Austenitic Steel Research Articles

Effects of Thermal Aging on the Oxidation Behavior of 316L Austenitic Steel in 600 °C Supercritical Fired Boiler: Mechanism Based on Interface Features

Effects of Thermal Aging on the Oxidation Behavior of 316L Austenitic Steel in 600 °C Supercritical Fired Boiler: Mechanism Based on Interface Features

Hardfacing of GX40CrNiSi25-20 cast stainless steel with an austenitic manganese steel electrode

Abstract To enhance the wear and corrosion resistance of engineering components, various surface modification techniques have been devised. Among these, arc welding processes employing specialized electrodes offer relatively straightforward methods with low production costs for hardfacing applications. This paper focuses on the hardfacing process using pulsed current arc welding to reinforce cast austenitic steel structural components, aiming to prolong their lifespan. Typically, hardfacing coatings utilize Fe, Ni, and Co-based alloys. Among these, Fe-based alloys, such as manganese austenitic alloys employed in our experiments, are favored for their robust mechanical work hardening capacity, resulting in significant hardness enhancements (from 186–219 HV5 in the as-deposited layer to 468–492 HV5 after mechanical work hardening) under intense wear and impact conditions. The innovation of the hardfacing process developed in this study lies in utilizing a universal TIG source adapted for manual welding with a covered electrode in pulsed current mode. This hardfacing technique can be applied to both worn components in operation and new ones before being put into service, thereby ensuring long-term durability and reducing maintenance costs.

Microstructure and Mechanical Properties of Layered Billets from Various Grades of Austenitic Steels Grown by Additive Electric Arc Welding

Microstructure and Mechanical Properties of Layered Billets from Various Grades of Austenitic Steels Grown by Additive Electric Arc Welding

Achieving Well‐Balanced Strength and Ductility in Warm‐Rolled Fe–30.5Mn–8Al–1.0C Lightweight Austenitic Steels via Aging Treatment

Achieving Well‐Balanced Strength and Ductility in Warm‐Rolled Fe–30.5Mn–8Al–1.0C Lightweight Austenitic Steels via Aging Treatment

The adverse effect of grain refinement on hydrogen embrittlement in a high Mn austenitic steel

This study presents a novel observation wherein the reduction in grain size (GS) from 20 μm to 1 μm in austenitic steel adversely affects hydrogen embrittlement (HE). The findings indicate an increase in total absorbed hydrogen with grain refinement when subjected to cathodic hydrogen charging. The results demonstrate that even with grain refinement to 1 μm, the primary mode of hydrogen damage remains intergranular, with a significant increase in relative elongation loss (REL%). This phenomenon is attributed to the early nucleation of intergranular hydrogen-induced cracks (HICs) and the accelerated propagation rates of HICs, leading to local stress increments and rapid alloy failure. The accelerated development of HICs is ascribed to the impact of grain refinement on intensified normal stress exerted on grain boundary planes, as well as the suppression of ε-martensite and its positive effect on crack arresting. Besides the enhanced degradation rate of the hydrogen-affected area (HAA) due to grain refinement, the higher ratio of HAA to the entire cross-sectional area was identified as a crucial factor contributing to rapid failure and the inverse effect of grain refinement on HE resistance.

Effect of H2S on the corrosion behavior of austenitic and martensitic steels in supercritical CO2 at 550 °C and 20 MPa for Brayton cycle system

Corrosion of alloy materials significantly influences the stability and efficiency of the supercritical carbon dioxide (S-CO2) Brayton cycle. In this study, we investigated the corrosion behavior of the austenitic alloy SP2215 and the martensitic alloy X19CrMoNbVN11-19 (X19) in S-CO2 at 550°C and 20 MPa. The effect of impurities, H2S, on corrosion behavior was studied. After 900 hours, SP2215 formed a 1.1 μm thick oxide layer (Cr2O3). X19 formed a loose and porous double oxide layer of 4.1 μm (outer: Fe3O4, inner: FeCr2O4). After H2S doping, SP2215 had an oxide layer of 6.2 μm (FeS, SiO2, and Cr2O3), while X19 was 9.8 μm (outer: Fe3O4, SiO2, FexSy and Fe2O3, inner: FeCr2O4, Fe2SiO4 and Cr2S3). Metal sulfides formed and the corrosion layer thickened. This indicates that H2S not only changes the corrosion mechanism but also aggravates the corrosion. However, the corrosion of CO2 is dominant. SP2215 has better corrosion resistance than X19.

