High-temperature compressive creep of liquid phase sintered silicon carbide

Creep of liquid phase sintered SIC has bern studied at temperatures between 1575 and 1700 degrees C in argon under nominal stresses from 90 to 500 MPa. Creep rates ranged from 3 x 10(-8) to 10(-6)/s, with an activation energy of 840 +/- 100 kJ/mol (corresponding to carbon and silicon self-diffusion), and a stress exponent of 1.6 +/- 0.2. The crept samples showed the presence of dislocation activity, generally forming glide bands and tangles. Degradation of the mechanical properties due to cavitation or reaction of the additives was not detected. SEM and TEM microstructural characterization and analysis of the creep parameters leads to the conclusion that the creep mechanisms operating are grain boundary sliding accommodated by lattice diffusion and climb-controlled dislocation glide operating in parallel. Other possible operating mechanisms are discussed and the data are compared with published data. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. Ali rights reserved.