Transverse-Rupture Strength of WC-Go Alloys Coated with Titanium Nitride by PVD Process

The transverse-rupture strength of HIP-treated WC-(5~20)%Go alloys coated with titanium nitride layer up to 5/μm by PVD process at 773K was mainly studied. The effect of annealing at 923~1273K on the strength of coated alloys was also studied. The strength of coated alloys decreased generally with increasing thickness of coated layer; and the strength was lower as Co contents of alloys increased, excepting the case of 5% Co alloy. Decrease in the strength became markedly with decreasing Co contents, when coated alloys were annealed. At a fixed Co content and thickness of layer, the strength of coated alloys annealed at 1073~1273K was nearly the same, irrespective of annealing temperatures. The strength obtained after annealing was almost equal to that of coated alloy by CVD process (in this case, total thickness of coated layer and η-containing layer was regarded as the thickness of layer). The above phenomena concerning the strength of coated alloys could be clarified, based on the fact that fracture characteristics of coated alloy were substantially different between as PVD and annealed state, being in close relation to the fracture strength of coated layer.