| The chemical deposition of Ni-P and Ni-P-Cg coatings on titanium surface were carried out. Firstly, the influence of improved activation process on the deposition rate of coatings and the adhesive force between the coating layer and matrix were investigated. Secondly, it had been systematically investigated that the effects of surfactants on the coatings properties by orthogonal experiment, and then the optimized processes of electroless plating Ni-P-graphite on titanium alloy were put forward. Thirdly, the crystallization processes of Ni-Pand Ni-P-Cg coatings were analyzed, the crystallization kinetic equations of coatings were carried out.Supersonic technique was introduced into the existing activation process, and then the activation process was completed by ultrasonic action. Choose the deposition rate, the adhesive force between the coating layer and matrix and surface morphology as indexes to research and compare the improved activation process.The results indicated that supersonic technique shorted activation time, reduced dissolved quantity of substrate, increased mass transfer coefficients of transient zinc layer, fined its microstructure, while enhanced the deposition rate and improved the adhesive force between the coating layer and matrix.It had been systematically investigated that the effects of surfactants, concentration of graphite in the bath and diffusing time by supersonic on the coating properties in this paper. The optimized processes of electroless plating Ni-P-graphite on titanium alloy were put forward by methods of structer, surface morphology, micro hardness and wear value. The results showed that: (1) When HTAB and nonylphenol polyoxyethylene were used in optimum condition, the deposition rate was 16.3mg·cm-2·h-1; amorphous Ni-P-Cg plating was deposited with cellular structure on the surface; the graphite embeded in cellular, displaying flesh flower status; the vol percentage of graphite in the coating was 29.06%; the hardess of coating was 325.2 HV and the wear value was 7.5mg. (2) When HTAB and polyoxyethylene sorbitan monooleate were used in optimum condition, the deposition rate was 13.1mg·cm-2·h-1, the vol percentage of graphite in the coating was 22.50%, the hardess of coating was 439.2HV, and the wear value was 7.3mg. (3) Compouding cationic surfactant hexamine with non-ionic surfactant nonylphenol polyoxyethylene or polyxyethylene sorbitan monooleate, the effects were not ideal.After heat-treatment, the properties of coatings were analyzed by methods of SEM, XRD, EDS, micro hardness instrument and wear test. The results showed that the onset of crystallization temperature was increased due to graphite in composite coating and period of completing crystallization was shortened; Due to appearing rigid enhancement phase TiCx in Ni-P-Cg coating after heat treatment, it caused the really high hardness of coating, and about at 400℃, the hardness of composite coating was the highest-1239HV which was about five times the value of titanium substrate, the wear loss was 4.3mg, and the hardness of Ni-P alloy coating was 960.5HV, the wear loss was 15.6mg.The crystallization kinetic of coatings was studied by differential thermal analysis. The data of non-isothermal kinetics were analyzed and compared by methods of Ozawa, Freeman-Carroll, Achar and Coats-Redfern. The results indicated that characteristic temperature Tm and crystallization activation energy E of Ni-P-Cg coating were higher than Ni-P coating's, however enthalpy value was lower; crystallization activation energies of Ni-P coating and Ni-P-Cg coating were 308.9kJ/mol and 412.99kJ/mol respectively, Pre-exponential factors lnA were 58.03/s-1 and 77.84/s-1 respectively, so kinetic equations were determined.
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