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The effects of pulsed gas tungsten arc welding parameters on the morphology of additive layer manufactured Ti6Al4V has been investigated in this study. The peak/base current ratio and pulse frequency are found to have no significant effect on the refinement of prior beta grain size. However, it is found that the wire feed rate has a considerable effect on the prior beta grain refinement at a given heat input. This is due to the extra wire input being able to supply many heterogeneous nucleation sites and also results in a negative temperature gradient in the front of the liquidus which blocks the columnar growth and changes the columnar growth to equiaixal growth.

The automotive and aero sectors seek lightweight high-strength materials for enhanced structural efficiency. Magnesium (Mg) alloys are used in defense, space, transportation, the electronic industry, and the biomedical field because of a good combination of properties viz., light weight, good specific stiffness, specific strength, processability, biocompatibility, good damping etc. Mg alloys are used in the cast and wrought forms, depending on the property demands, service requirements and cost. In addition, they are currently contemplated for non-loaded engineering structural applications. Many of these require the joining of Mg alloys, and it is timely to review the significant developments in the fusion of Mg alloys. Gas tungsten arc welding (GTAW) has often been preferred for Mg alloys because of its adaptability, stability, and economy. GTAW has various variants and a few advanced technologies. In addition, power beam processes provide some advantages amidst the challenges. The literature on fusion welding of Mg alloys is reviewed, focusing on the process / technology capabilities, effect of process parameters on the metallurgical transformation/ microstructural evolution and the resultant properties. Research gaps are identified relevant to the industrial needs to leverage the newer technologies to obtain quality weld joints also with view to achieve increased productivity and leveraging the capabilities for repair welding.

The automated weld quality assurance can improve efficiency and productivity. This paper presents the development of real-time weld quality assurance approach for gas tungsten arc welding (GTAW) using acoustic emission (AE) and air-coupled ultrasonic testing (UT). The major weld defect of interest in this paper is burn through, that is, melting through the base metal during welding that creates a hole/gap. The in situ monitoring system evaluates the changes in weld size leading to burn through by changing the weld heat input. Different categories of burn through are defined that include melting of the back of the plate without any molten metal exiting to formation of a hole in the plate. It is demonstrated that complete air-coupled UT cannot be used simultaneously with welding due to the influence of the magnetic field that develops in the weld torch during welding, which weakens the ultrasonic signal. Consequently, a rolling UT transmitter is combined with air-coupled UT receiver to increase the signal/noise value. Wave dispersion is detected due to the different levels of burn through. While UT method provides quantitative information about the weld state, any localized surface discontinuity causes sudden surges in the AE energy indicating non-uniform welding qualitatively. It is concluded that passive and active nondestructive evaluation methods should be combined to monitor weld quality real time for qualitative and quantitative assessment.

The welding process of dissimilar metals, with distinct chemical, physical, thermal, and structural properties, needs to be studied and treated with special attention. The main objectives of this research were to investigate the weldability of the dissimilar joint made between the 99.95% Cu pipe and the 304L stainless steel plate by robotic Gas Tungsten Arc Welding (GTAW), without filler metal and without preheating of materials, and to find the optimum welding regime. Based on repeated adjustments of the main process parameters—welding speed, oscillation frequency, pulse frequency, main welding current, pulse current, and decrease time of welding current at the process end—it was determined the optimum process and, further, it was possible to carry out joints free of cracks and porosity, with full penetration, proper compactness, and sealing properties, that ensure safety in operating conditions. The microstructure analysis revealed the fusion zone as a multi-element alloy with preponderant participation of Cu that has resulted from mixing the non-ferrous elements and iron. Globular Cu- or Fe-rich compounds were developed during welding, being detected by Scanning Electron Microscope (SEM). Moreover, the Energy Dispersive X-ray Analysis (EDAX) recorded the existence of a narrow double mixing zone formed at the interface between the fusion zone and the 304L stainless steel that contains about 66 wt.% Fe, 18 wt.% Cr, 8 wt.% Cu, and 4 wt.% Ni. Due to the formation of Fe-, Cr-, and Ni-rich compounds, a hardness increase up to 127 HV0.2 was noticed in the fusion zone, in comparison with the copper material, where the average measured microhardness was 82 HV0.2. The optimization of the robotic welding regime was carried out sequentially, by adjusting the parameters values, and, further, by analyzing the effects of welding on the geometry and on the appearance of the weld bead. Finally, employing the optimum welding regime—14 cm/min welding speed, 125 A main current, 100 A pulse current, 2.84 Hz oscillation frequency, and 5 Hz pulse frequency—appropriate dissimilar joints, without imperfections, were achieved.

