Mechanical and tribological properties of tungsten carbide sputtered coatings

Tungsten carbide (WC) hard coatings have been obtained on steel substrates by an r.f. magnetron sputtering process. Two-layer coatings have been deposited in order to improve the adhesion on steel. The lower layer was tungsten metal and the upper WC layer was obtained by reactive sputtering of the tungsten target in an Ar and methane gas mixture. AES and SIMS confirmed that the WC layer composition depends on the reactive sputtering gas composition. Film microhardness was measured by microindentation, and the coating adhesion by microscratch. Measurement results showed that high hardness coatings can be prepared at a relatively low temperature and that good adhesion on steel is achieved with the two-layer coating. Nanowear measurements showed a noticeable dependence of this applied functional property on the coating compositions.