Iron-carbon Alloys Research Articles

Reexamination of crystal growth theory of graphite in iron-carbon alloys

Most analysis of graphite morphology in cast iron-carbon alloys is performed on samples cooled to room temperature. This raises the concern that the crystallization of graphite is obscured by subsequent recrystallization and growth in solid state. To bring clarity to this issue, the authors used Field Emission Gun Scanning Electron Microscopy on deep-etched interrupted solidification (quenched) specimens to reveal the morphology of graphite growing in contact with the liquid at the very beginning of solidification.To understand the complexity of graphite crystallization in iron alloys, the analysis included evidence from the crystallization of materials with analogous hexagonal structure, such as of snowflakes and metamorphic graphite, and from the crystallization of diamond cubic structure silicon crystals in aluminum-based alloys. Information from research discussing graphite produced through gas-solid (chemical vapor deposition) and solid-solid (graphite in steel) transformations was also exploited.The large variety of graphite solidification morphologies described in this and earlier papers derives from the complexities of its faceted growth during crystallization, a diffusion-limited crystal growth process, in the presence of anisotropic surface energy and anisotropic attachment kinetics. It was confirmed that the basic building blocks of the graphite aggregates are hexagonal faceted graphite platelets generated through the growth of graphene layers. As solidification advances, the platelets thicken through layer growth through two-dimensional or screw dislocation nucleation. Depending on bulk composition, local supersaturation and undercooling, the platelets aggregate through a variety of mechanisms including tiled-roof and foliated crystals and dendrites, curved-circumferential, cone-helix, helical (macro-spiral), and polyhedral pyramidal (or conical) sectors growth. The final graphite shape of graphite spheroids is affected by the crystallography of the nucleus, as it affects the initial growth of the graphite platelets.

Nature of Angular Carbides in Damascus Steel

It is detected that in some specimens of Damascus steel part of the excess cementite is of unusual origin, in contrast to excess phases of secondary cementite, ledeburite cementite, and primary cementite in ironcarbon alloys. It is revealed that a morphological feature of separate particles of cementite in Damascus steel includes anomalously large excess carbides in the form of irregular octahedral and prisms. It is shown that angular carbides form within the original metastable ledeburite colonies, and therefore they are called “eutectic.” It is established that unalloyed materials of the carbide class acquire Damascus properties steel properties during isothermal exposure on annealing, which leads to thermal separation of colonies of metastable ledeburite, to limitation of newly formed eutectic carbides, and to their subsequent coalescence. It is revealed that some sorts of Damascus steel, being within the field of white cast iron with respect to carbon content, do not contain broken ledeburite within their structure. It is shown that the pattern of carbide inhomogeneity entirely consists of eutectic of angular carbides of non-etching triangular-prismatic morphology.

Modeling of the electron-beam boriding in the system Fe-B-C-O2

This paper reviews the conditions of iron borides formation and simulation of surface layers saturation depending on the stoichiometry of original components. Temperature fields have been investigated as well, which form certain phases in accordance with the pressure in the chamber and the power of the electron beam. A thermodynamic study of phase equilibria in Fe-B-C-O systems has been performed. This was done in order to optimize conditions for forming functional layers on the surface of iron-carbon alloys as a result of electron beam boriding in vacuum. Furthermore, strength characteristics of iron boride layers have been determined. Then these layers obtained by different methods and using various source components have been thoroughly compared with each other during the analysis.

Damascus steel ledeburite class

Discovered that some of blades Damascus steel has an unusual nature of origin of the excess cementite, which different from the redundant phases of secondary cementite, cementite of ledeburite and primary cementite in iron-carbon alloys. It is revealed that the morphological features of separate particles of cementite in Damascus steels lies in the abnormal size of excess carbides having the shape of irregular prisms. Considered three hypotheses for the formation of excess cementite in the form of faceted prismatic of excess carbides. The first hypothesis is based on thermal fission of cementite of a few isolated grains. The second hypothesis is based on the process of fragmentation cementite during deformation to the separate the pieces. The third hypothesis is based on the transformation of metastable cementite in the stable of angular eutectic carbide. It is shown that the angular carbides are formed within the original metastable colony ledeburite, so they are called “eutectic carbide”. It is established that high-purity white cast iron is converted into of Damascus steel during isothermal soaking at the annealing. It was revealed that some of blades Damascus steel ledeburite class do not contain in its microstructure of crushed ledeburite. It is shown that the pattern of carbide heterogeneity of Damascus steel consists entirely of angular eutectic carbides. Believe that Damascus steel refers to non-heat-resistant steel of ledeburite class, which have similar structural characteristics with semi-heat-resistant die steel or heat-resistant high speed steel, differing from them only in the nature of excess carbide phase.

