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Dissimilar welding of duplex stainless steel (DSS) with high-strength low alloy (HSLA) was more complicated since they were utilized in automotive and aerospace design, which needed components with lower weight, higher tensile strength (TS), hardness, corrosion resistance. In this research paper, the main objective was to establish a gas tungsten arc welding process, on a 60∘ angle double groove on both sides of DSS and HSLA, using three different filler metals ER2594, ER70S2 and ER304. The welded surfaces of the specimens were analyzed to assess the microstructural characterization using SEM and Edax, and they were also tested to determine their mechanical and corrosion characteristics. In comparison to microstructural characterization, Mn and Si combination decreased the surface defects in the weldment made by ER2594. The determination of mechanical properties revealed that specimen A produced by ER2594 was superior to other specimens B and C, in terms of yield stress, TS and hardness. Similarly, improved corrosion resistance was achieved by the larger presence of Cr along with Ni in ER2594. In the welded joint, Ni combined with an appropriate proportion of other alloying elements in ER2594 enabled effective control over the ferrite-austenite phase balance, which was crucial for achieving the necessary combination of properties and weldability designed for particular applications. Among the three filler metals, ER2594 showed better microstructure uniformity, enhanced TS, hardness and superior corrosion resistance. [ABSTRACT FROM AUTHOR]

The cladding process reduces manufacturing costs by depositing super austenitic stainless steel onto low-carbon steel. Arc welding techniques, especially gas tungsten arc welding (GTAW), are commonly used for this purpose. This study evaluates the influence of heat input on cladding performance. Macroscopic analysis showed good fusion of the weld beads to the base metal with no defects. Higher heat input resulted in a lower dilution rate due to increased reinforcement. A microstructural analysis of the heat-affected zones revealed similar characteristics, with martensite formation attributed to cooling conditions. Increased microhardness was observed at the interface between the cladding and base metal, corroborating the microstructural findings. Additionally, a significant enhancement in corrosion resistance was noted in the deposited layers. This research contributes to optimizing cladding processes, ensuring better material performance in industrial applications. [ABSTRACT FROM AUTHOR]

This study investigates and establishes the effect of welding process parameters on the tribological performance of the fabricated weld using the gas tungsten arc welding (GTAW) process. Both ER 2594 and ER 70S-2 were used as filler metals to fabricate a dissimilar GTA weld between sDSS 2507 and N50 steels. sDSS 2507/N50 DWJs have substantial importance to the subsea oil-gas drilling industries, especially in tubing and coupler assembly. The thermodynamic study predicts microstructure evolution during weld fusion zone cooling. Dry-sliding tribology behaviors were investigated using a pin-on-disc dry-sliding wear tester with a constant load of 30 N, sliding speeds from 1.111 to 6.666 m/s, and distances from 500 to 3000 m. Scanning electron microscopy examined the worn surface's wear mechanism and progression. ER70S2-LHI specimen had the lowest volume loss (12.83 mm3), and the N50 BM exhibited the greatest (112.65 mm3). Due to its martensitic structure, ER70S2-LHI has the lowest wear rate (4.28 × 10–3 mm3/m), while N50BM demonstrates the highest wear rate (37.5 × 10–3 mm3/m). For both LHI and HHI weld conditions, ER70S2 filler welds outperform ER2594 filler welds by 85 and 60%, respectively, in volume loss and by 81 and 48%, respectively, in wear rate. N50 BM had poorest wear progression and the ER70S2-LHI weld zone the most. Sliding wear on pins from base metal and filler weld zones exhibits mixed-mode abrasive, adhesive, and fatigue wear, producing material removal as spalling and flaking. [ABSTRACT FROM AUTHOR]

This study aims to analyze the effect of 70-30 Cu-Ni filler metal on mechanical and microstructural properties of Al 2024 and stainless steel 304 hybrid joints fabricated through the gas tungsten arc welding technique. The mechanical properties, i.e., tensile strength and microhardness, of Al-SS joints have been analyzed and evaluated through joint interfacial microstructure analysis. The optimum tensile strength (155.746 MPa) has been obtained at welding current ranges between 75 and 80 A, welding speed of 110–115 mm/min, and gas flow rate of 9.75-10 L/min, whereas maximum microhardness (300 HV) at welding speed of 115-120 mm/min, welding current of 70-75 A, and gas flow rate of 9.5-10 L/min. The fine equiaxed dendrites at the interface of the aluminum weld zone and the thin interfacial layer at the SS304 weld zone interface contributed to the higher tensile strength. Scanning electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction reveal the ductile CuAl, NiAl3, and NiAl phases instead of Fe-Al brittle phase, improving hybrid bonding between Al 2024 and SS 304. The dimples and tear ridges microstructure have been observed for high-strength joint, while cracks and cavities on the fracture surface indicate its brittleness and low strength (102 MPa). [ABSTRACT FROM AUTHOR]

This work discusses the effect of gas tungsten arc welding (GTAW) variables on the welding transverse tensile strength and hardness of S 235JR at different groove configurations. The welding microstructure and numerical fracture mechanism are also discussed. GTAW is increasingly emerging in the local industry due to its advantages over conventional shielded metal arc welding (SMAW). The properties of steel welding have always concerned manufacturers and researchers. Since steel structures experience forces such as tensile, it's vital that good welding has increased tensile strength. It was reported that the hardness of welding affects the welding properties and, therefore, the integration of welded structures. The groove shape of the joining ends determines the size of the FZ and affects the dilution; thus, it is important to study the groove shape due to its effect on the final properties of welding. The results showed an increased welding traverse tensile strength (251 MPa) at higher welding speeds (150 mm/min) and V-shaped groove welding. The Vshaped groove welding that obtained higher tensile strength (251 MPa) has shown higher grain boundary ferrite and PF volume friction in the FZ and finer PF in the HAZ due to its higher interpass heat input. Higher traverse tensile strength welding has shown increased bainite and lower bainite volume friction in FZ and a finer grain structure in HAZ. The failure due to tensile force starts at the welding root, according to numerical analysis, and a double V-shaped groove has shown deformation balance at the tensile test. [ABSTRACT FROM AUTHOR]

The current study aims to investigate the effect of the hybrid thermal tensioning technique transient thermal tensioning and trailing intensive cooling (TTT–TIC) on residual stresses and distortion of titanium Ti-5Al-2.5Sn and stainless steel 304 gas tungsten arc welded (GTAW) joints using Nb–Cu composite filler. The two preheating oxyacetylene torches are used for in-situ heating at TTT condition whereas compressed CO2 has been employed for in-situ trailing cooling of weld at TIC condition. The residual stresses and distortion have been evaluated at the distance between preheating torches (DA) in the case of TTT, the distance between the cooling source and the welding torch (DB) in case of TIC, and optimal distances DA and DB in case of hybrid TTT–TIC condition. The minimum values of tensile residual stresses and distortion of 98 MPa and 0.904 mmm on SS side, and 84 MPa and 0.425 mm on Ti side have been obtained at TTT–TIC condition. A significant percentage reduction in tensile residual stresses has been attained at novel TTT–TIC of 60% on SS side, and 63.48% on Ti side than conventional GTAW, 14.7% on SS side and 18.4% on Ti side than TIC condition, 52.20% on SS side and 56.02% on Ti side than TTT condition at hole depth of 0.3 mm on both plates. In the case of TTT–TIC, a percentage reduction in transverse distortion of 43.61, 24.81, and 32.09% have been achieved over the conventional GTAW, TIC, and TTT conditions respectively. In case of longitudinal distortion, the 57.07% reduction in distortion on Ti and 45.87% on SS side under the TTT–TIC method have been achieved. [ABSTRACT FROM AUTHOR]

