Hardness Of Steel Research Articles

Competition and Precipitation Mechanism of Inclusions in the Al–Ti–Mg Complex Deoxidized Steel

In this work, the competitive precipitation mechanism of inclusions in Al–Ti–Mg complex deoxidized steel is investigated by experimental observation and thermodynamic analysis. Many types of inclusions are observed in steel, and the two and multi‐layer structural inclusions are composed of the single‐particle inclusions of TiS, TiN, TixOy, MnS, Al2O3, and MgAl2O4. Thermodynamic calculation results suggest that the transformation order of Al2O3 contains two pathways: one is Al2O3 → MgAl2O4 → MgTi2O4 → MgO and the second is Al2O3 → Ti2O3 → MgTi2O4. However, the transformation reaction of Al2O3 into MgAl2O4 or Ti2O3 has not completely ended, and no MgTi2O4 and MgO inclusions are found in the steel sample. The precipitation order of Ti2O3, TiN, TiS, and MnS in present steel is Ti2O3 → TiS → TiN → MnS. MnS only precipitated in solid steel, TiS, and TiN precipitated in the solid–liquid interface at T < 1794 K and T < 1796.5 K, respectively. The actual transformation and precipitation order of inclusion in the present Al followed by Ti–Mg deoxidized steel is Al2O3 → MgAl2O4 → Ti2O3 → TiN → TiS → MnS or Al2O3 → Ti2O3 → TiN → TiS → MnS.

Sliding Wear Behavior of WP7V Tool Steel with Different Hardnesses Under Reciprocating Test Rig

This study involved the investigation of the mechanical and tribological behaviors of DIN 1.2344 and WP7V tool steels, quenched in a salt bath after austenitization at 1050 °C, followed by triple tempering for 2 h. The selection of tempering temperatures produced two hardness levels under four metallurgical conditions, with the hardest level found only for WP7V steel (54 and 57 HRC). The mechanical properties were evaluated using Rockwell C, Vickers, and nanoindentation methods, along with unnotched impact tests, according to the SEP 1314 guidelines. Wear tests were conducted in a tribometer configured for a reciprocating setup, with a frequency of 5 Hz, a load of 25 N, and a time of 60 min, at room temperature and at 200 °C. As counterbodies, alumina balls of 5 mm in diameter were used. Wear tracks were evaluated through scanning electron microscopy, EDS, interferometry, and Raman spectroscopy. Friction and wear behaviors were affected by the variation in temperature for softer steels (DIN 1.2344 and WP7V of 48.5 HRC): the higher the temperature, the better the tribological performance. The harder steels were not sensitive to temperature testing. These effects depend on maintaining iron oxide (hematite) at the point of contact. The wear rates determined for the hardest material (57 HRC), considering its impact resistance, make it unsuitable for severe conditions such as hot stamping.

Effect of Annealing Time on Pitting, Intergranular Corrosion, and Hardness of Stainless Steels

Stainless steels are the material that has chromium as a main component. The chromium content reacts with oxygen in air, subsequently, forms thin chromium oxide film on the surface of stainless steels. Thus, when these steels are exposed to high temperature for a long period of time in many applications, chromium carbide could precipitate along the grain boundary and reduce the corrosion resistance. This project is conducted to study annealing time effect on stainless steels when exposed to high temperature at various exposure time periods. Three different kind of stainless steels, namely, AISI 304, AISI 304D and AISI 2205 were used in this study. Stainless steels were heated at 600°C for 0, 6, 24, 48 and 96 hours, then cool down in air. Consequently, the investigations were performed by using double-loop Electrochemical Potentiokinetic Reactivation (DL-EPR) and Cyclic Potentiodynamic Polarization (CPP) to study degree of sensitization and film properties. In addition, chromic acid and oxalic acid were used as reagent of acid etching to observe microstructures. Finally, Vickers hardness test were also conducted. Percentage degree of sensitization increased from 2.93% to 62.20% in AISI 304, increased from 5.26% to 55.54% in AISI 304D and from 12.19% to 69.35% in AISI 2205. The pitting potential decreased from 0.47 mV to 0.23 mV for AISI 304 but remained relatively constant for AISI 304D and AISI 2205. The results indicated that after the specimens were exposed to high temperature for a long period of time, all specimens had more chromium depleted areas, more carbide along the grain boundaries, worse film quality and small changes in hardness value.

