Study On Preparation And Tribological Properties Of Electro-brush Plating Ni-P/Al₂O₃/Graphene Composite Coatings

Due to the influence of marine environment and special working conditions,many sliding parts in ship field are faced with the duality of wear and corrosion resistance.Therefore,self-lubricating functional coatings with high hardness,wear resistance and corrosion resistance has become an important research direction in the field of ships.Nano-composite brush plating technology is an important technical means to strengthen the comprehensive performance of mechanical parts and to repair the surface of the workpiece.Meanwhile it is a kind of technological innovation and industrial applicability.Because of the unique advantages in the marine components functional coating preparation and repair,it has become the current development trend of engineering technology.In this paper,according to the performance requirements of corrosion-resistant sliding parts in marine environment,nano-composite brush plating technology,which is convenient for on-line repair,is used to prepare wear-resistant and multi-friction composite brush coating to enhance the comprehensive performance of parts and prolong the service life of parts.Firstly,in this paper,the composition of coating materials is designed based on the analysis of the failure mechanism of marine environment and parts,and the brush pen is prepared by the analysis of the principle of brush plating.On the basis of plating Ni-P coatings,nano-Al₂O₃ and graphene particles are added to prepare the composite coating with both wear and lubrication.In order to make the nanoparticles uniform and stable in the brush plating solution,it is preferable that the appropriate surfactant disperses the graphene particles.Meanwhile The Al₂O₃ Sol is prepared by the hydrolysis method of organic alkoxide to solve the problem that the addition of Al₂O₃ powder is easy to agglomerate.Then,nano-Al₂O₃ Sol and oxidized graphene dispersion are added to the watt plating.Ni-P,Ni-P/Al₂O₃,Ni-P/graphene and Ni-P/Al₂O₃/graphene are prepared on the basis of obtaining stable composite bath.The surface morphology,microhardness,tribological properties and corrosion resistance of the coatings are tested by scanning electron microscopy?SEM?,micro-sclerometer,friction-wear tester and electrochemical workstation.The effects of pH value,working voltage,brushing speed,brushing time,Al₂O₃ Sol content and graphene concentration on the microstructure and properties of the coating are studied,and the process parameters are optimized.The tribological properties of Ni-P/Al₂O₃/graphene composite brush coatings are tested by friction and wear tests.The friction and wear mechanism of Ni-P/Al₂O₃/graphene composite coatings ia tested.The effects of brushing process parameters,nano-particle content and tribological properties are studied.The results show that the existence of graphene reduces the friction coefficient of Ni-P coating,and the friction coefficient can be as low as 0.12 under the appropriate process parameters.The addition of Al₂O₃ Sol improves the wear resistance of the coating,and the wear amount is the smallest when the working voltage is 14V.The wear mechanism of Ni-P/Al₂O₃/graphene composite brush coatings is mainly abrasive wear and fatigue wear.In order to further improve the compactness and comprehensive properties of the coatings,the brush coating is post-treated at different temperatures,and the effect of heat treatment temperature on the microstructure,microhardness,corrosion resistance and tribological properties of the coating is studied.The results show that the heat treatment temperature directly affects the microstructure of the composite coatings,which has a great influence on the wear resistance,friction reduction and corrosion resistance of the coating.In the heat treatment temperature of 400?,the composite coating surface is fine,uniform,smooth and no cracks.Meanwhile,the hardness has been greatly improved and the value is up to 869.8HV.The coating with good wear resistance and low friction coefficient has been obtained.