Study of the microhardness ensuring the contact endurance of structural materials

The strength of the working surfaces of gears depends on the mechanical properties of the material and the quality of parts. We present the results of studying the strength of materials and working surfaces of a gear mechanism due to structural changes attributed to chemical and thermal treatment. The surface strength of the gears of gas turbine engines was studied. Nitrocementation and ion nitriding were used for chemical and thermal treatment of the contacting surfaces of steel samples under study (20Kh3MVF-Sh, 16Kh3NVFMB-Sh, 18Kh2H4MA, and 12Kh2H4A). Changes in the microhardness of the component layers (diffusion, transition and basic) of the toothed crown were analyzed. Metallographic analysis of the structure of materials was carried out to describe the factors determining the surface strength of working surfaces. Systematized data on the change in the microhardness of materials obtained experimentally in conditions of mass production are presented. Presented experimental results on changes in the mechanical properties of materials are based on data on the microhardness and structural state of the surface layers of the working profiles of gears. A comparative assessment of the surface strength of the studied samples during contact interaction was performed. The dependence of the surface strength on the multifactorial volumetric structure and structure formation of the material in the process of operation is determined. It is shown that the method of surface saturation forms the structure of a material with different mechanical properties accompanied with the formation of a transition zone having characteristic distinctive values of the hardness. The results obtained can be used in the design of gears, taking into account changes in the mechanical properties and structure of materials to ensure the necessary operational requirements.