Increasing the resistance of a NiCrBSi coating to heat wear by means of combined laser heat treatment

Testing of NiCrBSi coatings formed by gas-powder laser cladding and combined laser heat treatment, including laser cladding and high-temperature annealing, were conducted under conditions of sliding friction on the Kh12M steel according to the pin-on-disk scheme. The combined processing resulting in the formation of large carbides and chromium borides in the coatings is shown to increase their wear resistance by a factor of 1.8 at sliding velocities of 6.1 and 9.3 m/s, when there is significant frictional heating of the friction surfaces. © 2018 Author(s)

Corrections to the Nonrelativistic Ground Energy of a Helium Atom

Considering the nuclear motion, the authors give out the nonrelativistic ground energy of a helium atom by using a simple but effective variational wave function with a flexible parameter $k$. Based on this result, the relativistic and radiative corrections to the nonrelativistic Hamiltonian are discussed. The high precision value of the helium ground energy is evaluated to be -2.90338 a.u., and the relative error is 0.00034%.Comment: 8 pages, no figures, 2 table

The effect of thickness on the properties of laser-deposited NiBSi-WC coating on a Cu-Cr-Zr substrate

Ni/60WC coatings on copper substrate were placed via laser deposition (LD). A structural study was conducted using electron microscopy and a microhardness evaluation. Two body abrasive wear tests were conducted with a pin-on-plate reciprocating technique. A tool steel X12MF GOST 5960 (C-Cr-Mo-V 1.6-12-0.5-0.2) with a hardness of 63 HRC was used as a counterpart. The following results were obtained: Precipitation of the secondary carbides takes place in the thicker layers. Their hardness is lower than that of the primary carbides in the deposition (2425 HV vs. 2757 HV) because they mix with the matrix material. In the thin layers, precipitation is restricted due to a higher cooling rate. For both LD coatings, the carbide's hardness increases compared to the initial mono-tungsten carbide (WC)-containing powder (2756 HV vs. 2200 HV). Such a high level of microhardness reflects the combined influence of a low level of thermal destruction of carbides during laser deposition and the formation of a boride-strengthening phase from the matrix powder. The thicker layer showed a higher wear resistance; weight loss was 20% lower. The changes in the thickness of the laser deposited Ni-WC coating altered its structure and wear resistance. © 2019 by the authors.Acknowledgments: This work was supported by the state orders of IMP UB RAS on the subjects “Laser”, “Structure”. The authors are grateful to the collective use center “Plastometry” of the Institute of Mechanical Engineering of the Ural Branch of the Russian Academy of Sciences for their help in conducting structural studies

Reducing the distortion in thin-sheet structures made from high-strength steel based on CAE-welded joint analysis

High competition in the field of mechanical engineering requires the manufacture of lightweight thin-sheet structures made of high-strength steels ensuring the geometry of a certain accuracy. Supporting a given geometry is achievable by improving methods to reduce residual deformations. Therefore, the purpose of the investigation is to reduce the distortion based on the analysis of the influence of clamping rigidity on the stress-strain state of the assembly using computer simulation by the finite element method. The result of the study is a clamping model that allows to adjust the level of residual stresses and deformations, confirmed experimentally. © 2019 IOP Publishing Ltd.Foundation for Assistance to Small Innovative Enterprises in Science and Technology, FASIE: 11995GU/2017The present study was supported by FASIE Grant №11995GU/2017. This work was done within the state order of IMP UB RAS on the subject “Laser”

Structure study of laser treated NiBSi/WC coatings on bronze substrate

Metal matrix composite layers like NiCrB-WC on the substrate of bronze C18150 were performed by laser deposition. The influence of layer thickness and operating parameters on the structural characteristics, microhardness, and crack susceptibility were analyzed. Rational technological modes were defined applied to a diode laser.Проведено сравнение металоматричных покрытий вида NiCrB-WC на основе из бронзы С18150, полученных лазерной наплавкой на основе из бронзы CuCrZr. Проанализированы зависимости изменений структурных характеристик, твердости, склонности к образованию трещин от толщины покрытий и технологических параметров. Определены рациональные режимы обработки с использованием диодного лазера

Properties of arc-sprayed coatings from Fe-based cored wires for high-temperature applications

Equipment of a thermal power plant is subjected to high temperature oxidation and wear. This raises operating costs through frequent repair of worn parts and high metal consumption. The paper proposes a possible solution to this problem through arc spraying of protective coatings. Cored wires of the Fe-Cr-C basic alloying system are used as a feedstock. Additional alloying by Al, B, Si, Ti and Y allows one to create wear- and heat-resistant coatings, which are an attractive substitute of more expensive Co- and Ni-based materials. © 2017 Author(s)

Wear-resistant nickel-based laser clad coatings for high-temperature applications