This study investigates the structure–property relationship in a dissimilar joint between super duplex stainless steel (sDSS 2507) and pipeline steel (X-70) using gas tungsten arc welding and ER2594 filler. Tubing and risers used to transport hydrocarbons are regularly joined using these dissimilar metals. The microstructures of lower heat input (LHI-0.7 kJ/mm) and higher heat input (HHI-1.4 kJ/mm) weldments were examined to understand the influence of heat input on the structure–property relationship. The weldments' mechanical characteristics were tested via hardness, impact, and tensile tests. Base metal and weld zone/interface characterization were studied utilizing optical and scanning electron microscopes with energy-dispersive spectroscopy (EDS). Elemental variation was confirmed by EDS spectra, elemental line mapping, and electron probe microanalysis with wavelength-dispersive spectrometer along the weld interface and weld zone. Significant microstructure variation was observed in X-70 BM at the LHI and HHI weld interfaces. Type II boundary and macro-segregation forms like peninsulas and islands were present in both weldments. In LHI and HHI weldment, duplex microstructure dominates the weld zone cap and filler pass. In the backing pass, duplex microstructure replaces skeletal ferrite, which predominates in the root pass of the HHI weld zone. LHI weldment has an average microhardness of 275 ± 7 HV0.5, while HHI had 285 ± 5 HV0.5. Both weldment's tensile tests revealed that the sample fractured on the weaker X70 BM side. LHI and HHI weldments had 600 MPa and 610 MPa ultimate tensile strengths and 22% and 18% elongation percentages, respectively. LHI weldments (200 ± 7 J, 210 ± 4 J) and HHI weldments (210 ± 5 J, 220 ± 8 J) have lower average impact toughness in cap and root pass than the sDSS 2507 BM (320 ± 3 J) and X-70 BM (300 ± 6 J), respectively. The increase in heat input led to a minimal 2% difference in tensile strength, a notable 10% increase in hardness, and a slight 5% variation in impact toughness between LHI and HHI weldments. Marine and offshore applications may benefit from investigating the sDSS 2507/X-70 DWJ's process parameter selection, thermodynamic analysis, and structure–property relationship. [ABSTRACT FROM AUTHOR]

Restrictive operating conditions (even exceeding 700 °C) of materials in advanced ultra super critical (AUSC) power plants and the need to minimize manufacturing and maintenance costs require the production of dissimilar metal welded joints (DMW). Significant differences in the physical and chemical properties of welded materials lead to phenomena that reduce the weldability of the metals used and force the search for solutions that limit unfavorable phenomena, e.g., the use of buttering layers. The study presents a comparison of two types of joints with Alloy 617 (UNS N06617) and ferritic P92 (UNS K92460) steel made using Inconel 82 (ENiCrFe-3) and Inconel 617 (ERNiCrCoMo-1) alloys buttering layer and the corresponding chemical composition of filler metals. All areas of the joints made with the gas tungsten arc welding process were subjected to structural investigations (optical microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) and mechanical tests (microhardness, room and high temperature tensile, and toughness testing). Despite the more complicated welding procedure, sound welded joints were obtained with favorable properties resulting, inter alia, from the reduced thickness of the martensite layer in HAZ of P92 steel and the limited diffusion of alloy components compared to welded joints without the buttering layer. This also resulted in a reduction of the maximum hardness (especially in the case of Inconel 82 buttering—by 15–30 HV0.5 in comparison with Inconel 617 buttering) and an increase in strength while limiting the decrease in plasticity (even 663 MPa tensile strength and 21% of elongation for Inconel 617 buttered joint). Moreover, improved high-temperature performance (approximately 70–100 MPa) of the welded joint following the application of the buttering layer was confirmed. The presented results allow for drawing general conclusions that both proposed welding procedures can be recommended for use in the working conditions occurring at AUSC. [ABSTRACT FROM AUTHOR]

This work optimizes the current (I), voltage (V), flow rate (F), and arc gap (G) of the gas tungsten arc welding (GTAW) of the Ti40A titanium alloy to decrease the heat input (HI) and improve the ultimate tensile strength (TS) and micro-hardness (MH). The radial basis function network (RBFN) was utilized to present performance measures, while weighted principal component analysis (WPCA) and an adaptive nondominated sorting genetic algorithm II (ANSGA-II) were applied to estimate the weights and generate optimal points. The evaluation via an area-based method of ranking (EAMR) was employed to determine the best solution. The results indicated that the optimal I, V, F, and G are 89 A, 23 V, 20 L/min, and 1.5 mm, respectively. The improvements in the TS and MH were 1.2 % and 19.8 %, respectively, while the HI was saved by 18.4 %. The RBFN models provided acceptable accuracy for prediction purposes. The ANSGA-II provides better optimality than the conventional NSGA-II. The HI, TS, and MH of the practical GTAW Ti40A could be enhanced using optimality. The optimization method could be utilized to deal with optimization problems for not only other GTAW operations but also other machining processes. [ABSTRACT FROM AUTHOR]

In order to realize the heat input regulation in the gas tungsten arc welding (GTAW) process, a novel compound excitation device consisting of a longitudinal magnetic field and a cusp magnetic field was developed in this paper. The magnetic field distribution law in the arc zone was analyzed under various excitation parameters of the device. Using 316L austenitic stainless steel as the base metal, the variation law of arc and weld penetration under different coupling excitation parameters was studied. The research reveals that the magnetic induction intensity in arc zone approximately conforms to the linear superposition law of two single magnetic fields. Under the compound excitation device, the welding arc is compressed while maintaining its deflection, causing its cross-section to change from circular to elliptical. Under the premise that the longitudinal excitation current maintains the arc deflection angle, an increase in cusp excitation current results in a decrease in weld width and arc bottom area, while increasing weld penetration, metal melting area, and arc voltage. These results indicate that the compound excitation device can effectively regulate the heat input distribution and arc heat flux density. [ABSTRACT FROM AUTHOR]

Cultivator coulters show high wear in use, which causes excessive machine stops to replace parts and, consequently, high costs for the agricultural producer due to the exchange of these components. The present work evaluated the wear resistance of a cultivator coulter coated with Fe–Cr-Nb cladding applied by gas tungsten arc welding (GTAW). The tests were carried out specifically on sandy and compacted soil, in the severe field conditions found in the southern region of Brazil, in the city of Bagé, RS. The cultivator coulter was characterised by optical microscopy, roughness and coating thickness measurements, grazing-incidence X-ray diffraction analysis (GIXRD), and SEM/EDS. The volume losses of cultivator coulter were evaluated using an "Absolute 7330SI" laser scanner and the SPACE CLAIM 2021 R2 software. Soil compaction was determined by penetrometer test, and the soil composition analyses were also performed. The uncoated cultivator coulters were completely eroded in approximately 22 ha. However, the cultivator coulters coated with Fe–Cr-Nb cladding resisted during the 30 ha of the tested area. Extrapolation of the results suggests an increase of approximately 100% in the wear resistance of the coated cultivator coulter. [ABSTRACT FROM AUTHOR]

In this study, the effects of SiC and TiB2 reinforcement particles on the corrosion behaviors of the surface composites of an Al5052 substrate produced with a gas tungsten arc welding (GTAW) technique were investigated. The electrochemical behaviors of the base metal (BM) and surface composites were evaluated by open-circuit potential monitoring, potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) in two solutions: 0.5 M H2SO4 and 3.5% NaCl. The results of PDP and EIS showed that by adding reinforcement particles on the surface, the corrosion resistance decreased in both environments relative to BM. Among Al5052-based surface composites, the AA5052/SiC + TiB2 composite in 3.5% NaCl solution and AA5052/TiB2 in H2SO4 solution showed the lowest corrosion resistance due to the formation of microgalvanic couples in the Al matrix. The corrosion resistance of Al5052-based surface composites in 3.5% NaCl solution was much better than that in 0.5 M H2SO4. Furthermore, scanning electron microscopy (SEM) analysis confirmed the PDP and EIS results. The SEM image of the corroded surface of AA5052/TiB2 exhibited severe pitting corrosion in both solutions relative to the other composites. In contrast, the AA5052/SiC composite showed a relatively lower corrosion rate in both 3.5% NaCl and 0.5 M H2SO4. Hardness tests provided evidence for improved mechanical properties of the composites in comparison with the BM. In particular, composites containing TiB2 showed the highest hardness, followed by AA5052/SiC + TiB2 composites. [ABSTRACT FROM AUTHOR]

