Comparison On The Immersion Corrosion and Electrochemical Performance of WC-Al2O3 Composites and WC-Co Hard Metal in NaCl Solution

WC-15wt.%Al2O3 composites was prepared via hot pressing sintering technology. The corrosion behaviors of WC-Al2O3 composites and traditional WC-Co hard alloy in NaCl solution were studied by immersion corrosion and electrochemical technique. The impedance value of WC-Al2O3 composite increased more rapidly than WC-Co hard metal during the 24 hours, which indicated that WC-Al2O3 composites has more compact passivation film than WC-Co hard metal. The results confirmed that the corrosion performance of WC-Al2O3 composites was higher than WC-Co cemented carbide in NaCl solution. The corrosion mechanism of WC-Al2O3 composites and WC-Co hard alloy 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 hard alloy 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 WC phase and Co binder.