Structural Features of Steel 35 after Quenching by Deforming Cutting
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Structural Features of Steel 35 after Quenching by Deforming Cutting A. G. Degtyarevaa, O. M. Zhigalinaa,b,*, D. N. Khmeleninb, and V. N. Simonova a Bauman
b
Moscow State Technical University, Moscow, 105005 Russia Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics,” Russian Academy of Sciences, Moscow, 119333 Russia *e-mail: [email protected] Received March 20, 2018; revised March 20, 2018; accepted April 12, 2018
Abstract—The structure of steel 35 after high-speed quenching by deforming cutting has been investigated. The phase composition and structural features of the hardened surface layer, consisting of regions (edges) with a similar periodic inhomogeneity, are established. A martensite-like structure of different degree of dispersivity (1–3 μm) is found to be localized in the vicinity of the cutter. A ferrite structure with a grain size of 1.0–1.5 μm dominates in the zone located far from the cutter effect. The revealed periodic structural inhomogeneity is due to the nonuniform temperature distribution during deforming cutting. Partial dissolution and a change in the shape and sizes of cementite plates in the α-Fe matrix as a result of plastic deformation are revealed by electron microscopy. DOI: 10.1134/S106377451806010X
INTRODUCTION High-speed impacts with concentrated energy fluxes (laser irradiation, plasma quenching, electronbeam and ultrasonic treatment), which change the properties of the surface layer of materials, are characterized by a variety of structural processes. High-speed treatments aimed at surface hardening (as a result of which, along with an intense thermal effect, the surface layer is subjected to plastic deformation) hold a particular position among the aforementioned impacts. Such treatments include, for example, electromechanical and friction-hardening quenching by grinding and special turning. Despite the technological differences, a common feature of all these methods is that a treatment intensively affects local regions in material, which leads to the formation of peculiar structures, radically differing from the well-known ones (obtained by conventional thermal treatment). The specificity of thermal effect at high-speed treatments of materials leads to a change in the phase transformation temperature. For example, the α-Fe– γ-Fe transformation in steels may be shifted to higher temperatures [1, 2], while the transformation temperature range may be expanded with an increase in heating rate [3, 4]. Extreme temperature and time conditions may change the phase transformation mechanisms and the structure formation kinetics during crystallization. For example, high-speed heating makes it possible to implement (at least, partially) diffusionless shear mechanism of austenite formation [5]. The results obtained by many researchers indicate that an increase in the heating rate leads to an increase
in dispersivity of material structures [6–10] and changes significantly the recrystallization mechanism and rate. It
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