Novel X-shape filtered arc deposition (X-FAD) apparatus is specially designed and newly developed for thick hydrogen-free tetrahedral amorphous-carbon (ta-C) film coating on superhard alloy (or cemented carbide) substrate. The apparatus has a graphite cathode for deposition of hydrogen-free diamond-like carbon (DLC; ta-C and amorphous carbon: a-C) film and a chromium (Cr) cathode for deposition of Cr layer. The filter duct shapes a composed form of a T-shape filter (T-FAD) for DLC film and a crank-shape filter (Crank FAD) for Cr film. Both carbon plasma beam and Cr plasma beam finally pass through a common plasma duct and scanner part, and go forward to the substrate.
It is known that the adhesion of ta-C film to the superhard alloy is not good and the employment of binding interlayer between ta-C film and superhard alloy is one of the solutions. In this paper, using X-FAD, thick ta-C film was prepared on the superhard alloy. Principal results were as follows. (1) Crank FAD remarkably worked to prepare droplet-free Cr film. (2) Cr single layer did not work as appropriate biding interlayer between superhard alloy and ta-C. (3) Multi interlayer composed of Cr, a-C, and functionally graded DLC (a-C to ta-C), worked as a good biding interlayer for ta-C film on superhard alloy with thickness of more than 1 μm.