Activated Tungsten Inert Gas Welding 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.

Penetration depth, phase balance and corrosion behaviour in activated TIG welding of UNS S32205

The aim of this research is to investigate the impact of a flux containing 80% TiO2 and 20% CeO2, under protective atmosphere (100% Ar, 98% Ar-2% N2, and 95% Ar + 5% N2) on penetration depth, phase equilibrium, and corrosion behaviour of autogenous A-TIG welds generated at constant current density. The reason for choosing cerium in the flux composition and nitrogen in the shielding gas is their effect on the phase balance of austenite and ferrite in this alloy. Metallography, ferritoscopy, and potentiometry were employed in the examination of the welds. The use of a two-component flux increased the penetration depth in TIG welding by up to 87%. Adding 2% and 5% nitrogen gas to the shielding gas in active TIG welding further increased the penetration depth to 117% and 130%, respectively. The results of ferritoscopic analysis reported the amount of austenite in the base metal and conventional TIG weld as 48% and 32%, respectively. However, the use of two-component flux increased the amount of austenite in the weld metal to 39%. Additionally, the addition of 2% and 5% nitrogen to the shielding gas in active TIG welding increased the amount of austenite in the weld metals to 60% and 76.6%, respectively. According to cyclic potentiodynamic polarization studies, active TIG welding with different nitrogen gas concentrations showed improved general and pitting corrosion properties in weld metals compared to conventional TIG welding. Consequently, weld metal resulting from active TIG welding with 2% nitrogen gas exhibited corrosion properties almost identical to that of the base metal.

STUDY ON THE IMPACT OF POST WELD HEAT TREATMENT ON TIG AND A-TIG INCONEL 617 WELDMENTS

This study analyzes the effects of Post Weld Heat Treatment (PWHT) on the mechanical properties and microstructure of Inconel 617 weldments produced by the Activated Tungsten Inert Gas (A-TIG) welding and Tungsten Inert Gas (TIG) welding. The TIG weld joints considered for this study were in an as-welded condition and underwent two different conditions of heat treatment including 1050∘C for 3 and 5[Formula: see text]h, respectively. The A-TIG weld joints studied were the as-welded type and the weldment was heat-treated at 1050∘C for 3[Formula: see text]h. The microstructure and the characterization of mechanical properties were performed for all weldments and a comparative assessment was made. Tensile strength and the hardness of the heat-treated samples were considerably higher than that of the as-welded samples. Impact toughness was slightly reduced after PWHT. Improvement in tensile strength could be attributed to the precipitation of the carbides and segregation of Chromium (Cr) and molybdenum (Mo).

Influence of flux agent composition on the ionization potential in A-TIG welding of the electrolytic tough pitch copper (Cu-ETP) sheets

Due to its high thermal expansion coefficient and high thermal conductivity, welding of copper and copper alloys is considered difficult and demanding. Activated TIG welding (A-TIG) welding has been widely researched as a welding method for obtaining deeper penetration on various metals. However, A-TIG welding of copper remains unexplored without guidelines on the influence of flux agents and the influence of the applied parameters and achieved mechanical properties in produced welds. In this paper three agents were used as single component fluxes: calcium oxide (CaO), silicon dioxide (SiO2) and sodium carbonate (Na2CO3) for A-TIG welding Cu-ETP sheets. Welds were characterized by visual inspection and macrostructural analysis, also bend testing and tensile strength testing were conducted. Microstructure of the weld with optimal mechanical properties was analyzed by means of Field Emission Gun-Scanning Electron Microscope (FEG-SEM) and also the chemical characterization of the weld was made by means of Energy Dispersive Spectroscopy (EDS). The results showed that the most effective flux used was silicon dioxide. Welds welded with SiO2 showed good results in visual inspection, macrostructure analysis and band test and also have acceptable values of tensile strength. However, oxide inclusions have been found in weld metal in significant percentage which could indicate the possible degradation of electrical conductivity of the material.

Study the Effect of Fluxes on Weld Penetration during Activated TIG Welding of SS304

Stainless steel is widely employed in a variety of industries, including aerospace, chemical processing, and transportation. It can be recycled indefinitely with no loss of property. The Gas Tungsten Arc Welding (GTAW) or Tungsten Inert Gas (TIG) technique is widely used for connecting thin pieces of stainless-steel. However, it is ineffective for combining heavy parts in a single pass. Activated TIG (A-TIG) dramatically enhances weld penetration up to 1.5- 4 times in a single pass. A-TIG is the centre of investigation among researchers because of its deep penetrating capacity. This article discusses the effects of particular flux powders, such as NaF and Fe2O3, on surface appearance and geometric shape. Weld of satisfactory appearance is produced using NaF powder as a flux in TIG welding, whereas, Fe2O3 powder results in a substantial increase in both the joint-penetration and weld-aspect ratio.

