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The authors of this scientific article conducted comprehensive studies aimed at identifying the influence of barium and cerium on the graphitization process and the structure of frictional gray cast iron. The purpose of this scientific article: to investigate the effect of barium and cerium, which are part of industrial foundry alloys used to modify iron-carbon alloys, on the morphology, distribution and dispersion of cementite and graphite. In the course of experimental studies, two industrial foundry alloys were used to modify cast iron. First foundry alloy: foundry alloy SiitMish-1 based on silicon and calcium. Second foundry alloy: foundry alloy TsISM; this foundry alloy is a powder alloy that contains silicon, calcium, barium, cerium. The authors of this article have established the optimal concentration of foundry alloys that provide the necessary degree of graphitization of cast iron without the formation of ledeburite. Such concentrations of foundry alloys make it possible to avoid the formation of ledeburite in the structure of cast iron and to limit the content of secondary cementite: the content of secondary cementite is optimal for gray friction cast irons, which have an austenitic structure of the metal base. The authors of this article found that the modification of cast iron with a foundry alloy TsISM, which contains barium and cerium, completely prevents the formation of graphite, which is located along the boundaries of dendrites. Graphite, which is located along the boundaries of dendrites, significantly reduces the frictional characteristics of cast iron. It was found that the modification of cast iron only with calcium does not allow avoiding the formation of graphite, which is located along the boundaries of dendrites.Modification of gray friction cast iron with a complex master alloy containing barium and cerium makes it possible to approximately three times reduce the length of graphite inclusions in comparison with cast iron modified with a silicon-calcium alloy.

This study describes the laser surface hardening process effect on microstructures produced and their wear behavior. Ductile iron samples were austempered at three different austempering temperatures: 232 °C/288 °C/398 °C respectively. Then, the laser surface hardening process was applied on each sample. Different laser gaps were designed: 1.5mm/3mm/4 mm. The microstructures were observed using optical microscopy and tribo-tests were run using a UMT-3 tribo tester. A Rockwell hardness tester was used to measure the hardness after heat-treatment. Optical microscopy and SEM were used to observe the different microstructures and their distribution on the worn surface. The results showed that the laser processing generated ledeburite, martensite, or tempered bainite microstructures. Vickers hardness tests were carried out on these microstructures. The original needle-like microstructures were observed on the samples with 4 mm laser gap but not with 1.5 mm or 3 mm laser gap. This is because part of the 4 mm laser gap is beyond the laser heat effected zone. Generally, severe ploughing wear and smearing wear were observed on the tempered bainite zone but not the bainite zone. Debris was generated during the tribo-tests and led to three body abrasive wear which not only resulted in higher wear loss, but also polished the worn surface.

The present research studied the combined effects of quench-tempering and laser surface hardening treatments on wear behavior of gray cast iron, and compared results with conventional austempered gray cast iron. Four tempering temperatures of 316 °C (600 °F), 399 °C (750 °F), 482 °C (900 °F) or 552 °C (1025 °F) with a constant holding time of 60 min and four austempering temperatures of 232 °C (450 °F), 288 °C (550 °F), 343 °C (650 °F) or 399 °C (750 °F) with a constant holding time of 120 min were utilized in the heat treatment design. The wear tests were carried out on a universal mechanical tribometer with a reciprocating ball-on-plate sliding configuration. Also, the microstructure, micro-hardness profiles and worn tracks were examined. Through this work, it was found that three zones existed under the laser hardened surface. Zone 1 was the laser hardened zone containing ledeburite with hardness of approximately 68HRC. Zone 2 was the heat affected zone containing the martensite with hardness of approximately 66HRC. Zone 3 was the substrate with hardness ranging from 42.1 to 24.8HRC. In the sliding wear tests, the quench-tempering treatment only resulted in higher wear resistance of gray cast iron when compared with untreated specimens, but lower wear resistance than that of austempered gray cast iron under similar macro-hardness. The wear performance of the quench-tempered gray cast iron was enhanced after receiving the laser surface hardening treatment. Finally, the laser hardened and quench-tempered gray cast iron with tempering temperature of 552 °C showed similar mass loss due to wear as austempered gray cast iron with an austempering temperature of 232 °C. By observing the worn surfaces, the laser hardened regions could effectively inhibit the formation and propagation of cracks developed within the substrate regions. In addition, the substrate with low hardness in laser hardened and quench-tempered gray cast iron may provide enhanced ductility and toughness for gray cast iron engineering components. The results obtained in this research have significant value in selecting the optimum heat treatment process for laser hardened gray cast iron components.