A fine-grained fusion zone characterises a tough aluminium weld. To improve the solidification characteristics and refine the grains in aluminium welding, different inoculation particle combinations were introduced to the filler wire by solid state metal screw extrusion. Filler wires were I-joint welded with two different welding methods to reveal the potency for grain refinement. Grain size, microstructure, porosity content, and hardness across the weld was revealed. Gas metal arc welding with a Ti-TiC inoculated filler wire exhibited a remarkable grain refinement of 91% compared to a base reference of commercial pure aluminium. The Al 3 Ti intermetallic phase was found as nucleation point. Gas tungsten arc welding showed lower grain refinement potency, and no Al 3 Ti phase was found in any weld. Thus, the effect of welding method must be taken into consideration upon development of inoculant containing filler wires. [ABSTRACT FROM AUTHOR]

This research focuses on the effect of heat input of super duplex stainless steel (sDSS 2507) and nitronic steel (N50) dissimilar welded joints. Two heat input combinations selected as lower heat input (LHI) (0.62 kJ/mm) and higher heat input (HHI) (1.01 kJ/mm) were preferred during the operation of the gas tungsten arc welding process (GTAW) process using ER2594 filler. The macrosegregation like an island, peninsulas are observed in both weldments' HAZ and weld zone. The presence of secondary austenites (γ2) precipitation is observed in HAZ and root region of weldments. As heat input increases, the ferrite content of the weld zone in HHI decreases. Nevertheless, HHI had an advantageous effect on austenite nucleation in the HAZ. To ascertain the mechanical characteristics of the dissimilar metal welds (DMWs), tests such as the Vickers micro-hardness test, Charpy impact test, and tensile test were conducted. The mechanical evaluation reveals that the average hardness of LHI shows more hardness of 280 ± 4 Hv0.5 than HHI weldment of 270 ± 3 Hv0.5. Hence, weld zone, HAZ, and interface hardness do not indicate any significant change with the increment in heat input, which can be credited to the phase balance of ferrite/austenite. The tensile strength of LHI and HHI weldment is 895 ± 4 MPa and 900 ± 5 MPa, respectively, but LHI weldment displays better ductility. The Charpy impact test reveals that the impact toughness value decreases with increased heat input (i.e., 165 ± 5 J and 145 ± 3 J for LHI and HHI weldment, respectively) because of the secondary phase formation and increased grain size. However, the weld metal's Charpy impact toughness was more than the ASME standard value (> 41 J) and the EN 1599:1997 standard value (> 47 J). The microstructural observation and mechanical characterization suggest that lower heat input could be beneficial for weld's structural integrity. [ABSTRACT FROM AUTHOR]

Welding and joining Titanium and its alloys are always challenging because getting a contamination-free joint is difficult with arc welding. For this concern, an attempt was made with and without shielding arrangements using the Gas Tungsten Arc Welding (GTAW) process on the Ti-6Al-4V alloy sheet. To study the presence of oxygen and other elements with respect to surface colourization at the weld zone, an Energy-dispersive X-ray spectroscopy (EDX) analysis is carried out. Based on the EDX analysis, post-flow and pre-flow shielding gases are also included in the operation window. Bead on Plate (BoP) trials are performed using the shielding arrangement setup and selected parameters on the thin sheets (2 mm) of Ti-6Al-4V. After examining the BoP trails, defect-free joins in a 2 mm sheet are fabricated using the optimal welding parameters. The microstructure of the joint is captured and compared with the simulation work. Compared to the base metal, coarse and enormous grains are identified at the weld zone. Due to the proper shielding, no cracks appeared in the joint subjected to the three-point bend test. The considerable heat input during the GTAW process resulted in the nucleation of (ά) in FZ, as spotted in the TEM images. The microhardness value at FZ for base metal is 373 HV and 332 HV, respectively. It is confirmed that the suggested shielding setup could prevent contamination in welds resulting in better mechanical properties. [ABSTRACT FROM AUTHOR]

Using Gas Tungsten Arc Welding, or TIG Welding, good quality weld can be obtained. In this process, a shielding Gas is used to avoid atmospheric contamination of the molten weld pool. In the present work, bead profile in aluminium workpiece is observed as welded by AC TIG welding under 100% argon gas shield. Effects of variation of arc frequency, current and stand-off distance on bead profile are investigated. In the experiment, the bead-on-plate welding of 14 treatments is performed on Al 1000 series aluminium plates without a filler wire utilizing Central Composite Design system of Response Surface Methodology (RSM). Gas pressure is maintained at 2 kg/cm2 with gas flow rate of 15 lit/min, welding speed of 100 mm/min, electrode diameter of 3 mm and wave balance of -25. From this investigation, it is observed that an increase in welding current increases weld penetration. These are caused by the increase in heat input with the increase in weld current and decrease in torch travel speed. An increase in stand-off distance is also observed to cause a decrease in weld penetration. Analysis of variance (ANOVA) is also performed on the observed results. Regression equations are formed relating the response to the factors (independent variables). Linear relationships are found to be quite significant for both the cases of penetration and weld bead width. Acceptable correlation coefficients (R2) more than 95% are obtained in case of depth of penetration and more than 99% in case of bead width indicating effectiveness of the results observed. [ABSTRACT FROM AUTHOR]

Hot wire Gas Tungsten Arc Welding (GTAW) process is selected for the fabrication of thick section modified 9Cr 1Mo steel components of Steam Generators (SGs) for 500MWe Prototype Fast Breeder Reactor (PFBR) at Kalpakkam, India. During the welding procedure qualification for fabrication of SGs, the 30 mm and 62 mm thick modified 9Cr 1Mo steel welds were subjected to chemical analysis, visual examination, liquid penetrant examination, radiography examination, micro-hardness tests, longitudinal and transverse tensile tests (at ambient temperature and 525 °C), bend tests, drop weight tests and impact tests (at 0 °C and +18 °C). Literature reveals both positive and negative view on the welding of thick-section steel components. Limited information is available in the open literature on the effect of thickness on material properties of modified 9Cr 1Mo steel welds made by the hot wire GTAW method. In view of the above, authors attempted to systematically investigate the influence of thickness on the mechanical properties of modified 9Cr 1Mo steel welds made by the hot wire GTAW process. In this paper, the chemical compositions, hardness, tensile strength, bending strength and impact properties of 30 mm and 62 mm thick welds produced by narrow gap hot wire GTAW process are characterized and compared. It is found that the mechanical properties of 30 mm and 62 mm thick welds are comparable except the impact properties at 0 °C. The impact strength at 0 °C for a 62 mm thick weld was found inferior in comparison with a 30 mm thick weld. [ABSTRACT FROM AUTHOR]

The purpose of the method of AC/DC mixed gas tungsten arc welding (GTAW) is to improve the welding efficiency of aluminum alloy AC-GTAW. It is expected to make a great change in the aluminum alloy manufacturing industries. The feature of AC/DC mixed GTAW includes two parts, AC mode and DC mode, during the welding process. A comparison study between the AC/DC mixed GTAW and AC-GTAW is carried out by analyzing the arc characteristics and weld formation. The results showed that the uniformly distributed AC and DC signals were obtained in the AC/DC mixed GTAW. The front width and back reinforcement of the weld bead in the AC GTAW and the AC/DC mixed GTAW increased first and then decreased with increasing frequency. The geometrical parameters of the weld cross-section in the AC/DC mixed GTAW was increased, when the same frequency was used. For example, the frequency of 30 Hz was employed, the front width of the weld bead in the AC/DC mixed GTAW was increased to 0.3 mm compared with that of the AC-GTAW. The AC/DC mixed GTAW has a greater effective heat input compared with the AC GTAW due to introduction of the DC mode. [ABSTRACT FROM AUTHOR]

