Preparation And Properties Of Ni-graphene Nanocomposite Coating By Electrophoretic-Pulse Electrodeposition

The problems of easy corrosion and poor wear resistance of magnesium alloy limit its wide application.Ni-Graphene and Ni-GO-CNTs composite coatings were prepared on the surface of magnesium alloy by electrophoretic-pulsed electrodeposition.The surface and cross section morphologies of the composite coating were observed by scanning electron microscope.The phase composition of the composite coating was characterized by XRD.The graphene was characterized by Raman and infrared spectroscopy.The micro-hardness and friction and wear properties of the composite coating were tested by micro-hardness and friction and wear tester.The corrosion resistance of the composite coating was characterized by electrochemical workstation.The effects of duty cycle and CNTs concentration on the microstructure and wear resistance of Ni-Graphene and Ni-GO-CNTs composite coatings were studied in order to improve the wear and friction reduction and corrosion resistance of magnesium alloy,expand the application field of magnesium alloys.The main contents and conclusions of this paper are as follows:(1)Graphene layer was deposited on the surface of AZ91D magnesium alloy by electrophoretic deposition.The effects of solution and dispersant on the stability and dispersity of suspension and the effect of electrophoretic deposition parameters on the amount of electrophoretic deposition were studied.Finally,graphene is dispersed in ethanol absolute with isopropanol as dispersant.The optimized electrophoretic deposition parameters are as follows:The concentration of graphene in electrophoretic solution is 0.2 g/L,isopropanol is 2 ml/L,deposition voltage is 140 V,deposition time is 16 min,deposition temperature is room temperature.(2)Ni-graphene composite coating was prepared on magnesium alloy surface by electrophoretic-pulse electrodeposition.The effect of pulse duty ratio on the properties of composite coating was studied.The results show that the composite coating has the highest microhardness and corrosion resistance when the duty cycle is 60%.The friction and wear properties of the composite coating are the best.(3)The effect of CNTs concentration in electrophoretic solution on the properties of Ni-GO composite coating was studied.The results show that the wear resistance of Ni-GO-CNTs composite coating increases firstly and then decreases with the increase of CNTs concentration.When the concentration of CNTs is 0.04 g/L,the friction coefficient and wear loss of the composite coating are the lowest,which is mainly due to the crosslinking between CNTs and GO,which enhances the physical and chemical properties of the composite coating,and further strengthen the mechanical properties of the Ni-GO-CNTs composite coating.In addition,the friction coefficient of the composite coating can be further reduced because of the self-lubricating and bearing effect of CNTs.