Effects of Vacuum Laser Remelting Post-treatment on the Microstructures and TGO Growth Kinetics of HVAF-Sprayed NiCoCrAlHfYSi and NiCoCrAlTaY Coatings

This paper aims to further explore the potential performance of MCrAlY coatings with high-temperature oxidation and corrosion resistance. The NiCoCrAlHfYSi and NiCoCrAlTaY thermal spray powders were deposited by activated combustion high-velocity air fuel (AC-HVAF), and then, the deposited coatings were treated by vacuum laser remelting treatment. Additionally, the formation and propagation of microcracks were significantly suppressed at the interface between thermally grown oxides (TGO) and HVAF coatings. Additionally, the initial presence of the TGO layers of vacuum laser remelted specimens reached ranging from 0.5 to 1.0 μm. After isothermal oxidation for 200 h at 1050 °C, a pure, dense, continuous, and stable alumina layer was primarily formed onto the surface of LHVAF386 coating, while those of other types of deposited coatings usually contained some kinds of spinel oxides. The metallurgical bonding interfaces between the TGO and vacuum laser remelted coatings were adequately excellent; thus, the microcracks at these regions were not easily detected, whereas for other types of deposited coatings, the formation and propagation of microcracks usually occurred. Furthermore, for the vacuum laser remelted LHVAF386 coating, the growth rate of TGO and weight gain of the coatings was considerably lower than those of other deposited coatings, confirming the coatings might be much more stable after vaccum laser remelting treatment.