Adhesion and wear resistance of CVD diamond coatings on laser treated WC-Co substrates

A novel method using a high power diode laser to selectively remove cobalt binder from the outermost layer of Co-cemented tungsten carbide (WC–Co 5.8 wt.%) is hereby discussed. A continuous 940-nm wavelength diode laser source at power of 600–1500 W and scanning speed of 1 mm/s was used to perform the thermal treatments. Hot Filament-Chemical Vapour Deposition (HF-CVD) was then used to deposit PolyCrystalline Diamond (PCD) coatings. Increasing the laser fluence, Co-binder was progressively and selectively evaporated from the WC–Co substrate. The selective removal of the Co-binder from the outermost layer of WC–Co induces a significant corrugation of the substrate, very promising to deposit on it high quality diamond with improved adhesion. Indeed, too much high laser fluence must be avoided, as it would tend to induce the resintering or the local melting of the tungsten carbide grains.