Effect of Ni-Nb Interlayer Thickness on Mechanical Property of Hf B2 Composite Joints

Transcription

1 Engineering Conferences International ECI Digital Archives Ultra-High Temperature Ceramics: Materials for Extreme Environment Applications III Proceedings Spring 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 Follow this and additional works at: Part of the Materials Science and Engineering Commons Recommended Citation Kou Honda, Noritaka Saito, Kunihiko Nakashima, Cesare Melandri, and Laura Esposito, "Effect of Ni-Nb Interlayer Thickness on Mechanical Property of HfB2 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). uhtc-iii/10 This Conference Proceeding is brought to you for free and open access by the Proceedings at ECI Digital Archives. It has been accepted for inclusion in Ultra-High Temperature Ceramics: Materials for Extreme Environment Applications III by an authorized administrator of ECI Digital Archives. For more information, please contact

2 April 16, 2015 UHTC: Material For Extreme Environment Applications Ⅲ Effect of Ni-Nb Interlayer Thickness on Mechanical Property of HfB 2 Composite Joints Kou Honda, Noritaka Saito, and Kunihiko Nakashima Kyushu University, Japan Cesare Melandri, and Laura Esposito CNR-ISTEC, Italy

3 Background - Ultra High Temperature Ceramics UHTCs Ultra High Temperature Ceramics Several borides, carbides, and nitrides of the group Ⅳ and Ⅴ metals Excellent properties Ti, Zr, Hf, Ta -B 2, -C, -N High melting points > 3000 Good thermo-mechanical properties Chemical stability Prospective applications Problems William G. Fahrenholtz et al. : J. Am. Ceram. Soc., 90 [5] (2007) Poor sinterability and workability It is difficult to produce the large and complex shaped parts of UHTCs. For the practical use, an effective method of bonding will be required.

4 Background - Typical methods of ceramics bonding Typical examples of ceramics bonding Metal brazing bonding Ceramics Metal Ceramics Low melting metal Heat resistance Oxide solder bonding Ceramics Oxide Ceramics Bad wettability Adhesion Solid state bonding Ceramics Ceramics High temperature and high pressure Cost Transient Liquid Phase (TLP) bonding

5 Background - TLP (Transient liquid phase) bonding TLP bonding Cladding Cladding low low melting melting point metal metals Insert metals Ceramics Ceramics Refractory core metal ➀ ➁ ➂ 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

6 Objective HfB 2 composite joints The TLP bonding using Ni-Nb interlayer was successfully applied to bond HfB 2 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 HfB 2 composite joints. (1)Noritaka Saito:J.Mater.Sci, 47, (2012)

7 Experimental procedure- Fabrication of HfB 2 composites Raw powders HfB 2 (2 μm, 99.5%) + 10 vol% MoSi 2 (-2 μm, 99.9%) Milling and Mixing ZrO 2 milling media for 24 h in ethanol Molding Uniaxial pressing +300 MPa CIPing Microstructure of HfB2 composite of HfB 2 composite Sintering Polishing 1950 for 1 h Under 0.1 MPa Ar Relative density 97.6% with diamond slurry Bonding HfB 2 MoSi 2 2 μm

8 Experimental procedure- Fabrication of HfB 2 composite joints Interlayer Cladding metal: Ni Core metal: Nb Sample A Ni 2 Ni μm Hot pressing Quenching Atmosphere: 20 Pa Vacuum Temperature: 1500 C Holding time: 30 min Applied pressure: 8.5 MPa HfB 2 composite HfB 2 composite Sample B Nb Ni 127 Ni μm 2 Ni μm Ni : 0.40 μm Nb 25.4 μm The interfacial region of joints were observed by using FE-SEM. The mechanical properties of joints were evaluated by 4-points bending test.

9 Observation results of interfacial reaction

10 Interfacial microimage of sample A (Nb : 127 μm, Ni : 2 μm) Sample A Nb 130 μm Nb Nb-Si Nb-Ni-Si HfB 2 composite Reaction layer 10 μm HfB2 Nb Nb5Si3 (Nb,Hf)2NiSi 20:27 at% NbNiSi (Nb,Hf)3B2 36:24 at% 5μm The interdiffusion of Ni and Nb was not completed. The reaction layer mainly contained Si from MoSi 2 sintering aid. The HfB 2 composites hardly reacted to the interlayers.

