High-temperature creep response of a commercial grade siliconized silicon carbide

摘要

Creep studies conducted in four-point flexure of acommercial siliconized silicon carbide (Si-SiC, designated asNorth NT230) have been carried out at temperatures of 1300,1370, and 1410℃ in air under selected stress levels. The Si-SiCmaterial investigated contrained ~90%α-SiC , 8% discontinuousfree Si, and 2% porosity. In general, the Si-SiC material exhibitedvery low creep rates (2 to 10×10-10s-1 ) at temperatures ≤1370℃ under applied stress levels of up to 300 Mpa. At 1410℃, themelting poit of Si, the Si-SiC material still showed relative lowcreep rates (~0.8 to 3×10-9s-1 ) at stresses below a threshold valueof ~190Mpa. At stresses >190Mpa the Si-SiC material exhibitedhigh creep rates plus a high stress exponent (n=17) as a result ofslow crack growth assisted process that initiated within Si-richregions. The Si-SiC material, tested at temperature≤1370℃ andbelow the threshold of 190Mpa at 1410℃, exhibited a stressexponent of one, suggestive of diffusional creep processes.