Temperature dependence of the deformation behavior and mechanical properties of a Fe–Mn–Al–C low-density steel for cryogenic application

The temperature dependence of the deformation behavior and mechanical properties of a Fe–20Mn–6Al-0.6C-0.15Si austenitic low-density steel was studied by tensile test and Charpy impact test at −196 °C, −77 °C and room temperature (RT), followed by microstructure analyses. The results indicate that the decreased tensile temperature, which is corresponding to reduced stacking fault energy (SFE), promotes the planar glide of dislocations. This led to larger fraction of low-angle grain boundaries (LAGBs) at lower tensile temperature. Consequently, both the tensile strength and elongation were improved as temperature decreased. At lower impact test temperature, the load and energy of crack initiation were larger, indicating a higher resistance to crack initiation. However, the transition from stable to unstable crack propagation occurred more rapidly at lower temperature, resulting in lower crack propagation energy and reduced resistance to crack propagation. This is because less region experienced planar glide. Due to the rapid unstable crack propagation, the Charpy absorbed energy at −196 °C was the lowest. The smaller fracture surface area, larger fibrous zone and more obvious ductile fracture characteristics in radial zone suggest that the toughness is better at higher temperature. Additionally, the presence of secondary cracks at RT delayed fracture, therefore benefitting toughness.

Monitoring of relative magnetic permeability variation during cyclic bending testing of austenitic steel grade 10Kh18n10t samples

Cyclic bending testing of austenitic chromium-nickel steel grade 10Kh18N10T samples was carried out. Evalution of relative magnetic permeability showed its noticeable increase when the samples became fractured. This increase is related to deformation martensite appearance. Additional experiment showed, that deformation martensite formation starts before the actual destruction of the sample.

Trapping and diffusion in high-pressure hydrogen charged CoCrFeMnNi high entropy alloy compared to austenitic steel 316L

High entropy alloys (HEAs) have attracted considerable research attention as potential substitute materials for austenitic steels in high-pressure hydrogen environments. The corresponding hydrogen absorption, diffusion and trapping has received less scientific attention. Therefore, the CoCrFeMnNi-HEA was investigated and compared to an austenitic steel AISI 316L. Both were subjected to high-pressure hydrogen charging at 200 bar and 1000 bar. Thermal Desorption Analysis (TDA) was used to clarify the specific desorption behavior and hydrogen trapping. For this purpose, the underlying TDA spectra were analyzed in terms of a reasonable peak deconvolution into a defined number of peaks and the activation energies for the respective and predominant hydrogen trapping sites were then calculated. Both materials show comparable hydrogen diffusivity. However, there were significant differences in the absorbed hydrogen concentrations at both charging pressures. The calculated activation energies suggest strong hydrogen trapping in the CoCrFeMnNi-HEA.

Effect of materials and process parameters on machinability of stainless steels

Stainless steels, recognized for their corrosion resistance attributed to a minimum of 11 % Chromium, encompass a variety of alloys with distinctive microstructures and properties. Machinability significantly varies among these alloys. Austenitic steels such as SS303 and 304 present challenges, demonstrating poor surface finish and high power consumption. This study, employing a central composite design, investigates the machinability of AISI 303, 304, 316, AISI 416, and AISI A36. Turning tests with PVD TiAlN-coated inserts revealed optimal parameters for cutting speeds (90.5256–244.411 m/min), feed (0.0635–0.4826 mm/rev), and depth (0.00016–0.00187 m.). Surface finish analysis identified AISI 316 as the best, closely followed by AISI 303. From a power consumption standpoint, AISI 303 performed the best, and concerning fragmented chip morphology, AISI 303 also excelled. The superior performance of AISI 303 is attributed to 2 % Manganese and 0.15 % Sulfur, proving to be the most effective combination compared to the other four steels, resulting in a higher percentage of MnS2, optimal for improving machinability. The depth of cut emerges as the most influential factor affecting dimensional accuracy. These findings hold practical significance in the selection of stainless steels and corresponding process parameters across various industries, including the manufacturing of heavy earthmoving equipment. By shedding light on the optimal composition and machining conditions, this study contributes valuable insights for enhancing performance and efficiency in stainless steel applications.

