Boron nitride thin films deposited by RF plasma reactive pulsed laser ablation as interlayer between WC-Co hard metals and CVD diamond films

Thin films of boron nitride have been obtained by reactive pulsed laser ablation of a boron target in the presence of a 13.56 MHz radio frequency nitrogen plasma. The films have been deposited at several substrate temperatures, using the on-axis configuration, on WC-Co cutting tools, after Co removal by chemical etching (HCl/HNO3 or HF/HNO3). Diamond polycrystalline films of increasing thickness have been deposited by HF-CVD at different methane percentages. Cross-sections of the coated samples have been characterised by scanning electron microscopy, while the film quality and interface stress of multilayer structures have been evaluated by Raman spectroscopy. The boron nitride thin film crystallisation and the adhesion optimisation of the whole structure have been studied by varying the deposition parameters, such as the substrate temperature and the nitrogen gas pressure.