UNS S31803 Duplex Research Articles

Evaluation of the Magnetic Permeability for the Microstructural Characterization of a Duplex Stainless Steel

Abstract Non-destructive testing has been commonly used to assess the presence of discontinuities that may affect the integrity of materials in service. In this study, a Hall-effect sensor is used in a methodology developed to study, in a non-destructive manner, the microstructural variations of a material that occur because of the single-phase decomposition. The material selected was the UNS S31803 duplex stainless steel, particularly because of its behavior at temperatures below 525°C. Measurements of magnetic permeability based on Hall voltage values were performed, as well as hardness measurements and x-ray diffraction studies. The results confirm that the magnetic permeability can be used to successfully track the formation of α′ phase from α phase in a duplex stainless steel.

Cavitation Erosion of Sensitized UNS S31803 Duplex Stainless Steels

During processing or use, duplex steels can be subjected to heating at high temperatures that can affect their behavior. This work aims to correlate the influence of the sensitization treatment on the ultrasonic cavitation erosion behavior of a UNS S31803 (X2CrNiMoN22-5-3) duplex stainless steel. Duplex stainless steels, formed as a result of rapid cooling after solution annealing, are sensitized at temperatures of 475 and 850 °C, respectively, leading to hardening and embrittlement due to the spinodal decomposition of the ferrite and the precipitation of secondary phases. The ultrasonic cavitation erosion experiments showed that the sensitization at 850 °C reduced the mean depth of erosion by about 11% and the mean depth of erosion rate by 28%. By contrast, the sensitization at 475 °C deteriorates the cavitation erosion resistance, increasing the erosion parameters by up to 22%, compared to the solution annealed state.

Optimization of process parameters of friction welding of UNS S31803 duplex stainless steels joints

This article presents an approach based on Taguchi method and Grey relational analysis to optimize process parameters of friction welding of UNS31803 duplex stainless steel. The main objective is to maximize mechanical properties like tensile strength, hardness and impact toughness and to minimize corrosion rate. Heating pressure, heating time, upsetting pressure and upsetting time were the four process parameters taken each at three levels. According to Taguchi quality design concept, an L9 orthogonal array was selected for experiments. The best combination of process parameters was found by both Taguchi method and Grey relational analysis. The influence of the process parameters on overall quality characteristics of the friction welding process was evaluated by the analysis of variance (ANOVA) method. The confirmation test results with optimal parameters confirmed the effectiveness of the proposed method in this study. Later, comparison was done between Taguchi method and Grey relational analysis on the basis of improvement in multi-response signal to noise (S/N) ratio over initial process parameters. Grey relational analysis was proved to be a better technique than Taguchi method for optimization of multiple responses.

Effects of post weld heat treatment on friction welded duplex stainless steel joints

In the present work, the effects of post weld heat treatment (PWHT) on friction welded UNS S31803 duplex stainless steel samples at three different temperatures namely 1080°C, 1150°C and 1200°C followed by water quenching were studied. Microstructural evaluations such as volume fraction of austenite/ferrite, grain size measurements, SEM-EDS, TEM and microhardness aspects were carried out. The volume fraction of ferrite to austenite ratio was balanced at 1080°C. Ni element is more effective in controlling the dual phase balance. Finer grains were obtained at 1080°C due to recrystallization effect. Microhardness was affected by reduction of ferrite percentage. Dual phase presence and absence of precipitates were conformed through XRD and TEM which follow Kurdjumov–Sachs relationship. Under the following: heating pressure: 40 heating time: 4 upsetting pressure: 80 upsetting time: 2 (Experiment no. 5) on PWHT at 1080°C, the balance of dual phase ratio, finer grains and increased microhardness were obtained.

Evaluation of Microstructural Effects on the Degree of Sensitization (DOS) of a UNS S31803 Duplex Stainless Steel Aged at 475°C

In this study, microstructural and electrochemical behavior of a UNS S31803 duplex stainless steel aged at 475°C were investigated. Hardness values increased with aging at 475°C and evidence of alpha prime (α′) phase formation was confirmed by transmission electron microscopy analysis. Double loop electrochemical potentiokinetic reactivation measurements in a 2 M H2SO4 + 0.5 M NaCl + 0.01 M KSCN solution showed an increase in the degree of sensitization values, mainly for the sample aged for 360 h at 475°C. Moreover, the results suggest that α′ phase formation occurred via spinodal decomposition mechanism.

Corrosion behavior of UNS S31803 steel with changes in the volume fraction of ferrite and the presence of chromium nitride

The goal of this study was to examine the changes caused in stress corrosion cracking and the critical pitting temperature behavior of a UNS S31803 duplex stainless steel due to variations in the ferrite fraction and the presence of chromium nitride in their microstructure. The steel plates were cold rolled and annealed at 1060°C. Microstructural variations in the plates were produced by thermal annealing treatments at 1200°C and 1300°C. Steel annealed at 1060°C showed greater resistance to stress corrosion cracking than steel annealed at 1300°C. Steel annealed at 1300°C had the lowest critical pitting temperature.

