Low Nickel Austenitic Stainless Steel Research Articles

Influence of inconel interlayer on microstructural, mechanical and electrochemical characteristics in single-pass ATIG welding of dissimilar austenitic and duplex stainless steel

This study investigates the impact of Inconel 625 interlayer on dissimilar welded low nickel austenitic stainless steel (LNiASS) and super duplex stainless steel (S32760) using activated tungsten inert gas (ATIG) welding. Two weldments were prepared: with and without (autogenous) interlayer. Geometrical investigation of the weld cross sections revealed that interlayer-based welding significantly increased the depth of penetration and decreased weld width as compared to autogenous welding at the same welding current. The dual microstructure was observed in the weld zone (WZ) of autogenous weldment while fully austenitic structure with few intermetallics was observed in the WZ of interlayer-based weldment. Mechanical properties, particularly impact strength observed to be improved in the case of interlayer-based weldment (91 ± 2 J) compared to autogenous weldment (68 ± 2 J). Lower microhardness was noticed for the WZ of interlayer-based weldment (258 ± 3 HV0.2) than WZ of autogenous (279 ± 2 HV0.2) weldment due to the presence of higher content of Ni. However, UTS of interlayer-based weldment (654 MPa), falls short in comparison to the autogenous weldment (693 MPa), indicating a compromised joint efficiency of 5.96%. The corrosion resistance was observed to be higher for the WZ of interlayer-based weldment attributed to the higher content of Ni and Mo. The sensitization study revealed 47.33% degree of sensitization in the WZ of autogenous weldments due to dual microstructure, while interlayer-based weldments showed no sensitization.

Dissimilar welding of AISI 201 and 202 low nickel stainless steels by GTA and PA welding processes

This paper presents the results of dissimilar joining techniques for AISI 201 and 202 low nickel austenitic stainless steels. These were welded by Gas Tungsten Arc Welding (GTAW) and Plasma Arc Welding (PAW). The tests were performed to examine the weld bead shapes, microstructure, mechanical properties and corrosive behavior of the weld metals with different welding processes. The weld bead shape by GTAW was larger than that performed by PAW. The microstructure of the weld metal produced by GTAW contained more delta ferrite in the austenite matrix than the weld metal produced by PAW. The volume of hardness in welds produced by PAW higher than the GTAW process same with the ultimate tensile strength and percentage elongation welds produced by PAW higher than the GTAW process. According to the potentiodynamic polarization test results, pitting corrosion resistance of the weld produced by PAW was higher than the weld produced by GTAW. Both weld metals showed the pitted area adjacent to the phase boundary between austenite and delta ferrite in the mixed microstructure. Based on the present work, it was concluded that PAW was the more suitable welding procedure for joining dissimilar 201 and 202 austenitic stainless steels.

Understanding the microstructural evolution and tensile characteristics of low nickel austenitic stainless-steel welds fabricated by diode LASER

In the present investigation, the utilization of diode laser welding in both continuous wave (CW) and pulse wave (PW) modes was applied to weld sections of 4 mm thick low nickel austenitic stainless steel (LNiASS) material. Subsequently, a comprehensive examination of the microstructural attributes of these welds was conducted by X-ray diffraction, electron backscatter diffraction (EBSD), and electron channeling contrast imaging (ECCI). The microstructural assessment was performed at both as-welded state and after the tensile deformation at three discrete strain rates ranging from 3.3 × 10−4 to 1.0 × 10−2. Furthermore, an investigation into the influence of strain rate variations on the tensile behavior of the two aforementioned types of welded joints, along with an exploration of the occurrence of strain-induced martensitic transformation, was carried out. The outcomes revealed that the PW welds yielded finer grain sizes in comparison to CW welds. It was observed that the martensite content within both CW and PW welds exhibited an augmentation with increasing strain rates. Furthermore, the PW welds exhibited a higher martensite content when compared to the CW welds under all examined strain rates. The PW welds consistently demonstrated higher UTS and total elongation across all three strain rates, while the CW welds exhibited a higher YS. Furthermore, as the strain rates increased, a decline in the strength ratio was observed for both weld types, accompanied by an increasing disparity between UTS and YS, indicative of work hardening phenomena.

