Oxidation resistant tungsten carbide hardmetals

Abstract

We present a new method for retarding the oxidation rate of hardmetals. By diffusion impregnating a WC-FeCr hardmetal with silicon, we manufacture two-layered silicide coatings consisting of an FeSix outer crust and WSi2 beneath. The structure results from a preferential reaction between silicon and the metallic binder. The FeSix outer layer is crucial to providing oxidation resistance as when exposed to oxygen it passivates, forming a protective SiO2 surface film – while simultaneously preventing exposure of the underlying WSi2, which is known to oxidise in an active manner. Our analysis shows the coating method is applicable to various hardmetals structures.