Asthana, R.

Coddington, B. P.

Halbig, M. C.

Singh, M.

NASA Technical Reports Server

National Aeronautics and Space Administration 
Bonding of Silicon Carbide Based Ceramics using 
Particulate Reinforced Ag-Cu-Ti Alloys 
R. Asthana* 
University of Wisconsin-Stout, USA 
M. C. Halbig 
NASA Glenn Research Center, USA 
B. P. Coddington 
University of Wisconsin-Madison, USA 
M. Singh 
Ohio Aerospace Institute, USA 
.. . 
l\1~ 
. . ' j: :: 
. . ~ .. :STOUT 
. . lll' -111f 0 · WISC-ONSI 
36th International Conference and Exposition on Advanced Ceramics and Composites, 
Daytona Beach, Florida, January 22 - 27, 2012. 
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https://ntrs.nasa.gov/search.jsp?R=20150010196 2019-08-31T07:50:38+00:00Z
National Aeronautics and Space Administration 
Outline 
• Background and Introduction 
- Potential Applications 
• Experimental Details 
- SiC Brazing using Ticusil 
- SiC Brazing using TiCusil + SiC particles 
• Characterization 
- Optical Microscopy 
- Scanning Electron Microscopy {SEM) 
- Energy Dispersion Spectrometry {EDS) 
- Microhardness Measurements 
• Summary and Conclusions 
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Need for Joining and Assembly Technologies 
• Joining is an enabling technology for utilization of 
advanced ceramics and composites in high temperature 
applications. 
• Aerospace Systems 
- Aerospace and Space Propulsion Components (Combustor 
Liners, Exhaust Nozzles, Nozzle Ramps, Turbopump Blisks) 
• Non-Aerospace Systems 
- Nuclear Industries, Land Based Power Generation, Process 
Industries, Heat Exchangers, Recuperators, Microelectronic 
Industries (Diffusion Furniture, Boats) 
• The development of ceramic joining and assembly 
capability will allow the application of advanced ceramics 
and composites technology in a timely manner. 
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National Aeronautics and Space Administration 
Critical Need for Joining and Integration Technologie 
in Fabrication of MEMS Lean Direct Injector 
Previous joining approach 
using silicate glass resulting in 
plugged fuel holes and leaks 
in the SiC injector. 
.--~-==::::] 
Un-optimized diffusion bond 
using a 38 micron thick 
alloyed Ti foil for an 
interlayer. Microcracks and 
non-uniformity are seen . 
Key Technologies: 
Optimized diffusion bond 
using a 10 micron thick PVD 
coating for an interlayer. A 
uniform bond with no 
microcracking is observed. 
Above: Unbonded 1" SiC discs 
with a 0.65" diameter Ti 
coating on one of the discs. 
Below: Ultrasonic C-scan 
image of bonded discs. 
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National Aeronautics and Space Administration 
Technical Challenges in Bonding of Ceramics 
• Wetting of the Ceramic Substrate 
- Active Braze Alloys - Ti 
Contact Angle Between Ceramic and Liquid Filler Metal or Alloy 
Ceramic Filler Metal Temperature (oC) Contact 
Substrate or Alloy Angle (0 ) 
SiC Ag-28%Cu 930 160 
SiC Ag-35%Cu-1.5%Ti 850 10 
Nascimento et al. Cera mica 49 (2003) 178-198 
Liquid Metal 
h 
Liquid Metal 
Yl, 
Ll Ysv- Ysl 
cosu = -
Yzv 
• Residual stress due to differing CTE of substrate and braze 
Delamination and cracking in SiC substrate 