A unique methodology has been developed with the compilation of two magnets to produce the double axial magnetic field, and the effect on the arc shape and the bead characteristics in the gas tungsten arc welding (GTAW) process have been investigated. The load-carrying capacity of the joint depends upon the bead geometry. The developed methodology is capable of altering the arc shape and consequently the bead geometry of weld as per the requirement. Experimental results show that the double axial magnetic field changes the arc shape from a conical to constricted conical. It is further observed that magnetic configurations North-South-South-North (N-S-S-N) and Zero-Zero-South-North (0-0-S-N) provided better results than other configurations. The North-South-South-North (N-S-S-N) configuration produced a minimum penetration (0.98 mm) and a maximum shape factor (7.81), along with good appearance of weld beads. This configuration is suitable for cladding and hardfacing applications. The increased penetration (3.03 mm) was achieved with the Zero-Zero-South-North (0-0-S-N) configuration compared with conventional welding (2.20 mm). Similarly, this configuration yielded a higher bead width (8.13 mm) than conventional welding (5.90 mm). This configuration is suggested for the single-pass welding operation. [ABSTRACT FROM AUTHOR]

In this study, UNS S31803 duplex stainless steel and Hastelloy C-276 nickel-based superalloy were joined by gas tungsten arc welding (GTAW) process. Nickel based ERNiCr-3 and ERNiCrMo-3 filler metals with different chemical compositions were used for joining the dissimilar metals. Metallurgical structures of the joint parts were determined by microstructural characterization studies. In mechanical characterization, both hardness and impact toughness were measured. Corrosion behavior of the welds were investigated by potentiodynamic polarization tests in 3.5% NaCl solution. Characterization studies showed that (i) weld metals had a dendritic/cellular solidification structure which changed due to thermal effects in all passes from the surface to the root, (ii) depending on the chemical composition of the filler metal, Nb-rich carbides and Laves phase were formed in the weld metal, (iii) the amount of Mo affected toughness, hardness, and corrosion resistance. [ABSTRACT FROM AUTHOR]

The development of techniques to improve the welding of super duplex steels is necessary in order to ensure that the phase balance and properties of the material are not affected during this process. Hybrid arc-laser welding is a perfect combination of the advantages of both processes, producing deeper weld beads with more balanced phases than the pulsed laser process. Here, the objective was to improve the corrosion resistance of UNS S32750 weld beads by increasing the volumetric austenite percentage in the fusion zone (FZ) with a hybrid process of GTAW (gas tungsten arc welding) and pulsed laser Nd-YAG (neodymium-doped yttrium aluminum garnet). Welds were performed in bead on plate conditions with fixed laser parameters and a varying heat input introduced through the GTAW process. Additionally, welds within a nitrogen atmosphere were performed. After base metal characterization, an analysis of the FZ and heat affected zone were performed with optical microscopy, scanning electron microscopy and critical pitting tests (CPT). The synergy between the thermal input provided by the hybrid process and austenite-promoting characteristic of nitrogen led to a balanced volumetric austenite/ferrite fraction. Consequently, the results obtained in CPT tests were better than conventional welding processes, such as laser or GTAW solely. [ABSTRACT FROM AUTHOR]

A dissimilar welded joint of Inconel 718 and 304L austenitic stainless steel was prepared using a combined procedure with the gas tungsten arc welding and shielded metal arc welding processes by employing the Ni-based fillers: ERNiCr-3 and ENiCrFe-3. The welded joints were investigated for metallographic testing and mechanical properties, and a relationship was established between the microstructure and the resultant mechanical properties. Microstructural observation revealed the formation of the unmixed zone on the 304L SS side. The weld metal showed that the fully austenitic microstructure consisted of the Nb- and Ti-rich carbide phases along the inter-dendritic spaces. The tensile test results at room temperature showed the failure from the weld metal which might be due to alloying element segregation along the inter-dendritic spaces. However, a tensile test at 600 °C showed the failure from the 304L SS base metal with a tensile strength and % elongation value of 377 MPa and 24%, respectively. The hardness plot showed the average hardness value of the weld metal of 236 ± 5 HV, which was higher than the 304L SS BM (204 ± 4 HV) but lower than the IN718 BM (243 ± 5 HV). The impact toughness of the weld metal was 109 J, which was significantly lower than the base metals. The poor impact strength of the weld metal might be due to the evolution of the NbC phase along inter-dendritic spaces. [ABSTRACT FROM AUTHOR]

A bimetallic composite pipe butt joint was prepared by automatic gas tungsten arc welding (GTAW). The microstructure and pitting properties of the joint were investigated. The results show that the microstructure of the joint is columnar crystal, columnar dendrite, and equiaxial crystal. Mo, Nb, and Cr segregate in joint and form Laves and NbC precipitates in the interdendritic. The heat-affected zone (HAZ) becomes the preferred region for pitting due to recrystallization behavior and large and continuous Laves, this was demonstrated by both immersion corrosion and electrochemical experiments. To better understand the pitting behavior of the joint, this study discusses the mechanism of passive film rupture and pitting development, and uses electrolytic corrosion by Nital to simulate the morphology of the initial corrosion pits around the Laves phase. [ABSTRACT FROM AUTHOR]

Aluminium alloys and magnesium alloys offer superior properties with less density that allow designing structures with reduced cost, high efficiency, and material optimisation. Increasing usage of aluminium and magnesium alloys in industries like automobile, aerospace, railway, shipbuilding and marine requires their fabrication. At the same time, aluminium and magnesium joining is challenging due to detrimental effect of hard and brittle intermetallic compound (IMC) (Mg17Al12 and Mg2Al3) formation. Addition of interlayer or filler of chosen composition limit formation of Al/Mg IMCs by controlling IMC dispersal and variety (retarding amount of Al/Mg IMC and preferentially forming other less brittle IMCs). Fast welding processes; limit energy input and reactivity time to avoid IMC formation. Controlled heat input; maintain lower processing temperature to avoid IMC formation. These three individually or in combination are possible ways to tackle the formation of Al/Mg IMCs. Dissimilar Al-Mg joining by methods like Gas Tungsten Arc Welding , Diffusion Bonding, Laser Welding and Laser Weld Bonding, Cold Metal Transferand Friction Stir Welding have been discussed in detail. The effects of modification implemented on the material response in terms of resultant joint properties, microstructure and metallurgical relations are emphasised. Furthermore, the future scope for dissimilar Al/Mg welding has been deliberated. [ABSTRACT FROM AUTHOR]

In the present study, a facile and economical gas tungsten arc welding (GTAW)-based WAAM approach was employed to fabricate a complex geometry by the filler wire of stainless steel (SS-304L) and subsequently covered with a hydrophobic dense and thick TiNNPs (Titanium nitride nano-pyramids) film. To analyze the mechanical properties of the printed alloy, room temperature tensile test and the microstructure reveal mostly homogeneous austenite as well as martensite phase. Comprehensive characterizations of the uncoated and coated samples were performed in terms of morphology, composition, structure, tensile test, and corrosion by FESEM, EDAX, XPS, XRD, and electrochemical work-station. The results indicated that the GTAW-fabricated sample (WSS-304L) led to a significant change in the surface properties, which can considerably enhance corrosion durability and corrosion resistance of TiNNPs coating, while maintaining their mechanical properties. The corrosion behavior of the bare and coated substrate was studied using potentio-dynamic polarization measurements in order to correlate water repellency with corrosion resistance; however, the coated sample demonstrated active corrosion without passivation. This method is commonly used in the protection of various materials from active corrosion. [ABSTRACT FROM AUTHOR]

