Enhancing micro-hole quality for SiC_f/SiC CMCs via coupled laser ablation and ultrasonic vibration

Silicon carbide fiber-reinforced silicon carbide ceramic matrix composites (SiC_f/SiC CMCs) are promising materials for high-temperature components due to their exceptional thermal-mechanical and physical properties. Film cooling technology, utilizing numerous micro-holes (0.1–1 mm in diameter), is a critical approach for enhancing the material's thermal resistance. However, the inherent hardness, brittleness, and anisotropy of SiC_f/SiC CMCs pose significant challenges, leading to low precision and poor efficiency in micro-hole fabrication. To address these challenges, this study proposes a hybrid micro-hole drilling method combining laser ablation and ultrasonic vibration-assisted drilling (LA-UVAD). Through comparative experiments, the material removal mechanisms and damage formation patterns under the synergistic effects of laser ablation and ultrasonic vibration were investigated. The effects of various drilling parameters on drilling force, hole-wall quality, geometric accuracy, and exit damage were systematically analyzed. A multi-objective optimization model based on machine learning and the nondominated sorting genetic algorithm II (ML-NSGA-II) was developed and experimentally validated. The results show that all indicators initially decrease and then stabilize as spindle speed increases and feed rate decreases. Compared to conventional empirical methods, the LA-UVAD process reduces drilling force, hole wall roughness, and exit damage by 7.23%, 10.04%, and 52.47%, respectively, with a prediction error of less than 18% for the optimization model. These results provide a solid theoretical foundation and offer valuable practical insights for the efficient, low-damage machining of micro-holes in SiC_f/SiC CMCs.