Dissimilar Metal Welds Research Articles

Microstructure, Hardness, and Residual Stress of the Dissimilar Metal Weldments of SA508-309L/308L-304L

A dissimilar metal weldment consisting of SA508-309L-308L-304L is widely used in light-water nuclear reactors. These weldments demonstrate dissimilar susceptibility to stress corrosion cracking that are related to the microstructure, properties, and residual stress. In this work, microstructures, hardness, and the residual stress distribution of the dissimilar metal weldments were investigated, with the correlation of increased hardness in the heat-affected zone (HAZ) to the microstructure. 304L HAZ demonstrated similar grain morphology as the base material, and the increase in hardness was primarily attributed to the increased dislocation density. SA508 HAZ demonstrated a change of grain morphology resulting from the different peak temperatures and cooling rates. The increased hardness in the SA508 HAZ was attributed to the refined grain morphology, higher dislocation density, and higher number density of precipitates. A ~ 20–30-μm-wide martensitic zone formed at the fusion boundary of SA508-309L, where Cr-rich carbide precipitates were observed, with the average size and the number density of 44.1 ± 16.9 nm and 1.5 × 1021 m−3, respectively. Residual stress results demonstrated the largest tensile stress at 309L butter, indicating its high cracking susceptibility.

Effect of impurities in dissimilar metal welds on their corrosion behavior

AbstractDissimilar metal welds are commonly used constructional solutions in most light‐water reactors. Unfortunately, it may also be a source of operational problems due to the combination of two or more metals with different corrosion resistance. For welds of carbon and austenitic steel, it is possible to observe damage in the austenitic steel, which is the material with better corrosion resistance. This self‐contradictory phenomenon is presumed to be caused by the segregation of impurities (S, P, C) from carbon steel on austenitic grain boundaries. The goal of this study is to demonstrate the effect of these impurities on the corrosion behavior of Fe–Cr–Ni alloys with different Cr and Ni content by using electrochemical methods.

Modeling of Laser Welds Using Machine Learning Algorithm Part I: Penetration Depth for Laser Overlap Al/Cu Dissimilar Metal Welds

Modeling of Laser Welds Using Machine Learning Algorithm Part I: Penetration Depth for Laser Overlap Al/Cu Dissimilar Metal Welds

WITHDRAWN: Challenges and possibilites in the resistance spot welding of dissimilar metals – A review

In order to get a defect free spot weld, both the metals are desired to have the same thermal and electrical conductivity. But when welding dissimilar metals or sheets of different thickness, the fusion zone of both the metals may not experience same heat input due to the difference in material properties. This leads to weld defects such as nugget offset, voids and intergranular cracks in the fusion zone. The existence of weld defects deteriorates the mechanical performance of welded joints. A thorough metallurgical analysis must be carried out to ensure that the weld nugget is free of defects. The resistance spot welding of various dissimilar metals in the recent research publications and its practical outcomes are analyzed.

Modified microstructures in proton irradiated dual phase 308L weldment filler material

The effect of proton irradiation on the microstructure of δ ferrite—γ austenite mixed phase 308L filler material in a 508–304 dissimilar metal weldment was investigated over a depth of 0 to 10 µm. Ni–Si–Mn G-phase precipitates were observed with SEM and TEM in δ ferrite but not in γ austenite. Our density functional theory based calculations show that the G/Fe interface energy in δ-Fe is significantly lower than that in γ-Fe (0.35 versus 1.25 J/m2), which provides a thermodynamics-based explanation for our experimental observations of preferential formation of G-phase in δ ferrite. STEM-EDS, TEM dark field imaging, and diffraction patterns confirmed the Ni–Si–Mn enriched precipitates were G-phase precipitates with a stoichiometry of Mn6Ni16Si7. Intragranular voids and Ni–Si enriched clusters were observed in irradiated γ austenite. Additionally, Ni and Si segregation was observed along the void interfaces. In both cases, Ni–Si clusters and segregation to voids, selected area diffraction patterns did not reveal the existence of a second phase. Proton irradiation induced Cr depletion and Si and Ni enrichment at γ−γ austenite grain boundaries that was characterized with STEM/EDS.

