Gas Tungsten Research Articles

Advancements and Challenges in Wire Arc Additive Manufacturing – A Review

Wire arc additive manufacturing (WAAM) is a groundbreaking advancement in 3D metal printing, enabling efficient and cost-effective production of large, complex components using gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW). Suitable for metals like stainless steel, aluminium, and titanium alloys, WAAM involves layer-by-layer deposition of molten metal using an electric arc to melt wire feedstock. Despite its benefits, WAAM faces challenges with thermal cycles and microstructural inconsistencies, affecting component strength and ductility. Recent studies focus on microstructural analysis and mechanical properties, revealing varied microstructures due to distinct heat cycles. Research indicates consistent hardness across WAAM-fabricated components, with variations based on microstructural constituents. Optimizing the WAAM process involves understanding these characteristics and refining welding parameters. Advances in WAAM technology promise significant improvements in manufacturing efficiency, cost-effectiveness, and component quality across various industries.

Creep rupture and microstructural analysis of dissimilar welded joints of P92 steel and Alloy 617

Advanced ultra-supercritical plants are recognized for their efficiency and effectiveness in energy production, particularly when operating at elevated steam temperatures (700–720 °C). High-temperature components within these plants, including turbines, pipes, headers, and tubes, typically employ nickel-based alloys like Alloy 617, renowned for their outstanding resistance to corrosion and oxidation. Nevertheless, lower-temperature components (below 620 °C) frequently use less expensive ferritic-grade steels like P91 and P92. Welding these disparate materials balanced the plant’s performance and cost-effectiveness. This study focuses on the creep rupture behaviour of a dissimilar welded joint made through a gas tungsten arc welded joint between P92 steel and Alloy 617, utilizing a Ni-based Inconel 617 filler, at a test temperature of 650 °C under a stress of 140 MPa. A light microscope and a field emission scanning electron microscope were used for microstructural study. The investigation looks at how creep ruptures happen and how the microstructure changes inside the DWJ, and microhardness testing to comprehensively assess the joint’s performance under specific stress and temperature conditions. At 140 MPa and 650 °C, the sample demonstrated a creep rupture time of 54.5 h.

The effect of welding time on the tensile load capacity of dissimilar-metal stainless steel-carbon steel TIG-Spot welded joint

This study examines the influence of welding time on the tensile load capacity of spot TIG welds using stainless steel and low carbon steel plates (100 mm × 30 mm × 0.8 mm) as per AWS D8.9 standards. A constant welding current of 90 A was applied, with 2-, 3-, 4-, and 5-seconds welding times. Tensile properties, microstructure, and hardness were analyzed using a universal tensile machine, an optical microscope, a scanning electron microscope, and a Vickers hardness tester. Results show that the tensile load capacity increases with welding time, peaking at 4 seconds (≈4300 N), before dropping significantly at 5 seconds (≈4000 N) due to overheating, which weakens the joint. The findings highlight the critical role of optimizing welding time to maximize joint strength while preserving the material's microstructure. Overextended welding times compromise performance, emphasizing the balance required for achieving durable welds.

Enhancing Welding Productivity and Mitigation of Distortion in Dissimilar Welding of Ferritic-Martensitic Steel and Austenitic Stainless Steel Using Robotic A-TIG Welding Process

The P91 martensitic steel and 304L austenitic stainless steels are two mainly used structural steels in power plants. The major problem in conventional multipass tungsten inert gas (TIG) welding of P91/304L steel is high heat input and joint distortion, increased cost and time associated with V groove preparation, filler rod requirement, preheating and welding in multiple passes, and labor efforts. Hence, in this study, a novel approach of robotically operated activated flux TIG (A-TIG) welding process and thin AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA) sheet as the interlayer was used to weld 6.14 mm thick P91 and 304L steel plates with 02 passes in butt joint configuration. The joints were qualified using visual examination, macro-etching, X-ray radiography testing and angular distortion measurement. The angular distortion of the joints was measured using a coordinate measuring machine (CMM) integrated with Samiso 7.5 software. The quality of the A-TIG welded joints was compared to the joints made employing multipass-TIG welding process and Inconel 82 filler rod in 07 passes. The A-TIG welded joints showed significant reduction in angular distortion and higher productivity. It showed a 55% reduction in angular distortion and 80% reduction in welding cost and time compared to the multipass-TIG welded joints.

