Iron-based Powder Materials Research Articles

Influence introducing various plasticizers into an initial charge on the structure and properties of iron-based powder materials alloyed with copper

Influence introducing various plasticizers into an initial charge on the structure and properties of iron-based powder materials alloyed with copper

Study of the Plasticizer Effect on Technological Properties of Iron-Based Powder Materials Alloyed with Copper

Study of the Plasticizer Effect on Technological Properties of Iron-Based Powder Materials Alloyed with Copper

Process of Sintering Iron-Based Powder Materials Alloyed with Copper with Introduction of Various Plasticizers Into an Initial Charge

Process of Sintering Iron-Based Powder Materials Alloyed with Copper with Introduction of Various Plasticizers Into an Initial Charge

Study on the Influence of Warm Die Compaction Behavior on the Mechanical Properties of Iron-Based Powder Materials

Study on the Influence of Warm Die Compaction Behavior on the Mechanical Properties of Iron-Based Powder Materials

Determination of porosity functions in the pressure treatment of iron-based powder materials in agricultural engineering

One of the most effective ways to obtain products with the required performance characteristics is the cold plastic deformation of porous workpieces. The relevance of the subject under study is due to the need to increase the reliability of the stress-strain state assessment during the plastic processing of porous workpieces by clarifying the porosity functions. The purpose of the study is to develop a method for describing the mechanical characteristics of porous bodies by single functions, the nature of which is determined by the properties of the base material and does not depend on the initial porosity. Analytical, numerical, experimental, and computational methods using modern specialised software systems were used to examine the processes of plastic deformation. The study presents a method for describing the mechanical characteristics of porous bodies with single functions. A set of interrelated methods and techniques is based on the basic provisions of the mechanics of plastic deformation of porous bodies and allows obtaining reliable porosity functions for this material, by clarifying theoretical dependencies by experimental studies. Therewith, experimental data were obtained in experiments on axisymmetric upsetting of cylindrical samples without friction at the ends. Based on the conducted theoretical studies, porosity functions for iron-based materials are obtained. Samples of five different initial porosities were used for the study. As a result of processing experimental data, final expressions for the porosity functions of the iron-based powder workpiece material are obtained. The study also presents a method for calculating the accumulated deformation of the base material. Flow curves for iron-based powder materials are plotted. The obtained results will allow formulating the practical recommendations for the development of technological processes for the plastic processing of powder materials by pressure to obtain products with specified physical and mechanical properties

Effect of Fullerenes Additions on Physical – Mechanical Properties of Hot-Forged Iron-Based Powder Materials

It is possible to expand the applications ranges of powder material products by enhancing the performance properties of these products in addition to their manufacturability and reliability together, it’s possible by materials structures modification. In this paper, the effect of fullerene (C60) additives to iron-based powder material has been studied. All samples produced by Hot-Forging (HF) powder materials technology. Green and HF density of the obtained samples calculated by volume / weight and Archimede’s principle, respectively. The effect of technological parameters on the microstructure of carbon steels’ samples was done by an ALTAMI MET-1M metallographic microscope. Tensile test executed by using of a universal testing machine UMM –5 and the microhardness (HV10) was measured by REICHERT hardness test machine. The results showed that the HF C60 steels’ samples had higher density and strength of 0.81 and 25%, respectively, with a good plasticity in comparison with graphite steels’ samples.

Determining the influence exerted by the static conditions of final squeezing on the compaction process of iron-based powder materials

This paper reports a study into the process of re-compaction of powder briquettes in the conditions of static pressing at a pressure of 800 MPa. The technological parameters of the pressing process have been analyzed, which make it possible to improve the compaction of powder briquettes based on iron. Such parameters are the outer greasing, which reduces friction between a green compact and the walls of the press tool matrix, and the firing, which removes the deformation strengthening of the green compacts and increases their plasticity.
 The green compacts’ sealing mechanism involved in the final squeezing process has been established, which is associated with the grinding of pre-compressed particles due to the strain in the contact areas. The increase in the stressed state of green compacts following the final squeezing was confirmed by the results of studying the residual micro-strains.
 The change in the stressed state of iron green compacts has been confirmed by the study into the structurally sensitive characteristics, which include the materials’ magnetic and electrical properties. Determining the magnetic characteristics has shown that final squeezing leads to an increase in coercive force, which can be explained by both the increase in the stressed state and the grinding of grains. Investigating the impact exerted by the annealing environment on the value of magnetic characteristics has demonstrated that annealing in hydrogen is more effective in terms of improving magnetic properties than annealing in a vacuum. This is due to the refining of grain boundaries through the processes of reduction of oxide films.
 The study of the mechanical characteristics of green compact materials based on iron powder has established that final squeezing leads to an increase in the hardness and strength of materials depending on the conditions of deformation. A significant improvement in the green compacts’ strength (820‒824 MPa) is due to both a decrease in porosity by 8‒10 % and an increase in the contact area as a result of plastic deformation after the annealing

