Austenitic Stainless Steel Grade Research Articles

Comparison of electrolytic etching and immersion etching for 304L, 316L and 347 austenitic stainless-steel grades

Comparison of electrolytic etching and immersion etching for 304L, 316L and 347 austenitic stainless-steel grades

Intergranular Corrosion Analysis of Austenitic Stainless Steels in Molten Nitrate Salt Using Electrochemical Characterization

This study investigates the influence of molten nitrate salt exposure on the intergranular corrosion (IGC) behavior of three grades of austenitic stainless steel (namely, AISI 304, AISI 304H, and AISI 321H). Two electrochemical techniques, double loop electrochemical potentiokinetic reactivation and potentiodynamic polarization methods, are applied after stainless steel is exposed to 600 °C molten nitrate salt, 60% NaNO3, and 40% KNO3 for varying immersion durations. Corrosion morphology is examined using optical microscopy and scanning electron microscopy images to assess susceptibility to IGC. IGC is prompted by the presence of chromium carbides at grain boundaries, which leads to chromium depletion around these carbides. The findings of the experiments reveal distinct IGC behavior among stainless steel grades. For AISI 304, the degree of sensitization (DOS) increases as exposure time progresses. However, AISI 304H and AISI 321H stainless steel exhibit diminishing DOS after 100 and 10 h of exposure, respectively. This trend is attributed to desensitization or the healing effect when stainless steel is exposed to molten salt for a prolonged time. The depletion and recovery of Cr near grain boundaries are confirmed by the inverse relationship to DOS of pitting potential.

Validating cyclic plasticity material model for three materials subjected to asynchronous axial-torsion conditions

In the present work, a cyclic plasticity model based on Ohno-Wang kinematic hardening rule and Tanaka non-proportionality parameter, is proposed to simulate the cyclic stress strain response of three materials. The proposed model has been validated with respect to reported test results on two grades of steel (SA 333 Gr. 6 and E355) and one grade of austenitic stainless steel (X5CrNi18-10) under asynchronous axial-torsion loading conditions with a wide range of frequency ratios. The proposed model resulted in a comparable assessment of axial and shear stress–strain response with respect to the test loops for all three materials.

The Effects of Electrochemical Hydrogen Charging on Charpy Impact Toughness and Dry Sliding Tribological Behavior of AISI 316H Stainless Steel

In this work, solution-annealed AISI 316H grade austenitic stainless steel was studied in terms of investigating the electrolytic hydrogen charging effects on the resulting Charpy impact toughness and dry sliding tribological behavior. Conventional Charpy impact bending tests were employed to study the mechanical response of the investigated material to dynamic loading conditions, whereas dry linear sliding tribological tests were used to study material friction and wear behavior. The obtained mechanical and tribological properties were correlated with corresponding fracture and tribological mechanisms, which were determined from morphological observations of fracture surfaces and tribological tracks. The applied testing procedures were individually carried out for the non-hydrogenated, hydrogen-charged, and dehydrogenated material conditions. The observed changes in individual properties due to applied hydrogen charging were rather small, which indicated the good resistance of solution-annealed AISI 316H steel against material degradation in currently used electrolytic hydrogenation conditions.

Microstructure and Pitting Corrosion Characteristics of Tig Welded Joints of Super 304HCu Austenitic Stainless Steel

Abstract Super 304HCu is an advanced ultra-super critical (A-USC) boiler grade austenitic stainless steel with the distinct addition of 3 wt.-% of Copper. A-USC power plants intended to operate in chloride rich environments (sea shore, feed water residues, etc.) are susceptible to chloride assisted corrosion failures. In this study, the pitting corrosion behaviour of the Super 304HCu parent material and tungsten inert gas weld joints was studied using a potentiodynamic cyclic polarization test in 3.5 % NaCl solution at three different pH levels (pH = 3, pH = 7, and pH = 11). The Epit values of the parent material is found to be much nobler than that of the weld joints. The micrographs of the pitted weld joints and the oxalic acid etched structure of Super 304HCu joints are presented. From the micrographs it is revealed that the heat affected zone is the most susceptible region to pitting corrosion.

