Data Sets Formation on the Physical Properties of Oxide Scale Components for Theoretical Assessment of Efficiency Parameters of Laser Cleaning of Carbon Steels and Related Processes

There is a need in machine-building industries nowadays to automate technologies, in particular, laser ones, to remove surface oxide layers – mill scale, rust – from steel products/pieces in order to improve the energy effectiveness of processing. Herewith, a theoretical assessment method for the intensity of heating of the oxide layer and the phase transition in it can be used to optimize laser cleaning (LC) of the steel surface. To realize this, it is possible to use some calculation and modeling procedures that require, as a first step, the data collection and verification on the temperature-dependent properties of iron-containing condensed phases, as possible components contained, in particular, in scale, which is typically widespread into various metal products. In this regard, the formation of database for characteristics of oxide scale components by the way of selection of information on thermophysical (including optical) properties of the components mentioned and of steel base, which are required for a reliable calculation of the thermal efficiency parameters of the technology for laser cleaning of carbon steels, as well as such actively developed related technologies as laser cutting, drilling, coating remelting, etc., was chosen as the task of our research. An analytical overview of published experimental data made it possible to systematize information on a number of transport and other physical properties of iron-containing components at ambient pressure, including thermal conductivity (k) and diffusivity (a), density ρ, irradiation absorptance and integral emissivity in the temperature range from T ≈ 298 K to the melting temperatures of oxide and metal phases and above them. At the same time, a preliminary thermochemical estimation shows (on the calculated data) the existence of such thermodynamically stable forms of the condensed phase in the heating spot of scale layers during its LC at the melting point and above it, as Fe3O4, FeO, and Fe, which is consistent with known experimental data. Comparison of the values of a calculated by us (using the published values of k, ρ and molar heat capacity and using extrapolation in the high-temperature region) for the types of scale components under consideration with a set of experimental values of this parameter in current literature revealed the presence of differences for both oxide and metal phases. These new values make it possible to fill in a gap in the temperature range T = 1600–1800 K that existed in the data on the thermal diffusivity. The value of a = (0.83–0.92)·10–6 m2/s was also calculated for liquid iron oxide for the T ≈ 1800 K, which was not measured experimentally, that, obviously, prevented modeling of not only laser surface processing, melting and cleaning of steels, but also calculations in the field of metallurgical and other technologies, which are characterized by the presence of iron oxide melts during heating

Investigation of Upgraded Technology for Plasma Spraying of Bronze Powder Using the Combined Process with Hydrocarbon Additions

The object of the research is thermal spray process for the formation of metal coating from bronze powder in plasma-fuel variant, using direct current (DC) electric arc plasma torch, on steel samples. The aim of the work was to investigate and develop the technology for plasma-fuel spraying of functional coatings (for wear-resistant and antimicrobial applications) on machine-building and medical purpose pieces with increased process capacity and moderate energy consumptions in a comparison with conventional thermal spray technologies with use of inert and oxygen-free gas media. During the study, using experimental and thermodynamic estimation methods, the thermal and chemical parameters of the process under the spraying conditions at ambient pressure were characterized, which made it possible to determine the area of preferred regimes of the developed technology. On the modernized testing unit for plasma spraying of metal powders with power of up to 40 kW, operating using a controlled combination of three types of gases – technical nitrogen and propane-butane (LPG) with compressed air, the measurement and optimization of the operating and constructive/assembling parameters of the system for aluminum bronze coating spraying were established. In this case, the experiments were carried out using the designed fuel intensifier, which is joined with the PP-25 arc plasma torch, as well as additional technological equipment (protective shroud). For samples of the resulting coatings with a thickness of 100 to 450 m from the bronze material, testing of phase composition and some parameters of the resulting coatings on steel products was carried out. Operating capacity of the proposed process reaches 7–15 kg/h for bronze powder when using a moderate power of the torch – up to 35–40 kW and a limited flow rate of hydrocarbon gas (for example, LPG of the SPBT grade) – 0.1–0.35 kg/h. Analysis of the energy efficiency parameters of the developed technology, as well as its calculated technical characteristics, in a comparison with plasma and combined equipment of a similar purpose, showed that it has an advantage in terms of target indicators, in particular, in terms of energy consumption and total energy efficiency of the spraying unit, not less than 20–30 %. This makes it to proceed later to the stage of application of this technology into production based on a new process for the metal coating formation, in particular with antimicrobial properties, with improved energy efficiency of the process

Особенности процесса лазерной сварки разнородных материалов на железной и медно-никелевой основе

The paper presents investigations on influence of laser welding parameters with fiber lasers on formation of a welding joint, its geometrical and physical and mechanical properties while welding spring steel and Fe–Cu–Ni system.Исследовано влияние параметров процесса лазерной сварки с применением волоконных лазеров на процесс формирования сварного соединения, его геометрические и физико-механические свойства при сварке рессорно-пружинной стали и системы «железо – медь – никель»

