Spatio-temporal multi-scale observation of the evolution mechanism during millisecond laser ablation of SiCf/SiC

Millisecond laser processing has advantages in terms of depth, efficiency, and cost. The evolution mechanism of the laser ablation of SiCf/SiC fabricated through melt infiltration remains unclear. Therefore, spatio-temporal multi-scale observation is proposed. The information of gas, plasma, and droplets is collected and analysed. The results reveal that laser power and the type of assist gas considerably affect the material removal, hole morphology, and efficiency. Typical topographies, such as crack propagation, fibre fracture, recasting, and debonding are clarified with various melting temperatures and internal stress induced by temperature gradient. Additionally, the distribution of elements Si and C is exclusive, which is clarified with surface tension, melting temperature difference, chemical reaction, and intervention of assist gas. The simulation model based on heat transfer laws and the birth-death element method verifies the rationality of the evolutionary model of the hole morphology. Moreover, the simulation model established for first pulse ablation in N-2 indicates that a limited increase in maximum depth at high power can be attributed to the plasma shielding effect. This study can guide the processing of parts in the aerospace and nuclear industries.