Structure and Phase Composition of Ferriticperlitic Steel Surface after Electrolytic Plasma Quenching
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Russian Physics Journal, Vol. 63, No. 5, September, 2020 (Russian Original No. 5, May, 2020)
STRUCTURE AND PHASE COMPOSITION OF FERRITICPERLITIC STEEL SURFACE AFTER ELECTROLYTIC PLASMA QUENCHING N. A. Popova,1 E. L. Nikonenko,1,2 E. E. Tabieva,3 and G. K. Uazyrkhanova3
UDC 669.112.227.34
The paper presents the transmission electron microscopy investigations of the structure and phase composition of ferritic-perlitic ST2 steel surface after electrolytic plasma quenching. The steel in the initial state represents the material after hardening at 890°С for 2 or 2.5 hours and quenching in warm (30–60°С) water with subsequent tempering at 580°C for 2.5 or 3 hours. Electrolytic plasma quenching is carried out at 850–900°С in an aqueous salt solution for 4 seconds, at 320 V voltage and 40 A current. In the initial state, the morphology of the steel matrix consists of lamellar perlite and nonfragmented and fragmented ferrite. Electrolytic plasma quenching of the steel surface results in the martensite transformation, steel self-tempering, and the formation of cementite particles in all martensite crystals. This treatment also leads to the diffusion transformation of phases, the release of residual austenite (-phase) along the low-temperature martensite laths and lamellas and in all crystals of lamellar martensite, the formation of М23С6 special carbides and, finally, to the enhancement of all parameters of the steel fine structure. Keywords: steel, electrolytic plasma quenching, morphology, phase composition, ferrite, perlite, martensite, residual austenite, cementite, particle, fine structure parameters.
INTRODUCTION The effective development of industries is largely determined by the development and implementation of new resource-saving technologies that provide the quality improvement of products. Stable and efficient machinery production is impossible without the use of new technologies that provide the required complex of strength and plastic properties of constructional steels. This requires understanding of the nature of processes occurring in steels. The development of effective means of enhancing the service characteristics is based on studying the physical mechanisms of formation and evolution of the steel structure and phase composition as one of the important tasks of modern condensed-state physics and materials science. In many cases, the durability of mechanisms and machinery depends on the wear resistance of parts, which undergo considerable reversing impact loads. The surface layer of such parts must mainly possess the high strength and hardness that are combined with sufficient core viscosity. This can be achieved using a variety of the surface hardening techniques. One of such techniques is the surface quenching achieved through a short-duration heating of the metal surface layer up to a quenching temperature and its successive rapid cooling. Various surface quenching techniques are currently used in the industrial production [1–11]. Among them, electrolytic plasma quenching of parts [12–14], wh
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