ＷＣ‐Ｃｏ系超硬合金の圧縮疲労特性

Abstract

As WC-Co based alloys have high hardness, compressive strength and Young's modulus and excellent deformation resistance, they have been widely applied for wear and impact resistance tools. Therefore, it becomes very important to acquire knowledge on compressive fatigue characteristics of these alloys. In this study, the effects of Co content, WC grain size, HIP and coating treatment on compressive fatigue life of medium or coarse-grain WC-7-20mass% Co alloys and micrograin WC-6-l5mass%Co-0.4-1.2mass%Cr3C2 alloys were mainly investigated and discussed with the variation of coercive force during fatigue process.The results obtained were as follows: (1) The fatigue life increased with decreasing Co content in the medium and coarse-grain alloys, but it was almost same with no relation to Co content in the micrograin alloys. The fatigue life showed an upward tendency with decreasing WC grain size. (2) The effect of HIP treatment on fatigue life was not observed at all. The fatigue life of PVD-coated alloy did not change and that of CVD-coated alloy remarkably decreased, comparing with that of non-coated alloy. (3) The coercive force of medium-grain WC-12mass%Co alloy increased with increasing applied maximum stress and repeated cycle, and it became much larger in the repeated compressive fatigue test than static compressive test. This increase of the coercive force was considered to be equivalent to the degree of toughness deterioration due to fatigue hardening in Co phase during fatigue process.