Research status of reversed austenite in martensite: Review

Abstract This paper studies the role of reversed austenite in martensitic stainless steels, summarizes the formation principles of reversed austenite in martensitic stainless steels and reviews elements influencing its formation. It also summarizes common heat treatment methods for obtaining reversed austenite in martensitic stainless steels and compares the advantages and disadvantages of various approaches. For example, layered quenching and tempering yield more reversed austenite compared to simple tempering, resulting in finer microstructures at room temperature.The paper analyzes how different reversed austenite contents affect the strength, ductility, and hardness of martensitic stainless steels, as well as the impact on pitting, intergranular, hydrogen, and stress corrosion. It finds that a higher amount of reversed austenite leads to a higher yield-to-tensile strength ratio, increased ductility, and lower hardness. While reversed austenite improves resistance to pitting, intergranular, and stress corrosion, its effect on hydrogen embrittlement remains debated.Additionally, the paper summarizes the formation principles of reversed austenite in martensitic stainless steels and reviews elements influencing its formation, aiming to identify optimal elements and heat treatment methods to increase reversed austenite content. This paper aims to make a summary of the research of experts and scholars in recent years, provide the knowledge foundation for the scholars who have just contacted, and give some reference for the future research direction.

THE INFLUENCE OF QUENCHING AND TEMPERING ON THE HARDNESS AND MICROSTRUCTURE OF 42CrMo4 STEEL

This article deals with the effect of quenching and tempering on the hardness and microstructure of 42CrMo4 steel. All investigated samples were water quenched from an austenitizing temperature of 820 °C. After quenching, the samples were tempered at 610 °C, for 30 minutes and for 60 minutes. After the heat treatment, the cross-sectional hardness of the samples was measured. The hardness was measured using the Vickers tester and a test force of 98,1 N (HV10). The highest average hardness was achieved after quenching with values of 657,3 HV10 on the surface and 487,6 HV10 in the core. Samples that were tempered for 30 and 60 minutes showed an average surface hardness of 364,3 HV10 and 330 HV10 and an average core hardness of 332,3 HV10 and 303,3 HV10, respectively. The microstructure was investigated by the use of light optical microscope.

Theoretical precipitation modeling and multidimensional characterization of sulfide inclusions in tellurium-containing steels

This study investigates the precipitation characteristics of sulfide inclusions during the solidification of alloy steels under the combined influence of sulfur (S), manganese (Mn), and tellurium (Te). A multidimensional characterization and comparison of sulfide inclusions in Te-containing steels with varying sulfur content and cooling conditions were performed using X-ray Micro-CT, Raman spectroscopy, and field emission scanning electron microscopy (FE-SEM). Both 2D and 3D analyses confirmed that increasing the S content in Te-containing steels leads to a higher overall number of sulfide inclusions. In particular, the rise in the proportion of small-sized inclusions was analyzed from the perspectives of interfacial dynamics and equilibrium thermodynamics. Regarding inclusion morphology, 2D characterization exhibited significant inaccuracies in assessing large inclusions in high-S, Te-containing steels, while X-ray Micro-CT proved advantageous for evaluating both the spatial distribution and morphology of inclusions. In addition, X-ray Micro-CT was used for the first time in this study to perform a non-destructive analysis of the layered MnS-MnTe structure, expanding the method's application in the metallurgical field. A predictive model based on inter-element activity interaction coefficients was employed to determine the first-order activity interaction coefficient of Te for Mn. Furthermore, a thermodynamic model for sulfide precipitation in Te-containing steels was developed. This study lays a theoretical foundation for better control of sulfide inclusions in future Te-containing specialty steels.

