Duplex Stainless Steel Welds Research Articles

A Review on Microstructure Development and Mechanical Properties of Fusion Welded Duplex Stainless Steels

A Review on Microstructure Development and Mechanical Properties of Fusion Welded Duplex Stainless Steels

Effect of Filler Metal on the Performance of 2205 Duplex Stainless Steel Weldments

Effect of Filler Metal on the Performance of 2205 Duplex Stainless Steel Weldments

Fracture morphology of GTAW welding of dissimilar duplex stainless steels exposed to H2S corrosion

Fracture morphology of GTAW welding of dissimilar duplex stainless steels exposed to H2S corrosion

Investigations on high-power laser beam-submerged arc hybrid welding of thick duplex stainless steel using laser beam wobbling

Duplex stainless steels are used in many application fields due to their outstanding performance with respect to strength, toughness, and corrosion resistance. These properties are based on a microstructure proportion of at least a proportion of 30% austenite. To meet the requirements of the microstructure and a high productivity, a high-power and precise heat controlled welding procedure like laser beam-submerged arc hybrid welding is necessary. In this study, laser beam-submerged hybrid welding processes are developed for butt joints of duplex stainless steel S31803 (t = 16 mm) using a disk laser beam source with a maximum output laser beam power of PL = 16 kW. The aims of these developments are to achieve stable, efficient one-layer welding processes for joining weld seams with high quality regarding the microstructure. Therefore, the welding parameters, laser beam power, welding speed, and wobble amplitude are investigated using visual inspections and metallographic analyses. To increase the microstructure proportion of austenite, the laser beam is wobbled linear and transversal to the welding direction using amplitudes up to 5 mm. As results of welding process developments, stable and efficient one-layer hybrid welding processes were archived at a high welding speed of vW = 1.0 m/min and a wobble amplitude of WA = 2.5 mm. The weld seams meet the requirement of at least a proportion of 30% austenite. Without using laser beam wobbling, the weld seam does not achieve the austenite proportion required at this welding speed.

Role of Ni-Rich Solute Clusters in the Age Hardening Performance of Ferrite in 22% Cr Duplex Stainless Steel Weld Metal

The nanoscale structure of ferrite in a 22% Cr duplex stainless steel weld metal (fabricated with grade 2209 filler wire) aged at 400 °C was characterized via scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy through the Super-XTM detector; the results were compared with those of a corresponding grade base metal (2205). The weld metal-ferrite exhibited a more pronounced spinodal decomposition than the base metal-ferrite because of its higher Ni content. Moreover, the presence of Ni-rich solute clusters with a body-centered-cubic structure was notably evident in the weld metal-ferrite. The investigation of the precipitation hardening mechanism using the Ardell model confirmed that, besides the extended spinodal decomposition, Ni-rich solute clusters significantly contributed to the improved age hardening performance of the weld metal-ferrite in the 22% Cr duplex stainless steel.

Reduction of the Backing Gas Sequence as a Facile Method to Improve Corrosion Resistance in Duplex Stainless Steel (DSS) Weldment

Duplex stainless steel (DSS) is an important material used for corrosion resistance in various harsh environment plants such as petrochemical, offshore subsea component, and other chemical industries. An approximately equal amount of austenite and ferrite (A/F) ratio grants good mechanical properties and rust protection on. The detrimental intermetallic phase frequently occurs due to an unbalanced A/F ratio caused by the welding’s thermal cycle. Backing gas is commonly applicable in the field combined Gas Tungsten Arc Welding (GTAW) process. However, the use of backing gas to complete a single weld from root to cap joint required huge additional costs for consumables. Maintaining the thermal cycle in the welding parameter and GTAW process with ER2209 filler metal for DSS below 10 mm thick can reduce the backing gas sequence. The research aims to efficiently substitute full backing gas consumption, which meets a desirable quality in terms of corrosion resistance. The effect of backing gas reduction was studied. All specimens were tested by visua Vickers microhardness, metallography, ferrite content measurement, and electrochemical corrosion test. The visual test shows no defects beyond the range of the ASME IX acceptance and criteria. The evaluation comes from the ferrite scope and electrochemical corrosion test. The backing gas on the root weld shows a balance A/F ratio of around 38% ferrite content accepted in various standards. The backing gas sequence on the root until filler-pass obtained 0.04 mm/year, which is the desirable corrosion resistance and met the requirement of ASTM A932.

