Tula State University (Tula, Russia):

L. M. Nechaev, Cand. Phys.-Math., Prof., Dept. “Theoretical Mechanics”, e-mail: nech47@yandex.ru
N. B. Fomicheva, Cand. Eng., Associate Prof., Dept. “Metal Physics and Material Science”
E. V. Markova, Cand. Eng., Associate Prof., Dept. “Machinebuilding Technology”

The results of metallographic researches and the study of wear resistance of 30KhN2MFA and 30KhGSA structural steels after hardening by such technologies as shot blasting, ultrasonic smoothing, laser processing, and electrochemical polishing have been presented. The evaluation of the tribotechnical properties of the hardened layers obtained by the investigated surface-hardening technologies have been carried out. The main criteria were the depth and type of substructural loosening of the active rubbing layer. An increase in the wear resistance of the material after the laser surface treatment was obtained. The paper presents the results of the calculation of the most important characteristics of the surface layer substructure: the level of microdeformations (Δа/а), dislocation density ρ, the size of the block structure fragments D after applying the tested hardening methods. The energy intensity of the structures was determined, which made it possible to identify structures with the highest fatigue life. It was established that the pulsed laser effect contributes to a sharp increase in the density of dislocations and micro-distortions. At the same time, the volume of the austenitic phase and the level of tensile macrostresses increase. Carrying out additional ultrasonic smoothing enables to reduce the amount of residual austenite and changes the sign of macrostresses. The combination of a pulsed laser and ultrasonic treatment to the greatest extent strengthens the structural steels under study.

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