Dissimilar welding of duplex stainless steel with Ni alloys: A review

In this article, the mechanical properties and microstructure of 304L austenitic stainless steel/Incoloy 800HT nickel alloy dissimilar welded joints are investigated. The joints were made of 21.3 mm × 7.47 mm tubes using the TIG process with the use of S Ni 6082 nickel filler metal. No welding imperfections were found and high strength properties of joints were obtained, meeting the assumed acceptance criteria of the product’s standards. The tensile strength of the welded joints was higher than for the joined materials (Incoloy 800HT). Macro- and microscopic metallographic tests revealed the correct morphology of the joints and the appropriate structures in their critical zones. However, differences were found in the morphologies of the zones between the weld and the base materials. In fusion boundary from the side of the Incoloy 800HT alloy, no clear outline of the fusion line was observed (type A fusion boundary), while increased grain size and an epitaxial structure were observed. In turn, in the zone: weld–304L steel, a distinct fusion line was observed with areas with an increased amount of high-temperature δ ferrite (type B fusion boundary). No precipitates were found that could reduce the resistance of the joints to intergranular corrosion. A hardness decrease (approximately 30 HV0.1) in the transition zone: austenitic steel–weld and an increase of hardness (approximately 10 HV0.1) on the opposite side of the welded joint were observed.

Mechanical and Microstructural Characterization of TIG Welded Dissimilar Joints between 304L Austenitic Stainless Steel and Incoloy 800HT Nickel Alloy

Prediction of impact toughness based on the microstructural characteristics of steel weld metals is complicated due to the innumerous parameters involved. The common practice that associates this property with the microstructure of the last bead of multipass weldments has been proven to be unsatisfactory, because the amount of acicular ferrite, the most desirable constituent, may not always be the main contributor to toughness. Parameters such as the recrystallized fraction, the presence of micro-phases and inclusions may also have a relevant role. Thus, to consider the influence of all these parameters, the method proposed by the International Institute of Welding (IIW) is not sufficiently comprehensive and so complementary techniques are necessary. This situation is more relevant for high strength steel weld metals, where very refined microstructures may not be adequately resolved, resulting in misidentification of the microstructure. The use of scanning electron microscopy as an auxiliary technique to optical microscopy has been successfully used for many decades to study C–Mn and low alloy weld metals, mainly when refined microstructures are to be assessed. Recently, in addition to the previously mentioned techniques, Electron Back Scattering Diffraction (EBSD) has also been used to enable a more effective analytical procedure. This technique, which provides valuable information about grain boundaries, is advantageous for refined microstructures to confirm constituents such as acicular ferrite, bainite, and martensite. This work proposes a contribution to the microstructural characterization of C–Mn and high strength steel weld metals based on the analysis carried out by optical microscopy, scanning electron microscopy and EBSD techniques, involving the influence of recrystallization in multipass welds, microstructural constituents, microphases, and inclusions. The microstructure/toughness relationship analysis of some experimental results obtained over the last decades for weld metals with ultimate tensile strength varying from 400 to 1000 MPa was done using the methodology proposed in this work to check its effectiveness and to explain the impact toughness behavior.

Microstructure characterization and its relationship with impact toughness of C–Mn and high strength low alloy steel weld metals – a review

Prediction of welding deformation in stiffened structure by introducing thermo-mechanical interface element

Wire arc additive manufacturing (WAAM) with better material utilisation efficiency and higher deposition rate was employed to fabricate bi-metallic structure (BMS) of non-stabilised austenitic stai...

Microstructure and mechanical properties of wire arc additive manufactured bi-metallic structure

Inconel 625 nickel alloy and UNS S32205 duplex stainless steel (DSS) were welded with ER2209 filler metal using MIG (Metal Inert Gas) welding method. The weld metal obtained by DSS filler metal was subjected to mechanical and microstructural evaluation. Toughness and hardness properties had been examined by mechanical and microstructural characterization of weld metal, fusion line, and HAZ (Heat Affected Zone) region, and precipitations were investigated by light microscopy (LM), scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS). Corrosion behavior of base metals and face and root of weld metal were examined by using potentiodynamic polarization test. Additionally, detailed elemental analysis and mapping of weld metal with both optical emission spectrometer (OES) and X-Ray spectrometer were attained. Results demonstrate a significant decrease in toughness of the welding due to the presence of Nb and Mo rich intermetallic precipitations in the Inconel HAZ and root region, although there is no significant increase in hardness. Potentiodynamic polarization test shows that the dilution-induced microstructural transformation in the root of weld has the worst corrosion resistance in the weld metal. Therefore, this dissimilar welding does not have optimum properties for neither toughness nor corrosion.