Исследование модернизированной технологии плазменного напыления порошка бронзы с использованием комбинированного процесса с добавками углеводородов

The object of the research is thermal spray process for the formation of metal coating from bronze powder in plasma-fuel variant, using direct current (DC) electric arc plasma torch, on steel samples. The aim of the work was to investigate and develop the technology for plasma-fuel spraying of functional coatings (for wear-resistant and antimicrobial applications) on machine-building and medical purpose pieces with increased process capacity and moderate energy consumptions in a comparison with conventional thermal spray technologies with use of inert and oxygen-free gas media. During the study, using experimental and thermodynamic estimation methods, the thermal and chemical parameters of the process under the spraying conditions at ambient pressure were characterized, which made it possible to determine the area of preferred regimes of the developed technology. On the modernized testing unit for plasma spraying of metal powders with power of up to 40 kW, operating using a controlled combination of three types of gases – technical nitrogen and propane-butane (LPG) with compressed air, the measurement and optimization of the operating and constructive/assembling parameters of the system for aluminum bronze coating spraying were established. In this case, the experiments were carried out using the designed fuel intensifier, which is joined with the PP-25 arc plasma torch, as well as additional technological equipment (protective shroud). For samples of the resulting coatings with a thickness of 100 to 450 mm from the bronze material, testing of phase composition and some parameters of the resulting coatings on steel products was carried out. Operating capacity of the proposed process reaches 7–15 kg/h for bronze powder when using a moderate power of the torch – up to 35–40 kW and a limited flow rate of hydrocarbon gas (for example, LPG of the SPBT grade) – 0.1–0.35 kg/h. Analysis of the energy efficiency parameters of the developed technology, as well as its calculated technical characteristics, in a comparison with plasma and combined equipment of a similar purpose, showed that it has an advantage in terms of target indicators, in particular, in terms of energy consumption and total energy efficiency of the spraying unit, not less than 20–30 %. This makes it to proceed later to the stage of application of this technology into production based on a new process for the metal coating formation, in particular with antimicrobial properties, with improved energy efficiency of the process.Исследование посвящено процессу газотермического формирования покрытия из бронзового порошка в плазменно-топливном варианте с использованием электродугового плазмотрона на стальных образцах. Цель работы – изучение технологии для плазменно-топливного напыления функциональных покрытий (износостойкого и антимикробного применения) на изделия машиностроительного и медицинского назначения с повышенной производительностью процесса и умеренными энергозатратами по сравнению с традиционными методами термического напыления в инертных и бескислородных газовых средах. С помощью экспериментального и термодинамического расчетного методов оценивались тепловые и химические параметры процесса в условиях напыления при атмосферном давлении, что позволило определить область предпочтительных режимов данной технологии. На модернизированной авторами установке плазменного напыления порошков электрической мощностью до 40 кВт, работающей с регулируемым сочетанием технических азота и пропан-бутана, а также воздуха, проведены измерение и оптимизация режимных и конструктивных параметров системы нанесения покрытия из алюминиевой бронзы. Эксперимент осуществлен с использованием разработанного топливного интенсификатора, стыкуемого с дуговым плазмотроном ПП-25, и дополнительной технологической оснастки (защитного кожуха). Для полученных покрытий толщиной от 100 до 450 мкм из промышленного порошка алюминиевой бронзы проведено тестирование фазового состава и некоторых параметров получаемых покрытий на стальных изделиях. Производительность предложенного процесса достигает 7–15 кг/ч по порошку при умеренной мощности плазмотрона до 35–40 кВт и умеренном расходе углеводородного газа (предпочтительно технического пропан-бутана марки СПБТ) 0,1–0,35 кг/ч. Оценка параметров энергоэффективности разработанной технологии и ее расчетных технико-экономических характеристик в сравнении с плазменным и комбинированным оборудованием аналогичного назначения показала, что она имеет преимущество, в частности, по удельным энергозатратам и общему энергетическому КПД аппарата не менее чем на 20–30 %. Это позволяет перейти к стадии последующего внедрения данной технологии в производство на основе нового процесса получения металлопокрытий различного назначения, в том числе с антимикробными свойствами.

Peculiar Features of Laser Welding Process for Dissimilar Materials on Ferrum or Copper-Nickel Base

The paper presents investigations on influence of laser welding parameters with fiber lasers on formation of a welding joint, its geometrical and physical and mechanical properties while welding spring steel and Fe–Cu–Ni system

Structure-phase condition and tribological properties of coatings based on self-fluxing nickel alloy PG-12N-01 after laser surfacing

Some parameters of laser surfacing of self-fluxing nickel alloy PG-12N-01 are considered. Different structures containing a low-melting -Ni – Ni3B eutectic and a -Ni – Cr3C2 eutectic that crystallizes at a higher temperature and forms the strength skeleton of the coating may form depending on the rate of the surfacing. The effect of the rate of the surfacing on the wear resistance of the coating and on the coefficients of dry friction are determined