Numerical relation of cast iron chill characteristics (distance of chilled layer H and volume quota of ledeburite in it Qл ) with its carbon equivalent СE was investigared. This data helps to prognosticate with high probability the evolution of the surface chilled layer forming at the production of castings with different thickness from cast iron of various chemical compositions. The object of study is the unalloyed induction melted cast iron with eight variants of chemical composition with carbon equivalent from 3.30 up to 5.53 %. From these cast irons we made the step-by-step castings with steps sizes of 10×60 mm and thickness of 5, 10, 20 and 40 mm. The distance (depth) of chilled layer was measured at the fractures of the castings and gaged on thickness of full chill zone. Ledeburite volume quota was detected by metallographic method using “Nexsys-Image expert pro 3” computer program. According to experimental data, when the casting thickness is 5 and 10 mm the through (at all thickness) full chill is formed at carbon equivalent ≤ 4.08 % and ≤ 3.67 % consequently. At the castings with 20 and 40 mm thickness the zone of full chill is absent, and in this case the chilled layer depth increases with a decrease of carbon equivalent and decreases with an increase of casting’s thickness X. The dependence of H from СЕ have the exponential character and can be described by the equation H = A exp (–k СE ), where A and k are empirical coefficients. Ledeburite volume quota near the contact surface of casting with chiller is near 90 %, but with an increase in the distance from the surface it decreases with different intensity depending on changes of carbon equivalent and casting’s thickness. By mathematical processing of the experimental data received for the distance of 5 mm from the contact surface of the casting with chiller, we have detected that numerical re lation Qл in casting chilled layer with value of CE can be described by the exponential dependence

The present study mainly investigated the phase transformation and wear performance of laser hardened austempered gray cast iron specimens. Ball-on-Plate reciprocating sliding wear tests with PAO4 base oil were carried out on untreated, quench-tempered, austempered, laser hardened austempered gray cast iron specimens. Micro hardness profiles and worn surfaces were analyzed for specific wear mechanisms. It was found that four different zones were formed beneath the laser hardened surface including laser hardened zone (Ledeburite, ≈67HRC), upper heat affected zone (Martensite, ≈69HRC), lower heat affected zone (Tempered Ausferrite, ≈36HRC) and substrate (Ausferrite, ≈39HRC). In the sliding wear tests, the laser hardened austempered gray cast iron specimens showed higher wear resistance than others, which could be associated with the benefits of ausferritic structure with high fracture toughness and laser hardened regions with high hardness. By observing the worn surface, grooves and micro-sized material removal occurred within the substrate. The surface of the substrate ploughed by the asperities of the ball and hard wear debris stopped on the edge of the laser hardened regions since ledeburite and martensite had high hardness and abrasive wear resistance. However, some micro-cracks and spalls were developed within the laser hardened zone. The results obtained from this study could be used as reference in future research and applications of laser hardened austempered gray cast iron. Keywords: Gray cast iron, Austempering, Laser hardening, Sliding wear resistance

The numerical relation of cast iron chill characteristics (distance of chilled layer H and volume quota of ledeburite in it Ql) with its carbon equivalent СE was investigated. This data helps forecast the evolution of the surface chilled layer forming at the casting production with different thickness from cast iron of various chemical compositions. The study focuses on the unalloyed induction-melted cast iron with eight chemical-composition variants with carbon equivalent from 3.30 up to 5.53%. From these cast irons, step-by-step castings were made with steps sizes of 10 × 60 mm and thickness of 5, 10, 20, and 40 mm. The chilled-layer distance (depth) was measured at the casting fractures and gaged on thickness of full chill zone. Ledeburite volume quota was detected by a metallographic method using the “Nexsys-Image expert pro 3” computer program. According to experimental data, when the casting thickness is 5 and 10 mm, the through (at all thickness) full chill is formed at a carbon equivalent ≤4.08% and ≤3.67%, consequently. At the castings with 20- and 40-mm thickness, the zone of full chill is absent. In this case, the chilled layer depth increases with a decrease of carbon equivalent and decreases with an increase of casting’s thickness X. The dependence of H from CE have the exponential character and can be described by the equation H = Aexp(–kCE), where A and k are empirical coefficients. Ledeburite volume quota near the contact casting surface with chiller is near 90%, but it decreases with different intensity depending on changes of carbon equivalent and casting’s thickness with an increase in the distance from the surface. By mathematical processing of the experimental data received for the 5-mm distance from the contact surface of the casting with chiller, a numerical relation Ql in casting chilled layer with value of CE can be described by the exponential dependence: Ql = 1000(7/(X + 10))exp(–CE).

Electron beam remelting (EBR) of cast irons is an established procedure for generating hard and wear-resistant functional surfaces. Due to process-specific rapid cooling after the surface melting of cast iron, solidification occurs according to the metastable system, and a ledeburitic surface-layer microstructure is generated (eutectic carbide + austenite + pearlite). When a subsequent nitriding process is added, carbide morphology and distribution have a decisive influence on the formation of nitride layers. In this analysis, investigations on the influence of different EB process parameters are presented and discussed, such as beam current and acceleration voltage, as well as the effect of focus position on the ledeburite morphology, the layer thickness and surface deformation after the EBR process. Cast iron with globular graphite was used as the base material for the present investigations. The classification of the ledeburite was carried out by examining polished metallographic cross-sections for the determination of the EBR layer thickness, the layer hardness and the secondary dendrite arm spacing. The latter factor also allowed conclusions to be reached regarding the rates of cooling. Furthermore, the local distribution of C and Si in the microstructural constituents of the ledeburitic surface layer was essential in understanding the diffusion processes and phase transformations during the subsequent nitriding process. For this reason, EBR layers with defined coarse and fine ledeburitic carbides were generated and characterized in detail using EDX surface scans. The influence of the local microstructure, the carbide morphology and the element distributions in the EBR layer on the formation and properties of the nitride layers are discussed in light of initial nitriding experiments. Based on these findings, further optimization of the surface layer is possible with respect to the selection of parameters for both the EBR and nitriding processes.

