The effect of phosphorus additions on densification, grain growth and properties of nanocrystalline WC–Co composites

Abstract

To control the grain growth of nanocrystalline WC–Co cemented carbides by phosphorus (P) doping was studied in spark plasma sintering (SPS). Experimental results show that the use of small amount of phosphorus dopant to chemically-activated sintering of the nanocrystalline WC–Co composites could enhance the sinterability, promote the low temperature densification, and decrease the sintering temperature of the WC–Co nanocomposites. With only 0.3wt.% P additions, full density WC–7Co cermets were obtained at temperature as low as 1000°C, which is 100°C lower than that of the undoped counterparts in spark plasma sintering of the nanocomposites. By phosphorus doping in WC–Co nanocomposites, the grain growth of WC–Co cemented carbides could be inhibited to some extent, as a result WC–7wt.% Co–0.3wt.% P cemented carbides with average WC grain size of 200nm were achieved, which can be attributed to the lower sintering temperature resulting in a decrease of grain boundary mobility. Mechanical properties measurements show that P doping could lead to a great increment of hardness, but at the same time a little sacrifice of fracture toughness of the nano-WC–Co cemented carbides.