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We measured the austenitic FeCr18Ni12.5 stainless steel Hugoniot as a function of crystallographic direction to approximately 60 GPa. We shock-compressed FeCr18Ni12.5 samples oriented along ⟨ 100 ⟩ , ⟨ 110 ⟩ , and ⟨ 111 ⟩ to mean stresses ranging 30.5–58.1 GPa via Ta plate impact in a large-bore powder gun and measured the free-surface velocities with laser interferometry. We unambiguously observed the largest post-shock free-surface velocity along ⟨ 100 ⟩ in each experiment, which consequently produced the lowest shock velocity along that orientation. However, the propagation of experimental uncertainties through the impedance matching scheme used to compute the shock velocity produced sufficient uncertainty overlap to preclude definitive conclusion of Hugoniot anisotropy. [ABSTRACT FROM AUTHOR]

This work presents the effect of process parameters viz., current, speed, gas flow rate, and arc gap on characteristics of austenitic stainless steel SS304 bead-on plate welds and determines the optimal combination of parameters. Experiments were conducted as per Taguchi L9 orthogonal array and the effect of process parameters on weld bead profile, penetration depth, bead width, microstructure, and hardness were analysed. An optimum value was obtained for each process parameter to maximize penetration depth and hardness and minimize the bead width and HAZ. It was found that heat input per unit weld length is crucial in controlling the weld characteristics. Stronger inward flow patterns were responsible for beads with a narrower width and deeper penetration because of higher heat input however, excessive heat input was detrimental and produced wider beads and HAZ. Current and speed were most dominant in deciding weld characteristics than gas flow rate and arc gap. Predicted results are in close agreement with the confirmation experiments. [ABSTRACT FROM AUTHOR]

Microstructural evolutions and cryogenic mechanical properties of AISI 904L superaustenitic stainless steel were studied for the first time and compared with those of metastable AISI 304L and 316L austenitic stainless steels. The temperature-dependencies of these properties were critically discussed and correlated to the microstructures, focusing on the solid solution strengthening, transformation-induced plasticity (TRIP), and twinning-induced plasticity (TWIP) effects. The 904L alloy showed an extraordinary cryogenic strength-ductility synergy with excellent work-hardening behavior. [ABSTRACT FROM AUTHOR]

For this study, the researchers aimed to dissimilar weld the Nickel-based superalloy Inconel 718 (IN 718) with austenitic stainless steel 304L (ASS 304L) using the gas tungsten arc welding (GTAW) technique and Nickel-based filler IN 82 (ERNiCr-3). In order to examine the weld microstructures, we utilized optical microscopy (OM) and field emission scanning electron microscopy (FESEM) with energy-dispersive spectroscopy (EDS) to identify any segregation present in various weld zones. Through optical and FESEM analyses, it was revealed that the base metals (BM) exhibit an austenitic character. The IN 718 BM matrix contains dispersed γ′ and γ″ strengthening precipitates within the Nickel matrix. On the other hand, the ASS 304L BM displayed a unique austenitic microstructure characterized by twins features. The weld metal exhibited solidification grain boundaries (SGBs), migrated grain boundaries (MGBs), and distinct dendritic microstructures that had an impact on the properties of the weld. Through extensive analysis and mapping of the IN 82 weld zone, it was discovered that interdendritic regions contain carbides of Nb, Cr, and Ti. In addition, there were Unmixed zone (UZ) areas between the IN 82 filler and the base materials on both sides of the weld zone, appearing as islands and beaches. The texture of the different weld zones was evaluated using electron backscattered diffraction (EBSD) analysis. Additionally, the presence of a notable level of strain within the weld metal grains was observed through Kernel average misorientation (KAM) micrographs. Fractures were observed in the IN 82 weld zone, indicating that it is the weakest area in the IN 718/ASS 304L dissimilar weld at room temperature, according to the outputs of the tensile tests. The micro-hardness profile showed substantial hardness values in the weld zone, which can be attributed to the appearance of a diverse microstructure and additional precipitates. At room temperature, the recorded average tensile strength of the dissimilar weld joint was 626 MPa. In addition, experiments were carried out at high temperatures of 550 °C, 600 °C, and 650 °C to measure the tensile strength. In the high-temperature tensile tests, it was observed that the IN 82 weld zone exhibited higher tensile strength compared to the ASS 304L BM. Interestingly, the high temperatures tensile specimens failed in the 304L BM. The Charpy impact toughness test was performed with notches at ASS 304L HAZ, IN 718 HAZ, and the weld center. Using the deep hole drilling (DHD) technique, we were able to quantify residual stress and identify the location of the highest tensile residual stress, which was found to be 3 mm from the weld surface. [ABSTRACT FROM AUTHOR]

The thermal-mechanical processing (TMP) for twin-induced grain boundary engineering (GBE) generally adopts a small amount of cold deformation and subsequent annealing at solution temperature of austenitic stainless steels. The nucleation mechanism during the TMP of GBE is essential to the understanding of the evolution of grain boundary character distribution (GBCD). The mechanism for recrystallization nucleation is investigated in a 316L austenitic stainless steel which was subjected to short-time annealing at solution-annealing temperature after 5–10 pct tensile deformation. A total of 22 recrystallization nuclei were found, and the analyzing of the orientation relationships between the nuclei and nearby deformed grains revealed that most of the nuclei are formed following the strain-induced boundary migration (SIBM) mechanism. The formation of highly twinned grain-clusters as the typical feature of GBE microstructure is a result of extensive multiple twinning starting from every single nucleus. Low nucleation density is more important than how the nucleus forms during GBE. A portion of the recrystallization front boundaries outside the clusters expanded into the deformation microstructure more extensively than the others. However, the growth advantage does not have an obvious correlation with the misorientation of these recrystallization front boundaries. [ABSTRACT FROM AUTHOR]

Dissimilar metal welded (DMW) joint plays a crucial role in constructing and maintaining ultra-supercritical (USC) nuclear power plants while presenting noteworthy environmental implications. This research examines different welding techniques utilized in DMWJ, specifically emphasizing materials such as P91. The study investigates the mechanical properties of these materials, the impact of alloying elements, the notable difficulties encountered with industrial materials, and the concept of buttering. The USC nuclear power plants necessitate welding procedures appropriate for the fusion of diverse metal alloys. Frequently employed methodologies encompass shielded metal arc welding (SMAW), gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), and flux-cored arc welding (FCAW). Every individual process possesses distinct advantages and limitations, and the choice of process is contingent upon various factors, including joint configuration, material properties, and the desired weld quality. The steel alloy known as P91, which possesses high strength and resistance to creep, is extensively employed in advanced ultra-supercritical (AUSC) power plants. P91 demonstrates exceptional mechanical characteristics, encompassing elevated-temperature strength, commendable thermal conductivity, and notable resistance against corrosion and oxidation. The presence of alloying elements, namely chromium, molybdenum, and vanadium, in P91, is responsible for its improved characteristics and appropriateness for utilization in (AUSC) power plant applications. Nevertheless, the utilization of industrial materials in DMW joint is accompanied by many noteworthy concerns, such as the propensity for stress corrosion cracking (SCC), hydrogen embrittlement, and creep deformation under high temperatures. The challenges mentioned above require meticulous material selection, process optimization, and rigorous quality control measures to guarantee the dependability and sustained effectiveness of DMW joint. To tackle these concerns, a commonly utilized approach referred to as buttering is frequently employed. When forming DMW joint in nuclear facilities, it is customary to place a buttering coating on ferritic steel. This facilitates the connection between pressure vessel components of ferritic steel and pipes of austenitic stainless steel. The primary difficulty in DMW joint manufacturing is in mitigating the significant disparity in material characteristics resulting from carbon migration and metallurgical alterations along the fusion interface between ferritic steel and austenitic stainless steel. The process of buttering entails the application of a compatible filler material onto the base metal before the deposition of the desired weld metal. The intermediate layer serves as a mediator, enhancing the metallurgical compatibility, diminishing the probability of fracture, and enhancing the overall integrity of the joint. Buttering is still a new research area with a wide scenario of scope in terms of development, which could revolutionize developing high-temperature. These long-term sustainable joints could serve under critical conditions like AUSC power plants and reduce CO2 emissions by increasing the overall efficiencies of the systems. [ABSTRACT FROM AUTHOR]

