Activated sintering of tungsten alloys through conventional and spark plasma sintering process

The sintering temperature of pure tungsten can be reduced through the addition of small amounts of transition elements. The present study deals with the activated sintering of tungsten with 1.0wt% additions of copper, cobalt, molybdenum, iron and nickel using the spark plasma sintering (SPS) technique. The alloys were sintered at 1200 degrees C and the mechanical properties and microstructures were compared with those of conventionally sintered alloys, sintered under vacuum condition. The high-rate sintering of SPS has led to an overall reduction in process time and also to a better densification of alloys compared with the conventional sintering process. In both the processes, nickel addition is found to be the best activator, followed by cobalt, iron, molybdenum and copper. The addition of copper and molybdenum showed only a meager increase in the relative density. The alloys, with nickel, cobalt and iron additions, sintered through the SPS process offered much higher density compared with the conventionally sintered alloys. The highest density is observed for the nickel-doped tungsten alloy, which is found to be around 90% of the theoretical density. The microhardness of the sintered alloys is found to depend on its sintered density.