Sn matrix soft overlays for the three-layer plain bearings were prepared by ECR-DC hybrid sputtering. Overlays with Vickers hardness between 5-20Hv, measured at loads of 49mN, were obtained by using pure Sn and Ag-Sn composite targets with Ag/Sn target area ratios of 0.5/44.5 - 6/39. The hardness of the overlays across the wear scar exhibited progressive increase due to densification of coatings and work hardening during the sliding. The physical and mechanical properties of the overlays were also analyzed by optical microscopy (OM), scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and tribological tests were performed using a CSEM type ball-on-disk tribometer.
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Engine bearing performances were improved by forming overlays using only environmentally friendly materials Ag and C. Ag and Ag-C composite overlays were deposited onto Pb-free bronze layer on plain bearings by electron cyclotron resonance sputtering. Their physical and mechanical properties were analyzed by optical microscopy, scanning electron microscopy, electron-probe micro analysis, X-ray diffraction, and laser Raman spectroscopy. C within the overlay was identified to be a diamond-like carbon and found to be distributed uniformly. Seizure resistance was evaluated by rig test machine and excellent results were obtained for the overlay containing 1.7wt.%C. The damage was not observed on the bearing with this overlay after 100hr engine test.
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A new process for tribo-coatings was developed, where TiN and TiN/MoS2 films of 1~3mm in thickness were deposited by an electron cyclotron resonance - direct current hybrid sputtering system on mirror polished stainless steel or bearing steel flat substrates. Nanoindentation tests showed the increase in hardness from 35 š 5 GPa to 52 š 5GPa by MoS2 inclusion into the TiN matrix. Critical load measured by scratch tests, characterizing the adhesion strength, was found to be 4N and 16N for the TiN and TiN/MoS2 films, respectively. The tribological properties of the films were measured in dry conditions with a CSEM ball-on-disc tribometer and it was found that the super-hard TiN/MoS2 film exhibited lower values of the coefficient of friction than the TiN film. The physical and morphological properties of the films were also analyzed by atomic force microscopy and X-ray diffraction.
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Ag-C composite overlays of slide bearings for automotive use were prepared by ECR-DC hybrid sputtering with the use of Ag-graphite targets. Most part of the graphite was found to be transformed into amorphous diamond-like carbon. The obtained overlays showed excellent tribological properties; low and stable coefficient of friction, low wear rate and high seizure resistance. The optimum C concentration in Ag was found to lie around 1.5wt.%.
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