Eutectoid Steel Research Articles

Enhanced Surface Properties of 1080 Eutectoid Steel by Cathodic Cage Plasma TiN Deposition

Enhanced Surface Properties of 1080 Eutectoid Steel by Cathodic Cage Plasma TiN Deposition

Nanostructured Eutectoid Steel Synthesized by Mechanical Alloying and Spark Plasma Sintering

Nanostructured Eutectoid Steel Synthesized by Mechanical Alloying and Spark Plasma Sintering

Microstructural evolution and mechanical behavior of pearlitic steel under multi-directional forging

The mechanical behavior and the microstructural evolution of a pearlitic SAE 1080 steel were analyzed along 12 Multi-Directional Forging (MDF) cycles at room temperature and strain amplitude Δε ≈ 0.30 (MDF0.30). The resulting cumulative strain flow curve is typical of metals undergoing extensive dynamic recovery, displaying appreciable work hardening up to a strain εt ≈ 0.9, followed by a very low work hardening, where flow stress rises from ≈1400 MPa to ≈1510 MPa. Similarly, the microhardness raises up to a total cumulative strain εt ≈ 1.8 and seems to stabilize for further straining, reaching ∼3626 MPa after εt ≈ 10.8. Conversely, yield strength initially rises and then falls remarkably after εt > 5.4. This behavior is related with directional cross effects that favor dynamic recovery as the total applied strain increases. These results differ remarkably from those connected to a monotonic deformation process such as axisymmetric drawing. In addition, directional cross effects decrease the material yield stress as the total applied strain increases. Microstructural results revealed that MDF0.30 leads to increasing shearing, bending and fragmentation of the cementite lamellae into particles <50 nm in diameter dispersed in the ferritic matrix as the total imposed strain rises. As a consequence, only limited alignment and changes in the cementite interlamellar spacing are observed, up to a total applied strain ≈10.8. It is considered that the work hardening of pearlitic steel deformed through MDF0.30 is dominated by the dynamic recovery of the interlamellar ferrite and a limited contribution from the cementite. Such results have never been reported in the literature and are of practical importance, since extensive cold working of eutectoid steel through MDF can be performed with standard presses and large specimens.

Pearlite Growth Kinetics in Fe-C-Mn Eutectoid Steels: Quantitative Evaluation of Energy Dissipation at Pearlite Growth Front Via Experimental Approaches

Essential understanding of the pearlite growth kinetics is of great significance to predict the lamellar spacing and the resultant mechanical properties of pearlitic steels. In this study, a series of eutectoid steels with Mn addition up to 2 mass pct were isothermally transformed at various temperatures from 873 K to 973 K to clarify the pearlite growth kinetics and the underlying thermodynamics at its growth front. The microscopic observation indicates the acceleration in pearlite growth rate and refinement in lamellar spacing by decreasing the transformation temperature or the amount of Mn addition. After analyzing the solute distribution at pearlite growth front via three-dimensional atom probe, no macroscopic Mn partitioning across pearlite/austenite interface is detected, whereas Mn segregation is only observed at ferrite/austenite interface. Furthermore, in-situ neutron diffraction measurements performed at elevated temperatures reveal that the magnitude of elastic strain generated during pearlite transformation is very small. Based on the thermodynamic model, these experimental results are used to estimate the contribution of various factors to the total energy dissipation. Compared with the Mn-free alloy, the retardation effect of Mn addition on pearlite growth kinetics, which is partly due to the reduced driving force for pearlite growth, can be well explained by further considering the solute drag effect of Mn.

Increasing the Strength and Impact Toughness of Carbon Steel Using a Nanosized Eutectoid Resulting from Time-Controlled Quenching.

High-carbon steels are normally used as tool materials. The use of such steels for construction is limited due to their increased brittleness and poor weldability. However, it appears that high-carbon steels possess certain hidden reserves for enhanced plasticity and strength if properly heat-treated. An unconventional heat treatment was applied to carbon eutectoid steel (0.8 wt.% C) in order to increase its strength and impact toughness simultaneously. Samples for tensile and impact testing were held at 800 °C for different time ranges from 3 min to 9 min with subsequent cooling in oil. It was established that for each type of sample, an optimal holding time exists that is responsible for increased strength and high impact toughness. The hardness and microhardness levels of the surface and under-surface regions of the samples reached 390 HV after optimal heat treatment. An X-ray revealed a shift of the (211)α-peak to the lower 2-theta angles after heat treatment with the optimal holding time; this indicates an increase in carbon content in alpha solid solutions of approximately 0.12 wt.%. Thus, a nanostructured mixture of low-carbon martensite and thin cementite plates is formed in the under-surface region of carbon eutectoid steel after heat treatment, with a controlled holding time at the austenitizing temperature.

