Volume Fraction Of Austenite Research Articles

Effects of austempering on the microstructure and mechanical properties of high-strength nanostructured bainitic steel containing 3.5 wt% aluminum

This study aims to produce a cost-effective and low-density, high-strength nanostructured bainitic steel by optimizing the austempering process conditions. To do this, a steel containing 0.8C-1.5Mn-0.6 Cr-0.35Mo-3.5Al was selected and the effects of austempering time and temperature on the microstructure and mechanical properties of this steel were studied. Xrd technique was used to recognize the phases present in the microstructure and measure the retained austenite volume fraction and carbon content. Hardness measurements showed that the highest value was obtained from the specimen containing the highest volume fraction of the bainitic ferrite associated with the retained austenite with the highest carbon content, at the completion time of transformation. Such a combination of microstructure and hardness was applied to find the optimum time at different temperatures during the austempering process. The microstructures of the optimal specimens were evaluated through optical microscopy (OM) and field-emission scanning electron microscopy (FESEM), and the average thickness of the bainitic ferrite plates was calculated. Finally, tensile tests were performed on the optimal specimens to assess the fracture surface through FESEM. For high steel with 3.5 wt% Al, the results indicated that it is possible to obtain a microstructure consisting of bainitic ferrite plates with an average thickness of 53 nm surrounded by the carbon-rich retained austenite with a hardness of 561HV, a yield stress of 1614 MPa, an ultimate tensile strength of 1981 MPa, and a total elongation of 9 %.

Calphad-assisted design of high strength – ductility martensitic stainless-steels with reverted austenite

Introducing reverted austenite at lath martensite boundaries has been shown to be an effective method to increase the ductility of martensitic steels. However, significant strength reductions can also be introduced during the reversion process in martensitic stainless steels. To overcome the strength-ductility trade-off, we explore the effects of alloying elements in delaying the overaging of the precipitates and accelerating the austenite formation. To this end, we carry multi-objective optimization considering (1) lattice misfit and diffusivity for kinetics of precipitation, and (2) austenite fraction and thermodynamic driving force of austenite reversion for austenite formation. With the insights from calculations, model alloy compositions are then proposed, and mechanical testing and microstructural analysis are applied. The model alloy confirms that a relatively higher volume fraction of austenite can form prior to overaging, which doubles the total elongation without significant strength loss.

Effect of Retained Austenite on the Microstructure and Micro-Hardness of AISI 4330 Low Alloy Steel Using X-Ray Diffraction method

The mechanical properties of low alloy steel are significantly influenced by retained austenite (RA). Consequently, using the X-Ray diffraction (XRD) measurement method, the retained Austenite volume fractions in AISI4330 alloy steel have been assessed in this article. The specimens underwent heat treatment at various heating temperatures (800 ֯C, 900 1000 ֯C) and cooling rates (Water and Oil). The findings demonstrate that retained Austenite formation rises with rising heating (Austenitizing) temperatures for the same quenching media as well as with rising cooling rates. The specimens were heated to a temperature of 1000 °C and then quenched in water, yielding the highest amount of retained austenite (7.733 wt%), and the lowest amount (1.977 wt%), which was obtained when the specimens were heated to a temperature of 800 °C and quenched in oil. The Vickers method was employed to conduct micro-hardness testing, and the results demonstrate that hardness values are reduced as heating temperatures increase. Optical microscopy was used to investigate the effects of retained austenite on the microstructure. The results show that bainite and/or martensite phases with a small amount of retained austenite dominate the microstructure at low cooling rates, whereas martensite and retained austenite phases dominate the microstructure at higher heating and cooling rates.

Revealing the effects of martensitic transformation and dislocation slip in austenite on the micromechanical behaviors of a 9Ni steel using crystal plasticity finite element method

