VERY HARD SOLID-SOLUTION-TYPE TUNGSTEN CARBON COATINGS DEPOSITED BY REACTIVE MAGNETRON SPUTTERING

Tungsten-carbon coatings have been deposited on stainless steel substrates by reactive magnetron sputtering in Ar-CH4 mixtures. The composition of coatings was determined by electron microprobe analyses. Only the cubic alpha-W phase with an expanded lattice parameter was detected by X-ray diffraction in the W-C coatings containing less than 25 at% of carbon. Since the lattice dilatation of the alpha-W phase increased with increasing carbon content these coatings were assumed to be tungsten-carbon solid solutions. The dilatation of the W crystal lattice and Vickers hardness of the solid-solution-type W-C coatings were measured as functions of the carbon concentration. A lattice dilatation-microhardness relationship was established.