Hybrid Treatment and Natural Aging Behavior of Peak-Aged Eutectoid Steel Powder-Reinforced Al 7075 Matrix Composites

The current work focuses on the natural aging phenomenon of a eutectoid steel powder-(0.8 wt.%) reinforced Al-Zn-Mg (Al 7075) alloy, which was subjected to a hybrid heat treatment. The hybrid treatment comprises the aging treatment of a matrix and the conventional treatment of a steel reinforcement in a single stretch on the stir cast composite. This material finds uses in space and transportation applications. The hybrid treatment consists of a conventional heat treatment cycle to obtain pearlite, bainite, and martensite phases in steel powder, followed by an age-hardening treatment for the Al 7075 matrix. This hybrid heat treatment resulted in improvements in the hardness and strength over the conventional aging treatment. The peak-aged hybrid specimens were subjected to natural aging in an open atmosphere for a continuous duration of 25 weeks to study the stability of the properties after peak aging. Tests of the mechanical properties such as the hardness and tensile strength along with microstructure analysis were carried out. During natural aging, the hardness of composites decreases irrespective of the quantity of the reinforcement in the composites and the type of reinforcement phase alteration during hybrid heat treatment. Also, the composites subjected to hybrid heat treatment show better resistance to natural aging compared to the conventionally aged samples. Within the group, the hybrid-treated martensite formed into a composite with 6 wt.% reinforcement showed only a 4% reduction in hardness during natural aging, which is an indication of a decent level of resistance to natural aging.

Archaeometallurgical Study of a 16th–17th Century “Rapier” Sword Manufactured in Caino (Northern Italy)

AbstractA metallurgical study was performed on a 16th–17th century “rapier” sword manufactured in Caino (northern Italy). Metallographic investigations and Vickers microhardness measurements indicate that the rapier was forged by assembling via hammer-welding different hypoeutectoid and near eutectoid steel bars. The rapier blade was heat treated by slack-quenching to increase its hardness, especially near the blade tip, improving the thrusting performance. The chemical composition of slag inclusions was analyzed by scanning electron microscopy coupled with X-ray dispersive spectroscopy. Compositional data of slag inclusions were analyzed by a multivariate statistical strategy aimed to distinguish and classify slag inclusions on the basis of their origin. It was estimated that the temperature reached during the finery and forging processes was at least 1270 °C and 1160 °C, respectively.

Cryogenic Treatment of Martensitic Steels: Microstructural Fundamentals and Implications for Mechanical Properties and Wear and Corrosion Performance.

Conventional heat treatment is not capable of converting a sufficient amount of retained austenite into martensite in high-carbon or high-carbon and high-alloyed iron alloys. Cryogenic treatment induces the following alterations in the microstructures: (i) a considerable reduction in the retained austenite amount, (ii) formation of refined martensite coupled with an increased number of lattice defects, such as dislocations and twins, (iii) changes in the precipitation kinetics of nano-sized transient carbides during tempering, and (iv) an increase in the number of small globular carbides. These microstructural alterations are reflected in mechanical property improvements and better dimensional stability. A common consequence of cryogenic treatment is a significant increase in the wear resistance of steels. The current review deals with all of the mentioned microstructural changes as well as the variations in strength, toughness, wear performance, and corrosion resistance for a variety of iron alloys, such as carburising steels, hot work tool steels, bearing and eutectoid steels, and high-carbon and high-alloyed ledeburitic cold work tool steels.

Металознавчі аспекти дисперсійного нітридного зміцнення високовуглецевих сталей Повідомлення 1. Вплив параметрів аустенізуючого нагріву та відпуску на фазовий перерозподіл азоту та ванадію в сталях