Austenite is an extremely important phase that significantly influence the mechanical properties of (austenite + martensite) duplex steels. Two different deformation mechanisms, i.e., dislocation slip and martensitic transformation, can be activated in the austenite upon plastic deformation. However, these two deformation mechanisms make different contributions to the work hardening and flow stress of the austenite which are hardly separated by experimental methods, making it difficult to clarify the effect of austenite on the micromechanical behavior of (austenite + martensite) duplex steels. In this work, the influence of martensitic transformation and dislocation slip in austenite on the micromechanical behaviors is investigated in a model 9Ni steel consisting of austenite and tempered martensite (TM) using the crystal plasticity finite element method (CPFEM). The austenite and fresh martensite (FM) formed within the austenite grain upon deformation process are regarded as a whole named as FM/A island in the CPFEM. To accurately model the rate of martensitic transformation, the martensitic transformation kinetics law used in the CPFEM is developed by relating the number of possible nucleation sites for fresh martensite to the mechanical driving force originating from the resolved shear stress on each transformation system. The material parameters for the TM were determined by micropillar compression tests. Besides, the method for separating and determining the material parameters accounting for dislocation slip in austenite and martensitic transformation by a combination of neutron diffraction and measurements of stress-strain curves and austenite volume fractions is developed and exemplified. The CPFEM simulation results show that the local concentration of equivalent plastic strain and stress triaxiality in the FM/A island can be enhanced by the dislocation slip in austenite but suppressed by the martensitic transformation. In addition, the martensitic transformation has a remarkable effect on strengthening the local concentration of maximum principal stress in the FM/A island.

Enhancing strength and ductility in the nugget zone of friction stir welded 7Mn steel via tailoring austenitic stability

The martensite often appears in the nugget zone (NZ) of friction stir welding (FSW) 7 wt.% Mn steel due to low austenite stability, deteriorating ductility and toughness. In this work, a 7 wt.% Mn steel was subjected to FSW, and preheating was used to tailor the austenitic stability to greatly improve the strength–ductility combination of the NZ. The austenitic deformation behavior and strain hardening mechanism in the NZ were systematically investigated. The microstructure of the as-welded NZ was composed of ultrafine blocky ferrite, austenite, and small amounts of martensite, whereas the as-preheated NZ contained ultrafine blocky ferrite and austenite, and the concentration of Mn in austenite was increased from 8.4 wt.% to 10.7 wt.%. This enhanced the austenitic stability, resulting in a significant increase in the volume fraction of austenite in the as-preheated NZ from 37.3% to 66.4%. The product of strength and elongation (PSE) in the as-preheated NZ increased dramatically from 42.6 GPa% to 67.1 GPa%, depending on a persistent high strain hardening rate (SHR). Multiple strain-hardening mechanisms were revealed. The austenite with enhanced stability can provoke sustained transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP) effects, and massive dislocation multiplication occurs during tension, resulting in strong strain hardening.

High strength-high ductility combination in a low-density medium Mn steel prepared by a highly efficient route

Medium Mn steels are the primary candidates in the fields of automobile, construction machinery et al. due to the advantages of high strength-ductility combination, and low costs. By now, the balance of good performance and high preparation efficiency is still a critical issue to be unsolved, which restricts their further applications. This work designs a novel Al-contained medium Mn low-density steel and explores the effect of a short intercritical-annealing process. The microstructure evolution of multi-scales, especially the austenite characteristics and Mn partitioning behaviors is analyzed, and the relationship between austenite and tensile properties is discussed. The results indicate Al can broaden the annealing processing window and improve the annealing temperature. When annealed at 780 °C, the austenite reverted transformation happens quickly and after annealing for 3 min, the austenite volume fraction maintains stable in the range of 52.4–56.7 vol%, but the morphology and Mn concentration are very different. A large amount of blocky austenite with a coarse size of more than 1 μm and a low Mn concentration of 8–9 wt% forms at the longer annealing time of 20 min, while the austenite almost presents a lath-like shape with a high Mn concentration exceeding 10 wt% at annealing time of 4 min. The tensile properties are closely related to the volume fraction and mechanical stability of austenite, and the sample annealed for 4 min exhibited the best performance with tensile strength of 1192 MPa and total elongation of 33 %, due to its slow TRIP effect.