The maraging steel is an impeccable choice for aerospace applications due to its high strength and excellent toughness. Welding is importantly involved in fabricating various structures out of maraging steel. Gas tungsten arc welding (GTAW) is the most commonly adopted technique for joining maraging steel. However, the major concern regarding the welding of maraging steel is the formation of the reverted austenite phase in the fusion zone and the heat affected zone. This reverted austenite deteriorates the mechanical property performance of welded joints. The present study focuses on GTAW of 12 mm thick MDN 250 maraging steel. An attempt was made to suppress the reverted austenite by employing suitable post-weld heat treatments. Three different types of post-weld heat treatments were adopted, i.e, (i) direct aging (W-DA), (ii) solutionizing + aging (W-SA), and (iii) homogenizing + solutionizing + aging (W-HSA). The micrograph and XRD analysis of the fusion zone with W-DA and W-SA conditions reveal the presence of reverted austenite. The SEM/EDAX examination of the fusion zone of as-welded, W-DA, and W-SA conditions revealed micro-segregation of Ni, Mo, and Ti elements from the matrix to the grain boundaries. On the other hand, the W-HSA condition was free from micro-segregation and austenite reversion. Electron backscatter diffraction (EBSD) analysis was used to estimate the percentage of reverted austenite in the fusion zone. The tensile test shows the highest strength of 1721 MPa (UTS) in W-HSA conditions. Similarly, the microhardness of the W-HSA conditions depicts a higher hardness with an even distribution in the microhardness values across the weldment. Hence, considering both metallurgical and mechanical examination of the weldment, the W-HSA heat treatments give superior properties in the case of GTA welded MDN 250 grade maraging steel. [ABSTRACT FROM AUTHOR]

This study focuses on the results of the welding process when the Taguchi method is added to the design of experimental welding parameters when creating the welding procedure for gas tungsten arc welding (GTAW) by ASME Code for duplex stainless steel (UNS31803). A Vickers hardness tester is employed to collect and convert the tensile strength data for each test piece (weld bead, base material, and heat-affected area). A ferritic rate meter can quickly determine the ferric contents, which affect corrosion resistance and susceptibility to cracking. The test data are entered into the Taguchi technique to analyze the influence of each component on the welding quality. The L9 (34) orthogonal table is used to design the parameters for the experiment. We fixed the same shielding gas and flow rate. Backing gas at root, workpiece clamping angle, heat input, and interlayer temperature are employed as control factors for the four essential variables of the GTAW process. The ideal set of quality analysis and optimization parameters can be found. The welding parameters could be used to improve the welding quality of thin and short duplex stainless steel pipe fittings during argon welding. [ABSTRACT FROM AUTHOR]

In supercritical thermal power plant units, a dissimilar joining of heat-resistant Cr-Mo steels such as P91 and P22 is commonly employed for components like boiler headers, piping, and steam turbine casing to increase the flexibility in design and application and also to reduce the material costs. However, a dissimilar joining of these two steels with matching filler has been subjected to several issues like mismatch in coefficient of thermal expansion, diffusion of elements, and unmixed zone formation. In the present investigation, microstructure and mechanical behavior study was conducted for the welded joint of different grade Cr-Mo steel, i.e., P22/P91 for the as-welded (AW) and post-weld heat treatment (PWHT) condition. The dissimilar welded joint (DWJ) was produced using the multi-pass gas tungsten arc welding (GTAW) process with Ni-based superalloy filler Inconel 82. Microstructure observation showed the absence of any type of possible cracking in the weldments obtained by Inconel 82 filler; however, an inhomogeneity in microstructure was found along the weldments. After the PWHT, carbon diffusion across the interface of P22 steel and Inconel 82 weld metal occurred, which resulted in the formation of soft zone (SZ) and hard zone (HZ). The welds produced using Inconel 82 filler displayed tensile strength and impact toughness of 608 ± 3.5 MPa and 83 ± 4 J, respectively. After PWHT, tensile strength and Charpy impact toughness were 507 ± 8 MPa and 75 ± 3 J, respectively. The fracture of tensile-tested specimen had occurred in the weak P22 base region for both AW and PWHT conditions, which ensured that welded joint was safe for supercritical power plant applications. The longitudinal residual stress of 380 MPa and transverse residual stress of 400 MPa were measured in top region of the weld metal, while in the root region, magnitude of 130 and 185 MPa was measured in longitudinal and transverse directions, respectively. [ABSTRACT FROM AUTHOR]

It is known that the conventional arc welding processes reduce the fatigue life of welded joints. However, in this work, a gas tungsten arc welding process with dynamic wire feeding (GTAW-DWF) at frequencies of 0.5, 5, 10 and 15 Hz improved the fatigue properties compared to the conventional process (C-GTAW) and the unwelded base material. The investigation was based on axial fatigue tests (R = 0.1) at room temperature, microhardness tests, microstructural analysis, secondary dendritic arm spacing (SDAS) measurements, scanning electron microscopy of fatigue fracture surfaces and Weibull distribution analysis. The mechanisms associated to dendritic morphology of fusion welds and solidification patterns were discussed. The SDAS values were (5 ± 0.8), (4 ± 1.0), (2 ± 0.3) and (4 ± 0.7) µm for the GTAW-DWF process with frequencies of 0.5, 5, 10 and 15 Hz, respectively, compared to (6 ± 1.4) µm of the conventional process. The GTAW-DWF lower SDAS and the absence of micro solidification defects were associated with the fatigue life improvement. The fatigue life for the GTAW-DWF with 1 Hz welded joints improved the fatigue life from 3288 to 115,356 cycles and from 12,027 to 522,143 cycles for maximum stress levels of 534 and 481 MPa, respectively, compared to the conventional GTAW process. [ABSTRACT FROM AUTHOR]

The 9% Cr steels were developed for ultra-supercritical (USC) power plants to meet the requirements of high operating temperature and pressure. These steels are produced to operate at high temperatures where impact toughness is not a concern; however, it becomes important for the welded joints to have good impact toughness at room temperature for manufacturing. The present work investigates the effect of the post-weld heat treatment (PWHT) parameters, i.e., temperature and time, on the impact toughness of multi-pass gas tungsten arc welded (GTAW) joints of ferritic/martensitic grade P92 steel. The microstructural evolution in welded joints given varying post-weld temperatures and times was studied. The lath martensitic structure of the weld metal for the as-welded joints resulted in high hardness and low impact toughness. The weld fusion zone toughness was 12 J, which was lower than the minimum specified values of 41 J (ASME standards) and 47 J (EN ISO 3580:2017). The PWHT temperature and time were found to have a significant effect on the impact toughness of the weld metal. A drastic increase in the impact toughness of the weld metal was noticed, which was attributed to lath break-up, reduction in dislocation density and reduction in solid solution hardening. The maximum impact toughness of 124 J was measured for PWHT temperature and time of 760 °C and 120 min, respectively. The effect of PWHT parameters on tensile strength was also investigated, and test results showed that the joint was safe for USC boiler application as it failed from the region of the P92 base metal. The variation in microstructural evolution along the weldments resulted in hardness variation. PWHT led to homogeneity in microstructure and, ultimately, reduction in hardness value. According to the study, the optimum temperature and time for PWHT of a GTAW joint of P92 steel were found to be 760 °C and 120 min, respectively. [ABSTRACT FROM AUTHOR]

Materials with a high strength-to-weight ratio are of particular interest to the manufacturing industry. This requirement can be met by using low-density aluminium alloy materials, such as the 7XXX series. The non-weldable material AA7075 was chosen for this study. We planned to weld AA7075 material with ER5183 filler material and use Gas Tungsten Arc Welding to make the weld. A welded specimen's Parent Material (PM), Heat Affected Zone (HAZ), Temperature Heat Affected Zone (THAZ), and Weld Zone (WZ) were microscopically examined and hardness measurements were taken. This study revealed that ER5183 filler material was used to weld non-weldable AA7075 material, and the problem occurred after welding. Due to the sudden water quenching after welding, the weld develops hotcracked defects. The air-cooled weld had a lower microhardness than the water-cooled weld. [ABSTRACT FROM AUTHOR]