Identification and quantification of martensite in ferritic-austenitic stainless steels and welds

This paper aims at the phase identification and quantification in transformation induced plasticity duplex stainless steel (TDSS) base and weld metal containing ferrite, austenite, and martensite. Light optical microscopy (LOM) and electron backscatter diffraction (EBSD) analysis were employed to analyze phases. Samples were either mechanically or electrolytically polished to study the effect of the preparation technique. Mechanical polishing produced up to 26% strain-induced martensite. Electrolytic polishing with 150 g citric acid, 300 g distilled water, 600 mL H3PO4, and 450 mL H2SO4 resulted in martensite free surfaces, providing high-quality samples for EBSD analysis. Martensite identification was challenging both with LOM, due to the similar etching response of ferrite and martensite, and with EBSD, due to the similar lattice structures of ferrite and martensite. An optimized Beraha color etching procedure was developed that etched martensite distinctively. A novel step-by-step EBSD methodology was also introduced considering grain size and orientation, which successfully identified and quantified martensite as well as ferrite and austenite in the studied TDSS. Although here applied to a TDSS, the presented EBSD methodology is general and can, in combination with knowledge of the metallurgy of the specific material and with suitable adaption, be applied to a multitude of multiphase materials. It is also general in the sense that it can be used for base material and weld metals as well as additive manufactured materials.

Mechanical Properties and Microstructural Characterization of Laser Welded S32520 Duplex Stainless Steel.

This paper investigates an experimental design of laser butt welding of S32520 duplex stainless steel, which has been passed out with the help of a pulsed Nd: YAG laser supply. The intention of the present research is to learn the impact of beam diameter, welding speed, and laser power on the superiority of the butt weld. The individuality of butt joints has been characterized in terms of tensile properties, fractography, and hardness. It was noticed that unbalanced particle orientations indirectly produce a comparatively fragile quality in the laser welded joint. The outcome of varying process parameters and interaction effect of process parameters on ultimate tensile strength and micro hardness were studied through analysis of experimental data. With different process parameters, the heat energy delivered to the material was changed, which was reflected in tensile strength measurement for different welded samples. From this present research, it was shown that, up to a certain level, an increase in process parameters amplified the tensile strength, but after that, certain level tensile strength decreased with the increase in process parameters. When process parameters exceeded that certain level, the required amount of heat energy was not delivered to the material, resulting in low bead width and less penetration, thus producing less strength in the welded joint. Less strength leads to more ductile weld joints. Microhardness was higher in the weld zone than in the base region of welded samples. However, the heat affected zone had a high microhardness range.

Effect of post-weld heat treatment on microstructure and corrosion properties of multi-layer super duplex stainless steel welds

Abstract To investigate the influence of post-weld heat treatment on the microstructure and corrosion properties of super duplex stainless steel welded joints, multi-layer multi-pass welding of 2507 super duplex stainless steel by tungsten argon arc welding was performed using an ER2594 welding wire. The microstructures of the welded joints before and after post-weld heat treatment at 1150 °C, 1170 °C and 1190 °C were observed, and the mechanical and corrosion properties were tested. The post-weld heat treatment changed the austenite content and morphology of the welded joint and improved the corrosion resistance of different parts of the weld metal. The choice of various solution heat treatment temperatures affected the change in austenite content in the weld zone and the degree of diffusion and homogenization of the alloy elements. After post-weld heat treatment at 1170 °C, the two-phase ratios in each area of the weld were the most suitable and uniform, and the overall mechanical and corrosion properties of the joint were more uniform.

