REACTION-INFILTRATED, NET-SHAPE SIC COMPOSITES

The processing and net-shape capability of SiC composites formed by reactive infiltration of glassy carbon preforms using liquid silicon alloys have been studied. Composites consisting of 65-85 vol.% SiC with a secondary phase of Si, Si-AI, or Si-Cu compounds have been prepared. Tests of dimensional changes and the retention of surface finish during reactive infiltration have been conducted. Changes in linear dimensions between a machined preform and the reacted composite can be smaller than 0.1%. Surface finishes R(a) < 1.8 mu m are achievable in as-reacted composites. The simultaneous joining and reaction bonding of parts to form a more complex shape has been demonstrated. The flexural strength, modulus of elasticity, hardness, and indentation fracture toughness of these materials have been characterized.