A Comparative Investigation of Duplex and Super Duplex Stainless Steels Processed through Laser Powder Bed Fusion

The aim of this paper was to compare duplex (DSS) and super duplex stainless steel processed by laser powder bed fusion (LPBF) based on the process parameters and microstructure–nanomechanical property relationships. Each alloy was investigated with respect to its feedstock powder characteristics. Optimum process parameters including scanning speed, laser power, beam diameter, laser energy density, and layer thickness were defined for each alloy, and near-fully dense parts (>99.9%) were produced. Microstructural analysis was performed via optical (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The samples were subjected to stress relief and high-temperature annealing. EBSD revealed the crystallographic orientation and quantified the phases in the as-built and annealed sample conditions. The as-built samples revealed a fully ferritic microstructure with a small amount of grain boundary austenite in the SDSS microstructure. High-temperature solution annealing resulted in the desired duplex microstructure for both alloys. There were no secondary phases present in the microstructure after both heat treatments. Nanoindentation generated nanomechanical (modulus) mapping grids and quantified the nanomechanical (both hardness and modulus) response; plasticity and stress relief were also assessed in all three conditions (as-built, stress-relieved, and annealed) in both DSS and SDSS. Austenite formation in the annealed condition contributed to lower hardness levels (~4.3–4.8 Gpa) and higher plastic deformation compared to the as-built (~5.7–6.3 Gpa) and stress-relieved conditions (~4.8–5.8 Gpa) for both alloys. SDSS featured a ~60% austenite volume fraction in its annealed and quenched microstructure, attributed to its higher nickel and nitrogen contents compared to DSS, which exhibited a ~30% austenite volume fraction.

Effects of Base Metal Preheating on the Microstructure, Mechanical Properties, and Corrosion Resistance of UNS S32750 SDSS Pulsed Nd:YAG Laser Welding

Super duplex stainless steel has a microstructure consisting of equal proportions of austenite and ferrite. However, welding with Nd:YAG pulsed laser results in an imbalanced microstructure that compromises the steel’s properties. This paper studied the effects of preheating the base metal on pulsed Nd:YAG laser welding. Four conditions were evaluated (no preheating and heating at 100 °C, 200 °C, and 300 °C). The analysis included studying the microstructure, microhardness, and corrosion resistance. Preheating the base metals was found to be an effective method for increasing the volume fractions of austenite. The preheated samples showed an improvement in corrosion resistance compared to the untreated sample. The microhardness varied, with the ferrite amount being higher in the untreated sample.

Strengthening mechanisms and microstructural evolution of medium manganese steel under dynamic and static loading

The study analyzes the deformation strengthening mechanisms of medium manganese steel under dynamic and static loading conditions. Different austenite volume fractions (7.4 %, 19.1 %, 30.9 %, 37.7 %) were obtained by varying the heat treatment temperatures (640 °C, 660°C, 680 °C, 700 °C). Results show a linear increase in austenite volume fraction with higher annealing temperature, while carbon content in austenite decreases. Yield strength initially decreases and then increases with annealing temperature. The mechanical properties of all four temperature-tested steels show a clear strain rate dependence in the high strain rate range, with strength increasing with strain rate. Quasi-static conditions no significant strain rate sensitivity. 680 °C test steel's quasi-static deformation is mainly governed by the transformation-induced plasticity (TRIP) effect and dislocation slip in body-centered cubic (bcc) crystals. Dynamic deformation after a strain of 0.14 shows a weakened TRIP effect, and dislocation strengthening in bcc crystals becomes dominant despite a large amount of untransformed austenite. During quasi-static deformation, 700 ℃ test steel exhibits strain hardening due to the TRIP effect at low strains and significant dislocation strengthening in bcc crystals at high strains. Although the TIRP effect is initially suppressed during dynamic deformation, it lasts for a long time. The combined effects of the TRIP effect and martensite dislocation strengthening determine the deformation strengthening mechanisms. Additionally, an optimized Voce model with strain rate strengthening term is proposed. It can well describe the mechanical behavior under dynamic strain rate.

Effects of Pre-Stretching on the Mechanical Behavior of Cold-Rolled 5%Mn Medium Manganese Steel.

Studies about the pre-stretching effect on the mechanical behavior of cold-rolled 5%Mn medium manganese steel have adopted optical microscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction techniques. Results showed that pre-stretching would change the ferrite morphology from massive and lath-like to strip-like. With the pre-stretching increasing from 0% to 14%, the dislocation density and yield strength both grew gradually, which corresponded to growth from 6.49 × 1014 m-2 to 7.98 × 1014 m-2 and growth from 765 MPa to 1109 MPa, respectively. Meanwhile, the austenite volume fraction, elongation and product of strength and elongation were all reduced with the pre-stretch increase. The stabilized retained austenite with pre-stretch delayed the occurrence of the TRIP effect and improved the work hardening rate. As a result, the Lüders band disappeared at 2% pre-stretch and the PLC band vanished from the stress-strain curve at 14% pre-stretch.

