Effects of crystal phases on creep behaviour of SiAlON ceramics

Mechanical properties of SiAlON that is one of the important high technology ceramic at both room temperature and elevated temperature are associated with the type and the amount of the aids in starting composition. In this study, 45×3×4 mm bar shape samples were prepared with different compositions by using Er2O3, Yb2O3, Lu2O3 and various heat treatment were applied on the samples. After surface preparation, creep tests were applied in atmospheric environment at 1400 ºC and 100 MPa. Each composition were investigated by using XRD and SEM techniques before and after creep tests. Also creep tests were applied on the heat treatment samples to determine the effects of heat treatment temperature and period. Creep resistance was increased by extending of sintering and heat treatment periods. After determining the best sintering and heat treatment condition creep mechanism were determined by creep tests that were applied at different temperatures and loads. Creep test results showed that Lu2O3 composition has the best creep resistance while Yb2O3 composition has the worst creep resistance.