In the present investigation, stability of weld morphology was investigated in case of electrolytic tough pitch copper (12 mm thickness) processed by Hot Wire Gas Tungsten Arc Welding (HW GTAW) using CuNi filler wire with variations of processing conditions, using different combination of hot wire's parameters such as feed rate and current. The assessment of weld bead geometry was performed using visual examination (during and after welding), and macrographic dimensional measurements of weld bead geometry such as depth of penetration and depth to width ratio. In addition to the stability of weld bead geometries, microstructural variations and weld quality assessments were studied using optical microscopy, scanning electron microscopy, energy dispersive x-ray spectroscopy, and micro-hardness measurements in case of processed sample observed with most uniform weld bead geometry. The results revealed that minimum dimensional variations of weld bead geometry throughout the processed length was obtained with 5.42 mm bead width, 1.2 mm bead height, 1.8 mm penetration, and 0.36 depth to width ratio when hot wire's parameters were 0.6 m/min wire feed rate and 90 amps hot wire current. The bridging mode of metal transfer helps to receive more stable weld bead geometry with minimum dimensional variations. Ni filler wire of HW GTAW improves the hardness in the Heat affected zone (70 HV0.3) and weld zone (80 HV0.3), which were 33% and 17% higher of base material. The weld zone was consisting of mixed mode of grains such as dendrites just above the fusion line and cellular grains further above dendrites in case of processed sample of minimum dimensional variations of weld bead geometry throughout the processed length. [ABSTRACT FROM AUTHOR]

Gas tungsten metal arc welding (GTAW) is used to study the effect of the base metal thickness, welding current and welding speed on the tensile strength and hardness of mild steel welding. The analysis found that base metal thickness had the highest effect and highest means of tensile strength and hardness of the welding. Taguchi's design (TD) suggested using higher base metal thickness, lower welding current and higher welding speed when welding mild steel in order to obtain maximum tensile strength and hardness. The welding that has higher tensile strength showed higher hardness. However, the hardness increased proportionally with the increased internal stresses of the welding. The welding showed wider heat affected zone (HAZ) with the increase in internal stresses of the welding. [ABSTRACT FROM AUTHOR]

In this study, three welding methods are used. The purpose to investigation the effects of SMAW, SAW, and gas tungsten arc welding (GTAW) on the tensile stress of low carbon steel conforming to ASTM 283 c. 8mm thick plates are used as base material for butt welded joints. The tensile properties of the welded joints were evaluated and the results were compared by experts using the Taguchi method to design three levels of each parameter (current, voltage and displacement speed). From this research, it is found that compared to metal shielded arc welding and submerged arc welding, the pulling effect of the gas shielded welding joint of the tungsten electrode is the best. This is mainly due to the presence of The results of using analysis of variance (ANOVA) to estimate important parameters show that welding current and speed of the weld have a significant effect on tensile stress .the experimental results are in agreement with predicted results, and the maximum error is 3%. [ABSTRACT FROM AUTHOR]

Duplex stainless steel (DSS) is an important material used for corrosion resistance in various harsh environment plants such as petrochemical, offshore subsea component, and other chemical industries. An approximately equal amount of austenite and ferrite (A/F) ratio grants good mechanical properties and rust protection on. The detrimental intermetallic phase frequently occurs due to an unbalanced A/F ratio caused by the welding’s thermal cycle. Backing gas is commonly applicable in the field combined Gas Tungsten Arc Welding (GTAW) process. However, the use of backing gas to complete a single weld from root to cap joint required huge additional costs for consumables. Maintaining the thermal cycle in the welding parameter and GTAW process with ER2209 filler metal for DSS below 10 mm thick can reduce the backing gas sequence. The research aims to efficiently substitute full backing gas consumption, which meets a desirable quality in terms of corrosion resistance. The effect of backing gas reduction was studied. All specimens were tested by visua Vickers microhardness, metallography, ferrite content measurement, and electrochemical corrosion test. The visual test shows no defects beyond the range of the ASME IX acceptance and criteria. The evaluation comes from the ferrite scope and electrochemical corrosion test. The backing gas on the root weld shows a balance A/F ratio of around 38% ferrite content accepted in various standards. The backing gas sequence on the root until filler-pass obtained 0.04 mm/year, which is the desirable corrosion resistance and met the requirement of ASTM A932. [ABSTRACT FROM AUTHOR]

Automatic gas tungsten arc welding experiments of 5083 aluminum alloy were completed, to analyze the weld microstructure and mechanical properties. The influences of welding current, travel speed, frequency, and arc length on weld forming and mechanical properties were studied. When the welding current was 160 A, the travel speed was 380 mm/min, the frequency was 100 Hz, the arc length was 4 mm, and the maximum tensile strength of the welded joint was 296.9 MPa, which was 86.8% of the base metal's tensile strength. The fracture elongation was 7.8%. No porosity was formed in the weld, but there were poor fusion problems. ER5356 welding wire can improve the problem of poor weld fusion and accommodate Mg element vaporization losses. When the wire feeding speed was 1200 mm/min, the tensile strength of the welded joint can be improved to 315.2 MPa, which was 92.2% of the base material's tensile strength, and the fracture elongation was 8.5%. The tensile specimens fractured in the heat-affected zone. The fracture surface was characterized as plastic fracture. [ABSTRACT FROM AUTHOR]

Nickel base hardfacing alloys serve to mitigate corrosion losses at elevated temperatures. Efficacy of Nickel base hardfacing alloys can be compromised when applied onto Fe base substrates due to iron dilution in hardfacing. The degree of Fe dilution can be reduced by using advanced deposition methods and optimized deposition parameters. Gas Tungsten Arc Welding (GTAW) method is commonly employed for its cost-effectiveness and versatility, but it tends to induce higher Fe dilution due to increased heat input. This study aims to reduce the degree of Fe dilution and enhance corrosion resistance by introducing a nickel base buffer layer (alloy 625) between the nickel base hardfacing alloy and AISI 316L stainless steel substrate. For comparative purposes, Ni base hardfacing alloy was deposited on the substrate without any buffer layer. Hardfacing depositions were prepared using manual GTAW process. Process parameters namely, deposition current, voltage, travelling speed, pre-heating temperature, and cooling method were kept constant. Samples underwent aging at 1123 K for 4 h, followed by microstructural examination via optical and scanning electron microscopes. Iron (Fe) dilution quantification was performed using energy dispersive spectroscopy (EDS). The EDS analysis showed that the use of buffer layer between the hardfaced deposit and the substrate decreased the degree of Fe dilution in the hardfaced deposit. X-Ray diffraction (XRD) analysis was performed to identify various phases formed in the hardfaced deposit. Potentiodynamic polarization test was performed to assess the corrosion resistance of hardfaced deposit in 3.5 wt% NaCl solution. Results show significant improvement in corrosion resistance of hardfacings deposited sample with buffer layer as compared to those without buffer layer. Aging treatment further enhanced corrosion resistance. The corrosion resistance data is correlated with the microstructure and phases formed in various samples. [Display omitted] • The impact of buffer layer on hardness, microstructure, Fe dilution, and corrosion resistance in Ni-based hardfacing using the GTAW method. • Higher Ni concentration in the hardfacing deposition reduces Fe dilution, improving the Ni/Fe ratio in Ni-based hardfacing. • Presence of Mo and Nb in the hardfacing refine microstructure and improve corrosion resistance. • Solidification analysis performed to assess the impact of Mo and Nb addition using phase and Scheil diagrams. [ABSTRACT FROM AUTHOR]

