Oxidation weight gain and strength degradation of Si3 N4 with various additives

Abstract

Oxidation behaviour and strength degradation, due to long-term high temperature exposure in air, of Si3N4 with MgO, ZrO2 or Y2O3, as densification aids have been studied. It was found that the weight change and strength degradation in the specimens depend largely on the kind of densification aid. Strength degradation, which generally occurred and was greatest at higher additive levels, was related to the generation of pits in the specimen surface. Possible mechanisms for pit formation are discussed.