The carbon steel pipe line of the dehydrogenation tail gas system in a certain styrene unit has a thinning rate of 55.51% and a corrosion rate of up to 5.29 mm/a after one year of use, which restricts the long-term stable operation of the plant. The corrosion of the dehydrogenation tail gas carbon steel pipeline was inspected through electromagnetic eddy current scanning, ultrasonic thickness measurement, and macroscopic inspection. The impact of corrosive medium, process operating parameters, on-site pipeline location and material on pipeline thinning in the dehydrogenation tail gas system was analyzed. The results indicate that the localized corrosion and thinning of the dehydrogenation tail gas carbon steel pipeline are caused by a combination of carbon dioxide corrosion and erosion corrosion under certain temperature and pressure. To alleviate corrosion issues, it is recommended to re-evaluate the process operating conditions of the dehydrogenation tail gas system, add cooling equipment before the dehydrogenation tail gas compressor, or upgrade the pipeline material to 304 austenitic stainless steel. Or consider adding corrosion inhibitors to the dehydrogenation exhaust system. At the same time, regular electromagnetic eddy current scanning or ultrasonic thickness measurement should be carried out to monitor the relevant pipelines and prevent leaks in a timely manner. [ABSTRACT FROM AUTHOR]

This study explores the impact of microstructural features on fatigue crack initiation in poly‐crystalline materials, emphasizing hydrogen‐induced complexities. Grain anisotropy, misorientations, grain size variations, and elastic–plastic inhomogeneities concentrate stress at grain boundaries, making them susceptible to crack initiation during fatigue loading. The presence of hydrogen compounds this process, due to complications of characterization of local hydrogen content and activating embrittling mechanisms. Building upon a model for nickel, this research investigates 316L austenitic stainless steel specimens with varying grain sizes, both uncharged and hydrogen‐charged. In situ low‐cycle fatigue loading experiments establish correlations between fatigue crack initiation and microstructural features. The study reveals specific combinations of features crucial in the initiation process, undergoing alterations in the presence of hydrogen. A proposed qualitative model links microstructural features with accumulated plastic shear strain during fatigue and prevalent hydrogen embrittlement mechanisms like hydrogen‐enhanced local plasticity and hydrogen‐enhanced decohesion. Highlights: The effects of hydrogen on fatigue crack initiation (FCI) sites in stainless steel 316L are studied.Two different grain sizes were analyzed by in‐situ scanning electron microscopy (SEM) and electron back‐scattered diffraction (EBSD) and high‐resolution digital image correlation (HR‐DIC).Hydrogen‐assisted FCI is correlated with initial features of the microstructure.A model is proposed linking FCI with microstructure and accumulated plastic shear strain. [ABSTRACT FROM AUTHOR]

Creep life prediction of component materials exposed to air and liquid sodium environments is critical to ensure the safe operation and structural integrity of a sodium‐cooled fast reactor. In this paper, a method for predicting the creep life of a wide range of austenitic stainless steels in air and liquid sodium was proposed based on a physics‐informed neural network. Based on the established datasets for sodium corrosion rates and creep life in air and liquid sodium, the predictive performance of physical equations, conventional machine learning models, and the proposed model were assessed. Subsequently, a data‐driven creep life assessment framework was established, providing insight into the engineering application of machine learning methods in high‐temperature structure assessment. The results show that the creep fracture of austenitic stainless steel is accelerated by liquid sodium corrosion. The proposed physics‐informed neural network exhibits enhanced suitability and accuracy for predicting the sodium corrosion rate and creep life than physical equations and conventional machine learning methods. Highlights: A data‐driven creep life prediction method for metals under corrosion was proposed.New physical constraint and feature have been proposed based on domain knowledge.The excellent predictive performance of proposed method has been validated.Data‐driven creep assessment under environment effects has been proposed. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of nitrogen content on the tribological behavior of 316L (N) stainless steel at three different nitrogen levels: 0.07, 0.11 and 0.22 wt. percent. AISI 316L (N), an austenitic stainless steel, is the primary structural material used in sodium-cooled prototype fast breeder reactors (PFBR). Wear tests were conducted using a pin-on-disc tribometer, with a sliding velocity of 0.8 m/s and a normal load of 40 N, over a sliding distance of 1000 m. The experiments were carried out against an Inconel 718 counter face material at four different temperatures: room temperature, 200 °C, 400 °C and 550 °C. The dry sliding wear tests were performed in a vacuum of 10–6 torr to simulate wear in liquid sodium. The investigation covered the properties of the three grades of stainless steel, including microstructure, hardness, X-ray diffraction (XRD), specific wear rate, wear resistance and wear coefficient. This study also compared three different wear models a weight loss model, an ASTM model, and geometric models highlighting the reported anomalies. Scanning electron microscope (SEM) photographs of the worn surfaces were used to assess the severity and mode of wear. It was discovered that wear resistance decreases as temperature increases due to the material's thermal softening, and that the stainless steel with 0.07 wt% nitrogen exhibited the best wear resistance among the tested compositions. [ABSTRACT FROM AUTHOR]

In the process of directed energy deposition (DED), the grain structure of the deposited samples is determined by two aspects. The first is the initial solidification grain structure; the second is the effect of the upper thermal cycle on the solidified grain structure of the lower layer. Dynamic recrystallization and grain growth can be activated under suitable strain and the temperature resulting from thermal cycles. The evolution of grain size and the geometric dislocation density (GND) of austenitic stainless steel 316 L under different strains and temperatures caused by thermal cycles was investigated. It is found that dynamic recrystallization requires an appropriate level of accumulated strain, temperature, and initial grain size. Under <2% accumulated strain and 400–1200 °C conditions caused by 30 layers of thermal cycles, fully dynamic recrystallization occurs with coarse initial grains (CIG), leading to the complete coarsening of grains. However, relatively fine initial grains (FIG) under the same conditions only display partial dynamic recrystallization. The next 2–4% strain and 400–700 °C by 60 layers of thermal cycles make up the driving force of fully dynamic recrystallization, and the grains coarsen completely. Larger accumulated strain (4–6%) and lower temperature (400–600 °C) by 90 layers of thermal cycles and FIG provide more nucleation sites for dynamic recrystallization, which leads to little coarsening of grains even after fully dynamic recrystallization. Temperature, accumulated strain, and the amount of δ-ferrite promote the formation of sub-grains during dynamic recrystallization caused by thermal cycles, which leads to the increase in GND. [ABSTRACT FROM AUTHOR]

