Grinding of WC–Co hardmetals

This paper concentrates on the morphology of the ground surface of cobalt tungsten carbide (WC) composite materials that belong to the category of so-called hardmetals. A deformed and detached surface layer was found on top of the specimens after surface grinding with a diamond wheel. In order to determine aspects of material removal, various routes were followed. Etching the surface layer revealed WC grains in the subsurface of the machined samples. Most of these grains were plastically deformed by prismatic slip in the hexagonal lattice of WC. Also cracks were found in these grains. Further, the increase in residual stress due to the grinding process was examined by X-ray diffraction (XRD). The stress increases to a maximum stress in the carbide grains before the relaxation occurs by slip and cracking. The surface roughness after grinding was measured by scanning confocal microscopy. Roughness exponents were calculated from the 3D profiles and the values of this process were in good comparison with values for grinding ceramics.