Study on wear behavior of low nickel austenitic stainless steel by using ball on disc

Austenitic stainless steels have wide applications in various industries due to its good corrosion characteristics and their surface strength. A variety of procedures are used to enhance the surface characteristics. Wear studies are critical in all of the toughest materials. Surface damage was studied in terms of material-removal methods such plastic deformation and brittle fracture. This paper investigated the specific wear rate of Low Nickel ASS. The parameters selected for wear testing like sliding speed, load, time duration and types of ball. Six numbers of experiments were conducted for measuring specific wear rate, mass loss and coefficient of friction were highlighted in this paper. A comparison study was made to know the effect of wear parameters like sliding speed, load, time duration and types of ball on specific wear rate and coefficient of friction. It was seen that with increasing of load and sliding speed of disc the specific wear rate of the material significantly increasing.SEM analysis was also made on worn surface to know the behaviour of wear in the sample.

Enhancement of corrosion protection of AISI 201 austenitic stainless steel in acidic chloride solutions by Ce-doped TiO2 coating

Ce-doped TiO2 coatings were applied by electrodeposition on a low-nickel austenitic stainless steel (AISI 201) bearing 8 wt% Mn to improve the electrochemical properties in acidic chloride solutions. Characterization of the Ce-doped TiO2 coatings was performed by a scanning electron microscope equipped with energy dispersive X-ray spectroscopy (EDS) to study the tiny features. The corrosion behavior of the bare and coated steel was evaluated in aqueous acidic chloride solutions mixing with different chloride concentrations, 1 mol·L−1 H2SO4 with 0–1.5% NaCl. Potentiodynamic polarization tests were conducted to evaluate the corrosion characteristics, corrosion potential Ecorr and corrosion current density icorr. Further study concerning the weight loss (WL) using immersion tests for the long-term was conducted to determine the bare and corresponding coated steel's equivalent corrosion rates. It was found that the electrodeposited Ce-doped TiO2 coatings with a layer thickness of ~1 μm enhance the corrosion resistance of the coated steel in the acidic chloride solutions compared to its counterpart, the bare steel. The polarization tests showed that the icorr of the Ce-doped TiO2 coated steel significantly declined to a half value of the bare steel. The Ecorr for all coated specimens shifted to a more positive value when compared with those of the bare steel. The WL measurements displayed that the bare AISI 201 steel experiences intensive corrosion degradation in the presence of a low concentration of chloride ions. However, the Ce-doped TiO2 coatings significantly resist the aggressive chloride ions and consequently increase the corrosion resistance of the steel.

Corrosion Behavior of Ni-Based Metallic Coatings Deposited by Thermal Spray Method on Low Nickel Austenitic Stainless Steel

Corrosion Behavior of Ni-Based Metallic Coatings Deposited by Thermal Spray Method on Low Nickel Austenitic Stainless Steel

The features of metal dusting process in the extremely low nickel austenitic stainless steel (18Cr-21Mn-0.65N-Fe)

The features of metal dusting in extremely low nickel austenitic stainless steel (18Cr-21Mn-0.65N-Fe) were studied in syngas environment (75% H2 and 25 %CO) at 400-700 °C, under cyclic exposure for 300 h. Carbon corrosion occurred at 400-500 °C, however, at 600-700 °C, oxidation of Mn and formation of Mn-Cr-O spinels significantly reduced the carbon attack. The surface and cross section of the exposed coupons were examined by XRD, SEM(EDS) and EPMA. Metal dusting resulted in formation of very few corrosion pits of the size 2-7 μm and epitaxial growth of carbon nanotubes on the surface exposed at 400-500 °C.

Corrosion characteristics and fuel cell performance of a cost‐effective high Mn–Low Ni austenitic stainless steel as an alternative to SS 316L bipolar plate

In this study, newly developed high manganese (Mn) and low nickel (Ni) austenitic stainless steels were investigated as an alternative to conventionally used SS 316L for bipolar plate applications in proton exchange membrane fuel cells. Systematic studies on the corrosion behavior were carried out in simulated hydrogen and oxygen environments, for both half- and fuel-cell conditions. The Mn-based SS revealed nobler corrosion potential and comparable passive current densities to that of SS 316L. The passive current density of Mn-based SS is well within the DoE 2020 target of <1 μA cm−2. Though MnSS1 steel has lean Ni content, the addition of Mn and N is beneficial for improving the corrosion performance, which is comparable to SS 316L. The recorded ICR values for Mn SS1 and SS 316L are 234.6 ± 20 and 155 ± 20 mΩ cm2 at a compaction force of 140 N cm−2, respectively. Both the steels do not to meet the DoE ICR target of 10 mΩ cm2, which requires conductive coating or improvement in oxide conductivity. The performances of the steels (both Mn-SS and 316L SS) with varying thickness were also investigated in a single fuel cell condition with serpentine flow field design as bipolar plates with varying thickness (10, 5 and 2 mm). A maximum power density of 370 mW cm−2 was achieved with the Mn-based metallic bipolar plates, whereas SS 316L showed 354 mW cm−2. By changing the composition of austenitic stainless steel, that is, using Mn SS1 instead of SS 316L the overall fuel cell cost decreases by three times.