Improving erosion resistance through solution treatment of nitronic and martensitic steels for slurry erosive applications

Erosive wear is a general phenomenon in moving underwater parts of various types of equipment and slurry transportation. Materials with high erosion resistance are recommended for such applications. Currently used martensitic steel can be replaced with nitrogen containing austenitic stainless-steel grades 21-4 N and 23-8 N due to higher erosion resistance. This paper investigates the pathway to enhance the slurry erosion resistance of nitronic steels and evaluates its feasibility to replace currently used martensitic steel for heavy slurry erosive applications. Solution treatment was observed as a potential pathway to improve slurry erosion resistance and mechanical properties of the selected steels where specimens were subjected to solution treatment at 950 °C and 1150 °C. After the solution treatment, reduced carbide volume and fine distribution in the nitrogen alloyed austenitic microstructure resulted in higher erosion resistance. Nitronic steel grades resulted in low cumulative weight loss or high erosion resistance than martensitic steel for as-received and solution-treated samples. Solution treatment resulted in a maximum reduction in cumulative weight loss for martensitic steel, 21-4 N and 23-8 N was 10 wt%, 14.2 wt%, and 18.18 wt%, respectively, at 90° impingement angle. The erosion mechanisms observed at different impingement angles were different for both nitrogen alloyed and martensitic steels. The erosion mechanism was primarily deformation at 90° impingement angle, whereas at 30° impingement angle, the mechanism was lip formation, detachment, and ploughing.

Structural performance of stainless steel sections fabricated by laser-welding, hot-rolling and extrusion

This paper presents an experimental investigation on the structural performance of austenitic stainless steel columns with open sections fabricated by laser-welding, hot-rolling and extrusion. The aim of the experimental programme was to quantify and compare the effect that different fabrication techniques have on the structural behaviour of the columns. The investigated cross-sections were extruded and laser-welded I-sections with the American designation S5x10, and hot-rolled and laser-welded channel sections with the European designation UAP 120x60x6. All sections were fabricated from austenitic stainless steel grade 1.4307/1.4301 (dual certified). The experimental programme consisted of stub and long column tests, as well as measurements of all the parameters that were considered to have an impact on the structural behaviour of the sections, including: material properties, cross-sectional geometry, residual stresses and global geometric imperfections. The tests showed that although the residual stresses and geometric imperfections of the austenitic stainless steel laser-welded columns are similar to those of the extruded/hot-rolled columns, their structural performance was noticeably better than that of the extruded sections, and equivalent to that of the hot-rolled sections. The experimental data was also used to assess the adequacy of the European column curves for laser-welded and hot-rolled open sections susceptible to flexural buckling about the minor axis. It was found that while for laser-welded I-sections it may be possible to justify a higher buckling curve, more research is needed for channels.

Influence of cyclic hardening characteristic on seismic performance of welded austenitic stainless steel H-section beam-column

Previous studies have revealed that the cyclic hardening feature of austenitic stainless steel depended on the applied strain amplitude and exhibited unsaturation prior to failure, which greatly affected the seismic response of austenitic stainless steel structures. In view of the limited research on the seismic performance and design of structural stainless steel members, this study investigates the influence of cyclic hardening characteristic on the performance of welded austenitic stainless steel H-section beam-column under combined uniaxial cyclic bending and constant compression. The finite element (FE) models of unsaturated cyclic hardening austenitic stainless steel grade S30408 beam-columns with H-section were initially created and validated with the available test data. The effects of loading history in conjunction with the axial compressive load level and the cross-section slenderness on the seismic performance of specimens were then studied through extensive parameter analysis. Results show that the capacities of load-carrying and deformation for the austenitic stainless steel member are discrete under different loading histories. Apparently, the unsaturated cyclic hardening property of stainless steel S30408 influences the performance of the member under seismic loading. Moreover, current codified design methods and the Continuous Strength Method (CSM) underestimated the ultimate strengths of stainless steel beam-columns under seismic loading. The over-strength factor and seismic deformation capacity design formulae of welded austenitic stainless steel H-section beam-columns were finally proposed.

