Investigation of the Damage Mechanism of Femtosecond Laser Processing of Diamond/SiC Composites Based on DFT

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Abstract
Aiming at the problems of high hardness, high brittleness, and severe damage caused by traditional processing technologies of Diamond/Silicon Carbide (Diamond/SiC) composites, this paper systematically studies the effects of different powers and processing technologies of femtosecond laser on the material properties. The composite material was processed using six laser powers under two processes: cutting (depth-concentrated energy input) and grinding (surface-dispersed energy input). Combined with characterization methods such as XRD, SEM, XPS, and AFM, the influence laws of laser power on the phase composition, graphitization degree, surface morphology, and roughness of the material were systematically analyzed. Additionally, density functional theory (DFT) calculations was used to reveal the influence mechanism of laser power on the structural stability of the material from the perspectives of thermodynamics and phonon properties. The results show that: due to concentrated energy input, the cutting process is prone to thermal accumulation, leading to a high degree of diamond graphitization and severe surface defects. The roughness is the lowest at a power of 2700 W, reaching 80. 6 nm. The grinding process, with dispersed energy input, can weaken thermal accumulation and reduce the degree of diamond graphitization under the same laser power. The roughness is the lowest at a power of 3000 W, which is 71. 3 nm. Density functional theory calculationsconfirms that the thermal damage of Diamond/SiC composites is essentially the synergistic effect of hindered heat conduction caused by interfacial phonon scattering and laser energy-induced temperature exceeding the critical threshold. The intrinsic structure of the material is stable. Under laser irradiation with power higher than 3100 W, the temperature exceeds the critical graphitization temperature of diamond, ultimately leading to severe damage.

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