The comparative investigation of the corrosion behavior of S32304 cast lean duplex and CF3M cast austenitic stainless steels was conducted in a chloride environment. The resistance to pitting corrosion of the S32304 alloy was "one" time higher than that of the CF3M alloy because the pitting potential, passive region, and critical pitting temperature of the low Ni-low Mo S32304 alloy were higher than those of the high Ni-medium Mo commercial CF3M alloy. There are two main reasons for the enhancement of the pitting corrosion resistance of high Cr-low Mo-medium N S32304 alloy compared to the low Cr-medium Mo CF3M alloy: First, the pitting resistance equivalent number (PRENδ+γ) value of the S32304 alloy is higher than that of the CF3M alloy. Second, the passive region of the S32304 alloy is larger than that of the CF3M alloy. It indicates that the synergistic effects of the three elements by adding high Cr and low Mo-medium N to the S32304 alloy enhance the passivity of the passive film, thereby increasing the resistance to pitting corrosion. It was verified that based on the PRENγ and PRENδ values calculated using an N-factor of 30, the pitting corrosion of the S32304 alloy was selectively initiated at the γ-phases and the inclusions of Mn oxy-sulfieds because the γ-phase's PRENγ value was smaller than the δ-phase's PRENδ, and finally propagated from the γ-phase to the δ-phase. [ABSTRACT FROM AUTHOR]

In the present work, the hot deformation behavior of two austenitic stainless steels with different nitrogen is studied by conducting compression tests at the strain rates in the range 0.01–7 s−1 and temperatures in the range 950–1150 °C using a Gleeble thermomechanical simulator. Simultaneously, the constitutive relationship is based on the Arrhenius hyperbolic sine equation and constructs the corresponding thermal processing maps based on dynamic material modeling (DMM).The 23Cr7MnNi2Mo0.93N (0.93 N) steel possesses a higher hot deformation resistance and a higher activation energy of deformation (628.39 kJ mol−1) compared to the 23Cr7MnNi2Mo0.45N (0.45 N) steel (315.79 kJ mol−1). Dynamic recrystallization occurs predominantly in 0.93 N steels under the conditions tested, the samples with 0.93% nitrogen content exhibit higher peak stresses and more complex rheological behavior. According to the thermal processing maps, the hot working region for 0.45 N steel is 1020 to 1150 °C at strain rates of 0.01 to 0.1 s−1, while 0.93 N steel is not suitable for processing in the experimental parameter range. [ABSTRACT FROM AUTHOR]

Super austenitic stainless steel 254SMO (254SMO SASS) plates are joined by double‐sided double‐arc synchronous TIP TIG butt welding (DSSTTABW) using ER NiCrMo3 wire, and the micro‐structure, mechanical and corrosion properties of 254SMO SASS joints are investigated subsequently. Results show that solidification grain boundary and solidification sub‐grain boundary can be observed in fusion zone. A small amount of σ phase precipitates in the weld, while χ phase is found in the transition zone, but no solidification crack occurs in weld and heat affected zone (HAZ). 254SMO SASS joint has higher micro‐hardness and lower tensile strength and elongation compared to base metal. During transverse tensile process, 254SMO SASS joints fail in the weld zone in a ductile mode. Electrochemical corrosion performance tests indicate that 254SMO SASS joint achieve equivalent pitting corrosion resistance and similar passive mechanism to base metal in 3.5 wt% NaCl solution. The passivation film on the surface of both joint and base metal display as n‐p semi‐conductive character, but the film stability of 254SMO joint surface is slightly poorer compared to base material. The surface passivation film of 254SMO joint primarily consists of oxides of Fe, Cr, and Mo before potentiodynamic polarization, while hydroxides of Fe and Cr are also observed after polarization. [ABSTRACT FROM AUTHOR]

Digital image correlation (DIC) technology can capture strain anomalies and predict crack initiation providing early warning of material failure. Herein, DIC technique is used to calculate the full‐field strain by analyzing the grayscale patterns of speckle images during the tensile process. This allowed for an analysis of the microstructure evolution of the 316LN austenitic stainless steel (SS) at cryogenic temperatures. Deformation behavior of the 316LN SS at cryogenic temperatures is further analyzed using electron backscatter diffraction technology and transmission electron microscopy. Based on the strain field obtained by the DIC technique, a comprehensive analysis of the martensite volume fraction at different strains can be conducted. The results show that the strain localization under cryogenic deformation is related to martensitic transformation, while the random distribution of slip bands aligns with local strain peak values. Notably, fracture under cryogenic deformation occurs in regions where the strain field reaches its peak, rather than at locations with the maximum strain value. [ABSTRACT FROM AUTHOR]

Ferritic/martensitic steels and austenitic stainless steels are high‐strength steels, and highly recommended in high‐temperature and high‐pressure application. In general, multimetallics with different Inconel alloys are used for joining. This is quite a complex and time‐consuming procedure. The current work demonstrates the efforts made to weld 8 mm‐thick P91 steel and 316L SS plates in a single pass using activating flux tungsten inert gas (A‐TIG) welding process without any interlayers. The main challenge is to get the symmetric weld bead profile. Flux coating is optimized in terms of flux composition, coating density, and coating pattern to get the full penetration with symmetric appearance. The current work discusses the possible cause and their solution of asymmetricity during dissimilar welding. Differential flux coating density is found to be very effective in controlling the arc column shape, fluid flow, and consequently the bead geometry. High coating density is used in the P91 side compared to 316L side. Symmetric weld profile with full penetration is achieved by applying multicomponent flux (33–38% TiO2, 38–43% SiO2, 13–17% NiO, and 8–10% CuO) during A‐TIG welding. [ABSTRACT FROM AUTHOR]

This paper outlines the TIG welding process without using active flux for 4 mm-thick plates of duplex stainless steel (DSS 2205) and austenitic stainless steel (SS 304L). It also provides the properties and behavior analysis of weldments. Complete penetration is achieved with multi-pass welding. The microstructure is examined using an optical microscope (OM) and a scanning electron microscope (SEM). It was used to report on the differences between the unpolished zone and the heat-affected zone (HAZ) in weldments. A Vickers hardness tester (HV scale 10) was used to assess the weldment's hardness. Tensile and bend failure were among the mechanical properties exhibited by the parent metals of DSS2205, SS304L, and dissimilar junctions. The findings demonstrated shallow gaps in the surface area and a greater ultimate tensile strength of 600 MPa for DSS similar welding. However, compared to other similar weldments, dissimilar weldments exhibit superior performance in bending conditions. [ABSTRACT FROM AUTHOR]

This paper presents a novel measurement method that aims to qualitatively and quantitatively assess uniform deformation during displacement- and force-controlled tensile tests of ductile metals. The method utilizes digital image correlation technology to record the strain distribution during tensile testing, followed by the calculation of the floating root mean square (RMS) value of the strain amplitude along the specimen axis. By implementing this approach, the RMS-based profiles of strain amplitude are identified in different metals and alloys, including austenitic stainless steels, structural steel, copper, and aluminium alloys. Moreover, the proposed method holds potential for predicting important deformation characteristics such as distribution of intensive plastic zones, necking effect, and delocalization effect. Thus, it establishes a link between macroscale and microscale during the analysis of plastic deformation behaviour. The effectiveness of the new method is compared with existing strain and strain-rate methods. The novel approach demonstrates promising advantages in the context of the identification of metal-forming parameters. [ABSTRACT FROM AUTHOR]