Comparative Study Between Friction Stir Welding and Tungsten Inert Gas Welding Processes

This study compares the properties of the aluminium alloy welded joints prepared by friction stir welding (FSW) to that of tungsten inert gas (TIG). It concentrated on the microstructure, hardness, corrosion resistance, and wear resistance. It has been found that the joints prepared by FSW have fine microstructure while coarse grains microstructure was obtained for joints produced by TIG welding. Also, the lowest Rockwell hardness measured at the centre of the welding line is 52 for joints prepared by FSW and 46 for ones produced by TIG welding. For corrosion resistance the reslt of tests indicated that the welded joints of the TIG process had higher corrosion resistance, the mass loss after 72 hours is 0.2519 grams from TIG joints and it is about double in the case of FSW joints (0.5263 grams). However, TIG joints have lower wear resistance compared to joints produced by the FSW process. It seems that the grain size of the welded joints, in these two considered welding processes, has a great effect on the investigated properties.

Surface Cladding of Mild Steel Coated with Ni Containing TiO2 Nanoparticles Using a High-Temperature Arc from TIG Welding

This study explores the use of a high-temperature arc generated during tungsten inert gas (TIG) welding to enhance the mechanical properties of the surface of AISI 1020 steel. An innovative two-step process involves using the high-temperature arc as an energy source to fuse a previously electrodeposited Ni/TiO2 coating to the surface of the substrate. The cladded surface is characterised by a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS), an optical microscope (O.M.) equipped with laser-induced breakdown spectroscopy (LIBS), Vicker’s microhardness testing, and pin-on-plate wear testing. The treated surface exhibits a unique amalgamation of hardening mechanisms, including nanoparticle dispersion strengthening, grain size reduction, and solid solution strengthening. The thickness of the electrodeposited layer appears to strongly influence the hardness variation across the width of the treated layer. The hardness of the treated layer when the Ni coating contains 30 nm TiO2 particles was found to be 451 VHN, validating an impressive 2.7-fold increase in material hardness compared to the untreated substrate (165 VHN). Similarly, the treated surface exhibits a twofold improvement in wear resistance (9.0 × 102 µm3/s), making it substantially more durable in abrasive environments than the untreated surface. Microstructural and EDS analysis reveal a significant reduction in grain size and the presence of high concentrations of Ni and TiO2 within the treated region, providing clear evidence for the activation of several strengthening mechanisms.

Improving Deposition Quality of Stellite Powder on Valve Seats by Optimized TIG Welding Parameters

The quality of the Stellite powder coated on these valve seats depends on the discharge profile and is crucial to the service length and quality of these seats, especially when called upon to work at their maximum capabilities. This research seeks to work out how to minimize blow holes in the TIG welding process when depositing Stellite powder while maintaining other desirable qualities of the weld. In this respect, the work uses the OVAT technique and Taguchi design approach to analyze the effect of the major welding parameters, such as weld speed, feed rate and welding current, on the formation of blow holes. The research shows that it is possible to gain a remarkable increase in weld quality when the parameters mentioned are strictly controlled. In this systematic experimentation, the optimal welding condition found out was the welding speed of 6.5 rpm, feed rate of 120 mm/min, and welding current of 150A. With this combination, these parameters were determined to reduce the chances of blow-holes forming and increase the welds' quality and durability. With respect to the study objectives, the present investigation offers a clear direction to enhance TIG welding of valve seats with special reference to minimize the defects. Analysis done in the study shows that the welding parameters have the greatest impact in reducing the blow holes; the feed rate is 56.61%, weld speed is 22.28% and welding current is 20.17%. The results enhance weld quality, offering rules for eradicating imperfections in the TIG welding of valve seats, which is crucial for high-performance sectors.