Corrosion of an UNS S31803 distillation column for acetic acid recovery

Unusually extended corrosion phenomena were detected in a distillation column, made of UNS S31803 duplex stainless steel, of a plant for the production of cellulose acetate. The process fluid was an aqueous solution of 80% acetic acid to separate by simple rectification. Corrosion was in the form of uniform attack mainly on downcomers and plates corresponding to the feedstock line.The phenomenon was a consequence of incomplete neutralization of sulphuric acid in the process fluid, used as a catalyst for the hydrolysis of esters. Controlled addition of H2O2 was proposed to solve the problem.

Finite element modelling and characterization of friction welding on UNS S31803 duplex stainless steel joints

Solid state joining techniques are increasingly employed in joining duplex stainless steel materials due to their high integrity. Continuous drive friction welding is a solid state welding technique which is used to join similar and dissimilar materials. This joining technique is characterized by short cycle time, low heat input and narrow heat affected zones. The simulation becomes an important tool in friction welding because of short welding cycle. In the present work, a three dimensional non-linear finite element model was developed. The thermal history and axial shortening profiles were predicted using ANSYS, a software tool. This numerical model was validated using experimental results. The results show that the frictional heating stage of the process has more influence on temperature and upsetting stage has more impact on axial shortening. The knowledge of these parameters would lead to optimization of input parameters and improvement of design and machine tools.

Electrochemical Impedance Spectroscopy Investigations of Stainless Steels in Presence of Corrosion Inhibitors

The behavior of corrosion and corrosion inhibition of AISI 1010 carbon steel, AISI 316 stainless steel and UNS S31803 duplex steel was studied in sodium chloride solution (3.0 wt. %), in the absence and presence of benzimidazole and imidazole corrosion inhibitors. The chemical and morphological characterization of steels were performed using the techniques such as optical emission spectrometry, optical microscopy, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). Electrochemical analysis were performed through the techniques of potentiodynamic polarization and electrochemical impedance spectroscopy. Metallographic, SEM and EDX analysis allowed to identify certain regions and elements present in the steel which provide corrosion occurring, such as inclusions.The electrochemical impedance results showed that the benzimidazole inhibition efficiencies were approximately 52%, 73% and 71%, respectively, for AISI 1010, AISI 316 and UNS S31803 steels. In the case of the imidazole was obtained efficiencies of about 96% for the AISI 1010 and AISI 316 steels and 85% for the UNS S31803 steel. Weight loss tests showed that for AISI 1010 steel, both benzimidazole and imidazole inhibit corrosion, and reduced the corrosion about 17% and 24%, respectively. In the analysis of the polarization curves in studies with seawater, it was observed that the inhibitors were lower efficient than in the middle chloride solution. The benzimidazole showed efficiencies of about 14%, 50% and 33% for AISI 1010, AISI 316 and UNS S31803 steels, respectively. In the case of Imidazole, it was observed that the inhibition efficiency of approximately 21%, 59% and 34% for the same steels, respectively. In all electrochemical analysis and weight loss test, imidazole proved to be the best inhibitor for the steels investigated. AcknowledgmentsFAPES, CAPES, FINEP, LMC and CNPq.

Multiobjective optimization of friction welding of UNS S32205 duplex stainless steel

Abstract The present study is to optimize the process parameters for friction welding of duplex stainless steel (DSS UNS S32205). Experiments were conducted according to central composite design. Process variables, as inputs of the neural network, included friction pressure, upsetting pressure, speed and burn-off length. Tensile strength and microhardness were selected as the outputs of the neural networks. The weld metals had higher hardness and tensile strength than the base material due to grain refinement which caused failures away from the joint interface during tensile testing. Due to shorter heating time, no secondary phase intermetallic precipitation was observed in the weld joint. A multi-layer perceptron neural network was established for modeling purpose. Five various training algorithms, belonging to three classes, namely gradient descent, genetic algorithm and Levenberg–Marquardt, were used to train artificial neural network. The optimization was carried out by using particle swarm optimization method. Confirmation test was carried out by setting the optimized parameters. In conformation test, maximum tensile strength and maximum hardness obtained are 822 MPa and 322 Hv, respectively. The metallurgical investigations revealed that base metal, partially deformed zone and weld zone maintain austenite/ferrite proportion of 50:50.