Nickel-based superalloys exhibit exceptional suitability for operating in environments characterized by corrosive agents and elevated temperatures. Strategic allocation of this expensive material solely to the functional surface areas yields significant economic advantages. The poor tribological property profile of Inconel 718 can be significantly improved through a boriding process. In this study, the possibility of combining a coating process with boriding technology and in situ heat treatment was investigated. Layers of Inconel 718 were deposited to an austenitic stainless steel using wire-based electron beam cladding (EBC) and subsequently subjected to boriding. Based on results from annealing experiments, boriding treatments were performed at various temperature/time regimens with the aim of inducing in situ age hardening during boriding. The focus was on the investigation of the influence of the temperature/time regime during boriding on the microstructure and hardness, as well as examining the wear and corrosion behavior of the resulting borided layers. The results showed that the desired target hardness range was achieved after in situ aging with all boriding variants. Furthermore, it was demonstrated that boriding significantly improved the wear resistance but decreased corrosion resistance. [ABSTRACT FROM AUTHOR]

This study investigated the influence of printing parameters and strategies on the morphological characteristics of austenitic stainless steel beads deposited on carbon steel substrates, using plasma directed energy deposition (DED). The experimental setup varied the welding current, wire feed speed, and torch travel speed, and we analyzed three printing strategies: simple-linear, overlapping, and oscillating. Moreover, advanced 3D scanning and computational analysis were used to assess the key morphological features, including bead width and height. The results showed that the computational model developed by using parabolic assumptions accurately predicted the geometric outcomes of the overlapping beads. The oscillating printing strategy was the one that showed improved morphological uniformity and bead substrate wettability, so these features were used for multi-layer component manufacturing. The use of equivalent wavelength–amplitude values resulted in maximum combinations of bead height and width. Moreover, cost-effective carbon steel substrates were feasibly used in microstructural and elemental analyses, with the latter ones confirming the alignment of the bead composition with the wire-fed material. Overall, this study provides practical insights for optimizing plasma DED processes, thus enhancing the efficiency and quality of metal component manufacturing. [ABSTRACT FROM AUTHOR]

The tungsten inert gas (TIG) welding process is widely used in various industries for its ability to produce high-quality welds at a low cost. However, TIG welding struggles with welding thick stainless steel in a single pass, reducing production efficiency. To address this, new TIG variants such as activated TIG (A-TIG), flux bound TIG (FB-TIG), and flux zone TIG (FZ-TIG) have been developed to enhance penetration in austenitic stainless steel. This study investigates the effects of TiO2 and Fe2O3 flux on 304 stainless steels welded using A-TIG, FB-TIG, and FZ-TIG processes. Results show a slight increase in the depth-to-width (d/w) ratio for A-TIG and FB-TIG, while FZ-TIG achieved a 59% higher d/w ratio compared to autogenous TIG welding. The increased penetration is attributed to the reversal Marangoni convection and arc constriction. Microstructural analysis reveals a higher delta ferrite content in A-TIG and FZ-TIG welds due to increased heat input. Additionally, FZ-TIG welds exhibited an 11.5% higher microhardness compared to autogenous TIG welds. FZ-TIG welding enhances penetration and mechanical properties effectively. [ABSTRACT FROM AUTHOR]

In the present study, cold metal transfer arc welding was employed to weld the 304L austenitic stainless steel (ASS) and Ti-stabilized 439 ferritic stainless steel (FSS) using a 309L filler electrode. Dissimilar joints were prepared using low heat input (HI; W1 ~ 247 J/mm) and high HI (W2 ~ 282 J/mm). The solidification mode for both weldments were the ferritic-austenitic mode and the weld zone (WZ) regions of both the weldments consists of columnar austenites, lathy and skeletal ferrite phases. The interfaces between WZ and ASS base metal showed the unmixed zone, whereas a conventional heat-affected zone (HAZ) was formed between the WZ and FSS base metals. The formation of ferrite stringers were observed in the unmixed zone, whereas peppery features of chromium-rich carbides were observed in HAZ. Moreover, electron backscattered diffraction technique was used to distinguish the microstructural differences between W1 and W2 weldments. Increase in the HIs resulted in decreased ferrite fraction in WZ as well as decrease in the mechanical strength of the joints. The W1 weldment depicted higher values of average micro-hardness (WZ ≈ 334.32 HV) than W2 (WZ ≈ 310.92 HV)) weldment. The electrochemical behaviour of the weldments was analysed for both the base metals and WZ of weldments. The higher degree of sensitization (DOS ~ 9.24%) of W1-WZ showed lower intergranular corrosion resistance than W2-WZ (DOS ~ 7.77%), however, the opposite trend was observed for impedance and pitting resistance. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the influence of lubrication and cooling conditions in the diamond burnishing (DB) process on the surface integrity and fatigue limit of chromium–nickel austenitic stainless steels (CNASSs) and, on this basis, identify a cost-effective and sustainable DB process. Evidence was presented that DB of CNASS performed without lubricating cooling liquid satisfies the requirements for a sustainable process: the three key sustainability dimensions (environmental, economic, and social) are satisfied, and the cost/quality ratio is favorable. DB was implemented with the same values of the main governing factors; however, four different lubrication and cooling conditions were applied: (1) flood lubrication (process F); (2) dry without cooling (process D); (3) dry with air cooling at a temperature of −19 °C (process A); and (4) dry with nitrogen cooling at a temperature of −31 °C (process N). Conditions A and N were realized via a device based on the principle of vortex tubes. All four DB processes provide mirror-finished surfaces with Ra roughness parameter values from 0.041 to 0.049 μm, zones with residual compressive stresses deeper than 0.5 mm, and increases in the specimens' fatigue limit (as determined by the accelerated Locati's method) compared to turning and polishing. Processes F and D produce the highest microhardness on the surface and at depth. The process D introduces maximum compressive residual axial and hoop stresses in the surface layer. The dry DB processes (D, A, and N) form a submicrocrystalline structure with high atomic density, which is most strongly developed under process D. When high fatigue strength is required, DB with air cooling should be chosen, as it provides a more favorable cost/quality ratio, whereas dry DB without cooling is the most suitable choice for applications that require increased wear resistance. [ABSTRACT FROM AUTHOR]

It is well known that stainless steel has many advantages such as superb durability, ductility, and corrosion resistance. Thus, the use of stainless steel for various structural members in construction fields is recently increasing. Structural behaviors of bolted and welded connections, compressive and flexural members, beam-column joints, seismic devices etc. have been conducted experimentally and numerically and thus new design methods have been proposed. Hence, in this study, both experiment and finite element analysis were conducted to assess the block shear failure behaviors of double-shear four-bolted connections made of austenitic stainless steel (STS304) with thinner plate and larger end distance, which are beyond the range of previous literature. The main parameter was end distance and edge distance. Block shear strengths by parametric analysis and test results study were compared with design predictions. It is found that current design equations tended to significantly underestimated test and analysis results. Therefore, modified block shear strength equation was recommended for austenitic stainless steel double shear bolted connection treated in this study. [ABSTRACT FROM AUTHOR]

