Study On The Preparation And Properties Of Composite Ceramic Coating On AZ31B Alloy By Thermal Spraying

Spraying composite powder was prepared by mechanical grinding method and agglomeration method.Using common spraying method,SHS reaction spraying method and thermal chemical reaction spraying method, common spraying ceramic coating,SHS reaction spraying ceramic coating and thermo-chemical reaction spraying ceramic coating were produced on magnesium alloy AZ31B.XRD and SEM were used to analyze the composition and morphology of the composite powder and composite ceramic coating. The thermal shock, compactness, microhardness, wear properties and corrosion resistance of the composite ceramic coating were investigated.The melting rate of SHS reaction spraying ceramic coating and thermo-chemical reaction spraying ceramic coating was high and the combination of the coating and matrix was well. Mg element took place diffusion in the interface of composite coating.TiB₂,MgAl₂O₄ and so on were found in the SHS reaction spraying ceramic coating.Thermo-chemical reaction was carried out in the process of preparing coatings. Al_3.21Si_0.47, MgAl₂O₄, Mg_3.5Al₉Si_1.5O₂₀ and so on were found in the coating.The thermal-shock times of these two kind of ceramic coating was 47 and 37, the porosity was 0% after hole sealing with varnish, the maxima microhardness value reached 1224 HV0.1 and 1016HV0.1.Wear properties and corrosion resistance of these two kind of ceramic coating was far higher than magnesium alloy substrate. The thermal shock, compactness, microhardness,wear properties and corrosion resistance of these two kind of ceramic coating was significantly better than common spraying coating.Compare with mechanical grinding method and agglomeration method,thermite reaction had happened in composite powder after 12 hours ball milling and globular structure coated each other was formed after granulation with agglomeration method.The spraying composite powder reacted fully in spraying process and high quality ceramic coating was formed by agglomeration method. The more new phase was produced in ceramic coating and the thermal shock, compactness, wear properties and corrosion resistance was significantly better than the ceramic coating with mechanical grinding method.