NASA Technical Reports Server (NTRS) 20160010288: TEM Analysis of Interfaces in Diffusion-Bonded Silicon Carbide Ceramics Joined Using Metallic Interlayers

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by  NASA Technical Reports Server (NTRS)

ICACC ‘16, Daytona Beach, FL, USA January 26, 2016,
TEM Analysis of Interfaces in
Diffusion-Bonded Silicon Carbide Ceramics
Joined Using Metallic Interlayers
1 T. Ozaki 1 Y. Hasegawa

2 H. Tsuda 2 S. Mori
3 M. C. Halbig 4 R. Asthana
5 M. Singh
1Technology Research Institute of Osaka Prefecture, Osaka, Japan
2Osaka Prefecture University, Osaka, Japan
3NASA Glenn Research Center, Cleveland, Ohio, USA
4University of Wisconsin-Stout, Menomonie, WI, USA
5Ohio Aerospace Institute, Cleveland, Ohio, USA
OPU
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outline
1. Introduction
properties and applications of SiC

2. Sample preparations used for diffusion bonding

Substrates : SA-Tyrannohex TM (SA-THX)
Interlayers : Ti-Mo foil
3. Experimental results
TEM and STEM images of substrates (SA-THX)
TEM and STEM images of diffusion bonded samples

4. Discussion about the microstructure of the formed

phases by diffusion bonding
the orientation relation between the precipitated TiC and Mo-Ti (SS)
5. Summary

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Developed for wide range uses
SiC is an attractive material
(not only as a monolithic material, but also in composites)
(high-temperature, extreme environment applications)
1. monolithic materials injector applications
1. Excellent mechanical properties
2. composites materials combustion liner,
2. Good oxidation resistance
nuclear and fusion reactor, turbine
3. High thermal stability
engine applications
exhaust
fuel
However,
geometrical limitations
hinder the wide use of SiC. It is difficult
to fabricate large, or complex shaped
components by Hot Pressing or CVD.
Therefore,
new advanced
© NASA methods are needed.
heat exchanger
Under those circumstances, one cost-effective solution for fabricating large,
complex-shaped components is the joining of simple shaped ceramics.
In this study, we are going to focus on
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diffusion b© oNAnSAd ing.
Mismatch of elastic modulus (E) and coefficient of thermal
expansion (CTE; α) between substrate and interlayer
We have to pay attention to mismatch of elastic modulus and CTE when we select interlayer material to join SiC.
10 (10-6K-1)
Elastic Modulus （E)
(GPa) 10 CTE (α) αTi
500
8
αSiC
8
） 400
1 αMo
- 6
K ΔE 6 Δα
300
6
-0 4 4
1 200
×
2 ETi 100 2
（
α ESiC
0 0 0
EMo
ETi ESiC EMo αTi αSiC αMo
Elastic Modulus CTE
115 450 329 8.4 3.2 5.1
Si N SiC W Mo Cr Ta Nb Ti V E α
3 4
Both E and CTE of Mo is closer to SiC than that of Ti .
Therefore, Ti-Mo bilayer that
‐ Ti and Mo have been used to join α‐SiC.
possesses both advances of Ti
‐ Better quality bonds formed with Mo than with Ti. and Mo is also very attractive.
But,
Therefore in this work, we
‐ Ti can lower the diffusion bonding temperature. utilize Ti-Mo as interlayers.
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Diffusion Bonding of a SA-THX using Ti/Mo metallic Interlayers
Used sample ＠NASA
Ti-Mo foil
SA-THX ...SiC fiber-bonded ceramics, UBE Industries
Ti-foil Mo-foil
Bonding structure
12.7μm
Mo 10μm Ti SA-THX // 10μmTi-12.5μmMo-10μmTi // SA-THX
Bonding process

Hot-press in 1200℃, 4hour, vacuum 30MPa
10μm Ti and 12.7 μm Mo
SEM image SA-THX
interlayer
parallel to SiC fiber
12.7μm
Mo
10μm Ti

Micro-crack
SA-THX
10μm Ti and 12.7μm Mo
interlayer
P産er技pe研ndicular to SiC fiber M.C. Halbig, et. al., Ceramics International41(2015)2140–2149
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Until now, the phases formed during diffusion bonding have been studied・・・・・.
(to join SiC-SiC using Ti interlayer)
M. Naka et al, Metallurgical and Materials Transactions, A; B. Gottselig, et al; J. European
28A(1997), 1385-1390 Ceramic Society, 6(1990), 153-160
Unfortunately, there has been little literature on TEM observation
(1)SEM observation (2)XRD measurement (3)Elemental analysis (4)Phase fraction measurement
of the phases formed during diffusion bonding.
Because, it seems very hard to prepare TEM sample
However,
from the bonded area. recently we successfully
Thinning more
obtained a clean, less-damaged, and precisely selected thin
by Ga ion
specimen from diffusion bonds by using an FIB.
Pick up the wall
Depositing carbon
Two parallel trenches
by manipulator
layer for protection
SiC SiC
Metallic
interlayer
10μm
Objectives

We diffusion bonded SiC and SiC (SA-THX and SA-THX)
using Ti-Mo foil metallic interlayer.
We carried out TEM and STEM observations with the diffusion
bonded sample prepared by FIB technique.

1. Evaluate microstructures of the diffusion bonded
SA-THX by TEM and STEM.

2. Characterize the complex microstructure in the
diffusion bonded area by TEM observation and
SAED analysis.
FIB and Cs-corrected STEM
Focused Ion Beam, FIB Cs-corrected STEM
（Hitachi FB-2200） （Hitachi HD-2700）
Checked the thin samples prepared by FIB.
Prepared thin samples for TEM and STEM.
Three-Observation mode:
SEM, BF-STEM and HAADF
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Fabricating procedure of the thin sample
（SIM image obtained by FIB）
① ②
position 1
SiC reaction reaction SiC 2
Mo
SA-THX layer layer SA-THX
W-depo（protection coating）
3
③ ④
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STEM observation of the FIB sample (HD-2700)
Position 1 （SiC-reaction layer） Position 2 （reaction layer） PoPsiotisointi o3n （ 1re （aScitCio-n反 la応ye層r-）M o）
T
SEM 3iS
Ci Ti Si C Mo-Ti
image 2 5 3 x TiC Mo-Ti
Ti Si C
5 3 x
Mo
HAADF
image
BF-STEM
image
Succeeded preparing the TEM samples in
the diffusion Bonded area.
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