MECHANICAL-PROPERTIES, STRUCTURE AND COMPOSITION OF ION-PLATED TUNGSTEN CARBIDE FILMS

Tungsten carbide films were prepared by rf magnetron sputtering of a tungsten carbide target onto high-speed steel (HSS), stainless steel, silicon and platinum. During deposition the substrate temperature remained below 100°C. The substrate potential was varied between 0 and - 120 V. From 0 to -40 V substrate bias we observed a decrease of the deposition rate whereas the intrinsic stress increased from 3 to 8 GPa. Simultaneously, the composition changed from WC1 to ca. WC0.5. The drastic variation of the chemical composition at low plating energies can be explained by a simple sputter model. With higher negative substrate potentials the films became harder (ca. 4500 HV 0.025) and denser. The adhesion to the substrates increased as well. SEM micrographs of such films deposited onto a non-biased substrate showed a less dense zone I structure. The crystal structure of the films, investigated by X-ray diffraction, was found as that of β-WC1-x and α-W2C. The stress can be reduced by adding approx 1% C2H2 to the working gas. © 1990.