Research On Preparation Of Ni-P-GO Electroless Composite Coatings And Properties

Electroless composite plating is added the particles on the basis of the original electroless plating. Electroless composite plating improve the wear resistance, corrosion resistance and other properties of the composite coatings by particle characteristics, such as high hardness, self-lubricating and high stability. Graphene has a stable two-dimensional structure, known as the world’s most hard materials, has excellent physical and chemical properties, so graphene oxide as the third phase particles are added to the preparation of Ni-P-GO composite layer, the system research of corrosion resistance, microstructure and wear resistance of composite coatings.The Hummers method was used to prepared graphene oxide, and characterized by TEM, AFM, FTIR, Raman and XRD. The samples were characterized by AFM, found that graphene oxide thickness self-controlis about 5nm. FTIR characterization showed that the graphene oxide with hydroxyl and carboxyl functional groups. These functional groups contribute to the graphene oxide is dissolved in water, to avoid the agglomeration phenomenon.In this study, the graphene oxide is added to the electroless bath, prepare Ni-P-GO composite coating by mechanical stirring. And the characterization of microstructure and properties of coatings using SEM, EDS, XRD, mechanical testing instrument and electrochemical workstation.In this paper, through the change of carbon content in the XPS, initially identified graphene oxide coating has entered into the compose coating. On the corrosion of coatings were characterized by Raman, it is found that the corrosion of the coatings and the graphene exhibits similar curve by contrast, showed that the graphene oxide into the coating process has become graphene by reducing agent. But because the reaction is not complete, there are some defects in the structure of graphene. The XRD test showed that, the organizational structure of Ni-P-GO composite coatings is amorphous structure. After heat treatment of 200 ℃, coating presents to the crystal transformation trend. After heat treatment of 400 ℃, the plating precipitation Ni3P and Ni phase, into the crystal structure. Heat 600 ℃, crystal precipitation is more evident. Organizational structure change in the coating after heat treatment, to enhance the performance of the foundation.Friction and wear properties of the coating were characterized by mechanical tester. The friction coefficient of the composite coating is significantly lower than that ofelectroless coating, the friction coefficient and the addition of graphene oxide has a certain relationship. When the amount of graphene oxide reached 40 mg/L, friction coefficient of the composite coating is the lowest. Addition of higher GO but the friction coefficient increases, which is due to excessive GO agglomeration together, resulting in friction performance degradation, and test results which are similar microhardness.The coating corrosion test using Tafel curves and AC impedance method. Two methods of test have proved that the corrosion resistance of composite coating is better, especially the coating after heat treatment.The results show that the corrosion resistance of the coating in at 400℃ heat treatment is best.