Systemic fundamental research for several decades at the FTIMS of the National Academy of Sciences of Ukraine and the accumulated experience of industrial application have shown that the technology of dispersion nitride hardening, which is based on the alloying of steels with nitrogen and vanadium, is a method of significantly improving the entire complex of physical, mechanical and operational properties of cast and deformed carbon, low-alloy and alloy steels of various functional purposes. The most significant advantage of the steels developed at the FTIMS of the National Academy of Sciences of Ukraine is a simultaneous significant increase in their static and cyclic strength, fracture toughness, thermal strength and heat resistance, wear resistance, annealing, weldability, reduction or complete elimination of the tendency to natural, deformation and warm embrittlement. Medium- and high-carbon pre-eutectoid and eutectoid steels of high strength and wear resistance are widely used in various fields of mechanical engineering. However, they are most widely used for railway wheels and rails. The reliability and operational resource of wheels and rails, which are in extremely harsh operating conditions, mainly determine the technical and economic performance indicators of railway transport. At the same time, existing relatively cheap non-alloyed and low-alloyed medium- and high-carbon wheel and rail steels no longer meet the modern requirements of increased speeds and load capacity of rolling stock. Keywords: carbon steels, dispersion nitride hardening, austenization, tempering, phase redistribution of nitrogen and vanadium.

A microstructure-based constitutive model for eutectoid steels

This work presents a constitutive model for eutectoid steels based on their two-phase lamellar microstructure. The model accounts for the individual behaviour of both ferrite and cementite, with perfect interphase adhesion assumed. It considers anisotropic hardening mechanisms in ferrite derived from the lamellar structure of pearlite while ignoring the crystal structure of either phase. The model also accounts for the evolution of orientation and spacing of lamellae under directional deformation, along with the evolution of internal stress distribution in both phases. Due to its simplicity, the model has very few calibration parameters but is still able to reproduce complex strain paths and loading conditions with excellent accuracy. The model was compared with tensile, compression and torsion tests from a 13-pass wire drawing series (up to drawing strains of 2.7) and reproduced accurately the mechanical response under any loading condition. The robustness of the model lies in the fact that it is able to recreate the evolution of internal stresses built in cementite and ferrite. Such internal stress evolution was confirmed to reproduce accurately the stress partitioning observed in neutron and X-ray diffraction tests reported in literature. Moreover, the model contributes to the understanding of the rapid broadening of cementite diffraction peaks observed during in-situ tensile tests of patented wires.

Influence of the Morphology of Eutectoid Steels on Corrosion Resistance in NaCl Aqueous Medium with and without CO2

This study conducts a comparative electrochemical evaluation of three types of pearlitic steels used in flexible pipelines for oil transport in marine environments. The steels have been manufactured with chemical composition and geometry variations to optimize operation performance under adverse conditions. Electrochemical tests were conducted using solutions simulating marine environments with NaCl and CO2, and at high temperatures. The results indicated that spheroidized (SC) steel demonstrated the best corrosion resistance under these specific conditions. Additionally, the Raman spectroscopy characterization technique was used to analyze the layers of corrosion products formed during the tests, identifying the presence of FeCO3 (siderite) and other corrosive oxides. These discoveries are valuable for selecting and improving materials in flexible pipelines used in oil production in marine waters. The study highlights the importance of the cementite morphology present in pearlite as a relevant factor in the corrosive behavior of steels, contributing to the development of more efficient and durable solutions for the offshore oil and gas industry.

To study the effect of Ni particles on microstructures and mechanical properties of Indium-Bismuth solder alloy

In this work, Ni particles were added to the In-34Bi solder alloy to enhance the mechanical properties of solder at ambient temperature. The microstructure seems to be fingerprint-like structures similar to pearlitic structures as seen in eutectoid steel. However, in this case, InBi2bands are seen in the Indium matrix. The distribution of Nickel particles was seen in backscattered images of scanning electron macroscopic images. Mechanical properties are improved by the addition of Ni particles in In-34Bi-1Ni solder alloy. The solder alloy's hardness has improved by 36%, its 0.2% proof stress has risen by 34%, and its ultimate tensile strength has increased by 40%. Distribution of Ni particles in In-34Bi-1Ni solder alloy confirmed In2Bi and Ni2In3. The presence of Ni and Ni2In3 tends to decrease ductility from 50% to 35%. The addition of Ni particles in In-34Bi-1Ni showed significant improvements in mechanical properties.

Fatigue Crack Propagation in Pearlitic Steel under Pressurized Gaseous Hydrogen: Influences of Microstructure Size and Strength Level

For the wall-thickness reduction of the components destined for pressurized gaseous hydrogen, widespread use of high-strength martensitic steels has long been desired. However, their strong susceptibility to hydrogen-assisted fatigue crack growth (HA-FCG) is still limiting their proactive applications. Here, we instead focused on pearlite as another potential reinforcing agent for the development of new hydrogen-compatible steels with acceptable cost performance. Fatigue crack growth (FCG) behavior of three eutectoid steels with different microstructure sizes (i.e., ferrite/cementite interlamellar spacing, colony and block sizes) and strength levels was investigated in a 90 MPa hydrogen gas, an essential evaluation when attempting to perform a defect tolerant design of the components used for high-pressure gases.

