Laser-induced concave/convex micro-textures array for enhancing performance of surface coatings: Bond coating in thermal barrier coating system

The bond coat of thermal barrier coatings (TBCs) often experiences internal crack nucleation and propagation due to insufficient strain tolerance, leading to premature failure during service. To address this issue, a composite laser-induced texture composed of both concave and convex features is engraved on the bond coat to prolong the service life of the TBC system. The influence of laser parameters, including laser power and pulse width parameters, on the microstructure and mechanical properties of the modified bond coat is investigated. The microstructure and composition of the TBCs are characterized by laser scanning confocal microscope, scanning electron microscopy and X-ray diffraction. The microhardness, fracture toughness and wettability of the laser-textured and unengraved TBCs are evaluated. The results reveal that the surface texture transitions from a spherical crown to a volcano-shaped morphology as the laser pulse width increases. For different laser parameters, when the power and pulse width are 150 W and 2000 μs respectively, laser-induced volcano-shaped micro-texture array providing superior adhesive properties and a highly active coating, enhances surface solid-liquid wettability. Microscopic observations show that laser texturing effectively suppresses internal pores and cracks inside the coating, and refines grain structure. Furthermore, the mechanical properties of the NiCoCrAlY coating were altered following laser texturing. The hardness of the coating increased by 41.8 %, the elastic modulus decreased by 13.2 %, and the fracture toughness was improved.