抄録
It is well known that the mechanical properties of cemented carbide largely depend on the WC grain size and carbon content. But the influence of WC grain size on the corrosion resistance has not been much studied. In this report, the effect of WC grain size on the corrosion properties of WC-15mass%Co cemented carbides was investigated in 3%NaCl neutral and 3%NaCl+0.1N H2SO4 acidic solutions by the immersion test and the polarization test. In the immersion test, the main dissolved element was Co, and the amount of dissolved Co in 3%NaCl+0.1N H2SO4 was several times lager than in 3%NaCl solution. The amount of dissolved metals in neutral and acidic solution decreased with the decreasing of WC grain size and the carbon content.
In the polarization test, the anodic reaction was the dissolution of the binder metals in both solutions, and the corrosion rate of the WC-Co alloy with smaller WC grain size was lower than that of the alloy with coarse WC grain size. WC-Co alloy with the smaller WC grain size showed a higher corrosion resistance because of the low current densities of active dissolution and passivated region in polarization curve.