Microstructure and Mechanical Properties of 10CrNi3MoV Steel-SS304L Composite Bimetallic Plates Butt Joint by Shielded Metal Arc Welding

In the present study, composite bimetallic plates of 10CrNi3MoV steel—304L stainless steel were butt welded by shielded metal arc welding (SMAW). A transition layer was designed to compensate for the dilution of Cr and Ni in stainless steel layer during the welding of dissimilar metals. From the results, it was seen that the lowest hardness of fusion weld was located in transition layer, followed by 304L stainless steel side, and the highest hardness occurred at 10CrNi3MoV steel area. The minimum hardness was related to high Cr and Ni in transition layer welded by E309L welding rod, and a uniform dendritic austenite structure was formed in the fusion weld. The formation of high-hardness carbides and vanadium-containing phases enhanced the hardness of the fusion weld. Butt welded joints had excellent tensile strength and toughness. The maximum tensile strength of the joint was about 694 MPa, and the tensile specimens fractured in ductile at matrix of the bimetallic plates. The impact energy of the weld joint was about 98 J at − 20 °C. When the number of loading cycles was set to 2 × 106 times, the maximum load limit of the bimetallic plate welded joint in 10CrNi3MoV steel was between 600 MPa and 625 MPa.

Microstructural characterization of low alloy steel A508 – 309/308L stainless steel dissimilar weld metals

In this study, the microstructure and microhardness of low alloy steel A508 welded with 309/308L stainless steel are investigated. The microstructure evaluations show that the heat affected zone of the A508 base metal changes, from tempered bainite to an uneven mixture of bainite and martensite, depending on the intensity of the heat flow from the welding process. Different recrystallization processes at the heat affected zone of the base metal are responsible for the changes of the microstructure, which lead to differences in the grain sizes, strain level, and yield strength in this region. The greatest deformation level is observed in the grain refined region with the highest heat influx, which leads to a high level of grain refinement and stress in this region, followed by the partial grain refined region and base metal matrix region, respectively. The interface region between the base metal and weld metal is observed to be very complex. At some regions of the 309/308L, adjacent to the fusion boundary type II boundaries, resulting from the allotropic δ – γ transformation and migration of steel phases/boundary at high temperature of welding were observed, alongside the type I boundaries. The 309/308L stainless steel consists of vermicular ferrite distributed along the austenite matrix, while ternary sigma secondary phase was observed to precipitate at the interface of the ferrite/austenite boundary. The yield strength of the grain refined region, partial grain refined region, and base metal matrix in A508 were estimated to be 598 MPa, 600 MPa, and 595 MPa, respectively. Finally, the heat affected zone of the base metal showed the highest hardness followed by the base metal matrix and weld metal, respectively.

Ultrasonic high frequency guided waves for testing of dissimilar metal welds

Abstract Ultrasonic testing of nickel-based dissimilar metal welds (DMWs) in nuclear power plants is always challenging due to its internal structures. Indeed, ultrasonic bulk waves can be severely scattered and attenuated because of coarse grains in DMWs and consequent difficulties such as splitting and skewing can be observed due to the anisotropic and inhomogeneous structure of the weld pool. Ultrasonic high frequency guided waves (HFGW) has the potential to reduce and overcome these issues and can offer a good compromise between the volume coverage and defect sensitivity for testing of DMWs. This work presents defect detection in DMW joints made by 12 mm thickness P91 and alloy 800 plates using HFGW. The generation and propagation characteristics of HFGW on both P91 and alloy 800 have been extensively studied by using 2D plane strain finite element modelling (FEM). For both experimental measurements and FEM, the input parameters such as the excitation frequency, incident angle and scan distance have been optimized with the help of Dispersion curves. It has been observed that the amplitude response of HFGW is more than two times on the P91 plate when compared to the alloy 800 plate. The interaction of HFGW with artificial defects made on the DMW and at the weld interfaces have been tested. It has been noticed that the HFGW can able to detect defect size down to ~ 10% of 12 mm wall thickness and 2 mm diameter side-drilled holes reliably from both sides of P91 and alloy 800.

