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Abstract

On the basis of research and analysis of literature sources, it is shown that the surface plasma hardening is rational in terms of universality, availability and economic efficiency for prolongation of the service life of heavy loaded parts. Without changing the parameters of surface roughness, such a hardening heat treatment is easily integrated into the technological process of restoring parts, is the finish operation, low-cost, sufficiently productive, and allows to effectively increase the operational stability of the replacement parts of the working organs of agricultural machinery. Comparison of the results of the investigated five variants of thermal hardening of flat specimens made of 65G steel is based on the fact that the best combination of high strength, plastic and viscous properties for heavy-duty replaceable parts of the working organs of soil-cutting machines provides plasma hardening with tempering at 300 ° C. It has been confirmed that at ultrafast heating rates that occur during plasma quenching, phase transformations are shifted to high temperatures and this thermally activated process strongly influences the kinetics of nucleation and growth of new phase nuclei. The relationship between the rate of austenite nucleation and the rate of their growth varies; As the temperature rises, the process of austenite formation occurs faster than the acceleration of their growth, an increasing quantitative advance of the nucleation rate over the growth rate is observed. This leads to the formation of a fine-grained austenite, which turns into a highly disperse martensite with high strength characteristics.