A Comparison Study of High-Temperature Low-Cycle Fatigue Behaviour and Deformation Mechanisms Between Incoloy 800H and Its Weldments

The high-temperature low-cycle fatigue (LCF) behaviour of Incoloy 800H and its weldments with Haynes 230 and Inconel 82 filler metals, which were fabricated with the gas tungsten arc welding (GTAW) technique, was investigated and compared at 760 °C. The results revealed that the Incoloy 800H weldments showed lower fatigue lifetimes compared to the base metal. However, the weldments with the Haynes 230 filler metal demonstrated an improved fatigue life at the low strain amplitude compared to both Incoloy 800H and the weldment with the Inconel 82 filler metal. The Incoloy 800H base metal showed pronounced initial cyclic hardening with hardening factors increasing with strain amplitudes. In contrast, the weldments with Haynes 230 and Inconel 82 filler metals displayed short initial cyclic hardening and saturation stages, followed by long continuous cyclic softening. The fractography and microstructure after LCF the tests were characterized with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Transgranular fracture with multiple crack initiations was the predominant failure mode on the fracture surfaces of both Incoloy 800 base metal and the weldments. TEM examination revealed that planar dislocation slips at the low strain amplitude evolved to wavy slips, eventually forming a cell structure at high strain amplitudes in the Incoloy 800H material as the strain amplitudes increased. However, the weld metal exhibited a planar slip mode deformation mechanism regardless of cyclic strain amplitude in the weldment specimens. The differing cyclic hardening and softening behaviours between Incoloy 800H and its weldments are attributed to the higher strength of the weldment specimens compared to the base metal. In the Incoloy 800H base material specimens, the reverse strains during LCF created wavy dislocation structures, which could not fully recover due to the non-reversible nature of the microstructure. As a result, cells or subgrains formed within the microstructure once created. In contrast, the higher strength of the weld metal in the weldment specimens significantly suppressed the formation of wavy dislocation structures, and deformation primarily manifested as planar arrays of dislocations.

Assessing ferrite content in duplex stainless weld metal: WRC ‘92 predictions vs. practical measurements

The weldability of stainless steels is largely controlled by the chemical composition, and alloys with ferritic or ferritic-austenitic solidification show the highest resistance to hot cracking. As the resulting phase balance also affects the final properties, it may be beneficial to both foresee and measure the weld metal ferrite content. The WRC ‘92 constitution diagram is currently the most accurate prediction tool available, but it does not take the cooling rate into consideration and the precision may be less accurate for stainless steels with high ferrite numbers (FNs). This study aims to assess the reliability of the WRC ‘92 diagram for weld metals with FN > 50. The chemical composition was altered through gas tungsten arc welding (GTAW) of UNS S32205 with ER347 filler wire that had been coated using physical vapor deposition (PVD) with either niobium (Nb), copper (Cu), nickel (Ni), manganese (Mn), carbon (C), or silicon (Si). The actual ferrite content was evaluated using image analysis, FeriteScope and X-ray diffraction (XRD). While predictions from the WRC ‘92 diagram were deemed acceptable for Ni, Si, and Mn, notable deviations were observed for Nb, Cu, and C. The FeriteScope exhibited a consistent trend with image analysis, albeit with slightly higher FN values, wider scatter, and the conversion factor from FN to vol% is open for discussion. The lowest accuracy and largest spread were obtained using non-contact XRD, rendering it unsuitable for ferrite measurements of welds. These findings underscore the need for improved prediction tools and appropriate measurement methods for assessing ferrite content in duplex weld metals.

Tribological behaviour study of SiO2-TiO2 coated Inconel 617 alloy fabricated by TIG welding

Tribological behaviour study of SiO₂-TiO₂ coated Inconel 617 alloy fabricated by TIG welding

Exposure assessment to fine and ultrafine particulate matter during welding activity in the maintenance shop of a steelmaking factory