Revisiting the Applicability Question of G.V. Samsonov’s Activated Sintering Concept in Studying Deformation Processes of Powder Materials

Some of Yu.G. Dorofeyev’s recollections about joint work and meetings with G.V. Samsonov, an outstanding materials science expert, are presented. Meetings in Yugoslavia, where G.V. Samsonov and M.M. Ristic, together with other world-famous scientists, developed the International Institute for the Science of Sintering, are of special importance. In the last years of his life, G.V. Samsonov proposed the concept of sintering activation by additives that act as electron acceptors and additionally contribute to the fraction of the ionic bond in the material. The possibility of applying this concept when developing activator additives, reducing the plastic deformation activation energy of powder materials based on iron, is considered. Sintering activation during the formation of stable electron configurations can be performed due to (i) accelerating grain-boundary heterodiffusion of the matrix material in the presence of segregations of the phase containing the activating microadditives (the W–Ni system), (ii) intensifying shrinkage during the plastic flow of the material matrix particles in the presence of segregation of phases containing the activating microadditive (the Fe–Ni, Fe–Co, Fe–Mn system), and (iii) an increase in the self-diffusion coefficient of host metal atoms due to the expansion of the occurrence region of a less closely packed crystal lattice (α phase) with the dissolution of the activating additive (the Fe–Mo system). The analysis of available information touching the prospects of using manganese and chromium as additives—densification activators—is presented. A decrease in the activation energy of densifying iron-based powder materials can be enabled when introducing manganese additives. Herewith, it is promising to apply diffusion saturation technology. The question of using chromium as the activator has no confirmatory answer and assumes the necessity of the additional investigation.

On the question of the applicability of G.V. Samsonov’s activated sintering concept in studying the processes of powder material deformation

Some Yu.G. Dorofeev’s memoirs about joint work and meetings with outstanding materials science expert G.V. Samsonov are given. Meetings in Yugoslavia were of particular importance where G.V. Samsonov and M.M. Ristićtogether with other worldfamous scientists created the International Institute for the Science of Sintering. In the last years of his life, G.V. Samsonov proposed the concept of sintering activation by additives that act as electron acceptors and additionally contribute to the ionic bond in the matrix material. The paper considers the possibility of using this concept in the development of activating additives that reduce the activation energy of the plastic deformation of iron-based powder materials. Sintering activation when forming stable electronic configurations can be accomplished by: 1) accelerating the grain-boundary heterodiffusion of the matrix material in the presence of phase segregations containing an activating microadditive (W–Ni system); 2) intensifying shrinkage durng the plastic flow of matrix material particles facilitated by diffusion porosity formed in the additive particles as a result of predominant additive atom diffusion into base metal particles (Fe–Ni, Fe–Co, Fe–Mn systems); 3) increasing the self-diffusion coefficient of base metal atoms due to the expanded area of a less close-packed crystal lattice (αphase) upon activating additive dissolution (Fe–Mo system). The article reviews the information available on the prospects for using manganese and chromium as compaction activating additives. The compaction activation energy of iron-based powder materials can be reduced by introducing manganese additives. At the same time, the use of diffusion saturation technology is promising. The question of using chromium as an activator does not have an unambiguous answer and suggests the need for further study.

