Influence of Carbon Content on the Formation of a Contact  Interparticle Surface during Hot Post-Pressing

Egorov, M. S.; Egorova, R. V.; Ковтун, М В

doi:10.23947/2541-9129-2023-7-2-90-101

Cited by 3 publications

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References 8 publications

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“…In the microstructure of the obtained samples it is possible to observe the deformed part of the material volume due to pore inflow. This moment is clearly visible on the microstructures, which is quite consistent with the analytical equality (2), according to which the pore size increases with the enlargement of powder particles at the same initial porosity of the studied pressings [9][10][11].…”

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confidence: 83%

Peculiarities of particle splicing at interlayer boundaries of hot-formed powder materials

Goncharova

2024

E3S Web Conf.

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Modern production of machine-building parts and building structures is directly related to the production of high-quality hot-formed powder materials. Powder metallurgy as a modern innovative technology, creating materials with unique physical properties, has such a significant advantage as environmental safety. The absence of aggressive and environmentally hazardous components in the technology makes the process of manufacturing powder steels harmless to the environment. The present scientific study deals with the given microstructures of hot-pressure treated powder materials. Residual porosity, which significantly affects the functional properties (mechanical and physical), is considered to be a fundamental factor influencing the areas of powder steel use. The mechanism of mutual diffusion of the introduced components and peculiarities of modeling the structure of powder blanks under conditions of sintering and subsequent deformation were studied. The influence of initial powder particle size on the formation of powder alloys structure under the characteristic features of homogenization under sintering conditions was analyzed. The conducted works allow to study the character of influence of technological parameters in the process of processing on the quality of powder materials splicing, formation of features of their structure and functional properties and qualities. The structure of almost porosity-free steel obtained during the tests of hot-pressure treatment is characterized by complete coverage of the entire number of particles by plastic deformation, which indicates its homogeneity, inherent in the initial particle size distribution of iron powder. The conducted scientific studies of physical processes during hot pressure deformation prove the decisive influence of the choice of technological parameters on improving the quality of splicing, as well as on the formation of microstructure and properties of powder steels.

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Section: Resultssupporting

confidence: 83%

Peculiarities of particle splicing at interlayer boundaries of hot-formed powder materials

Goncharova

2024

E3S Web Conf.

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Development of Interparticle Bonding during Sintering of Metal Powders with the Addition of Carbon

Egorov,

Egorova

2023

Safety of Technogenic and Natural Systems

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Introduction. Publications on sintered metal powder parts consider interparticle bonding in hot-deformed materials and features of low-alloy structural steels, as well as the use of carbon-containing materials. The authors of the presented article have previously investigated sintering in relation to structural changes in the material, described changes in physical and mechanical properties, reduction of oxides, recrystallization, etc. This paper shows the relationship of mechanical properties of powder steels with the parameters of intracrystalline bonding. The kinetics of its development during sintering is demonstrated for the first time. The study objective is to find out how sintering affects the interparticle bonding and structure of powder alloys with iron and carbon. The task is to study the technological modes of sintering samples from alloyed and pure iron powder to achieve the best mechanical characteristics.Materials and Methods. The powders of the Höganäs company were sintered at a temperature of 900-1150 ºС for 0.5–2.5 hours. The protective gas medium (dissociated ammonia) made it possible to prevent oxidative and other sintering reactions. For static cold pressing, a hydraulic press 2PG-125 with a maximum force of 1250 kN was used.Results. For the first time, the presence of intracrystalline bonding mechanisms with different intensity during sintering has been experimentally established. The dependences of the increment of the relative area of the contact surface on the duration of the isothermal exposure were constructed. With an increase in the sintering temperature to 1150 ºС and a holding time of more than 80 minutes, the contact surface area gradually increased. It was shown that the samples from the powder grades under consideration formed an intracrystalline bonding on the entire contact surface at 1150 ºС. Therefore, this technology can be recommended for practical use. The addition of graphite to the charge slows down the growth of the contact surface. At the same time, the molds from pure powder ABC100.30 and from Distaloy HP-1 powder showed differences. In the first case, with the addition of graphite to the charge, the contact surface developed more intensively than in the second one. The obtained results were recorded in the photo and visualized in the form of graphs.Discussion and Conclusion. According to the results of mechanical tests, it is possible to estimate the proportion of the contact section of the molding with intracrystalline bonding. Its feature is the structural correspondence of the interparticle surface of the splice and the intergrain boundary. The value of this boundary is determined by comparing the relative area of the contact section with the intracrystalline bonding and the relative area of the contact surface. The possibilities of improving the quality of bonding of powder steels by increasing the temperature and time of their exposure during sintering are determined.

