Study On Electroless Plating Ni-Cu-P Composite Technology And Its Properties

Electroless nickel-phosphorus coating has been widely used because of its excellent comprehensive performance,but in recent years,with the progress of science and technology,nickel-phosphorus coating gradually can’t meet the needs of industry,so it is necessary to improve the performance of coating.In this paper,CuSO₄and nanoparticles were added on the basis of nickel-phosphorus coating to prepare a coating with better corrosion resistance.In order to improve the hardness and corrosion resistance of the coating,the optimal composition and process parameters of the plating solution were screened through experiments,and the surface morphology,microstructure,corrosion resistance,hardness and other properties of the coating were tested by scanning electron microscopy,X-ray diffrotometer,electrochemical workstation,neutral salt spray experiment chamber and hardness machine.The main research contents and results are as follows:（1）The composition and process parameters of Ni-Cu-P plating solution were determined by single factor experiment,and then the formula of plating solution was optimized by orthogonal experiment.The results show that the optimal composition of Electroless Ni-Cu-P is as follows:The main salt was 26 g/L Ni SO₄·6H₂O,1.0 g/L CuSO₄·5H₂O,the reducing agent was 24 g/L NaH₂PO₂·H₂O,the complexing agent was 28 g/L Na₃C₆H₅O₇·3H₂O,the buffer was 10 g/L CH₃COONH₄·3H₂O,the stabilizer was 0.5 mg/L sulfourea,the plating temperature was 80℃,The pH value of the bath was 6.0,and the plating time was 1.5h.The hardness of the prepared coating is 479.1HV,the deposition rate is 10.7 mg·cm^-2·h^-1,and the porosity is 0.12 N·cm^-2.（2）On the basis of electroless Ni-Cu-P plating,adding nanoparticles to prepare composite coating,through comparison,it is concluded that adding CeO₂particles has the best effect.The solution composition of composite coating was optimized by response surface method.The results show that:When CeO₂concentration is 0.44 g/L,SDS concentration is 4.47 mg/L and sodium citrate concentration is 27.87 g/L,the maximum hardness of the coating can reach 679.892 HV and porosity can be reduced to 0.0395 N·cm^-2.The Ni-Cu-P-CeO₂composite coating showed better properties than Ni-Cu-P coating.（3）Finally,the Ni-Cu-P coating and Ni-Cu-P-CeO₂coating were heat treated to study the effect of heat treatment on the corrosion resistance,hardness and microstructure of the coating.The results show that the hardness and corrosion resistance of Ni-Cu-P coating are improved by 253.2 HV after 400℃heat treatment.After heat treatment at 450℃,the microstructure of Ni-Cu-P-CeO₂coating changes from amorphous to crystalline structure,and the hardness and corrosion resistance of the coating are improved.