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Ultra-High Temperature Ceramics: Materials for
Extreme Environment Applications III
Proceedings
Spring 4-16-2015
Effect of Ni-Nb Interlayer Thickness on Mechanical
Property of Hf B2 Composite Joints
Kou Honda
Kyushu University, Japan
Noritaka Saito
Kyushu University, Japan
Kunihiko Nakashima
Kyushu University, Japan
Cesare Melandri
CNR-ISTEC Italy
Laura Esposito
CNR-ISTEC, Italy
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Recommended Citation
Kou Honda, Noritaka Saito, Kunihiko Nakashima, Cesare Melandri, and Laura Esposito, "Effect of Ni-Nb Interlayer Thickness on
Mechanical Property of Hf B2 Composite Joints" in "Ultra-High Temperature Ceramics: Materials for Extreme Environment
Applications III", G. Franks and C. Tallon, University of Melbourne Eds, ECI Symposium Series, (2015). http://dc.engconfintl.org/
uhtc-iii/10
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April 16, 2015 UHTC: Material For Extreme Environment Applications Ⅲ
Effect of Ni-Nb Interlayer Thickness
on Mechanical Property
of HfB2 Composite Joints
Kou Honda, Noritaka Saito, and Kunihiko Nakashima
Kyushu University, Japan
Cesare Melandri, and Laura Esposito
CNR-ISTEC, Italy
15年5月7日木曜日
Background - Ultra High Temperature Ceramics
UHTCs：Ultra High Temperature Ceramics
1348
Journal of the American Ceram
↳Several borides, carbides, and nitrides
of the group Ⅳ and Ⅴ metals
Ti, Zr, Hf, Ta
-B2, -C, -N
Excellent properties
・High melting points（> 3000℃）
・Good thermo-mechanical properties
・Chemical stability
Prospective applications
Problems
・Poor sinterability and workability
Fig. 1.
A comparison
ofetthe
temperatures
most refracWilliam
G. Fahrenholtz
al. melting
: J. Am. Ceram.
Soc., 90 of
[5] the
1347–1364
(2007)
tory members of several classes of materials. Several borides, carbides,
and nitrides have melting temperatures above 30001C and are considered
ultra high-temperature ceramics. For comparison, the melting temperature of Zr is B18501C and the melting temperature of Hf is B22271C.
B atoms
in a structural
complex
leads to increases in the B–B
It is difficult to produce the large and complex
shaped
parts
of
UHTCs.
bond strength and an increase in the stiffness of the crystal lat-
For the practical use, an effective method
15年5月7日木曜日
tice along with increases in melting temperature (Tm), hardness
(HV), strength (s), and chemical stability.
The M–B bond strength in diborides depends on the degree of
of
bonding
will
be the
required.
electron
localization
around
M atoms. The valence electron
configuration in isolated B atoms is 2s22p. In metal borides, the
outer electron configurations are sp2 and sp3, which promote
strong covalent bonding. In diborides, B atoms are electron acceptors, while the M atoms are electron donors. Each M atom
donates two electrons (one to each B), which converts M to a
doubly charged cation, while B atoms become singly charged
21
!
31,32,40–45
Background - Typical methods of ceramics bonding
Typical examples of ceramics bonding
Metal brazing
bonding
Oxide solder
bonding
Ceramics
Metal
Ceramics
Ceramics
Oxide
Ceramics
Low melting metal
↓
Heat resistance ✕
Solid state
bonding
Ceramics
Ceramics
B
Zr
Bad wettability
↓
Adhesion ✕
Transient Liquid Phase (TLP) bonding
15年5月7日木曜日
High temperature
and
high pressure
↓
Cost ✕
Background - TLP (Transient liquid phase) bonding
TLP bonding
Insert metals
Cladding
low low
melting
pointmetal
metals
Cladding
melting
Ceramics
Refractory
core metal
➀
➁
➂
Ceramics
➀ The cladding metals will melt and fill the gap between the ceramics and the core metal.
➁ The liquid cladding metals will diffuse through the core metal.
➂ The interlayer will have higher re-melting temperature than the bonding temperature.
A low cost and well-trusted bonding method at high temperature use
15年5月7日木曜日
Objective
HfB2 composite joints
The TLP bonding using Ni-Nb interlayer was successfully
applied to bond HfB2 composite in our previous work.(1)
The adequate thickness of the interlayers of the joints is
needed to explore.
