The use of carbon-based coatings (hydrogenated and non-hydrogenated DLC, doped and alloyed-DLC) is of a wide interest due to its applications in mechanical components submitted to friction and wear including sliding parts in automotive engines. A tribological comparative analysis using a reciprocating (SRV) tester in lubricated and unlubricated conditions with a 4-stroke motor oil has been carried out on six currently relevant state-of-the-art coatings (namely WC/a-C, TiBC/a-C and TiC/a-C:H nanocomposites, Ti-doped DLC, BCN film and a crystalline monolithic TiC film as reference). The quantification of the fraction of the sp 2 -bonded matrix has been done by fitting of C1s XPS peak and the mechanical properties evaluated by nanoindentation.
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2The comparative analysis has allowed us to identify the capabilities of each system This fundamental information would be of relevance for assisting engineers in selecting best partnership for lubrication systems.
The mechanical and optical properties of TiO2 and Al2O3 films deposited by DC reactive magnetron sputtering were analysed as a function of the deposition conditions. Two different sputtering powers and three different voltages targets which influence the pressure and the deposition rate were studied. The voltage corresponds to two different percentages of the turn down set point of the hysteresis curve and fully poisoned condition. As their optical application is the main functionality of these coatings, the transparency and the refractive index were investigated. However, the mechanical properties are the key factors for determining the performance of these systems in use. For this, the wear resistance of these coatings was studied through the analysis of the evolution of the friction coefficient with time and the analysis of the wear track. The corrosion resistance has been also analysed through electrochemical studies. The results reveal that there is a clear influence of the studied deposition conditions on the mechanical and optical properties of these films. However, while general conclusions could be drawn for Al2O3 films, for TiO2 films the tendency is not so clear and further work needs to be performed.
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