The effects of heat-treatment parameters on the mechanical properties and microstructures of a low-carbon dual-phase steel

The austenite decomposition phase transformation in a low-carbon dual-phase (DP) steel is studied as a function of inter-critical annealing parameters: annealing time, annealing temperature, and cooling rate. The austenization kinetics are obtained by dilatometric analyses, water-quenched metallography, and thermodynamic calculations, and the austenite formed at different inter-critical annealing temperatures influences the subsequent formation of secondary phases during continuous cooling. Results indicate that the austenite volume fraction increases with both annealing temperature and time; although their effect on the final microstructure and mechanical properties lessens when the cooling rate decreases to the slow cooling regime below air cooling. Interestingly, the yield strength (YS) values of samples cooled at ∼1 °C/s with sand cooling, are 75∼100 MPa greater than the corresponding values at a rate of ∼6 °C/s with air-cooling. The results indicate that the yield strength is positively correlated with yield-point elongation but negatively correlated with the ultimate tensile strength. The effects of the cooling rate on the mechanical properties can be explained by the formation of Cottrell atmospheres of carbon together with the increase of the pearlite volume fraction. Based on the secondary phase components and strength evolutions, there are four possible outcomes for the different cooling rates: (I) martensite (M); (II) ferrite-martensite (FM); (III) coexistence of martensite and pearlite (MP); and (IV) ferrite-pearlite (FP). Our results reveal that the microstructure-property correlation can be illustrated schematically as a function of cooling rates and can thereby direct the heat-treatment parameters required to obtain desirable mechanical properties.

Experimental and Modeling Study on Austenitizing Process of GCr15 Steel

Abstract The austenitizing process of pearlite during homogenization heat treatment of GCr15 bearing steel was studied using dilatometry. A detailed study was conducted on the relationship between the volume fraction of ferrite, cementite, austenite, and residual cementite during the phase transformation process and the changes in heating temperature and heating rate. An austenizing model for the transformation of pearlite to austenite during homogenization heat treatment was proposed. The interfacial concentration, phase equilibrium, free energy of transformation, and eutectoid temperature between austenite and pearlite were calculated by Thermo-Calc software. The experimental phenomenon of the transition from pearlite to austenite during homogenizing heat treatment was theoretically explained.

Influence of Austempering Temperature on Microstructure and Mechanical Properties of High‐Silicon Carbide‐Free Bainitic Steel

The microstructural evolution of a novel high‐silicon carbide‐free bainitic steel at different austempering temperatures is investigated. The microstructure is evaluated by means of optical and electron microscopy, X‐ray diffraction, microhardness, and nanohardness. Results show a variation in the amount of stabilized retained austenite changing the temperature of the isothermal treatment. In particular, it is observed an increase in the retained austenite volume fraction increasing the temperature up to 350 °C, while further increase leads to a reduction. Moreover, increasing the isothermal holding temperature from 250 °C, through 300, 350, and 370 °C, a progressive bainite coarsening and an increase in the amount of stabilized carbon‐enriched retained austenite are observed. Tensile tests reveal an excellent combination of mechanical properties: mechanical strength in the range 1276–1988 MPa and total elongation 0.18–0.44.

The formation mechanism of austenite in the ultrahigh strength-toughness medium-Mn steel weld via friction stir welding

The medium-Mn steels with high strength and ductility can be used as a potential material in the engineering fields. However, the weld in the medium-Mn steel joint has extremely low ductility due to the existence of full martensite. In this work, a superior tensile strength of 1453 MPa and elongation of 32.7% was obtained in the weld of friction stir welded (FSWed) medium-Mn steel. This should be related to high volume fraction of austenite (24.4%) far higher than that of basal metal (15.1%). The formation mechanism of exceptionally high fraction of austenite was studied based on the transformation kinetics. The volume fraction of austenite in the weld predicted by classical model was only 15.4% much lower than the experimentally measured value, indicating that this model is not suitable for FSW. We applied various assumptions about the diffusivity of Mn in austenite and ferrite during simulation. Consequently, when the Mn diffusivity of austenite and ferrite was multiplied by 4000 and 1500 times, respectively, the simulated austenite volume fraction was well consistent with the experimental results. This was attributed to that the high density of dislocations introduced by strong plastic deformation of FSW promoted the Mn diffusion and the austenitic reverse transformation.