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Diffusion Processes in the Formation of the Structure of Alloyed Powder Steels

Egorov,

Egorova,

Eremeeva

2024

Safety of Technogenic and Natural Systems

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Introduction. The production of alloyed powder steels continues to be one of the most promising areas in domestic powder metallurgy. This is due to the high level of performance characteristics and the wide range of products that can be produced. Creating materials with desired properties is a complex process that involves various phenomena. One of these phenomena is the diffusion alloying of iron-based powder steels, which plays a special role in this process. The creation of alloyed powder steels in the Fe-NiO and Fe-Ni systems is important for metallurgy and metalworking, as they are used for coating and sintering to obtain materials with specific properties. In addition, the diffusion of nickel in iron during heat treatment is considered to improve material properties. Recent advances in the study of mutual diffusion are associated with the investigation of homogeneous systems. However, mutual diffusion even in single crystals always occurs under spatially inhomogeneous conditions. The modern literature has not sufficiently studied the mutual diffusion in two- and multi-component powder systems. Therefore, the aim of this work is to determine the effect of diffusion alloying with nickel and nickel oxide of iron-based powder steel on the processes of obtaining powder materials. Within the framework of this goal, the following tasks were set: to investigate the diffusion processes of interactions between pairs in the Fe-NiO and Fe-Ni systems, as well as to study technological modes of sintering and reducing annealing of samples in order to achieve maximum mechanical properties that would ensure the formation of a high-quality product.Materials and Methods. The work used iron powder of the PZHRV 2.200.26 brand manufactured by PJSC Severstal (Cherepovet) and carbonyl nickel powder PNK-UT3, obtained by the electrolytic method or splitting nickel salt with an aqueous solution, according to GOST 97922–97. Before use, the powders were tested using a universal laser particle size measuring device model FRITSCH ANALYSETTE 22 MicroTecplus and a Beckman COULTER No. 5 submicron particle analyzer. A two-cone mixer RT-NM05S (Taiwan) was used to prepare the charge. Pressing was carried out on a hydraulic press model TS0500–6 (China) in laboratory molds. Samples were obtained by pressing pre-hardened 3 mm diameter powder pins into a carbonyl nickel or NiO charge with a dispersion of 5–10 microns. Recovery annealing was carried out in a SNOL 6.7/1300 laboratory muffle furnace at 700°C, followed by annealing-sintering at temperatures of 1050, 1150 and 1250°C in a hydrogen atmosphere for 9 hours. Microstructural analysis was performed using a NEOPHOT-21 optical microscope. A Hitachi S-3400N scanning electron microscope was used to study the fine structure of the material. The distribution of element concentrations in the Fe-Ni diffusion zone was studied by local X-ray spectral analysis using the Kamebaks installation.Results. The studies showed that the porosity of the powder component after pressing was 12%. Diffusion in the iron-nickel powder system was 5–10 times higher when using carbonyl nickel compared to oxide. It was also found that high diffusion rates of reduced nickel led to faster and more uniform penetration of alloying elements into the material. The dependences of the distribution of nickel concentration and its oxide content after sintering were determined, as well as the indicators of diffusion interaction between iron, nickel, and nickel oxide during annealing, where nickel oxide was reduced and sintering occurred at different temperatures.Discussion and Conclusion. The analysis of the results obtained indicates a different intensity of diffusion processes in powder-alloyed steels. This can be explained by both the distortion of the crystal lattice of the starting materials and the increased segregation of defects, such as defective zones, that are formed during compaction of the material. This approach to studying two-component diffusion allowed us to compare the intensity of element diffusion redistribution depending on chemical composition and temperature, and to estimate the effective activation energy of diffusion. As a result of our studies, we have established quantitative parameters for the distribution of nickel concentration in the iron matrix, depending on sintering temperature, which affects the formation of high-quality materials. The research results obtained are of interest to specialists in powder metallurgy and heat treatment, as they can be used in the development of new multicomponent alloys.

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Influence of Carbon Content on the Formation of a Contact Interparticle Surface during Hot Post-Pressing

Cited by 3 publications

References 8 publications

Peculiarities of particle splicing at interlayer boundaries of hot-formed powder materials

Peculiarities of particle splicing at interlayer boundaries of hot-formed powder materials

Development of Interparticle Bonding during Sintering of Metal Powders with the Addition of Carbon

Diffusion Processes in the Formation of the Structure of Alloyed Powder Steels

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