Inconel 718 微槽/孔的水导激光填充扫描加工工艺 (特邀)

Objective With the increasing demands for service life and performance of aero-engines, the machining quality and efficiency of film cooling holes in hot-section components, primarily fabricated from nickel-based superalloys, are facing new challenges. Currently, conventional processing methods for film cooling holes in nickel-based superalloys exhibit certain limitations. Specifically, electrical discharge machining induces significant thermal effects, making it difficult to avoid the formation of recast layers and microcracks; electrolyte jet machining suffers from electrolyte corrosion damage at hole edges; and ultrafast laser processing, despite producing high-quality holes, suffers from relatively low processing efficiency. In contrast, water-jet guided laser machining technology offers distinctive advantages, including minimal surface damage, high precision, reduced recast layer formation, and independence of processing distance from laser focal depth, thereby demonstrating considerable potential for meeting the processing requirements of film cooling holes. To improve the sidewall morphology of nickel-based superalloys processed by water-jet guided laser scanning, this study investigates the influence of scanning parameters on processing quality and obtains an optimal parameter combination that simultaneously ensures both processing efficiency and sidewall quality. These findings provide valuable references for subsequent research on water-jet guided laser processing of nickel-based superalloys. Methods Firstly, this study investigates the influence of laser power and scan times on the process characteristics of nickel-based superalloys during water-jet guided laser non-filled scanning of straight grooves. Subsequently, the effect of fill spacing on the machining quality of water-jet guided laser filled scanning is examined. Finally, optimal parameter combinations are selected for the fabrication of straight holes and 45° inclined holes to conduct process validation. Post-processing involves grinding and polishing of the machined specimens using a polishing machine, followed by ultrasonic cleaning in anhydrous ethanol solution. The morphologies of the grooves and holes are then characterized using a tungsten filament scanning electron microscope (SEM). Additionally, energy dispersive spectroscopy (EDS) analysis is performed on the straight grooves obtained from scanning processing to evaluate the degree of oxidation at the groove entrances. Results and Discussions In water-jet guided laser scanning processing, as the laser power increases from 20 W to 50 W, the depth and width of groove exhibit a gradual increase (Fig.3); however, the sidewall quality of the surface of groove deteriorates, and the degree of oxidation near the entrance of groove becomes more severe (Fig.4). When the scan times increases from 1 to 4, the depth and width of groove gradually increase (Fig.3), whereas surface ablation becomes increasingly pronounced and the oxygen content rises progressively (Fig.4). In filled scanning processing, a fill spacing of 10 μm yields grooves with optimal entrance linearity and the lowest degree of oxidation, compared to fill spacings of 5 μm, 15 μm, and 20 μm (Fig.5). In inclined filled scanning processing, comprehensive evaluation of groove entrance linearity and entrance spatter indicates that a fill spacing of 10 μm achieves the highest groove quality (Fig.6). The morphologies of inclined groove entrances processed by left-to-right and right-to-left filled scanning are essentially identical (Fig.7). Under the optimal parameter combination of 50 W laser power and 10 μm fill spacing, both straight holes (Fig.8) and 45° inclined holes (Fig.9) exhibit satisfactory quality at entry/exit and cross-sectional sidewalls. Conclusions This study investigates the influence of water-jet guided laser scanning parameters on processing quality and obtains an optimal parameter combination that simultaneously ensures both processing efficiency and sidewall quality. Experimental results demonstrate that higher laser power leads to increased processing efficiency but compromises sidewall quality. Within the selected parameter range, an increased scan times enhances material removal capability yet deteriorates sidewall quality. Appropriate selection of fill spacing in water-jet guided laser filled scanning enables the attainment of favorable sidewall quality while maintaining high processing efficiency through high laser power. Within the experimental parameter range, the optimal fill spacing for water-jet guided laser filled scanning at 50 W laser power is determined to be 10 μm. In inclined filled scanning, variations in fill scanning direction within the same groove exert negligible influence on processing outcomes. Under the optimal parameter combination of 50 W laser power and 10 μm fill spacing, both straight holes and 45° inclined holes exhibit excellent sidewall quality. These findings indicate that appropriate fill spacing selection facilitates the achievement of superior film cooling hole sidewall quality while ensuring processing efficiency through high laser power application.