Effects of initial crystal size of diamond powder on surface residual stress and morphology in polycrystalline diamond (PCD) layer

Abstract

Polycrystalline diamond compacts (PDC) were synthesized using diamond powder of average crystal size 3–20 μm by the Ni70Mn25Co5 alloy infiltration technique at high temperature and high pressure (HPHT). The surface residual stress of polycrystalline diamond (PCD) layer was measured using micro-Raman spectroscopy with hydrostatic stress model and X-ray diffraction (XRD). Measurements of the stress levels of PCDs show that the residual compressive stresses range from 0.12 to 0.22 GPa, which increase with the crystal size of diamond. Scanning electron microscopy (SEM) was used to observe the morphology of initial diamond grains and PCD cross-section. The results indicate that PCD has a dense and interlaced microstructure with diamond-diamond (D-D) direct bonding. And the smaller the crystal size of diamond, the better the growth of diamond direct bonding and the smaller the binder metal between diamond boundaries will be.