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 (x) O, WO (x) and CuWO4 upon heating in the temperature range 400-1000A degrees C under oxygen flow. Apart from oxidized W and Cu phases, significant amount of Cu nuggets formed initially at 450A degrees C that rose gravimetrically up to 750A degrees C, and then disappeared at higher temperature. The maximum weight gain was about 22% compared to initial weight when oxidation was carried out at 750A degrees C. Oxidation beyond the temperature of 750A degrees C corresponded to significant loss of tungsten by evaporation of WO2 center dot (OH)(2) gaseous product. Thermal oxidation of W-Cu metal electrical contractor tip scraps produced porous and friable oxidized product of W and Cu.