and photographically exposes only the dark regions on mylar film, which is

then developed to reveal the platelet image. These dark areas become etched regions on the

platelet. An example of a developed photographic master formed by the laser scanner is shown

in Figure A-5.

After completing all photo masters fabrication moves to the platelet shop. Sheet stock of

appropriate thickness is cleaned (Figure A-6), then coated with a light-sensitive film photoresist

(Figure A-7). Photographic negatives are attached to both sides of the sheet stock, then exposed

to light (Figure A-8). After removing the negatives each sheet is developed in a chemical bath,

then rinsed to wash away unexposed photoresist.

RPT/G0114.119-App A-4 October 5. 1992
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After forming all featuresplateletsleavetheetchmachineandarerinsed to stop chemical

action and remove residual photoresist. A partial set of completed formed platelet liner platelets

are shown in Figure A-10. Platelets are then sent to the inspection station. Computer aided

inspection techniques allows 100% inspection and measurement of critical features (Figure All).

After inspection completed platelets are cleaned, and if necessary flash-coated with a bond

aid material (Figure A-12). Platelets are stacked under clean room conditions to prevent particle

contamination of the intricate flow passages (Figure A-13). Stacked assemblies are then

diffusion bonded under heat and pressure, either in a press (Figure A-14) or by hot isostatic press

(HIP) techniques. Completed parts (Figure A-15) are post-processed to remove identification

tabs, stacking pin holes and supporting flashing. Further processing may include additional

machining, welding fittings or forming (Figure A-16).

A-12

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A-20