Abstract
Cemented carbides with nickel binder have been widely used in place of cemented carbide with cobalt binder for improved corrosion resistance. For the cemented carbides of WC-Ni and WC-Ni-Cr alloys, the corrosion properties and the effects of carbon and Cr3C2 contents on their corrosion resistance were investigated by both immersion test and electrochemical measurement. In immersion test, dissolved elements and the amounts of them in 3%NaCl and 3%NaC1+0.1NH2SO4 solutions were analyzed by ICP spectroscopy. In electrochemical measurement, polarization curves in these solutions were measured. The anodic reaction was dissolution of the binder metals in both solutions, and the cathodic reactions were reduction of dissolved oxygen in 3%NaC1 solution, and reductions of both proton and dissolved oxygen in 3%NaC1+0.1NH2SO4 solution respectively. Anodic current densities in the polarization curves showed that corrosion resistance of WC-Ni-Cr was superior to that of WC-Ni. WC-Ni alloys with low carbon content showed the superior corrosion resistance to that of high carbon alloy, which was revealed by both conspicuous appearance of passivated region and low anodic current density in polarization curve.
