HOT ISOSTATIC PRESSING OF SIC-PLATELETS Y-TZP COMPOSITES

Composites consisting of Y-TZP matrix with SiC-platelet secondary phase were first densified by a two-step procedure consisting in pressureless sintering, followed by HIPing. Although platelets do not significantly affect matrix packing and microstructure, they modify the transformation of tetragonal into monoclinic zirconia during rupture, mainly according to a load transfer mechanism. In spite of a lower reinforcement by transformation toughening, the composites show higher toughness due to load transfer and crack deflection mechanisms, which are found to be active from room temperature up to 300-degrees-C. For higher temperatures, matrix degradation is observed due to cracking or chemical reaction of platelets with oxygen at the matrix-platelet interface.