Dependence of the resistance mechanism to corrosion on the artificially modified microstructures of APS Y2O3 coatings by response surface method

This work employed a response surface method (RSM) to artificially design the atmospheric plasma spraying (APS) parameters to prepare yttrium oxide (Y 2 O 3 ) coatings on nickel aluminum bronze (NAB) alloys to improve corrosion resistance in marine environments. The resistance mechanism was comprehensively explored based on the correlations among parameters, microstructure, and corrosion behaviors. Results indicated that the optimized parameters (current of 621.21 A, Ar flow of 49.04 L/min, spray distance of 132.73 mm) fostered modified microstructures with coherent grain boundaries and reduced porosity to 3.65%, extensively diminishing corrosion paths. The refined grain size lengthened the penetration path of corrosion ions, while the reduced scale of defects accelerated passivation, functioning in a "passivation-assisted blocking effect" capacity. Consequently, the optimized coating conferred a corrosion current density of 1.51 μA/cm 2 —one order of magnitude lower than bare alloy. The RSM-designed Y 2 O 3 coating successfully establishes a superior protection system for NAB alloys, ensuring enhanced durability in harsh working environments.