Welding fumes are a main source of occupational exposure to particulate matter (PM), besides gases and ultraviolet radiations, that involves millions of operators worldwide and is related to several health effects, including lung cancer. Our study aims to evaluate the exposure to fine and ultrafine airborne particulate in welding operators working in a steel making factory.In October 2019, air monitoring was performed for four days in five different welding scenarios and in the external area of a steelmaking factory to assess the exposure to airborne particles, ultrafine (UFP) particulate and inhalable fraction, during welding activities. The airborne particles distribution as particle number and mass concentration were measured using a low-pressure electric impactor, model ELPI™ (range of sampling 0.006 μm and 10 μm), whereas the airborne inhalable fraction was collected by filtration, using the IOM Sampler selector.The particle concentration, i.e. the number of particles per cm3 (part/cm3) showed significantly higher exposure figures for nanoscale particles, especially for the fractions included in the last 4 stages sampled by ELPI (from 0.010 μm to 0.071 μm), the figure representing between 85 % and 91 % of the total, whereas for the last 7 stages (0.010 μm–0.314 μm), they represented from 98 % to 99 % of the total. The average figure was approximately 5.01 × 104 part/cm3, while the maximum average was 1.95 × 105 part/cm3 on TIG welding, with a peak of 1.52 × 107 parts/cm3. In terms of mass concentration, the levels of PM inhalable fraction ranged between 0.1 mg/m3 and 1.08 mg/m3.The results of the present study substantially confirm previous studies regarding the distributions in terms of number and mass of welding fumes for SMAW and TIG techniques on steel, the mass concentration levels resulting within the permissible exposure limits (PEL) indicated by OSHA regulations. The results highlighted the importance of the efficiency of localized aspiration systems and the need to apply prevention and protection measures despite the low levels of exposure measured in terms of mass. ConclusionOverall, The particle number concentrations showed an important contribution in the emission of UFP compared to background levels. The PM inhalable fraction was substantially contained within the PEL. Further studies are needed to better understand the chemical characterization of the particulate also considering further variables of the working process that could influence the levels of exposure to welding fumes.

Numerical simulation of temperature distribution and residual stress in TIG welding of stainless-steel single-pass flange butt joint using finite element analysis

Abstract Controlling defects such as deformation in the weld joint and the residual or superfluous stresses due to tungsten inert gas (TIG) welding or arc welding is a major concern for many industries like aeronautical, automobiles, nuclear or atomic power plants, crude oil or fossil fuel industries where pipes are in use and circumferential welding is done. Arc welding is a metal joining process, and TIG welding is applied to many industrial sectors that require high-quality welding. Simulation has been done on single-pass TIG welding on the Flange pipe of SS316 to evaluate transient temperature, residual stresses, and distortion. First, a 3D model is developed and assembled in SolidWorks. Second, in an MSC Patran, preprocessing of the FE model is done. Finally, in MSC Marc, thermal and mechanical simulation is performed. Based on this simulation, the accuracy of welding of the flange–butt joint made of SS316 is validated. In this study, the information regarding simulation of temperature dispensation and residual or superfluous stresses is done on the flange–butt joint, and it found the stresses are compressive at the weld bead area, and along the transverse direction, stresses changed to the tensile. The experimental data show that the steep curve at 0.00 mm represents a maximum temperature near the weld path at approximately 2,352°C, and the slant curve shows the far away points from the weld path. Comparing it with FE analysis, the maximum temperature attained was around 2,539°C. An approximate deviation of 7.365% was observed. The results of the study will provide experimental and simulation analyses for the welding of pipes of stainless steel for the transportation of oil and gases in the petroleum industries.