Electron beam additive manufacturing of composite alloy from stainless steel and aluminum bronze: Microstructure and mechanical properties

The authors investigated the microstructure, phase composition and mechanical properties of the steel-bronze composite obtained by electron beam additive manufacturing with simultaneous supply of aluminum bronze wires BrAMc9-2 and stainless steel 06Kh18N9T. X-ray diffraction analysis revealed that the composite contains 25 % (vol.) of aluminum bronze, which leads to the formation of a three-phase structure consisting of γ-Fe, α-Fe and α-Cu grains. According to scanning electron microscopy, the volume fraction of austenite, ferrite and bronze in the steel – 25 % bronze composite is 40.7, 35.7 and 23.6 %, respectively. Unstable conditions of the electron beam additive manufacturing process lead to the release of dispersed particles in austenite and ferrite grains. Dispersion-hardened copper particles with an average particle size of 40 nm, the volume fraction of which is 47 %, are isolated in austenite grains. Dispersion-hardened NiAl particles with a volume fraction of 20 % are isolated in ferrite grains, the average size of which is 44 nm. Transmission electron microscopy data indicate the coherent conjugation of arrays of dispersion-hardened particles with the matrix. Such a composite structure provides an increase in yield strength and tensile strength by an average of 400 and 600 MPa compared with yield strength and tensile strength of 06Kh18N9T steel obtained by electron beam additive manufacturing without bronze addition. Microhardness of the composite is on average 2.2 GPa, which is 0.4 GPa higher than that of 06Kh18N9T steel obtained by electron beam additive manufacturing without bronze addition.

Microstructural-based analysis of the unexpected differences in rolling contact fatigue behavior between SAE52100 and SAE4320

The rolling contact fatigue (RCF) of both a high carbon through-hardening bearing steel (SAE52100) and a low carbon case-hardening bearing steel (SAE4320) have been investigated using RCF. The RCF-life for the SAE4320 steel was found to be ≈7.0 × 107 cycles, about 7 times higher than the RCF-life found for the SAE52100 steel of ≈ 1.0 × 107 cycles. Measurements from fracture surfaces of specimens tested to failure in rotatory bending fatigue tests revealed an average inclusion size of 27.3 μm for SAE52100, and 38.2 μm for SAE4320, indicating a lower purity for case-hardening bearing steel, and suggesting SAE4320 should have a shorter RCF-life, contrary to the measured RCF-lives. However, the carbide size, the prior austenite grain size and the retained austenite (RA) volume fraction for SAE4320 were measured as 0.20 μm, 10.8 μm and 25.0%, respectively, all of which are better than those for SAE52100 (0.59 μm, 16.1 μm and 3.1%). The enhanced RCF-life can be understood as a combined result of the detrimental effects of inclusion size and the beneficial contribution of the refined carbide and prior austenite grain size and of the increased austenite volume fraction. Based on this study, it is proposed that a double refinement of both carbide and prior austenite grain size, together with control of the austenite fraction, may be a promising way to extend RCF-life without the requirement for further inclusion refinement during the fabrication high-performance bearing steels.

Influence of partitioning treatment on microstructure and mechanical properties of an alloyed ductile iron austempered at different temperatures

AbstractThe present study was conducted to uncover effects of partitioning treatment on Cu–Ni–Mo alloyed ductile iron (DI) austempered at different temperatures. For this purpose, the DI samples, produced via sand casting, were austenitized at 900 °C for 60 min, followed by austempering at the temperatures of 275–325–375 °C for 120 min and afterwards a partitioning treatment was applied at 200 °C for 15 min. In the characterization studies, dilatometer, image analysis, JMat-Pro, mechanical tests, XRD, optical microscope, and scanning electron microscope (SEM) equipped with EBSD detector were utilized. Characterization studies showed that the effects of partitioning treatment were directly correlated with austempering temperature and high carbon austenite volume fraction changed in the range of 19.48–35.45%. That redistribution of carbon (C) between bainitic ferrite and high carbon austenite occurred, in turn, the carbon content of high carbon austenite increased with the partitioning treatment irrespective of austempering temperature were uncovered. Furthermore, the partitioning treatment considerably changed the grain morphologies of both high carbon austenite and banitic ferrite. As a consequence of these microstructural differences, the highest tensile strength of 1489.2 MPa was established in the sample austempered at 275 °C and partitioned at 200 °C, whereas the highest ductility of 5.61% acquired at the austempering temperature of 375 °C.

