Study On Self-Lubricating Composite Coatings With Ni-Based Electroless

With the rapid development of science technology and industries, the Ni-P coatings has cannot satisfied the engineering need. Composite coatings containing lubricating particles are receiving more and more interests. Especially the mechanical and tribological properties of the electroless Ni-P coatings can be improved by the incorporation of solid particles of lubricants such as PTFE, graphite, MoS2, etc. Due to its non-stick nature, non-galling, excellent dry-lubricity, low friction, good corrosion and wear resistance, these composite coatings have broad application prospects.In this work, electroless composite plating with PTFE,graphite and MoS2 particles was studied to achieve composite coatings with low friction coefficient. A comparison study of the properties of Ni-P, Ni-P-PTFE, Ni-P-graphite, and Ni-P-MoS2 composite coatings was conducted. Simultaneously, the effects of PTFE, graphite and MoS2 particles, surfactants, temperature and pH value of the electroless bath on the deposition rate of the coatings were investigated. As a result, the optimized electroless bath and operating conditions were obtained. The final products were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectrometer (EDS), X-ray powder Diffractometer (XRD), Atom Force Microscopy (AFM), Contact Angle measuring device and frictionometer. The results showed that self-lubricating Ni-P-PTFE, Ni-P-graphite, Ni-P-MoS2 composite coatings can be prepared by electroless plating.The content of PTFE, graphite, MoS2 particles in the prepared composite coatings is 11%, 21.6% and 5.5% respectively, which distributed uniformly in the amorphous Ni-P coatings. The diameters of these codeposited particles in the coatings are 12μm, 1μm~4μm和0.2μm~3μm respectively. The thickness of Ni-P-PTFE composite coatings is 12μm, the corresponding porosity ratio is 0.2·cm-2. The thickness of Ni-P-graphite composite coatings is 31μm, the porosity ratio is 0.1·cm-2. The thickness of Ni-P-MoS2composite coatings is 65μm, the porosity ratio is 0 cm-2. With the codeposited particles, the prepared composite coatings are of high relative density.The contact angle of Ni-P-PTFE composite coatings prepared in the optimized electroless bath and operating conditions is about 108°, much higher than that of Ni-P coatings. All the prepared composite coatings have low friction coefficient, the lowest friction coefficient of Ni-P-MoS2 composite coatings in our experiment can reach 0.026.