Structural Characterization And Tribology Property Of Ni-Cu-P Coating Plated By Electroless Method On Aluminium Alloy

In this thesis, the Ni-Cu-P alloy plating was deposited by electreless plating on thesubstrate of aluminum alloy using acidic plating solution. The chemical composition,micro-structure and properties of the Ni-Cu-P alloy coating, such as thermal stability,micro-hardness and adhesion strength, were studied by X-ray Diffraction (XRD), ThermalField Emission Scanning Electron Microscope (FESEM), Transmission ElectronMicroscope (TEM), Energy Dispersive Spectrometer (EDS), Differential ScanningCalorimeter (DSC), etc. The friction and wear properties of the Ni-Cu-P alloy coatingsas-plated and heat-treatment were examined using a ball-on-disc test machine underdifferent experiment conditions.The test results show that the Ni-Cu-P alloy coating could be obtained using theacidic plating solution. The as-plated coating has the lower porosity and the better bondingstrength. TEM results demonstrate that the as-plated Ni-Cu-P alloy coating was mainamorphous structure, and the coating after heat treatment was main crystalline structure.The detected adhesion strength values were in the range from30to40N. The polarizationcurve experiment indicates the coating has excellent corrosion resistance, its self-corrosionelectric potential of the coating was-0.290V. DSC results show the turning point ofcrystallization of the as-plated coating was around400℃. The deposition mechanism ofNi-Cu-P alloy coating were that atomic group preferential deposition, superimpositionincreasing, extending to a general region, forming, the amorphous structure coating.The tribology test results illustrate that the average friction coefficient and wear rateof the as-plated coating would be increased with the increase of applied load. And it wasfound that the trend was increased firstly, then decreased with the increase of slidingvelocity. The dominant mechanism of the as-plated coating was adhesive wear. After heattreatment, the average friction coefficient and wear rate of the coating were be increasedwith the increase of applied load, and decreased with the increase of applied slidingvelocity. The wear mechanism of the coating after heat treatment was plastic deformationt.The wear rate of the coating after heat treatment was lower than that of the as-plated coating. Obviously, the anti-wear resistance of as-plated coating can be improved bymeans of heat treatment.