| Graphite-like-carbon coatings were deposited using magnetron sputtering technology in order to study the influence of graphite target current on the microstructure and properties of the coatings. The microstructure of the coatings was observed and analyzed using scan electron microscope, atom force microscope, transmission electron microscope, X-ray diffraction, X-ray photoelectron spectrum and Raman spectra. Furthermore, the electrical resistivity of coatings was tested using four-point probe meter. The thickness, micro-hardness, adhesion and tribological properties of coatings were measured using the ball crater machine, Fischerscope HVS-1000 micro-hardness tester, WS-2005 scratch tester and pin-on-disc tester.The results show that the surface of coating was typical island structure cluster, when the graphite target current increased clusters of the coating surface became bigger and higher and the surface roughness increased. The analysis of SEM and TEM indicated that the graphite-like-carbon coating was a kind of composite gradient coating , we can divide the coating into three layer above the substrate—Cr sublayer, transition layer and carbon layer, the Cr sublayer was typical columnar crystals, the C content increased gradually above the Cr sublayer in the transition layer which contained nanocrystals. The carbon layer was mainly armorphous structure, element Cr enriched when the target current was low and gradually dispersed into the carbon layer with the increment of graphite target current. The electrical resistivity under different target current was between 10-5 and 10-7（Ω/m）, this result indicated that the graphite-like-carbon coatings had good electrical conductivity and there was mainly sp2 valence bond in the carbon layer, the sp3/sp2 ratio increased first and then decreased with the accretion of graphite target current.When the graphite target current changed from 0.5A to 2.5A, the thickness and deposition rate increased, the intrinsic hardness of coating increased first and then decreased, the maximum hardness appeared when the graphite target current was 1.5A. The result of scratch test indicated that when the target current was low it’s easily to scratch to the substrate so the coating couldn’t withstand high load, lamina spall appeared in the trace when target current was too high, the optimum bonding strength was when target current was 1.5A. The friction coefficient under different load increased while the ratio wear rate decreased first and then increased with the accretion of graphite target current. |
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