The influence of applied loading rate (dK/dt) on stress corrosion cracking (SCC) behavior in annealed 304L stainless steel immersed in 4.7 M MgCl2 solution was assessed at varying temperatures from 23 °C to 70 °C. Measured crack growth rates obtained under rising K loading (dK/dt > 0) are compared to those obtained during static K testing. A rising K-based loading protocol was found to yield more conservative crack growth rates across all temperatures, with the variation in crack growth rates (and therefore the dependence in loading rate) decreasing with increasing environmental severity. [ABSTRACT FROM AUTHOR]

The sensitization behavior of the welding heat affected zone (HAZ) in austenitic stainless steels (SSs) was investigated through simulated thermal cycles emulating actual multi-pass welding processes using the Gleeble simulator. The tests were performed with austenitic SSs, considering carbon contents, heat input, and distance from the fusion line to determine the thermal cycle conditions of the HAZ. Higher carbon content led to increased sensitization (degree of sensitization, DOS) values, while the influence of the thermal cycle in the final weld pass was that even though it was rapidly heated to over 1000 °C and cooled at a rapid rate, the DOS value decreased due to partial carbide dissolution and chromium diffusion. Therefore, effective management of the final thermal cycle in the HAZ contributes to improved intergranular stress corrosion cracking resistance. Even with prolonged exposure of the HAZ to the sensitization region, the discovery that corrosion resistance improves when the final heating cycle reaches 1000 °C underscores the importance of HAZ heat cycle management and provides valuable insights for materials engineering and industrial applications. [ABSTRACT FROM AUTHOR]

In this study, austenitic stainless steel (AISI 316L grade) coupon samples were developed by laser direct energy deposition (LDED) technique (using a 6 kW fiber-coupled diode laser with a wavelength of 1000 and 3.6 mm beam diameter) with 600–1000 W power input and 2–5 mm/s scan speed at a powder feed rate of 50 g/min. The clad zone was thoroughly investigated in terms of microstructure, phase, micro and nanohardness, and mechanical and electrochemical properties and correlated with input LDED parameters to determine the optimum process window. The samples processed under optimal process parameters were subjected to tensile testing, followed by a detailed study of the fractured surface to determine the mechanism of tensile deformation and failure. LDED leads to microstructural refinement and, hence, increases its microhardness in comparison with base plate. The wear (against the WC ball in fretting mode) and corrosion resistance (in a 3.56 wt pct NaCl solution) were improved for LDED coupons in comparison with that of the wrought alloy. Tensile behavior shows a marginal increase in yield strength and ultimate tensile strength in addition to ductility as compared to wrought alloy. [ABSTRACT FROM AUTHOR]

A Monte Carlo simulation method capable of replicating the kinetics of M23C6 precipitation in 347H stainless steels was developed for the purpose of producing synthetic microstructures that approximate its microstructural evolution under aging periods of up to 10,000 hours at temperatures between 600 °C and 750 °C. To accomplish this, experimental data from the literature was used to parameterize simulations and replicate the nucleation and growth kinetics of M23C6 particles within 347H and similar austenitic stainless steel alloys. These simulations were found to have considerable fidelity to previous efforts to study the precipitation of M23C6 in other 300 series stainless steel alloys. Synthetic 347H microstructures were then generated that accounted the effects of aging temperature, duration, dislocation density, and the presence of boron within the microstructure. These simulations predict several key trends, those being that (1) the size of M23C6 precipitates decreased with aging temperature and (2) the growth rate of M23C6 particles decreased with aging temperature. Further, while (3) the addition of dislocation density due to creep conditions resulted in increasing intragranular nucleation of M23C6 precipitates with increasing dislocation density and (4) B additions within the microstructure led to modest increases in precipitate size above 700 °C, which indicates that more complex physics are necessary to account for the presence of B. [ABSTRACT FROM AUTHOR]

The 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. [ABSTRACT FROM AUTHOR]

A novel non-magnetic Fe-21Cr-15Ni-5Mn-2Mo austenitic stainless steel with high strength and plasticity has been developed. The microstructure and liquid helium temperature (4.2 K) tensile properties of the top and bottom samples of large-size forged flat steel after solution treatment at 1090 °C were investigated. The results showed that the average grain size of the bottom sample (48.0 ± 6.7 μm) was smaller than that of the top sample (58.8 ± 15.3 μm), and the MX precipitates and Z phases were distributed in the matrix of the samples. The 4.2 K strengths of the samples at the top and bottom were high, and large amounts of annealing twin boundaries played a certain role in strengthening. After cryogenic tensile testing, large amounts of deformation twins, stacking faults, and dislocations were generated inside the austenite grains of both samples, which helped the material to obtain higher plasticity and strength. The top and bottom samples possessed excellent synergies of strength and plasticity at 4.2 K, and the 4.2 K tensile properties of the top sample were as follows: ultimate tensile strength (UTS) of 1850 MPa, yield strength (YS) of 1363 MPa, and elongation (EL) of 26%. The tested steel is thus believed to meet the requirements of combined excellent strength and plasticity within a deep cryogenic environment, and it would be a promising material candidate for manufacturing superconducting coil cases to serve in new generation fusion engineering. [ABSTRACT FROM AUTHOR]

Due to variations in chemical composition and production processes, homonymous austenitic stainless steels can differ significantly regarding their initial microstructure, metastability, and thus, their fatigue behavior. Microstructural investigations and fatigue tests have been performed in order to evaluate this aspect. Three different batches and production forms of nominally one type of steel AISI 347 were investigated under monotonic tensile tests and cyclic loading under total strain and stress control in low and high cycle fatigue regimes, respectively. The deformation induced α'-martensite formation was investigated globally by means of in situ magnetic measurements and locally using optical light microscopy of color etching of micrographs. The investigation showed that the chemical composition and the different production processes influence the material behavior. In fatigue tests, a higher metastability and thus a higher level of deformation induced α'-martensite pronounced cyclic hardening, resulting in significantly greater endurable stresses in total strain-controlled tests and an increase in fatigue life in stress-controlled tests. For applications of non-destructive-testing, detailed knowledge of a component's metastability is required. In less metastable batches and for lower stress levels, α'-martensite primarily formed at the plasticization zone of a crack. Furthermore, the formation and nucleation points of α'-martensite were highly dependent on grain size and the presence of δ-ferrite. This study provides valuable insights into the different material behavior of three different batches with the same designation, i.e., AISI 347, due to different manufacturing processes and differences in the chemical composition, metastability, and microstructure. [ABSTRACT FROM AUTHOR]

The directed energy deposition arc (DED-Arc) has been extensively used to develop metallic parts with varying complexities. A major challenge for austenitic stainless steels is managing heat accumulation due to their low thermal conductivity. This study aimed to characterize the microstructure and mechanical properties of AISI 316L preforms manufactured by additive manufacturing (AM) under different deposition paths and cooling conditions. Samples underwent macro- and microstructural analyses, and tensile and hardness tests to evaluate their mechanical behavior. Additionally, the effect of active cooling using near immersion active cooling (NIAC) in water on the microstructure was assessed by examining the secondary interdendritic spacing and ferritic phase fraction. The NIAC technique has shown potential for enhancing productivity by producing preforms with more uniform thickness and consistent solidification/cooling conditions throughout the multiple layers. This approach eliminated deposition idle time, leading to a productivity increase of up to 108%. Microstructures obtained with active cooling were more refined than those resulting from natural cooling, evidenced by a reduction in secondary interdendritic spacing and an increased fraction of delta ferrite. These microstructural changes resulted in higher hardness and mechanical strength in the material processed with the NIAC technique. However, difficulties in precisely controlling the water level resulted in increased apparent porosity when using the NIAC technique. [ABSTRACT FROM AUTHOR]