SURFACE HARDENING OF POWDERED IRON-CARBON ALLOYS

There are many ways to improve the quality of iron-carbon alloys used as structural materials, one of which is surface heat treatment with highly concentrated energy streams. The effect of electron-beam heating on the structure and properties of powder-metal ceramic materials was studied in this work. In order to solve this problem, the following tasks were solved: the study of the influence of the technological parameters of electron-beam processing on the structure and phase composition of the sintered materials on the basis of iron powder with graphite additions, determination of the influence of the thickness of the surface layer on the temperature gradient under the electron beam treatment of the material surface and formation structure, investigation of the influence of the chemical composition and the thickness of the surface layer on the hardness and microhardness of materials after electron beam processing. The advantages of electron-beam processing are shown in comparison with other methods of hardening the surface of parts. The influence of electron-beam processing regimes on the structure and phase composition of layered iron-based powder materials is studied. In the work the process of surface heat treatment of powdered laminated iron-carbon alloys is investigated. It was established that doping of a surface layer with carbide chromium allows to increase the surface strength of materials after treatment with an electron beam twice. Distribution of structural components of iron-carbon alloy under surface heat treatment depending on the thickness of the surface layer is investigated. Research results can be used to create economically alloyed structural iron-carbon alloys, which must have high surface hardness and high bulk strength. It is shown that in the middle of the samples the microhardness is practically the same for all materials and is about 3-4 GPa. On the surface, with a thickness of the upper layer of 0.5-1.0 mm, the average values of microhardness are about 5.0-5.5 GPa. With an increase in the thickness of the layer to 1.5-2.0 mm, the average microhardness reaches about 7.5-9.0 GPa. Surface hardness of materials also increases to 68 HRC with hardness in the middle of about 35-40 HRC. Research results can be used to create economically alloyed structural iron-carbon alloys, which must have high surface hardness and high bulk strength .

Influence of rolling scale processing parameters on morphology of reduced iron powder particles

The use of various modes of rolling scale preparation and technological regimes of its reduction to obtain iron powder is discussed, and some of the results of original research in this field are given. The main aim of this research is to obtain a reduced iron powder with the highest level of physical and technological characteristics. The use of modern diagnostic properties of materials allows scientists to collect and analyze information received from experts around the world with the help of decision support in the field of powder materials with physical and technological characteristics of the unique complex. The prerequisites for using the reduction method for the processing of rolling production waste are discussed in the article. The complex of physical and technological properties of iron-based powder materials for production of sintered products for various applications is investigated. The presented methodology for assessing the properties of materials using advanced methods of analysis allow to obtain real information about complex of performance characteristics of iron-based powder materials. The patterns of joint influence of technological process factors on the form and size of synthesized iron powder particles are defined. A feature of the development is a comprehensive accounting and mathematical presentation of influence of scale preparation parameters (grinding feed rate, temperature and time of isothermal holding at reduction) on the surface shape and the size of the reduced iron powder particles in order to detect the presence of synergy of these factors. The regularities in the future will help to develop mathematical models to quantify the degree of influence of technological factors on the structure, physicochemical and operational properties of powder materials. The research results can be applied by experts in metallurgy and mechanical engineers to develop new resource recovery technology of rolling production waste, as well as to create new kinds of sintered powder materials with improved performance characteristics.

Fabrication of metal-teflon bearings with specified operational properties

This study is devoted to the fabrication technology of composite materials with specified properties prepared from iron-based powder materials. A procedure of the ultrasonic impregnation of the samples with infiltrative compositions at various concentrations, temperatures, and time is described. The characteristics of oil absorbability are given. The physicomechanical properties of impregnated samples compared with the samples fabricated using the traditional method are investigated. The fabricated materials have a decreased friction coefficient (by a factor of ∼1.25) and improved leak-tightness (the samples withstood a pressure of 25 atm for 1 min). Metallographic analysis shows pores of sintered samples being filled with impregnating suspensions. The efficiency of this technology for achieving the specified operational properties of the wares is substantiated.

Special Features of Distribution of Microalloying Elements in Hot-Deformed Iron-Base Powder Materials and their Influence on the Quality of Interparticle Bonding

Auger electron microscopy of surfaces of low-temperature fractures of hot-deformed powder iron microalloyed with Na and Ca is performed. Special features of the distribution of impurity and alloying elements in various zones of fracture of specimens are analyzed and its correlation with the process of interparticle bonding in hot die forming of porous preforms is established.

Modeling of structurization processes and mechanical properties of porous powder materials

A new approach to the formation of the mechanical properties of iron-based powder materials is proposed. The approach is based on model ideas on the structurization of bulk powder mixtures under compacting pressure. It is established that as the porosity increases (decreases) within the range 5–25 %, the structure of compacted powder mixtures (compacts) alternates between mesostructural and submesostructal states.

