Micro-raman stress investigations and X-ray diffraction analysis of polycrystalline diamond (PCD) tools

A systematic study of the residual stress in the diamond layers of a three-layered polycrystalline diamond (PCD) cutting tool was performed using micro-Raman spectroscopy. The stress was measured cross-sectionally along the center-line of the cutter by determining the Raman shift in each of the three layers and was approximated as being biaxial within the dense outer layer and as being hydrostatic throughout the two inner layers. The stress measured along the thickness of the outer diamond layer is compressive and has an average value of 1300 MPa. The two inner layers of the PCD tool have an average compressive stress ranging from 870 to 950 MPa. These values are in good agreement with other experimental and computer-modelled determinations of residual stress in PCD cutters. Low angle X-ray diffraction (XRD) performed on a separate PCD tool blank confirmed the presence of diamond, tungsten carbide, tungsten and both the low and high temperature phases of cobalt. The high temperature cobalt phase may be quenched in during cooling from the high temperature-high pressure processing conditions.