Tribological Properties And Cavitation Corrosion Properties Of N-Al₂O₃/Ni Brush Plating Coatings

The corrosion and wear failure of Marine propeller and crystallizer copper plate is usually repaired by brushing plating nickel failure.In the course of ship operation,The propeller will be caused cavitation corrosion due to the change of pressure,causing bubbles in the sea water to collapse on the metal surface.And high temperature wear is an important reason for failure of crystallizer.In order to improve the performance of the repair layer,the n-Al₂O₃ hard particles were added on the basis of nickel,and the n-Al₂O₃/Ni composite brush plating was prepared on the Cu substrate by pulse brush plating.The effects of different voltage,frequency,duty cycle,addition amount of n-Al₂O₃ particles and annealing of 200⁵00°C on the microstructure and properties of the plating were studied and compared with direct current brush plating to optimize the process parameters.The wear resistance of the composite plating after annealing was investigated at room temperature and high temperature,and the cavitation corrosion behavior of the composite coating under simulated high-speed moving fluid was tested.The conclusion are as follows:?1?The pure nickel coating prepared at a voltage of 10 V for the DC power supply has the best performance;the pure nickel coating prepared at a frequency of 800 Hz and a duty ratio of 80%for the pulsed power supply has the best performance,and the performance of the plating after the addition of the pulse is significant promotion.In a certain range of content,the addition of nano-particles in the plating solution will make the plating crystallize finer,the structure more uniform,and the hardness of the plating will also increase.?2?Friction and wear tests show that the friction coefficient of the composite plating is significantly lower than that of the rapid nickel plating.The dispersed distribution of the nano-particles makes the cut mechanism effect of the worn surface weaken,and the wear resistance is improved.At the same time,the friction coefficient and wear rate of composite plating after annealing at 200-300°C are greatly reduced.With the increase of annealing temperature,the wear mechanism of composite plating gradually changes from adhesive wear to abrasive wear.High temperature friction and wear tests show that the composite plating has the highest friction coefficient and the least amount of wear at 300°C.The wear mechanism is mainly adhesive wear and plastic deformation.?3?The cavitation corrosion test shows that the cavitation erosion of Ni plating is a process of gradually increasing the temperature,while the n-Al₂O₃/Ni composite plating has a cavitation incubation period of 5 h.At this stage,the surface oxygen content of the composite plating increases significantly.After the cavitation entered the ascending stage,the two plating layers began to enter the stable stage and took place between 24 and 48 h.At this stage,the cumulative weightlessness rate changes little,and the accumulated weight loss increases.The addition of nano-particles increases the micro-hardness of the coating and changes the cavitation mechanism,which effectively improves the cavitation erosion resistance of the Ni plating.The cavitation on the surface of the Ni plating is manifested by the massive destruction of the surface layer and the interface.Stamping and smearing and lamellar stripping process.The cavitation erosion process of n-Al₂O₃/Ni composite brushed plating was followed by the exfoliation of the surface clusters,the initiation and propagation of cracks at the interface,and the etch pit failure of the plating.