Compressive fatigue characteristics of Wc-Co based alloys

As WC-Co based alloys have excellent wear and deformation resistance due to high hardness, high compressive strength and Young's modulus, they have been widely applied for wear and impact resistance tools or substrate of cutting tools. In this study, the effects of Co content, WC grain size, HIP and coating treatment on compressive fatigue life of WC-(0 similar to 1.2)%Cr(3)C(2)-(7-20)%Co alloys with different WC grain size were mainly investigated and also discussed with relation to the variation of coercive force of the alloys 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 microgram 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.