Joining of ultra-high temperature ceramics

Transcription

1 Engineering Conferences International ECI Digital Archives Ultra-High Temperature Ceramics: Materials For Extreme Environmental Applications II Proceedings Spring Joining of ultra-high temperature ceramics Laura Silvestroni CNR-ISTEC, Italy Diletta Sciti CNR-ISTEC, Italy Laura Esposito CNR-ISTEC, Italy Andreas Glaeser University of California - Berkeley Follow this and additional works at: Part of the Materials Science and Engineering Commons Recommended Citation Laura Silvestroni, Diletta Sciti, Laura Esposito, and Andreas Glaeser, "Joining of ultra-high temperature ceramics" in "Ultra-High Temperature Ceramics: Materials For Extreme Environmental Applications II", W. Fahrenholtz, Missouri Univ. of Science & Technology; W. Lee, Imperial College London; E.J. Wuchina, Naval Service Warfare Center; Y. Zhou, Aerospace Research Institute Eds, ECI Symposium Series, (2013). 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 Environmental Applications II by an authorized administrator of ECI Digital Archives. For more information, please contact franco@bepress.com.

2 Joining of ultra-high temperature carbides Laura Silvestroni 1, Diletta Sciti 1, Laura Esposito 1, Andreas M. Glaeser 2 1. Institute of Science and Technology for Ceramics, Via Granarolo 64, I Faenza, ITALY. 2.Dept. of Materials Science and Engineering, University of California, Berkeley.

3 Outline Introduction Aim of the work Starting materials Joint assembly Microstructure after joining Bonding mechanism Nanoindentation Conclusions & perspectives

4 Introduction Materials for high temperature applications: Borides and Carbides of Group IV, V transition metals High melting point High strength High hardness and stiffness Relatively good oxidation Low fracture toughness High density Processing often imposes simple shapes Difficult machining How to succesfully integrate UHTCs into hypersonic structures/turbine engines without losing the high temperature properties?

5 Ceramic bonding Solid state bonding Brazing and Active metal brazing Liquid phase bonding high precision only simple shapes, flat components, high P, high T pressureless, complicated shapes, moderate bonding T high vacuum and clean bonding atmosphere, limited excercise T pressureless, complicated shapes, possible degradation of the constituents, limited excercise T Transient liquid phase pressureless, complicated shapes, high precision, exercise T> bonding T bonding brittle reaction products, cte mismatch Aim of the work Explore the TLP bonding method for joining UHTCs Basic study of the reactions between -Ni and TMC Potential for strong refractory bonds

6 -Ni transient liquid phase A/B/A interlayer Liquid forma on a T<T B Liquid absorp on/ reactive penetration Ni- E 1 :1175 C E 2 :1290 C Ni-based alloys show adequate wettingbehavior towards UHTCs T ( C) C (Ni) 1282 C Ni 3 L 1175 C Ni C 2469 C () Void filling: θ1 + θ2 < Ni At %

7 Starting materials HP: 1900 C, 60 min, 30 MPa ZrC Density 98 % HfC Density 98 % TaC Density 93 % Uniform microstructures Rounded or faceted relatively equiaxed grains Mean grain dimensions ~10 µm. Occasional oxide phases ZrCandHfC: <2vol%offine,closedporosity(poresize0.3-1µm) TaC residual porosity 5 vol%. ~8%ofgraphiteinZrC( 1.5wt%offreeCinthestartingpowder)

8 Joint assembly Ni//Ni 2/125/2 µm platelet 1 2 Ceramic with polished surface 3 Al 2 O 3 milling media (<1.3 kpa) & Al 2 O 3 crucible 1400 C, 30, 10-4 Pa 4 C/min cooling,

9 Monolithic ZrC ZrC (Zr )C ZrC (Zr,)C -Zr-Ni Ni-Zr- 100 µm 10 µm 0.70 Zr 0.25 Ni 0.05 Ni 0.50 Zr µm

10 Monolithic HfC HfC 60 (Hf,)C µm HfC (Hf0.70.3)C HfC 10 µm (Hf0.70.3)C 0.55Ni0.3Hf0.15 Ni0.5Hf µm 5 µm HfC (Hf,)C -Ni-Hf Ni-Hf-

11 Monolithic TaC TaC (Ta,)C 10,Ni Ni0.35Ta0.05 TaC (Ta,)C Ta2C, Ta4C3 -Ta-Ni -Ni-Ta 5 µm 30 µm 2 µm 0.75Ta0.15Ni0.1 Ta2C, Ta4C3 (Ta )C 5 µm cracks