Dissimilar Metal Welds used in AUSC Power Plant, Fabrication and Structural Integrity Issues

ABSTRACTIn the current era, the Advanced Ultra Super-Critical (AUSC) plants have been used to substantially increased efficiency with environmental protection. AUSC components boiler header, re-heater and super-heater tube etc. are fabricated by using advanced materials to join by the welding process. Any failure of the power plant can lead to grave consequences, not only of substantial financial losses but additionally immensely treasured and irreparable human life loss. In this review, the dissimilar metal welds (DMWs) have many issues such as metallurgical issue, cracking, carbon migration, welding electrode selection, creep properties, suitable welding process and structure integrity issues which enhanced the failure of weldments. The results of our review showed that DMWs of AUSC power plant are joined by activated flux Tungsten Inert Gas (A-TIG) and Pulse A-TIG process to increase the productivity and cut the significant fraction of cost. However, A-TIG process with Post Weld Heat Treatment (PWHT) improved the mechanical properties and high-temperature creep resistance properties of DMWs. This state of the art is encouraged the researchers about the enormous future scope.

Joining of dissimilar metals using microwave hybrid heating and Tungsten Inert Gas welding - A review

In the new era of the Industrial Revolution, a new method is established in the welding of similar/dissimilar metals. Welding of dissimilar metals still possesses a significant challenge because of their incompatible material properties and structure. Using new materials in automobiles, aerospace has made dissimilar metal welding a very essential part of industrial application. Microwave Hybrid Heating (MHH) is a technique that has acquired a lot of attention in the recent years because of its precise and controlled heating and it can help in selective heating of materials. This process can join many materials and is also cost-effective and environment friendly. This paper reviews the successful joining of dissimilar metals through two non-conventional welding techniques namely Microwave hybrid heating and Tungsten Inert Gas welding but mainly focusing on the recent Microwave hybrid heating process with regards to the materials, susceptor medium, exposure time and the various techniques used for characterization of the joints. It can be concluded from the findings that limited study has been carried out in the field of dissimilar welding of metals through the above processes, especially microwave through microwave hybrid heating and there is scope for improvement and research.

Evaluation and Analysis of RT Suspected Defects on Reactor Pressure Boundary Weld

The control rod driving mechanism (CRDM) is one of the important equipments in the nuclear reactor, and its sealing shell is part of the pressure boundary of the nuclear reactor. The sealing shell is a pressure vessel made of two different material (austenitic stainless steel and nickel base alloy) cylinders welded by dissimilar metal welds. Product production process, in this dissimilar metal weld ray detection found suspected defects show. In this paper, the mechanism and process of the suspected defects are expounded through experimental verification, and it is proved that the suspected defects do not affect the quality of the weld.

Spajanje raznorodnih metala ultrazvučnim zavarivanjem

The dissimilar metal welding always challenges. The different alloys have different physical and mechanical properties. In the case of the electronic component of the car, it needs to establish a joint between dissimilar metals. The useful metals are for this application are copper and aluminium. Even that has good conductivity, corrosion resistance and formability. By fusion welding technologies these thin metal workpiece joining is not a simple technology. To use a solid state welding technology can be a suitable solution to establish a cohesion joint in case of this task. It well-known much suitable technologies, even that all of them has advantages and disadvantages. The choice of solid-state technology is the ultrasonic welding process. In the case of this process, we use pressure and high-frequency vibration for welding. Besides this process, the friction and vibration generated heat is lower than the metal melting temperature. The base of this technology is the ultrasound-assisted high-level formability. The optimization of this dissimilar joining technology parameters needs many pre-welding and testing process. In this work, we wanted to introduce this empirical optimization process.