In metallurgical practice, solidification of metallic materials usually starts by heterogeneous nucleation. Homogeneous nucleation can occur in deeply undercooled melts. Gas atomization represents one of the methods which can be used to achieve deep melt undercooling. In the gas atomization process, a certain number of the melt droplets can even reach hypercooling, which may provide suitable conditions for homogeneous nucleation in such particles. The paper presents an original approach to the quantitative analysis of the number of crystallization nuclei originated in deeply undercooled melt by the process of homogeneous nucleation using the particles of rapidly solidified (RS) powder of high alloyed Cr-Mo-V tool steel of a ledeburite type prepared by nitrogen gas atomization. For microstructural analysis, RS powder particles were sieved into six standard-sized granulometric fractions ranging from 50 μm to 125 μm. The maximum volumetric density of homogeneously formed crystallization nuclei was identified using the methods quantitative stereology in the granulometric fraction of RS powder from 56 μm to 63 μm with the value approximately 1.5 × 106 mm−3.

In this study, the effect of microstructure evolution, especially that involving the proeutectoid carbides, on hardness distribution of ledeburite steel containing 8% chromium content was investigated at different cooling rates after hot deformation. The continuous cooling transformation was carried out using a fully automatic transformation measuring apparatus under cooling rates in the range of 0.03-80 °C/s. The transformation temperatures, Ac1, Ac3 and Ms, were measured by dilatometry. A nanoindentation test was employed to evaluate the mechanical properties of the cooled specimens. The evolution of microstructure indicated that the proportion trend of the precipitated carbides was dependent on the cooling rates. In addition, a mixture of pearlite and proeutectoid carbides was observed under slow cooling rates in the range of 0.03-0.2 °C/s, for which only a martensite transformation took place in austenite, and the proeutectoid carbides precipitated negligibly at cooling rates greater than or equal to 10 °C/s. The results also showed that the nanohardness significantly decreased and then slowly increased to a stable value with increasing cooling rates, which was similar to the content trend of the carbides that precipitated during the cooling process.

F.M. Shirzadov1, fashirzadov@beu.edu.az, R.Y. Dadashov2, mr_dadashov@mail.ru. 1Baku Engineering University, Baku, Republic of Azerbaijan 2Azerbaijan Technical University, Baku, Republic of Azerbaijan Ширзадов Фархад Махаммад оглу, доктор философии по технике, доцент, заведующий кафедрой «Механическая инженерия», Бакинский инженерный университет, г. Баку, Республика Азербайджан, fashirzadov@beu.edu.az. Дадашов Рамиль Енгибар оглы, ассистент кафедры «Технология машиностроения», Азербайджанский технический университет, г. Баку, Республика Азербайджан, mr_dadashov@mail.ru. Continuous requirements for improving the quality of machines requires new investigation to constantly increase the production performance of parts. In this article, the surface of the cast iron EN-GJV-400 was remelted and modified via TIG (Tungsten-Inert-Gas) welding separately and simultaneously under high frequency magnetic field, as well as the microstructure and hardness of the specimens were compared. It has been found that with the plasma treating of the surface under high frequency magnetic field the mechanical and tribological properties of the specimens have been improved. The hardness of the specimens from the cast iron EN-GJV-400 was increased after the surface remelting with high frequency and low energetic magnetic field. The microstructures of the modified surfaces through the conventional TIG and high frequency magnetic field were also not same. The reason was that the magnetic energy in the molten material in the latter method caused additional temperature in weld pool as well as the rotation of the it in the direction of the magnetic induction vector. The size of the grains has been increased via the additional heating effect and at the same time the dendrite branches have been cut to the smaller parts. The technology can be applied for the increasing the Hertzian contact pressure, tribological properties of surfaces and for the alloying and shaping processes considering the magnetic force on the molten material. Постоянное повышение требований к качеству машин требует новых исследований и разработок в области проектирования новых технологических процессов и прогрессивных методов обработки для непрерывного повышения производительности деталей. В качестве одного из подобных вопросов в этой статье рассматривается проблема напыления различных износостойких материалов на поверхность распределительного вала с целью повышения его коррозионной и износостойкости. Поверхность чугуна марки EN-GJV-400 была переплавлена и модифицирована сваркой ВИГ (вольфрамовый инертный газ) отдельно и одновременно в высокочастотном магнитном поле, а также сравнивается микроструктура и твёрдость образцов. При этом установлено, что при плазменной обработке поверхности в высокочастотном магнитном поле механические и трибологические свойства испытуемых образцов улучшаются. Твёрдость образцов из чугуна марки EN-GJV-400 была существенно увеличена после поверхностного переплава высокочастотным и низкоэнергетическим магнитным полем. Микроструктура поверхностей, модифицированных с помощью обычного ВИГ и высокочастотного магнитного поля, также не была одинаковой. Причина этого заключалась в том, что магнитная энергия в расплавленном материале при последнем методе обработки вызывала дополнительную температуру в сварочной ванне, а также его вращение в направлении вектора магнитной индукции. Размер зёрен был увеличен за счёт дополнительного нагрева, и в то же время ветви дендритов были разрезаны на более мелкие части. Данная технология может применяться для увеличения контактного давления Герца, трибологических свойств поверхностей, в также для процессов легирования и формования с учётом магнитной силы, действующей на расплавленный материал. The welding processes and the metallographic analyses have been carried out at the Berlin Technical University, in the department of “Joining and surfacing technology”. Special Thanks to professor Lutz Dorn for the support during the experiments.