Role of intermetallic networks in developing high-performance austenitic steel

Role of intermetallic networks in developing high-performance austenitic steel

Tensile and cracking behavior of thin-walled 316Ti austenitic steel after exposure to 550 °C lead-bismuth eutectic with different oxygen concentration

The corrosion evolution of 316Ti steel in 550°C lead-bismuth eutectic (LBE) with oxygen concentrations (Co) of 5×10-6 wt.% and 5×10-8 wt.% and their impact on the tensile behavior were investigated in this study. The steel primarily underwent oxidation at Co of 5×10-6 wt.%, slightly influencing the tensile strength and elongation of specimen within 1000 hours exposure. In contrast, the structural integrity and tensile strength of specimen were significantly deteriorated at Co of 5×10-8 wt.% where the steel mainly experienced dissolution corrosion. The cracking behaviors of oxide layer and ferrite layer, and their influences on the failure of thin-walled specimen were discussed. Special concerns should be raised on the detrimental effect of localized corrosion, such as intergranular oxidation, LBE-wetted precipitate bands and dissolution pits, since cracks are expected to initiate easily in these zones and propagate into steel matrix under tension, potentially leading to the premature failure of thin-walled components.

Microstructure and corrosion property evolution of a surface-nanostructured 15-15Ti austenitic steel during immersion in liquid LBE at 550 °C

This study investigated the compatibility of surface-nanostructured 15-15Ti austenitic steel in 550 °C LBE with an oxygen concentration of 5 × 10−7 wt.% for various exposure durations (759, 1638, 2404, and 3012 hours). The results demonstrate that the grain size was reduced from 33.50 μm to the nano-scale after shot-peening (SP), achieving 17.62, 15.44, and 14.25 nm under SP pressures of 0.06, 0.15 and 0.25 MPa, respectively. The untreated steel experienced severe oxidation and dissolution corrosion, whereas the surface-nanostructured steel exhibited only mild oxidation and was resistant to dissolution corrosion. The enhanced corrosion resistance of surface-nanostructured steel is attributed to the higher protectiveness of the Cr-rich spinel layer and the less defective Ni-rich layer beneath it. Recrystallization occurred exclusively in the Ni-rich region, while the deformed steel underwent recovery during exposure. The thickness of the recrystallization layer was 2.9 μm at 759 h, increased to 8 μm at 1638 h, and remained stable thereafter. The size of recrystallized grains in SP-samples processed under pressure of 0.06 MPa and 0.15 MPa was approximately 2.92 μm, whereas it was about 1.32 μm for 0.25 MPa processed sample.

Bending fatigue behavior of metastable and stable austenitic stainless steels with different surface morphologies

AbstractThe surface morphology has a significant influence on the fatigue behavior of components. For austenitic stainless steels (ASSs), this issue is even more pronounced due to their metastability. Based on the complex deformation mechanisms of metastable ASSs, which include dislocation slip, deformation twinning, and deformation‐induced martensitic phase transformation, the metastable stainless steel AISI 347 was investigated in this study together with the stable AISI 904L as a reference material. Four‐point bending fatigue tests with load ratio R = 0.1 and testing frequency f = 10 Hz at ambient temperature were carried out on specimens with five technically relevant surface morphologies: mechanical polished, milled, microshot peened, laser shock‐peened, and ultrasonic modified. Systematic material characterizations were carried out to elucidate the crucial role of surface roughness and deformation‐induced α′‐martensite in the fatigue behavior of both metastable and stable materials. While surface roughness is a well‐known key factor in conventional fatigue cases, deformation‐induced martensite layers implemented by various surface modification methods were proven to improve the fatigue life in metastable austenitic steels, opening new perspectives to extend the lifetime of ASS components.

The effect of trace vanadium addition on mechanical properties, microstructure and austenite phase characteristics in a 3.9% Al-Delta TRIP steel

This study aimed to examine the effect of adding 0.12 wt% vanadium on the properties of delta TRIP steel through microstructural and mechanical investigations. The delta ferrite phase was observed in all annealing temperatures and samples. Carrying out bainitic transformation at 350 °C for 6, 10, and 15 min resulted in the stability of the austenite phase and the formation of ferritic bainite phase after heat treatment. The presence of vanadium led to the formation of MC precipitate phases and reduced the remaining austenite percentage from 14% to 6% by weight in the heat-treated sample. The low percentage of austenite in vanadium-containing steel has weakened the TRIP effect in strengthening. On the other hand, the presence of MC precipitates has compensated for the reduction in strength from the TRIP strengthening process through precipitation hardening and reducing the grain size of the delta ferrite phase. The resulting properties (UTS: 866 MPa and El: 41.3%) have led to the creation of a formability index of 35 GPa% in vanadium-containing steel, which is better than the mechanical properties (UTS: 857 MPa and El: 37.4%) and the formability index of vanadium-free steel (32 GPa%). These factors make this steel a suitable option for automotive industry applications. Based on these features make this steel a suitable candidate for automotive industries. Microstructural investigations revealed that the addition of vanadium reduces the grain size of the delta ferrite phase. Typically, the austenite phase forms around the ferritic bainite phase and delta ferrite grain boundaries. During tensile testing, it transforms into martensite through the TRIP process.

