Deformation-resistant Ta0.2Hf0.8C solid-solution ceramic with superior flexural strength at 2000°C

In this study, we explored the consolidation, solid-solution formation and high-temperature properties of tantalum hafnium carbide with the 1 TaC:4 HfC ratio, that is, Ta0.2Hf0.8C. Tantalum hafnium carbide bulks can be consolidated using spark-plasma sintering only at temperatures exceeding 2200 degrees C. The bulks prepared using a 40-min dwell at 2200 degrees C had the lattice parameter a = 4.571(9) A. Based on the three-point flexural tests, it was observed that the toughness and strength of Ta0.2Hf0.8C remained high at 2000 degrees C (3.4 +/- 0.4 MPa m(1/2), 500 +/- 20 MPa). At 2000 degrees C, majority of carbides show a plastic behavior, but the strain-stress curves of the SPSed Ta0.2Hf0.8C ceramic were linear. Using the shrinkage rate data during the SPS and the strain-stress data from the high-temperature flexure, we estimated the activation energies for the densification and flexure as 820 +/- 20 kJ/mol and 1180 +/- 120 kJ/mol, respectively.

Automated summary

In this study, the consolidation, solid-solution formation, and high-temperature properties of tantalum hafnium carbide with a 1 TaC:4 HfC ratio were investigated. It was found that Ta0.2Hf0.8C maintained high toughness and strength at 2000 degrees C. By analyzing shrinkage rate and strain-stress data, activation energies for densification and flexure were estimated.