Tailored Si3N4 ceramic substrates for CVD diamond coating

A review is presented of chemical vapour deposition (CVD) diamond coating of silicon nitride (Si3N4) materials. Microcrystalline and nanocrystalline diamond films were grown using microwave plasma (MPCVD) and hot filament (HFCVD) reactors, respectively. Scanning electron and atomic force microscopy, mu-Raman spectroscopy, low incident angle and classical X-ray diffraction, acoustic emission assisted Brale indentation and thermal conductivity measurements were employed for the full characterisation of the diamondl Si3N4 system. Using these techniques, the nucleation and growth stages as a function of substrate composition and surface pretreatment were characterised, as well as the diamond quality, the existence of residual stresses and the adhesion between the diamond film and the substrate. Based on this study, a tailored material was developed and tested in the machining of hard metal workpieces with encouraging results.