The shot peening procedure enhances the mechanical characteristics with the transformation of compressive residual stresses which helps in the increment of operational lifespan of the product. The study comprehensively analyzed the effect of consecutive shot peening procedures up to four peening passes with the coverage increases 100% on each peening pass up to 400% on the laser powder bed fused austenitic stainless steel and compared with the as-built condition focusing on surface characteristics, mechanical characteristics, and corrosion potential. Surface damage of the peened samples was found very minimal with the absence of visible scan tracks and unmelted powder particles due to the controlled peening parameters. The inducement of compressive residual stresses (−625 MPa) was observed to be higher at the fourth consecutive peening passes without strain-induced martensite, with an increment of hardness proportion of 29.12% with a depth of 1 mm, and increment of corrosion resistance across each peening pass. [ABSTRACT FROM AUTHOR]

Underwater laser direct metal deposition (UDMD) shows great application potential in underwater high-performance repair. The susceptibility of underwater repaired components to hydrogen embrittlement (HE) is not extensively researched yet. In this study, HE in 316L stainless steel repaired by UDMD is systematically investigated and compared with in-air direct metal deposited (DMD) 316L and conventionally manufactured (CM) 316L. The experimental results show that the high cooling rates involved in UDMD contribute to a "austenite-ferrite" solidification mode. The cellular structure with a high-density of dislocations increases the tensile strength of as-built UDMD 316L. Thermal desorption spectroscopy analysis reveals that the hydrogen concentrations are similar for 316L manufactured by three processing methods, suggesting that the complex microstructural features by UDMD and DMD do not provide additional H-trapping sites. SSRT results show that the HE susceptibility is in the sequence: CM 316L (30.7%) > UDMD 316L (15.1%) > DMD 316L (9.6%). Compared with CM 316L, the stable cellular structure and higher stability towards martensitic transformation of as-built 316L are beneficial for the HE resistance. In the hydrogen-charged UDMD 316L, the hydrogen-assisted dislocation movement and mechanical twinning formation enhance the localized plasticity and induce cracking. The micron-sized oxide particles and micro-pores further contribute to the fast decohesion of interfaces in the presence of hydrogen. Those combined effects lead to the reductions in tensile strength and elongation of the hydrogen-charged UDMD 316L. • High cooling rates in UDMD lead to cellular structures with high dislocation density. • Complex microstructures in UDMD 316L do not provide additional H-trapping sites. • HE susceptibility of UDMD 316L is larger than that of in-air DMD 316L. • H-assisted dislocation movement and twinning formation induce cracking of UDMD 316L. • Micron-sized oxide particles and micro-pores with H contribute to premature failure. [ABSTRACT FROM AUTHOR]

The ultrafine cellular structure promotes the extraordinary mechanical performance of metals manufactured by laser powder‐bed‐fusion (L‐PBF). An in‐depth understanding of the mechanisms governing the thermal stability of such structures is crucial for designing reliable L‐PBF components for high‐temperature applications. Here, characterizations and 3D discrete dislocation dynamics simulations are performed to comprehensively understand the evolution of cellular structures in 316L stainless steel during annealing. The dominance of screw‐type dislocation dipoles in the dislocation cells is reported. However, the majority of dislocations in sub‐grain boundaries (SGBs) are geometrically necessary dislocations (GNDs) with varying types. The disparity in dislocation types can be attributed to the variation in local stacking fault energy (SFE) arising from chemical heterogeneity. The presence of screw‐type dislocations facilitates the unpinning of dislocations from dislocation cells/SGBs, resulting in a high dislocation mobility. In contrast, the migration of SGBs with dominating edge‐type GNDs requires collaborative motion of dislocations, leading to a sluggish migration rate and an enhanced thermal stability. This work emphasizes the significant role of dislocation type in the thermal stability of cellular structures. Furthermore, it sheds light on how to locally tune dislocation structures with desired dislocation types by adjusting local chemistry‐dependent SFE and heat treatment. [ABSTRACT FROM AUTHOR]

This study evaluates the effectiveness of KMnO4, MK3 and 1-butanol inhibitors on corrosion of AISI 314 and AISI 304 stainless steels using linear and potentiodynamic polarization in 0.1 M HNO3. The metrics like corrosion potential (Ecorr), current density (jcorr) and polarization resistance (Rp) influence the inhibitor efficacy. The inhibitors improved electrochemical parameters significantly, indicating strong anti-corrosive properties. 1-Butanol had the strongest effect, enhancing corrosion potential and drastically reducing corrosion current density, demonstrating superior protection. The results indicated that without inhibitors, both steels showed higher corrosion rates and more negative potentials, reflecting their susceptibility to corrosion. The introduction of inhibitors markedly improved these parameters, particularly with 1-butanol, which significantly enhanced the polarization resistance and shifted the corrosion potential towards less negative values. The potentiodynamic results highlighted the dynamic effectiveness of inhibitors, reinforcing their role in mitigating corrosion under varied conditions. The study underscores the importance of selecting the appropriate inhibitors to enhance the durability and longevity of stainless steels in acidic environments, with 1-butanol showing the potential for industrial applications requiring high corrosion resistance. This necessitates comprehensive testing to accurately measure inhibitor capabilities in different conditions. [ABSTRACT FROM AUTHOR]

This comprehensive review examines the phenomena of stress corrosion cracking (SCC) and chloride-induced stress corrosion cracking (Cl-SCC) in materials commonly used in the oil and gas industry, with a focus on austenitic stainless steels. The study reveals that SCC initiation can occur at temperatures as low as 20 °C, while Cl-SCC propagation rates significantly increase above 60 °C, reaching up to 0.1 mm/day in environments with high chloride concentrations. Experimental methods such as Slow Strain Rate Tests (SSRTs), Small Punch Tests (SPTs), and Constant-Load Tests (CLTs) were employed to quantify the impacts of temperature, chloride concentration, and pH on SCC susceptibility. The results highlight the critical role of these factors in determining the susceptibility of materials to SCC. The review emphasizes the importance of implementing various mitigation strategies to prevent SCC, including the use of corrosion-resistant alloys, protective coatings, cathodic protection, and corrosion inhibitors. Additionally, regular monitoring using advanced sensor technologies capable of detecting early signs of SCC is crucial for preventing the onset of SCC. The study concludes with practical recommendations for enhancing infrastructure resilience through meticulous material selection, comprehensive environmental monitoring, and proactive maintenance strategies, aimed at safeguarding operational integrity and ensuring environmental compliance. The review underscores the significance of considering the interplay between mechanical stresses and corrosive environments in the selection and application of materials in the oil and gas industry. Low pH levels and high temperatures facilitate the rapid progression of SCC, with experimental results indicating that stainless steel forms passive films with more defects under these conditions, reducing corrosion resistance. This interplay highlights the need for a comprehensive understanding of the complex interactions between materials, environments, and mechanical stresses to ensure the long-term integrity of critical infrastructure. [ABSTRACT FROM AUTHOR]