Prediction of Mechanical Properties as a Function of Welding Variables in Robotic Gas Metal Arc Welding of Duplex Stainless Steels SAF 2205 Welds Through Artificial Neural Networks

Abstract Dual-phase duplex stainless steel (DSS) has shown outstanding strength. Joining DSS alloy is challenging due to the formation of embrittling precipitates and metallurgical changes during the welding process. Generally, the quality of a weld joint is strongly influenced by the welding conditions. Mathematical models were developed to achieve high-quality welds and predict the ideal bead geometry to achieve optimal mechanical properties. Artificial neural networks are computational models used to address complex nonlinear relationships between input and output variables. It is one of the powerful modeling techniques, based on a statistical approach, presently practiced in engineering for complex relationships that are difficult to explain with physical models. For this study robotic GMAW welding process manufactured the duplex stainless steel welds at different welding conditions. Two tensile specimens were manufactured from each welded plate, resulting in 14 tensile specimens. This research focuses on predicting the yield strength, tensile stress, elongation, and fracture location of duplex stainless steel SAF 2205 welds using back-propagation neural networks. The predicted values of tensile strength were later on compared with experimental values obtained through the tensile test. The results indicate <2% of error between observed and predicted values of mechanical properties when using the neural network model. In addition, it was observed that the tensile strength values of the welds were higher than the base metal and that this increased when increasing the arc current. The welds’ yield strength and elongation values are lower than the base metal by 6%, ~ 9.75%, respectively. The yield strength and elongation decrease might be due to microstructural changes when arc energy increases during the welding.

Mechanical Properties Study of a Duplex Stainless Steel Weld Using Physical Simulation and Work Hardening Models

Mechanical Properties Study of a Duplex Stainless Steel Weld Using Physical Simulation and Work Hardening Models

Investigation on Microstructure and Properties of Duplex Stainless Steel Welds by Underwater Laser Welding with Different Shielding Gas.

Taking S32101 duplex stainless steel as the research object, underwater laser wire filling welding technology was used for U-groove filling welding. The influence of different shielding gas compositions on the ferrite content, microstructure, mechanical properties and pitting corrosion resistance was studied by simulating a water depth of 15 m in the hyperbaric chamber. The results show that, under the same process parameters, the size and proportion of austenite in the weld when using pure nitrogen as the shielding gas are larger than those protected by other shielding gases. In a mixed shielding gas, the increase in nitrogen content has little effect on the strength and toughness of the weld. Regardless of the shielding gas used, the base metal was the weakest part of the weld. At the same time, intermetallic inclusions have an adverse effect on the impact toughness of the weld. The pitting corrosion resistance of the welds depends on the Cr2N content in the heat-affected zone. The precipitation and enrichment of Cr2N causes local chromium deficiency, which is the main factor for the weak pitting corrosion ability of the heat-affected zone. Pure nitrogen protection has a better corrosion resistance than other gas protection.

Fe and Cr phase separation in super and hyper duplex stainless steel plates and welds after very short aging times

Fe and Cr phase separation in ferrite, causing 475 °C-embrittlement, was studied after very short aging times in super duplex stainless steel (SDSS) and hyper duplex stainless steel (HDSS) plates and welds. Atom probe tomography showed that hot-rolled SDSS, experiencing significant metal working, had faster kinetics of phase separations compared to the SDSS and HDSS welds after 5 min aging at 475 °C. The surface of the 33-mm SDSS plate had faster Fe and Cr phase separation and larger toughness drop. A higher density of dislocations next to the austenite phase boundary in ferrite, detected by electron channeling contrast, can promote the phase separation at the surface of the plate with lower austenite spacing. The toughness dropped in HDSS welds after aging, but SDSS welds maintained their toughness. An inverse simulation method considering an initial sinusoidal nanometric Cr and Fe fluctuation showed that Ni increases the interdiffusion of Cr in the system, resulting a higher degree of phase separation in SDSS welds than the HDSS weld. Within the composition range of the studied SDSS and HDSS materials, the processing influences the Fe and Cr phase separation more than the variation in composition during short aging or typical fabrication times.