Technological support of workpiece surface quality based on local cryogenic impact during processing of austenitic steels

Technological support of workpiece surface quality based on local cryogenic impact during processing of austenitic steels

Aluminide Coatings by Means of Slurry Application: A Low Cost, Versatile and Simple Technology

The present study focused on demonstrating the versatility of the slurry deposition technique to produce aluminide coatings to protect components from high-temperature corrosion in a broad temperature range, from 400 to 1400 °C. This is a simpler and low-cost coating technology used as an alternative to CVD and pack cementation, which also allows the coating of complex geometries and offers improved and simple repairability for a lot of industrial applications, along with avoiding the use of non-hazardous components. Slurry aluminide coatings from a proprietary water-based-Cr6+ free slurry were produced onto four different substrates: A516 carbon steel, 310H AC austenitic steel, Ti6246 Ti-based alloy and TZM, a Mo-based alloy. The resulting coatings were thoroughly characterised by FESEM and XRD, mainly so that the identification of microstructures and appropriate phases was reported for each coating. The importance of surface preparation and heat treatment as key parameters for the coating final microstructures was also evidenced, and how those parameters can be optimised to obtain stable intermetallic phases rich in Al to sustain the formation of a protective Al2O3 oxide scale. These coating systems have applications in diverse industrial environments in which high-temperature corrosion limits the lifetime of the components.

Initiation of the Shape Memory Effect by Fast Neutron Irradiation

The band sample of austenitic steel 0.3C–13Cr–10Mn–3Si–1V was cold deformed to a shape of circular arc with a deflection of 3 mm and then irradiated by fast neutrons with a fluence of 6×1019 cm–2 in the vertical wet channel of the IVV-2M reactor at a temperature of 80 °C. This material belongs to the class of the stainless manganese austenitic steels with the shape memory effect (SME). The neutron irradiation was initially supposed to lower the SME upon the further heating in comparison with the reference sample. But instead, the SME appeared immediately under irradiation showing a decrease in the deflection of about 21 %. Check experiments confirmed that the lower limit of the SME in this material is 120 °C with its absence at 80 °C. This allows us to assert that the observed effect is the result of the neutron irradiation.

Influence of hydrogen on deformation and embrittlement mechanisms in a high Mn austenitic steel: In-Situ neutron diffraction and diffraction line profile analysis

Austenitic steels have relatively high resistance to hydrogen embrittlement and play a critical role in hydrogen service applications. In particular, high Mn austenitic steels are considered economically viable alloy alternatives for these applications. The current study employed in-situ and ex-situ neutron diffraction techniques combined with diffraction line profile analysis (DLPA) to investigate the influence of hydrogen on deformation and embrittlement mechanisms in a high Mn (approximately 30 wt pct) austenitic steel. Investigation using both neutron diffraction and electron backscatter diffraction revealed the presence of extensive deformation twins and stacking faults within the steel microstructure after tensile deformation in the non-charged condition. These microstructural features suggest planar deformation behavior, which is expected from the relatively low stacking fault energy (SFE) of the alloy (approximately 29 mJ/m2). Hydrogen pre-charging resulted in apparent increases in both dislocations and stacking faults, contributing to macroscopic hardening and embrittlement mechanisms. Overall, numerical parameters obtained through neutron DLPA were used to elucidate the underlying mechanisms associated with hydrogen effects on the mechanical behavior, i.e. macroscopic strengthening, strain hardening rate, and embrittlement.

High nitrogen steels produced by laser powder bed fusion – Processability of an additivated austenitic steel powder

The additivation of conventional metal powders allows the expansion of the range of materials and alloys suitable for powder bed fusion additive manufacturing of metals. The combination of material properties, the improvement of currently used powder properties, and their processability are the focus of this technique. This work investigates the influence of the additivation of Si3N4 particles to X2CrNi18–9 austenitic stainless-steel powder on the resulting powder properties and processability by PBF-LB/M. The aim is to process a composite material consisting of a steel matrix in which retained Si3N4 particles are embedded. A subsequent heat treatment by hot isostatic pressing should allow dissociation of Si3N4 and the associated nitrogen diffusion into the austenitic matrix to produce a high nitrogen steel (HNS). Despite some degradation in powder properties, as indicated by a decrease in the Hausner ratio from 1.24 to 1.15, PBF-LB/M successfully produced samples in a process window of 30–36 J/mm3.