Preparation And Tribological Behaviors In Seawater Of CrAlN Coating

The components subjected to the interaction of corrosion and friction in marine lead to instability even failure of the marine engineering equipment.It is believed that coating technique would be an effective way to improve the reliability of the equipment.In this work,Several Cr_1-xAl_xN coatings with different Al content were deposited on 316 L stainless steel via multi-arc ion plating.The optimal Al content of CrAlN in seawater was confirmed by compared the microstructure and tribological performance of Cr_1-xAl_xN coating.In order to further optimize the tribological behavior of Cr AlN Coating in seawater,the bias voltage of substrate was changed to ameliorate the structure of CrAlN coating.Moreover,an investigation was made into the tribological performances of CrAlN coating sliding against five ceramic balls in seawater.The ascertainment of the best friction pair mate was given by analyzed and discussed the wear mechanism of CrAlN/ceramics.1.With the increasing of Al,the hardness firstly increases and then decreases,with a maximum value of 28.5 GPa at 45 %.The columnar structure is disappeared gradually and a dense glass –like microstructure is observed and then returns the columnar structure when the Al content is above 65 %.It is the structure texture of the coatings that determined wear loss when Al content is below 65 %.The dominant phase in CrAlN coating above 65 % is AlN?002?,which is an easy hydrant phrase in water,which result in catastrophic spalling of AlCrN coating.The CrAlN coating with Al content of 65 % exhibited optimum tribological performance in both environments.2.The surface of CrAlN coatings is significantly determined by bias voltage of substrate.With the increasing of bias voltage of substrate,the size of particles on the surface of coating is decreased gradually,while the number of the particles firstly decreases and then increases.The wear rates of coating are influence by surface toughness when the bias voltage is low.The rougher of the surface,the longer of the run-in period.Loacal spalling occurs when the coating is fabricated at higher bias voltage enough,which was due to the lots of cracks occurring in the coatings and as a passageway for seawater to the substrate.The coating deposited at a bias voltage of-80 V exhibit optimal mechanical and tribology properties.3.Tribological performances of AlCrN coatings coupled with Si₃N₄,SiC,WC,Al₂O₃ and ZrO₂ balls were comparatively studied in air and seawater.Results showed that the tribological performances of different tribopairs depended on the nature and wear behaviors of the coupled ceramics.Seawater plays an important role in decreasing the friction coefficient by forming tribochemical films and fabricating hydrodynamic lubrication regime.However,the wear rates of AlCrN/ceramics are larger or smaller compared with ambient air environment due to the different functions between ceramics and seawater.The micro-dimples in the SiC balls could act as a reservoir of SiO₂ and wear debris,which could enormously reduce the friction coefficient and wear rate.Compared with other ceramic balls,the AlCrN coating sliding with SiC ceramic exhibits more excellent tribological properties.