Effect of high-repetition frequency nanosecond laser remelting on microstructure and oxidation properties of low-pressure plasma sprayed NiCoCrAlYTa coating

MCrAlYX coatings are widely utilized as bond coat in thermal barrier coating systems. This study employs highrepetition frequency nanosecond laser remelting (HRF-NLR) to enhance the resistance to high-temperature oxidation of NiCoCrAlYTa coatings prepared via low-pressure plasma spraying (LPPS). The objective of this study is to investigate how laser remelting influences the microstructural evolution of the NiCoCrAlYTa coating and the growth characteristics of the thermally grown oxide (TGO). Various scanning speeds and laser pulse energy densities were employed to investigate the microstates of the molten pool and the polishing mechanisms of the samples after HRF-NLR. Increasing the repetition frequency effectively mitigates the ablation issues typically associated with conventional laser remelting, while also enabling precise control over depth of the remelted coating. Microstructure analysis shows that the original rough surface was remelted and polished, contributing to a significant reduction in surface roughness, noticeable grain refinement, a high density of dislocations, and the redistribution of active elements within the modified coating. Oxidation results at 1150 degrees C reveal that the HRR-NLR coating can induce the formation of a dense, continuous, and slow-growing single alpha-Al2O3 film, demonstrating that HRF-NLR is an efficient and feasible method for improving the resistance of MCrAlYX coatings to high-temperature oxidation.