Ameliorative Corrosion Resistance and Microstructure Characterization of 2205 Duplex Stainless Steel by Regulating the Parameters of Pulsed Nd:YAG Laser Beam Welding

Welding parameters can greatly affect the final product. In this study, there was a variation given on the pulse energy, i.e., heat input parameters. The microstructure was analyzed and presented in relation to the efficiency of corrosion. The microstructural study showed the changes of the fusion zone (FZ) and the heat-affected zone (HAZ) with an increase in pulse energy. The development of a prominent austenite process on the weld material had a prolonged effect on its corrosion resistance property. Electrochemical impedance spectroscopy (EIS) and potentiodynamic measurements were used to test the electrochemical activity of laser-weld 2205 duplex stainless steel in an aqueous 3.5% NaCl solution. Finally, the findings of the EIS analysis were supported by Raman spectroscopy. Based on the obtained results, the 2205 duplex stainless steel (DSS) weld obtained at a higher pulse energy showed higher corrosion resistance than the welded sample obtained at a low pulse energy. The impedance spectroscopy confirmed a smooth surface property with an increase in the pulse energy and the presence of an oxide layer, a finding also confirmed by the Raman spectroscopy measurements.

Welding of Large Thickness Super Duplex Stainless Steel: Microstructure and Properties

In this study, Submerged Arc Welding (SAW) and Gas Metal Arc Welding (GMAW) processes were used in multi-pass welding of 33 mm thickness super duplex stainless steel plates. Recommended and higher than recommended arc energy and interpass temperatures were used. Both GMAW and SAW processes were able to produce large thickness weldments meeting the microstructural, mechanical, and corrosion resistance requirements, and also when using higher than recommended arc energy and interpass temperature. It was possible to reduce the number of welding passes by half when using higher than recommended arc energy and interpass temperature. The SAW process needed only half of the welding time required for the GMAW process to produce a weldment with nearly the same number of weld passes, when using recommended arc energy and interpass temperature. Based on the results of this investigation, the practical recommendations for welding large thicknesses should be revised and updated.

Comparison between PCA analysis and Grey based Taguchi analysis of TIG welding process parameters on Duplex stainless steel

Tungsten inert gas (TIG) welding on Duplex stainless steel (DSS) is more easy, comfortable and useful, if the process is precisely understood and controlled through development of the science & technology. TIG welding on DSS has been performed with the help of specific controlled welding process parameters. Welding quality has been strongly depended on these process parameters. In this study, some valuable welding parameters are chosen. These are welding current, shielding gas flow rate and speed of welding. These process parameters of TIG welding for ASTM/UNS 2205 DSS welds are optimized by using Principal Component Analysis (PCA) method and Grey based Taguchi’s L9 Orthogonal array (OA) experimental plan with the conception of signal to noise ratio (N/S). After that, compression results of above mentioned two analyses of TIG welding process parameters have been calculated. The quality of the TIG welding on DSS has been evaluated in term of ultimate tensile strength, yield strength and percentage of elongation. Compression results of both analyses indicate application feasibility for continuous improvement of welding quality on DSS in different components of chemical, oil and gas industries.

