On the influence of PDC wear and rock type on cutting efficiency

This research is concerned with the nature of frictional process taking place across the wear flat of a polycristalline diamond compact (PDC) cutter while tracing a groove on the surface of a rock sample. Results of precise cutting tests conducted with worn PDC cutters confirm previous results obtained by Adachi, 1996 and Lhomme, 1999, indicating that the contact stress and friction angle mobilized across the wear flat are close to the uniaxial compressive strength q and internal friction angle ? of the rock material. However, we show also evidences that the nature of the wear flat interface (roughness) and petrophysical properties of the rock material can drastically affect the magnitude of the contact stress and friction coefficient. These novel results suggest that particular attention should be devoted to the study of the nature and properties (thickness, flow regime,..) of the boundary layer or third body (powder and/or grains) mobilized below the wear flat.