Analysis of GTAW and FCAW Welding in Impact Testing in Steel Micro Structures

Welded joints, which encompass the criteria of welding base metal connections in the material, welding speed, material quality, and material toughness, are an integral aspect of tank construction. Steel material joints frequently fail during the Gas Tungsten Arc Welding (GTAW) and Flux Cored Arc Welding (FCAW) welding procedures because air droplets become trapped in the steel material during the welding process. Finding the primary reasons for welding failures is the goal of this study. Impact and microstructure testing are used in the welding research method on SS400 steel. The FCAW welding process uses E71T-1C (Kobe) Electrodes Steel Familiarc AWS A5.2 E71T-1C) at varying currents of 80 A (Root), 100 A (Filler), and 120 A (Capping), against SS400 steel plate material with a thickness of 10 mm x 200 mm x 200 mm in V Buut seams Joints. The GTAW ER 70 SG (Familiarc Filler/Rods TG-S51T) Electrode classification allows for 90 A (Root), 110 A (Filler), and 120 A (Capping). Plate 1 has a value of 36.3 kJ/inch in the heat input calculation findings at the three section sites, while Plate 2 has the highest value of 61 kJ/inch. In the meantime, FCAW plate 2 has an impact strength value of 142.1 J, and plate 1 has an average hit in the test results at each of the three places of the specimen, according to the impact test findings. Three welding parameter points were used to record the findings of the metallographic testing's microstructure observations. plates 1 and 2 on the capping, filler, and root. being aware of the areas in the welded junction between plates 1 and 2 that are impacted by heat in the microstructure. Because of the material's strong heat input, which makes the steel brittle and promotes the formation of pearlite rather than ferrite, plate 2 has the highest value in the impact test

Parametric Optimization of Tig Welding of Aisi 316L Stainless Steel Using Response Surface Methodology

Parametric Optimization of Tig Welding of Aisi 316L Stainless Steel Using Response Surface Methodology

Effects of Postweld Heat Treatment on Interfacial Behavior and Mechanical Properties of Joints Welded with Cu/Ni-Cr Alloy.

Welded cable composed of nickel-chromium (Ni-Cr) alloy and copper is a crucial component in the resistance heating technology used for heavy oil production. Tungsten inert gas (TIG) welding was employed to join the copper and Ni-Cr alloy using copper filler wire, and the stability of the welded joint was analyzed under high-temperature service conditions. We examined the changes in the microstructure and properties of the welded joint after postweld heat treatment (PWHT) at 600 °C for 3, 6, and 12 days. The results showed that the welded joint was appropriately formed, with fractures occurring in the copper substrate. The average tensile strength of the welded joint was 240 MPa. The copper and nickel dissolved into each other, forming a Cu0.81Ni0.19 strengthening phase. A columnar crystal diffusion layer formed at the interface between the Ni-Cr alloy and the fusion zone after welding. Grain boundary migration promoted the continuous growth in the columnar crystals as the PWHT duration increased, eliminating the microdefects and inhomogeneities caused by welding. The microhardness progressively decreased from the Ni-Cr alloy side to the copper side. However, the nanoindentation results at the Ni-Cr fusion line initially decreased and then increased with increasing PWHT duration, which contrasted the overall hardness trend observed across the joint after PWHT.

Investigate on dissimilar welding of high-entropy alloy and 310S with various fillers

This study investigates the microstructure and mechanical properties of non-equimolar CoCrFeMoNi high-entropy alloy (HEA) and SUS310S stainless steel dissimilar welds using different filler materials. The dissimilar welding was performed on gas tungsten arc welding with Inconel 82, Inconel 625, and 316L stainless steel fillers. The non-equimolar CoCrFeMoNi HEA is shown effective weldability with these fillers, maintaining distinguished phase stability and structural integrity. Microstructural analysis revealed varied grain morphologies influenced by the heat in the fusion zone and heat-affected zone. Mechanical properties were evaluated through tensile and hardness tests, showing that welds with Inconel 625 filler exhibited superior strength and ductility. The weld hardness value was maintained at 170 HV, with a yield strength of 301 MPa and an ultimate tensile strength of 587 MPa, resulting in a joint efficiency of 106 %.

Influence of the welding thermal cycle on δ-ferrite evolution in the first layer of austenitic stainless steel (ASS) 308L produced by WAAM-GTAW