The application of the novel dissimilar metal welded (DMW) joint, utilizing Inconel 617 and P92 steel, was showcased in the advanced ultra-supercritical (AUSC) boiler. The work has been performed to investigate the effect of Inconel 82 (ERNiCr-3) buttering layer on microstructure and mechanical properties (high-temperature tensile strength, impact strength and microhardness) of gas tungsten arc welded (GTAW) dissimilar joint between Inconel 617 and P92 steel fabricated using the Inconel 617 (ERNiCrCoMo-1) filler. For optical microscopy and scanning electron microscopy (SEM), samples were machined along a transverse direction which comprised the butter layer, weld metal, and heat-affected zone of both sides. The energy-dispersive X-ray spectroscopy (EDS) was used to map the interface of the buttering layer and weld metal and butter layer and P92 steel. The high-temperature tensile testing and Charpy impact testing at room temperature were conducted for the integrity assessment of the welded joint. The examination of microstructure and hardness revealed that the buttering layer of Inconel 82 filler successfully mitigated a significant portion of the brittle martensitic microstructure from the coarse-grained heat-affected zone (CGHAZ), along with hardness peaks on the side of P92 steel. The conventional method of DMW joint fabrication, without the use of a buttering layer, has been demonstrated to be less favourable compared to the new fabrication method, which incorporates a buttering layer. The TiC/NbC carbides were identified in the Inconel 82 buttering layer, whereas M 23 C 6 and Mo 6 C carbides were found in the Inconel 617 filler weld. Near the interface of the Inconel 82 buttering layer and P92 steel, the formation of peninsula and island structures, as well as Type I and Type II boundaries, were confirmed. Additionally, element diffusion of Ni, Cr, and Fe was observed. The tensile test results indicated an ultimate tensile strength of 620 ± 4 MPa and % elongation of 19 ± 4 % at room temperature, with fracture occurring in the buttering layer near the interface of the buttering layer and P92 steel. At temperatures of 550 °C and 650 °C, the ultimate tensile strength decreased to 448 MPa and 326 MPa, respectively, with fractures occurring in the P92 steel, irrespective of temperature. The hardness of the Inconel 82 buttering layer and Inconel 617 filler weld were 219 ± 10 HV and 248 ± 11 HV, respectively. The Charpy impact toughness of the Inconel 82 buttering layer and Inconel 617 filler weld were 138 ± 6 J and 115 ± 4 J, respectively. The study comprehensively investigates and discussed the correlations between microstructure and mechanical properties. • A dissimilar welded joint of buttered P92 steel and Alloy 617 was fabricated using the GTAW process. • The structural integrity of the welded joint was tested using high temperature tensile tests, hardness tests and Charpy impact tests. • A detailed investigation of the dissimilar weldments was performed using the SEM/EDS and optical microscopy. • A relation between microstructure and mechanical properties was investigated. [ABSTRACT FROM AUTHOR]

This study investigates the effect of filler materials on the structural integrity of dissimilar welded joints (sDSS 2507/IN625) employed in marine subsea manifold applications. Multi-pass gas tungsten arc welding (GTAW) using ER2594 and ERNiCrMo-3 fillers investigates microstructure evolution, solidification mechanisms, mechanical characteristics, residual stresses, and corrosion behavior. Optical and scanning electron microscopy revealed an unmixed zone (peninsula/island-shaped) at the weld interface and weld zone (WZ) in both filler weldments. Segregation of Mo, Nb, and Ni was observed in the interdendritic region of ERNiCrMo-3 filler WZ, whereas the skeletal ferrite matrix of ER2594 filler WZ revealed the existence of the Laves phase (Fe 2 Nb form). Electron beam scattered diffraction (EBSD) investigation showed austenitic solidification for ERNiCrMo-3 and fully ferritic solidification for ER2594 with distinct dendrite formations. Inhomogeneity has been observed in microhardness maps, with ER2594 and ERNiCrMo-3 WZ averaging 310 ± 7 Hv 0.5 and 270 ± 10 Hv 0.5 , respectively. ERNiCrMo-3 (165 ± 5 J and 180 ± 3 J) and ER2594 (100 ± 3 J and 110 ± 6 J) fillers exhibited distinct effects on toughness in the weld cap and root due to laves phase precipitation. Additionally, ER2594 (750 ± 6 MPa) and ERNiCrMo-3 (790 ± 7 MPa) fillers exhibited lower tensile strength than base metals. The structural integrity of WZ can be better understood by residual stress analysis, which showed compressive cap pass and tensile root pass residual stresses for both fillers. In a 3.5 wt% NaCl solution, both fillers exhibited outstanding corrosion resistance in marine conditions. These findings improve subsea manifold structure integrity and performance in corrosive marine environments. [Display omitted] • Multi-pass GTAW of sDSS 2507/IN625 DWJs with ER2594 and ERNiCrMo-3 fillers. • ER2594 exhibits ferritic solidification; ERNiCrMo-3, austenitic with Laves phase. • ERNiCrMo-3 welds demonstrate higher impact toughness and better corrosion resistance. • ERNiCrMo-3 exhibits higher compressive stresses, impacting weld integrity. [ABSTRACT FROM AUTHOR]

Inconel 825, a Ni–Fe–Cr alloy highly regarded for its exceptional corrosion resistance and high-temperature strength. This investigation studies the effect of heat input, precipitation, and micro segregation of Inconel 825 weldments and compares the effectiveness of two welding techniques: gas tungsten arc welding (GTAW) and electron beam welding (EBW). The findings indicate that increasing heat input generally enhances weldment quality by reducing the lack of penetration. However excessive heat input in GTAW leads to root cracking and solidification cracking; while EBW demonstrates better control over undercut and maintains consistent weld quality even at higher heat inputs. Both GTAW and EBW samples exhibit dendritic grain morphologies with distinctive grain boundaries. Precipitates, such as Al 4 C 3 and TiN, are observed in both processes, contributing to improved mechanical properties. While GTAW weldments show some degree of segregation for Mo, Cu, Ti, and Al, EBW weldments demonstrate negligible segregation for major alloying elements but micro-segregation of Ti and Al. EBW weldments additionally showcase higher average hardness, superior tensile strength, and ductility compared to GTAW weldments. This can be attributed to lower heat input, faster cooling rates, and a reduced rate of elemental segregation. Fractographic analysis reveals the presence of voids and micro-voids, indicating a ductile mode of failure for both GTAW and EBW samples. These void characteristics vary based on the heat input and microstructural features. [Display omitted] • Effects heat input, precipitation, and micro-segregation using GTAW and EBW on Inconel 825 was studied. • Higher GTAW heat input improves quality but risks cracking; EBW ensures consistent quality at higher heat input. • In both GTAW and EBW weldments, observed precipitates enhance mechanical properties. • GTAW weldments shows Mo, Cu, Ti, and Al segregation; EBW has minor elemental segregation of Ti and Al. • Comprehensive evaluation reveals superior EBW performance over GTAW in Inconel 825 weldments. [ABSTRACT FROM AUTHOR]

Pipes (rigid risers and flowlines) are employed to transport oil and gas from the wells to the platforms. In these pipes, the fluids can be very corrosive and, therefore, corrosion-resistant alloys (CRA) must be chosen. Alloy 625 is a well-known CRA with improved corrosion resistance. However, nickel-based alloys have high cost compared to that of the low alloy steels, thus pipes entirely made of CRA are economically unfeasible. Internal coating with a thin CRA layer is a less expensive and suitable alternative than the solid CRA. An internal coating by overlay manufacturing process can induce phase transformations at the interface. In this work, an alloy 625 cladding layer was deposited in an API X65 steel substrate with an automatic weld overlay system using gas tungsten arc welding (GTAW) process (often referred to as tungsten inert gas (TIG) hotwire). Thus, this study aims at evaluating an API X65 steel pipe cladded with alloy 625. The results show a suitable nickel-based alloy overlay deposited in an API X65 carbon steel substrate. [ABSTRACT FROM AUTHOR]