Tribological Performance of TiO2-Nanostructured Particles as Oil-Lubricant Additives for Different Iron-Carbon Alloys

We evaluated the tribological performance of a dispersion of titanium dioxide (TiO2) nanostructured particles in car engine base oil for three different iron-carbon alloy materials (bearing steel, carbon steel and cast iron) in a disc–disc tribometer. The lubrication, friction and wear performance of the nanostructured particles was measured by testing three different configurations: 1) pure base oil, 2) base oil with additive package and 3) nanodispersion formulation. For the bearing steel – carbon steel configuration we found that the oil additive package reduces the coefficient of friction from µ =0.12 to µ=0.03. Upon adding TiO2-nanostructured particles to this formulation a further friction reduction by a factor of 3 to a superior frictional coefficient of µ<0.01 could be measured. This effect, however, could not be verified for the other two alloy material combinations, where the frictional coefficient was not affected by the nanostructured particle addition. Since carbon steel is characterized by the lowest Brinell hardness of the three tested alloy materials and exhibited the lowest surface roughness after the test procedure, we attribute the observed friction reduction to a lubricating titanium (dioxide) overlayer that builds up on the carbon steel surface but not on bearing steel and cast iron. This is supported by element-specific energy dispersive X-Ray analysis (EDX). Further attempts to optimize and predict nanotribological formulations for industrial applications are under way.

Eutectic Carbides in Damascus steel Ledeburite Class (Wootz)

Considered the nature of the change of the morphology of excess carbides in Damascus steel (Wootz), depending on the degree of supercooling of the melt, heat treatment and plastic deformation. Discovered that some of blades Damascus steel has an unusual nature of origin of the excess cementite, which different from the redundant phases of secondary cementite, cementite of ledeburite and primary cementite in iron-carbon alloys. It is revealed that the morphological features of separate particles of cementite in Damascus steels lies in the abnormal size of excess carbides having the shape of irregular prisms. Considered three hypotheses for the formation of excess cementite in the form of faceted prismatic of excess carbides. The first hypothesis is based on thermal fission of cementite of a few isolated grains. The second hypothesis is based on the process of fragmentation cementite during deformation to the separate the pieces. The third hypothesis is based on the transformation of metastable cementite in the stable of angular eutectic carbide. It is shown that the angular carbides are formed within the original metastable colony ledeburite, so they are called “eutectic carbide”. It is established that high-purity white cast iron is converted into of Damascus steel during isothermal soaking at the annealing. It was revealed that some of blades Damascus steel ledeburite class do not contain in its microstructure of crushed ledeburite. It is shown that the pattern of carbide heterogeneity of Damascus steel consists entirely of angular eutectic carbides. Believe that Damascus steel refers to non-heat-resistant steel of ledeburite class, which have similar structural characteristics with semi-heat-resistant die steel or heat-resistant high speed steel, differing from them only in the nature of excess carbide phase.

Формирование неоднородной структуры железоуглеродистых сплавов спеканием частиц разнородных сталей

Формирование неоднородной структуры железоуглеродистых сплавов спеканием частиц разнородных сталей

Morphology of Excess Carbides Damascus Steel

&lt;p class="1Body"&gt;Considered the nature of changes in the morphology of carbides of the unalloyed high-carbon alloys type Damascus steel depending on the degree of supercooling of the melt, heat treatment and plastic deformation. It is shown that iron-carbon alloy with carbon content as in white cast iron at high degrees of supercooling can crystallize as a high-carbon steel. Considered three hypotheses for the formation of the eutectic carbides in pure iron-carbon alloys. The first hypothesis is based on the thermal process of dividing plates of secondary cementite or of ledeburite on isolated single grain. The second hypothesis is based on the deformation process of crushing of secondary cementite or of ledeburite into separate fragments (the traditional view on the formation of eutectic carbides). The third hypothesis is based on the transformation of metastable ledeburite in a stable phase of eutectic carbide prismatic morphology. Found that some types of wootz, which carbon content as in of white cast irons not is contain its structure of ledeburite. It is shown that the structure of consists entirely of the eutectic carbides prismatic morphology.&lt;/p&gt;

Methods to Predict Stresses in Cutting Inserts Brazed Using Iron-Carbon Brazing Alloy

This work describes a method for predicting residual and operating stresses in a flat-form tool insert made of tungsten free carbides brazed using iron-carbon alloy. According to the studies’ results it is concluded that the recommendations relating to the limitation of a melting point of tool brazing alloys (950-1100°C according to different data) are connected with a negative impact on tools as a composite made of dissimilar materials rather than on hard alloys as a tool material. Due to the cooling process stresses inevitably occur in the brazed joint of dissimilar materials, and these stresses increase with the higher solidification temperature of the brazing alloy.

Wootz: Cast Iron or Steel?

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.

Damascus Steel Microstructure

The nature of change in the amount and morphology of iron dendrites and excess phases in relation to the degree of high-carbon alloy melt supercooling is considered. It is revealed that in pure iron-carbon alloys by changing the degree of melt supercooling it is possible to obtain steel with a carbon content as in white cast iron, or white cast iron with a carbon content as in steel. It is shown that before forging Damascus steel the structure is ideal with a pearlite matrix, without secondary free cementite, and with excess ledeburite phase. Features of ferrite and ledeburite shape change with thermomechanical treatment (forging) are studied. It is detected that during deformation heating for forging there is ledeburite recrystallization into a more stable phase of eutectic carbide. Limits are determined for transformation of pure high-carbon alloys in carbide class steel of the Damascus type.

