Influence of binder metal on wear initiation of cemented carbides in sliding contact with granite

Drill bits equipped with WC-Co cemented carbide buttons offer great performance in many rock drilling applications. Generally, the wear of these buttons against the rock is gradual and moderate, or even slow depending on the rock conditions. However, the Co binder has recently been found to cause health issues and an alternative binder, which does not compromise the performance of the cemented carbide, is needed. In the present work, the performance of WC-Fe and WC-Ni is investigated and compared to the common WC-Co in a sliding test against granite. The results show immediate scrape-off of granite against protruding WC grain edges. Some WC grains crack and fragments are subsequently removed, adding up to loss of entire WC grains. A nanoscale pattern gradually evolves on other WC grains, implying also nanoscale wear. Both WC-Fe and WC-Ni show significantly faster wear initiation and early propagation compared to WC-Co, although the wear characteristics are similar.