Femtosecond laser drilling of SiC/SiC composites in longitudinal magnetic field and semi-water immersion assistance

The thermal protection components prepared by SiC/SiC composites require laser processing of a large number of high-quality cooling holes. Improving the quality of femtosecond laser drilling for SiC/SiC composites using field-assisted techniques is an unexplored area. This study aims to bridge this research gap by evaluating and comparing femtosecond laser drilling performance in SiC/SiC composites under varied environments (unassisted, magnetic-assisted, water-assisted, and water/magnetic-assisted). The investigation delves into the effects of magnetic and water assistance on hole geometric properties, elucidating processing mechanisms. In addition, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) were used to analyze microscopic characteristics. The results show that water-assisted increases the hole diameter more significantly compared to magnetic-assisted. It is worth noting that water-assisted improves the roundness of the entrance and exit, while magnetic-assisted affects the roundness of the entrance. Water-assisted oxidation inhibition and water flow-promoted debris removal effectively mitigated oxide deposition and diffusion, resulting in improved morphology of the entrance/exit and cross-section. Importantly, water/magnetic-assisted drilling significantly improved the hole wall morphology and reduced the surface roughness by 93.3%. EDS and XPS analyses showed that magnetic-assisted and water-assisted inhibited oxidation in the deposition and diffusion zones at the entrance, while magnetic-assisted performed better in inhibiting oxidation in the diffusion zone. Water/magnetic-assisted drilling is an effective method to improve the quality of femtosecond laser drilling of SiC/SiC composites. This study provides new insight for future high-quality drilling of ceramic matrix reinforced composites.