Formation of A Hardened Surface Layer Under Complex Laser Action on the Cutting Edge of Parts Made of Structural Carbon Steels

Abstract

The purpose of the work was to study the effect of laser modification of the cutting edge on changes in the structure and mechanical properties of the surface layer of parts made of hot–rolled structural carbon steels of grades 20, 35, 45 using a fiber laser.Methods. Structural carbon steels of grades 20, 35, 45 were selected as the objects of the study. To study the effect of laser modification on changes in the structure and mechanical properties of machine parts using laser cutting, special samples were made in the form of plates with a thickness of 2 mm (st20 and st45) and 4 mm (st35). After gas laser cutting, laser modification of the Q-switch cutting edge was performed with a fiber pulsed laser.Results. The regularities of changes in the structure of the zone of gas-laser thermal exposure after laser treatment (cutting, modification) are revealed. It has been established that repeated laser treatment (laser modification) of the cutting edge does not lead to a change in the structural components and microhardness in the zone of gas-laser thermal effects obtained after laser cutting. It has been established that the nature of the microhardness change is the same for all the studied steel grades: the highest values are reached near the surface of gas-laser treatment and are, for example, for steel grade 35 470-560 HV, which is 3,2-3,9 times greater than the initial microhardness (145 HV). Thus, a hardened layer with increased wear resistance is formed on the surface of the part after laser treatment. It is shown that the use of laser surface modification as an additional operation in the manufacture of parts by laser cutting makes it possible to improve the quality (roughness) of the surface layer. At the same time, the greatest effect of reducing roughness is given by laser modification in three passes along the X-Y plane.Conclusion. The results obtained can be used in the creation of resource-saving material processing processes.