Silicon carbide fiber reinforced silicon carbide ceramic matrix composites (CMC-SiCf/SiC) have been widely used in aerospace and other fields due to their excellent properties such as high hardness, oxidation resistance and high temperature resistance. Different from the traditional machining methods, laser processing technology has great application prospects in CMC-SiCf/SiC. In this paper, the single-pulse ablation test and multi-pulse cumulative ablation test of CMC-SiCf/SiC were carried out by femtosecond laser at different powers with a wavelength of 1035 nm. A series of experiments were designed to process the ablation pits on the material surface. The diameter of the ablation pits was observed by laser confocal microscope. The variations of the ablation threshold of CMC-SiCf/SiC surface under different pulse energies and pulse numbers were studied. The results show that the multi-pulse ablation threshold of CMC-SiCf/SiC decreases with the increase of pulse number, and there is a significant cumulative effect. The multi-pulse ablation threshold of CMC-SiCf/SiC is mainly related to the number of pulses, which is determined by two parameters: accumulation factor and single-pulse ablation threshold. The single-pulse ablation threshold of CMC-SiCf/SiC is 1.1914 J/cm2, and the accumulation factor is 0.6245. In femtosecond laser processing, the pulse accumulation effect has a significant influence on the ablation of hard and brittle material CMC-SiCf/SiC. This study can provide technical guidance for process optimization.
Nickel-based superalloy (DZ411) is widely used in the manufacture of high-temperature components in the aerospace field due to its excellent physical and mechanical properties, such as high-temperature resistance, oxidation resistance, and corrosion resistance. Laser polishing can improve the surface quality and service performance of nickel-based superalloy materials. In this paper, a new type of multi-beam coupling laser based conventional laser is used to process the nickelbased superalloy materials. The processing experiments of nickel-based superalloy were carried out by changing laser power, scanning speed, and scanning pitch. Then the polished surfaces were observed and detected by laser confocal microscope. The results show that the surface of nickel-based superalloy materials has certain regularity with the variations of process parameters. Under these experimental parameters, surface roughness (Ra) decreases first and then increases with the increase of laser power, scanning speed, and scanning pitch. The minimum Ra of the polished surface is 1.06 μm under the process parameter combinations of laser power of 1W, scanning speed of 400 mm/s, and scanning pitch of 20 μm. The maximum valley depth (Rv) and the maximum height (Rz) of profile first decrease and then increase with the increase of laser power or scanning speed. However, Rv and Rz had a little rate of fluctuation with the increase of scanning pitch. The laser polishing process involves the dynamic time-varying absorption mechanism of the coupled laser energy by polymorphic materials, and it is accompanied by complex physical processes such as material melting, gasification, and re-condensation. When Ra is relatively low, a clear corrugated structure appears on the machined surface. This research work can provide process data support for optimizing the polishing process parameters of nickel-based superalloys and expand the laser processing types.
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