Effect of Oxidation on Creep of Silicon-Nitride-Based Ceramics

Abstract

AbstractThe creep behaviour of reaction bonded silicon nitride materials strongly depends on the amount and type of porosity allowing oxygen to penetrate into the interiour. For dense silicon nitride materials, the type and amount of additives are the most important factors to control the oxidation and creep behaviour. A parallelism in the temperature dependance of creep and oxidation is observed, and a characteristic temperature is found for each individual material, which is decisive for the performance limits. Transient creep is observed over long period of time. At high temperatures, with beginning of the softening of the intergranular phase, accelerated creep with rather short time to rupture occurs. A preoxidation treatment is in most cases beneficial for the creep properties. The postinvestigation of the crept specimens revealed, that the oxidation behaviour is influenced by the stresses during the test. The extent of oxidative attack and the phases present are different in stressed and non stressed regions of the specimens.KeywordsCreep RateOxide ScaleSilicon NitrideCreep BehaviourSecondary CreepThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.