12 Bonding mechanism System ZrC HfC TaC New carbides (Zr,)C (Hf,)C (Ta,)C Ta 2 C, Ta 4 C 3 Metal alloys ZrNi NiZr NiHf NiHf TaNi NiTa TMC (TM,)C -rich alloy Ni-rich alloy Ta 2 C, Ta 4 C 3 GENERAL BEHAVIOR: -Ni eutec c 1176 C, 60 at%ni Infiltration in the ceramic by capillary forces TMC dissolution in the liquid and precipitation of (TM,)C Residuals of Ni 3 and Ni 6 7 containing traces of the TM ZrC: homogeneous (Zr,)C due to C impuri es Zr is highly soluble in Ni- alloy and excess of C helps the carbo-reduction HfC:jagged HfC grains in (Hf,)C HfC is the least soluble in -Ni alloy TaC:formation of Ta-rich carbides TaC easily loses C giving rise to the Ta-rich carbides

13 You ung's modulus (GPa) Nanoindentation on ZrC Bulk (Zr,)C ZrC ZrC gnagno Position (µm) x (µm) Hardness (GPa) 5 mn Bulk (Zr,)C 35 ZrC ZrC gnagno Position (µm) x (µm) Young s modulus slightly decreases in the (Zr,)C region Almost no variation for hardness (H C =18GPa)

14 Young's modulus (GPa) 700 HfC HfC gnagno Nanoindentation on HfC Bulk (Hf,)C Hardness (GPa) Bulk (Hf,)C HfC 5 mn HfC gnagno Position (µm) Position (um) Young s modulus and hardness are basically not affected by the presence of (Hf,)C

15 Nanoindentation on TaC Bulk Ta 2 C 600 TaC TaC gnagno C 40 Bulk Ta 2 C TaC C 5 mn Mo You odulo ung s di Modulus Young (GPa) bulk valori di bulk Hardness (GPa) valori bulk di bulk Posizione x impronta (µm) (µm) Posizione x impronta (µm) (µm) Young s modulus decreases in the Ta-rich carbide region Hardness increases moving toward the joint owing to pores closure, but decreases in the Ta-rich carbide region (H Ta2C =18GPa)

16 in the joints 5 mn pure pure is stiffer in TaC > ZrC = HfC; straight trend is harder in TaC > ZrC > HfC; U-shaped trend owing to C enrichment is hardest in TaC owing to C release from Ta-rich carbides formation

17 Conclusions & future perspectives Successful joining of monolithic TM carbides through transient liquid phase bonding at 1400 C with P<1.3 kpa. Good compatibilitybetweentmcand-nialloy,goodctematch(~ K -1 ) -NiNi melt dissolves the carbides and forms (M,)C. 2 residual metal alloys, -richandni-rich,arefoundclosetothejointwith tracesofthetm ZrC displays a homogeneous reaction zone, thanks to C in the microstructure HfCistheleastsolubleinthe-Nialloy TaClosesCevolvingintoTa-richcarbides(Ta 2 C,Ta 4 C 3 ) smallcracks Nanoindentation showed no or little E&H difference from bulk and reaction zone inhfc,forzrcandtace&hvariationswereobserved. IN PROGRESS Preparation of specimen for 3-pt strength measurements. MoSi 2 is detrimental as it originates,ni-silicides forming cracks upon cooling. SiC present as secondary phase seems stable promising for most UHTCs!

18 ZrC+15 MoSi2* *Most of MoSi2 converted to SiC ZrC ZrC+SiC (Zr,)C Ta2C (,Ni,Zr)xSiy (,Ni)C SiC ZrC + SiC (0.75Ni0.15Zr0.10)0.8Si µm 20 µm (Zrxy)C ZrC (Zr,)C (ZrxyNiz)C (,Ni,Zr)xSiy (,Ni,Zr) xsi 10 µm 5 µm

19 Acknowledgements Prof. B. Fahrenholtz, Prof. G. Hilmas (MS&T) Dr. S. Guicciardi, C. Melandri, D. Dalle Fabbriche (ISTEC-CNR) Thank you for your attention!

20 TaC+15v MoSi2 HfC+15v MoSi2 HfC/TaC + 15 MoSi2 HfC + MoSi µm 20 µm (Hf,,Ni,)C (,Ni,Hf,)xSiy (,Hf)C 10 µm (Mo,Ni)xSiy up to 40 μm in the matrix cracks (Ta,,Ni,)C (,Ni)xSiy (Ni, )xsiy 100 µm 10 µm µm 22 µm

21 Starting matrices ZrC HfC ρ:98% ρ:98% ρ:93% ~8%C graphite TaC +15 MoSi 2 10% SiC ~13%MoSi 2 <5% MoSi 2 2%SiC ~13%MoSi 2 2%SiO 2 0.5%SiC 5 20 µm µm 5 µm 5 µm