Effect of austenite fraction and stability on strength-hardening-ductility in additively manufactured 17-4 PH stainless steel containing nitrogen

Additively-manufactured (AM) 17-4 precipitation-hardening (PH) martensitic stainless steel (SS) built from nitrogen-atomized powder often retains a large volume fraction of austenite. The retained austenite lowers the yield strength compared to both wrought and AM 17-4 SS built from argon-atomized powder, hindering its use in many applications. However, retained austenite allows for high work hardening and high ductility through deformation-induced martensitic transformation (DIMT). This work systematically investigates the influence of various heat treatments on the volume fraction and stability of the retained austenite from tensile loading in AM 17-4 SS containing a mass fraction of 0.13% nitrogen (AM 17-4N SS). Synchrotron-based high-energy x-ray diffraction (HEXRD) is used to quantify the austenite volume fraction resulting from the heat treatments and the extent of DIMT in tensile specimens loaded to various plastic strains and specimens loaded to fracture. We show that by altering the volume fraction and stability of the retained austenite in AM 17-4N SS using different heat treatments, the DIMT process can be utilized to vary the strength, work hardening, and ductility, thus enabling its use in a wide range of applications. The AM 17-4N SS is also shown to meet or exceed the peak aged requirements for wrought 17-4 SS with yield strength (YS) of >1200 MPa, an ultimate tensile strength (UTS) of >1500 MPa, and a uniform elongation of ≥13% while retaining ≈ 20% volume fraction of austenite.

Time-Dependent Evolution of Volume Fraction and Stability of Retained Austenite in a Hot-Rolled and Intercritically Annealed Al-Alloyed Medium-Mn Steel

The development of superior mechanical properties in medium-Mn requires the optimization of microstructural parameters such as retained austenite (RA) stability, volume fraction, and morphology. The present work explores the possibility of using a continuous annealing approach instead of conventional batch annealing to perform an intercritical annealing (IA) treatment in a hot-rolled strip of an Al-alloyed 5Mn steel. Dilatometric studies were performed at a temperature of 680 ºC with soaking times ranging from 1 to 300 min to follow the microstructural changes as a function of time. The microstructures thus obtained were thoroughly characterized by means of X-ray diffraction, SEM and TEM, TEM-EDS microanalysis and EBSD phase and orientation maps. It was observed that with increasing soaking times, the volume fraction of retained austenite gradually increases, albeit at the cost of its stability. The comparison of martensite start temperatures (Ms) based on the chemical composition of austenite at 680 ºC with that experimentally obtained at higher process temperature revealed the effect of the grain size on the reduction of RA stability for longer process times. Accordingly, mechanical tests results showed that the yield stress, tensile strength and hardness decrease with an increase in the IA soaking time.

Correction of Phase Balance on Nd:YAG Pulsed Laser Welded UNS S32750 Using Cobalt Electroplating Technique

Super-duplex stainless steel (SDSS) shows high mechanical and corrosion resistance because of the balanced structure of austenite and ferrite. However, maintaining this phase ratio after welding is a challenge. The use of austenite stabilizing components is recommended to balance the microstructure. The addition of alloying elements presents a challenge because of the characteristics of Nd:YAG pulsed laser welding. An approach, which has proven to be effective, is to use metal electroplating to prepare the surfaces of the mechanical SDSS components that will be welded, therefore promoting the phase balance in the fusion zone. While the effects of metals such as nickel as an austenite stabilizer are well recognized, cobalt’s effects require more research. The present work investigated the influence of the use of cobalt addition in the joining process by preliminary electroplating on UNS S32750 SDSS Nd: YAG pulsed laser welding, specifically regarding microstructure and microhardness. Three conditions were investigated, changing the thickness of the deposited cobalt layer. The addition of cobalt modified the morphology and increased the volume fraction of austenite. An austenite volume fraction of around 48% was obtained using a 35 μm thick cobalt coating. The microhardness was affected by austenite/ferrite proportions. The microhardness dropped from about 375 HV to 345 HV as the cobalt layer’s thickness rose, being similar to that of the base metal. The effect of cobalt as an austenite stabilizer was observed, and the cobalt electroplating technique was effective to correct the phase balance on UNS S32750 laser welding.