Interlayer
Ni-Nb
Objective
The present work aimed at investigating the effect of Ni-Nb interlayer
thickness on the mechanical properties of HfB2 composite joints.
(1)Noritaka Saito:J.Mater.Sci, 47, 8454-8463(2012)
15年5月7日木曜日
Experimental procedure- Fabrication of HfB2 composites
Raw powders
HfB2 (2 μm, 99.5%) + 10 vol% MoSi2 (-2 μm, 99.9%)
Milling and Mixing
ZrO2 milling media for 24 h in ethanol
Microstructure of HfB2 composite
Molding
Microstructure of HfB2 composite
Uniaxial pressing
+300 MPa CIPing
Sintering
1950℃ for 1 h
Under 0.1 MPa Ar
Polishing
Relative density
97.6%
with diamond slurry
Bonding
15年5月7日木曜日
HfB2
MoSi2
2 μm
Experimental procedure- Fabrication of HfB2 composite joints
Interlayer
Sample A
Cladding metal: Ni
Core metal: Nb
Ni
Nb
Hot pressing
Atmosphere: 20 Pa Vacuum
Temperature: 1500°C
Holding time: 30 min
Applied pressure: 8.5 MPa
Quenching
Ni
HfB2
composite
Sample B
127Niμm
2 Ni
μm
Ni : 0.40 μm
HfB2
composite
Nb
• The interfacial region of joints were observed by using FE-SEM.
• The mechanical properties of joints were evaluated by 4-points bending test.
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2 Ni
μm
25.4 μm
Observation results of interfacial reaction
15年5月7日木曜日
Interfacial microimage of sample A (Nb : 127 μm, Ni : 2 μm)
Sample A
Reaction
layer
10 μm
130 μm
Nb
Nb
Nb-Si
Nb-Ni-Si
HfB2 composite
HfB2
Nb
Nb5Si3 (Nb,Hf)2NiSi NbNiSi
20:27 at%
・The interdiffusion of Ni and Nb was not completed.
・The reaction layer mainly contained Si from MoSi2 sintering aid.
・The HfB2 composites hardly reacted to the interlayers.
15年5月7日木曜日
(Nb,Hf)3B2
36:24 at%
5μm
Interfacial microimage of sample B (Nb : 25.4 μm, Ni : 0.40 μm)
Nb ss
Sample B
Reaction
layer
20 μm
50 μm
Nb-Hf-Ni
Nb solid solution
Nb-Hf-Si
Nb-Hf-B
HfB2 composite
HfB2
(Nb,Hf)3B2 (Nb,Hf)5Si2 Nb5Si2 (Nb,Hf,Mo) (Hf,Nb)2Ni
45:16 at%
62:9 at%
76:16:8 at% 51:17 at%
5μm
・The interdiffusion of Ni and Nb was not completed similar to Sample A.
・The reaction layer contained Si and Hf from HfB2 composite.
15年5月7日木曜日
Discussion on the interfacial reaction of sample A
Before bonding
During heating
After bonding
Nb
Nb
Nb
Ni
HfB2 composite
➀ Ni-Nb melt
Nb-Si
Nb-Ni-Si
➁
Si
➂
HfB2 composite
Nb-Hf-B
➀ Enough amount of Ni-Nb melt was formed, and filled the gap between Nb and
HfB2 composite.
➁ Nb and Si diffused into the other side respectively.
➂ The thick reaction layer was formed uniformly.
15年5月7日木曜日
Discussion on the interfacial reaction of sample B
Before bonding
During heating
Nb
➁
HfB2 composite
Nb ss
Nb-Hf-Si
Nb-Hf-B
➂
HfB2 composite
Ni
➀ Nb-Ni melt
➀ Smaller amount of Ni-Nb melt was formed.
➁ Nb directly touched and reacted with HfB2 composite.
➂ The reaction layer was formed complexly.
15年5月7日木曜日
After bonding
Hf-Nb-Ni
Summary of interfacial reaction
Sample B
Sample A
Nb
Nb
Ni-Nb melt
HfB2 composite
HfB2 composite
Nb-Ni melt
Difference in the interfacial reaction is due to the difference
in the amount of Ni-based melt.
