Formation of Q-carbon and diamond coatings on WC and steel substrates

Recently we reported the formation of diamond and a new phase of Q-carbon, harder than diamond, on sapphire (0001) substrates by direct conversion of amorphous carbon layers by nanosecond pulsed laser melting or annealing. Here we show that this process can be extended to other substrates, specifically WC (Co-bonded) and steels that are needed for high-speed machining and oil and gas exploration and biomedical applications. Since diamond and Q-carbon layers are formed via laser melting and quenching of carbon, these layers are quite adherent to the substrates, thus solving a critical adhesion problem associated with initial graphitic layers in CVD diamond coatings. We have used these Q-carbon, diamond and Q-carbon-diamond composites as seed layers for HFCVD (hot filament chemical vapor deposition) to grow thicker and more adherent layers of diamond. [Display omitted] •Formation of Q-carbon and diamond coatings on WC-Co and steels.•PLA and HFCVD diamonds formed are largely strain free.•PLA results in direct conversion of amorphous carbon into diamond and Q-carbon.•The whole conversion process is completed in less than fraction of a microsecond.•Q-carbon based coatings are more adherent because of the interfacial melting during the conversion process.