Study Of Process For Electroless Ni-P-SiC-MoS₂ Composite Plating

As a kind of excellent surface treatment technique, because of simple process, homogeneous and fine coatings, electroless composite plating has been widely developed and applied. MoS₂ is a good solid lubricant and silicon carbide has a higher hardness. So Ni-P-SiC-MoS₂ composite plating has an excellent anti-friction and wear behavior.In this paper, the influences of process parameters on the quality of electroless Ni-P-SiC-MoS₂ composite plating were studied. Firstly, the effects of composite agent on the deposition rate and the life of solution, the surfactants on the particle wetting and dispersion were investigated. And then, the effects of preparing temperature, the addition quantity of particles, the content of surfactant, and the stirring speed on the plating properties, such as the deposition rate, the adhesive strength and the hardness of plating, were discussed by the orthogonal test method. Ni-P-SiC-MoS₂ plating with uniform thickness and compact structure was obtained. The effects of heat-treatment process on the hardness and the adhesive strength of plating and the content of surfactant and temperature on the plating-matrix adhesive strength were studiedalso.It is shown that the method with the citric acid-acetic acid electrolyte solution has a higher plating speed and solution stability. The composite surfactant composed by cationic surfactant and nonionic surfactant is better than single surfactant to the particle wetting and dispersion. For the depositing rate, the most significant influence factor is preparing temperature, and the next is stirring speed. For the plating hardness, the most is the addition quantity of particles, and the next is stirring speed too. The best technology conditions are as follow: 90℃solution temperature, 60mg/l surfactant content, 240r/min stirring speed, and 6g/l particle addition.After heat-treatment at 400℃for 1 hour, the hardness of composite plating can reach HV1096. Prepared at 90℃and 60mg/l of surfactant content the plating-matrix has a bigger adhesive strength.The results of anti-friction and wear experiment indicate that the friction coefficient and the mass loss of Ni-P-SiC-MoS₂ plating were much less than these of Ni-P-SiC plating.The porosity of plating decreases with the plating thickness increase. The porosity of plating approached zero when the plating thickness of the samples is 22.3μm after heat-treatment.The corrosion resistance of Ni-P-SiC-MoS₂ composite plating after heat-treatment is inferior to that of Ni-P composite plating. The corrosion resistance of those plating is better in alkaline solutions, and poor in acidic solutions.