A study of laser machining combined with dynamic chemical etching in micro‐hole drilling of 2.5D SiC f /SiC composites

Abstract In this study, we used a novel method of laser machining combined with dynamic chemical liquid etching (LMDCE) to drill holes in 2.5D SiC f /SiC ceramic matrix composites (CMC‐SiC). A chemical solution that could quickly remove the recast layer without damaging the substrate was selected. Severe recast layer and microcrack defects were observed when laser machining was performed in the air. The surface of the material was highly carbonized due to the thermal effect of the laser. The effect of different defocus amounts and scanning speeds on the hole taper was studied. A lower scanning speed can ensure that a smaller taper is obtained by the microhole. The bore diameter of the holes processed with a defocusing amount of 0 or −1 mm is more uniform. The results show that with the assistance of a dynamic chemical solution, the fibers break neatly into needle‐like shapes, the thermal effect of the laser on the ceramic substrate is significantly weakened, the microhole shows good roundness, and there are no recast layers and oxides on the sample surface. In addition, microcracks are significantly reduced, and high‐quality microholes without a heat‐affected zone (HAZ) are machined. The method provides a new idea on how to eliminate machining defects and achieve higher‐quality micromachining for ceramic matrix composites.