LOW-FRICTION AND WEAR-RESISTANT A-C-H A-SI1-XCX-H MULTILAYER COATINGS/

Amorphous hydrogenated carbon a-C:H and silicon alloyed a-C:H (a-Si1-x Cx:H) films were combined into a multilayer coating by alternatively a dding silane to methane in a conventional capacitively coupled paralle l plate r.f. plasma assisted chemical vapour deposition process (r.f. PACVD). The multilayer structures were revealed by Rutherford backscat tering spectroscopy (RES) and their mechanical properties were determi ned by depth sensing indentation. The tribological behaviour of variou s multilayer combinations was studied by ball-on-disk testing. The r.f PACVD technique allowed to produce multilayer coatings with varying c omposition modulations and sharp interfaces. The mechanical properties of the a-C:H/a-Si1-xCx:H multilayer coating were situated in between those of its constituents. By optimising the a-Si1-xCx:H sublayer comp osition, sublayer thicknesses and thickness ratios, top layer composit ion and total thickness of the multilayer, a true low friction and wea r resistant coating was obtained showing a friction coefficient below 0.1 under a relative humidity of 50% in air together with a wear resis tance comparable with that of pure diamond-like carbon.