Comparative bending creep behaviour of silicon carbide sintered with oxynitride additives

The characteristic high temperature creep behaviour of liquid phase sintered SiC ceramics with Y2O3-AlN and Lu2O3-AlN as sintering additives has been evaluated as a function of composition, microstructure and post-sintering treatment. Creep testing in four-point bending geometry was performed at temperatures between 1200 °C and 1500 °C in air under stresses ranging from 50 to 300 MPa. Grain boundary sliding accommodated by grain boundary diffusion along with some creep cavitations were found to be possible creep mechanisms. A comparative study with reference to the additive system Y2O3-AlN demonstrates significantly improved creep resistance of the Lu2O3-containing ceramics.