Reduction of Co2+ by polyalcohols in the presence of WC surfaces studied by XPS

Article abstract of DOI:10.1016/S0025-5408(97)00019-6

Cemented carbides, widely used in cutting tools, are made by sintering fine particles of WC and Co. So far the production of the sintering material has utilized a time and energy consuming grinding and mixing step. An alternative process to chemically precipitate Co metal directly onto WC particles in solution has been investigated by one of the author groups. A Co salt is dissolved in a suspension of ethylene glycol and WC powder and boiled under vigorous stirring. In the present work, surfaces of WC were studied with X-ray photoelectron spectroscopy (XPS), with Al Kα radiation and synchrotron radiation, before and after various reaction times. These studies were undertaken to further clarify the reaction mechanism in particular the possible existence of a Co²⁺ complex specifically adsorbed on the WC-surface. The morphology of the surfaces was examined with scanning electron microscopy (SEM). The Co precipitation seems to proceed through ordinary heterogeneous nucleation. WO₃ on the surface was reduced by hot glycol. No evidence for Co-complex binding to the surface could be found. This lends support to the use of the developed process for coating other substrate surfaces.