Analyze the Effect of Weld Heat Input on Mechanical Properties of Nitrogen Alloyed Stainless Steel by GMAW Process

GMAW process in the recent research work investigates the effect of heat input, feed rate, voltage, current (controlled by GMAW Process) on the tensile strength, micro-hardness and microstructure of nitrogen alloyed stainless steel (JT grade). The base material used for the investigation was Nitrogen Grade austenitic stainless steel (JT Grade) with the low percentage of nickel content. JT grade steel has good resistance to oxidation, easy fabrication, and excellent toughness even in the low temperatures. It is not expensive as lower cost nitrogen and manganese are added as partial alternative for nickel. The yield and ultimate tensile strength of the base metals and welding filler was to be calculated to get the best desirable properties of the welding process. The microstructure, macro-structure and chemical test on the metal plates were done to study about their properties. The numbers of trials are to be done for getting the best and appropriate parameters. And the last testing were done on the best parameters( heat input, voltage, current) on the base metal of JT grade to test the micro- hardness and tensile strength of the metal and welding. The 3 types of filler metal ER308L, ER309L, and ERNiCrMo3 were used during the welding process in GMAW to study these effects. The hardness were tested at the HAZ area and WELD area and the location of fracture from welding area were consider during the testing to get the tensile strength of the weld.

Evaluation of Microstructure High Chrome Austenitic Stainless-Steel grade 253MA after Creep Test at Temperature of 700°C

High Chrome Austenitic Stainless-Steel grade 253 MA is a material that widely used for high temperature. This is due the fact this material has excellent mechanical properties and creep resistance. However, changes in microstructure can occur in long-term use, which will affect the creep resistance (shortened service life of the material). The microstructure of High Chrome Austenitic Stainless-Steel 253 MA creep test specimens was investigated. Creep testing at a temperature of 700 °C with a loading of 150 MPa was carried out. The cold rolling process with 53% reduction in thickness was applied followed by annealing at 900°C, 1000°C, and 1100°C for 3600s to obtain different grain size. Grain size after annealing and after creep test was measured to see the effect of annealing temperature on the grain size of tested steel and to see its effect on creep resistance based on the creep test conducted. Grain size and morphology of the phase after creep test were observed by scanning electron microscope and optical microscope

The study of sigma and carbide in cast austenitic stainless-steel grade HH after 24 years of high-temperature service

Cast austenitic stainless steel (CASS) has been widely used for long-term service periods in high-temperature applications. Nonetheless, the behavior of CASS after high-temperature and long-term service is insufficiently researched alongside the microstructural analysis for sigma phase and carbide. Here, intermediate pipe support made from CASS grade HH was investigated after 24 years of service at 700 °C and compared with the solution-treated specimen at 1100 °C for 2 h. The chemical composition was analyzed by optical emission spectroscopy (OES), while the microstructure was observed using optical microscopy and scanning electron microscope (SEM). The confirmation of phase composition and lattice parameters were further analyzed by energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction spectroscopy (XRD). The mechanical properties were assessed by tensile tests, hardness tests, and impact tests, whereas the corrosion property was analyzed using potentiodynamic polarization. Based on experiment and analysis, the effects of 24 years of exposure on the sigma phase are spheroidization and Cr depletion, and even partial transformation to ferrite. The sigma phase significantly increases the hardness, but Cr depletion slightly reduces the hardness to 96.86 HRB. Meanwhile, the carbide will increase in quantity and develop an irregular interface at long-term high-temperature exposure. Microstructure evolution of the sigma phase and carbide decreased tensile strength to 46%, elongation to 3%, and impact value to 1.6% of the minimum specifications, respectively, while the corrosion rate increased 10 times (about 7.35 μm per year).

Investigation of the interaction of liquid tin-lithium alloy with austenitic stainless steel at high temperatures

This paper describes research work to determine the corrosion compatibility of material of the capillary-porous structure (CPS) matrix with a liquid tin-lithium (Sn-Li) alloy at high temperatures. The studies were carried out with the Sn-Li alloy containing 73 at.% of tin and 27 at.% of lithium and samples of 12Cr18Ni10Ti grade austenitic stainless-steel. This steel was proposed as one of the options as a candidate material for the Sn-Li CPS matrix manufacturing. Experiments on the interaction of a liquid Sn-Li alloy with stainless-steel at high temperatures were carried out on the TiGrA experimental facility based on the Mettler Toledo TGA/DSC 3+ thermogravimetric analyzer. The temperature gap in corrosion experiments ranged from 600 °C to 1000 °C, the interaction time for each temperature level was about 10 h. In the course of the work, experiments were carried out to study the compatibility of a Sn-Li alloy in the liquid phase with stainless-steel at temperatures of 600 °C, 800 °C and 1000 °C. Post-experimental studies of stainless-steel samples were carried out using microstructural and energy-dispersive analysis. Based on the results obtained, it was determined that when stainless-steel interacts with an Sn-Li alloy at high temperatures, complex physical-chemical processes occur, such as: selective dissolution of steel components by a liquid alloy; permeation of the liquid alloy into stainless-steel; mass transfer of dissolved metals from a solid metal to a liquid one.

