Character and mechanism of surface micromachining for C/SiC composites by ultrashort plus laser

Abstract

A new surface micromachining way of ultrashort plus laser for C/SiC composites with high quality and efficiency was demonstrated, including picosecond and femtosecond laser. Surface morphologies, element content and bonding states of C/SiC composites were analysed in detail after machined by picosecond and femtosecond laser power respectively. For femtosecond laser machining, the amount of nanoparticles increased with increasing laser power. At 20 and 50 mW, Si-C, C-C and Si-O bonds existed in nanoparticles, while Si-C bonds disappeared at 70 mW. For picosecond laser machining, cauliflower-like particles and periodic ripple with certain depth were formed distinctly. Furthermore, thermal ablation phenomenon occurred, and only Si-O bonds existed in particles due to the oxidation of the carbon fibres and SiC matrix. The results showed that femtosecond laser with low power was more suitable to the surface machining due to better machining quality and less machining damage compared with high power picosecond laser.

Effect of Heat Treatment on Mechanical and Thermal Properties of SiC/SiC Composites With Three-Dimensional Carbon Network

“…First, the transfer channels increase the density of SCCS composites as mentioned in Section 3.1. Second, the introduction of pitch-based C fibers can fill the mass transfer channel so that avoiding the problem of the transfer channel shrinking and leaving large holes in the subsequent CVI process [25] . In addition, when the crack propagates between the layers and encounters the transfer channel in the Z direction, the main crack passes through the fiber, then the C fiber bundle are sheared, and the remaining cracks by-pass the transfer channel and continue to expand (Fig.…”

“…Besides, CVI method yields stoichiometric and crystalline β-SiC matrix with fine-grained microstructure, which are preferred for heat conduction. In our previous work, laser-assisted CVI (LA-CVI) method combining CVI with laser processing was used to establish a CVI mass transfer channel [21][22][23][24][25] . The mass transfer channel not only increased the density, but also strengthened the mechanical properties and thermal conductivity of C/SiC composites.…”

A Study on the Technical Method of Drilling Micro Holes on New CMC-SiC with Femtosecond Laser

“…CMC-SiC (silicon carbide ceramic matrix composites) are considered as another new strategic material after the carbon-carbon composite material(C/C) [1,2]. CMC-SiC with high thermal stability, low density, high specific strength, high specific modules, good oxidation resistance, good ablation resistance, long life working temperature up to 1650℃ and other excellent features make it possible to replace the current high-temperature alloys and refractory metal materials used in high-performance engines, and it can further improve the thermal efficiency of the engine.…”