Currently, the development of mechanical engineering depends on the development of effective technologies that can improve the reliability of both machines and technological equipment. To increase the wear resistance of machine parts, it is first of all necessary to improve their performance indicators, namely, to change the microstructure and increase the hardness of the surface layer.
The Russian Federation provides a large number of production areas that currently are at the stage of improvement and contribute to the economic development of the country. The area of the manufacture of mechanisms with gears became very popular in production and repair areas.
The technology of manufacturing gears consists of mechanical and heat treatment (HT). Traditional methods of heat treatment, such as bulk hardening in furnaces, chemical heat treatment (CHT), high-frequency current (HFC) hardening, and laser hardening, are environmentally unsafe and harmful. Thermal microcracks and their subsequent development, decarburization and oxidation of the surface layer, uneven cross-section hardness, and difficulties in finishing with honing and grinding are also possible [6].
Bulk hardening in furnaces allows obtaining only overall strength when hardening and serrated profiles are needed. HFC hardening leads to brittleness and warping of the teeth, especially with a small module. CHT method has restrictions on the weight and size of the gears and allows getting a small thickness of the hardened layer of the part compared to other types of HT. CHT is long and expensive; it is mainly used in large-scale and mass production.
Diffusion processes do not always occur in the metal during laser quenching, as a result of which the structure remains uneven, which negatively affects the strength and hardness indicators. Therefore, the workpieces are subjected to preliminary heat treatment in order to obtain a more uniform and dispersed structure. At the same time, laser hardening results in structural heredity: the structure of the previously hardened steel is restored and the subsequent re-hardening occurs under the influence of laser radiation. It follows that to obtain the best mechanical properties of hardened steel, it is desirable to carry out a preliminary heat treatment to recover the structure, as well as that laser hardening technology allows strengthening the gears module preferably from 5 mm [7].