Особенности формирования структуры в металлических сплавах при наноструктурирующей фрикционной обработке и последующем термическом воздействии

Цель настоящей работы – детальное электронно-микроскопическое изучение особенностей формирования структуры и фазового состава углеродистых и низколегированных сталей, а так же хромоникелевых сплавов (аустенитная сталь и лазерная наплавка) в процессе больших пластических деформаций при фрикционной обработке и последующем термическом воздействии. В соответствии с современными представлениями одним из важнейших резервов повышения прочности поверхности металлических материалов является создание в них высокодисперсных и нанокристаллических структур оптимизированного состава и уровня дефектности, которое может быть осуществлено современными методами интенсивной поверхностной пластической деформации (ИППД), такими как дробеструйная обработка, ультразвуковая ударная обработка колеблющимся инструментом, дробью или шариками в вакууме, обработка падающими или летящими из пневматической пушки шарами и другие методы. Нанокристаллические структуры (с размером кристаллитов 5-100 нм) могут быть также созданы под действием больших пластических деформаций, реализуемых в условиях внешнего трения (фрикционного воздействия) на поверхности не только пластичных металлических материалов, таких как медь, никель, кобальт, железо и аустенитные стали, но и высокопрочных материалов: аморфный сплав Fe64Co21B15, термоупрочненные (HRC более 62) углеродистые инструментальные, цементированные и высоколегированные стали. Поэтому эффективным методом наноструктурирования поверхностных слоев практически любых металлических материалов является фрикционная обработка, проводимая в условиях трения скольжения, исключающих заметный нагрев поверхности трения. Фрикционная обработка, позволяющая наноструктурировать в холодном состоянии высокопрочные и труднодеформируемые сплавы, расширяет возможности для углубленного исследования свойств наноструктур деформационного происхождения, которые не могут быть созданы другими методами получения объемных наноструктурных материалов. Важным преимуществом наноструктурирующей фрикционной обработки является ее применимость для дальнейшего улучшения свойств стальных изделий, подвергнутых поверхностной термической (например, лазерной) упрочняющей обработке, а также возможность кардинального повышения теплостойкости простых углеродистых сталей до уровня теплостойкости высоколегированных полутеплостойких сталей. Полученные в ходе исследования результаты могут быть использованы при разработке современных технологий создания наноматериалов функционального назначения с повышенными эксплуатационными характеристиками, обеспечивающими прогнозируемое повышение прочности, износостойкости и теплостойкости деталей и инструмента.According to the modern representations, surface layer modification is considered to be one of the most important reserves of increased durability and operational performance of metal materials. Considerable improvement in the tribological properties of metal materials can be achieved by the formation of a highly dispersed structural state in their bulk or surface layers using severe plastic deformation methods. For example, the rise of the wear resistance and the diminishing of the coefficient of friction of low-carbon steel are achieved by the nano-structuring of the surface layer with ultrasonic treatment using metal balls [Wang, Z.B., Tao, N.R., Li, S., Wang, W., Liu, G., Lu, J., and Lu, K., Effect of Surface Nanocrystallization on Friction and Wear Properties in Low Carbon Steel, Mater. Sci. Eng. A, 2003, vol. 352, nos. 1–2, pp. 144–149.]. Frictional treatment by indenters made of hard materials carried out under the sliding friction conditions that eliminate the severe heating of the surface being treated is an effective way to form functional nanocrystalline layers with enhanced strength and tribological characteristics on steel surfaces [Makarov, A.V., Nanostructuring Friction Treatment of Carbon and Low_Alloyed Steels, in Perspektivnye materialy. Tom IV: Uchebnoe posobie (Perspective Materials. Vol. 4: A Tutorial), Merson, D.L., Ed., Tolyatti: Tolyatti Gos. Univ., 2011, pp. 123–207.]. Unlike bulk deformation methods, frictional treatment makes it possible to form the nanostructure of not only soft and ductile, but also high strength and hardly deformed materials, including quenched steels. Nanocrystalline structure formation under frictional treatment sufficiently well covered for soft material like copper, pure iron and austenitic steels. However, in scientific periodic literature a consecutive process of nanostructures formation under the influence of a large plastic deformation in hardly deformed materials (like carbon steels, high alloyed steels and thermo-strengthened steels) was not considered so far. The aim of present research is to eliminate this deficiency. The study will clarify the modified surface layer structure and properties dependence on friction treatment and heat treatment parameters. Obtained data can be used in the development of modern functional-grade nanomaterials with the raised operational characteristics, providing predicted increase of durability, wear resistance and heat resistance of parts and the tools.Программа развития УрФУ на 2013 год (п.2.1.2.1

