Fabrication and application of nano–microcrystalline composite diamond films on the interior hole surfaces of Co cemented tungsten carbide substrates

Nano–microcrystalline composite diamond films are deposited on the interior hole surface of Co cemented tungsten (WC–6%Co) drawing using a squirrel-cage hot filament passing through the interior hole with large aperture by the bias-enhanced hot filament CVD. A new process is used to deposit nano–microcrystalline composite diamond coatings by a two-step hot filament chemical vapor deposition (HFCVD) procedure. Research results show that the as-deposited composite diamond films exhibit nanocrystalline diamond crystallites with grain sizes ranging from 60 to 90 nm and their surface roughness is measured as approximately Ra 220 nm with 4 mm scanning length. The Raman spectrum mainly exhibits three features near 1332, 1560 cm− 1 (G peak), and a weak peak at approximately 1150 cm− 1, which is attributed to the transpolyacetylene. XRD pattern indicates good crystallite quality of the composite films. The as-fabricated diamond coated dies show obvious performance enhancement in the practical application. Comparing with the WC–Co drawing die, the working lifetime of the diamond coated drawing die increases by a factor of above 15. Furthermore, the surface quality of the drawn copper pipes is greatly improved.