Effect of Vanadium-Alloying on Microstructural Evolution and Strengthening Mechanisms of High-Nitrogen Steel Processed by High-Pressure Torsion

We study the effect of high-pressure torsion on the microstructure, phase composition, microhardness, and strengthening mechanisms of high-nitrogen austenitic steels with different vanadium content: Fe-23Cr-19Mn-0.2C-0.5N, Fe-19Cr-21Mn-1.3V-0.3C-0.8N, and Fe-18Cr-23Mn-2.6V-0.3C-0.8N, wt %. Regardless of the chemical composition of the steels, high-pressure torsion (HPT) causes the refinement of their microstructure due to a high density of dislocations, twin boundaries, and shear bands. Vanadium alloying decreases the stacking fault probability in the structure of the steels and changes their dominating deformation mechanism under high-pressure torsion: from planar dislocation slip and twinning in the vanadium-free steel to dislocation slip with a tendency to shear band formation in the vanadium-alloyed steels. An increase in the vanadium content forces precipitation hardening. Thus, after HPT, the V-alloyed steels have a higher microhardness as compared to the vanadium-free one. Different strengthening factors (strain hardening, solid solution hardening, and precipitation strengthening) govern the value and kinetics of growth of microhardness of the steels processed by high-pressure torsion. Vanadium alloying and increasing its content result in the growth of the contribution of precipitation hardening and decreases strain hardening of high-nitrogen steels.

Tracking research on the performance changes of S31042 steel under long term service

S31042 is widely used in ultra-supercritical units due to its excellent comprehensive performance at high temperatures. Tracking and monitoring research was conducted on as-received S31042 tubes and tubes in service for 13k hours, 31k hours, and 52k hours at 650 °C. The results show that as the service time increased, a large quantity of M23C6 phase precipitated along the grain boundaries, gathered and grew up into the bulk. This weakened of the grain boundaries, which facilitated crack propagation and significantly reduced the plasticity and toughness of the S31042 heat-resistant steel. After 13k hours of operation, the dispersion strengthening of the precipitated phase inside the grain and grain boundary led to a substantial increase in hardness, while there was no obvious change in strength. However, after 52k hours of operation, the dispersed precipitated phase within the grain slowly aggregated and grew, decreasing the effectiveness of dispersion strengthening. Consequently, both the high-temperature strength and hardness of the S31042 steel gradually decreased. As the service time increased, the continuously distributed and similarly sized M23C6 phases on the grain boundaries of S31042 developed into an inhomogeneous coarsening chain structure. Additionally, the appearance of nanoscale secondary NbCrN and M23C6 phases within the grain and their resulting precipitation strengthening effects were the main reasons for the significant change in S31042 hardness values. Based on these findings, the residual life of S31042 heat-resistant steel in service was predicted using an extrapolation method based on high-temperature creep rupture tests and the relationship model between hardness and the P function. A comparison of the L-M parametric life prediction results with the strength extrapolation life prediction results based on the standard creep rupture test shows that the creep rupture strength extrapolation method is slightly conservative. Therefore, the prediction results based on the hardness L-M parameter method, which is simple and easy to perform, can be used for preliminary life prediction.

Effect of heat treatment on the interfacial element diffusion and hardness of FeCoNiCrAl high-entropy alloy coatings

FeCoNiCrAl high-entropy alloy (HEA) coatings have here been prepared on Q235 steel by using the plasma spraying technology. The effects of heat treatment (300 °C, 400 °C, and 500 °C) on the coating phase, surface and cross section morphologies, surface Brinell hardness (HRB), cross section Vickers hardness (HV), and element diffusion at the coating interface, were then investigated. The distribution of pores, cracks, and unmelted particles on the surface of the coating was analyzed by scanning electron microscopy (SEM). The results showed that the BCC crystalline structure of the HEA coating did not change significantly after heat treatment at 300 °C, 400 °C, and 500 °C. In addition, the bonding between the coating and the matrix interface became significantly improved, and the cracks at the coating interface were eliminated. New oxides that filled the pores and cracks inside and at the interface of the coating were also observed as the temperature and holding time increased. Furthermore, the surface hardness of the Q235 steel was reduced as a result of the spray coating. However, this surface hardness was increased to HRB 85 (or even more) after heat treatment. Compared with the other samples, the coating sample that was heat-treated at 500 °C showed the best strength.