The current research studied the effects of laser surface hardening treatment on the phase transformation and wear properties of gray cast irons heat treated by austempering or quench-tempering, respectively. Three austempering temperatures of 232 &deg, C, 288 &deg, C, and 343 &deg, C with a constant holding duration of 120 min and three tempering temperatures of 316 &deg, C, 399 &deg, C, and 482 &deg, C with a constant holding duration of 60 min were utilized to prepare austempered and quench-tempered gray cast iron specimens with equivalent macro-hardness values. A ball-on-flat reciprocating wear test configuration was used to investigate the wear resistance of austempered and quench-tempered gray cast iron specimens before and after applying laser surface-hardening treatment. The phase transformation, hardness, mass loss, and worn surfaces were evaluated. There were four zones in the matrix of the laser-hardened austempered gray cast iron. Zone 1 contained ledeburite without the presence of graphite flakes. Zone 2 contained martensite and had a high hardness, which was greater than 67 HRC. Zone 4 was the substrate containing the acicular ferrite and carbon-saturated austenite with a hardness of 41&ndash, 27 HRC. In Zone 3, the substrate was tempered by the low thermal radiation. For the laser-hardened quench-tempered gray cast iron specimens, three zones were observed beneath the laser-hardened surface. Zone 1 also contained ledeburite, and Zone 2 was full martensite. Zone 3 was the substrate containing the tempered martensite. The tempered martensite became coarse with increasing tempering temperature due to the decomposition of the as-quenched martensite and precipitation of cementite particles. In the wear tests, the gray cast iron specimens without heat treatment had the highest wear loss. The wear performance was improved by applying quench-tempering heat treatment and further enhanced by applying austempering heat treatment. Austempered gray cast iron specimens had lower mass loss than the quench-tempered gray cast iron specimens, which was attributed to the high fracture toughness of acicular ferrite and stable austenite. After utilizing the laser surface hardening treatment, both austempered and quench-tempered gray cast iron specimens had decreased wear loss due to the high surface protection provided by the ledeburitic and martensitic structures with high hardness. In the worn surfaces, it was found that cracks were the dominant wear mechanism. The results of this work have significant value in the future applications of gray cast iron engineering components and provide valuable references for future studies on laser-hardened gray cast iron.

The thermal conditions in the molten pool during the laser surface melting of ductile cast iron EN-GJS-700-2 were estimated by using infrared thermography and thermocouple measurements. The thermal data were then correlated with the microstructure of the melted zone. Additionally, the thermodynamic calculations of a Fe-C-Si alloy system were performed to predict the solidification path of the melted zone. It was found that increasing the cooling rate during solidification of the refined ledeburite eutectic but also suppressed the martensitic transformation. A continuous network of plate-like secondary cementite precipitates and nanometric spherical precipitates of tertiary cementite were observed in regions of primary and eutectic austenite. The solidification of the melted zone terminated with the Liquid &rarr, &gamma, Fe + Fe3C + Fe8Si2C reaction. The hardness of the melted zone was affected by both the fraction of the retained austenite and the morphology of the ledeburite eutectic.

Manual arc-welded hardfacings are widely used for the protection of new or the restoration of worn parts in agriculture, forestry, and mining applications. A study was conducted to investigate the effect of electrode covering composition on the microstructure, wear (low, average stress abrasion, erosion at 30, 50, and 80 m s&minus, 1), and economic feasibility of Fe&ndash, C&ndash, Cr manual arc-welded hardfacings. Hardfacings were produced with the carbon and chrome contents varied in the ranges of 0.87&ndash, 2.95 and 1.3&ndash, 33.2 wt.%, respectively. The major phases composing the microstructures of the hardfacings were austenite, perlite, ledeburite, and various carbides, including eutectic M7C3. Technical and economic analyses were performed to assess the economic feasibility of hardfacings and reference wear-resistant steel Hardox 400. A wear and economic feasibility map was created to specify various types and facilitate the selection of optimal hardfacings for specific conditions. The produced Fe&ndash, Cr coatings were the most effective in low-stress abrasive conditions (up to 7.8 times greater than Hardox 400) and quite effective in erosive conditions (up to 2.9 times greater than Hardox 400).