Occurrence of characteristic defects of grinding balls from rejects of continuously cast billets of rail steel

On the basis of metallographic studies, the authors determined the characteristic defects of grinding balls rolled from the rejects of continuously cast billets of K76F rail steel. Relationship of the presence of internal defects of the balls with their impact resistance was established. Defects in the form of internal cracks with accumulations of non-metallic inclusions in the area of their localization and flocks have the greatest impact on the reduction of balls impact resistance. Such defects are the cause of balls destruction during impact resistance tests in 62 and 17 % of cases, respectively. The effect of internal cracks without significant accumulations of non-metallic inclusions and quenching microcracks located along the boundaries of the phase interface was estimated at 12 and 9 %. The regularities and mechanism of influence of the rejects chemical composition of K76F rail steel billets on the probability of destruction of the balls produced from them during impact resistance tests were established. An increase in sulfur content in the billets of the studied rail steel reduces impact resistance of the balls produced from them, as it contributes to formation of non-plastic sulfides that concentrate in the area of internal cracks. An increase in hydrogen content in rail steel naturally contributes to an increase in probability of formation of the flocks, which significantly reduce the balls stability to shock loads. An increase in carbon content in the initial billets affects the increase in probability of destruction of K76F steel balls during copra tests. It is explained by formation of cementite-type carbides when carbon content corresponding to the eutectoid steel is reached. In general, the relative degree of influence of the K76F rail steel chemical composition on impact resistance of grinding balls is 48 %.

Optimization of the dilution parameters to improve wear resistance of laser cladding 15-5PH steel coating on U75V pearlitic steel

The dilution effect of the substrate during laser cladding is inherent, and controlling the dilution degree paves the way for the microstructural design of coatings with excellent mechanical properties. In this study, low-carbon 15–5 precipitation hardening (PH) stainless steel was selected as the cladding material on the surface of U75V pearlitic railway steels to improve wear performance. By altering the processing parameters, the cracking susceptibility, microstructures, and wear resistance of coatings with different dilution rates were investigated thoroughly. The results indicated that with the increase of laser beam power, the dilution effect of the eutectoid steel substrate enhanced obviously, resulting in the composition deviation of coatings. Microhardness of the coatings increased with the dilution rate but the excessive dilution effect led to severe cracking defects. The optimized cladding coating with a dilution rate of about 48 % exhibited a microhardness of 490 HV, and the wear tests showed that the wear volume decreased by about 85 % when compared to that of the U75V substrate. Microstructural characterization revealed that the increased carbon content induced by dilution, resulting in martensite hardening and carbides precipitation, was responsible for these performance improvements. This work demonstrated the potential of coating strengthening by dilution control, which expands the option for surface modification materials for railways.

Wear and rolling contact fatigue competition mechanism of different types of rail steels under various slip ratios

This study aims to explore the wear and rolling contact fatigue (RCF) competition mechanism of the hypoeutectoid, eutectoid rail, and bainitic rail steels under different slip ratios. The results showed a clear competition relationship between wear and RCF of rail steel. With the increase in slip ratio, the wear rate of hypoeutectoid and eutectoid rail steels was increased and then remained stable, and the wear rate of bainitic rail steels was increased. Bainitic rail steels suffered catastrophic wear when the slip ratio exceeded 2%. With the slip ratio increased, the RCF crack propagation rate of the hypoeutectoid rail and eutectoid steels rail increased rapidly at first and then increased slowly. Except for the slip ratio of 5%, the RCF crack propagation rate of the bainitic rail increased with the increase in slip ratio. With the increase in slip ratio, the degree of wear rate increase and crack propagation rate was not consistent, which led to the competition between wear and RCF. The competitive relationship between wear and RCF was reflected in the variation of rail wear form. As the slip ratio increased, the main wear form of the hypoeutectoid and eutectoid rail steels was transformed from adhesive wear to adhesive wear and fatigue wear, whereas for bainitic rail steel, it was changed from adhesive wear to fatigue wear, and finally to adhesive wear. At high slip ratios, the retained austenite of bainite rail steel was seriously broken, so cracks in the bainitic rail steel could easily propagate along the plastic deformation layer.

