Study On The Bonding Performance Of Plasma Sprayed Ceramic Coatings On Aluminum Alloys Substrate

Aluminum alloy is an optimum material for light weighting of vehicles, especially for automobiles. But, the low hardness and bad wear-resistance limited its application. Using plasma spraying technology to spray a hard coating on aluminum substrate can solve the shortages. Low bonding strength is a critical problem restricting its application of plasma spraying on aluminum. Bonding performance of plasma spraying Al₂O₃-45TiO₉ coating on aluminum substrate was researched from the respects of bonding mechanism and spraying processing.The principle of plasma spraying technology and its process were summarized. The influence of coatings structure, spraying parameters, heat transfer and movement of melt particles to the bonding strength was investigated. And the bonding mechanism was discussed.Orthogonal experiments were carried out on the spraying parameters of the process with NiCrAICo—Y₂O₃ bonding coatings and Al₂O₃-45TiO₂working coatings,which selected the primary influence factors and secondary influence factors. The optimized spraying processes for NiCrAICo — Y₂O₃ bonding coatings and Al₂O₃-45TiO₂ working coatings were determined.Al₂O₃-45TiO₂ coating was compared with WC-10Co4Cr coating. It showed that oxide ceramic coating was better than carbide coating as no burning loss of elements and no decomposition of compounds at high temperature. Considering the easy oxidation of aluminum at high temperature, it was designed to spray coating with the argon atmosphere to decrease the oxidation of aluminum substrate and reduce the forming of alumina on interface. Compared with the coating sprayed at atmosphere, the bonding strength of Al₂O₃-45TiO₂ coating sprayed at argon atmosphere was increased from 28.0MPa to 31.6MPa.Gradient and non-gradient of Al₂O₃-45TiO₂ coatings were designed and manufactured. The bonding strength was studied. The results showed that the gradient coating reduced the inner stress of coating and increased the bonding strength. The bonding strength of gradient coatings was high up to 37.4MPa. The chemical elementdistribution of the coating was measured with lining scan of the probe. The testing result was consistent with the design.The coatings were inspected by using equipment of metallurgical microscope, stereoscan and energy spectrometer, managing to find out the microstructure and the reason effecting on the bonding strength of Al-,O3-45TiO, coating on aluminum substrate.