Study On Preparation And Properties Of Composite Coatings Containing Nano-MoS₂ By Electroless Depositing

In this paper ,Ni-P/n-MoS₂ composite coatings were prepared by electroless plating, the preparation process, microstructure and properties of Ni-P/n-MoS₂ composite coatings were investigated. On the aspect of preparation process, the optimization of base electroless bath, dispersed methods of nanometer MoS₂ particles and the effects of technologic parameters on depositing velocity and n-MoS₂ content were investigated. The surface morphology and microstructure of Ni-P/n-MoS₂ composite coatings were characterized by OM(optical microscope), SEM(scanning electron microscope), XRD(X-ray diffraction) and XPS(X-ray photoelectron spectrometer). The friction and wear properties of Ni-P/n-MoS₂ composite coatings were investigated using M200 ring-block wear tester and Q800 end wear tester by comparing with Ni-P coatings and Ni-P/m-MoS₂ composite coatings. The corrosion resistance of Ni-P/n-MoS₂ composite coatings were investigated by the ways of static state immergence and polarization curves.The results show that:Using optimized base electroless bath, and adding CTAB 10mg/L and Tween-80 10ml/L , nanometer MoS₂ particles that congregates heavily under nature state can be better dispersed;The depositing velocities were obviously affected by depositing temperature , and the depositing velocity reached maximum when T=88°C,but depositing temperature have little effects on nano- MoS₂ content in composite coating . The depositing velocity reached maximum when pH=4.5,the nano-MoS₂ content in composite coating reached maximum when pH=4.4,and when nano-MoS₂ adding volume was 2.0g/L,both depositing velocity and nano-MoS₂ content reached maximum.The microhardness of composite coating increased with the nano-MoS₂ content.The adhering force between coating and matrix was not affected obviously with adding nano-MoS₂ particles. In ring-block wear testing,the wear loss and friction coefficient of Ni-P/n-MoS₂ composite coatings markedly less than Ni-P coatings ,and appreciably less than Ni-P/m-MoS₂ composite coatings.In end wear testing, the friction coefficients of Ni-P/n-MoS₂ composite coatings under different loads have no obvious difference,but the friction coefficients descend lightly with the increasing of friction line velocity; The anti-friction and wear resistance action of Ni-P/n-MoS₂ composite coatings,mainly due to continuous and whole self-lubricating film.The hole ratios of Ni-P/n-MoS₂ composite coatings descend with the increasing of nano-MoS₂ content;The results of static state immergence and polarization curves show that the corrosion resistance of Ni-P/n-MoS₂ composite coatings is not well with that of Ni-P coatings.