Effect of inorganic anions on the corrosion behavior of UNS S32750 duplex stainless steel in chloride solution

The present study explored the electrochemical behavior of UNS S32750, a super duplex stainless steel which was not commonly researched in previous studies. The effect of bicarbonate () and sulfate () on the electrochemical behavior of UNS S32750 duplex stainless steel in the chloride (Cl−) solution was investigated using potentiodynamic polarization, scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS), and Mott‐Schottky analysis. The electrochemistry behavior shows that with the addition of and , pitting potential increased and passive current density decreased, indicating that bicarbonate or sulfate can reduce sensitivity to pitting corrosion of UNS S32750 duplex stainless steel in Cl− solution, and film resistance (R1) and lower charge transfer resistances (R2) increased, and the carriers density (NA and ND) values are about 1020 cm3, and the carriers density decreases. The results may provide theoretical guidance for material‐choosing in the wastewater treatment industries containing high chloride concentration such as non‐ferrous metallurgical wastewater.

The impact of heat input on the strength, toughness, microhardness, microstructure and corrosion aspects of friction welded duplex stainless steel joints

The impact of heat input on mechanical aspects like joint strength, toughness, microhardness and metallurgical and corrosion characterization of UNS S31803 duplex stainless steel (DSS) in solid state continuous drive friction welding was studied. The experiments were carried out according to Design of Experiments (DOE) with L9 orthogonal array by varying the four different parameters namely friction pressure, friction time, upsetting pressure and upsetting time, keeping spindle speed as constant. Detailed analysis of fracture morphology, presence of elements and its distribution on joint zone were performed through scanning electron microscopy (SEM) attached with energy dispersive spectroscopy (EDS). No intermetallic phases were observed by X-ray diffraction (XRD) technique. Tensile strength results showed that higher the heat input the better was the preservation of joint strength. At room temperature, toughness decreased as heat input increased. At −100°C and −196°C, toughness of weld metal was comparatively higher than other fusion processes. Microhardness increased with an increase in heat input due to grain refinement. In addition, the corrosion behavior of the weld metal was also evaluated through potentio-dynamic polarization curve. Corrosion resistance of weld was better than that of base material and it is increased with an increase in the heat input.

Effect of volume fraction of phases and precipitates on the mechanical behavior of UNS S31803 duplex stainless steel

Mechanical properties of a grade UNS S31803 duplex stainless steel were studied. Samples were annealed at three different temperatures, 1060°C, 1200°C, and 1300°C, to change the α/γ proportion, to precipitate undesirable phases (for example, α′, σ and chromium nitrides), and to study the effect of the microstructure on the mechanical behavior. Specimens with a thickness of 1.8mm were prepared according to ASTM standards and tested at room temperature. Tensile tests were conducted using displacement control at a rate of 5mm/min. Force-controlled constant amplitude axial fatigue tests were conducted at a frequency of 30Hz and an R stress ratio of 0.1. Microstructural analyses, performed by optical microscopy and scanning electron microscopy, showed the following modifications to the microstructure: changes in the phase volume fractions, the phase grain growths, and the morphology of the γ-phase and the precipitation of chromium nitrides in the α-phase. The mechanical properties of the steel were significantly changed due to the changed microstructure. The results demonstrate the sensitivity of the steel to the annealing temperature.

Investigations on the structure – Property relationships of electron beam welded Inconel 625 and UNS 32205

• Joining of dissimilar metals of Inconel 625 and UNS S32205 using electron beam welding. • Detailed structure – property relationship of dissimilar welds. • Improved metallurgical and tensile properties from the EB welding. The metallurgical and mechanical properties of electron beam welded Ni based superalloy Inconel 625 and UNS S32205 duplex stainless steel plates have been investigated in the present study. Interface microstructure studies divulged the absence of any grain coarsening effects or the formation of any secondary phases at the heat affected zone (HAZ) of the electron beam (EB) weldments. Tensile studies showed that the fracture occurred at the weld zone in all the trials and the average weld strength was reported to be 850 MPa. Segregation of Mo rich phases was witnessed at the inter-dendritic arms of the fusion zone. The study recommended the use of EB welding for joining these dissimilar metals by providing detailed structure – property relationships.

Corrosion Properties and Impact Toughness of 2205 Duplex Stainless Steel after TIG Welding*

Abstract Application fields for duplex stainless steels are drastically increasing. Industries producing and operating petrochemical process equipment, pipelines, bridges, pressure vessels, heat exchangers, rotors, and sea-water systems have a high demand for these steels. In this study, UNS S32205 duplex stainless steel plates of 3 × 40 × 145 mm were TIG welded with welding wires of W22 9 3 NL (2209). The main aim was to investigate the effects of various amounts of magnetic δ-ferrite and other important phases or intermetallic compounds that are formed during and after welding. The phase quantities differing by the welding conditions and argon shielding gas mixtures containing 0, 1, 3, 6, and 9 vol.-% N2 are studied. The investigations included Charpy V-notch impact tests, weight loss corrosion tests, and microstructural analyses according to ASTM A 923 and magnetic δ-ferrite measurements according to EN ISO 17655, and EN ISO 8249 as well as image analyses according to ASTM E-562, ASTM E 1245 for a comparision of the effect of the amounts of all phases. The differences with respect to the welding parameters were also identified.

