Study On Technics Of Ni-P-SiC-PTFE Composite Plating

Being their homogeneity excellent corrosion resistance, anti-wear, weldability and other special electric and magnetic properties, electroless plating deposits have widely been applied to electronics, petroleum, chemistry, aerospace, nuclear, automobile, printing, textile, machinery and so on. Varieties electroless composite plating, which have good rigidity, wearability, self-lubricating ability, heat-resistant ability and special decorative ability etc., could be obtained by altering different kinds of matrixes and dispersed particles.In this thesis, the effect of different parameters on Ni-P-SiC-PTFE composite plating and different kinds of surfactants on dispersibility of dispersed particles were investigated.The influences of the concentrations of accelerants, buffers, complexing agents and surfactants on deposition velocity and microhardness of composite plating were studied using orthogonal experimental design. Optimal parameters and composite platings of well filmuniformity and compact structure could be abtained by analysing the technics parameters.The influences of heat-treatment on hardness of coatings were also studied. The surface morphology and composition of the composite coatings were characterized by means of scanning electron microscope(SEM) and energy dispersive X-ray spectroscopy(EDS). Porosity, inoxidability and wearability of the composite coatings were tested. It was shown that lactic acid- sodium citrate used as complexing agent was good for stability of electroless bath, and complex surfactants, which were mixed cation surface active agent with nonionic surface active agent, was better than single surfactant for the wettability and dispersibility of the particles. The influences of various surfactants on deposition velocity and microhardness of composite platings was largest, and that of the concentration of succinic acid took second place. Considered the longevity of electroless bath and deposition velocity, the optimal parameters were followed: surfactants used were complex surfactants, the concentration of succinic acid, lactic acid and aminoacetic acid were 15 g/L, 20 mL/L, 5 g/L, respectively.The microhardness of Ni-P-SiC-PTFE composite platings could reach HV612 after heat treatment at 400℃for 1h. After heat treatment for 1h, the microhardness of Ni-P-SiC-PTFE composite platings were higher than that of Ni-P-PTFE platings, and the wearability was better. The optimal temperature of heat treatment was 300℃. The effect of heat treatment temperature on the friction coefficient was slightly, and all the friction coefficient could reach 0.015.Considered the porosity of the coatings decreased with the increase of the thickness of the coatings, it was optimum that the thickness of coatings was thicker than 20μm.After heat treatment at 300℃for 1h, the inoxidability of the Ni-P-SiC-PTFE coatings was worse than that of Ni-P-PTFE coatings. For the two kinds of composite coatings, the inoxidability of coatings immersed in alkalescence solution was best, and that of coatings immersed in acidic solution was worse.