Grain size effect on wear resistance of WC-Co cemented carbides under different tribological conditions

Abstract

The grain-size dependence of wear resistance of WC-Co cemented carbides (with mean WC grain sizes of 2.2 μm, 1.6 μm, 0.8 μm and 0.4 μm, respectively) was investigated under different tribological conditions. The results showed that the grain size had opposite effects on wear resistance of the cemented carbides in dry sliding wear and microabrasion tests. In the former condition, with decrease of WC grain size hence the increase of hardness, plastic deformation, fracture, fragmentation and oxidation were all mitigated, leading to a drastic decrease in the wear rate. In the latter condition, pull-out of WC grains after Co removal dominated the wear, so that the hardness of cemented carbide was not a core factor. As a result, the wear resistance of the cemented carbide generally showed a decreasing trend with decrease of the grain size, except for a slight increase in the ultrafine-grained cemented carbide. Single-pass scratching of the cemented carbides under various loads indicated the same failure mechanism as that in the sliding wear tests. Furthermore, the reasons for severe surface oxidation of the coarse-grained cemented carbides were disclosed.