An innovative wire-arc additive manufacturing (WAAM) process is used to fabricate Cu-9 at. pct Al on pure copper plates in situ , through separate feeding of pure Cu and Al wires into a molten pool, which is generated by the gas tungsten arc welding (GTAW) process. After overcoming several processing problems, such as opening the deposition molten pool on the extremely high-thermal conductive copper plate and conducting the Al wire into the molten pool with low feed speed, the copper-rich Cu-Al alloy was successfully produced with constant predesigned Al content above the dilution-affected area. Also, in order to homogenize the as-fabricated material and improve the mechanical properties, two further homogenization heat treatments at 1073 K (800 °C) and 1173 K (900 °C) were applied. The material and mechanical properties of as-fabricated and heat-treated samples were compared and analyzed in detail. With increased annealing temperatures, the content of precipitate phases decreased and the samples showed gradual improvements in both strength and ductility with little variation in microstructures. The present research opened a gate for in-situ fabrication of Cu-Al alloy with target chemical composition and full density using the additive manufacturing process.

Gas tungsten arc welding (GTAW) and its variants are esteemed as economically efficient welding methods for welding titanium alloys in the aerospace and nuclear industries. In the present work, the influence of electrode tip angle on weld geometrical elements, distortion, and hardness was investigated in commercially pure titanium (CP-Ti) sheets welded through pulsed-GTAW. Bead-on-plate (BOP) welding was performed on 2 mm thick CP-Ti sheets using electrode tip angles of 30, 45, 60, 75, and 90°. Defect-free welds were obtained by utilizing an indigenously developed shielding setup assembled with p-GTAW machine. The weld geometrical elements were evaluated using metallographic samples of weldment cross section under the stereomicroscope. The findings revealed that as the electrode tip angle increased from 30 to 60°, weld bead width decreased from 6.84 to 5.32 mm. Additionally, the weld penetration initially increased from 1.59 to 1.75 mm up to 60°, but subsequently decreased to 1.51 mm at 90°. Furthermore, increasing the electrode tip angle led to reduction in weld distortion. Microhardness measurements demonstrated an increase in hardness from the base (141 HV 0.2 ) to the weld region (151 HV 0.2 ), with a slight decrease observed in the HAZ (134 HV 0.2 ). This hardness trend across the weldment remained consistent with each electrode tip angle, and higher hardness was observed using large electrode tip angle.

The arc welding with weaving has been used widely to obtain better weld quality by avoiding lack of side wall fusion and improve the weld efficiency by obtaining the wide weld. But the effect of weaving process parameter on the weld is not clear. The aim of this work is to study the effect of process parameters on arc behavior and weld formation in Weaving-Gas Tungsten Arc Welding (W-GTAW), those parameters include welding current, tungsten electrode height from the electrode tip to upper surface of workpiece, weave angle, weave speed, and weave stop time on the left and right sides. The instantaneous arc shape and electrical signal data were collected by high-speed camera and electrical signal acquisition system, respectively. Furthermore, the weld morphology was also systematically analyzed. This result shows that the bottom surface radius of the arc changed with weaving in the W-GTAW. When the weave speed increased to 0.40 × 10 −1  rad/s, the change of the radius was the least, with only 0.10 mm drift, and the difference between the arc forces in the middle and the two sides of the molten pool was smallest in all experiments. Compared with the welding stability of each process, decreasing the tungsten electrode height, weave angle and speed could significantly enhance the welding stability. The forming coefficient of weld with a weave angle of 1.9° was 3.11. It shows that increasing reasonably the weave angle and speed can increase the weld penetration and might help reduce stress concentration and hot crack tendency of the weld. When the welding current is reduced to 130 A for W-GTAW welding, the hardness transition from base metal (BM) zone to weld zone (WZ) is more gentle. Furthermore, the W-GTAW technology shows great application potential in weld forming control by adjusting process parameters.

