Gas Tungsten Arc Welding Method Research Articles

Effect Of Heat Input On Microstructure And Mechanical Properties Of Tig Welded Aisi 318ln Stainless Steel Plates

Duplex stainless steel is the type with the best corrosion resistance among all types of stainless steel. However, their cost is higher than other stainless steels. Therefore, it is more widely used in areas where the risk of corrosion is high. Therefore, the most common use of duplex stainless steel is in the petrochemical industry. In this sector, where chemicals with high abrasive power are used, duplex stainless steel is used for both the transport and storage of chemicals. Welding is an indispensable fabrication method in these applications. Therefore, there is a need for reliable welding procedures that will not adversely affect the mechanical properties and corrosion behavior of these steels in the weld zone. In this study, the microstructural evolution and mechanical properties of the 3 mm thick SAF 2205 (AISI 318LN) duplex stainless steel welded joints fabricated by the gas tungsten arc welding method using an ER2209 filler wire were investigated. The microstructures formed in the weld area were examined in detail with an optical microscope. The mechanical properties and welding performance values of the joints obtained were determined by tensile test and microhardness measurements. In addition, the effect of heat input on the microstructure and mechanical properties of welded joints was also investigated.

Study on mechanical and micro structural properties of spin arc welding in Hastelloy C-2000

Nickel-based Hastelloy C-2000 is widely used in the aerospace, chemical, and medicinal sectors. Investigating the potential efficacy of the spin arc welding process on Hastelloy C-2000 was the main focus of this study. In spin arc welding the centrifugal force has been obtained in the fusion zone, thus the weldbead quality increases. Weld current, rotating speed, and spin diameter are all separate parameters used in the welding procedure. The microstructural investigation was carried out using optical microscopy, X-Ray Diffraction (XRD), and field emission scanning electron microscopy (FESEM). The mechanical characteristics of the welded specimens were examined closely. Spin Arc Welding ultimate tensile strength (UTS), hardness value (HV), and impact experiments were compared to those of the Multi-pass Pulsed Current Gas Tungsten Arc welding method (MPCGTAW). In 27 tests, increasing the current and rotating speed resulted in greater penetration depth and weld height. The width of the weld was found to be a little high, with a spinning diameter of 2 mm. In comparison, samples 5 and 15 were found to have better hardness, tensile strength, and toughness, especially with suitable welding parameters such as current (120 I and 140 I), speed (1800 rpm), and spin diameter (2 mm and 3 mm). A microstructural study showed no grain segregation, contributing to the material’s increased hardness and tensile strength. The novel findings of the present study suggest that spin arc welding might be superior for various Hastelloy C-2000 connections that might have great applications in industries.

Analysis of Welding Current Variation of SMAW and GTAW Combination Welding with Double V Groove on The Mechanical Properties and Microstructure of SS304 Stainless Steel

In this paper, the combination of shielded metal arc welding (SMAW) and gas tungsten arc welding (GTAW) welding methods are used in a double V groove SS304 10 mm thick plate. Welding current variation of 110A SMAW/120A GTAW, 100A SMAW/130A GTAW, and 90A SMAW/140A GTAW was used to observe the effect of the welding current variation on the tensile strength and microstructure. Tensile test and metallography test were performed to observe the phenomenon. ImageJ software was used for microstructure analysis. The welding current variation resulted in higher tensile strength with the highest current on GTAW method, while a more dispersed and lathy ferrite structure was observed on the microstructure.

Effect of thickness on mechanical properties of modified 9Cr 1Mo steel welds made by narrow gap hot wire gas tungsten arc welding process

Hot wire Gas Tungsten Arc Welding (GTAW) process is selected for 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 open literature on the effect of thickness on material properties of modified 9Cr 1Mo steel welds made by hot wire GTAW method. In view of the above, authors attempted to systematically investigate the influence of thickness on mechanical properties of modified 9Cr 1Mo steel welds made by 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 62 mm thick weld was found inferior in comparison with 30 mm thick weld.

