Evaluation of Corrosion Resistance of WC-Co Based Alloys in H2SO4 Aqueous Solution

Though WC-Co cemented carbides are widely used for a variety of machining, cutting, drilling and other applications because of their high strength, high hardness and excellent wear resistance, there exist corrosion issues during practical use. However, little work is currently available in the published literature on this subject. In this study, the corrosion behaviors of three cemented carbide specimens, i.e., WC-Co (Sample A), WC-Cr3C2-Co (Sample B) and WC-βt-Co (Sample C) in which βt indicates (Ti, W, Ta, Nb) C, are investigated by the electrochemical methods such as the polarization test and the electrochemical impedance spectroscopy, hereafter shortened as EIS, as well as the immersion test under constant potential in comparison with that of SUS304 stainless steel. The similar active, passive and over passive state regions to SUS304 stainless steel during the polarization test, and the preferential dissolution of Co were observed for all of the three specimens mentioned above. Both Cr3C2 and βt improved the corrosion resistance of WC-Co alloy, in which the effect of the former was better than that of the latter. EIS test showed that all of the three samples showed the similar capacitance semicircle in the first quadrant. The induction semicircle followed the capacitance semicircle mentioned above for the sample A and sample C while the other capacitance semicircle followed for the sample B.