Process parameters based machine learning model for bead profile prediction in activated TIG Welding using random forest machine learning

The bead profile in the activated tungsten inert gas welding process depends on process parameters and flux composition. Using a conventional statistical-based model, the correlation of these input parameters with the bead shape geometry is complex. Therefore, machine learning-based techniques were implemented to predict the bead shape geometry, that is, penetration (D), width (w), and D/w ratio in the A-TIG welding process of austenitic stainless steel. Random forest regression and classification models were implemented to predict bead shape geometry in the A-TIG welding process. Based on the results, classification-based modeling was appropriate for predicting the bead profile. In addition, the correlation of the process parameters and flux composition with the bead profile was established.

Activated Tungsten Inert Gas Weld Characteristics of P91 Joint for Advanced Ultra Supercritical Power Plant Applications

Activated Tungsten Inert Gas Weld Characteristics of P91 Joint for Advanced Ultra Supercritical Power Plant Applications

Effect of welding processes on ferrite content, microstructure and mechanical properties of super duplex stainless steel 2507 welds

Abstract Super duplex stainless steel (SDSS) plates of 6 mm thickness have been welded using tungsten inert gas, activated tungsten inert gas, electron beam welding and friction stir welding processes. Among these, in the first two, melting and solidification of material occurs slowly whereas, it is faster in electron beam welding process and no melting occurs in friction stir welding. Macro and microstructural studies, hardness surveys, tensile tests and percentage of ferrite content were compared for all the welds. The ferrite–austenite phase balance is 50 % each, with electron beam weld metal at about 65 % ferrite. This showed the hardness of the weld metal and heat affected zones to be higher than base metal. The weldment joint efficiencies are more than 90 %. The fracture location is found to be in the weld metal for tungsten inert gas and activated tungsten inert gas weld, in the nugget for friction stir welds and in the base metal for electron beam welds. The ductility of electron beam weld joints is 32 % while it is around 20 % for the others. The preferred order while choosing the welding process should be activated tungsten inert gas welding, tungsten inert gas welding, electron beam welding, and friction stir welding.

Particle Swarm Method for Optimization of ATIG Welding Process to Joint Mild Steel to 316L Stainless Steel

316L stainless steel joined to mild steel is widespread in several applications to reach a requested good association of mechanical properties at a lower cost. The activating tungsten inert gas (ATIG) weld was carried out using a modified flux composed of 76.63% SiO2 + 13.37% Cr2O3 + 10% NaF to meet standard recommendations in terms of limiting the root penetration. Modified optimal flux gave a depth of penetration 1.84 times greater than that of conventional tungsten inert gas (TIG) welds and a root penetration of up to 0.8 mm. The microstructure of the dissimilar joints was investigated using a scanning electron microscope and EDS analysis. The mechanical properties of the weld were not affected by the modified flux. The results show that the energy absorbed in the fusion zone in the case of ATIG weld (239 J/cm2) is greater than that of TIG weld (216 J/cm2). It was found that the weld bead obtained with the optimal flux combination in ATIG welding can better withstand sudden loads. The obtained UTS value (377 MPa) for ATIG welding was close to that of TIG welding (376 MPa). The average Vickers hardness readings for ATIG welds in the fusion zone are up to 277 HV, compared to 252 HV for conventional TIG welding.

Numerical Investigation of the Iron and Oxygen Transport in Arc Plasma During an Activated Tungsten Inert Gas Welding Process

Numerical Investigation of the Iron and Oxygen Transport in Arc Plasma During an Activated Tungsten Inert Gas Welding Process

Investigation of the Mechanism of Powder Pool Coupled Activating TIG Welding

As a highly effective welding method, PPCA-TIG (Powder Pool Coupled Activating Flux–Tungsten Inert Gas) welding aims to achieve automated activation of TIG welding through the use of suitable activating fluxes. However, due to the unique transitional behavior of activating elements, the mechanism of PPCA-TIG is a little bit different from common activating TIG welding. In this research, a two-dimensional model is established to investigate the effect of four activating fluxes (TiO2, SiO2, MnO2, CaF2) on arc morphology and force. A series of welding experiments is performed to study the impact of the different activating elements on the molten pool. The results show that the increase in the penetration of TiO2 is related to the high arc temperature and great arc force and electromagnetic force in the molten pool. The problem of the softening of 3003 aluminum alloy welded joints is solved. Other activating fluxes are less effective than TiO2. The addition of calcium fluoride significantly affects penetration. The use of TiO2, SiO2 and MnO2 changes the molten pool viscosity and affects the molten pool oscillation, thus affecting the weld quality.

