Research of thermomechanical processes in the surface layer of steel parts after strengthening electromechanical processing

This article presents the results of theoretical and experimental studies of the surface layers of parts made of structural steels after electromechanical hardening.

The authors show that electromechanical hardening is characterized by the simultaneous presence of heterogeneous structures, non-uniformly distributed in the surface layer of the part, formed by varying intensities of thermomechanical action. The extremely short thermal exposure time of the surface layer during electromechanical hardening does not facilitate complete dissolution of cementite and the formation of a homogeneous γ-solution, which can lead to incomplete hardening with cementite inclusions. During electromechanical hardening, due to high-speed heating and cooling, a fine-grained martensitic structure is formed in a thin surface layer, as well as the thinnest non-etchable (by conventional methods) light zone with a depth of up to 0.1 mm. The light zone and the base metal have a distinct boundary, indicating a significant difference in the nature of these structures.

Therefore, the research proves that significantly lower internal residual stresses present in the treated surface layer after surface electromechanical processing, which is confirmed experimentally. In this case, stresses of the first kind were considered in the study. Moreover, individual micro-volumes of the surface layer of local tracks can be tempered and contribute to obtain a heterogeneous structure in the treated layer.

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