Weld root reinforcement is a critical geometric parameter governing stress concentration and structural performance in thin-walled stainless-steel piping systems designed to ASME B31.3. While current codes specify permissible dimensional limits, they do not explicitly quantify how incremental variations in root height influence stress distribution under realistic service loading conditions. This study integrates finite element analysis (FEA) with experimentally validated GTAW weld profiles to evaluate the structural influence of weld root height in 316L stainless-steel pipe joints. An experimentally manufactured 4 in schedule 10S joint with a measured root height of less than 1.5 mm was adopted as the baseline geometry. Additional models with reinforcement heights of 1.138, 2.0, 2.5, and 3.0 mm were evaluated under two representative load cases: (i) internal pressure combined with drag and axial thrust (LC-1), and (ii) internal pressure with thrust only (LC-2). The results demonstrate that reinforcement heights exceeding 2.0 mm increase von Mises, hoop, longitudinal, and radial stress gradients, with peak stresses shifting toward the weld toe under drag-inclusive loading. In contrast, reinforcement ≤2 mm provides smoother load transfer and reduced stiffness discontinuity across the weld interface. The combined numerical and experimental findings support a stress-informed upper limit of 2 mm for weld root reinforcement in thin-walled stainless-steel pipelines, offering a performance-based complement to existing dimensional acceptance criteria.

The aim of this study was to investigate the influence of the discharge parameters on the initial spatial instability of arcs after their initiation by the non-contact method in single-pulse electrode-negative gas tungsten arc welding. The investigated parameters were the P peak peak arc pressures, the T durations for achieving the peak arc pressure, and the P final arc pressures at the end of current pulses. It was found that increasing the current amplitudes from 50 to 200 A enhanced mean both the P peak values (from 0.25 to 4.00 kPa) and the P final levels (from 0.16 to 1.72 kPa). Enhancing the electrode diameters from 1.0 to 2.4 mm increased these experimental output parameters from 1.85 to 1.99 kPa and from 0.57 to 1.23 kPa, respectively, while they were decreased from 2.32 to 1.47 kPa and from 1.19 to 0.62 kPa after changing the sharpening angle of their tips from 30° to 90°. The period of the spatial instability of arc discharges was shortened from 14.4 to 5.8 ms by increasing the current amplitudes from 50 to 200 A. However, enhancing the electrode diameters from 1.0 to 2.4 mm increased its duration from 9.2 to 12.0 ms. It was also prolonged from 6.2 to 16.8 ms after changing the sharpening angle of the electrode tips from 30° up to 90°. The shortest duration of the arc stabilization period of 5 ms was observed when using the WL15 non-consumable electrode, while it was the longest (35 ms) for the WP one.

Weld quality plays a critical role in ensuring the structural integrity and long-term performance of critical piping systems used across petrochemical, oil and gas, marine, and healthcare sectors. Although gas tungsten arc welding, shielded metal arc welding, and gas metal arc welding are widely applied in pipe fabrication, existing studies often examine these processes independently and provide limited insight into the comparative influence of process parameters on weld morphology, microstructure, and mechanical performance. This review consolidates findings from recent research to evaluate how welding current, arc voltage, heat input, travel speed, shielding gas composition, and joint preparation interact to affect weld bead geometry, heat-affected zone evolution, tensile properties, hardness, and overall weld integrity in piping systems. The primary objective of this review is to critically compare fusion welding process parameter optimization strategies and to identify unresolved challenges in achieving controlled weld root geometry for high-integrity piping applications. Recent industrial failure investigations, particularly in ethylene oxide service piping, further underscore the importance of weld root control. Several documented leak events were traced to excessive root protrusion and inadequate interpretation of non-destructive testing data, where elevated reinforcement disrupted internal flow and promoted turbulence-induced degradation. These recurring issues highlight a broader industry challenge and strengthen the need for improved root-height optimization in critical piping applications. A significant research gap is identified in the limited optimization of weld root reinforcement, particularly in gas tungsten arc welding processes, where most reported studies document root heights exceeding 3 mm. Achieving a root height below 2 mm, which is an important requirement for reducing flow-induced turbulence and meeting industry acceptance criteria, remains insufficiently addressed. This review highlights this gap and outlines future research opportunities involving advanced parameter optimization and improved process monitoring techniques. The synthesis presented here provides a comprehensive reference for enhancing weld quality in critical piping systems and establishes a pathway for next-generation welding strategies aimed at producing high-integrity weld joints compliant with the American Society of Mechanical Engineers B31.3 requirements.