The effect of high-temperature processing on laser clad Ni-based coatings is studied. Annealing at 1025°C forms thermally stable framework structures with large chromium carbides and borides. As a result, improved hardness and wear resistance of the coating are maintained when heated to 1000°C. Stabilizing annealing also increases the frictional thermal resistance of the NiCrBSi coating. Under high-speed (3.1– 9.3 m/s) sliding friction, when the surface layer temperature reaches about 500 –1000°С and higher, the wear resistance of the coating increases by 1.7 – 3.0 times. The proposed approach to the formation of heat-resistant coatings is promising, in particular, for a hot deformation tool and other components of metallurgical equipment operating under high thermal and mechanical loads. Such products include crystallizer walls of continuous casting machines. For the walls, the development of laser cladding technology for wear-resistant composite coatings on copper alloys is relevant as an alternative to thermal spraying. The cladding of composite NiBSi-WC coatings of 0.6 and 1.6 mm thickness on a Cu-Cr-Zr bronze substrate heated to 200 – 250°C with a diode laser is considered. The presence of boron causes the formation of the W(C, B) carboboride phase, whose hardness is higher than that of WC in the initial powder. Depending on the thickness of coatings and, accordingly, on the duration of heating and the subsequent cooling, the process of secondary carboborides precipitation from the solid solution can be suppressed (in the “thin” coating) or activated (in the “thick” coating). This leads to a higher wear resistance under friction sliding 1.6 mm thickness coating. © 2019, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved.Institute of Education Sciences, IES: АААА-А18-118020790147-4Russian Science Foundation, RSF: 19-79-00031АААА-А18-118020190116-6The work was supported by the state orders of IMP UB RAS on the subjects “Laser” and “Structure” №АААА-А18-118020190116-6 and IES №АААА-А18-118020790147-4. The study of the evolution of the structure of NiCrBSi coatings during heating was carried out with financial support from the Russian Science Foundation, grant № 19-79-00031. The structural studies were done on the equipment installed at the Plastometriya Collective Use Center of IES UB RAS

Massively parallel computing on an organic molecular layer

Current computers operate at enormous speeds of ~10^13 bits/s, but their principle of sequential logic operation has remained unchanged since the 1950s. Though our brain is much slower on a per-neuron base (~10^3 firings/s), it is capable of remarkable decision-making based on the collective operations of millions of neurons at a time in ever-evolving neural circuitry. Here we use molecular switches to build an assembly where each molecule communicates-like neurons-with many neighbors simultaneously. The assembly's ability to reconfigure itself spontaneously for a new problem allows us to realize conventional computing constructs like logic gates and Voronoi decompositions, as well as to reproduce two natural phenomena: heat diffusion and the mutation of normal cells to cancer cells. This is a shift from the current static computing paradigm of serial bit-processing to a regime in which a large number of bits are processed in parallel in dynamically changing hardware.Comment: 25 pages, 6 figure

КЛЕТОЧНО–АВТОМАТНАЯ МОДЕЛЬ РАЗДЕЛЕНИЯ ФАЗ ПРИ ОТЖИГЕ СЛОЕВ НЕСТЕХИОМЕТРИЧЕСКОГО ОКСИДА КРЕМНИЯ

The suggested model simulates the structural evolution of the SiOm (m < 2 ) layer with a thickness of the order of 3—30 nm and the formation of Si nanoclusters in that layer during thermal annealing at temperatures of 900—1200 °C. The model does not take into account the crystallinity or amorphous structure of the nanocluster. The 3D cellular automaton model implemented by means of SoftCAM software (CA) on 3D cubic grid with a cell scale of 0.54 nm is synchronous, does not use Margolus’s block neighborhood and is open to the incorporation of ab initio calculations for SixOy clusters. The state of the CA cell is determined by three variables (x, y, z), taking on 0,1,2 , ..., 255 and corresponding to the number of atoms of silicon and oxygen and the arbitrary “free volume” in a cell and the fourth variable δ, taking on 0, 1, 2 and corresponding to cells belonging to nanoclusters, SiOx matrix or the interface between them. The local transition rules are determined from the following considerations: 1) for each cell, the scalar “free energy” is calculated similar to the thermodynamic potentials, as it depends only on the state of the cell; 2) the “free energy” consists of three parts: the internal U(x, y), the elastic G(z) and the surface E(δ); 3) the matter exchange between cells is determined by probabilities depending on the difference between the “free energy” by the Fermi— Dirac relation. The model traces the total number of nanoclusters, their average size and the average distance between them. The simulation results are consistent with published experimental data. Предложена модель, имитирующая эволюцию структуры слоя SiOm (m < 2) толщиной порядка 3—30 нм и формирование в нем нанокластеров кремния в процессе термического отжига при температурах 900—1200 °С. Модель не принимает в расчет кристалличность или аморфность структуры нанокластера. Трехмерный клеточный автомат (КА) на кубической сетке, построенный в программе SoftCAM, является синхронным, не использует блочную окрестность Марголуса и открыт для внедрения данных ab initio расчетов SixOy−кластеров. Состояние ячейки КА задано тремя переменными (x, y, z), принимающими значения 0, 1, 2, ..., 255 и соответствующими числу атомов кремния, кислорода и условному свободному объему в ячейке с ребром 0,54 нм, а также четвертой переменной δ, принимающей значения 0, 1, 2 и соответствующей принадлежности ячейки нанокластеру, матрице SiOx или границе между ними. Функции локального перехода КА определены из следующих соображений: 1) для каждой ячейки вычисляется скаляр «свободная энергия», аналогичный термодинамическим потенциалам, поскольку зависит только от состояния ячейки; 2) «свободная энергия» есть сумма трех энергий: внутренней U(x, y), упругой G(z) и поверхностной E(δ); 3) обмен вещества между ячейками определяется вероятностями, зависящими от разности «свободных энергий» по соотношению Ферми—Дирака. В модели отслежена динамика общего числа нанокластеров, их средний размер и среднее расстояние между ними. Установлено, что результаты моделирования согласуются с имеющимися в литературе экспериментальными данными.