Tool Wear Monitoring in Hard Turning Using Sensor Fusion: An analytical approach

At present, the life expectancy of tool has become a vital aspect in the manufacturing industries, especially where materials with high hardness have more importance. Nowadays hard steel has been widely used for manufacturing of commercial parts in military aircrafts, car systems and hydraulic tools, etc. Manufacturing industries, mainly concentrates on mass production of the products with precision and accuracy. In such cases the continuous machining may weaken the tool causing tool wear which ultimately affects the quality with production rate. To avoid such an unwanted scenario, different tool wear prediction techniques have been introduced which uses cutting force signals or average chip-tool interface temperature or surface roughness signals, etc. According to the literature, different techniques are available for the pre-judgment of the tool wear that shows variation in the accuracy of prediction. Sensor fusion technique can be employed to overcome this problem by combining data from different sensors intelligently to improve the process. Sensor fusion uses this combined data to correct deficiencies of individual sensors and predict the tool wear accurately which compensate for the sudden breakage of the tool in real life applications. In this paper, a new approach of tool wear prediction has been introduced to correlate different available sensor by using sensor fusion technique. Also, a mathematical approach has been derived for the sensor fusion purpose. The experimentation has been carried out using coated carbide inserts on 55 HRC hardened steel.

Microstructural, Mechanical, and Electrochemical Corrosion Properties of Extrusion Additive Manufactured 17-4 Precipitation Hardenable Stainless Steel

Microstructural, Mechanical, and Electrochemical Corrosion Properties of Extrusion Additive Manufactured 17-4 Precipitation Hardenable Stainless Steel

Ball-on-Disk Wear Maps for Bearing Steel–Hard Anodized EN AW-6082 Aluminum Alloy Tribocouple in Dry Sliding Conditions

In recent years, Golden Hard Anodizing (G.H.A.®) has been developed as a variant of the traditional hard anodizing process with the addition of Ag+ ions in the nanoporous structure. The tribological properties of this innovative surface treatment are still not well understood. In this study, ball-on-disk tests were conducted in dry sliding conditions using 100Cr6 (AISI 52100) bearing steel balls as a counterbody and GHA®-anodized EN AW-6082 aluminum alloy disks. The novelty of this work lies in the mapping of the wear properties of the tribocouple under different test conditions for a better comparison of the results. Three different normal loads (equal to 5, 10, and 15 N) and three different reciprocating frequencies (equal to 2, 3, and 4 Hz) were selected to investigate a spectrum of operating conditions for polished and unpolished G.H.A.®-anodized EN AW-6082 aluminum alloy. Quantitative wear maps were built based on the resulting wear rate values to define the critical operating limits of the considered tribocouple. The results suggest that the coefficient of friction (COF) was independent of test conditions, while different wear maps were found for polished and non-polished surfaces. Polishing before anodizing permitted the acquisition of lower wear for the anodized disks and the steel balls.

Development of significantly hard hypereutectoid plain carbon steel through incomplete austenitization based cyclic quenching treatment

AbstractIn this investigation hot rolled steel bars of 1.24 weight % carbon steel are subjected to incomplete austenitization based cyclic quenching treatment. Each cycle consists of inserting the specimen in an electric resistance furnace at a temperature of 894 °C and holding for a short duration (6 minutes), followed by oil quenching to the room temperature. Such a typical thermal cycling results in the evolution of a novel microstructure that comprises of large clusters and blocks of cementite in a matrix of martensite after 3 and 4 cycles. Accordingly, a significantly high hardness (7.13 GPa) is achieved on execution of 3 cycles which envisages a new pathway of incomplete austenitization based cyclic quenching treatment for development of new‐generation plain carbon hypereutectoid tool steel.

Effect of boron content and quenching temperature on the microstructure and wear resistance of high boron steel

Abstract This article investigates the change rule of the microstructure, hardness and wear resistance of high boron steel containing 0.1 wt.% to 0.5 wt.% boron in the cast state and after quenching at different temperatures. The results show that the microstructure of cast high boron steel with different contents of boron is composed of pearlite, ferrite and eutectic boride, which has lower hardness and wear resistance, and the higher the content of boron, the higher the hardness and the better the wear resistance. After quenching at 900–1,000 °C, pearlite and ferrite change into a large number of lamellar martensite and a small amount of lath martensite. After high-temperature quenching at 1,050 °C, retained austenite appears in the microstructure in addition to martensite, and borides are partially dissolved. The hardness and wear resistance are significantly improved compared to the as-cast high boron steel. As the quenching temperature increases, the dissolution of boride is obvious, the hardness and wear resistance are firstly increased and then decreased. When the content of boron is 0.5 wt.% and the quenching temperature is 1,000 °C, the hardness reaches a maximum value of 59.0 HRC, and the abrasion resistance is the best.