Study on Key Parameters of Dilution Ratio of the Bead Deposited by GTAW Method for Nuclear Components

It is of great significance to reduce welding hot cracks and improve the corrosion resistance of nuclear power components by controlling the dilution ratio of the cladding weld bead formed by gas tungsten arc welding (GTAW). This paper presents a method to predict the dilution ratio by using the ratio of the thermal power of forming a unit length weld to the cross-section of the fuse, that is, the linear energy of forming a unit volume of deposited metal, which is characterized by the “Heat Equivalent for Melting Welding Wire” (HEMW). It is found that there is a linear positive correlation between the HEMW and the dilution ratio. With the increase in HEMW, the proportion of deposition heat energy in the whole effective heat input energy decreases, the proportion of base metal melting heat energy increases, and the proportion of non-melting heat energy diffused to the base metal remains basically unchanged. The HEMW is used to predict and control the dilution rate under the condition of pulse welding. By increasing the wire feeding speed under the condition of pulse peak current and reducing the welding speed, a high deposition efficiency, low dilution rate and low heat input is realized, which plays an important guiding role in improving the deposition quality.

Corrosion resistance of the dissimilar alloy AL6XN-Inconel 718 in 0.5 M NaCl

In the present work, the corrosion resistance of the dissimilar alloy AL6XN-Inconel 718 bound by the Gas Tungsten Arc Welding (GTAW) method was studied. Different alloy zones were analyzed: base materials (BMs), heat affected zones (HAZs) and welds. The effect exerted by the GTAW method on the corrosion resistance displayed by such dissimilar alloy in 0.5 M NaCl was established by means of corrosion studies employing potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) tests. The electrochemical results revealed that the alloy HAZs are more susceptible to corrosion due to microstructure changes caused mainly by elements such as Ni, Cr and Mo during the GTAW process.

Experimental investigation on residual stress distribution in zirconium/titanium/steel tri-metal explosively welded composite plate after cutting and welding of a cover plate

To investigate the residual stress distribution in the zirconium/titanium/steel tri-metal explosively welded composite plates after welding a cover plate and cutting with various methods, two specimens made of the composite plate were prepared. The flame cutting method and the abrasive waterjet cutting method were employed to cut the two edges of the specimens. And a cover plate of zirconium was welded to the cladding layer of one specimen with the gas tungsten arc welding method. The contour method was adopted to get the full map of residual stress distribution in the specimens. The stresses induced by the flame cutting and the abrasive waterjet cutting in the composite plate were distinguished and the interfacial stress distributions in the composite plate without and with welding a cover plate were investigated. The result shows that longitudinal tensile stress with a magnitude of about 200 MPa occurs in the titanium/steel interface of the composite plate after welding of zirconium cover plate, and the tensile stress on the steel side reaches the yield strength of steel. After welding the 60 mm-wide cover plate to the composite plate, the stress induced by the welding of one side of the cover plate has almost no effect on that induced by welding of the other side of the cover plate. The flame cutting method can induce large tensile stress in the steel base plate with a magnitude equal to the yield strength of steel and a width up to 22 mm. The water-jet cutting has relatively less influence on the stress at the cutting edge.

Advanced Structural and Technological Method of Reducing Distortion in Thin-Walled Welded Structures.

The article presents an innovative method of reducing welding distortions of thin-walled structures by introducing structural and technological changes. The accuracy of the method was demonstrated on the example of welding the stub pipes to the outer surface of a thin-walled tank with large dimensions, made of steel 1.4301 with a wall thickness of 1.5 × 10−3 (m). During traditional Gas Tungsten Arc Welding (GTAW), distortions of the base are formed, the flatness deviation of which was 11.9 × 10−3 (m) and exceeded the permissible standards. As a result of structural and technological changes, not only does the joint stiffness increase, but also a favorable stress state is introduced in the flange, which reduces the local welding stresses. Numerical models were developed using the finite element method (FEM), which were used to analyze the residual stresses and strains pre-welding, in extruded flanges, in transient, and post-welding. The results of the calculations for various flanges heights show that there is a limit height h = 9.2 × 10−3 (m), above which flange cracks during extrusion. A function for calculating the flange height was developed due to the required stress state. The results of numerical calculations were verified experimentally on a designed and built test stand for extrusion the flange. The results of experimental research confirmed the results of numerical simulations. For further tests, bases with a flange h = 6 × 10−3 (m) were used, to which a stub pipe was welded using the GTAW method. After the welding process, the distortion of the base was measured with the ATOS III scanner (GOM a Zeiss company, Oberkochen, Germany). It has been shown that the developed methodology is correct, and the introduced structural and technological changes result in a favorable reduction of welding stresses and a reduction in the flatness deviation of the base in the welded joint to 0.39 × 10−3 (m), which meets the requirements of the standards.

