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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]

Duplex alloys have excellent mechanical properties, as well as resistance to corrosion, but when they are welded, they present a segregation process of the alloying elements that must be controlled by the electrical welding parameters. In this work, an optimisation study is carried out on the electrical parameters for top welding two 3-mm thick flat profiles, where the smallest optimal thermal input is to be obtained. Welding is carried out with an ABB welding robot. The electrical parameters that can be controlled are the intensity and the forward speed; the rest of the electrical variables are regulated by the robot's control cell. The Taguchi optimisation consists of an L4 matrix of two factors taken in pairs and the objective is to minimise the thermal input, as well as the geometry of the weld bead. In addition, experimental validation tests of the Taguchi model are carried out. The S32205 duplex alloy is a little-known alloy used in welding with the GTAW process and this is the main reason for its selection in this study. The influence of each of the welding variables on the geometry of the welded joint is evaluated as a percentage. [ABSTRACT FROM AUTHOR]

This study investigates the corrosion behavior of dissimilar gas tungsten arc (GTA) welded joints between super duplex stainless steel (sDSS 2507) and pipeline steel (X-70) using electrochemical and immersion corrosion tests. The GTA welds were fabricated using ER2594 and ER309L filler metals. The study examined the electrochemical characteristics and continuous corrosion behavior of samples extracted from various zones of the weldments in a 3.5 wt.% NaCl solution, employing electrochemical impedance spectroscopy, potentiodynamic polarization methods, and an immersion corrosion test. EIS and immersion investigations revealed pitting corrosion in the X-70 base metal/X-70 heat-affected zone, indicating inferior overall corrosion resistance due to galvanic coupling. The corrosion byproducts identified in complete immersion comprised α-FeOOH, γ-FeOOH, Fe3O4, and Fe2O3, whereas γ-FeOOH and Fe3O4 were predominant in dry/wet cyclic conditions. Corrosion escalated with dry/wet cycle conditions while maintaining a lower level in complete immersion. The corrosion mechanism involves three wet surface stages in dry/wet cycles and typical oxygen absorption during complete immersion. Proposed corrosion models highlight the influence of Cl−, O2, and rust layers. [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]

The effect of three levels of welding arc energy input on the metallurgical, mechanical, and corrosion behavior of AISI 304L stainless steel was studied with the aim of investigating and recommending the most useful range of process parameters for improved performance of engineering structures made from this industrially important alloy. The gas tungsten arc welding process was employed, and all the joints were butt-welded using a single-V groove design. With an increase in heat input, the δ-ferrite phase changed from lathy to vermicular, besides the heat-affected zones of all the welds exhibiting grain coarsening effects. Postweld thermal aging led to the preferential occurrence of carbides in the interdendritic regions, which degraded their corrosion performance. Thermal aging did not affect the tensile strength of these welds, but their ductility was significantly impacted. The extent of segregation of Cr and C, especially, was observed to be the least in the case of low heat input welds. This study establishes that while designing welding procedures for AISI 304L structures, low welding arc energy should be used as it promotes better mechanical as well as corrosion properties. [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]

ZW61 magnesium alloy has a wide range of application prospects as a lightweight green engineering material. In this paper, the temperature field and microstructure of gas tungsten arc welding (GTAW) for ZW61 magnesium alloy are simulated by the finite element method and the cellular automata (CA) method. The results show that the microstructure in the center of the fusion zone (FZ) is all equiaxed grains affected by compositional supercooling. While at the edge of the molten pool, the crystals produced by associative crystallization evolve into columnar grains after undergoing competitive growth. Furthermore, the temperature field of the molten pool alters as the welding heat input increases. Especially, the temperature gradient behind the molten pool slows down. Thus, the cooling rate during solidification of the molten pool decreases, increasing the size of the weld microstructure. Meanwhile, solute concentration plays an essential role in the weld microstructure evolution. The rise in Zn content both refines the size of the equiaxed grains and inhibits the growth of the columnar crystals. Moreover, the experimental results of the thermal cycling curves and the FZ microstructure exhibit minimal error with the simulation results, verifying the reliability of the model.