F321 austenitic stainless steel is used in high-temperature, high-pressure, and severe irradiation conditions at high-temperature gas reactors, leading to the formation of irradiation defects such as point defect in the matrix. This study explores the displacement cascade process in F321 austenitic stainless steel based on molecular dynamics (MD) simulations with the aim of investigating the effect of PKA energy, PKA direction and temperature. MD results show that irradiation-induced Frenkel pairs (FPs) number increases with increasing PKA energy. The effect of different PKA directions is not significant when energy is lower than 30 keV, which becomes obviously at 50 keV and 100 keV. In addition, the increasing temperature leads to lower FPs. When it comes to defect cluster, both size and number of clusters increase with increasing PKA energy, which is consistent with the trend with FPs. Vacancy cluster is larger than that of interstitial cluster and the irradiation-induced defect cluster is not significantly dependent on PKA directions. Furthermore, five typical dislocation loops (1/2 < 110>, 1/6 < 112>, 1/3 < 111>, 1/6 < 110 > and 1/3 < 100>) are observed in samples after displacement cascade, especially high-energy PKA cascades. More interestingly, 1/6 < 112 > dislocation loop is formed first in the displacement cascade process due to its high mobility. These insights reveal systematic irradiation defect formation mechanism during displacement cascade under varied irradiation conditions, offering a new perspective for novel understanding irradiation effect in F321 stainless steel. Based on that, the effect of various factors could be quantified precisely, governing the study of irradiation defects' generation. [ABSTRACT FROM AUTHOR]

The application possibilities of austenitic stainless steels in high friction, abrasion, and sliding wear conditions are limited by their inadequate hardness and tribological characteristics. In order to improve these properties, the thermochemical treatment of their surface by plasma nitriding is suitable. This article is focused on the corrosion resistance of conventionally plasma-nitrided AISI 304 stainless steel (530 °C, 24 h) in 0.05 M and 0.5 M sodium chloride solutions at room temperature (20 ± 3 °C), tested by potentiodynamic polarization and electrochemical impedance spectroscopy. Optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy are used for nitrided layer characterization. The experiment results confirmed the plasma-nitrided layer formation of increased micro-hardness related to the presence of Cr2N chromium nitrides and higher surface roughness compared to the as-received state. Both of the performed independent electrochemical corrosion tests point to a significant reduction in corrosion resistance after the performed plasma nitriding, even in a solution with a very low chloride concentration (0.05 mol/L). [ABSTRACT FROM AUTHOR]

AISI 301LN metastable austenitic stainless steels (MASSs) are known to exhibit high work‐hardening rates attributed to martensite evolution during straining which results in the second‐phase strengthening mechanism. This enhances surface hardness and potentially reduces wear and rolling contact fatigue (RCF). The aim of this study is therefore to evaluate the work hardening, wear, and RCF performance of AISI 301LN metastable austenitic stainless steel as a possible alternative material for rolling and sliding applications by varying the contact conditions such as slip ratio against the standard R350HT rail steel using a twin‐disc simulator. The results show that 301LN MASS has high surface work hardening and increased hardness because of martensitic transformation, while R350HT rail steel has only slightly changed. The formation of a hard martensitic phase is also confirmed by X‐ray diffraction analysis as well as by two other techniques, indicating a secondary hardening effect. Although it shows potential for work hardening, its susceptibility to wear‐related problems may make it less suitable for rolling and sliding applications due to a cracking and spalling mechanism induced by martensite formation. The surface strains required for the observed martensite formation are calculated and found to be very high, approaching 0.4. [ABSTRACT FROM AUTHOR]

316 Austenitic stainless steel (AusSS) is extensively utilized in high‐temperature industrial applications such as boiler tubes and nuclear reactor pressure vessels. These components commonly experience failure under high‐temperature and high‐pressure conditions, attributed to either creep or fatigue. Existing classical models for creep and fatigue life prediction focus on a singular failure mode (either creep or fatigue) and consider physical features only. This study aims to develop a unified life prediction model for both creep and fatigue phenomena. It synthesizes information from 12 additional unexplored chemical and microstructural features from the National Institute of Materials Science (NIMS), Japan database, and previously published literature. Machine learning (such as decision tree, random forest, and XGBoost) and deep learning (like deep neural network) algorithms are employed in the modeling process. The trained models have been cross‐validated against unseen creep and fatigue life data, demonstrating superior prediction accuracy of 96.1% for deep neural network compared with classical models. Highlights: Unified prediction model for both creep and fatigue life prediction.Investigated the effect of up to 20 physical, chemical, and microstructural features.Multiple ML and DL prediction models were developed and compared with classical ones. [ABSTRACT FROM AUTHOR]

This study investigates the relationship between grain size and material parameters defined in the microscopic hardening laws of the phenomenological crystal plasticity model of Méric–Cailletaud. This investigation is essential for accurate cyclic loading simulations, where the grain size effect on kinematic hardening cannot be neglected. The work was carried out through finite element simulations of the macroscopic plastic behavior of six representative volume elements (RVEs), of austenitic stainless steel 316L, varying in grain size, using a model of Méric–Cailletaud, implemented within the Abaqus software. Experimental literature results serve as benchmarks for adjusting grain size-related hardening parameters. The findings reveal that the studied parameters obey the Hall–Petch law and exhibit an inverse relationship with the square root of the grain size. What is noteworthy is the effect of grain size on kinematic hardening, which differs significantly from previous studies where kinematic hardening parameters were kept constant. Additionally, parameter evolution varies notably between microstructures with coarse and fine grains. Finally, determining hardening parameter variation as a function of grain size provides us with an extended model of Méric–Cailletaud capable of predicting the local as well as the global mechanical behavior of stainless steel 316L in both monotonic and cyclic loading cases, considering the grain size effect. [ABSTRACT FROM AUTHOR]

Solid-to-solid diffusion bond between ferritic SA508 low alloy steel (LAS) and austenitic 316L stainless steel (SS) via hot isostatic pressing (HIP) was evaluated. This study investigated the microstructural and mechanical evolutions of the bimetallic interface before and after heat treatment. The interfacial region between two materials demonstrated uniform microstructure, no visible manufacturing defects, and higher interfacial hardness and tensile strength. The joint interface was stronger than for both 316L SS and SA508 LAS. The interfacial hardening was attributed to the significant grain refinement at the interface region and dislocation hardening under as-HIP'ed condition. Post-HIP heat treatment considerably reduced the interfacial strength, attributed to dislocation recovery and grain growth. From the mechanical perspective, the work confirmed utilizing HIP capsules during HIP manufacturing provides adequate interfacial strength between 316L SS HIP capsule and SA508 LAS for cladding purposes. The 316L SS HIP capsule may be used as the cladding layer for corrosion protection. [ABSTRACT FROM AUTHOR]

