Effect of Substrate Surface Texture Shapes on the Adhesion of Plasma-Sprayed Ni-Based Coatings

The bonding of thermal-sprayed coatings largely depends on the substrate surface morphology. This study examines the effect of the substrate surface texture shapes on the adhesion strength of coatings. For that, it used plasma-sprayed Ni-based MoS2 coatings deposited on grit-blasted and laser-textured surfaces, and investigated the coating bonding strength (ASTM 633 pull-off test), and cross-sectional and fracture morphologies, as well as phase compositions and element distribution. The results showed that the surface texture shape has a significant effect on the improvement of coating adhesion. The coatings deposited on sinusoidal-textured surfaces had the highest adhesion strength (50.0 MPa), followed by coatings deposited on groove-textured surfaces, while dimple and dimple–groove textures resulted in the lowest coating adhesion strength. The coating fracture analysis revealed that cohesive failure occurred mainly at the texture positions, while adhesive failure occurred almost always in plain areas. Therefore, it could be concluded that, in the conditions of this study, the existence of plain areas and dimple textures did not improve coating adhesion. Factors such as coating bond mode, contact area ratio, and coating deposition quality should be comprehensively considered in texture design to improve coating adhesion.