Thermo-mechanical processing is performed to engineer the microstructure comprising of nano-spheroidized cementites in ultrafine-grained ferrite in high carbon steel to enhance strength-ductility relationship. Spheroidization is achieved through heavy warm rolling (4-passes of 30% reduction at 823 K and 873 K) followed by extended annealing (1 h and 2 h) at the respective deformation temperatures. The influence of annealing temperature and time on the evolution of carbide precipitates, the extent of spheroidization and ferrite softening is investigated employing scanning electron microscopy, electron back scatter diffraction and transmission electron microscopy techniques. A near-complete spheroidization is achieved following heavy warm rolling and subsequent annealing for 2 h at 873 K (WR873K-2H). Although ferrite grain size increases with time and temperature of annealing, it ceases to cross the ultrafine regime (470–750 nm) due to the pinning effect of the carbides that restricts the migration of ferrite grain boundaries. A simultaneous increase in strength and ductility is achieved following heavy warm rolling and subsequent annealing for 1 to 2 h at 873 K. Maximum elongation (~30%) is achieved in the WR873-2H specimen in contrast to ~20% elongation in as-received specimen. Such an increase in ductility is due to the near-complete spheroidization as revealed by the ductile mode of fracture in fractrographic analysis. Keywords: High carbon steel, Heavy warm deformation, Ultrafine grains, Spheroidized cementite, Tensile properties

In this work, a comparative analysis of two iron bullets found in The Royal Ammunition Factory of Eugi in Navarra (Spain) was performed. Both bullets presented a spherical shape with a relatively good state of preservation, belonging to the last years of the factory production (1766-1850). Several techniques such as microhardness, X-ray fluorescence (XRF), light (LM) and scanning electron microscopy (SEM), optical mission spectroscopy (OES) and energy dispersive X-ray spectroscopy (EDX) analysis were used in order to identify the manufacturing process of the two bullets. The analyses of the microstructures carried out by LM and SEM showed that one bullet was composed of white cast iron with a pearlitic matrix, steadite and graphite; while the other was composed of grey cast iron with a pearlitic matrix, graphite and a low amount of steadite. The chemical analysis of the bullets carried out by OES indicated significant differences in the amount of silicon and phosphorous. The variation in silicon content could suggest that the foundry temperature under oxidizing environment varied during the casting. The SEM and EDX analyses showed both bullets had manganese sulphide inclusions but only one of the bullets exhibited titanium and vanadium inclusions. The microhardness analyses carried out revealed Vickers hardness differences along the diameter. This variation could be explained by the differences in cooling rate along the diameter. Based on the physical characteristics of the bullets and on the obtained results, it can be concluded that one of the bullets could have been used as a grapeshot projectile and the other one as a bullet for ribauldequins. In addition, calcined ore and slag found in this factory were also analysed. The variation found in their chemical composition corroborated that the foundry temperature employed during the manufacturing process was low, the slag being enriched in Si, Al and Mn elements.

A graded high-vanadium alloy composite coating was synthesized from premixed powders (V, Cr, Ti, Mo, Nb) on ductile iron (DI) substrate via atmospheric plasma arc surface alloying process. The resulted cross-section microstructure is divided into three distinct zones: upper alloyed zone (AZ) rich with spherical primary carbides, middle melted zone (MZ) with fine white iron structure and lower heat affected zone (HAZ). Spherical or bulk-like primary carbides with diameter < 1 μmin the AZ are formed via in-situ reactions between alloy powders and graphite in DI. Microstructural characterizations indicate that the carbides are primarily MC-type (M=V, Ti, Nb) carbides combined with mixed hardphases such as M 2C, M7C3, M23C6, and martensite. Disperse distribution of spherical, submicron-sized metal carbides in an austenite/ledeburite matrix render the graded coating hard-yet-tough. The maximum microhardness of the upper alloyed zone is 950 HV0.2, which is five times that of the substrate. Significant plastic deformation with no cracking in the micro-indentations points to a high toughness. The graded high-vanadium alloy composite coating exhibits superior tribological performance in comparison to Mn13 steel and plasma transferred arc remelted DI.

A novel high-vanadium based hard composite coating was synthesized from premixed powders (V, Cr, Mo, Ti, Nb) on ductile iron (DI) substrate via atmospheric plasma beam surface alloying process. The graded coating can be divided into three distinct zones: upper alloyed zone (AZ) rich with spherical primary and eutectic submicron carbides, middle melted zone (MZ) with fine white iron structure embedded with high-carbon martensite and lower heat affected zone (HAZ) where martensite/ledeburite double shells were substantially formed. Spherical or bulk-like primary carbides with diameter

In order to determine the optimum geometry of the ingot mold format (the format of ingot mold with a diameter per height ratio H / D It was considered 205Cr115 steel type (according with , STAS 3611 - Romanian stardandization) and known also as X210Cr12 steel type (according with European standard). It has been considered an element of volume of coordinates x, y, z in the solidifying ingot and have made the following assumptions: (i) the equilibrium distribution ratio K, is applied to the solid-liquid interface; (ii) solid diffusion is negligible during solidification; and (iii) the solid density is constant during solidification. In carrying out the simulation of segregation mechanisms are resolved heat transfer equation, that simulating the solidification process and are are solved the interdendritic fluid equation of motion.

