Oxidation and corrosion resistance of WC coated tungsten fabricated by SPS carburization

Tungsten carbide (WC) coated tungsten samples were fabricated through spark plasma sintering method by covering a layer of graphite powders on the tungsten substrates. The oxidation behavior in a flowing argon atmosphere containing 0-5 vol.% hydrogen and corrosion behavior in static heavy water have been investigated. It was found that the oxidation rate of WC coated sample is one seventh that of uncoated one at the temperature of 500 °C. However, at 650 °C, both of them underwent severe oxidation and a 40-50 microns thick layer of WO3 and WO2.9 compounds formed on the surface of both samples. Addition of 5 or 1 vol.% hydrogen can completely inhibit the occurrence of oxidation respectively for uncoated or coated samples, within the temperature range of 500-800 °C. Furthermore, corrosion behavior in static heavy water suggested that the uncoated tungsten underwent somewhat corrosion after 20 days' immersion at 20 °C. In contrast, the corrosion in 60 °C heavy water for 15 days was much severe. However, less corrosion was occurred to the coated samples in both cases. For both kinds of samples, the corrosion products mainly consisted of tungsten oxides and hydroxides.