Effect of the technological conditions of frictional treatment on the structure, phase composition and hardening of metastable austenitic steel

The process parameters of the frictional treatment (indenter material, medium, load) of the 12Kh18N10T chromium-nickel austenitic steel have been optimized for the criteria of strain hardening and the quality of the surface being treated. The paper studies effect of the multiplicity of the frictional action of a synthetic diamond indenter at room temperature in an argon medium and the loading temperature ranging between -196°C and +250°C on the hardening, phase composition and fine structure of the surface layer of the steel. It has been found that the completeness of the strain-induced γ→α′ martensitic transformation in the surface layer of the steel is strongly dependent on the multiplicity and temperature of loading and that the level of hardening rises with the multiplicity of action, but shows little dependence on the temperature of frictional treatment. © 2016 Author(s).Russian Foundation for Basic Research, RFBR: 15-08-0794701201354598Ural Branch, Russian Academy of Sciences, UB RAS: 15-9-12-45The work was done in the framework of the Complex Program of UB RAS (project No. 15-9-12-45) and the government assignment for IES UB RAS, theme No. 01201354598 supported by RFBR, project No. 15-08-07947

Examining the structure of mill rolls made of 9X2MΦ and 8X3CΓΦ steels using the ultrasonic method for quality control

The microstructure of specimens of 9X2MΦ and 8X3CΓΦ steels taken from working rolls of a reversing mill was examined. A correlation between characteristics of the crystal structure of the metal and the intensified attenuation of ultrasonic waves was found. Ultrasonic inspection was carried out using an ultrasonic flaw detector (Krautkramer Co.). The microstructure was examined by means of traditional metallographic analysis methods, which were implemented using a scanning electron microscope; X-ray spectral microanalysis and electron backscatter diffraction were used. The morphology and elemental composition of discontinuity flaws were studied; as well, phase maps, crystallite misorientation histograms, and Taylor factor maps were plotted for specimens taken from the defect zone of a 9X2MΦ steel working roll. © 2013 Pleiades Publishing, Ltd

Parameters Evolution of Orthorhombic Martensite Lattice in VT16 Titanium Alloy During Heating

The material of the study was (α + β) -titanium alloy VT16. Samples were quenched from different temperatures and then they were heated in situ on X-ray diffractometer. It has been established that the period “b” of the orthorhombic martensite lattice showed negative values of the coefficient of thermal expansion during heating.     Keywords: titanium alloys, XRD-analysis, orthorhombic martensite, coefficient of thermal expansion

The Effect of Copper and Manganese on the Amorphization Process in a Thin Fe–Si–Mg–O Film

The effect of copper and manganese on the amorphization process in the surface layer of a technical Fe-3% Si alloy during annealing in the α → γ transition temperature range was determined by x-ray phase analysis. The presence of 0.5 wt. % Cu and 0.3 wt. % Mn in the initial Fe-3% Si solid solution significantly enhances the amorphization process that occurs when heated in the temperature range 920… 960∘C as an alternative to the α → γ phase transformation. The effect of amplification of amorphization is both in obtaining a larger amount of material in the amorphous state, and in the appearance of two amorphous phases, differing in average interatomic distance. The composition of the amorphous phase is approximately described as Fe89Si6Mg4Mn0.5Cu0.5 in the presence of Cu and Mn atoms and Fe90Si6Mg4 in the case of their absence in the amorphous layer.     Keywords: amorphization, non-ambient x-ray diffraction, Fe-3%Si, phase transition, thermal stability

Special features of the structure and phase composition of a Ti-23Al-26Nb/Al layered material obtained by plasma-spark sintering

Special features of formation of the structure of a layered intermetallic material based on titanium aluminide obtained by the method of plasma-spark sintering of foils are studied. The dependence of the structure on the temperature-and-time treatment parameters is determined. © 2013 Springer Science+Business Media New York