Experimental and simulation of C45 steel bar heat treatment with the GTAW method application

The motivation of the paper is an attempt to indicate the relationship between the selected Gas Tungsten Arc Welding (GTAW) technology and the parameters of the boundary conditions for the simulation of the heat treatment process of elements made of medium-carbon steel. The authors of the paper prepared and described a series of numerical simulations and experimental studies concerning this problem. Simulations often use previously-developed analytical equations to describe the relationships between process parameters. The results obtained for the input data for determining the heat source power (voltage) from the analytical equation and experimental measurements were compared. Several cases of the size of the areas of direct influence of the GTAW arc (various radius of a simulation heat source) were analysed. All computations were performed in the author’s software based on Finite Element Method (FEM) solving the heat transfer equation with the convection term. In this paper, the GTAW heating parameters (boundary condition) for a current intensity equal 30 A were identified. With the assumed arc efficiency coefficient, the arc voltage set on the device and the measured value of the arc current, the optimum radius of the heat source was determined. The identification of parameters was confirmed by the convergence of the results of numerical simulation in three-dimensional space (3D) with the results of the experiment. Unfortunately, the applied methodology did not give good results for current equal to 50A.

Microstructure, mechanical and corrosion properties of TIG welded Hastelloy C-276

Abstract Hastelloy C-276 is a corrosion resistant nickel based solid solution hardened industrial alloy which has superior mechanical and corrosion properties. In this study, Hastelloy C-276 alloy was welded via the GTAW (Gas tungsten arc welding) method using ERNiCrMo-4 filler metal. Tensile, bending and notch impact tests were performed to determine the mechanical properties. The microstructure of the weld metal was investigated by light microscopy (LM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The impact toughness values of the heat affected zone (HAZ) showed a better performance than those of the weld metal. In addition, the corrosion properties of the weld metal and the base material were investigated by potentiodynamic polarization tests. Electrochemical potentiodynamic polarization parameters were determined according to corrosion behavior and microstructure properties. In particular, the corrosion rate of the weld metal increased because of the Mo-rich phases deposited in the weld metal microstructure.

Microstructure, mechanical and corrosion properties of TIG welded Hastelloy C-276

Abstract Hastelloy C-276 is a corrosion resistant nickel based solid solution hardened industrial alloy which has superior mechanical and corrosion properties. In this study, Hastelloy C-276 alloy was welded via the GTAW (Gas tungsten arc welding) method using ERNiCrMo-4 filler metal. Tensile, bending and notch impact tests were performed to determine the mechanical properties. The microstructure of the weld metal was investigated by light microscopy (LM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The impact toughness values of the heat affected zone (HAZ) showed a better performance than those of the weld metal. In addition, the corrosion properties of the weld metal and the base material were investigated by potentiodynamic polarization tests. Electrochemical potentiodynamic polarization parameters were determined according to corrosion behavior and microstructure properties. In particular, the corrosion rate of the weld metal increased because of the Mo-rich phases deposited in the weld metal microstructure.

Properties of UNS 10276 Nickel Alloy and SA 516 GR 70 Steel Dissimilar Weldment

Abstract At moderate and high temperature applications, nickel-based superalloys are widely preferred as suitable candidate materials due to their high mechanical properties and corrosion/oxidation resistance, however, difficulties in mass production of these alloys and their cost cause the use of these alloys as a part of dissimilar weld joints with any structural material. In this study, a dissimilar weld joint between a nickel-based superalloy (UNS 10276) and unalloyed steel (SA 516 GR 70) was successfully performed by gas tungsten arc welding method by using ErNiCrMo-3 filler metal. Initially, the microstructural features of base materials, heat affected zone and weld metal were characterized and cellular, coarser cellular and epitaxial growth dendrites as matrix phases and several Mo-rich and Nb-rich precipitates embedded in the solidified structure were observed in weld metal. In heat affected zones and fusion lines of the dissimilar joints, some metallurgical phenomena like partially melted zone, solidification at grain boundary, migrated grain boundary and decarburization were also examined. All these microstructural features affected the mechanical properties.

