Research Of The Preparation And Tribological Properties On The Composite Coating By Electrophoretic-electrochemical Deposition

Composite coatings are widely used in industrial production and other fields, because itpossesses the double outstanding performance of the matrix metal and solid particles. At present, themethods of particles codeposition with matrix metal have been maturely developed, however there arestill many problems to perfect. For example, there is still be existing the limitation in improving thecontent of particles in composite coatings. The initial research of the non codeposition processindicates that the combination of the electrophoresis and electroplating could improve the particlessignificantly.In this dissertation, the electrophoretic-electrochemical of diamond and other solid lubricativeparticles were carried out in order to prepare the high content of antiwear particles in the compositecoatings. The main researches and conclusions are showed as follows:1. First the appropriate dispersion medium and additives were selected to make up a stableelectrophoretic suspension through the primeval attempt and finally the electrophoretic deposition ofthe diamond etc particles were successful achieved. The main parameters in effecting the depositionwere established, such as: the concentration of particles in solution, the amount of the additive（MgCl₂·6H₂O）, electrophoretic deposition voltage and time.2. The influence of the main parameters on the electrophoretic deposition quantity anddistribution of diamond particles were studied via orthogonal test. The results showed that, theaddition of MgCl₂·6H₂O had the optimum value under the same experimental condition and also hada significant effect on the distribution of diamond electrophoresis layer. All of the other threeelectrophoretic parameters had a positive correlation relationship with the amount of electrophoreticdeposition.3. The same method was also applied to the assessment of the composite coatings structure andperformance. Besides the electrophoretic parameters, the electric current density was also considered.The results of range analysis indicated that electric current density had the greatest impact on thedeposition rate. According to the microhardness, surface roughness and friction coefficient of thecomposite coatings, MgCl₂·6H₂O and electric current density were the main influence factors. Themass fraction of the diamond in composite coating could reach up to48%and the wear rate of thecomposite coating that achieved under appropriate parameters could hardly be tested, which possessedhigh abrasion resistance property. 4. MoS₂, CaF₂and other solid lubricative particles were taken into theelectrophoretic-electrochemical process. It was found that expect PTFE, MoS₂and CaF₂could realizeelectrophoretic deposition. While, the effect of MoS₂deposition was poor, the obvious crackphenomenon was found. The following step with the electroplating was conducted. The surface roughof Ni-MoS₂composite coating was high, which appeared like mushroom shape. The two stepdeposition method was well applied to CaF₂particles. The phenomena that generated above may becaused by the difference of solid particles in their inherent properties.