Control CTE of braze by dispersing SiC particulate 
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National Aeronautics and Space Administration 
Technical Challenges in Bonding of Ceramics to Metals 
• Residual stress due to differing CTE 
- Major problem in joining SiC to metal 
l'l E,,(" = 4.0 X IU 6fVC 
Cl E.._"''- 11.5 \ HI 6 !°C 
Stress cracks 
due to CTE mismatch 
SiC 
'- AgCuTi braze ·- ·· · 
Kovar ----1.!.!!!!!_ 
- Less severe in SiC-to-SiC joints but still important due to 
CTE mismatch between SiC and braze 
• Control CTE of braze by dispersing SiC particulate 
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National Aeronautics and Space Administration 
Background Information 
~ C/C brazed to Ti-6AI-4V using SiC particles (4.61Jm) in Ag-26.7Cu-
4.6Ti 
Qin and Yu, Joining ofC/C composite to TC4 using SiC particle-reinforced brazing alloy. Mater. Charact. , 61, 2010, 
635~639. 
~ C/SiC brazed to metals using (Ag-6AI)+Ti+C filler (as mixture of Ag, 
AI, Ti powders and short carbon fibers) 
Wang et al, Reactive composite brazing ofC1 SiC composites to Ti alloy with (Ag-6Al) +Ti +C composite filler 
materials, Mater. Sci. 
Techno!., 27(1), 2011, 49-52 
~ C/SiC composite joined to Ti using Ag-Cu-Ti braze containing short 
carbon fibers 
Lin et al, Joints of carbon fiber-reinforced SiC composites to Ti-alloy brazed by Ag-Cu-Ti short carbon fibers, J 
Mater. Proc. 
Techno!. , 189(1-3), 2007, 256-261 
Main Findings: 
- Particles and fibers reacted with Ti, forming thin TiCx layers 
- Particles and fibers randomly distributed in braze 
- Fibers preferentially aligned parallel to brazed interface 
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National Aeronautics and Space Administration 
Materials and Key Properties 
Materials: 
Y Substrate: CVD silicon carbide 
Y Braze matrix: Ticusil (68.8Ag-6.7Cu-4.5Ti, T L: 900°C) 
Y Braze reinforcement: SiC particulates (size: ~20 J,Jm) 
Ticusil 
SiC 
E 
(GPa) 
85 
466 
Oy 
(MPa} 
292 
Generic Property Data 
U.T.S. 
(MPa) 
339 
Thermal CTE Electrical 
Conductivity 6 Conductivity 
(W/mK) (x 10- m/m*K} (x106 /Om} 
219 18.5 . 29 
300 4.0* 
% Elongation 
28 
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National Aeronautics and Space Administration 
Experimental Procedures 
- Ultrasonic cleaning of SiC 
substrate in Acetone for 10 min 
- Ticusil powder mixed with 5, 10 
and 15 wto/o SiC particulates (-20 
IJm) and glycerin to dough-like 
paste 
- Paste applied using spatula and 
substrates sandwiched under 
200gload 
- Heated to 1 ooc above the braze 
liquidus temperature, isothermally 
held for 5 minutes 
- Mounted in epoxy, polished and 
characterized 
Ticusil + SiCP 
25.4mm 
100gload 
SiC 
SiC 
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National Aeronautics and Space Administration 
CVD SiC/Ticusil (0°/o SiCp)/CVD SiC 
www.nasa.gov 10 
National Aeronautics and Space Administration 
CVD SiC/Ticusil (So/o SiCp)/CVD SiC 
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National Aeronautics and Space Administration 
CVD SiC/Ticusil {1 Oo/o SiCp)/CVD SiC 
Location 1 
- . 
'' ' ~.,..'2Q1S ~. 1o(_OmmxS/):)1,'~ .. (3~[ IJJI~~I1J 1•/i 