Virtual corrosion testing on stainless steel AISI 304 welded pipe with Hydroxyethyl Cellulose in 3.5% NaCl solution and turbulent flow

A virtual corrosion testing machine is used to investigate the corrosion inhibition efficiency and mechanism of an inhibitor in stainless-steel 304 pipes under turbulent flow conditions. The pipes are welded by the gas tungsten arc welding method and evaluated in 3.5 percent sodium chloride solution with absence (0 ppm) and presence 100, 300, and 600 ppm hydroxyethyl cellulose concentrations. The solutions are absence and presence the inhibitor, are fed in the welded pipe at a flow rate of 7,500 and 15,000 cm3 per minute as behaves to be turbulent flows. Electrochemical impedance spectroscopy and potentiodynamic polarization techniques are used to investigate the corrosion inhibition process. The inhibitor can adsorp on the surface of stainless steel welded pipe and inhibit the corrosion rate of the stainless steel. The concentration volumes of the inhibitor are correlating the corrosion rate in the same direction. The turbulent flow is to reduce the adsorption mechanism of the inhibitor, affect to corrosion reaction for the stainless-steel welded pipe and relate to the corrosion rate. If the flow rate increases, the corrosion rate would also increase. The corrosion inhibition efficiency is reached up to 66% by addition HEC 600ppm concentration in the condition. Pitting corrosion is observed on the heat-affected zone of the welded pipe by scanning electron microscope.

Exploration of mechanical and metallurgical characterization of Incoloy 20 weldment using gas tungsten arc welding methods

In this paper, metallurgical and mechanical properties are assessed for Incoloy 20 weldment made using traditional arc welding methods with ERNiCrMo-4 filler metal. High magnification microscopes (optical and scanning electron microscopes) are utilized to observe the microstructure of welded specimens. Energy dispersive X-ray spectroscopy is utilized to explore the elemental segregation of welded specimens. Secondary precipitates formed during welding are identified through X-ray diffraction method. It is explored that crack-free weldments are achieved from both continuous current gas tungsten arc welding (CCGTAW) and pulsed current gas tungsten arc welding (PCGTAW) processes. Hardness, impact and tensile tests are conducted to identify the mechanical properties for welded specimens. Results of CCGTAW and PCGTAW specimens are compared and analyzed in detail. Comparatively, PCGTAW specimens offered better results than that of CCGTAW.

Surface remelting treatment of 7075 aluminum alloy—microstructural and technological aspects

7075 aluminum alloy in the T6 state was subjected to surface remelting treatment using Gas Tungsten Arc Welding (GTAW). The changes in the material microstructure were examined by means of light microscopy, scanning electron microscopy and EDS. Moreover, profilometric tests and comparative measurements of material hardness in the state before and after the treatment were conducted. In the remelted layer strong microstructure refinement and the disappearance of microstructure banding were found. A fine dendritic microstructure was dominant in the remelted zone. Use of the GTAW method reduced the number of intermetallic precipitates in the surface layer. A consequence of dissolving the precipitates was a decrease in the hardness of the material in relation to the hardness before the modification. All the samples were characterized by the presence of a remelted zone, a narrow partially remelted zone and a wide heat affected zone. With an increase in the heat source travel speed, and consequently less heat entering the remelted material, the dimensions of the individual zones decreased. The conducted research showed that GTAW technology can be used in the surface remelting treatment of aluminum alloys and can be a competitive solution in comparison to other technologies.

Comparative study of microstructure and properties of low-alloy-steel/nickel-based-alloy interfaces in dissimilar metal weld joints prepared by different GTAW methods

Low-alloy-steel/buttering (or welding) metal interfaces in safe-end dissimilar metal weld joints (DMWJs) at nuclear power plants are weak parts. To optimize the quality of the safe-end DMWJs used for the construction of domestic nuclear power plants and to improve the welding productivity, a series of DMWJs in full-size have been manufactured by using different gas tungsten arc welding (GTAW) methods. The microstructure, chemical composition distribution and local properties across the SA508/52(M) interfaces in these DMWJs are studied. The high heat input and long high temperature duration during hot-wire GTAW process promote the carbon diffusion and grain boundary migration and hence the DMWJ by hot-wire GTAW has the largest amount of type I and type II boundaries and the widest carbon depleted zones and carbon enriched zones, which resulting in the worst performance among the DMWJs in simulated primary water. Type I and type II boundaries are high angle random grain boundaries (RGBs) and Cr-depleted zones are found along type II boundaries resulting in their high susceptibility to SCC. In addition, these boundaries are prone to be cracked during mechanical bending process.

