Initiation of Oxidized Intergranular Cracking in Low-Cycle Fatigue at High Temperature.

Intergranular cracking due to oxidation under low-cycle fatigue loading at 700°C has been studied with a comparison of results obtained from two different types of specimens, with and without oxidation. Morphology of the surface oxidation of the specimen under low-cycle fatigueloading is quite different from that of the specimen without fatigue loading. Selective oxidation along the grain boundary was observed on the surface of fatigue-loaded specimens, while on the other hand, the surface of specimens without fatigue loading was oxidized uniformly all over the area. Intergranular cracking occurs under the combined effects of preferential oxidation along the grain boundary and grain boundary sliding in high-temperature low-cycle fatigue in air.