How can H content influence the tribological behaviour of W-containing DLC coatings

摘要

In this paper, the influence of the addition of W and H to pure DLC coatings on the structural, mechanical and tribological properties will be presented. The coatings were deposited by r.f. magnetron sputtering from a C target embedded with different numbers of W pellets. Working in non-reactive or reactive atmosphere allowed to deposit H-free or H-containing coatings, respectively, on steel and Si substrates. A Cr adhesion interlayer was interposed between the films and the substrate. Films with W content from 0 to 12 at percent and H incorporated up to a maximum value close to 40 at. percent were deposited. All coatings had an amorphous structure, although vestiges of crystallinity could be detected in W-containing films. The addition of W led to a significant hardening of the DLC coating (from ~ 10 to 18 GPa); inversely, with H incorporation the hardness drop down to values even lower than that of pure DLC films. It was possible to establish a good correlation between the hardness and the residual stresses. In spite of decreasing friction and wear coefficients when alloying DLC with W, almost no difference was found among the W-DLC films whatever the W content was. A similar trend was achieved with the H addition. However, in this case a decrease in the friction coefficient was registered whereas the wear rate increased. The best performance concerning the friction was obtained for an H-containing coating (0.05) whereas, for the wear resistance, H-free W-DLC films were better performing (0.3 X 10~(16) m~3 N~(-1) m~(-1)).