Optimization of material and process parameters for plasma transferred arc hard facing for high temperature applications

The authors in this research paper have investigated the process of hardfacing, which is a well-established manufacturing process for increasing the durability of industrial components, which are subjected to extreme wear, erosion, abrasion. The objective of this study is to establish a scientific methodology to select the most suitable combinations of materials as base-deposition materials for hardfacing, specifically focusing on Nickel-based and Cobalt-based materials. In order to make an informed decision, multi-criteria decision-making method known as “Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS)” is used. This technique permits to deal with wide range of important factors, such as the materials' high-temperature resistance, wear resistance, and corrosion resistance, among others. The paper discusses a step-by-step approach to selecting the best alternative material for hardfacing by considering eight different criteria and assigning preferences to each of the available materials. The results of this methodology suggested that Stellite-6 based cobalt-based alloy is best suitable for AISI 304 grade austenitic stainless steel materials used for high temperature applications.In addition, the paper also studies the effects of various welding parameters on the hardfacing process. This includes parameters such as welding current, welding speed, powder feed rate and the type of shielding gas used. The significance of each parameter is also studied, and the results of these investigations are discussed in detail. Overall, this research paper provides a comprehensive overview of the hardfacing process and the materials and techniques that are best suited for it, making it valuable resource for professionals and researchers in the field.

Shear resistance and design of stainless steel plate girders in fire

In this paper, the shear resistance and design of stainless steel plate girders at elevated temperatures are investigated. A broad range of parameters influencing the structural response of stainless steel plate girders in fire are taken into account, considering (i) austenitic and duplex stainless steel grades, (ii) rigid and non-rigid end posts, (iii) different aspect ratios for the unstiffened portions of the plate girders, (iv) various web slendernesses and (v) different elevated temperature levels. The influence of these parameters on the behaviour of stainless steel plate girders at elevated temperatures is considered. Currently, there is an absence of specific design rules on the fire design of stainless steel plate girders in the European structural steel fire design standard EN 1993-1-2. Considering this, an accuracy assessment of the room temperature stainless steel plate girder design recommendations of the European structural stainless steel design standard EN 1993-1-4 applied with the elevated temperature material properties of stainless steel is performed. The results indicate that this approach leads to unsafe and scattered ultimate strength estimations for stainless steel plate girders in fire. New fire design recommendations for stainless steel plate girders that are in accordance with the existing design provisions of EN 1993-1-2 and EN 1993-1-4 are proposed. The accuracy and safety of the proposed new design recommendations are comprehensively verified against the results from nonlinear finite element modelling.

Corrosion of alumina-forming austenitic alloys under the supercritical carbon dioxide-based venus atmospheric surface conditions

Several grades of alumina-forming austenitic (AFA) stainless steel (SS) alloys were probed after exposure to simulated sCO2-based 467 °C Venus surface atmospheric conditions using the NASA Glenn Extreme Environments Rig (GEER) for 30 days. AFA samples were characterized by gravimetric analysis, X-ray diffraction (XRD), and electron microscopy. All AFA samples formed multilayered scales in which the outer layer is mainly magnetite (Fe3O4) and nickel sulfides (Ni3S4, Ni4S3), and the inner layer is mainly chromia containing aluminum, (Cr,Al)2O3. The most resistant of the AFA alloys exhibited specific weight gain corrosion resistance similar to SS304, which formed an inner (Fe3−xCrxO4) spinel.

Temperature Effect on Deformation Response in Austenitic Stainless Steel

Stress-strain behavior of austenitic stainless steel grade AISI 304 was investigated by means of uniaxial tensile tests and magneto-phase analysis. The test materials were strained in tension within the temperature range of-100 ≤ T ≤ +100 °C. According to the results, intensive strain hardening occurs in austenitic stainless steel when strain-induced α’- martensite is present in the material, and stress-strain behavior is associated with the increase yield strength and tensile strength with decreasing temperature. The analysis of the hardening kinetics reveals that kinetics are affected by the temperature and by the amount of α’- martensite content.

