Synergistic Optimization of Plasma-Sprayed Zirconia Coatings: Towards Ultra-High Hardness and Superior Wear Resistance

This study reported on the multi-objective optimization of atmospheric plasma spraying parameters for zirconia coatings by incorporating the response surface method with the desirability method, while simultaneously enhancing microhardness and reducing wear rates. The spraying variables were optimized to improve coating performance using an L18 Taguchi orthogonal experimental design combined with the response surface method. The analysis of variance revealed the primary factors to be acceleration voltage, stand-off distance, powder feed rate, and primary gas Ar/H2; together, these factors accounted for 79.70% of the total performance variance. An R2 value of 0.752 for microhardness was yielded by the fitted reduced quadratic model, whereas an R2 value of 0.845 for wear volume losses was yielded by the interaction model. Within the optimised parameter range, the predicted microhardness was 1404.1 HV, with an experimental error of only 1.84%, and the wear volume loss was reduced to 4.53 mm3, with a prediction error of 3.27%. Additionally, the optimized coating was found to have fully molten droplets, less porosity, and negligible interlayer cracks, with only slight pitting observed during the wear test, as revealed by scanning electron microscopy. This multi-objective optimisation strategy, integrating the Taguchi method with the RSM, effectively enables the preparation of zirconia coatings with superior mechanical properties and provides reliable process guidelines for protective coatings on aluminium alloys.