| The addition of enhancers and Fillers in the plastic raw materials will accelerate the wear, corrosion and oxidization of plastic mould(made of 2Cr13 mould steel) in the production of plastic, which reduce the service life of plastic mould. To solve this problem, in this paper, the composite electrolytes with PTFE emulsion, MoS2 nanoparticles and CeO2 nanoparticles were respectively prepared on the basis of Ni-W(D) alloy plating bath. Ni-W(D) alloy coatings, Ni-W(D)/PTFE nanoparticle composite coatings, Ni-W(D)/MoS2 nanoparticle composite coatings and Ni-W(D)/CeO2 nanoparticle composite coatings were prepared by electro-brush plating on the 2Cr13 mould steel substrate.The surface morphology and cross-sectional microstructure the composition analysis, bonding strength, micro-hardness, wear resistance, antifriction, corrosion resistance, and high-temperature oxidation resistance of coating were observed and measured. The effect of nanoparticle on the microstructure and properties of coatings were researched. Comparative analysis of microstructures and properties were carried out between composite coatings and Ni-W(D) alloy coating.The results showed that the nanoparticles is distributed uniformly in composite coatings. The bonding interface between the coating and substrate is combined closely with concave-convex combination. There is no clear dividing line between the working layer and transition layer of coating. The addition of nanoparticle releases the inner stress of composite coatings, increases the critical thickness to some extent, and improves the bonding strength of coating and substrate.Nanoparticle content in composite plating solution has obvious effects on microstructure of composite coatings. In certain range of concentrations, the microstructure of composite coating becomes fine and uniform as the increase of the nanoparticle content in composite plating solution, meanwhile the cellular protuberance and the crack of composite coating is reduced obviously. When the addition of nanoparticle increased to a certain extent, due to the agglomeration of nanoparticle, the microstructure uniformity of coating declines and grains become coarse. The more the addition of PTFE emulsion or MoS2 nanoparticles is in plating solution, the lower the microhardness of composite coatings is, and while the microhardness of Ni-W(D)/CeO2 composite coatings is enhanced owing to the addition of CeO2 nanoparticles, especially when the addition of CeO2 nanoparticles is 30g/L it arrive at the maximum.The friction and wear test indicated that the addition of nanoparticle reduces the friction coefficients and the wear loss of coatings. PTFE emulsion and MoS2 nanoparticles presents a significant antifriction effect due to their self-lubricating property, which makes coatings keep smooth after frictional wear. The adhesion wear phenomenon on the surface worn of Ni-W(D)/CeO2 composite coatings is reduced and the plowed wear effect is weakened with the dispersive distribution of hard CeO2 nanoparticles in coatings.The electrochemical corrosion experiment showed that the dispersive distribution of nanoparticle in the coating has little effect on the corrosion resistance of coatings.PTFE nanoparticle increases the self-corrosion potential of coatings and reduces the corrosion current, whose corrosion resistance is the best. MoS2 nanoparticle decreases the self-corrosion potential of coatings and increases the corrosion current, whose corrosion resistance is the worst. CeO2 nanoparticle would not improve significantly the corrosion resistance of coatings.The results of heat treatment experiments showed that the heat treatment enhances the microhardness of coatings, and the microhardness of coatings run up to the highest after heat treatment at 300 ℃ owing to the secondary strengthening. The result of high-temperature oxidation experiment indicated that the oxidation weight gain of Ni-W(D) alloy coatings is relatively serious. Compared with the Ni-W(D) alloy coatings, however, the oxidation weight gain of Ni-W(D)/PTFE nanoparticle composite coatings and Ni-W(D)/MoS2 nanoparticle composite coatings is higher than Ni-W(D)alloy coatings because their oxide films were destroyed seriously. The oxidation degree of Ni-W(D)/CeO2 nanoparticle composite coatings is decreased due to the dispersive distribution of CeO2 nanoparticles in coatings, which improves the high-temperature oxidation resistance of coatings. |
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