Study of laser hardening processes of corrosion-resistant austenitic steels using chromium-nickel steel 12Kh18N10T (AISI 321) as an example

The aim of this work is to study the processes of laser hardening: laser hardening and laser peening of corrosion-resistant austenitic steels with the latest generation of lasers. The development of the laser industry and the lasers that generate ultrashort pulses of radiation make a thin layer of a finely dispersed crystalline or sometimes an amorphous structure on the surface. The technology implies the use of nanosecond laser radiation with ultra-high power density. It is shown that significant hardening of the surface of 12Kh18N10T steel can be made with laser peening technology. It includes special preparation of the surface to excite a shock wave deep into the material. It also increases the hardness of materials that are not hardened by heat treatment. The methods of laser peening, depending on the material, includes the use of a layer opaque to laser radiation with a low evaporation temperature (black paint, metal foil, etc.) on the surface of the detail. A transparent layer is used upon the opaque layer. Water or water-based helium is most often used for it. The energy of the laser pulse is absorbed by an opaque layer. It leads to its heating, evaporation and the formation of a high-temperature plasma depending on the surface of the material and on the transparent layer that restrains the diffusion of plasma temperature. Comparative studies of laser hardening and laser peening of corrosion-resistant austenitic chromium steel were made in the article. Laser hardening can not provide a surface hardness of more than 300 HV. The increase in microhardness is connected with deformation processes in the melting area, that can be found in the scientific literature. The analysis of the results shows a significant hardening of the 12Kh18N10T steel surface due to the excitation of the laser impact wave. The impact wave made in the laser plasma creates conditions for intense plastic deformation; as a result an ultra-fine-grained structure with nanocrystalline grains are formed. The maximum microhardness of the 405 HV0.10 surface is made at a minimum thickness of the gel layer (0.1 mm).The work was supported by the Ministry of Science and Higher Education of the Russian Federation (project No. FSFS-2024-0024).