Finite element analysis of lap joint based on various geometrical parameters to study the behavior of weld strength

This paper reports on study of lap joint weld shear strength of resistance spot weld. Resistance Spot Welding (RSW) is a very cost effective joining technology in automobile industry used to join sheets or plates. The research papers present the effect of various parameters like welding time, welding current, electrode force and squeeze time on strength of joint formed by spot welding of similar and dissimilar metals and thicknesses. Optimization of these parameters is obtained by the micro-hardness test, tensile shear test and fatigue test and the papers presented the methodologies to increase the fatigue life of the joint. In this paper MSC Nastran software is used to analyze the strength of the joint formed by the resistance spot welding. Steel Plates or sheets are modeled with Shell elements of type CQUAD4 and weld element between two plates (Nuggets) are modeled with 1D element with CBAR elements. Various FE models are generated with the consideration of geometrical parameters like thickness of the plate, nuggets along the span length and edge distance. FE models will be subjected to constant pre-defined loads on the various FE models and the weld shear strength were captured for each model and compared against the other models to study the weld behavior. Outcome of the present study provides the insight towards the selection of the optimized weld spots (nuggets) distribution for the various thicknesses of the plate, location of the nuggets along the length and the selection of optimum edge distance. The present study is used to compare the stresses induced in the plates and nuggets for the given load.

Research contribution and potential investigation on friction stir welding for AA2014 material family

Abstract Aluminum alloy 2014 has wide application. In its applications, aerospace and automobile industries are utilized well such Aluminum alloy. This article presents a novel approach of reviewing material related research to pave the path for new researchers. The aluminum is one of the popular materials and can be modified either to form a composite or augmenting the material properties with utilization of heat treatment methods. Friction stir welding is one of the advanced metals joining/ welding technology. This paper reviews how the two popular cases jointly contributing for creating mechanical structures. This papers covers parameter optimizations for friction stir welding of similar and dissimilar metals, mathematical modeling, post welding treatments, new tool contributions, grain structure effects, need for FSW and identified further research scope further research are consolidated and presented as research potential.

Effect of welding electrode variation on dissimilar metal weld of 316l stainless steel and steel ST41

The propeller shaft is part of the ship which transmitting rotation from engine to propeller. The shaft is also used in small-medium size of fisherman boat. In order to reduce the cost of production, dissimilar metal bases are used by joining Steel ST41 and 316L Stainless Steel in process. This research was conducted to analyze effect of welding electrode towards tensile strength, macrostructure, and microstructure of Steel ST41 and 316L Stainless Steel welded metal. Two variations of electrode that used in this paper were E309-L and E6013 with Shielded Metal Arc Welding process (SMAW). The other parameter such as current was set at 80 A and voltage was set at 20 V with 20 mm/min welding travel speed. The results of tensile test show average tensile strength max (σmax) of E309-L and E6013 electrode were 581,42 MPa and 599,24 MPa respectively. These results show that welding process is increasing the maximum tensile strength from base material strength level. The microstructure test interpretation shows E309-L electrode has lower possibility to create delta ferrite in HAZ (Heat Affected Zone) rather than E6013 electrode. This means welding process with E6013 tends to have lower corrosion resistance.

Characteristic analysis of dissimilar metal weld for AISI304 with SA213T22 in super heater coils

Super heater is an inevitable component of any boiler system and failure of super heater leads to breakdown of whole plant. The integration of efficient quality welding technologies for dissimilar metals will be a key component in the successful weld quality for power plant components. In this investigation, an attempt has been made to study the dissimilar material AISI304 and SA213T22 tungsten inert gas welding is performed under different welding conditions current (100, 115, 130 Amps), gas flow rate (6, 8, 10 ltr/min), speed (2, 2.5, 3 mm/sec) and micro structure analysis performed to find influence of fusion heat. The Taguchi analysis is implemented to obtain single response optimization and grey relational analysis used to attain multi response for best yield strength, the ultimate strength, Vickers hardness and the elongation of the metals.