In this article, the effects on the weld bead geometry and heat affected zone at observe area explored on Wire Arc Additive Manufacturing Gas Tungsten Arc Welding (WAAM-GTAW). Based on GTAW process, layer by layer WAAM components are produced by deposition welding. Each welding process, the temperature is recorded at one point to determine temperature history. This article explained how specific thermal cycles, from the welding heat input to subsequent cooling phases, dictate the transformation behavior, phase stability, and morphological changes in δ-ferrite, ultimately shaping the material properties and performance of the welded. The factor affecting these properties were explained to identify evolution microstructure in observe area. The paper focuses on the impact of the temperature history to determine macrostructure and microstructure δ-ferrite evolutions of the observe parts deposited in the WAAM process. The thermal cycle experienced during welding lead to the transformation of δ-ferrite into austenite. The δ-ferrite transforms in austenite when the temperature rises above 800 °C–450 °C (T 8/5). Specimens that experienced temperatures above T8/5 exhibited vermicular (V) and eutectic ferrite (EF) modes of delta ferrite. Specimens that had peak temperature prediction records around 750 °C–525 °C in the T8/5 area exhibited ferrite with acicular (Ac) mode. Specimens approaching the lower line of T8/5 around 425 °C showed a transition from acicular to coarse Ac. Specimens with peak temperature records below the T8/5 line generally did not experience changes after the welding process.

Investigation of Vibratory-Assisted TIG Welding on Al6063 Alloy: Microstructural Behavior, Mechanical Properties, and Machine Learning-Based Hardness Prediction

Investigation of Vibratory-Assisted TIG Welding on Al6063 Alloy: Microstructural Behavior, Mechanical Properties, and Machine Learning-Based Hardness Prediction

Microstructural Aspects on Brazing Stainless Steels for High Temperature Applications

A wide range of applications request components that work in an environment where they are subject to high temperatures, combined with a corrosive action of the same environment. The components with a complex geometry can be obtained only using some assembling processes, among which are welding and brazing. One of the most important advantages of these processes is the possibility to obtain a sealed joint, that guarantees it to be waterproof. In comparison with welding process, brazing process has also an important technological advantage: it is a process that is able to produce a quality joint in a very small, narrow and tight places., where is very difficult or almost impossible to reach with other welding processes (e.g. GMAW/MIG – Gas Metal Arc Welding, GTAW/TIG – Gas Tungsten Arc Welding, SMAW – Shield Metal Arc Welding, FCAW - Flux Cored Arc Welding, SAW – Submerged Arc Welding). The research in this direction carried out in University Politehnica Timisoara, was focused on using brazing as a joining process to obtain a complex geometry part working in these environments. The brazed joint will create a dissimilar joint, putting in contact stainless steel with a Ag-Cu brazing alloy, which creates diffusion processes at microstructural level as well as phase transformations (due to thermal cycle and diffusion) which have a large impact on operating behavior of these joints. This paper presents some results on investigation phase and microstructural constituents transformations that took place in these brazed joints.

Multi-pass weld influence on metallurgical, tensile, impact toughness and fatigue crack growth behavior of gas tungsten arc welded Ti-6Al-4V joints

A comparative study on the influence of changing the number of weld passes on the metallurgical and mechanical properties of Ti-6Al-4 V alloy was carried out. Two welded joints involving 3-pass and 4-pass welding procedure were fabricated for 7 mm thick Ti-6Al-4 V plates using gas tungsten arc welding (GTAW) process. A compatible solid filler of Ti-6Al-4 V was used to weld these plates. A significant variation in the microstructure and the microhardness of the upper part of the fusion zones of these welds was observed. Equiaxed microstructure possessed by the base metal resulted into relatively better transverse tensile strength, ductility, and impact toughness than the 3-pass and the 4-pass weld. Widmanstätten and martensite-α′ microstructure associated with the fusion zone of the 3-pass weld resulted into a larger fraction of high angle grain boundaries (HAGBs) which accounted for higher resistance to fatigue crack propagation in this weld. Fusion zone of the 4-pass weld possessed lamellar and basketweave microstructure which had a lower fraction of HAGBs and, hence exhibited relatively lower resistance to fatigue crack propagation as compared to the 3-pass weld. However, equiaxed microstructure of the base metal could not offer much resistance to fatigue crack propagation, which resulted into relatively poor fatigue performance of the base metal. These fatigue studies indicate that both the weld joints exhibited better fatigue crack resistance than the base metal. This study established that 7 mm thick Ti-6Al-4 V joint welded using 3-pass welding procedure resulted into superior mechanical properties than those obtained by using 4-pass welding procedure.