Hydrogen Embrittlement Behavior of Plastically Pre-Strained and Cathodically Hydrogen-Charged 316H Grade Austenitic Stainless Steel

In this work, the effects of electrochemical hydrogen charging of 316H grade austenitic stainless steel were investigated in order to characterize its hydrogen embrittlement (HE) resistance. The as-received 316H material was in a fully recrystallized (solution-annealed) material condition. The susceptibility to HE of the studied material was evaluated by determination of the embrittlement index from the results of conventional uniaxial tensile tests of nonhydrogenated and hydrogen-charged test specimens. The study was focused on the effects of two selected plastic pre-strain levels of tensile specimens on their resulting HE resistance. The selected pre-strains corresponded to the tensile stress conditions within the “yield stress–ultimate tensile strength” (YS–UTS) range and directly at the UTS point. The obtained embrittlement indices for the presently used pre-straining and hydrogen charging conditions indicated that the HE of the studied material states was small. However, it was revealed that the observed degradation of deformation properties of plastically pre-strained and hydrogen-charged materials was mainly caused by gradual plasticity exhaustion due to tensile straining, which well correlated with the observed effects indicated by electron backscatter diffraction analyses and indentation hardness measurements.

Mechanical properties of plasma arc welded AISI304LN austenitic stainless steel at various temperatures

ABSTRACT AISI 304 grade austenitic stainless steels are widely used in a wide variety of fields such as chemical, automobile, food industries, etc. due to their good mechanical properties and corrosion resistivity. In this study, AISI 304LN austenitic stainless-steel couples were joined with plasma arc welding. The effect of temperature on the mechanical properties, formability and fracture morphologies of joints was evaluated. For this purpose, tensile testing of the joints was carried out in the temperature range of –50°C, and 25°C–850°C. Thus, the ultimate tensile strength, (UTS), yield strength, (YS) and elongation (EL%) amounts of welded joints were determined. The fracture morphologies of the tensile test samples were examined. It was observed that the rupture (except 850°C) occurred from the weld metal. The highest formability was obtained in the samples tested at 850°C. In addition, the existence range of dynamic strain aging (DSA) of the plasma arc welded samples was also investigated. The unsteady plastic flow between the yield and the ultimate tensile of the sample subjected to the tensile test at 250–550°C are evaluated as signs of DSA.

Influence of heat treatment on the mechanical and the lubricant wear characteristics of stainless-steel grades against 5 wt% NaCl as industrial shielding materials

This article investigates the impact of the heat treatment, and lubricant wear measurements at 5 wt % NaCl solution, mechanical and radiation shielding properties of three grades of stainless steels: SS316, M303, and SS201. The obtained results showed that heat-treated martensitic stainless-steel grade has improved mechanical and tribological properties while heat-treated austenitic stainless-steel grades showed deteriorated wear resistance. The radiation shielding parameters of the studied grades are comparable. The effectiveness of heat treatment in the presence of NaCl solution is verified.

Effect of Nb-free consumables on the microstructure and structural integrity of pressure vessel grades of dissimilar austenitic stainless steel welded joints

The research article demonstrates the role of fillers in the evolution of the microstructure and mechanical integrity of dissimilar joints of stabilized austenitic stainless steels. Pulsed direct current (PDC) gas tungsten arc welding (GTAW) technique was adopted to obtain the joints of dissimilar grades of stabilized austenitic stainless steels such as AISI 321 and AISI 347. The joints of these dissimilar grades of stainless steels were achieved using a ferritic-austenitic stainless-steel filler ER2553 and Ni-rich austenitic fillers ERNiCrMo-4, ERNiCrMo-10. Delta ferrite was observed in heat-affected areas (HAZ) on both sides of stainless steels, regardless of joints. Precipitation of Mo–Nb, Mo–W rich phases was noticed in the fusion zones (FZ) while adopting Ni-based austenitic fillers. During the tensile load, the fractures occurred on the base metal side of the AISI 321 for the Ni-based fillers and on the FZ while using the ER2553 fillers. The joint efficiencies achieved by these dissimilar joints were 103.2%, 128.11% and 116.16% for ER2553, ERNiCrMo-4 and ERNiCrMo-10 fillers respectively. The joints established with the ERNiCrMo-4 filler improved the notch's impact resistance in ambient temperature and below zero conditions compared to other weld seams.