Based on the chemical composition requirements and enhancing the utilization value of the products, this work put forward a direct preparation method for low Ni-Cr alloy cast iron from red mud and laterite nickel ore by high-temperature carbothermal reduction smelting and refining. X-ray fluorescence (XRF), optical emission spectrometer (OES), scanning electron microscopy (SEM) attached with energy dispersive spectroscopy (EDS) analysis, hardness and polarization tests were used in the characterization process. The results show that low Ni-Cr alloy cast irons contain 1.50–2.00 wt.% Ni and 0.70–0.80 wt.% Cr have been prepared as the mass ratios of red mud to laterite nickel ore vary from 80:20 to 70:30, in which the recovery were 93.70% for Fe and 99.83% for Ni, respectively. The alloy cast iron was consisted of ledeburite and cementite matrix with evenly distributed Ni and Cr elements and block and flake graphite precipitated phase. With the increasing of Ni and Cr contents, the hardness and corrosion resistance of the alloy cast irons improved. Keywords: Low Ni-Cr alloy cast iron, Red mud, Laterite nickel ore, Electric arc furnace

In recent years, application of high duration steels, first of all, martensitic and bainitic steels used in manufacturing of parts and structures of crucial function has increased significantly. It is possible to achieve a high duration state by means of effective deformation hardening of steels of various classes at rational use. Understanding of quantitative laws and mechanisms of deformation hardening of steels of different structural classes under active plastic deformation is necessary in terms of targeted formation of structure-phase states and mechanical properties of material. In this work, comparative analysis of structure evolution, phase composition and state of defective substructure of steel with martensitic and bainitic structures under active plastic deformation prior to fracture was performed using transmission electron diffraction microscopy. It was shown that after austenitization at temperature of 950 °C (1.5 hours) and subsequent quenching in oil of 38CrNi3MoV steel and normalization of 30Cr2Ni2MoV steel, a multiphase structure (α phase, γ phase, cementite) is formed, based on martensite of packet morphology (38CrNi3MoV steel) and lower bainite (30Cr2Ni2MoV steel). Obtained quantitative regularities of changes in parameters of steel structure in process of plastic deformation made it possible to carry out studies aimed at analyzing the distribution of carbon atoms in structure of deformed steel. Localization of carbon atoms in martensite structure (38CrNi3MoV hardened steel) and bainite (30Cr2Ni2MoV normalized steel) are revealed. It was established that steels deformation is accompanied by destruction of cementite particles. For hardened martensitic steel, with an increase in degree of deformation, the total number of carbon atoms located in solid solution based on α- and γ-iron decreases, and on structural defects – increases. Redistribution of carbon atoms in steel with bainitic structure with increase in deformation degree consists in growth of number carbon atoms located in α-iron, in defects of the crystal structure, and in intraphase boundaries cementite and its’ subsequent decrease in cementite particles within bainite plates and in γ-iron.

The variety of requirements for friction pairs requires the development of different technologies for the production of tribological materials with reference to the operation modes. Composite materials obtained by the casting technology have been successfully applied for the normalization of the thermomechanical state of the steam turbines. These composites consist of the matrix based on copper alloys reinforced with cast iron granules. Because the structure and properties of cast iron are determined by the conditions of their production studies have been conducted on determination of preparation conditions on grain structure and properties of the synthesized composite material. Using an upgraded unit for production of granules technological regimes were determined providing narrow fractional composition. It has been found that granules formed are characterized with typical microstructure of white cast iron containing perlite and ledeburite. Microhardness of pilot cast iron granules is characterized by high values (from 7450 up to 9450 MPa) and depends on the size of the fraction. Composite materials obtained using experimental granules had a microhardness of the reinforcing cast iron granules about 3500 MPa, and a bronze matrix – 1220 MPa, which is higher than the hardness of the composite material obtained by using the annealed DCL-1granules (2250 MPa). Metal base of experimental granules in the composite material has the structure of perlitic ductile iron with inclusions of ferrite not exceeding 10–15% and set around a flocculent graphite. As a result, the increase of physical-mechanical properties of finished products made of composite material is observed.

It is found that the deformation of white cast iron under forging production is only possible with a minimum number of permanent impurities. The developed modes of high-temperature intermediate annealing facilitate the deformation of the forging under normal production conditions. It is shown that in the process of isothermal annealing of white cast iron begins the process of disintegration of ledeburite in the more stable eutectic carbides, providing technological plasticity for subsequent forging. The installed influence of the purity of white cast iron on the morphology of the excess carbides and their ability to divide. Studies the morphology of the excess eutectic carbides after melting, pre-annealing and after deformation forging. Discovered that after severe plastic deformation the structure of white cast iron becomes more stable, due to the appearance of eutectic carbides. It was determined that the deformed structure of white iron, because of its lack ledeburite component, was more identical with the structure of the alloy ledeburite steels. The data obtained can be used for making Damascus bladed weapons products, experiencing shock-variables loads.