Evaluation of microstructural and mechanical properties of dissimilar Inconel 625 nickel alloy–UNS S32205 duplex stainless steel weldment using MIG welding

In this study, nickel-based alloy 625 and duplex stainless steel (DSS) UNS S32205 (2205) dissimilar pairs were welded with metal inert gas (MIG) welding process. Weld metal, obtained with the utilization of ERNiCrMo-3 filler wire, was subjected to mechanical, microstructural, and corrosion investigations. V-notch impact tests and micro hardness measurements were realized on dissimilar weld metal. Microstructural changes in weld metal, fusion line, and heat-affected zone were examined using optical, scanning (SEM), and transmission electron microscopes (TEM) with energy-dispersive spectrometry (EDS). Phase precipitations rich of Nb and Mo were detected among dendritic austenite arms in the weld metal. It was observed that ERNiCrMo-3 filler metal had sufficient toughness because of high nickel content. Corrosion tests revealed that weld metal face pass is the least corrosion-resistant zone in weld metal unlike weld root. This is mainly because more intense intermetallics formed in weld metal face compared with the middle of the weld and the root.

Investigation of microstructure, mechanical, and corrosion behavior of nickel-based alloy 625/duplex stainless steel UNS S32205 dissimilar weldments using ERNiCrMo-3 filler metal

In this article, the effect of gas metal arc welding (GMAW), pulsed gas metal arc welding (GMAW-P), and cold metal transfer (CMT) welding processes on angular distortion is investigated along with strain relaxation by removing weld deposits. Moreover, in order to investigate the behavior of the joint in terms of angular distortion, stress stretching (i.e., pressure model) is applied on welds via finite element analysis simulation to compensate weld shrinkage. In addition, a conceptual welding procedure using two different welding processes (i.e., deep-heat model) for filling the joint and strain relaxation of the weld, respectively, is investigated by a modeling approach. The joint type studied in all cases is a double-fillet welded Tee-joint.

Strain-Based Assessment and Modeling for Low-Distortion Welding Procedure

High strength low alloy (HSLA) steels are quite crucial in weight reduction in manufacturing of vehicles and constructions with high steel thickness. Quenched and tempered S690QL HSLA stee...

Investigations on Mechanical Strength and Microstructure of Multi-Pass Welded S690QL HSLA Steel Using MAG and FCAW

Shipbuilding industry grows rapidly due to the increasing growth of economies and thus, the need for new and bigger ships emerge. Manufacturing of ships in shipyards includes harmful processes, such as welding, which impact the workers and the environment. As a consequence of increase in demand for new ships, deleterious welding fume and emissions all over the world increase year by year. Welding fume includes hazardous micro and sub-micro sized metal particulates and in addition to welding fume, welding emissions consist of detrimental gaseous wastes as well. In this study, a set of experiments was designed by Taguchi method. These experiments were realized by two welders using two different types of covered electrodes (rutile and cellulosic), welding speeds and currents on Grade A shipbuilding steel, which is one of the most common steels in shipbuilding. After the experiments, fume formation rate was measured and it was observed that the contributions of the factors are 92.47%, 5.42% and 1.66% for electrode type, current and welder, respectively. The results were assessed using Taguchi and ANOVA and evaluated in terms of environment and occupational health and safety.

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Tolga Mert

Papers

Evaluation of microstructural and mechanical properties of dissimilar Inconel 625 nickel alloy–UNS S32205 duplex stainless steel weldment using MIG welding

Investigation of microstructure, mechanical, and corrosion behavior of nickel-based alloy 625/duplex stainless steel UNS S32205 dissimilar weldments using ERNiCrMo-3 filler metal

Strain-Based Assessment and Modeling for Low-Distortion Welding Procedure

Investigations on Mechanical Strength and Microstructure of Multi-Pass Welded S690QL HSLA Steel Using MAG and FCAW

Fume Formation Rate Analysis of Shipbuilding Steel with SMAW Using Taguchi Design and ANOVA