The effect of laser microstructuring on the structure and properties of the surface layer of U8A Carbon steel parts

The purpose of the work was to study the effect of laser microstructuring on changes in the microhardness and structure of the laser exposure zone of U8A high-carbon steel sheets.Methods. High-carbon steel sheet U8A grade (sheet thickness 10 mm) was selected as the objects of the study, from which samples for the study were cut using a continuous fiber laser equipped with an EIP1119 optical head manufactured by NTO IRE-Polyus. After gas laser cutting, laser microstructuring of the rolled Q-switch surface was performed using a fiber pulsed laser according to the following mode: speed 40 mm/s; power 100 Watts; frequency 100 kHz, pulse duration 100 ns, pulse energy 1MJ. To study the microstructure, slits were made, followed by etching the surface with a 5% HNO3 solution in alcohol. The microstructure was studied using a Nikon MA200 inverted metallographic microscope at different magnifications. The following equipment was used to measure the macrohardness: Rockwell TP150M hardness meters (scales HRC, HRB and HRA), Super-Rockwell TRS 5009-01M (scale HRN15 – at a load of 15 kgf). Microhardness was measured on a KBW1-V hardness tester under loads: 10 N, 1 N and 0.25 N.Results. It was found that laser treatment of the surface of the samples led to an approximately two-fold increase in the hardness of the surface layer with a depth of 0.029-0.045 mm. It is revealed that the increase in hardness occurs due to a change in the structure of the surface layer of the samples as a result of an increase in the dispersion of granular perlite. It is shown that during laser exposure, the surface of the samples is heated and further cooled in air after laser removal, which corresponds to classical heat treatment – normalization. The obtained hardness values correspond to the troostite structure.Conclusion. The results obtained can be used in the creation of resource-saving material processing processes.