Mechanistic analysis of waterjet-guided laser effects on surface micro-defects in nickel-based superalloys

Aircraft engines, crucial to aerospace performance, depend heavily on the thermal and mechanical properties of turbine blade air film holes. These properties are notably influenced by micro-defects introduced during manufacturing. While waterjet guided laser (WJGL) processing offers distinct advantages due to its unique machining approach, the mechanism by which it affects micro-defects remains unclear. This study employed response surface methodology to investigate the effects of waterjet-guided laser (WJGL) processing parameters on the surface integrity and microdefects of nickel-based single-crystal superalloys. A mathematical model was developed to characterize the WJGL processing of these alloys, aiming to understand microstructural changes and guide the control of microdefects. The results show that heat input and spatial energy density significantly influence the surface integrity of the remelted layer, with higher heat input and energy density leading to increased surface defects and roughness. Interactions between processing parameters were also analyzed. At lower heat input and energy density, water pressure plays a critical role in reducing thermal defects, with higher pressure enhancing heat dissipation and mitigating thermal damage. At higher heat inputs, the waterjet predominantly acts as an erosive agent. A notable interaction was observed between water pressure and hole depth ratio, where droplet reflection within the hole disrupts the processing jet, reducing efficiency. Additionally, oxidation studies revealed that dissolved oxygen in water promotes reactions between internal elements and oxygen, forming oxides that adhere to the remelted layer and degrade the mechanical properties of gas-film holes. Controlling element segregation can minimize microcracks and oxide residues. These findings offer valuable quantitative insights for reducing thermal defects in high-performance turbine components during precision manufacturing.