Microstructure and Fracture Toughness of Sintered Bodies from Fine SiC Powder and SiC-TiC Composite Powder

Abstract

Fine SiC powder and SiC-TiC composite powder were prepared by vapor phase reactions using Si(CH₃)₄ and TiCl₄. The particle size was about 200nm. They were hot-pressed at 2000°C in Ar with a sintering aid of Al₂O₃ or Y₂O₃-Al₂O₃ system. The sintered bodies were densified to 98-99% of theoretical. Rod-like grains were observed in monolithic SiC with both Al₂O₃ and Y₂O₃-Al₂O₃ system, and the higher fracture toughness was observed in Y₂O₃-Al₂O₃ system. The fracture toughness was increased by TiC inclusions although the growth of rod-like SiC grains tended to be retarded. The growth of SiC grains was exaggerated in SiC-TiC composite powder with a large amount of Y₂O₃-Al₂O₃ sintering aid, leading to more improved fracture toughness. The present results suggest that the improvement of fracture toughness can be enhanced by combination of rod-like SiC grain growth and TiC inclusion with Y₂O₃-Al₂O₃ sintering aid.