Thermodynamic consideration and phase evolution during oxidation of tungsten–copper electrical contactor scraps

Abstract

Present studies account the feasibility studies on isothermal oxidation of W–Cu hard metal electrical contractor scraps for recycling by roasting-leaching method. This was investigated as one of main processes to produce friable oxidized product amenable to subsequent leaching process. Oxidation is facilitated using scrap turnings instead of solid W–Cu contactor rods. The alloy oxidizes to Cu_xO, WO_x and CuWO₄ upon heating in the temperature range 400–1000°C under oxygen flow. Apart from oxidized W and Cu phases, significant amount of Cu nuggets formed initially at 450°C that rose gravimetrically up to 750°C, and then disappeared at higher temperature. The maximum weight gain was about 22% compared to initial weight when oxidation was carried out at 750°C. Oxidation beyond the temperature of 750°C corresponded to significant loss of tungsten by evaporation of WO₂ · (OH)₂ gaseous product. Thermal oxidation of W–Cu metal electrical contractor tip scraps produced porous and friable oxidized product of W and Cu.