Synthesis of WC-Ni composite powders by thermochemical processing method based on co-precipitation

The synthesis of nano-sized, uniformly distributed WC-Ni powders was studied through co-precipitation of oxide powders followed by thermochemical reduction and carburization. Ni and W oxide complexes were first obtained from their salts' solutions through chemical co-precipitation method by adjusting pH. The precipitated powders were then calcined to obtain a mixture of their oxides as WO3 and NiWO4 which were reduced and carburized simultaneously by carbon monoxide (CO) at temperatures up to 950 °C. ICP and FTIR along with XRD analyses were conducted on the residual solution and powders to investigate the precipitation mechanism. The effect of precursor solution pH on the chemical and morphological uniformity of the powders process was investigated; the optimum value was determined as ∼13. The ICP analysis of the remained solution after co-precipitation indicated almost complete extraction of Ni and W into the precipitates. Proper temperatures for calcination in air, and simultaneous reduction and carburizing in CO were determined through TGA analysis; 550 °C and 950 °C respectively. SEM observation of the material in various steps revealed nano-sized particles in all of them, along with fine distribution of Ni and W elements. XRD analysis of the calcine sample showed the presence of WO3 and NiWO4 and the same analysis for the reduced and carburized sample confirmed the formation of WC and Ni.