Additive manufacturing of Inconel625-HSLA Steel functionally graded material by wire arc additive manufacturing

Functional graded materials (FGMs) have been widely applied in many engineering fields, and are very potential to be the substitutions of dissimilar metal welding joints due to their overall performance. In this work, the Inconel625-high-strength low-alloy (HSLA) Steel FGM was fabricated by wire arc additive manufacturing (WAAM). The chemical composition distribution, microstructure, phase evolution and mechanical properties of the FGM were examined. With the increasing of HSLA Steel, the chemical composition appeared graded distribution, and the primary dendrite spacing was largest in graded region with 20%HSLA Steel and then gradually decreased. And the main microstructure of the FGM transformed from columnar dendrites to equiaxed dendrites. Laves phase precipitated along dendrites boundary when the content of HSLA Steel was lower than 70% and Nb-rich carbides precipitated when the content of HSLA Steel exceeded to 70%. Microhardness and tensile strength gradually decreased with ascending content of HSLA Steel, and had a drastic improvement (159HV to 228HV and 355Mpa to 733Mpa) when proportion of HSLA Steel increased from 70% to 80%.

Review on welding and fracture of nickel based superalloys

Nickel-based super alloys comprise of up to ten alloying elements inclusive of both heavy refractive and lightweight elements. These super alloys find application in corrosive or oxidizing environment, high temperature, and stresses. They possess high fracture toughness, tensile and yield strength. There is a demand for high quality welded joints of Nickel-based super alloys in gas turbines of power generation and aerospace. Manufacturers around the world are trying to enhance the properties with befitting process parameters and approaches. In this paper, chemical compositions, microstructures, welding and fracture studies of nickel-based super alloys with special reference to Inconel 718 was reviewed. Dissimilar metal welding of Inconel 718 to other alloys were also reviewed.

Investigation on solidification and phase transformation of heterogenous interface structure in dissimilar metal weld between high Cr heat-resistant steel and nickel-based alloy 617

The present study characterized heterogenous interface structure in dissimilar metal weld between a high Cr martensitic heat-resistant steel and nickel-based alloy weld metal (WM), and revealed its solidification and phase transformation processes during welding. The heterogenous interface structure consists of a martensitic peninsula structure and a partially mixed zone (PMZ) of austenitic stainless steel. The K–S relationship between peninsula structure and its surroundings indicates: 1. phase transformation of (δ-Fe) to (γ-Fe) of peninsula occurs only after previous austenitic PMZ has solidified; 2. the subsequent WM solidifies epitaxially on (γ-Fe) of peninsula. Due to that the liquidus temperature of PMZ is lower than that of base metal (BM), the peninsula structure can form in the early stage of solidification by quick freezing of liquid BM.

Finite element analyses of the effect of weld overlay sizing on residual stresses of the dissimilar metal weld in PWRs

Dissimilar metal welds are commonly used in various types of reactors to connect low alloy steel nozzles and austenitic stainless steel piping systems. To mitigate the degradation of stainless steel pipe welds that are affected by intergranular stress corrosion cracking in BWRs, weld overlays have been implemented to provide the structural reinforcement. They have also been applied to repair dissimilar metal welds at nozzles in BWRs and PWRs. A weld overlay can favorable reverse residual stresses from tensile to compressive around interior of the susceptible materials. The ASME Code Case N-504 series suggest that the evaluation of repaired welds should consider residual stresses that are generated by the weld overlay with other applied loads on the system. This study considers a dissimilar metal weld that joins the low alloy steel nozzle to the stainless steel safe end in a typical PWR, and is to calculate the post-overlay residual stress states using ANSYS finite element analysis software. Based on the stress report and site survey of the hot leg nozzle, models for analyzing residual stresses were developed on various assumptions. Computational results demonstrate that the weld overlay process probably provides compressive distributions of axial and hoop residual stresses at the inside surface of the dissimilar metal weld. The residual stress distributions that are induced by weld overlays of various sizes are compared to determine the effect of weld overlay sizing on the residual stresses in the original weld. The comparison reveals that weld overlay length has a greater effect on residual stresses than weld overlay thickness. As the applied overlay length increases, the compressive residual stresses increase markedly. Each nozzle/safe end design is somewhat unique; using a feasible weld overlay dimension in consideration of technical and economic is necessary. This investigation has provided a reference for optimizing the weld overlay design of dissimilar metal welds in PWRs.