WEAR OF ROCK-CUTTING TOOLS

AbstractThe conditions under which carbide-tipped rock-cutting tools are employed are very much more severe than any experienced under metal-cutting conditions, vibration of the cutting machine being very significant. Cutting rock also tends to be an intermittent process.Once macroscopic chipping of the cutting edge has been overcome, the predominant mechanism of wear appears to be one of microfracturing of the surface layers, probably a high-strain-fatigue type of failure. For this reason pure WC–Co grades are usually employed for greater fracture-resistance, rather than other grades of cemented carbides. However, other mechanisms of wear are also probably operative, corresponding to abrasive mechanisms, and becoming more important as higher temperatures are generated. Recent hardness measurements indicate that at the temperatures generated in the carbide tip, especially when cutting quartzitic rock, grains of the rock material could well be harder than the tool material. At the wear flat, where a certai...