Corrosion resistance of phosphorus-clad iron powders in biological and inorganic media

The production and use of clad iron-based powder materials is a promising area of powder metallurgy that allows variation in their process and magnetic properties in wide ranges. The corrosion properties of phosphorus-clad iron powders and their interaction with biological media of the living organisms are studied. The PZhRV 3.200.26 (Ukraine), AHC 100.29 (Sweden), and PZhV 200 (Russia) iron powders with different particle sizes are clad with phosphorous by the method of thermochemical decomposition of phosphorous compounds and by the method of thermochemical synthesis in a vibrating bed. Corrosion tests of the iron powders clad with phosphorous are performed in a 3% NaCl solution. Calculations of the corrosion depth index show that the clad powders are much more resistant to corrosion in aggressive media (3–4 points according to the ISO 11130:2010 standard) than the starting powders (1 point). The low values of the corrosion depth index of phosphorus-clad powders testify that surface corrosion proceeds on powder particles. It is shown that the interaction of the starting PZhRV 3.342.28 and AHC 100.29 iron powders with human blood plasma is 5.8 and 7.2 times more intensive, respectively, than that for PZhRV 3.342.28 and AHC 100.29 powders clad with phosphorous. On the surface of iron powders, phosphorus interacts with blood plasma proteins to form a protective colloidal biocomplex, which increases substantially the resistance of clad powders in blood plasma. Thus, the cladding of iron powders with phosphorus enhances significantly their chemical stability both in human blood plasma and in air.

Determination of the physical and mechanical properties of iron-based powder materials produced by microwave sintering

Microwave energy is highly efficient for heating and processing different materials. In recent years, this type of heat transfer has been used in sintering process. Rapid and highly efficient heating, time and energy saving, and improved properties of sintered materials are advantages of microwave sintering. In this paper, Fe and Fe-Cu powder compact samples (cylindrical and bone shapes) are sintered both in microwave and electrical tube furnaces. The microwave generator has 2.45 GHz frequency and 1 KW power. Times are selected in the range of 5–25 min for microwave sintering and 5–40 min for electrical heating. The sintering temperature is set at 1120°C. Samples are sintered in the reducing atmosphere of 95% N2 + 5% H2 mixture. The density, hardness, and tensile strength of the samples are measured. The results are compared. The results show that the microwave-sintered materials have a finer microstructure. The microwave-sintered materials have 6–8% higher density, 5–10 HV5 higher hardness, and about 10% higher tensile strength than conventionally sintered materials.

Densification Mechanism of Warm Compaction for Iron-Based Powder Materials

An apparatus measuring changes of various forces directly and continuously was developed by a way of direct touch between powders and transmitting force component, which can be used to study forces state of powders during warm compaction. Using the apparatus, warm compaction processes of iron-based powder materials containing different lubricants at different temperatures were studied. Results show that densification of the powder materials can be divided into four stages, in which powder movement changes from robustness to weakness, while its degree of plastic deformation changes from weakness to robustness. The proposed densification mechanism may provide an insight into understanding of warm compaction process.

Fullerites and Their Derivatives: Structure, Properties, and Their Possible Formation in Iron-Based Powder Materials

Fullerites and Their Derivatives: Structure, Properties, and Their Possible Formation in Iron-Based Powder Materials

Use of commercially pure hydrogen in the annealing and sintering of iron-base powder materials

The effect of temperature (1000–1600 K) and impurities on the oxidation-reduction potential, and ability to carburize iron, of complex gas atmospheres based on commercially pure hydrogen was studied. It was shown that it is possible to utilize gas with a high concentration of methane for the annealing of iron powder. Recommendations are given for the practical use of commercially pure hydrogen to maintain a given carbon concentration in iron-base powder materials during annealing and sintering.

Effect of alloying impurities and conditions of heat treatment of iron-based powder materials and their magnetic properties

The structure of the initial iron powders, the type of alloying impurities, and the conditions of compaction and heat treatment of materials have been studied from the standpoint of their effect on the magnetic properties. Ways of enhancing the properties of magnetically-soft iron-based powder materials are recommended and methods of studying them are suggested.