The main advantage of welding cast iron is to recover parts by repairing defects induced by casting processes (porosities, etc.), before they enter their working cycle, as well as repair cracks or fractures when already in service. This method contributes to decreased foundry industrial waste and avoids the additional energy costs of their immediate recycling. Therefore, it is necessary to have a welded joint with similar or better characteristics than the parent material. The major problem of welding cast iron is that this material has a very high content of carbon in comparison to steel (&asymp, 3%). Therefore, when it is heated by the very high temperatures from arc welding and during its process of solidification, very hard and brittle phases originate, known as ledeburite and martensite, and appear in the partially melted zone and in the heat-affected zone. Eventually, this problem can be solved by implementing heat treatments such as preheat or post weld heat treatments under specific parameters. Therefore, in this study, the aim is to collect data about the effects of heat treatments performed at different temperatures on welded joints of high strength ductile cast iron (SiboDur&reg, 450), and to evaluate the effects of heat treatments performed at diverse temperatures on welded joints of this type of material, using Shield Metal Arc Welding and nickel electrodes. Mechanical strength, hardness, and microstructure were analyzed, showing that the best mechanical strength in the joint (380 MPa) was obtained using two passes of E C Ni-Cl (ISO EN 1071:2015) filler metal and post weld heat treatments (PWHT) of 400 &deg, C for two hours.

Nodular cast iron shows poor weldability due to obvious crack tendency caused by chilled structure in interface region during welding and cladding process. However, chilled structure could be eliminated by controlling interface heat input during laser cladding process. In this paper, brazing interface characteristic with no chilled structure could be obtained by controlling the heat input of the interface, and the results showed that the brazing interface illustrated higher strength compared with the chilled structure interface. The results illustrated that the tensile strength of specimens with brazing and intermittent chilled structure characteristic could reach 564 MPa. However, tensile strength of specimens with continuous chilled structure characteristic was lower than 353 MPa. Cracks formed in the interface zone and extended to the ledeburite region. FEM method with the help of ANSYS software was adopted to determine the thermal cycles of the interface region during the cladding process, and the mechanism of the interface behavior was studied.

The paper presents research results of the influence of heat input into high carbon rail steel during cutting processes on microstructure transformation and cracking. The massive block of steel prepared for rail rolling processes was cut and examined by nondestructive magnetic testing and destructive testing by microscopic examination and hardness measurements. The results show unfavorable microstructure changes where pearlite and transformed ledeburite were obtained. The effects of the presence of such microstructures are high hardness near to cutting surfaces (above 800 HV) and microcracks which grow into low hardness block cores during rolling and rail shaping.

A model for estimating the upper to lower bainite transition has been developed for the iron–carbon–manganese–chromium–silicon alloy system by comparing the time required to decarburise a supersaturated bainitic ferrite platelet and that needed for the start of cementite precipitation in the ferrite. The problem is treated as a competition between the decarburisation time and the kinetics of cementite precipitation. Lower bainite is induced when the latter process is faster. The time for forming a volume fraction of 0.01 of the equilibrium amount of cementite is taken as the precipitation start time. The model was calibrated using experimental data from the iron–carbon system, and verified with the iron–carbon–manganese–molybdenum system and an experimental steel currently being developed for high-strength applications.

A Cr-Ni-Mo overlayer was deposited on the surface of compacted graphite iron (CGI) by the plasma transferred arc (PTA) alloying technique. The microstructure of Cr-Ni-Mo overlayer was characterized by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), and X-ray diffractometer (XRD). Results show that the cross-section consists of four regions: alloying zone (AZ), molten zone (MZ), heat affected zone (HAZ), and the substrate (SUB). The microstructure of AZ mainly consists of cellular γ-(Fe, Ni) solid solution, residual austenite and a network of eutectic Cr7C3 carbide while the MZ area has a typical feature of white cast iron (M3C-type cementite). The martensite/ledeburite double shells are observed in the HAZ. With decreasing the concentration of Cr-Ni-Mo alloys, the fracture mode changes from ductile in the AZ to brittle in the MZ. The maximum hardness of the AZ (450 HV0.2) is lower than that of the MZ (800 HV0.2). The eutectic M3C and M7C3 carbides increase the microhardness, while the austenite decreases that of the AZ.

International audience; The austenitization from a spheroidized microstructure during intercritical annealing was studied in a Fe-0.1C-3.5Mn alloy. The austenite grains preferentially nucleate and grow from intergranular cementite. The nucleation at intragranular cementite is significantly retarded or even suppressed. The DICTRA software, assuming local equilibrium conditions, was used to simulate the austenite growth kinetics at various temperatures and for analyzing the austenite growth mechanism. The results indicate that both the mode and the kinetics of austenite growth strongly depend on cementite composition. With sufficiently high cementite Mn content, the austenite growth is essentially composed of two stages, involving the partitioning growth controlled by Mn diffusion inside ferrite, followed by a stage controlled by Mn diffusion within austenite for final equilibration. The partitioning growth results in a homogeneous distribution of carbon within austenite, which is supported by NanoSIMS carbon mapping.

Directional solidification of the Fe - 4,3 wt % C alloy was performed with the pulling rate equal to v=83 μm/s. Sample was frozen during solidification to reveal the shape of the solid/liquid interface. Structures eutectic pyramid and spherolitic eutectic were observed. The solidification front of ledeburite eutectic was revealed. The leading phase was identified and defined.

