Diamond thin films were deposited using a cyclic growth/etch oxy-acetylene process on tungsten substrates. Growth of SH polytype of diamond was observed in the diamond thin films. Deposition of 8H polytype of diamond was found to be strongly dependent on the process parameters. Two different phases of tungsten carbide which were formed at the substrate/film interface were also identified by X-ray diffraction. Raman spectrum of these samples confirmed the presence of 8H polytype.