Oxidation of tungsten and tungsten carbide in dry and humid atmospheres

Abstract Oxidation experiments were performed on pure tungsten and hot-pressed tungsten carbide. The chemical state and thickness of the oxide products were determined by ESCA. The oxidation of W and WC in dry atmosphere was performed in oxygen at temperatures ranging from 20 to 500 °C. The oxide formed is WO 3 . The thickness of the oxide layer increases slowly up to 200 °C, after which the oxide growth is rapid. The oxidation behaviour of W and WC in humid atmospheres was studied at room temperature in air at relative humidities of 60 and 95%. It was found that the thickness of the oxide layer increases with increased humidity. No formation of hydroxide was observed. Exposing W to water for one week results in a thick layer of WO 2 , WO 3 and hydroxide. In the case of WC no oxide at all was visible after exposure to water. Furthermore, WC is resistant to further oxidation after exposure.