APPLICATION OF COERCYTIMETRY METHOD FOR EVALUATION OF RESIDUAL STRESSES IN FLAT KNIVES

Abstract

With the help of high-frequency currents, hardening coatings of increased hardness are applied to the working bodies of agricultural machines. When evaluating the effectiveness of these methods, along with studying the basic physical and mechanical properties of coatings, it is necessary to know the level of residual stresses in the coatings obtained. (Research purpose) The research purpose is studying the features and evaluate the possibilities of using coercimetry as an objective and reliable method for determining the stress state of flat knives hardened by HDPE boration. (Materials and methods) Samples of 65G steel in the initial state and flat mower knives reinforced with HDPE boration were prepared for the study. Performed the work in accordance with the current GOST 58599-2019 "Technical diagnostics. Diagnostics of steel structures. Magnetic coercive method. General requirements". Bursting machines, a magnetic structroscope (coercitimeter) were used KRM-C-K2M and devices for determining hardness and microstructure. (Results and discussion) At the first stage, the expected values of the coercive force for 65G steel were calculated depending on the chemical composition. As a result of mechanical tests of 65G steel samples for tensile strength with simultaneous measurement of coercive force, experimental data were obtained for constructing calibration curves, which were used to determine stresses in hardened knife samples after HDPE boration. It was determined that the residual stresses in hardened flat knives vary from 400 to 730 megapascals. These stresses can be considered acceptable (safe), since the yield strength for 65G steel is 685-785 megapascals. (Conclusions) The method of measuring coercive force makes it possible to estimate the degree of change in residual stresses in parts hardened by HDPE boration methods.