Smelting in cupola furnace for recarburization of direct reduction iron (DRI)

Herein the synthesis of iron-carbon saturated alloys (foundries) melting in cupola furnaces from direct reduction iron is described. The fundamentals are reviewed and combinations undertaken are discussed along with their results, including conclusions and recommendations for follow up.

Carbon-depleted outer core revealed by sound velocity measurements of liquid iron–carbon alloy

The relative abundance of light elements in the Earth's core has long been controversial. Recently, the presence of carbon in the core has been emphasized, because the density and sound velocities of the inner core may be consistent with solid Fe7C3. Here we report the longitudinal wave velocity of liquid Fe84C16 up to 70 GPa based on inelastic X-ray scattering measurements. We find the velocity to be substantially slower than that of solid iron and Fe3C and to be faster than that of liquid iron. The thermodynamic equation of state for liquid Fe84C16 is also obtained from the velocity data combined with previous density measurements at 1 bar. The longitudinal velocity of the outer core, about 4% faster than that of liquid iron, is consistent with the presence of 4–5 at.% carbon. However, that amount of carbon is too small to account for the outer core density deficit, suggesting that carbon cannot be a predominant light element in the core.

Анализ влияния составляющих железоуглеродистых сплавов на их износостойкость при взаимодействии с абразивной средой

The article provides an overview of the influence of the main structural com-ponents (metallic, graphite, carbides) iron-carbon alloys on their wear resistance in the interaction with the abrasive. The results of laboratory testing of metals for wear

Laser-Plasma Treatment of Structural Steel

To conduct high production hardening modification of iron-carbon and titanium alloy surface layers a laser-plasma method (LPM) is developed. The method is based on the use of optical pulse discharge plasma. A discharge is ignited with laser pulses repeated with a high frequency by a CO2-laser oscillator - amplifier system. A laser pulse is focused on the treated surface. To form plasma in alignment with the beam in the laser head, a high velocity gas flow (air, nitrogen, argon, and carbon dioxide) is created. The pressure of the plasma-forming gas can reach 0.5 MPa, and the output speed of the laser head can be 300 m/s.The results of the experiment on the impact of laser-plasma action on the structure and microhardness of the structural steel surface are presented. Laser-plasma treatment leads to the formation of a layer with the martensitic structure on the surface of structural low-alloyed steel 40Kh. This layer is formed due to quenching in a liquid state (QLS) and quenching in a solid state (QSS). The microhardness of the martensitic layer is 11-13 GPa, the hardened zone depth reaches 0.3 mm. It is proposed to use laser-plasma treatment of structural steel as a method for the local surface hardening of machine parts and tools.

Effect of the method of introducing alloying compositions on the properties of the surface layer in iron–carbon alloy castings during lost-foam casting

The structure, the phase composition, and the properties of the surface layer in steel and cast iron castings are analyzed after alloying by B4C–Ti and B4C–FeTi compositions during lost-foam casting using different methods of their introduction. It is found that, irrespective of the method of introducing an alloying composition, the processes of physicochemical interaction between the alloying-composition components and a poured melt (according to the mechanism of self-propagating high-temperature synthesis) lead to the formation of titanium and iron borides, nitrides, carbides, and carbonitrides.

Модели и характеристики прерывистого превращения аустенита в железоуглеродистых сплавах

Модели и характеристики прерывистого превращения аустенита в железоуглеродистых сплавах

Evaluation of the Effect of Modifier Composition with Nanostructured Additives on Grey Cast Iron Properties

Production and use of modifiers for cast iron and steel are analyzed. Compositions of standard industrial modifiers are considered with evaluation of trends in their development. It is shown that a promising area for creating a new generation of fundamentally different types of modifier is nanomodification of molten iron-carbon alloys.

Structural, elastic, and thermal properties of cementite (Fe3C) calculated using a modified embedded atom method

Structural, elastic, and thermal properties of cementite (${\mathrm{Fe}}_{3}C$) were studied using a modified embedded atom method (MEAM) potential for iron-carbon (Fe-C) alloys. Previously developed Fe and C single-element potentials were used to develop a Fe-C alloy MEAM potential, using a statistics-based optimization scheme to reproduce structural and elastic properties of cementite, the interstitial energies of C in bcc Fe, and heat of formation of Fe-C alloys in L${}_{12}$ and B${}_{1}$ structures. The stability of cementite was investigated by molecular dynamics simulations at high temperatures. The nine single-crystal elastic constants for cementite were obtained by computing total energies for strained cells. Polycrystalline elastic moduli for cementite were calculated from the single-crystal elastic constants of cementite. The formation energies of (001), (010), and (100) surfaces of cementite were also calculated. The melting temperature and the variation of specific heat and volume with respect to temperature were investigated by performing a two-phase (solid/liquid) molecular dynamics simulation of cementite. The predictions of the potential are in good agreement with first-principles calculations and experiments.

Innovations and problems of the course “Science of materials and technology of construction materials”

The paper considers some innovative approaches for the study of the basic sections of the course and during the development of iron carbon alloys particularly. Methods of intensification of using interactive methods of training and knowledge control are suggested.