Wear-resistant coatings (WRC) can be conditionall split into two main coating groups—those with ‘intrinsi hardness’ (diamond, cubic boron nitride, titanium carbide and those with ‘extrinsic’ hardness (nanolayere and nanocomposite coatings) w1x. Many researchers I the field of physical vapor deposition (PVD), chemical vapor deposition (CVD) and plasma enhanced CV (PECVD) set as their goal the pursuit of high hardness believing that this will provide the ultimate level of wear resistance w2,3x. The view w1x is also that coatings need to have the ability to absorb deformation, i.e. they have to combine an adequate degree of ‘elasticity’ with adequate hardness to fulfill the needs of the tribological contact conditions. The coatings based on a-SiC:H seem to belong to the latter classification. We have shown earlier w4x that such coatings can serve as protective and wear-resistant layers on cutting tools in processing aluminum or titanium materials. Later, Esteve, Lousa, Martinez et al. w5x have shown that PVD carbon-rich a- SiC films on silicon wafers had higher wear resistance than the substrates, in spite of the fact that the amorphous films had low hardness (H) and low elastic modulus (E) (H;6 GPa and E;80 GPa) as compared with those of the crystalline silicon wafers. Hydrogenfree a-Si C , x;0.5, films obtained by laser ablation x 1yx (LAD) and triode sputtering deposition (TSD) w6x exhibit H;30 GPa and E;240 GPa. As a rule, PECVD hydrogenated films have H and E that are about two times lower than the un-hydrogenated counterpart w6x. Cros, Gat and Saurel w7x have shown that the Young modulus increases with Si–C bond density from 196 GPa to 273 GPa for PECVD and LAD films, respectively. An influence of annealing on film properties was studied in Refs. w8–10x. The annealing of a-SiC:H films were performed in vacuum w8–13x, in a nitrogen w13,14x and argon w15x atmospheres. Hydrogen was found to undergo high effusion in the temperature range of 400– 600 ℃. The films after annealing in a nitrogen atmosphere were denser as compared with those annealed in vacuum . Schmid, Eickhoff, Richter et al. choosing annealing temperatures between 450 and 750 ℃ have shown that the stress of PE CVD films changing from 400 to 490 MPa is clearly more affected than the Young modulus having a value of 180 GPa. As far as we can see from literature, the investigations of the effect of annealing on the hardness of a-SiC:H films have yet not been carried out. So, from this short literature review it follows that, when analyzing mechanical properties of a-SiC:H films, only the films with carbon-rich or equi-atomic compositions have been considered. Besides, the tribological properties of the films have been investigated only in two works. Since we have investigated the tribological properties of PECVD a-SiC:H film having the equiatomic composition deposited on substrates of hard alloys earlier, here we present the results investigations of the Si-rich films deposited on silicon crystalline wafers. We shortly characterize as-deposited and annealed a-SiC:H films prepared by PECVD from MTCS. It is shown that wear resistance and high hardness cannot correlate in amorphous hydrogenated Si-rich silicon carbide. Although a-SiC:H films show low hardness, their rather good wear resistance and thermal stability make them suitable as WRC in processing soft materials.
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