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]

New systems and methods to access the temperature of the melt pool in welding processes have been developed to study phenomena, monitor behaviours, and even be used in closed-loop control strategies. Concerning arc welding processes, the arc radiation might impose a challenge to measure the temperature. However, heat input is the key point for welding quality. This work aims to evaluate the feasibility and detect potentialities of accessing the thermal field from the rear weld pool in the GTAW process by using in-house developed equipment. The original system was conceptualized based on a previous bichromatic method. Experiments were carried out with and without the wire feed addition, and welding parameters were varied to explore its impacts on the temperature measurement. A strategy to select the regions of interest (ROIs) within the weld pool was created, and the mean temperature was calculated and correlated to the weld bead features. This strategy was able to overcome the challenges imposed by the electrode/nozzle reflection and the arc radiation during the welding. The rear weld pool thermal field was shown to be an important source of data to provide hints of the weld bead features. The mean temperature can indicate geometrical changes in the weld bead. Furthermore, the technique has the potential to be used as a promising real-time process monitoring tool. [ABSTRACT FROM AUTHOR]

Gas tungsten arc welding employs the Taguchi method to reduce thermal distortions in the welded structures which are used in many industrial applications including marine, offshore, petrochemical and automobile sectors. Using a vernier height gauge, we calculated the amount of transverse deformation caused by the GTA welding procedure. An L8 orthogonal array is used with the welding current, weld root gap, gas flow rate, and welding speed as the critical parameters for four noise sources. Finding the average, standard deviation, and solution effectiveness are the three main goals of the Analysis of Variance. According to the results of these analyses, weld distortion may be significantly influenced by weld parameters. Lower thermal strain values were observed when higher welding current and gas flow rate is maintained. The optimal degree of distortion is believed to be two degrees. Controlling welding speed and root gap resulted in a 37% contribution with a 90% confidence on distortion, indicating that these parameters are crucial to producing a reliable design. [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]

Gas Tungsten Arc (GTA) welding employs to reduce the welding cost and produces the quality of the joint at the required positions. In this study, multipass GTA welding of SS316L was simulated, and experiments investigated its impacts on thermal analysis. An accurate and physically suitable heat flux simulation model is to be given as input for the analysis of welding processes. The transient thermal analysis was modeled using ANSYS with relevant APDL coding using Double Ellipsoidal moving heat flux models, providing boundary conditions. The temperatures of weldments were measured in real-time using infrared thermography and validated with simulation using ANSYS. Temperature readings were obtained from the analysis and the experiment, and the degree of agreement is less than 1%. [ABSTRACT FROM AUTHOR]

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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.

Aircraft applications make use of Ti–6Al–4V alloy for almost 50% of all alloys used in aerospace industry. Besides this, owing to their high tensile strength to density ratio, high corrosion resistance, and ability to withstand moderately high temperatures without creeping, titanium alloys are used in armor plating, naval ships, spacecraft, and missiles. Aircraft engines and frames are frequently fabricated using welding technology which often involves multiple passes that has direct impact on metallurgical properties of these alloys. In view of the weldability issues of this industrially important alloy, the aim of the present work was to investigate the effect of weld pass on the metallurgical properties of 7-mm-thick Ti–6Al–4V alloy. Ti–6Al–4V weld joints in the butt-welding position were fabricated using 3-pass and 4-pass welding procedure using gas tungsten arc (GTA) welding process in the manual mode. The results of this work show that Ti–6Al–4V alloy is sensitive to welding heat input variation that occurs due to weld pass procedural effects. Further, welding procedures can be designed according to the microstructural and hence mechanical requirements of Ti–6Al–4V alloy by controlling heat input per weld pass suitably. [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 this work, magnetic field-assisted autogenous gas tungsten arc welding (GTAW) of low carbon steel has been studied. The external magnetic field was generated by custom made rectangular shaped samarium cobalt permanent magnets which were arranged in a manner to generate a cusp-type magnetic field (CMF). The impact of CMF on the morphology and microstructural evaluation of the weld joints were examined prudently using optical microscope, Field-emission scanning electron microscope and X-Ray Diffraction technique. The experimental results exhibited that the CMF assisted GTAW produce joints with better mechanical and metallurgical properties compared to conventional GTAW. In CMF assisted welds, width of weld beads was reduced by an average of 4% and depth of penetration was increased by 13%. Temperature measurement on the work piece showed a significant amount of temperature decrease for the same amount of heat input under the influence of the CMF. An improvement in grain refinement was observed in the heat-affected zone (HAZ) adjacent to fusion boundary by 12% and HAZ adjacent to base metal by 15% compared to conventional GTAW, which in turn promoted a considerable increase in hardness. The tensile properties in CMF assisted welds were enhanced by 3% and 8%, respectively, for an increase of heat inputs from 0.34 to 0.45 kJ mm−1. [ABSTRACT FROM AUTHOR]