APPLICATION OF ELECTROLYTE BASED ON SODIUM CARBONATE FOR ELECTROLYTEPLASMA SURFACE HARDENING OF STEEL 45

This article evaluates the electrolyte-plasma hardening (EPH) of steel 45 using an electrolyte based on sodium carbonate (Na₂CO₃). Theoretical foundations of the electrolysis process of a sodium carbonate aqueous solution were studied during the course of the work. The mechanical and tribological properties of 45 steel samples after EPH were studied. It was found that with an electrolyte composition of 20% Na₂CO₃ and 80% distilled water, a hardened zone with a thickness of up to 5 mm is formed after EPH. The increase in microhardness reached up to 690 HV, which corresponds to a 3–3.5 times increase compared to the initial state. The results of tribological tests showed that the friction coefficient of steel 45 decreased after EPH, indicating a significant improvement in tribological characteristics compared to the initial value before hardening. Electrochemical tests on the corrosion resistance of steel 45 were also carried out. After EPH, the corrosion rate significantly decreased for steel 45 samples, indicating its highest corrosion resistance.

Unveiling the mechanism of the carbon ordering and martensite tetragonality in Fe–C alloys studied via deep-potential molecular dynamics simulations

The martensitic transformation plays a pivotal role in the strengthening and hardening of steels, yet an accurate interatomic potential for a comprehensive description of the martensitic phase formation in Fe–C alloys is lacking. Herein, we develop a deep learning-based interatomic potential to perform molecular dynamics (MD) simulations to study the martensitic phase transformation across a range of carbon (C) concentrations. The results reveal that an increased C concentration leads to a suppression of phase boundary movement and a deceleration of the phase transformation rate. To overcome the timescale limitations inherent in MD simulations, metadynamics sampling was employed to accelerate the simulations of C diffusion. We find that C atoms tend to cluster at distances equivalent to the lattice parameter of Fe with the same sublattice occupation, leading to local lattice tetragonality. Such C-ordered structures effectively inhibit dislocation movement and enhance strength. The stress field induced by dislocations facilitates a higher degree of ordering. The formation of C-ordered structures is identified as a potentially crucial strengthening mechanism for martensitic steels. The consistency between our simulation results and reported experimental observations underscores the effectiveness of the developed DP model in simulating martensitic phase transformation in Fe–C alloys, providing detailed insights into the mechanisms underlying this process.

The Effect of Heating Rate on the Microstructure Evolution and Hardness of Heterogeneous Manganese Steel.

The use of a rapid heating method to achieve heterogeneity of Mn in medium-manganese steel and improve its comprehensive performance has been widely studied and these techniques have been widely applied. However, the heating rate (from α to γ) has not received sufficient attention with respect to its microstructure-evolution mechanism. In this study, the effect of heating rate on the microstructure evolution and hardness of heterogeneous medium-manganese steel was investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and DICTRA simulation. The results showed that the Mn distribution was heterogeneous in the initial microstructure of pearlite due to strong partitioning of Mn between ferrite and cementite. At low heating rates (<10 °C/s), the heterogeneity of Mn distribution was diminished to some extent due to the long-distance diffusion of Mn in high-temperature austenite. Contrastingly, at high heating rates, the initial heterogeneity of the Mn element could be largely preserved due to insufficient diffusion of Mn, which resulted in more ghost pearlite (GP: pearlite-like microstructure with film martensite/RA). Moreover, the high heating rate not only refines the prior austenite grain but also increases the total RA content, which is mainly composed of additional film RA. As the heating rate increases, the hardness gradually increases from 628.1 HV to 663.3 HV, due to grain refinement and increased dislocation density. Dynamic simulations have also demonstrated a strong correlation between this interesting microstructure and the non-equilibrium diffusion of Mn.

