Thermal shock resistance of SiC whisker reinforced Si3N4 ceramic composites

Thermal shock resistance of hot-pressed SiCw/Si3N4 (w = whisker) composites was investigated by thermal shock resistance parameters and water quenching test. The results showed that the thermal shock resistance to fracture initiation and crack-stable repropagation deteriorated with increasing SiCw content in spite of the improvement of fracture toughness, K-IC. This could be attributed to the great decrease of strength, sigma, and the considerable increase of Young's modulus, E, and thermal expansion coefficient, alpha, resulting from the addition of SIC whiskers. The curves of the residual strength, sigma(r), after water quenching versus thermal shock temperature difference, Delta T, e.g. sigma(r)-Delta T, showed good relationships with the calculated thermal stress fracture resistance parameter, R, and thermal stress crack stability parameter, R(st). The crack propagation of SiC whisker reinforced Si3N4 occurred primarily in a quasi-static manner: and it could be mainly attributable to SIC whiskers' pulling-out and bridging toughening effects.