Steam Oxidation Resistance of Silicon Carbide Castables at Elevated Temperatures

Silicon carbide castables of different SiC contents(86%and 71%,by mass)were prepared using white fused corundum,silicon carbide particles and fines,activated alumina powder,silica fume and pure calcium aluminate cement as main starting materials,heat treating at 1000℃ for 3 h,and oxidizing in steam atmosphere at 1000℃ for different durations(100,200,300,400 and 500 h).The mass and volume before and after oxidation,the bulk density,the apparent porosity and the cold compressive strength were tested.The phase composition and the microstructure before and after oxidation were analyzed by XRD and SEM.The results indicate that:(1)within 300 h of oxidation duration,silicon carbide shows an increasing oxidation rate;however,the oxidation rate is low during 300-500 h of oxidation duration;2)the oxidation rate of the specimen with 71%SiC is slightly higher than the one with 86%SiC;3)with the increasing oxidation degree of silicon carbide,the apparent porosity of the specimens tends to increase,followed by the declining bulk density and cold compressive strength.