Comparative kinetic and structural analyses of nanocrystalline WC powder synthesis from pre-reduced W under pure and diluted CH4 atmospheres

W nanoparticles derived from WO3 during heating in H2 were carburized at 900–1100 K in pure, Ar and H2-diluted CH4 atmospheres. It was aimed to elucidate carburization behavior of pre-reduced W powders under various atmospheres and to establish optimal conditions for the synthesis of nanocrystalline WC. Weight measurements, XRD and SEM were used to characterize the products at various stages of the reaction. At 900 K, carburization was limited to the formation of W2C owing to slow C diffusion. At 1000 K, WC particles were obtained within ~ 75 min using the diluted gas mixtures, while under pure CH4 atmosphere carburization reaction practically stopped due to pyrolytic carbon skin formed on particle surfaces where C supply was more than consumed. WC powders with particle size 40–65 nm and grain size 15–25 nm were synthesized at 1100 K in a short time under the gas atmospheres studied.

Research Highlights
► W nanoparticles were obtained from WO3 during heating to 900–1100 K in H2.
► Incomplete carburization of pre-reduced W at 900 K was ascribed to slow C diffusion.
► At 1000 K, WC particles were obtained using Ar and H2- diluted CH4 gas mixtures.
► Carburization at 1000 K in pure CH4 stopped due to pyrolytic carbon formation.
► Nanocrystalline WC powders were obtained at 1100 K in the gas atmospheres studied.