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National Aeronautics and Space Administration 
CVD SiC/Ticusil {15o/o SiCp)/CVD SiC 
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Effect of SiC Dispersion on Joint Hardness 
(Ticusil Braze) 
SiC/Ticusii+SiCP/SiC Joint 
4000 ....--------.--------.-------r--------r---------r------, 
:::: Brc ze Region 
3500 , - .. ) 
4 .... -.-:..:. ~~,F-'~~ . ~ .\J ...-·y~-=~. ~~ . ~"'- ·~ .. .,. . , ', <.., ,.-: ~ . ;..,:::_~ - -~ .r· --'- ' 
. ' · ~·· ·....,. . ...-~ ~ !' . ' ·~ ..: . ', • 
3000 +-~· ~-=·=+======-~· ~~~· ~1~- j~~====~-~--~'~~ ---~ ~ L ..._ ' : "' ~, CVD iC i\ fj1t v[ SiC ~ 2500 +----~--~~---ri--r----+----+---~ 
c :~ . (jll ~ \ j f ~ · ~ ~ 
0 2000 +----~---~~. +: ~~~-r----+----+---~ 
b l : ~ ~1500 +----~---HI~\ ~~-~ ~i-r----+--+·-··~··• ~···~=~n~i l -~ 
g r:\ll ~ ~ rl
~ ' : j 1000 +----~---H----"-+--.......,_--r----+---+-=-r-------T~~~;:--tl \~ J , - -a- ::>'Yo ::>ILP Paste 
·.; fJ ~ - 10% SiCp Paste 
500 +----+----H-~.--~----+---+---+---~ v 0 +-~~~+-~~~~~~~~~~~-+~~~-+~~~~ 
- • - ::>% SiCp Paste 
--~-- .L5% SiCp Paste 
0 500 1000 1500 2000 2500 3000 
Distance Across Joint, 11m 
);;-- The small braze thickness allowed only a single indentation to be made 
within the braze. 
);;-- No measureable effect of SiC dispersion on joint hardness was noted 
www.nasa.gov 14 
National Aeronautics and Space Administration 
Projected CTE Decrease with SiC Dispersion in Braze 
Kerner's equation for volumetric CTE of a matrix containing particles: 
(1 I K m ) - (1 I K ) 
a == a V + a V - (a - a )V V [ P ] 
c m m P P m P m P (V I K ) (V I K ) (3 I 4G ) 
ac =volumetric CTE of composite 
am= volumetric CTE of matrix 
aP =volumetric CTE of particulate 
Vm, Vp =volume fractions of matrix and particulate 
Km,KP = Bulk moduli of matrix and particulate 
Gm =Shear modulus of matrix 
am = 55.5 X 1 o-6 K-1 
aP = 12.3 x 10-s K-1 
Km = E/[3(1-2v)] = 57GPa, E = 85 GPa, v- 0.25 
KP = 203 GPa 
Gm- 0.4E = 34 GPa 
60 
~ 50 
........ 
E 
~ 40 
w' 
tJ 30 
u 
'i: 
~ 20 
E 
:::s g 10 
0 
m p+p m+ m 
(E.H. Kerner, Proc. Phys. Soc., 869, 1956, BOB) 
------
I Base don Kerner' equation 
-
0 5 10 15 20 25 
SiC v/f,% 
At 15 v/f SiC in Ticusil braze, a 16% decrease is projected in the CTE of Ticusil 
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National Aeronautics and Space Administration 
Reaction and Interface Formation 
>- Formation of TiC and titanium silicides {TiSi2, Ti5Si3, 
Ti5Si3Cx) is thermodynamically feasible {aG<O) 
>- Based on aG calculations, TiSi2 and Ti5Si3 are less 
probable than TiC 
>- Titanium silicides could also form during solidification 
following SiC dissolution in braze and melt saturation 
with Si 
• 
www.nasa.gov 16 
National Aeronautics and Space Administration 
Microstructural Observations 
>- SiC particles are randomly distributed in Ticusil and well-bonded 
>- Evidence of reaction of Ti with SiC and Ti-Si-C phase formation 
at interface 
>- SiC particles with Ti-rich interface aid nucleation of Cu-rich 
secondary phases 
>- Loss of Ti in reaction with SiC particulates did not impair 
bonding with SiC substrate 
>- Reinforcing AgCuTi braze with SiC can 
- reduce the CTE mismatch and residual stresses 
- aid bonding 
- enhance braze strength 
