Laser ablation of RB-SiC composite by femtosecond laser irradiation

Abstract

Reaction-bonded silicon carbide composites (RB-SiC), consisting of SiC grains and Si matrix, have a complex ablation mechanism as two-phase composites under femtosecond laser irradiation. The ablation threshold of RB-SiC was calculated, which decreases (from 1.01 J/cm2 to 0.56 J/cm2) with increasing pulse number N and finally stabilized. At low fluence (F/Fth ≤ 5) and a low number of pulses, photochemical ablation dominates. For a higher number of pulses and high fluence (5 <F/Fth ≤ 50), photothermal ablation dominates with photochemical ablation. The results show that structures such as pits, convex, and holes exist on the surface of Crater I, while Laser-induced Periodic Surface Structures (LIPSS), and condensation structures exist on the surface of Crater II. In both types of ablation craters, the SiC grain surface produces the Low Spatial Frequency LIPSS (LSFL) with a period of about 900 nm and the High Spatial Frequency LIPSS (HSFL) with a period of about 300 nm. Based on the surface morphology, microstructure, and physical phase analysis of the ablation craters, a preliminary model of the removal mechanism of the ablation craters by femtosecond laser irradiation was established. These findings are expected to provide theoretical and experimental support for the precision processing of RB-SiC by femtosecond laser.