Achieving a synergistic combination of high hardness, enhanced creep resistance and damage tolerance in plasma-sprayed eutectic/amorphous Al₂O₃-YAG composite coatings through laser remelting

Abstract

Atmospheric plasma-sprayed (APS) Al₂O₃-YAG amorphous coatings show potential for corrosion protection in third-generation Concentrated Solar Power (Gen3 CSP) systems but suffer from inherent porosity, microcracks, and high-temperature structural instability. To overcome these limitations, this study utilizes a laser remelting (LR) post-treatment strategy to transform the amorphous precursor into a dense, layered eutectic/amorphous composite structure. This unique architecture achieves a synergistic combination of high hardness, superior creep resistance, and damage tolerance. The remelted surface layer exhibits a peak hardness of 23.46 GPa (approximately 2.7 times that of the amorphous base) and a reduction in steady-state creep rate by nearly 65%. Mechanistically, the in-situ formed fine eutectic network acts as a barrier to dislocation motion and diffusion, significantly enhancing creep resistance. Furthermore, the dense phase boundaries promote toughening mechanisms such as crack deflection and bridging, replacing the catastrophic shear band failure of the amorphous phase with a controlled energy dissipation mode. These results demonstrate that laser-remelted Al₂O₃-YAG coatings offer a robust solution for ensuring long-term structural integrity and reliability in extreme molten salt environments.