15年5月7日木曜日
4-points bending test
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Fabrication process of bending beams for 4-points bending test
Electrical discharge machining
Bonding
2.5
mm
2.5mm
BBBBBB
BBBBBB
Cutting
B
2
mm
2mm
Electrical discharge machining
2 mm ×2.5 mm ×25 mm
HfB2
HB10M
Polishing
4-points bending test
Strength measurement
at R.T. and at H.T. (1000℃)
15年5月7日木曜日
mmm
with diamond slurry
HfB2
HB10M
φ10mm
φ10
mm
Experimental procedure of 4-points bending test
σ=
σ
P
l
L
w
t
3P(L-l)
2wt2
:
:
:
:
:
:
Bending stress (MPa)
Maximum Load (N)
Loading span (mm)
Support span (mm)
Width (mm)
Thickness (mm)
R.T. tests for Joints
Crosshead speed ：1mm/min
Number of Trials ：5 times
H.T. tests for Joints
Crosshead speed ：1mm/min
Number of Trials ：3 times
Pressure
Conditions
Pressure
：1000°C in air
R.T. tests for HfB2 Composite
Crosshead speed ：1mm/min
l: 10 mm
Number of Trials ：12 times
t: 2 mm
w: 2.5 mm
L: 20 mm
25 mm
15年5月7日木曜日
Result and discussion of 4-points bending test
600"
600
HfB2 Composite at R.T.
462 ± 45.7 MPa
Bending Strength (MPa)
500"
500
398 MPa
337 MPa
300"
300
200"
200
187 MPa
100"
100
0
15年5月7日木曜日
412 MPa
400"
400
H.T.：1000°C
0"
0"
0.5"
A
(R.T.)
1"
1.5"
2"
2.5"
B
A
(R.T.)
(H.T.)
Joint Sample
3"
3.5"
B
(H.T.)
4"
Result and discussion of 4-points bending test
SampleA and Sample B had similar strength, and had comparable strength with HfB2
composite strength at R.T.
600"
600
HfB2 Composite at R.T.
462 ± 45.7 MPa
500
Bending Strength (MPa)
500"
comparable strength
398 MPa
337 MPa
300"
300
200"
200
187 MPa
100"
100
0
15年5月7日木曜日
412 MPa
400"
400
H.T.：1000°C
0"
0"
0.5"
A
(R.T.)
1"
1.5"
2"
2.5"
B
A
(R.T.)
(H.T.)
Joint Sample
3"
3.5"
B
(H.T.)
4"
Result and discussion of 4-points bending test
SampleA and Sample B had similar strength, and had comparable strength with HfB2
composite strength at R.T.
・From SEM observation of the fracture surfaces, similar Nb-Si were found.
・Ductile metal Nb would decrease the influence of residual stress in the cooling period of the
bonding process.
Sample A
Sample B
5μm
Nb5Si3
Nb5Si2
5μm
15年5月7日木曜日
Result and discussion of 4-points bending test
In Sample A, the H.T. strength was slightly decreased compared with the R.T. strength.
In Sample B, the H.T. strength was significantly decreased.
600"
600
HfB2 Composite at R.T.
462 ± 45.7 MPa
500
Bending Strength (MPa)
500"
398 MPa
337 MPa
300"
300
200"
200
187 MPa
100"
100
0
15年5月7日木曜日
412 MPa
400"
400
H.T.：1000°C
0"
0"
0.5"
A
(R.T.)
1"
1.5"
2"
2.5"
B
A
(R.T.)
(H.T.)
Joint Sample
3"
3.5"
B
(H.T.)
4"
Result and discussion of 4-points bending test
In Sample A, the H.T. strength was slightly decreased compared with the R.T. strength.
In Sample B, the H.T. strength was significantly decreased.
・Some intermetallics phases of Ni-Nb were found.
・These Ni-Nb intermetallics have relatively low melting temperature.
・The presence and softening of these intrmetallics would be a possible reason why the
H.T. strength of Sample B was found to be small.
Nb7Ni6+Nb2Ni6
15年5月7日木曜日
Summary
The present work aimed at investigating the effect of Ni-Nb interlayer
thickness on the mechanical properties of HfB2 composite joints.
・HfB2 composite joints were well-bonded by TLP bonding using Ni-Nb interlayer.
・Different thickness of Ni-Nb interlayer caused different reaction in the interfacial region.
・The different reaction was due to the difference in the amount of Ni-based melt.
・Two kinds of the joints revealed the similar strength at room temperature because similar
Nb-Si was formed on the interfacial region regardless of the different reaction.
・Because Ni-Nb intermetallics have relatively low melting temperature, the intermetallics
would significantly decrease the high temperature strength of the joints bonded with small
amount of Ni.
15年5月7日木曜日
Thank you !
15年5月7日木曜日