Thermal Power and the Structural Parameters of a Wind Turbine Permanent Magnet Eddy Current Heater

Permanent magnet eddy current heating as a new type of wind energy utilization method, which is energy-saving, is zero-emission, and involves no pollution and a high utilization of wind energy, has attracted more and more attention. This paper deals with the simulation and optimal design of a permanent magnet eddy current heater (PMECH) driven by wind. Solid steel, closed-slot, and open-slot PMECH are proposed, and corresponding 2D finite element method (FEM) models are established. Using the skin depth concept, numerical analyses are conducted on the influence of the number, size, and position of copper strips on the thermal power of closed-slot and open-slot PMECHs, and the thermal power growth compared to solid steel PMECH. The results showed that there is an optimal value for stator wall thickness. When the air-gap length is 0.5 mm and the rotation speed is 200 and 1000 rpm, the optimal stator wall thickness is 16 and 9 mm, respectively. Compared to the influence of conductivity on thermal power, the influence of permeability is more significant. Compared with solid steel PMECH, both closed-slot and open-slot PMECH in a low-speed region can effectively improve thermal power, and the open slot has more obvious advantages. The maximum values of the thermal power growth (TPG) and thermal power growth rate (TPGR) of the closed-slot PMECH are 1.57 kW and 120.15%, respectively. The maximums of TPG and TPGR of the open-slot PMECH are 2.58 kW and 175.08%, respectively. The experimental results prove the validity of the analytical calculation.

Recrystallization Behavior of Computationally Optimized Low‐Alloy Steel at Various Temperatures and Strain Rates

The dynamic recrystallization (DRX) behavior of SA508‐III steel, a critical material for reactor pressure vessels (RPVs) normally treated by hot forging, is thoroughly examined in this article. In the investigation, elevated temperatures and the coarsening of metallic phases and carbides are revealed to contribute to the degradation of the steel's strength–toughness relationship. Utilizing computational thermodynamics, the stability of secondary phases, including carbides and brittle inclusions, is simulated to enable precise phase equilibrium calculations and accurate prediction of key mechanical properties such as yield strength, tensile strength, and hardness. These simulations facilitated targeted modifications to the alloy composition to enhance the steel's strength and hardenability under high‐temperature, high‐pressure conditions. In this study, alloy composition and processing parameters within the CALculation of PHAse Diagram framework, utilizing the ThermoCalc and JMatPro software packages, are optimized. In the microstructural investigations conducted under various isothermal deformation conditions (1173–1473 K) and strain rates (0.001–1 s−1), it is demonstrated that DRX mechanisms led to varied grain size developments, with a critical strain rate identified at 0.01 s−1 during high‐temperature deformations. In these findings, significant insights are provided into optimizing the mechanical performance of SA508‐III steel for RPV applications.

Buckling behaviour of high-strength retrofitted steel sections manufactured through post heat-treatment processes

High-strength steel is increasingly popular in construction for its strength-to-weight ratio, which lowers the self-weight of structures and reduces transportation, erection, and foundation costs. Induction hardening (IH) process which involves rapid heating and cooling of the material leads to microstructural changes which enhance the hardness and strength of conventional steel, elevating it to the level of High Strength (HS) steel. This study reports an extensive investigation on the buckling response and design of IH post-treated structural steel Circular Hollow Sections (CHS). It includes tensile coupon tests, microstructural analyses, initial geometric imperfection measurements, and residual stress evaluations to determine the effects of IH treatment on CHS. Column buckling tests were conducted, and a numerical model was developed and validated against the experimental results which was utilised to study systematically the effect of imperfections. The findings suggest that the magnitude of the imperfections in IH steel sections doubled compared to the non-treated condition, whilst there was a minimal impact on the residual stresses. A comprehensive parametric study was performed using finite element models to study the structural response of IH steel CHS columns over a large range of global slendernesses and allow the assessment of the buckling curves specified in EN 1993–1–1. It was concluded that the buckling curve a (imperfection factor, α=0.21) specified in EN 1993–1–1 provides the best buckling load predictions for the IH steel CHS columns, the response of which is superior to that of their virgin counterparts, despite the increased imperfections caused by the heat-treating process.