Unfavourable operating conditions of equipment in the energy industry resulting from high-temperature loads determine the need to use special materials and technological solutions, including welding procedures. In this article, buttering using IN82 (ERNiCr-3) consumables was proposed as a method to improve the weldability of grade 92 steel joined by the gas tungsten arc welding (GTAW) process with AISI 304L (IN617 filler). The microstructural characterization of samples was carried out using an optical microscope, scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy. The welded joint was further characterized by hardness, tensile (room temperature and at 620 °C temperature) and impact tests. Additionally, the fracture surfaces of tensile and impact tests were studied by SEM. Despite the confirmation of the diffusion of alloying elements and significant changes in their concentration, which indicates the formation of Ti and Nb-rich phases, no welding imperfections were detected and favourable joint structures and acceptable properties were obtained. In particular, this concerns the limitation of the formation of brittle structures and the elimination of the untempered martensitic layer. At the same time, there was a significant decrease in the maximum hardness of heat-affected zone (HAZ) on the grade 92 steel side to a relatively low value of 310 HV, and a minimum tensile strength criterion of 600 MPa was achieved with a simultaneous increase in ductility (35% elongation) of the joint. Comparatively, when compared to a non-buttered welded joint, the joint produced with a buttering layer exhibited an increase in the elongation and impact toughness of the welded joint without any compromise in ultimate tensile strength (Sut). The fracture surface of tensile and impact-tested specimens was also characterized using SEM/EDS. Summarizing all the results, it can be concluded that the proposed GTAW procedure of grade 92 and 304L steels can be used in extreme working conditions, in ultra-supercritical power units or the petrochemical and chemical industries. [ABSTRACT FROM AUTHOR]

In this research, dissimilar metals of AA 6082 and AA 7075 are joined using Gas Tungsten Arc Welding (GTAW) process with ER4043 filler wire. The welding conditions and their range are identified for producing quality welding characteristics. Taguchi based techniques are adopted for design of experimentation and analyzing factors involved in welding characteristics. L-9 Orthogonal Array (OA) was used for Design of Experiments (DOE). Welding current, filler diameter and root gaps are selected as input parameters. The welded structure defects were inspected with X-ray radiography images as well as macrostructures. The response factors such as Ultimate Tensile Strength (UTS), % of elongation, hardness and impact strength were considered and evaluated by conducting mechanical tests. Analysis of Variance (ANOVA) is conducted to study the influence of parameters on responses. The tensile strength of sample 5 is increased by 53.37% when compared with the sample 6 due to the lower heat input rates. The welding speed (68%) has most influence parameter followed by welding current (14%) and filler diameter (14%). The dissimilar combination of aforementioned joints have wide range of application including aerospace, defense, and military sectors. [ABSTRACT FROM AUTHOR]

This study investigates the effect of a tungsten carbide-nickel coating on the wear resistance of plain carbon steel. The primary phases identified in the coating were Fe3W3C, Fe4W2C, and a eutectic structure containing Fe3W3C and (Fe–Ni)-α. Wear behavior was evaluated through a friction coefficient test and Scanning Electron Microscopy (SEM) analysis. The coated samples exhibited a significantly lower friction coefficient compared to the uncoated sample, indicating superior wear resistance. This improvement is attributed to the presence of a network of (Fe, W)3C carbides and the strong interfacial bonding between the coating and substrate. Coated surfaces displayed parallel scratches and small wear particles, indicative of a scratch-type wear mechanism. Microhardness measurements revealed a distinct profile across the coating thickness. The high hardness near the surface is attributed to the presence of simple carbides. Hardness increased further in the center of the coating due to optimized welding parameters. Hardness decreased towards the interface with the substrate due to a decrease in alloying elements and a shift towards complex carbides.