Analytical and Neural Network Analysis on Flux-Coated Aluminium Alloy by Activated TIG Welding with Synthesized Nanocomposites

This research focused to synthesize the material by the tungsten inert gas (TIG) welding process with support of appropriate flux coating material. Therefore the required amount of flux coating material was utilized to enhance the mechanical properties of the specified localized welded regions. Hence, this study concentrated to select the nano-SiO2 flux particles that were employed for TIG process. This activated TIG welding composes the flux-coated welding on the base metal of AA5083-H111, as this material was highly reactive with SiO2 by the presence of magnesium precipitates and well synthesized after the welding. The post- and preheat treatment process was achieved before and after welding. The selection of activated TIG process parameters composed of strengthened weld specimens along with constant parameters like electrode tip angle and flow rate, respectively. Initially, the process parameters were designed by the statistical analysis of Box Behnken method with support of regression formulation to determine the optimal solution. The maximum tensile strength was attained at the welding process parameters of welding speed (100 mm/min), voltage (13 V), and current (125 amps). The higher hardness was achieved at the process parameters of welding speed (80 mm/min), voltage (12 V), and current (125 amps), respectively. Finally, the neural network approach was utilized to verify the predicted responses of tensile and microhardness properties. The interaction plots, mean plots, and 3D scatter plots were influenced to enhance the process parameters. In this research, mechanical properties were enhanced by the flux-coated SiO2 and the analytical method also advances the optimal parameters.

Region-wise evaluation of strength and creep behavior of AISI 904L weldments by small specimen testing techniques

Super austenitic stainless steel AISI 904L is a premium stainless steel renowned for its outstanding characteristics and the ability to be maintained even under harsh situations. This alloy is widely used in a variety of engineering applications, and hence generating creep and indentation data of the material will prove useful for those concerned. Our study investigates the impression creep (IC) and automated ball indentation (ABI) performance in activated tungsten inert gas (ATIG) and hot wire tungsten inert gas (HWTIG) weldments of 10 mm thick plates of AISI 904L. ABI-evaluated strength correlates well with the conventional uniaxial tensile test and hardness data. IC studies were performed on base metal and welds by applying a load of 60 kg on a 1 mm diameter flat-end cylindrical punch at 650 oC. Several cycles of loading followed by partial unloading were performed on ABI specimens at 25 °C using a 0.76 mm diameter tungsten carbide spherical indenter. The results indicated that the ATIG weld excelled over the HWTIG weld with higher creep resistance. During the ABI analysis, the heat-affected zone of HWTIG weldment displayed higher UTS and ABI hardness values of 499 MPa and 185 HB, respectively. Hardness values generated by the ABI analysis are 174 HB, 161 HB, and 177 HB for the base metal, ATIG weldment, and HWTIG weldment, respectively. This was found to be very much in agreement with conventional hardness test results. The results cemented the ability of IC and ABI analysis to precisely predict the creep and mechanical properties of the base metal and weldments. Data generated through this study will benefit industries and researchers associated with AISI 904L.

Mechanical properties and microstructure of activated TIG welded similar joints of Inconel alloys by desirability approaches

This study discussed about the activated tungsten inert gas welding with utilizing of aluminium oxide flux coated material on the Inconel 800 nickel based alloys. The Taguchi L9 orthogonal array was arranged the input factors namely, current, welding speed and voltage to find out the output mechanical characteristics of tensile strength and hardness responses. The following input parameters ranges 70 to 100 (A) of current, 30 to 50 mm/min of welding speed and 11 to 15 (V) of voltages are utilized. The entire nine samples are attained better mechanical strength and hardness when compared to the base metal. It is revealed that the effect of flux coated Al2O3 in the Inconel 800 to enhance the tensile and microhardness. The desirability functional approach (DFA) was implemented to analyze the input parameters to uncover the multi-objective output responses into single responses with influence of composite desirability values. From the detailed analyzes of DFA the nine specimens employed with the composite desirability and its ranking arrangements to identify the optimal parameters. The rank 1 was allotted to 9th run specimen that parameters are 100 (A) at current, 70 mm/min of welding speed and 13 (V) at voltage, respectively. The contour plots showed the interactions among the input parameters and composite desirability’s with their outcomes.

