Effect of oxidation on the strength of silicon nitride base reaction sintered ceramics

Conclusions Oxidation of silicon nitride base reaction sintered material at 1400°C with subsequent removal of the oxide layer makes it possible to increase the strength of the material at 20°C by 20%. On the other hand, short-term strength at 1400°C after such treatment is lower than the strength of nonoxidized specimens, yet it is still greater than the strength of oxidized specimens from whose surface the oxide layer was not removed.The increased strength of specimens after oxidation is mainly connected with the fact that defects in the subsurface layers of ceramics are healed by the oxide phase and that impurities are removed from the inner layers. Reduced strength is usually caused by the formation of an oxide layer with high concentration of defects on the surface of the specimens or by considerable internal stresses arising in the specimen.Translated from Poroshkovaya Metallurgiya, No. 5(281), pp. 40–44, May, 1986.