Deposition of Diamond-Like Carbon Films on Inner Wall Surfaces of Millimeter-Size-Diameter Steel Tubes by Plasma Source Ion Implantation

Diamond-like carbon (DLC) film deposition on the interior surfaces of steel tubes was carried out by plasma source ion implantation. SUS304 austenitic-type stainless steel tubes with inner diameters of 9, 5, and 4 mm were used as substrate tubes. Acetylene was the working gas for the plasma that was generated by applying a negative pulse voltage of -18 kV to the substrates. The surface morphology of the films and the film thickness were observed by atomic force microscopy and scanning electron microscopy. The composition within the film and at the interface was examined by depth profiling with Auger electron spectroscopy and secondary ion mass spectrometry. The film structure was characterized by Raman spectroscopy. The friction coefficient of the untreated substrate and the DLC films was evaluated by a reciprocating sliding test. The DLC film surfaces were smooth, and no special structure was observed on the surface. The DLC film thicknesses, structure, and composition on the interior surface of the steel tube depend, on the one hand, on the gas and pulse conditions and, on the other hand, on the distance from the end of the tube, as well as on the diameter of the tube. A low friction coefficient of 0.2 was derived for the deposited DLC films.