Abstract
The effect of corrosion on fatigue fracturing of silicon nitride ceramics was investigated in 1N and 3N H2SO4 solutions. The crack propagation rate da/dt increased when the stress ratio R under cyclic loading was decreased. The higher concentrated solution enlarges the stress ratio dependence of da/dt. Therefore, it is considered that corrosion increases the effect of cyclic loading on da/dt. According to results of an energy dispersive X-ray spectroscopy (EDX) analysis, it was found that the sinterring additive components of Al and Y decreased at the crack tip. This suggests that the grain boundary phase at the region dissolved. In addition, a similar effect was also observed by scanning electron microscopy (SEM). Consequently, it is concluded that the dissolution of the grain boundary phase contributes to the increase of da/dt in H2SO4 solutions.
