Aluminum Alloy Substrate Ni-sic Composite Coatings Technology

The technique for electrodepositing Ni-SiC composite coating and the pretreatment method for aluminium alloy substrate were investigated in this paper. The process conditions have been obtained for good wear resistance on the surface of aluminium substrate. The influence of technological conditions such as cathodic current density, pH, temperature, agitation and especially the surfactants on the property of Ni-SiC coating were investigated in detail. The composition, structure and morphology of the coating were analyzed by using XRD, SEM and ED AX methods. The microhardness, wear resistance and behavior of anti-corrsion and anti-oxidation of Ni-SiC composite coating were investigated. The results show:( 1 ) Non-ions surfactants F-l inhibites SiC particle incorporation in the deposits, but anodic-ions surfactants especially XCG can promote SiC particle incorporation in the deposite.(2) SiC particle incorporation doesn' t effect the crystallization of the composite coating, the wear resistance, anti-oxidation and anti-corrosion propreties of the coating increase significantly after heat treatment in the temperature range of 200℃-400℃ for 2 hours. But the properties of the coating change with the NisSi phase forming when heated at 500℃ for 2 hours.(3 ) The wear resistance of Ni-SiC composite coating is much better than that of Cr coating and pure Ni coating with the heat treatment. The volume wear rate of Ni-SiC composite coating is only 31% of that of Cr coating, 11.6% of that of pure Ni coating. Therefore the Ni-SiC composite coating can be used to replace Cr coating for protecting the engine cylinder of the airplane.