Interrupted and incremental tensile tests have been carried out on 316 austenitic stainless steel at different strain rates, revealing the correlation between the strain, strain rate, and temperature rise of martensitic transformation. The FERITSCOPE FMP ferrite tester and Telops FAST M2K infrared imager measured the martensite content and surface temperature rise at different strain rates, respectively. The effect of adiabatic temperature rise and strain rate on martensitic transformation was isolated by incremental tests. Compared with the incremental tensile test at a low strain rate (0.001 s−1), it has been found that the increase in strain rate has a negative effect on martensitic transformation, and the effect of strain rate on martensitic transformation seems to be more significant than that of adiabatic temperature rise. The formation and evolution mechanism of strain-induced martensitic transformation of 316 austenitic stainless steel were studied by electron backscattered diffraction. During the process of tensile plastic deformation, the nucleation and growth of new martensite mainly occurred near the twin boundary. [ABSTRACT FROM AUTHOR]

Wire arc additive manufacturing (WAAM), based on gas metal arc welding, is ideal for fabricating components with sizeable geometries and moderate structural intricacies. However, the electric arc introduces a heat source and directional heat dissipation during deposition, resulting in undesired microstructural characteristics, such as columnar dendritic structures, which lead to variations in hardness across the printed component. Our previous research introduced the friction stir burnishing (FSB) tool integrated with WAAM using a hybrid approach called simultaneous processing. This method suppressed dendrite formation and enhanced the microstructure within WAAM. This approach directly correlates process dynamics, force dynamics, and temperature control, facilitating efficient plastic deformation. This research investigates the relationship between process parameters and microhardness within the combined manufacturing systems of WAAM and FSB tools. The study primarily focuses on using SUS 316L austenitic stainless steel wire material for WAAM and examines how simultaneous operation with the FSB tool impacts microstructure and microhardness. The investigation emphasizes three key parameters: the distance between the welding torch and the FSB tool, tool rotational speed, and machine feed speed. Comprehensive experimentation, including Taguchi analysis, determines optimal values for these parameters. Results indicate that torch-to-tool distance and machine feed speed significantly influence microhardness, while tool rotational speed shows minimal impact. The most effective combination for enhancing microhardness was a torch-to-tool distance of 20 mm, a machine feed speed of 528 mm/min, and a tool rotational speed of 1900 rpm. This combination induced a plastic deformation transformation effect, contributing to the overall improvement in microhardness. Additionally, the optimal parameters for achieving a smaller grain size were a torch-to-tool distance of 17 mm, a machine feed speed of 356 mm/min, and a tool rotational speed of 1900 rpm, as indicated by the average grain size. Furthermore, this study shows significant improvements in microstructure and hardness within 50–200 µm depth from the surface. Comparative analysis between FSB tool-processed and non-processed samples indicates a 22.51% increase in microhardness, with the grain size of the simultaneous process being 7 µm compared to 11.55 µm. Optimizing the process parameters of simultaneous processing achieves superior microhardness and microstructural refinement. Additionally, it highlights the need for further material development to address challenges associated with tool durability, paving the way for advancements in simultaneous processes. [ABSTRACT FROM AUTHOR]

In this work, the oxidation properties of austenitic 316L stainless steel powder and sintered porous support were investigated at the temperature range of ~600-750 䨽 for 100 hours in ambient air. Oxidation kinetics was determined by continuous thermogravimetry and analyzed employing parabolic rate law. It was observed that oxidation leads to the formation of an oxide scale, with substantial oxidation occurring at = 650 ℃ in the powder. The porous steel support was fabricated using the tape casting method with two distinct pore former concentrations. The microstructural features of both the powder and support were investigated by X-ray diffractometry and scanning electron microscopy coupled with energy-dispersive X-ray analysis. The mechanical properties of the metal support were examined before and after oxidation via a microhardness test. The effect of porosity on the resulting properties of the metal support was also highlighted. In summary, 316L stainless steel support suits SOCs applications below 600 ℃. [ABSTRACT FROM AUTHOR]

AISI 316L austenitic stainless steel is utilized in various processing industries, due to its abrasion resistance, corrosion resistance, and excellent properties over a wide temperature range. The physical and mechanical properties of a material change during the manufacturing process and plastic deformation, e.g., bending. During the combined tensile and bending loading of a structural component, the stress state changes due to the residual stresses and the loading range. To characterize the component's stress state, the billet was bent to induce residual stress, but a phase transformation to martensite also occurred. The bent billet was subjected to combined tensile–bending and fatigue loading. The experimentally measured the load vs. displacement of the bent billet was compared with the numerical simulations. The results showed that during fatigue loading of the bent billet, both the initial stress state at the critical point and the stress state during the dynamic loading itself must be considered. Analysis was demonstrated only for one single critical point on the surface of the bent billet. The residual stresses due to the phase transformation of austenite to martensite affected the range and ratio of stress. The model for the stress–strain behaviour of the material was established by comparing the experimentally and numerically obtained load vs. displacement curves. Based on the description of the stress–strain behaviour of the pre-deformed material, guidelines have been provided for reducing residual tensile stresses in pre-deformed structural components. [ABSTRACT FROM AUTHOR]

In the context of an increasing interest in the use of high-performance steels in the construction industry due to their superior mechanical properties, understanding the behaviour and assessing the performance of dissimilar welded connections becomes essential. When several steel grades are adopted for fabrication of the same dissipative element, dissimilar welded connections have a decisive importance regarding the seismic performance of the structural member. This paper presents the experimental results of monotonic and low-cycle fatigue (LCF) tests on dissimilar welded connections. The welded connections are designed to reproduce the loading state that occurs between the web and the flanges of dissipative links in an eccentrically braced frame, and represent combinations of S235 mild carbon steel, 1.4404 austenitic stainless steel, and S690 high-strength steel. The obtained experimental results provide a better understanding of the behaviour of dissimilar welded connections through the evaluation of their strength, ductility, and failure mechanisms, providing a basis for finite element (FE) models' calibration for further numerical simulations. This study contributes to the evaluation of the feasibility of connections between dissimilar steels in seismic-resistant steel structures. [ABSTRACT FROM AUTHOR]

To detect mechanical overloads on the component directly in operation, a metastable material can be used as a load-sensitive sensor when combined with an eddy current testing system. In order to find a suitable metastable sensor material that exhibits microstructural changes at an early stage before fatigue failure, quasi-static tensile tests and cyclic rotating bending tests were carried out with the austenitic stainless steels 1.4301 (2 batches), 1.4305, 1.4541 and 1.4550. For the detection of microstructural changes, electromagnetic testing was used in-situ in the tensile test and ex-situ between the rotating bending test after a pre-defined number of cycles. The investigated materials 1.4301 batch2 and 1.4550 showed the largest signal changes and the lowest austenite stability both in the tensile test and under cyclic bending load. Due to the better mechanical properties, 1.4301 batch2 should be preferred. The order of the austenitic stainless steels tested was similar in terms of transformation behavior in both tests. Thus, the tensile test combined with in-situ electromagnetic testing appears to have potential as a suitable benchmark test for austenite stability. With regard to the cyclic bending stress, an overload of the specimens could be detected for the materials 1.4301 batch2, 1.4305, 1.4541 and for the 1.4550 on the basis of a significant amplitude change. At low bending stresses, uncritical for structural integrity, no increase in amplitude was measured. The results have shown that an early detection of overloads is possible with several materials, however, the potential for detecting overloads varies between materials and also between individual batches. In addition, it has been observed that as the bending stress increases, the gradient of the change in amplitude over the number of cycles increases as well. Thus, with a known number of cycles, it could be possible to classify the previous load spectrum based on the difference in amplitude between two measurements. [ABSTRACT FROM AUTHOR]