Plasma enhanced chemical vapor deposition of diamond coatings on Cu–W and Cu–WC composites

• Diamond coatings have been deposited on Cu–W and Cu–WC substrates by MPCVD.
• Various characteristic methodologies indicate the diamond film quality.
• Introduction of W increases diamond nucleation density markedly.
• Formation of WC phase improves interfacial bonding.

In this study, two Cu–W (Cu30–W, Cu40–W) and one Cu50–WC composites (all in wt.%) were synthesized by powder metallurgy and used as substrates for diamond coating in a microwave plasma enhanced chemical vapor deposition reactor. Optical microscopy, scanning electron microscopy, Raman spectroscopy, X-ray diffraction, indentation test and synchrotron-based high resolution X-ray near edge absorption spectroscopy were used to investigate the morphology, composition, microstructures and adhesion of diamond films. The results show that the adhesion of diamond coatings formed on these Cu–W alloy substrates is much higher than on pure Cu substrate. The adhesion improvement is primarily attributed to the reduced mismatch in the thermal expansion coefficients, and the formation of WC phase on the sub-surface of the substrate that strengthens the coating-substrate interfacial bonding.