TRIBOLOGICAL BEHAVIOR OF HARD CARBON COATINGS DEPOSITED ON STEEL SUBSTRATES BY PLASMA-ASSISTED CHEMICAL-VAPOR-DEPOSITION

We have tested the tribological behaviour of steel probes with various diamond-like coatings in a vacuum shell and under various environment s against steel. We obtained the coatings by plasma-assisted chemical vapour deposition. Experiments show good adhesion of these coatings to the substrate and good resistance to high shear stresses. This paper presents experimental results for several diamond-like coatings (DLCs) , permitting an identification of the tribological behaviour of each c oating structure. Coatings with a high electrical conductivity, which indicates the presence of graphite within the DLC, exhibit very good t ribological properties: low friction coefficients and very low wear ra tes. Adsorbable gaseous environments lead to a decrease in the frictio n coefficient. Diamond-like coatings without the graphite structure sh ow a very different tribological behaviour. The presence of water vapo ur or other active gases such as oxygen leads to an increase in the fr iction coefficient.