Investigation on microstructures of typical particles in plasma spheroidized WC-Co powder

Abstract

Spheroidized WC-Co powder has more complex morphologies than other spherical powders. To investigate this phenomenon, this study divides spheroidized WC-Co powder into five categories based on the morphologies of WC grains and whether the WC grains were completely melted in plasma torch and discusses in detail their surface morphologies and formation mechanisms. It is found that the growth mechanisms of the typical particle A during spheroidization are dissolution-precipitation and aggregation and growth mechanisms. Furthermore, typical particle B has high spherical shapes, and its increased free carbon content suppresses the anisotropic growth of WC grains, leading to a transformation of the WC grains from needle-like to fine grains. Finally, typical particle C has coalescence of WC grains, and the free carbon may accumulate on the surface of black particle to form a shell, which can cause blurred SEM images.