Surface features of multi-beam coupling nanosecond laser processing of nickel-based superalloys

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Abstract
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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