Determination of wear mechanisms by stepwise erosion and stereological analysis

In erosion and abrasion, the detailed processes that cause material removal are still poorly understood. This means that with a few notable exceptions, good models for the prediction of materials behaviour are still not readily available. Stepwise testing is a new approach that has been recently developed as a way of providing information on the build up of damage in erosion. The technique uses a combination of exposing a test sample to repeated very low duration abrasion or erosion followed by accurate relocation in the SEM. This enables the real wear processes within a material to be followed in considerable detail, giving an excellent basis for developing new and improved models. In an earlier preliminary study [M.G. Gee, R.H. Gee, I. McNaught, Stepwise erosion as a method for determining the mechanisms of wear in gas borne particulate erosion, Wear 255 (2003) 44–54.], the technique was applied to the gas borne particulate erosion wear of a high speed steel and a WC/Co hardmetal. In this paper, the technique has been applied to two further WC/Co alloys with a coarse and a fine grain size. It was found that the predominant mechanism of wear was the fracture, fragmentation and removal of individual WC grains following the accumulation of plastic deformation, coupled with the removal of cobalt binder from the wear surface, undermining the WC grains.