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Thermodynamic analysis of phase transformations of the multicomponent Fe–Ni–Cr–Cu–Si–C system is performed. It is of interest for the advanced metallothermic preparation technology of a wear-resistant alloy. To estimate the phase composition and structure of the alloy, computer calculations of characteristic vertical sections of the phase diagram are performed using the Thermo-Calc (TCW5 version) software; they are based on a digital simulation of phase equilibria using the CALPHAD method and the TTFe-Thermotech Fe-based Alloys Database, which includes data on chemical elements and is intended for the calculations of stable and metastable phases in multicomponent alloys. The phase transformations are considered at temperatures of 300 to 1400°C, a step of 100°C, and variable contents of Ni, Cr, Cu, Si, and C alloying elements. Vertical sections of the Fe–Ni–Cr–Cu–Si–C phase diagram are calculated, and the critical temperatures of the phase transformations of the alloy and chemical compositions of the formed phases (α, β, β2, γ, γ2, L) are determined. The thermodynamic simulation results show that, when an Fe-based alloy is alloyed, its microstructure becomes more complex and its phase composition changes; this situation takes place during gas-plasma facing. To study solidification to obtain quantitative information about the solidification stages of an alloy, the critical temperatures separating the stages, the composition and amount of precipitated phases, and the effect of temperature are determined. The temperature dependence of melt solidification exhibits a transition of nonequilibrium melt solidification to an equilibrium solidification stage at 950°C; this assumes a fine-grained structure of the coating. Thermodynamic analysis allows us to predict a ferrite–martensite structure of the coating with ledeburite inclusions during the preparation of a wear-resistant coating by metallothermic technology. The constructed vertical sections show that complete dissolution of all components in liquid occurs at ~1400°C.

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.

The effect of heat treatment parameters (the temperature of 850 – 930°C and the cooling rate of 1 – 20 K/min) on the microstructure and mechanical properties of carbon steel with 1.95 wt.% C is studied. The temperatures of the phase transformations in the steel are determined. X-ray diffractometry is performed. A heat treatment mode preventing the formation of ledeburite in the structure of the steel and promoting a uniform distribution of carbide particles in the matrix is suggested.

Heat treatments are frequently used to modify the microstructure of cast irons according to experimental parameters. Among these, laser surface engineering (LSE) has become relevant for being a highly localized treatment with rapid heating and cooling of the irradiated area resulting in minimal distortion of the workpiece. This work presents and experimentally validates a thermo-metallurgical model able to predict the phase transformations occurring during the LSE treatment of nodular cast iron when it is subjected to different laser beam powers and scanning velocities. For this purpose, an experimental characterization of the thermal history and final microstructure is performed for several operating scenarios. In particular, significant changes in the microstructure can be seen at high powers and low scanning velocity where the matrix is transformed into ledeburite and martensite. The final phase volume fractions predicted by the proposed model along the depth of the sample are compared with the corresponding experimental measurements. The results obtained in the simulation are in good agreement with the experimental measurements. This work highlights the use of our model to be systematically applied for the design and optimization of LSE treatments on cast irons.

The dependence of the properties of high-carbon roll materials on their chemical composition is investigated. Both cast irons and ledeburite steels were chosen as the research materials. It was shown that the structure and phase composition of the studied materials determine their wear resistance. Alloying indefinite cast iron with molybdenum, vanadium and niobium increases its wear resistance.

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).

The structure and mechanical properties of an ultrahigh-carbon steel modified with amorphous ferrosilicon with a low melting point are studied. The methods of x-ray diffraction, optical and scanning electron microscopy are used to study the effect of the amorphous modifier on the structure of eutectic ledeburite in the cast steel. Tests for tensile strength and impact toughness are conducted. It is shown that the mechanical properties increase as a result of the modification without subsequent heat treatment.

The quenching heating temperature effect on the amount of retained austenite, the austenite stability from the strain martensitic transformation, as well as the hardening ability and abrasion resistance of high-carbon chromium ledeburite alloys (95Kh18 and 260Kh16M2 cast iron) have been investigated. The γ → α transformation and micro-TRIP-effect on the working surface of the alloys, a dissipative structure with a high degree of friction hardening and good abrasive wear resistance have been formed in this alloys.

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.

—The influence of vanadium on the microstructure, carbide deposition, and hardness of the chromonickel indefinite iron alloyed with ferrovanadium in the working layer of rollers is investigated. The microstructure of iron alloyed with nonnitrided ferrovanadium consists of primary dendrites; ledeburite; a small quantity of graphite; complex carbides MeC and carboborides Me(C, B) containing niobium, titanium, vanadium and chromium; and also chromium carbides of plate or needle morphology. In samples alloyed with nitrided ferrovanadium, the complex carbonitrides Me(C, N) are also seen. With increase in vanadium content, the proportion of these particles increases from 0.17 to 0.9% for samples alloyed with nonnitrided ferrovanadium and from 0.45 to 0.9% for samples alloyed with nitrided ferrovanadium. Their mean area varies from 1.5 to 2 μm2 and from 1.4 to 1.8 μm2, respectively. In iron alloyed with nitrided ferrovanadium, the maximum hardness (770 HV at a vanadium concentration of 0.4%) is greater than in samples alloyed with nonnitrided ferrovanadium (710 HV at a vanadium concentration of 0.3%).

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).

In the present study, 6 wt% Mo was added into high chromium cast iron (HCCI, 16 wt% Cr), and the effects of heat treatment on microstructure and mechanical properties of the base and alloyed HCCI were investigated. A ledeburite matrix and Mo-rich M2C were obtained besides M7C3 in the as-cast alloyed HCCI. During the soaking process of the destabilization treatment, amounts of secondary carbides (M23C6) precipitated out of austenite. Martenstic transformation of matrix occurred in the forced air cooling process. Most of the M2C decomposed into bright white fishbone M6C and punctate MC. The overall hardness of alloyed HCCI increased due to the presence of Mo-rich carbides and martensite matrix with secondary carbides. Comparing with the destabilized sample, the toughness of the alloyed HCCI improved and the hardness decreased after tempering treatment, and the toughness of the alloyed HCCI increased with the increase of tempering temperature. The abrasive wear resistance of the HCCI improved with the addition of Mo after heat treatment, and the QT500 sample had the optimal wear volume loss. The abrasive wear resistance decreased with the increase of tempering temperature, due to the exsolution of C atoms in the martensitic matrix.

A new approach for the development of medium Mn AHSS is proposed in this work. It exploits a fine scale (~ 100 nm) chemical patterning of Mn in austenite that may be obtained by the austenitisation of a pearlite structure formed under conditions with strong Mn partitioning between ferrite and cementite. The resulting ‘ghost pearlite’ ferrite/austenite can be subsequently treated to exhibit an interesting combination of ultimate tensile strength (UTS) (1600–2100 MPa) and ductility (7–10% elongation). The simple steel composition and very short processing provides a UTS-ductility combination similar to maraging steels and super bainitic steels.

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.

The effect of heating temperature for quenching on the amount of residual austenite, its stability with respect to strain martensitic transformation, as well as its hardenability and wear resistance in the process of abrasive wear of high-carbon chromium alloys of the ledeburite class: steel 95Kh18 and cast iron 260Kh16M2 have been studied.