Grooving wear of single-crystal tungsten carbide

The anisotropic nature of tungsten carbide (WC) single crystals has been evaluated in single-tip scratch testing and in multiple-tip abrasion. The single-tip grooves were made with a Vickers diamond indenter and the abrasion tests were performed with diamond and silica grits. All tests were performed on both the prism and basal planes of the WC crystals. A polycrystalline binderless carbide (Bl) was also evaluated. Optical surface profilometry was used to estimate the amounts of displaced, removed and ridge-formatted material in the scratch tests and the wear volumes in the abrasion tests. The scratches and wear scars were studied with scanning electron-, atomic force- and light optical microscopy (SEM, AFM, LOM). In situ studies of the scratch process were also performed. Wear debris were analysed with transmission electron microscopy (TEM). The results show that there are differences in both the amount of wear and the wear mechanisms between different crystallographic directions of WC. Depending on the direction of the slip planes in relation to the groove direction, the wear mechanisms change from ductile (grooves parallel to the slip planes) to brittle (grooves perpendicular to the slip planes). It is also shown that WC tends to wear by a formation of angular rod-shaped wear debris with the slip planes as the preferred surface planes. (C) 1999 Elsevier Science S.A. All rights reserved.