Influence of Aging Time on the Tensile Strenght of a Duplex Stainless Steel

This article was aimed at studying the influence of different aging times during the precipitation phase of the UNS S31803 (SAF 2205) duplex steel. To do so, all the test specimens were solution heat treated at 1050oC for 1 hour and quenched in water. After this step, the samples were aged at 850°C for periods of 10, 60 and 600 minutes and cooled in water. The aging heat treatments (TT) were performed in order to precipitate the sigma phase. Samples were subjected to microhardness and tensile tests so that the influence of the microstructural changes over the mechanical properties of the steel was assessed. Based on the microhardness and tensile test data, it was possible to verify a significant change over the mechanical properties of the UNS S31803 steel.

Experimental Investigation on Friction Welding of UNS S32205 Duplex Stainless Steel

UNS S 32205 duplex stainless steel specimens were joined by continuous drive friction welding process. The experiments were conducted as per the Taguchi (L16 orthogonal array) method. The friction welding process parameters such as heating pressure, heating time, upsetting pressure, upsetting time, and speed of rotation were fixed with low, medium, and high levels of range based on the machine capacity, and the required knowledge was acquired from the preliminary experiments. The joint characterization studies included micro structural examination and evaluation of mechanical properties of the joints. Microhardness variation, impact toughness, and tensile strength of the joints were evaluated. Neither a crack nor an incomplete bonding zone was observed. The tensile strength of the joints was higher than the strength of the base material, and the friction and upsetting pressures were found to influence the joint strength. The tensile strength of all the welds was observed to be increasing with an increase in the rotational speed. The toughness of the friction welds was evaluated at room temperature and also at subzero (cryo) temperature conditions. The toughness for friction welds was found to be superior to the fusion welds of duplex stainless steel at room temperature and cryo conditions. Weldments exhibited better corrosion resistance than the parent material.

Optimization of process parameters of the activated tungsten inert gas welding for aspect ratio of UNS S32205 duplex stainless steel welds

The activated TIG (ATIG) welding process mainly focuses on increasing the depth of penetration and the reduction in the width of weld bead has not been paid much attention. The shape of a weld in terms of its width-to-depth ratio known as aspect ratio has a marked influence on its solidification cracking tendency. The major influencing ATIG welding parameters, such as electrode gap, travel speed, current and voltage, that aid in controlling the aspect ratio of DSS joints, must be optimized to obtain desirable aspect ratio for DSS joints. Hence in this study, the above parameters of ATIG welding for aspect ratio of ASTM/UNS S32205 DSS welds are optimized by using Taguchi orthogonal array (OA) experimental design and other statistical tools such as Analysis of Variance (ANOVA) and Pooled ANOVA techniques. The optimum process parameters are found to be 1 mm electrode gap, 130 mm/min travel speed, 140 A current and 12 V voltage. The aspect ratio and the ferrite content for the DSS joints fabricated using the optimized ATIG parameters are found to be well within the acceptable range and there is no macroscopically evident solidification cracking.

On the Depassivation Mechanism of Lean Duplex Stainless Steels and the Influence of the Partitioning of the Alloying Elements

The depassivation of UNS S32304, S32202, and S32101 lean duplex stainless steels (DSS) in 26 wt% sodium chloride (NaCl) was investigated by potentiodynamic polarization to understand the selective dissolution processes in localized corrosion phenomena. Results showed that the depassivation of the three grades proceeds in two stages. First, the austenite is the only phase depassivated within the range of no more than 0.3 pH units, providing a single corrosion peak on the polarization curves of the DSS. Subsequently, the ferrite is also depassivated and provides a second corrosion peak at a more cathodic potential. Results are discussed in terms of the partitioning of alloying elements.

Differential Evolution algorithm applied to FSW model calibration

Friction Stir Welding (FSW) is a solid state welding process that can be modelled using a Computational Fluid Dynamics (CFD) approach. These models use adjustable parameters to control the heat transfer and the heat input to the weld. These parameters are used to calibrate the model and they are generally determined using the conventional trial and error approach. Since this method is not very efficient, we used the Differential Evolution (DE) algorithm to successfully determine these parameters. In order to improve the success rate and to reduce the computational cost of the method, this work studied different characteristics of the DE algorithm, such as the evolution strategy, the objective function, the mutation scaling factor and the crossover rate. The DE algorithm was tested using a friction stir weld performed on a UNS S32205 Duplex Stainless Steel.