Comparison on the immersion corrosion and electrochemical corrosion resistance of WC–Al2O3 composites and WC–Co cemented carbide in NaCl solution

Abstract

WC–15 wt% Al₂O₃ composites were prepared via hot pressing sintering technology. The corrosion behaviors of WC–Al₂O₃ composites and traditional WC–Co cemented carbide in NaCl solution were studied by immersion corrosion and electrochemical technique. The impedance value of the WC–Al₂O₃ composite increased more rapidly than WC–Co cemented carbide during the 24 hours, which indicated that WC–Al₂O₃ composites had a more compact passivation film than WC–Co cemented carbide. The results confirmed that the corrosion resistance of WC–Al₂O₃ composites was higher than that of WC–Co cemented carbide in NaCl solution. The corrosion mechanisms of WC–Al₂O₃ composites and WC–Co cemented carbide in NaCl solution were also revealed by SEM, EDS, XPS and Raman. The corrosion products of WC–Al₂O₃ composites mainly contain WO₃, while for WC–Co cemented carbide they are Co(OH)₂, Co₃O₄ and WO₃. The different corrosion mechanism of the two materials is attributed to the Al₂O₃ phase instead of the Co binder, which avoids the galvanic corrosion between the WC phase and the Co binder.