Keyhole gas tungsten arc welding (K-GTAW) was applied to characterize the weld bead geometry in case of the 6 mm thick electrolytic tough pitch copper. Various conditions of welding speeds and preheating on the bead geometry were studied for its uniformity. Visual examination, macro bead dimensional analysis, microhardness profile across the transverse section, microstructural analyses were performed to investigate the K-GTAW on electrolytic tough pitch copper. The results revealed that full penetration of 6 mm can be obtained in a single pass using keyhole mode in GTAW. Keyhole length and width were majorly affected by the welding speed and preheating temperature. Significant variations in weld bead geometry were observed even when high heat input conditions were applied without preheating. Uniform weld bead geometry of 5 mm bead width and depth to width ratio of 0.42 was obtained for a length of 80 mm using appropriate preheating of 300°C and heat input condition of 1.37 kJ/mm (resulted from 300 amperes welding current, 120 mm/min welding speed, and 15.3 volts voltage). In the uniform weld bead geometry, the weld and heat affected zones were consisted of coarse grains relative to base material, wherein the micro hardness variations were observed. [ABSTRACT FROM AUTHOR]

Hybrid laser-arc welding (HLAW) is regarded as a promising joining process, since it can compensate disadvantages from laser autogenous welding and arc welding by uniting both techniques into a single melt pool. Such a process can achieve relative high quality metallurgical bonding, high speed, and low deformation. However, the process is considered complex and of difficult parametrization, as the four states of matter come to coexist in the same space and as the union of two processes generates interactions that are still not well understood [C. Churiaque, M. Chludzinski, M. Porrua-Lara, A. Dominguez-Abecia, F. Abad-Fraga, and J. Maria Sánchez-Amaya, "Laser hybrid welding of large thickness naval steel," Metals J. 9, 100 (2019); G. Casalino, Hybrid Laser Welding: A Review, DAAAM International Scientific Book (DAAAM International, Vienna, 2010), Chap. 38, pp. 413–430; and B. Ribic, T. A. Palmer, and T. DebRoy, "Problems and issues in laser-arc hybrid welding," Int. Mater. Rev. 54, 223–244 (2009)]. One of HLAW's main variations is studied and evaluated in this work, the hybrid laser-Tungsten Inert Gas (TIG) welding process. In this process, the interaction between the arc and the laser-induced plume is dependent on the shielding gas flow, arc welding current and voltage, laser beam characteristics, and the geometric relations between electrode, laser incidence position, and workpiece. Here, in order to further analyze the influence of the laser power on arc behavior during the hybrid process, tests were performed by varying the TIG current and laser power parameters from 60 to 100 A with increments of 20 A and 0 to 2500 W with increments of 500 W, respectively. From an arc's voltage monitoring, one can analyze the influence of the interaction between the arc's plasma and the plume induced by the laser. It was observed that the perturbation generated by the laser beam is directly proportional to its power, as there is an increase in the average voltage and the perturbance amplitude as a function of the applied laser power. The analysis presented over the dynamic aspect of the hybrid welding process and the influence of the laser beam on the arc contribute to the laser-TIG welding consolidation within the academic and industrial scenario. [ABSTRACT FROM AUTHOR]

Although different forms of renewable energy sources are in expansion, the oil and natural gas industry remains essential, maintaining its demand for more efficient methods for product transportation. The most productive and safe way is the flow through pipelines. However, pipeline usage directly involves several wear mechanisms, which contribute to pipeline degradation and, consequently, the need for repairs and maintenance shutdowns, implying in heavy financial impact in the entire industrial chain of supply. An economical and feasible solution to mitigate wear is to protect equipment with metallic coatings. Through this technique, engineers can keep the more noble—and expensive—metals only in regions where their chemical and mechanics proprieties are needed. Various processes may be industrially used for coating, presenting different levels of productivity, quality, and required investment. Among the arc welding processes, the most used for coating applications against wear and corrosion is the tungsten inert gas (TIG) process. The laser coating process, or laser metal deposition (LMD), a process concurrent to TIG, can apply such coatings with high precision and reproducibility, minimizing dilution, distortions, lack of fusion, and the formation of a large heat affected zones; however, results may vary. The present work evaluates two dilution-equivalent Inconel 625 coatings through rubber disk tribological testing, microhardness measurements, and worn surface analysis by scanning electron microscopy via energy dispersive x-ray analysis. Each coating was manufactured by one of the mentioned processes, LMD or TIG, with three replicates of each process to observe its repeatability. For the laser manufactured coating, microhardness values averaged to 247 HV, while TIG's average stayed at 218 HV. Volumetric loss due to wear testing behaved differently, with higher values about 16.3% more for TIG when compared to laser coating. The differences between microhardness values and volume losses are explained by crossing information from each coating's cross-section microscopy and worn surface, as well as each process parameterization and nature. In conclusion, LMD coating presented itself as the more efficient process; such a result, in parallel with the continuous advance in laser sources technology, makes a significant contribution to LMD consolidation as the pipeline coating process and a case study with a tribological comparison between two frequently applied processes. [ABSTRACT FROM AUTHOR]

This paper is aimed to study in detail about dissimilar welding of aluminium alloy (AA 1100) with mild steel (MS) of thicknesses 3.0mm and 2.0mm respectively. This paper also gives emphasis on the multi-objective optimization by using grey relational analysis (GRA) for samples welded with gas tungsten arc welding (GTAW). The welding input parameters are crucial in obtaining the desired weld quality. The experiments have been performed according to the L-8 orthogonal array. The input parameters chosen are the pulsed DC parameters such as pulsed current, base current, pulse on time percentage and frequency. The weld quality determining parameters are the ultimate tensile strength and Rockwell hardness. Grey relational analysis is used to obtain the optimum input values for the optimum weld quality. [ABSTRACT FROM AUTHOR]

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In this research work, a finite element (FE) numerical analysis was conducted to study the welding thermal field. The finite element model (FEM) was improved by means of the optimal mesh element size using statistical analysis of a design of experiment (DoE) based on the Taguchi method. Through the improved FEM, numerical model were carried out estimations of the penetration depth, heat dissipation phenomenon, and thermal energy input. Then, FE numerical results were linked to Matlab®. The FEM-Matlab® approach proposed the application of thermal energy predictions to estimate welding critical zones extensions and their possible non-metallic inclusions. The FEM-MATLAB® approach was applied to a case study: twinning-induced plasticity steel microalloyed with titanium (TWIP-Ti) weldments. Welding experiments were performed with the autogenous Gas Tungsten Arc Welding (GTAW) process in 6.3-mm thickness plates. The weld samples were analyzed metallographically to measure welding critical regions extensions. Both austenitic grain size and non-metallic inclusions were in good agreement with numerical results. The weld bead obtained by means of the optimal process parameters estimated by the FEM-Matlab® approach achieved full penetration and showed better microstructural characteristics according to the numerical estimation. [ABSTRACT FROM AUTHOR]

Gas tungsten arc welding (GTAW), a widely used industrial process, is one of the most intense artificial sources of optical radiation. This paper presents a theoretical investigation of the UV (180–400 nm), UVA (315–400 nm) and blue light (300–700 nm) radiation associated with the photobiological hazards to workers for argon GTAW arcs. The radiative properties of argon plasma were calculated and discussed for the three spectral regions of interest at temperatures from 5000–25,000 K and atmospheric pressure. A two-dimensional model of a GTAW arc was then developed to determine the local emissions in the arc, the total radiation escaping from the arc and corresponding effective irradiances. This model is also used to study the influence of the welding parameters (current intensity and arc length) on the radiative properties and the effective irradiances. The permissible exposure durations for skin and eyes were further evaluated according to the radiation exposure standard of the Directive 2006/25/EC for the three spectral intervals. It is found that the UV radiation is most hazardous among these spectra. Indeed, it is shown that the UV permissible exposure duration is very short, e.g. from 5.89 s to 9.8 min at the distances from 0.5 m to 5 m for a typical GTAW arc (200 A and 5 mm arc length). This study clearly supports the importance of undertaking an effective protection strategy for workers, particularly for skin and eyes, in the welding environment. [ABSTRACT FROM AUTHOR]