Influence of the preparation processes on the residual stresses in PCD and PcBN tools

Ultra-hard cutting materials such as polycrystalline diamond (PCD) and cubic boron nitride (PcBN) are increasingly being used as cutting tools in machining. The finishing of cutting tools is challenging due to their mechanical and thermal properties. Both mechanical preparation processes such as grinding and brushing are used to prepare the final contour of the tools. All processes affect the subsurface of the cutting edge, thermally, mechanically, or both. In addition to influencing the cutting edge microgeometry and topography, it is also to be expected that the residual stress state is influenced. In particular for the highly loaded cutting edge, the residual stress state is of major interest, since high cyclic load stresses occur during cutting. A measurement using conventional X-ray diffraction to determine the residual stress state in the cutting edge is not possible due to the very small surface and the strong curvature. For this reason, the influence of the cutting edge preparation methods grinding and brushing for PCD and PcBN on the residual stress state is determined in this work using Raman spectroscopy. For this purpose, the preparation-induced peak shift in the Raman spectrum is determined. This is then converted into absolute residual stresses using previously determined conversion factors.