Development of welding technique to avoid the sensitization in the alloy 600 by conventional Gas Tungsten Arc Welding method

Even though Nickel based superalloy (alloy 600) exhibits high corrosion resistance at elevated temperatures, the main limitation of this alloy is the formation of Cr-depleted zones in the grain boundary regions. In this regard, there is a constant demand for the reduction of Cr-depleted (sensitization) zones towards various applications. In order to achieve this, the present work is focussed on the fabrication of weld joints by Gas Tungsten Arc Welding (GTAW) and Pulsed Current Gas Tungsten Arc Welding (PCGTAW) using the filler wires such as ERNiCr-3, ERNiCrMo-3, and ERNiCrMo-14 to avoid sensitization. The fabricated materials were analyzed by optical and scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). The macro examination of these welded materials clearly reveals the presence of defect-free weld joints. As per the results from the microstructural analysis, the rapid cooling was achieved in the pulsed current technique, and subsequently, the equiaxed dendrites were observed in the fusion zone. EDS analysis showed the presence of Nb-rich (MC) carbide phases near the joints fabricated by filler wires i.e. GTA ERNiCr-3 and ERNiCrMo-3 indicating the preferential formation of Nb-carbide over Cr-carbide. In a similar way, Mo-rich M23C6 phases were observed near the joint fabricated by the filler wire, GTA ERNiCrMo-14. There was no microsegregation observed during the fabrication through the PCGTA welding technique.

Evaluation of microstructure and mechanical properties of dissimilar welding of copper alloy and stainless steel

The dissimilar welding of copper alloy and stainless steel was achieved with a gas tungsten arc welding method. We evaluated the mechanical properties of the post weld. The experimental results indicated that the tensile stress of the post weld of a CuCrZr/SS and OFHC/SS dissimilar joint achieved 310 and 220 MPa, respectively. The morphology of the fracture surface of the post tensile showed a dimple pattern structure; the microhardness showed a distribution of hardness 70~130 Hv in the fusion zone. Observations with a scanning electron microscope indicated that the Fe and Cr elements of stainless steel were mutually soluble in the copper substrate and confirmed that the dissimilar joint was successfully combined.

Surface modification of the AZ91 magnesium alloy

The main purpose of the study was to modify the surface layer of the AZ91 magnesium alloys with the use of the GTAW (Gas Tungsten Arc Welding) method. The remelting process was conducted with the use of an AC current with the concurrent cooling of the magnesium alloy in the liquid nitrogen bath. The assessment of the effectiveness of the treatment carried out with the use of the GTAW method was based on the analysis of the surface layer structure, and the investigation of hardness and the resistance to abrasion wear. Besides, the investigations of the corrosion resistance were carried out. The analysis of the treatment parameters combined with a macroscopic assessment and the structural changes in the surface layers allowed to distinguish some correlations attesting to the possibility of the remelting zone geometry shaping. The found structural effects of treatment such as significant refinement of the structure and its homogenization, as well as the positive results of corrosion investigations and mechanical tests proved that it is possible to achieve the intended research objectives and effectively modify magnesium alloys by the welding method.

Microstructure and tribological properties of gas tungsten arc clad TiC composite coatings on carbon steel

Purpose – The purpose of this paper is to evaluate the wear performance of carbon steel cladded with TiC powders by gas tungsten arc welding method. Because of poor wear resistance, carbon steels have limited industrial applications as tribological components. Design/methodology/approach – The cladding microstructures were characterized by optical microscope, scanning electron microscope (SEM) and X-ray energy dispersive spectrometer. The wear behavior of the clad layer was studied with a block-on-ring tribometer. Findings – The experimental results revealed that the metallurgical interface provided an excellent bond between the cladding and the carbon steel substrate. The cladding revealed no porosity or cracking, and particles were evenly distributed throughout the cladding layer. Hardness was increased from HRc 6.6 in the substrate to HRc 62 in the cladded layer due to the presence of the hard TiC phase. Originality/value – The experiments confirm that the cladding surfaces of TiC particles reduce wear rate and friction. Increasing TiC contents also improves hardness and wear resistance at room temperature and under dry sliding wear conditions.