Microabrasion of WC–Co hardmetals in corrosive media

In microabrasion, the influences of corrosive carrier media on the mechanisms and severity of 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. Ball cratering is still a technique which is in its infancy, but is yet sufficiently developed for a test programme to be undertaken using corrosive media. In this preliminary study, the technique has been applied to the microabrasion wear of a selection WC-based hardmetals. For the alkaline and neutral carrier media it was found that volume loss was inversely proportional to hardness. This was not in the case for the acidic media. Scanning electron microscopy of the wear surfaces indicated that the breakdown of the hardness–volume loss relationship in the acidic media was due to the coarser carbide grains (i.e. in the hardmetals of lower bulk hardness) remaining in situ rather than being removed by abrasive processes. Longer-term tests indicated that there were transients in the material removal process, giving a higher wear rate at the start of a test.