An analytical model to ascertain the fragmentation of cementite lamella at lamellar fault sites

ABSTRACT An analytical model is conceptualised and implemented for the first time to study the kinetics of cementite lamella fragmentation at the lamellar fault site occurring at an early stage of austenitisation in eutectoid steel. The model is conceived on the basis of two prime diffusion phenomena; namely, the curvature-dependent diffusion within cementite lamella and the diffusion-assisted dissolution in austenite. Both these diffusion phenomena are observed to have adequate significance in view of respective kinetic factors ascertained therein. The model is validated with necessary experimental work pertaining to the progress of lamellar fragmentation during isothermal holding at an austenitisation temperature of 775°C. The experimental result is closely followed by the developed model. A lamellar fragmentation time of 260 s is predicted accordingly for the incomplete austenitisation-based heat treatment of eutectoid steel.

Ефективність впливу легування міддю на зношування заевтектоїдних сталей

The intensity of wear of graphitized eutectoid steels with a carbon content in the range of 1.1÷1.7%, by weight was investigated. The effectiveness of the effect of copper doping on the wear of eutectoid steels in the cast state has been determined. It was established that under conditions of dry friction by sliding and taking into account the friction parameters in the sealing units the temperature on the worn surface and in the thin near-surface layer should exceed 1100 0С, at such temperatures and copper content more than 12%, by weight, in the binary system Fe-Cu there is a two-phase region +-phase, and  - phase, exists in the state of liquid and acts as a lubricant, the wear mode goes from dry to limiting. Lines of existence of -phases in the liquid state are constructed. The results of studies of the effect of copper on the intensity of wear of steels with different carbon content, under conditions of dry friction by slipping, indicated that regardless of the amount of carbon, doping of alloys with copper significantly reduces their intensity of wear to copper content at the level of 10-12%, by weight, a further increase in copper doping equalizes the effectiveness of the impact and reduces the intensity of wear. Alloying of steels with copper of 12% or more causes the formation of a copper phase film on the friction surface. Under the condition of alloying steel with copper less than 12%, the steel structure contains -phase, as a product of a three-phase eutectoid reaction and as a decomposition product of supersaturated solid iron solution. As the copper content in steel increases, the amount of copper phase in the steel structure and its amount on the contact surface increases, after reaching the copper content in the steel sufficient to form the primary grains of the copper phase, the formation of a stable layer of copper on the contact surface begins, which is the constant boundary layer of copper -phase in the liquid state. Keywords: steel, copper, carbon, alloying, wear resistance, friction.

Improving the Performance Properties of Eutectoid Steel Products by a Complex Effect

This study focuses on the assessment of possible hypereutectoid steel carbide mesh crushing. It is used for tools production, including forming rolls of various diameters, with modification and cyclic heat treatment methods. For steel containing 1.79-1.83% C, we studied the effect of 0.35-1.15% Si on the possible crushing of the cementite mesh within crystallization by introducing modifiers Ti, V, N, as well as simultaneously modifying V with N and Ti with N. The obtained castings of Ø200 mm, 400 mm high were cut into discs, from which we made samples for tests on wear, determining mechanical properties, thermal resistance, and susceptibility to brittle fracture. The assessment was performed in the as-cast and after double and triple normalizing and annealing with drawback. With additional fans blowing, we changed the cooling rate from 25 °C/h to 100-150 °C/h. We performed the microstructure analyses using traditional metallographic, micro-X-ray spectral analyses, and also used the segmentation process based on 2D image markers. It was found that the as-cast modifying additives infusion is insufficient for carbide mesh crushing. It can be made by multi-stage normalizing with accelerated cool-down for products up to 600 mm in diameter to cycle temperatures above the steel transfer from a plastic to elastic state (above 450 °C).

Microstructure and aqueous corrosion in carbon steel: An emerging correlation

A near eutectoid (0.72 wt% carbon) steel was subjected to controlled cooling in a dilatometer. Increasing cooling rate led to progressive microstructural evolution: from reconstructive pearlite (with decreasing interlamellar spacing) to displacive martensite (of diminishing grain size but enhanced acicularity). The martensite obtained at the fastest cooling (100 Ks−1) was also subjected to tempering. The corrosion performance of specimens with different microstructures was then evaluated using electrochemical (potentiodynamic polarization and electrochemical impedance spectroscopy) tests. The aqueous corrosion rate varied (i) non-linearly with pearlite spacing but (ii) linearly with features of the martensite microstructure. The non-linear dependence of corrosion on pearlite spacing was attributed to alignment or branching-induced interface crystallography. The corrosion current in martensitic or tempered martensite structures scaled linearly with increased martensite grain or lath size but decreased c/a ratio. A clear correlation between electrochemical responses and local depth of attack was also established.