Recently, a novel Ni–Cr–Co-based superalloy has been developed in China, exhibiting exceptional overall characteristics such as favorable mechanical properties at 800 °C, resistance to corrosion and oxidation, as well as remarkable welding capabilities. In this paper, the welding sample of the novel superalloy was prepared using the gas tungsten arc welding (GTAW) method. The conclusion indicates that the GTAW technique can be utilized to fabricate high-quality weld joints filled with superalloy wire. A segregation phenomenon exists between the core and boundary of the dendrite in the fusion zone. The interface of the joints is effectively fused without any separate area. There is an abundance of co-crystallization occurring between the weld metal and the base metal. Besides, the joint has been tested at room temperature (20 °C) and high temperature (800 °C) for its ultimate tensile strength (UTS). The UTS of the joint is 11780 MPa and 781Mpa at 20 °C and 800 °C, respectively. Moreover, the positions of the fractures in the two cases are different. At 20 °C, the fracture location is in the base metal, while at 800 °C, the fracture location is inside the fusion zone. The SEM analysis of the fracture indicates that at 20 °C, the joint's tensile fracture surface exhibits transparent mixed fracture mode, and there are numerous small dimples; at 800 °C, the dimple on the fracture surface of the joint disappeared, replaced by the feature of smooth fracture along the dendrites.

New systems and methods to access the temperature of the melt pool in welding processes have been developed to study phenomena, monitor behaviours, and even be used in closed-loop control strategies. Concerning arc welding processes, the arc radiation might impose a challenge to measure the temperature. However, heat input is the key point for welding quality. This work aims to evaluate the feasibility and detect potentialities of accessing the thermal field from the rear weld pool in the GTAW process by using in-house developed equipment. The original system was conceptualized based on a previous bichromatic method. Experiments were carried out with and without the wire feed addition, and welding parameters were varied to explore its impacts on the temperature measurement. A strategy to select the regions of interest (ROIs) within the weld pool was created, and the mean temperature was calculated and correlated to the weld bead features. This strategy was able to overcome the challenges imposed by the electrode/nozzle reflection and the arc radiation during the welding. The rear weld pool thermal field was shown to be an important source of data to provide hints of the weld bead features. The mean temperature can indicate geometrical changes in the weld bead. Furthermore, the technique has the potential to be used as a promising real-time process monitoring tool.

Al6013 base metals were joined successfully with ER4047 weld metal by using the GTAW method under different welding currents. Post-weld T6 heat treatment effects on corrosion properties were investigated in terms of open circuit potential (OCP), potentiodynamic polarization (PDS), and electrochemical impedance spectroscopy (EIS) tests. It was determined that corrosion resistance of the post-weld samples increased with increasing welding current, while T6 heat-treatment only effective on 110A and 140A welding current samples (3.61 to 2.08, 2.95 to 2.40, and 1.38 to 2.15 µA·cm-2 for 110, 140, and 170A welding current before and after T6 heat-treatment). The characteristics of the oxide films on the surfaces are revealed with EIS analysis by a two-constant equivalent circuit model which observed that while the passive film originating from Al is formed on the surfaces, on the other hand, it contains a pittings on the surface. It was determined that the pitting resistance of the T6 heat-treated 110A samples increased (3075 to 4562 Ω). Post-corrosion SEM surface morphologies showed that low welding currents lead to more damage with increased exposure to corrosion.

A multiple gas tungsten arc welding was performed on the fabrication of the Fe–Cr–Ni-based weld metal. Microstructures and hot corrosion behaviors of the non-equilibrium weld metals with different Nb contents in 75 wt%Na2SO4–25 wt%NaCl molten salt at 700 °C have been investigated. A bilayer oxide film composed of an inner Cr2O3 layer and an outer Fe2O3 layer formed on the surface of the weld metals. The mass gain rate and the thickness of the surface oxide film were enlarged with Nb addition, which could be attributed to the rapid inward diffusion of O through the cracks resulting from the Nb-oxide. Oxidation and sulfidation occur in the matrix, resulting in a large internal oxidation zone (IOZ) in the weld metal. Nb seemly promoted the sulfidation reaction due to a short-circuit diffusion of S through the interface of the Nb(C, N) and matrix and made the internal corrosion products to be distributed along the interdendritic zone of the weld metal. An apparent Cr-dealloyed layer appears in the IOZ of the weld metal. Dealloying was the detrimental form of hot corrosion of Fe–Cr–Ni-based weld metal exposed to molten salts containing chloride salts. Alloying with 0.8 wt% of Nb further accelerated the dealloying and resulted in a profound attack. [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]

