Thermal Cycling Behavior of Selective Laser-Remelted Thermal Barrier Coatings with Different Laser Dot Distances

The two-layer structured YSZ/NiCrAlY coatings were modified with dot shape by laser remelting. The microstructure, phase composition and thermal cycling behaviors of the as-sprayed and laser-treated coatings with different laser dot distances were investigated. The thermal cycling behaviors of the as-sprayed and laser-treated coatings were studied systematically at 1000 °C. The results indicated that the coating with 3 mm distance between the laser-treated zone, namely the dot distance, showed the longest thermal cycling lifetimes, which was approximately 2.5 times as much as that of the as-sprayed coating. For one thing, the columnar grains and segmented cracks in the dot units were beneficial for accommodating the thermal stresses of coatings during thermal cycling. For another, a certain number of microcracks in the dot units could release the driving force for crack propagation, namely the elastic energy.