S. V. Belikov

Investigation of Special Misorientations in Lath Martensite of Low-Carbon Steel Using the Method of Orientation Microscopy

Special misorientations between the laths of martensite packets in a low-carbon structural steel have been investigated by the method of EBSD-based orientation microscopy. It has been established that, in the process of the γ → α transformation, as a consequence of Kurdjumov—Sachs orientation relationships (ORs), special misorientations of the Σ3, Σ11, Σ33c, and Σ99a types are formed between the laths of a packet. The Σ3 misorientation is exact, and the remaining misorientations close to the special ones are formed with identical angular deviations as a result of the need to match the misorientations of laths in triple junctions (Σ3 + Σ11 → Σ33c, Σ3 + + Σ33c → Σ99a). Triple junctions of laths also appear in the packet that include a low-angle boundary (LAB) (between two laths of one orientation) and two boundaries of the Σ33c type, which can lead to the appearance of a boundary of the Σ41c type (Σ33c + LAB → Σ41c). The misorientation that corresponds to the Σ25b boundary discovered in the structure probably appears between the laths as a consequence of the fulfillment of the Nishiyama ORs.

Corrosion resistance of nickel-based alloys in salt and metal melts containing REE

The corrosion resistance of Hastelloy G-35 and VDM® Alloy 625 nickel alloys was studied in a wide temperature range (750–1100 °C) in fused LiCl, CaCl2, NaCl–KCl, LiF mixtures containing REE. The rates and the mechanisms of the corrosion of the materials studied were determined. The processes taking place during the interaction between alloys and melts were investigated.

Separations in steels subjected to controlled rolling, followed by accelerated cooling

Zones on the fracture surfaces of Charpy specimens and profiles of the fractures of these specimens are examined using impact-bending tests carried out in the temperature range of +20 to–90°C and fractography. The specimens were cut out of hot-rolled plates produced from 05G2B super-low-carbon steels that contained Ti, Nb, V, and Cu microadditives using controlled rolling, followed by accelerated cooling. A detailed analysis of separations, including a study of the morphology, number, area of separations, and the surrounding stress-relaxation zones, and the structure of the walls, has allowed us to identify the mechanisms of the origination and growth of the separations. It has been found that the correlated changes in the length, width, and depth of the separations are accompanied by the formation and expansion of the stress-relaxation zones around the separations. The rate of expansion of the area of these zones is higher than that of the area of the separations, which favors the macroplastic fracture of the specimens.

High-temperature corrosion of metals in the salt and metallic melts containing rare earths

A complex of independent methods was employed to study the corrosion resistance of molybdenum, zirconium, tantalum and tungsten in chloride, chloride-fluoride and fluoride-oxide melts based on LiCl, CaCl2, NaCl– KCl, LiF, and containing rare earths. Tests were conducted for 30 h at 750–1050 °C. The metals showed excellent corrosion resistance in fused chlorides (the corrosion rates were below 0.0005 g/(m2 h). Despite the presence of chemically active fluoride ions in the chloride-fluoride melts, the metals studied also showed very low corrosion rates, except molybdenum, for which the rate of corrosion was 0,8 g/(m2 h). The corrosion resistance of tantalum was considerably reduced in the fluoride-oxide melts; the corrosion rate was over 1 g/(m2 h) corresponding to the 8-th grade of stability and placing tantalum to the group of “low stability” materials.

A STUDY OF THE EFFECT OF TEMPERATURE MODES OF MELTING ON THE SPECIAL FEATURES OF STRUCTURAL AND PHASE TRANSFORMATIONS IN CORROSION-RESISTANT ALLOY ÉK77 UNDER ANNEALING AND AGING

The effect of preparation of alloy ÉK77 in liquid condition before crystallization on the characteristics of its cast, homogenized and aged structure is studied. The liquidus and solidus temperatures of alloy ÉK77 are determined. The temperature-time treatment of the melt is shown to influence the special features of the phase and structural state of alloy ÉK77 under post-crystallization heat treatment.

Special Features of Formation of Excess Phases During Aging of Corrosion-Resistant High-Alloy Austenitic Alloys Based on Fe And Ni

The applicability of the active criteria for estimating the metastability of austenite for predicting the operating capacity of high-alloy corrosion-resistant alloys based on iron and nickel in a single-phase preliminarily quenched condition in a temperature range of up to 500 – 650°C is analyzed. The temperature and time ranges of formation of excess phases are determined and fragments of C-curves are plotted. The effect of preliminary cold plastic deformation on the kinetics of aging and on the morphology of segregation of particles of second phases is studied.

Features of Carbide Precipitation During Tempering of 15H2NMFA and 26HN3M2FA Steels

Thermodynamic calculation of the equilibrium phase composition and evolution of the size and composition of carbide particles was carried out using Thermo-Calc and TC-Prisma 2.0 in order to identify the optimal modes of the final heat treatment for 15H2NMFA and 26HN3M2FA steels. The formation of structure and mechanical properties complex of the investigated steels was experimentally studied after tempering. The model describing the precipitation and growth of carbide particles was suggested based on the experimental results. This model will be used as part of the developed control complex of thermodynamic and kinetic conditions for the formation of micro grains and nano-sized hardening phases.

Erratum to: “Separations in steels subjected to controlled rolling, followed by accelerated cooling”

V. M. Farbera, V. A. Khotinova, *, S. V. Belikova, O. V. Selivanovaa, N. V. Lezhninb, A. N. Morozovaa, M. S. Karabanalova, and A. Yu. Zhilyakova aUral Federal University, ul. Mira 19, Ekaterinburg, 620002 Russia bInstitute of Metal Physics, Ural Branch, Russian Academy of Sciences, ul. S. Kovalevskoi 18, Ekaterinburg, 620990 Russia *e-mail: khotinov@yandex.ru Submitted November 24, 2016; accepted for publication November 24 , 2016

Special Features of Structure Formation in Pipes from Medium-Carbon Low-Alloy Steel 32G2F Under Heat Treatment

Special features of formation of structure and properties of seamless pipes from medium-carbon low-alloy steel for oil and gas applications are considered and associated with chemical inhomogeneity of the metal of the pipes.

Phase Composition Influence on Melt Viscosity and Ingot Structure Formation Features in EK77 Alloy

Effect of the alloy initial structure before remelting on the melt viscosity, its state prior to crystallization, and on processes occurring in the alloy in solid state during its subsequent treatment was investigated using EK77 alloy. The study was performed by means of torsional oscillation of the melt with crucible, scanning electron microscopy, and optical metallography.