Characterization of inhomogeneous microstructure and mechanical property in an ultra-thick duplex stainless steel welding joint

Ultra-thick duplex stainless steel welding plates are widely used in various industries. However, one of the significant concerns is the inhomogeneous microstructure and mechanical properties along the thickness, which reduces welding efficiency and degrade service performance. In this study, a 55 mm thick duplex stainless steel welding joint with an X-type weld groove was prepared to study the variation of microstructure and mechanical properties along the through-thickness direction by both the miniature tensile specimen and cross-weld tensile specimen. The correlation between the microstructure and mechanical property was also studied. The results showed that the weld metal was characterized by abundant columnar grains with decreasing austenite content from surface to mid-thickness. Besides, the total fraction of low angle grain boundaries increased more than one-fold, while the total fraction of high angle grain boundaries decreased from 48.03% to 4.52% with increasing depth to the mid-thickness. Furthermore, substantial substructured grains and recrystallized grains were dominated in the weld metal and base metal. Along the thickness direction, the mechanical strength almost decreased and the elongation of welding joint increased with the increasing distance from the surface. Microhardness had a similar trend to that of strength, which all can be attributed to the variation of austenite content and grain boundary character distribution. Along the transverse direction, weld metal had the highest strength of 597.67 MPa, followed by the heat-affected zone of 549.42 MPa and base metal of 510.20 MPa, while the trend of elongation was opposite to that of strength. The microhardness distribution was not consistent with that of strength and had a maximum at the heat-affected zone.

Evolution of Microstructure and Texture in UNS S32750 Super Duplex Stainless Steel Weldments

Evolution of Microstructure and Texture in UNS S32750 Super Duplex Stainless Steel Weldments

Effect of welding conditions and flux compositions on the metallurgy of welded duplex stainless steel

This research tends to investigate the influence of shielded metal arc welding (SMAW) parameters and flux compositions on the metallurgy of welded AISI 2205 duplex stainless steel (DSS). The consumable was developed using the Al2O3-TiO2-SiO2 flux system as major flux ingredients. The spectrophotometer was used for determining the chemical composition of the base core wire and the base plate. The six different fluxes (F1, F2, F3, F4, F5 and F6, with varied compositions were coated on a 3.2 mm diameter of ER2209 core wire with a coating factor of 1.65 mm. Basicity indexes of the six formulated fluxes were calculated to be less than 0.9 for the developed electrodes, which confirmed the electrodes to be acidic coated electrodes. The influence of welding parameters, particularly current on the hardness characteristics of the weldment was established to ascertain the integrity and applicability of the developed consumable. It was evident that the average welding current of 120A at a constant voltage of 22.5 V produced high hardness properties of the welded joint of DSS with an optimal heat input of 1.65KJ/mm. The hardness properties in most sceneries were observed to be high at heat affected zone (HAZ) and fusion zone (FZ) than in the base metal (BM) region which is attributed to the ferrite content. The average hardness value of the BM was found to be 241Hv/20, for the FZ and HAZ using the produced electrode F5 and F6 were found to be 250HV/20 and 301HV/20 respectively and for F6 was found to be 259HV/20 at FZ and 336HV/20 at the HAZ while that of the commercial electrode (C) was found to be: FZ-245/HV/20 and HAZ-319/HV/20 which is a good indication of its conformity to standard DSS. The SEM-EDS morphological characterization also reveals the austenite-ferrite phase with relatively coarse grains, inter-critical grains and fine grains at the HAZ regions of the welded joint.

Microstructure, Mechanical and Corrosion Properties of UNS 32205 Duplex Stainless Steel Weldment Joints by Multipass FCAW

Abstract In this study, the effect of multipass welding on the microstructure, mechanical and corrosion properties of the UNS 32205 duplex stainless steels (DSS) is investigated. The UNS 32205 DSS is welded in 3 or 7 passes by flux-cored arc welding (FCAW) using E2209 T1 – 1/4 flux cored wire. The weldments are characterized by light optical microscopy (LOM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Feritscope analysis, Charpy impact tests and electrochemical corrosion tests. The results suggest that the multipass FCAW process induces the formation of γ2 in the weld seam. The mechanical and the corrosion properties of the weld joints are affected by the heat input variation and the phase transformations. Especially, the formation of the γ2 in the weld seam results in a decrease in the corrosion resistance of the joint samples.