Optimization of Plasma Spraying for VW75 Rare Earth Magnesium Alloy Based on Orthogonal Experiments and Research on Its Performances

Abstract

In this study, the effects of the six technological parameters of atmospheric plasma spraying (including spraying current, spraying distance, main gas flow, auxiliary gas flow, spraying speed, and powder feeding rate) on the microhardness, density, and rate of deposition of nanoparticle cluster-oxidized yttria partially stabilized zirconia (YSZ) powder-ceramic coating were investigated through an orthogonal experiment. The structures of the powder and coating were observed by a scanning electron microscope. The hardness measurements were carried out on the samples, and the cross-section experimental results were analyzed by combining the structure of the coating and range analysis method, thereby obtaining the optimized technological parameters. The results show that the coating was primarily composed of melted ZrO2, and the coating section was a characteristic of concave–convex occlusions. Mechanical bonding played the dominant role. Main gas flow was the primary influencing parameter of performances of the atmospheric plasma spraying ZrO2 coating, followed by spraying current, auxiliary gas flow, powder feed rate, spraying speed, and spraying distance, successively. The optimal technological parameters for atmospheric plasma spraying ZrO2 coating were 75 standard cubic foot per hour (SCFH) of main gas flow, 875 A of spraying current, 45 SCFH of auxiliary gas flow, 30 g/min of powder feed rate, 400 mm/s of spraying speed, and 85 mm of spraying distance. The bonding microhardness, density, and rate of deposition of the prepared coating were HV388, 5.25 g/cm3, and 31.58%, respectively. The electrode potential and corrosion resistance of the prepared coating increased remarkably compared with that of the substrate, whereas the corrosion current decreased significantly.