Improvement in the microstructural properties of super duplex and austenitic stainless steel dissimilar joints by incorporating Ni-based austenitic interlayer

Tungsten inert gas welding (TIG) has remained a worldwide utilized welding technology in the industry to till date. Activated tungsten inert gas welding (ATIG) is also an advanced variant of TIG to enhance the penetration depth and reduce the width of the weld bead in single-pass compared to traditional TIG welding. The current study focuses on utilizing the Inconel interlayer approach to link dissimilar cold-rolled super duplex and austenitic stainless steels, which are mostly used in the offshore and marine industries. A systematic strategy is used to emphasize the studies conducted after using the ATIG interlayer procedure over the traditional TIG interlayer welding process. The research also studies and compares the microstructure, elemental mapping of the weld interface, phase identification and mechanical properties of dissimilar welded super duplex and austenitic steel samples. • ATIG welding approach for achieving single pass penetration of 6 mm thick plate with reduced weld heat input. • Without any weld defects such as weld porosity, undercut, overlap defect, and hot cracking a dissimilar welding of austenitic 202 and super duplex 32760 plates were successfully completed. • Microstructure evolution such as reduction in the width of heat affected zone, and reduction in the width of the unmixed zone was seen after using the ATIG interlayer weld technique. • Mechanisms such as reverse Marangoni and arc constriction in ATIG welding techniques could easily reduce parent metal loss in weld zones.

Effect of Oxide Flux Particle Size on Weld Bead Morphology of Hastelloy C-22

Activated tungsten inert gas welding (ATIG) welding is a new approach to Tungsten Inert Gas (TIG) welding that has the potential to improve weld penetration. This paper investigates the effect of micro and nanoparticle size oxide flux during TIG welding of Hastelloy C-22. The effect of SiO<sub>2</sub> and Al<sub>2</sub>O<sub>3</sub> oxide fluxes in terms of particle size and thermal stability on surface appearance, bead geometry, and microhardness of the fusion zone of hastelloy C-22 is investigated. The surface appearance of ATIG weld has a better appearance using nanoparticle size oxide flux when compared with the same micro size oxide flux. A slag layer produced by nano flux decomposition during TIG welding is very less compared to micro oxide fluxes. Nanoparticle SiO<sub>2</sub> flux has the potential to improve weld penetration and depth to width (D/W) ratio in the generated weldment when compared to microparticle SiO<sub>2</sub> flux during TIG welding Process. When nanoparticle Al<sub>2</sub>O<sub>3</sub> is used in TIG welding, weld penetration or the D/W ratio do not increase significantly. Due to the high voltage produced at the same arc length, TIG welding with nanoparticle SiO<sub>2</sub> flux produces a high heat input. Furthermore, higher arc temperatures produce by nanoparticle fluxes at the arc column, resulting in increased penetration depth.

Electrostatic probe analysis of SiO2 activating flux powders transition behavior in Powder Pool Coupled Activating TIG alternating current arc plasma for aluminum alloy

In alternating current Powder Pool Coupled Activating TIG welding for aluminum alloy, activating flux powders are transferred into the arc-pool coupling system through the outer gas to dramatically improve the weld penetration. The transition behavior of activating flux powders affects the weld penetration and forming intensely. To clarify the transition process of powder particles of activating flux SiO2 in the arc and its influence law and mechanism on arc characteristics, electrostatic probe powder capturing technology was developed to in-situ capture the in-flight powder particles at the expected position. Then, combined with SEM/EDS and thermodynamic calculation of the captured particles and spectrum diagnose of plasma compositions, the physicochemical process of SiO2 activating flux powder particles in the arc plasma was determined. Meanwhile, the influences of activating powders on current-carrying region, temperature and voltage of arc plasma were examined. The results show that, in the increase with heating time, the physical processes such as heating, melting, evaporation, breakage, collision, and fusion of SiO2 activating powders in the arc occur successively. The dissociation of SiO2 promotes the ionization of Ar and Al elements in the arc plasma. Compared with traditional TIG welding, the transition of activating flux powders makes the arc constrict, at the same time, the temperature along the axial centerline of arc raises, and the arc voltage significantly increases, all of which contributes to the obvious increase in weld penetration through SiO2 activating flux.