CAFE simulation of directional solidification structure of low nickel austenitic stainless steel

In this paper, through the secondary development of ProCAST&CAFE software, the dynamic boundary conditions of solidification process were established, the temperature field and solid fraction in the directional solidification process of low nickel austenitic stainless steel were simulated, and the effect of the pull rate on solidification microstructure was discussed. The results shows that the withdrawal rate is in the range of 15~200 μm/s, as the solidification speed increases, the isotherm becomes dense, gummy zone narrowing. And as the solidification rate increases, the primary dendrite arm gradually refines and the secondary dendrite arm becomes dense and coarse. In addition, as the withdrawal rate increases in the range of 15 to 200 μm/s, the lateral heat dissipation of the edge of the casting is gradually smaller than that of the central longitudinal heat dissipation, and the axial deviation of the dendrites is reduced from 27.66 ° to 25.964 °. At the same time, the comparative analysis simulation results are in good agreement with the experimental results, and the simulation calculation process is more reasonable.

Effect of ultrasonic shot peening on strain controlled fatigue behaviour of low nickel austenitic stainless steel

In the present investigation effect of Ultrasonic shot peening (USP) treatment on strain controlled fatigue behavior of low nickel austenitic stainless steel (Low Ni ASS) was studied at room temperature. The gauge section of fatigue samples were USPed with 2 mm diameter hard steel shots for 3 min. Microstructural characterization of the USP treated samples were carried out using XRD, SEM and TEM techniques. Refinement of grains in the surface region was observed and grain size was found to be ≈17 nm from quantitative analysis of XRD patterns. Strain controlled fatigue tests were carried out at different total strain amplitudes (Δεt/2) ranging from ±0.4% to ±0.8%. Fatigue life was increased significantly by 200% at lowest Δεt/2 of ±0.4% whereas it was reduced at highest Δεt/2 of ±0.8% by 50%. Fracture surfaces were characterized using SEM.

Enhancement of corrosion protection of low nickel austenitic stainless steel by electroactive polyimide-CuO composites coating in chloride environment

Purpose The purpose of this study is to improve the anticorrosion performance of low nickel stainless steel (AISI 201) in 3.5% NaCl by electroactive polyimide/copper oxide (EPI/CuO) composites coating. Design/methodology/approach Electroactive polyimide/copper oxide (EPI/CuO) composites were prepared by oxidative coupling polymerization followed by thermal imidization method. Findings The functional and structural properties of composites were characterized by X-ray diffraction, Fourier transmission infra-red and ultra violet-visible spectroscopy and the surface topography was characterized by field emission scanning electron microscope analysis and anticorrosion performance in 3.5 Wt.% NaCl was evaluated by electrochemical techniques. The obtained results of electrochemical techniques measurement indicated that the composites coated samples give better corrosion protection against attacking electrolyte. Originality/value The ever-increasing price of nickel (Ni) is driving the industries to use low-Ni austenitic stainless steels (ASSs). However, it exhibits relatively poor corrosion resistance as compared with conventional Cr-Ni ASSs. Nonetheless, its corrosion resistance can be enhanced by polymeric (electroactive polyimide [EPI]) coating. CuO particles exhibit the hydrophobic properties and can be used as inorganic filler to incorporate in EPI to further enhance the corrosion protection. The present research paper is beneficial for industries to use low-cost AISI 201, enhance its corrosion resistance and replace the use of costly conventional Cr-Ni ASSs.

Role of surface oxide layers in the hydrogen embrittlement of austenitic stainless steels: A TOF-SIMS study

Hydrogen environment embrittlement (HEE) of low-nickel austenitic stainless steels (AISI 300 series) with different chemical compositions was studied focusing on the impact of the steels surface oxides, grain sizes and dislocation arrangements. The susceptibility of the steels to HEE is judged with respect to the relative reduction of area (RRA), where the HEE susceptibility is lower for larger RRA values.For many AISI 300 steels a linear trend is observed correlating RRA and the probability of strain induced martensite formation in tensile tests. Some steels, however, depart from the general trend, revealing greater HEE resistances.A careful examination of possible factors influencing HEE of the investigated steels reveals that high RRA values are linked to a specific type of oxide layer, namely the “high constant level oxide”, as categorized by TOF-SIMS evaluation. Thus, this type of oxide layer may be able to lower the steels HEE susceptibility. Other types of surface oxides, grain sizes and dislocation arrangements in the matrix of the particular AISI 300 steels appear to be of secondary importance.