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National Aeronautics and Space Administration 
Observations 
~ Loss in braze ductility from SiC dispersion and ability to 
accommodate stress may be compensated by CTE decrease 
~ Excessive addition of SiC particles may induce pores in the 
joint 
~ Fine SiC causes clustering, metal-starved cavities and sites for 
crack initiation 
~ At very high SiC content, more Ti in filler may be used up in 
reaction with SiC particulates, leading to thinner reaction layer 
at substrate interface and affecting the joint strength 
• • 
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National Aeronautics and Space Administration 
Bonding of Silicon Carbide-Metals {ongoing ... ) 
CusiiABA 
. . . .. 
95W 3.5Ni 1.5Cu 
Hexoloy-SA 
CusiiABA 
Mo 
CVD SiC 
Ticusil 
95W 3.5Ni 1.5Cu 
CVD SiC 
Ticusil 
Mo 
Copper ABA 
95W ~.5Ni 1.5Cu 
Copper ABA 
CVD SiC 
Mo 
• SiC brazed to SiC, Ti, W, Ni, and Mousing Ag-Cu-Ti and Cu-Si-AI-Ti brazes 
• Multilayer joints created to manage CTE induced residual stresses 
• SiC-to-metal joints created using diffusion bonding were also extensively 
characterized for fuel injector application 
www.nasa.gov 19 
National Aeronautics and Space Administration 
Brazing of SiC to Kovar and to Molybdenum with 
Cusil ABA Foii/Copper/Cusil ABA Foil 
Kovar I Cusil ABA I Copper I 
Cusil ABA I SiC 
Molybdenum I Cusil ABA I 
Copper I Cusil ABA I SiC 
Molybdenum - Copper 
Interface w/Cusil · 
SO.Opm 
20 www.nasa.gov 
National Aeronautics and Space Administration 
Shear Testing of SiC to Kovar and SiC to Molybdenum 
Joints with Copper and Cusil ABA Foil 
• Testing Conditions Load 
- Crosshead speed: 
O.Smm/min 
- Air 
- RT, soooc, 700°C 
SiC to Kovar SiC to Molybdenum 
35 35 
- - 3 Tests (± 1.56) ns ns 
~ 30 ll. 30 
3 Tests (± 1 .46) :E 2 Tests (± 1.29) 
- -5 25 
C) 5 25 C) 
t: t: 
e 20 
..., e 20 ..., 
en en 
t: 15 0 t: 15 0 
en en 
~ 10 ~ 10 
.... .... 
a. a. 
E 5 E 5 
0 0 
0 0 
0 0 
RT 500°C 700°C RT 500°C ?oooc 
2 1 www.nasa.gov 
National Aeronautics and Space Administration 
Summary and Conclusions 
• Ti containing active brazes offer excellent wetting of the 
SiC substrates. 
• SiC particulate reinforcements in Ticusil braze alloys can 
be used to reduced the thermal expansion and enhance 
braze strength. 
• Copper interlayers proved to be capable of absorbing 
residual stresses introduced from brazing and acted as a 
diffusion barrier preventing unwanted silicide and carbide 
formation. 
• Initial mechanical testing shows that Mo-SiC joints brazed 
with a copper interlayer are capable of high strength -
failure typically occurred within the ceramic. 
• 
www.nasa.gov 22 
National Aeronautics and Space Administration 
Acknowledgements 
• This work was supported by the Subsonic Fixed 
Wing Project of the NASA Fundamental Aeronautics 
Program 
• Bryan Coddington would like to thank LERCIP 
Program at NASA Glenn Research Center for summer 
research support 
• Rajiv Asthana would like to thank OAI and NASA 
Glenn for summer research support 
www.nasa.gov 23 


Bonding of Silicon Carbide Based Ceramics using Particulate Reinforced Ag-Cu-Ti Alloys

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