钴基高温合金的水导激光制孔工艺研究 (特邀)

Objective Cobalt-based superalloys, renowned for their excellent high-temperature strength and oxidation resistance, are ideal materials for manufacturing critical components such as flame tubes in advanced aircraft engines. However, their exceptional high-temperature strength and sensitivity to work hardening pose significant challenges in machining film cooling holes. This study aims to explore the water-guided laser machining of GH5188 cobalt-based superalloy, focusing on the impact of key process parameters on the geometry and morphology of micro-holes, and determining the optimal parameters for fabricating high-quality micro-holes in this material. Methods The GH5188 specimens were characterized by SEM and X-ray diffraction (Fig.1-Fig.2), and their key physical properties are listed in Tab.1. A water-guided laser machining platform was built, with the system schematic and main equipment parameters shown in Fig.3 and Tab.2, respectively. A series of systematic experiments were then conducted to assess the influence of key process parameters -including single pulse energy, repetition frequency, water jet pressure, and scanning speed -on the geometric dimensions and morphology of the micro-holes. Additionally, orthogonal experiments were conducted to evaluate the relative contributions of each process parameter to the micro-holes size and morphology. The optimal parameter combination was identified and successfully applied to fabricate micro-holes with good morphological quality. Results and Discussions The micro-holes drilling results under different single pulse energies, repetition frequencies, water-jet pressures, and scanning speeds are presented in Fig.4-Fig.7, respectively. Orthogonal experiments were performed to evaluate the effect weight and interaction tendency of each parameter, with the orthogonal test results and main effects plot shown in Fig.8-Fig.9. The experimental results indicate that single pulse energy and repetition frequency are the most significant parameters affecting the entrance and exit diameter deviations, as well as the taper of the micro-holes. Using the optimized parameters, high-quality micro-holes with a near-zero taper of 0.00052 were successfully fabricated in GH5188 material, the entrance and exit surface morphology and sidewall morphology with element variation are shown in Fig.10-Fig.11. Respectively, demonstrating improved edge integrity and minimized thermal damage without obvious recast layer or slag accumulation. Conclusions This study successfully identified the optimal process parameters for water-guided laser machining of taper-free micro-holes in GH5188 cobalt-based superalloy: single pulse energy of 8.0 mJ, laser repetition frequency of 8.5 kHz, water jet pressure of 20.0 MPa, and scanning speed of 7.5 mm/s. The fabricated micro-holes exhibited excellent geometry and morphology, confirming the reliability of the optimized parameters. This research provides a solid foundation for selecting and optimizing the process parameters for precise laser machining of cobalt-based superalloys.