Purpose . This research is aimed to obtain the regression dependence of the machinability on the chemical composition of pig iron (C, Cr, Mn and Ni) in cast state. Methodology . The method of active experiment planning was used to build a mathematical model. Cast irons of composition 1.09…3.91 % С; 11.43…25.57 % Cr; 0.6…5.4 % Mn; 0.19…3.01 % Ni were studied. Cutting tools with plates 10х10 mm out of ВК8 according to State Standard 19051-80 were used for turning. Cutting modes: cutting depth – 0.8 mm, longitudinal feed – 0.15 mm/rot., spindle’s rotation frequency during turning – 200…360 rot./min. Lubricating and cooling liquids were not applied. Evaluation of iron workability was produced by determining the linear tool flank wear per unit length of the cutting path. Findings . Mathematically probabilistic equation of the regression dependence of the cutting tool’s wear on the C, Cr, Mn and Ni content in the machined cast iron were obtained. It was established that with the increase of Cr content in the cast iron to 14.8 % the cutting tool’s wear decreased as a result of formation of carbide eutectic which destroyed the doped ledeburite continuous frame. Further increase of chromium content promoted appearing of chromic carbides with high microhardness which considerably increased the tool’s wear. The conducted research shown that the minimum cutting tool’s wear 0,18 mkm/m was observed during the machining of cast iron containing: 1.09 % C, 14.8 % Cr, 2.3 % Mn and 1.2 % Ni; and the maximum wear is 48,96 mkm/m – when the content was: 3.91 % C, 11.43 % Cr, 5.4 % Mn and 0.19 % Ni. The tool’s wear reached 47.61 mkm/m during the treatment of cast iron containing 3.91 % C, 25.57 % Cr, 5.4 % Mn and 0.19 % Ni. Originality . Mathematically probabilistic model of the dependence of the cutting tool’s wear on the C, Cr, Mn and Ni content in the machined cast iron has been elaborated by the author. Practical value . The model allows optimizing the compositions of wear-resistant cast irons for castings which require the significant mechanical machining. Cast irons compositions were recommended for different exploitation conditions.

It is shown that the excess carbide phase in Wootz is of an unusual nature origin that differs from the excess phase of secondary cementite, ledeburite and primary cementite in iron-carbon alloys. It is revealed that the morphological features of excess cementite in Wootz lie in the abnormal size of excess carbides having the shape of irregular prisms. It is discovered that the faceted angular carbides are formed within the original of metastable ledeburite, so they are called “eutectic carbides”. It was found that angular eutectic carbides in the Wootz formed during long isothermal soaking at the annealing and subsequent deformation of ledeburite structures. It is revealed that carbon takes up 2.25% in Wootz (in the region of white cast iron), while none in its structure of crushed ledeburite. It is shown that the pattern of carbide heterogeneity consists entirely of angular eutectic carbides having an irregular trigonal-prismatic morphology. It is shown that Wootz (Damascus steel) is non-alloy tool steel of ledeburite class, similar with structural characteristics of die steel of ledeburite class and high-speed steel, differing from them only in the nature of excess carbide phase.

The addition of a third element to hypereutectoid Fe-C alloys may cause inclusions of a minor constituent in the precipitate of cementite from austenite even if the initial austenite is supersatura ...

Obtaining of layered excess cementite distribution in hypereutectoid steel by deformation in the intercritical temperature range is considered. The initial state prior to deformation is cast steel and heat treated cast steel. It has been revealed that in the cast state excess cementite can be represented in the form of plates in a volume of austenite grains, in the form of network along austenite grain boundaries, in the form of liquation-induced aggregates (tangles) in the interaxial intervals of austenite dendrites. Typically a cast structure contains all of these morphologies. Sometimes excess cementite can be represented as primary cementite in nonequilibrium ledeburite. It has been found that a reliable method to obtain the layered structure without the presence of coarse particles of cementite is deformation in the intercritical temperature range of hypereutectoid carbon steel with an initial Widmanstatten morphology of excess carbide phase.

In this work, we report a high-vanadium hierarchical coating prepared on the surface of nodular cast iron substrate by a low-cost plasma transferred arc (PTA) surface alloying process. The coating consists of a graded layer with an alloyed zone (AZ) rich in submicron sized granular (V-Ti-Nb-Cr-Mo) composite carbides on top of intermediate melted zone characterized by refined ledeburite and martensite. The dense spherical particles in the AZ are FCC structured MC-type (M = V, Ti and Nb) carbides which tend to aggregate while M7C3 and M2C carbides nucleate on MC. The super-lattice V8C7 maintains its cube-on-cube orientation relationship with TiC. The hardness of the AZ is 9.6 +/- 1.0 GPa, similar to 4 times that of the substrate. Nano- and micro-indentations point at a superior strength-toughness in the AZ, where cracks are deflected and bridged by the spherical MC carbides in a compressive residue stress state. The fracture mode appears to be rather ductile in the AZ whereas brittle failure appears in both the melted zone and substrate. TEM and EDS results confirm that such a micro architecture design, assisted by the rapid solidification rate of the PTA process, concurrently activates various strengthening micromechanisms including the precipitation hardening and grain refinement.