Study On Preparation Technology And Bonding Force Of Electroless Nickel Plating On Titanium Alloy Surface

Titanium alloy has excellent properties,such as high specific strength,excellent corrosion resistance,and good thermal stability.It is widely used in the fields of aerospace,medical and health,chemical oil,and marine vessels.However,titanium alloy has a large friction coefficient and poor wear resistance.When used for sliding or transmission parts,the contact parts will produce adhesion,seizure and fatigue damage under the action of micro-motion or mechanical vibration.In order to solve the above disadvantages,the surface modification of titanium alloys is often used in the industry.Electroless nickel deposit has excellent wear resistance and corrosion resistance,and uniformity,and electroless nickel plating is essy to operate.It can be used to improve the wear resistance of titanium alloys.(1)The cross-cut method(GB9286-98)and the pull-open method(GB5210-2006)were used to test the binding forces between the six activated pretreatment electroless nickel plating layers and the TC4 titanium alloy substrate.The bonding force of the obtained electroless nickel plating layer is rated as 0,and the bonding force is good.The bonding force of the copper plating activation pretreatment process is rated as 5,and the bonding force is poor;the secondary zinc leaching activation is measured by the pull-open method The bonding strength of the nickel-plated layer obtained by the pretreatment is the best,which can reach 9.44 MPa,and the bonding strength of the plating layer obtained by the underlying copper pre-treatment activation pretreatment is the worst,which is 3.24 MPa.(2)The friction coefficients of the electroless nickel plating layer and the titanium alloy substrate were tested by a vertical universal friction and abrasion meter,which were 0.2 and 0.46,respectively.The changes in the friction and wear amount were measured,and the coating wear amount was 0.3 mg,and the titanium alloy substrate wear amount was 0.5 mg.Wear scars on the surface of the plating layer and the titanium alloy substrate,it was found that there were no furrows on the surface of the plating layer,and the titanium alloy substrate had obvious furrows,which caused severe adhesion and tearing.(3)Scanning electron microscope(SEM)was used to observe the microscopic morphology of the coating surface and the interface of the coating.It was found that the surface of the coating was composed of many uniformly distributed cells,which consisted of many fine particles,in a cauliflower-like shape.Obvious boundary,but without any defects such as voids,which helps to improve the bonding force between the coating and the substrate.The energy distribution analyzer(EDS)attached to the SEM is used to analyze the element distribution at the interface of the coating.No Zn element was found at the interface of the nickel layer,indicating that the pre-treatment of zinc and nickel had a substitution reaction,and nickel was deposited on the titanium metal.(4)X-ray diffraction(XRD)was used to analyze the phase composition of the electroless nickel plating layer.It was found that a typical diffusion-like bun peak appeared at around 2? of 45°.It shows that the coating has a microcrystalline structure,and at the same time,some phases of nickel-phosphorus intermetallic compounds appear such as Ni3P appears.(5)X-ray photoelectron spectroscopy(XPS)was used to analyze the presence of composition on the surface of the coating.It was found that the coating did contain inclusion phases such as Ni3P.