Effect of welding current on properties of activated gas tungsten arc super duplex stainless steel welds

Abstract A comparative evaluation of the influence of welding current on Tungsten Inert Gas (TIG) welding and Activated Tungsten Inert Gas (ATIG) welding on the depth of penetration and microstructure properties was performed. Various super duplex stainless steel (SDSS) beads on plate weld joints were studied. Visual observation showed that lower welding current resulted in partial weld penetration in the case of both TIG and ATIG weldments. Weld joints obtained by the ATIG process have a higher depth of penetration and depth/width ratios than weld joints obtained in the conventional TIG process at comparatively lower welding currents. Further, microstructural characterizations were performed using optical microscopy. The weld zone microstructure consists of grain boundary austenite (GBA), widmanstätten austenite (WA) and intragranular austenite (IGA). Ferrite percentage in bulk material and each weldment was measured using ferrite scope. The TIG-welded heat affected zone (HAZ) joints showed higher ferrite content than activated flux TIG-welded HAZ joints for various welding current conditions. Ferrite content measured in the weld-zone, HAZ and base material was within the ranges of the standard values. The TIG weld zone showed higher hardness than that of the ATIG weld zone.

Characterization of the microstructure and mechanical properties of activated tungsten inert gas welded and hot-wire tungsten inert gas welded super austenitic stainless steel AISI 904L

Super austenitic stainless steel AISI 904L is a premium stainless steel variant known for its superior properties and ability to retain the same in highly challenging conditions. This study investigates the feasibility of welding 10-mm thick plates of AISI 904L through activated tungsten inert gas welding and hot-wire tungsten inert gas welding methods. The fabricated joints are then subjected to solidification mode study, ferrite number analysis, microstructural characterization, and mechanical tests. Results of the solidification mode study indicated primary austenitic solidification in both the weld joints. The ferrite number measurement revealed that the hot-wire tungsten inert gas weld joint had a higher δ-ferrite content of 1.58 over 0.99 of the activated tungsten inert gas weld joint. A microstructure study confirmed the presence of refined equiaxed grains in the fusion zone of the hot-wire tungsten inert gas weld joint, while the activated tungsten inert gas weld joint displayed equiaxed grains crammed between the columnar grains and dendrites. Liquid penetrant inspection of bend-tested samples proved the soundness and quality of both weld joints. The hot-wire tungsten inert gas weld joint excelled over the activated tungsten inert gas weld joint with a higher microhardness value. During tensile tests, activated tungsten inert gas and hot-wire tungsten inert gas weld joints displayed average ultimate tensile strength values of 521 and 514 MPa, respectively. The impact toughness of the activated tungsten inert gas weld joint was 248 J, while it was 220 J for the hot-wire tungsten inert gas weld joint. Field emission scanning electron microscope analysis equipped with energy-dispersive spectroscopy and elemental color mapping provided details about weld microstructure and the reasons for the material's failure. The study proved the efficiency and soundness of the 10-mm thick joints of AISI 904L fabricated by activated tungsten inert gas and hot-wire tungsten inert gas welding techniques.

Welding of Super Duplex Stainless Steel and Austenitic Stainless Steel:#xd; Influence and Role of Bicomponent Fluxes

ABSTRACT This study investigated dissimilar tungsten inert gas and activated tungsten inert gas welding experimental results of austenitic 202 with a super duplex 32760 stainless steel. Their microstructural study revealed a balanced austenite-ferrite morphology that mainly consisted of Widmanstatten austenite (WA), grain boundary austenite (GA), and intergranular austenite (IGA). The study showed that the use of flux reduced the heat input necessary to achieve complete penetration, which tends to increase ferrite count in the heat-affected zone and the weld zone of weldment, resulting in minimizing the hot cracking propensity. Further, structure-property connections were also established by evaluating these two weldments’ tensile strength, impact strength, and microhardness. It was determined that weldments of activated tungsten inert gas weldment had better mechanical properties than traditional tungsten inert gas weldment. A weld zone fracture occurred near the austenitic weld interface in both weldments. It was noticed that unmixed zone formation on the side of the austenitic steel was to blame for the poor mechanical properties and failure of tungsten inert gas and activated tungsten inert gas weld joints. In both cases, the hardness distribution in the weld zones is ranked as super duplex stainless steel base metal > heat-affected zone of super duplex steel side > welded zone > heat-affected zone of austenitic steel side > austenitic base metal.