Abrasive wear of tungsten carbide-cobalt composites. I. Wear mechanisms

Abstract

The anomalies arising from the previous observations of two wear mechanisms during rotary drilling of sandstone with sintered tungsten carbide tools have been resolved by further work on the initial stages of abrasive wear: selective cobalt removal and microfracture of the carbide skeleton are two stages in the overall wear mechanism. In the initial stages of wear, fine abrasive particles preferentially remove cobalt from the surface, thus forming small pits with intergranular facets. This is the rate-controlling step in the wear process. The removal of cobalt appears to lower the fracture strength of the surface layers. Intergranular cracks propagate from the pits, leading to microfracture of the carbide skeleton and a microspalling type of failure of the surface layer. The results indicates the importance of cobalt content and distribution, abrasive debris size and environmental factors in controlling the amount of abrasive wear in rock drilling.