The effect of the shielding gas arc welding process on the cavitation resistance of the three-component aluminum alloy AlMg4.5Mn and its welded joints was investigated. Welding was performed using the GTAW and GMAW processes in a shielded atmosphere of pure argon. After the welding, metallographic tests were performed, and the hardness distribution in the welded joints was determined. The ultrasonic vibration method was used to evaluate the base metal's and weld metal's resistance to cavitation. The change in mass was monitored to determine the cavitation rates. The morphology of the surface damage of the base metal and weld metal due to cavitation was monitored using scanning electron microscopy to explain the effect of the shielding gas arc welding process on their resistance to cavitation. [ABSTRACT FROM AUTHOR]

Al6013 base metals were joined successfully with ER4047 filler metal by using the GTAW method under different welding currents. Post-weld T6 heat treatment effects on corrosion properties were investigated in terms of open circuit potential (OCP), potentiodynamic polarization (PDS), and electrochemical impedance spectroscopy (EIS) tests. It was determined that corrosion resistance of the post-weld samples increased with increasing welding current, while T6 heat treatment only effective on 110A and 140A welding current samples (3.61 to 2.08, 2.95 to 2.40, and 1.38 to 2.15 µA·cm-2 for 110A, 140A, and 170A welding current before and after T6 heat treatment). The characteristics of the oxide films on the surfaces are revealed with EIS analysis. While the passive film originating from Al is generated on the surfaces, the two-constant equivalent circuit model found that as it also contains pittings on the surface. It was determined that the pitting resistance of the T6 heat treated 110A sample increased (3075 to 4562 O). Post-corrosion SEM surface morphologies showed that low welding currents lead to more destruction as increased exposure to corrosion. [ABSTRACT FROM AUTHOR]

This work expands findings about the dominant heat transfer mechanisms in argon and helium arcs at atmospheric pressure for monoatomic (Ar, He, 50% Ar–50% He), diatomic (air, N 2 , O 2 , F 2 , Cl 2 ), and triatomic ( CO 2 ) gases. The objective is to understand the dominant mechanisms in atmospheric plasmas through validated numerical modeling for GTAW welding process. Arcs of all gases have lengths of 10 mm and 200 A current. Five heat transfer mechanisms are considered: Joule heating, convection, radiation, conduction, and Thomson effect. Results indicate that the general structure of the arcs and dominant mechanisms are qualitatively similar for all gases; sizes change depending on the gas. The dominant energy input near the cathode is Joule heating, while that near the anode is convection. The dominant energy output always follows the same sequence: Thomson effect next to the cathode followed by convection, radiation in the arc column, and conduction near the anode. Joule heating is the most significant in Ar, while in He, it has the lowest significance. This is due to differences in electric conductivity of He (higher up to 21,000 K and lower beyond 21,000 K than other gases) and high viscosity of He, which creates a small Joule heating versus a large convection region. He transfers the most heat towards the anode by convection while N 2 has the lowest; due to the high enthalpy and viscosity of He compared to N 2 . Finally, Ar has the most significant radiative emission and He the smallest due to their net emission coefficient. [ABSTRACT FROM AUTHOR]

An attempt was made to produce graphene reinforced Inconel 718 composite by new combining accumulative roll bonding (ARB) and gas tungsten arc welding (GTAW). The phase composition analysis and wear behavior of the composite were assessed. The microstructure characterization was studied by Raman spectroscopy, scanning and transmission electron microscopy. The results display that integrating ARB with GTAW can be consider as a suitable way to yield superalloy-based composite with enhanced tribological behavior due to carbide and carbonitride formation formed from decomposition of graphene nanoplates (GNPs). The elastic modulus and hardness were initial recorded by nanoindentation and then used to attain the yield stress, and subsequently for characterizing flow behavior parameters like n and K. The obtained results exposed that the load–displacement curve acquired from nanoindentation and Nanoscratching has an excellent potential to investigate microscopic behavior of particle based composites. Evaluation of scratch mechanisms in composite specimens presented that the key failure in specimens are due to tensile state Hertzian cracks. Though, as the applied load rises, the specimen undertakes increasing incremental plastic deformation and failures change to interfacial spallation.