Relationship between hydrogen embrittlement and Md30 temperature: Prediction of low-nickel austenitic stainless steel's resistance

Hydrogen embrittlement (HE) of several low-nickel austenitic stainless steels (AISI 300 series) was studied with special attention to the impact of strain induced α′-martensite. The susceptibility of the steels to HE is judged with respect to the relative reduction of area (RRA): The HE susceptibility is lower for larger RRA-values. Strain-induced martensite formation was evaluated within in the framework of the Olson-Cohen model, revealing a linear relationship between RRA and the probability β of martensite nucleus formation in the steels. In order to widen the scope of data evaluation to literature data, the consideration of a parameter alternative to β is required. It is demonstrated that among other parameters the Md30 temperature (Nohara), which assesses the stability against martensitic transformation, can serve as an indicator to predict HE of AISI 300 series steels. Regarding the Md30 temperature (Nohara), a trend-line with respect to the RRA-values is found. Thereby, the RRA-values of low-nickel austenitic stainless steels group into three distinct regimes; (1) for Md30 > −80 °C, where RRA-values decrease with increasing Md30 temperature, (2) at Md30 ≈ −80 °C, where RRA-values show a large variation (‘threshold band’), and (3) for Md30 < −80 °C, showing constant RRA-values of nearly 100%. Some RRA data points that deviate from the trend line can be explained by the special microstructure of the investigated samples.

Mechanical Behaviour of AISI 204 Cu Metastable Low Nickel Austenitic Stainless Steel Sheets at Various Constantly Maintained Elevated Temperatures

Mechanical Behaviour of AISI 204 Cu Metastable Low Nickel Austenitic Stainless Steel Sheets at Various Constantly Maintained Elevated Temperatures

Microstructural, mechanical and intergranular corrosion behavior of cold work and thermal ageing of low nickel austenitic stainless steel

In the present investigation, microstructural, mechanical and electrochemical properties of cold rolled Cr-Mn austenitic stainless steel were studied. Heat treatment (800 °C, 900 °C, 950 °C and 1000 °C) and thermal ageing (one, two and three hours) of surface were investigated using an optical microscope, scanning electron microscope. Mechanical characteristics like hardness and tensile strength were evaluated. Electrochemical test were carried out using double loop electrochemical potentio kinetic reactivation tests (DLEPR) for finding the degree of sensitivity (DOS). The results showed that without cold rolled, thermal aged for one, two and three hours, there was high sensitization at the temperature of 850 °C and 900 °C, but at the temperature of 950 °C and 1000 °C there was re-homogenization. The grain size increased with increase in temperature. With cold rolled samples, there was a reduction in grain size, increased in strength and hardness in the samples, which is due to the formations of strain induced martensite (SIM). With the increase in thermal duration (1, 2 and 3 h) there was an increase in martensite formation at temperature of 850 °C and 900 °C. At temperature of 950 °C and 1000 °C, work hardening diminished. Also, it was observed that increase in strain induces martensite which in turn increases degree of sensitization (% DOS).

Corrosion Properties of a Low-Nickel Austenitic Porous Stainless Steel in Simulated Body Fluids

Nickel can cause severe allergic reactions. Therefore, efforts are made to reduce the content of nickel in austenitic stainless steels (SS). Powder metallurgy (PM) techniques can produce this steel in a highly affordable way. A novel low-nickel high-nitrogen austenitic powder metallurgy PM stainless steel is investigated in terms of corrosion behavior. Nitrogen, because of its gammagenic effect, is the applied sintering atmosphere. Two sintering processes are applied by controlling the sinter-cooling rate (furnace- and water-cooling). This material shows an austenitic microstructure free of precipitates only after the water-cooling process. The electrochemical behavior in two simulated body fluids—phosphate buffered saline (PBS) solution and Ringer solution—are studied. Corrosion behavior is evaluated by means of anodic polarization measurements and cyclic polarization curves. In addition, Electrochemical Impedance Spectroscopy is used to evaluate the corrosion resistance of this steel in PBS at open circuit potential and at 100 mV above corrosion potential. The water-cooling process promotes better corrosion behavior in simulated body fluids for high nitrogen and low nickel than a conventional (high nickel) austenitic PM SS 316LN type.

