Study On The Ni-P Alloy And Namo Composite Coating

In this paper, the techniques of electrodepositing Ni-P alloy coating and Ni-P-CNTs nano-composite coating from phosphorous acid system are investigated. Effects of technical conditions and heat treatment temperature on the surface morphology,structure and properties of electrodeposit are discussed. Wear resistance properties of Ni-P alloy coatings and Ni-P-CNTs nano-composite coatings are compared,and on th ebasis of that the wear resistance mechanism is analyzed.Ni-P alloy coating was prepared by pulsed electrodeposition. It has been found that a reasonnable pulse parameters can improve appearance quality and deposition rate of the coating. By the method of SEM to analyze the structure of alloy coating, it has been noticed that if the average current is big and the pulse width is small then the deposition rate will be more fast, and the grain refinement effect of the coating will become worse if duty ratio increases. Corrosion resistance test on Ni-P alloy coating reveals that under high-frequency conditions the coating exhibits excellent performance in corrosion resistance. Duty ratio has significant impact oncorrosion-resistant of the coating.and it will show excellent resistance to corrosion when duty ratio is the smallest.In order to improve the dispersion of CNTs in aqueous solution, the CNTs are modified by the cetyl trimethyl ammonium bromide (CTAB) and citric acid (CA), respectively, and the dispersion properties in aqueous solution are studied. The experimental results illuminate that the dispersion of CNTs in aqueous solution is improved by modification. Furthermore, the dispersed mechanism of MWNTs in de-ionized water was discussed through the study of Zeta potential analyzer and viscosity meter.Carbon nanotube was used as a reinforcement agent to prepare Ni-P matrix composite coating. The tribological behaviour of the composite coating was examined on a reciprocating wear test machine. The surface morphology before and after wear test were analyzed with scanning electron microscopy. The results show that the carbon nanotubes were uniformly embedded in the matrix and one end protruded from the surface. It is found the Ni-P-carbon nanotube composite coating have high wear resistance and self-lubrication. CNTs layer on the matrix protect the surface of the matrix from wearing. Meanwhile the incorporation of the CNTs suppresses the plastic deformation and enhances the mechanical properties of the coating.