11 Interfacial microimage of sample B (Nb : 25.4 μm, Ni : 0.40 μm) Nb-Hf-Ni Sample B Nb ss 50 μm Nb solid solution Nb-Hf-Si Nb-Hf-B HfB 2 composite Reaction layer 20 μm 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 HfB 2 composite.

12 Discussion on the interfacial reaction of sample A Before bonding During heating After bonding Nb Ni HfB 2 composite ➀ Ni-Nb melt Nb ➁ Si Nb Nb-Si Nb-Ni-Si HfB 2 composite ➂ Nb-Hf-B ➀ Enough amount of Ni-Nb melt was formed, and filled the gap between Nb and HfB 2 composite. ➁ Nb and Si diffused into the other side respectively. ➂ The thick reaction layer was formed uniformly.

13 Discussion on the interfacial reaction of sample B Before bonding During heating After bonding Nb ➁ Nb ss Nb-Hf-Si Nb-Hf-B ➂ HfB 2 composite HfB 2 composite Ni ➀ Nb-Ni melt Hf-Nb-Ni ➀ Smaller amount of Ni-Nb melt was formed. ➁ Nb directly touched and reacted with HfB 2 composite. ➂ The reaction layer was formed complexly.

14 Summary of interfacial reaction Sample A Sample B Nb Nb Ni-Nb melt HfB 2 composite HfB 2 composite Nb-Ni melt Difference in the interfacial reaction is due to the difference in the amount of Ni-based melt.

15 4-points bending test

16 Fabrication process of bending beams for 4-points bending test Bonding Electrical discharge machining Cutting Polishing Electrical discharge machining 2 mm 2.5 mm 25 mm with diamond slurry mmm HfB 2 HfB 2 10mm φ10 mm 2.5mm 2mm B BBBBBB BBBBBB 4-points bending test Strength measurement at R.T. and at H.T. (1000 )

17 Experimental procedure of 4-points bending test σ= 3P(L-l) 2wt 2 σ P l L w t : R.T. tests for Joints Bending stress (MPa) : Maximum Load (N) Crosshead speed 1mm/min : Loading span (mm) Number of Trials 5 times : Support span (mm) : Width (mm) H.T. tests for Joints : Thickness (mm) Crosshead speed 1mm/min Number of Trials 3 times Pressure Pressure Conditions 1000 C in air R.T. tests for HfB 2 Composite l: 10 mm Crosshead speed 1mm/min Number of Trials 12 times w: 2.5 mm t: 2 mm L: 20 mm 25 mm

18 Bending Strength (MPa) Result and discussion of 4-points bending test " " HfB 2 Composite at R.T. 462 ± 45.7 MPa " 412 MPa 398 MPa " 337 MPa " 187 MPa " 0 0" A (R.T.) A (H.T.) 0" 0.5" 1" 1.5" 2" 2.5" 3" 3.5" 4" Joint Sample B (R.T.) H.T C B (H.T.)

19 Result and discussion of 4-points bending test SampleA and Sample B had similar strength, and had comparable strength with HfB 2 composite strength at R.T " Bending Strength (MPa) " " " " " HfB 2 Composite at R.T. 462 ± 45.7 MPa 412 MPa comparable strength 337 MPa 398 MPa 187 MPa 0 0" A (R.T.) A (H.T.) 0" 0.5" 1" 1.5" 2" 2.5" 3" 3.5" 4" Joint Sample B (R.T.) H.T C B (H.T.)

20 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

21 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 " Bending Strength (MPa) " " " " " HfB 2 Composite at R.T. 462 ± 45.7 MPa 412 MPa 337 MPa 398 MPa 187 MPa 0 0" A (R.T.) A (H.T.) 0" 0.5" 1" 1.5" 2" 2.5" 3" 3.5" 4" Joint Sample B (R.T.) H.T C B (H.T.)

22 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. Nb 7 Ni 6 +Nb 2 Ni 6

23 Summary The present work aimed at investigating the effect of Ni-Nb interlayer thickness on the mechanical properties of HfB 2 composite joints. HfB 2 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.

24 Thank you!