Ni-p-nano-tio <sub> 2 </ Sub> Composite Coating Preparation Process And Performance

Adding nanometer-sized TiO₂ particle in solution of Ni-P electroless plating, ideal composite coating of Ni-P-(nano)TiO₂ was obtained by elctroless deposition, technological parameter and function of the Ni-P-(nano)TiO₂ composite coating were discussed in this thesis.In the fact of technological process,First,method to obtain the best technological parameters of Ni-P electroless plating with the orthogonal test of four factors that is nickel salt,reducing agent and complexing agent at three different levels. secondly,on the basis of the best technological parameters of Ni-P electroless plating,using orthogonal experimental method of two factors which is the concentration of nanometer TiO₂ particle and surfactant concentration at two different levels. At last,the best technological parameter of the Ni-P-nano(TiO₂) composite plating were obtianed:34g/LNiSO₄·6H2,30g/LNaH₂PO₂·H₂O,17g/L C₆H₈O₇·H₂O,27ml/L C₃H₆O₃,10g/L CH₃COONa,1mg/L Pb²⁺,TiO₂ 2.5g/L,surface activity 16ml/L,plating temperture 90℃,PH value 4.4,plating time 120 minutes.Optimum formula was obtained and a smooth and compact cmposite coating Of 25 mm thick was prepared,the mortphology,microstrcture,microhardness and corrosion resistance of the composite coating were studied by SEM,XRD,microhardness tester,corrosion voltmeter and weight loss method , and compare with Ni-P coating.The experiment results show: In respect of microhardness,the hardness of the nanometer TiO₂ composite coatings after plating and heat treatment in different temperature were higher than that of the Ni-P coatings.composite coating was analyzed with XRD after heat treatment,it is found that structure of the composite coating changed from amorphous state to crystalline after heat treatment at 200℃,and completely crystallized at 400℃.The hardness of the composite coatings after heat treatment was as high as Hv1150. crystallization temperature of the nanometer composite coating increase comparing with the Ni-P coating. In respect of abrasive resistance ,using weighing method show that the Ni-P-(nano)TiO₂ composite coating have better abrasive resistance.In respect of poroness, In respect of binding force,using thermal shock test show that the Ni-P-(nano)TiO₂ composite coating have better binding force.In respect of poroness,the Ni-P-(nano)TiO₂ composite coating have higher porosity than the Ni-P coating.In respect of corrosion resistance,the corrosion resistance were tested with free corrosion potential and dip in nine hours in 10% H₂SO₄ and 15% HCl etchant solution. Experiment show the same result that Ni-P coating have the best function of corrosion resistance and the Ni-P-(nano)TiO₂ composite coating a little worse than the Ni-P coating ,but them all more better than the matrix.In the end,the achievements are summarized,the prospect for the further study in this field is discussed ,and some related imporvement suggestion and measures are given.