Low Activation-Modified High Manganese-Nitrogen Austenitic Stainless Steel for Fast Reactor Pressure Vessel Cladding

Low and free nickel austenitic stainless steel alloys were developed successfully and proposed to be used as a liquid sodium coolant fast reactor pressure vessel cladding. A standard austenitic stainless steel SS316L (AISI 316L) was produced as a reference sample. The nickel content was partially or totally replaced by manganese and nitrogen. The microstructure of the produced stainless steel alloys was investigated using Schaeffler diagram, optical microscopy and X-ray diffraction patterns (XRD). Mechanical properties of the developed stainless steel grads were investigated using Vickers hardness, impact and tensile tests at room temperature. Sodium chloride was used to study the corrosion rate of the investigated alloys by open circuit potential technique. Slow and total slow neutrons removal cross sections were measured using 241 Am-Be neutron source and highly calibrated He-3 detector. Eight gamma ray lines which emitted from 60 Co and 232 Th radioactive sources and HPGe detector were used to study the attenuation parameters of the produced alloys. Metallography, Schaeffler diagram and XRD results showed that all the produced stainless steels are mainly of austenite phase with a small ferrite phase. The developed manganese-nitrogen stainless steels showed higher hardness, yield and ultimate tensile strength than SS316L. The elongation of developed stainless steels is relatively lower than the standard SS316L. The impact toughness was reduced with replacement of Ni by Mn. The developed manganese stainless steels have a higher total slow removal cross section than SS316L. On the other hand, the slow neutron and gamma rays have nearly the same behavior for all studied stainless steels.

Microstructural and Electrochemical Evaluation of Fusion Welded Low-Nickel and 304 SS at Different Heat Input

The present research study investigates the effect of heat input using E 308 electrode (controlled by welding current, i.e., 70, 85 and 100 A) on microstructure, mechanical properties and corrosion behavior of low-nickel and 304 stainless steel (SS) weldments produced by shielded metal arc welding technique. SEM investigation shows that with the higher heat input, δ-ferrite content was reduced. Dendrite and inter-dendritic length is also reduced by lowering the heat input. For all the heat inputs, it is observed that δ-ferrite content was higher in 304 stainless steel (SS) as compared to that of low-nickel austenitic stainless steel (Cr-Mn SS). Considering the heat input for Cr-Mn SS, coarse grains were observed in the heat-affected zone region. For low heat input (LHI), tensile fracture surface has exhibited river-like pattern with dimple appearance. Corrosion studies show better pitting resistance for low heat input (LHI) samples due to higher δ-ferrite present in the weld region. Similarly, higher interphase corrosion resistance is observed in both the SS grades causing more dissolution in the LHI samples.

Characterization of friction stir welded joint of low nickel austenitic stainless steel and modified ferritic stainless steel

Friction stir welding (FSW) of dissimilar stainless steels, low nickel austenitic stainless steel and 409M ferritic stainless steel, is experimentally investigated. Process responses during FSW and the microstructures of the resultant dissimilar joints are evaluated. Material flow in the stir zone is investigated in detail by elemental mapping. Elemental mapping of the dissimilar joints clearly indicates that the material flow pattern during FSW depends on the process parameter combination. Dynamic recrystallization and recovery are also observed in the dissimilar joints. Among the two different stainless steels selected in the present study, the ferritic stainless steels shows more severe dynamic recrystallization, resulting in a very fine microstructure, probably due to the higher stacking fault energy.

Effect of Welding Processes on Microstructure, Mechanical Properties, and Corrosion Behavior of Low-Nickel Austenitic Stainless Steels

In the present study, the influence of welding process on metallurgical, mechanical, and corrosion behavior of shielded metal arc welding and tungsten inert gas welding was explored using 308L electrode. Tungsten inert gas welding exhibited equiaxed grains, having better hardness and tensile strength than that of its counterpart. It is observed that heat-affected zone and unmixed zone of shielded metal arc welding is wider than tungsten inert gas welding. Dendrite length and inter-dendritic distance are smaller for tungsten inert gas welding. The volume fraction of ferrite is found to be higher in tungsten inert gas welding. The base metal shows higher ductility than both the weld; also, the ductility of tungsten inert gas welding was marginally better than shielded metal arc welding. Modified Strauss test shows intense grain dropping and strength reduction in both the process. The pitting corrosion resistance is found to be better for tungsten inert gas welding as compared to shielded metal arc welding. The galvanic current shows higher current density when couples are formed with base metal and weld zone produced by tungsten inert gas welding.