窒化けい素およびサイアロンの転がり疲労

抄録

Rolling contact fatigue tests were performed for two types silicon nitrides and a sialon using disk-type specimens. Both materials showed a fatigue behaviour similar to that typically found in metallic materials. From the fractographic and metallographic observations, it has been found that the crack initiation in the silicon nitrides subjected to rolling contact fatigue is to be induced by cyclic subsurface shear stress, as is known in steel bearings. On the mid-sections of the specimens, many subsurface cracks which lay parallel to the contact surface can be found at a depth where fluctuation of the Herzian shear stress was the maximum. The specimens subjected to the higher frequency rolling gave the shorter failure lives. Although the cyclic fatigue of ceramics under the pulsating uniaxial stress seems to be governed by environmentally assisted cracking, these facts suggest that the occurrence of cyclic dependent type of fatigue in ceramics is alternatively possible under the cyclic compressive stress state.