Solid state amorphization in a thin Fe-Si-Mg-O surface film triggered by the reduction of elements from oxides in the temperature range of the α-γ transformation

The study of the processes occurring in the surface layer of the MgO coated commercial alloy Fe-3%Si-0.5%Cu (grain oriented electrical steel) demonstrated that the amorphous phase in the form of a Fe-based solid solution is formed during continuous heating in the 95%N2 + 5%H2 atmosphere. For the purposes of this study, the following methods were used: non-ambient XRD at 20 –1060°C with heating and cooling at a rate of 0.5 dps, layer-by-layer chemical analysis performed by a glow discharge analyzer, scanning electron microscopy and energy dispersive X-ray spectroscopy. ThermoCalc software was used to calculate the potential phase equilibrium states. The amorphous phase was formed in the α → γ transformation temperature range, when the heating rates were altered in the surface layer of 1 µm initially consisted of a solid α-Fe-based solution with ~1– 2 wt.% Si with (MgFe)2 SiO4, (MgFe)O, SiO2 oxide inclusions. We suppose that (MgFe)2 SiO4 oxides are partly reduced by H2 to Mg2 Si molecular complexes, which become solid solutions in the temperature range of the metastability of the α-Fe crystal lattice with subsequent amorphization as an alternative to the α → γ transition. The amorphous state is obtained at 920 – 960°C and is retained both at subsequent heating (to 1060°C) and cooling (to 20°С), which is super-stable compared to the established metallic glasses. The composition of the amorphous phase can be described by the formula Fe89.5 Si6 Mg4 Cu0.5. © 2020, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved.Russian Foundation for Basic Research, RFBR: 20‑08‑00332Ministry of Education and Science of the Russian Federation, Minobrnauka: 11.1465.2014/K.Acknowledgements. This study was conducted using equipment provided by the Laboratory of Structural Analysis Techniques and Materials and Nanomaterials Properties of CKP Ural Federal University. The study was financially supported by Government Decree No. 211 of the Russian Federation, Contract No. 02. A03.21.0006 and within the framework of the state task issued by the Ministry of Education and Science of the Russian Federation, project No. 11.1465.2014/K. The reported study was funded by RFBR, project number 20‑08‑00332

Determination of critical points of amorphous Fe-Si-Nb-Cu-Mo-B alloy using non-ambient X-ray diffraction method

Critical points of amorphous alloy of Fe-Si-Nb-Cu-Mo-B system was determined using the non-ambient x-ray diffraction method. The sample with amorphous structure was produced by planar flow casting process. Temperature range of alloy nanocrystalline state was established. © 2019, National University of Science and Technology MISIS. All rights reserved

The influence of a combined strain-heat treatment on the features of electromagnetic testing of fatigue degradation of quenched constructional steel

The possibilities of the magnetic and eddy-current methods for testing fatigue degradation during low-cycle loading of quenched steel 50 (0.51% C) that was subjected to a combined strain-heat treatment according to an optimal regime that included friction treatment with subsequent tempering at T = 350 C, were investigated. It is shown that for steel that was subjected to a combined nanostructuring treatment, the accumulation of a plastic strain under "hard" cyclic loading can be tested using the coercimetric method and values of the residual magnetic induction on the major and minor magnetic-hysteresis loops, values of the maximum and initial magnetic permeabilities, and readings of an eddy-current instrument at a low excitation frequency of the eddy-current transducer. The appearance of surface fatigue cracks can be tested via eddy-current measurements at high frequencies, when the contribution of the crack formation in the hardened layer to the eddy-current characteristics is considerable. © 2013 Pleiades Publishing, Ltd

INFLUENCE OF THE X‑RAY DIFFRACTION EXPERIMENT PARAMETERS ON THE ACCURACY OF RIETVELD REFINEMENT

This work was aimed to evaluate the influence of X‑ray diffraction experiment parameters for accuracy of phase content and lattice constant determination by Rietveld refinement in the two-phase mixture.В настоящей работе проведена оценка влияния параметров записи дифрактограммы двухфазной смеси на точность определения содержания и периода решетки фазы методом безэталонного рентгенофазового анализа Ритвельда