Gas Tungsten Research Articles

Role of buttering layer composition on microstructural heterogeneity and mechanical properties of Alloy 617 and P92 steel dissimilar welded joints for future Indian AUSC program

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.

Enhancing microstructure and mechanical properties of dissimilar TIG welded duplex 2205 and Ni-based inconel 718 superalloy through post weld heat treatment

In demanding applications, maintaining structural integrity in dissimilar welded joints like those between duplex stainless steel and Ni-based superalloys requires achieving the best possible mechanical properties. This work examines the impact of post-weld heat treatment (PWHT) on the mechanical characteristics of joints made via double-sided tungsten inert gas (TIG) welding. The dissimilar welded joint was investigated by exposing it to the PWHT for 12 h at 650 °C. Reducing the negative impact of heat generated by welding on the mechanical characteristics and microstructure of the fusion zone was the main goal. To study for changes in the microstructure before and after PWHT, optical microscopy and scanning electron microscopy methods were used for microstructural analysis. To determine the effect of PWHT on the welded joints, mechanical properties such as tensile strength, toughness, and ductility were also assessed. The mechanical properties showed significantly enhanced characteristics and refined grain structures in the fusion zone.

Investigation on microstructural and mechanical integrity of GTAW dissimilar welded joint of IN 718/ASS 304L using Ni-based filler IN 625 using EBSD and DHD techniques

The current study investigates the relationship between the microstructural and structural characteristics of dissimilar gas tungsten arc welding (GTAW) between Inconel 718 (IN 718) and austenitic stainless steel 304L (ASS 304L) using Inconel 625 (IN 625) as a filler material. The microstructural characterization of the dissimilar weld includes the application of an optical microscope (OM), field emission scanning electron microscopy (FE-SEM) including energy dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD). The optical and FESEM analysis of the base metals (BM) indicates the austenitic nature of the IN 718 BM matrix, which incorporates strengthening precipitates γ′ and γ'' distributed throughout the Nickel matrix. In contrast, the ASS 304L BM exhibits an austenitic microstructure along with twins. Moreover, IN 625 weld metal exhibits austenitic microstructure in the form of cellular, columnar, and equiaxed dendrites. Elemental segregation demonstrates the existence of Nb, and Mo-rich carbides, including the laves phases at the interdendritic regions of the IN 625 weld zone and IN 718 Heat-Affected Zone (HAZ). Ferrite stringers were noticed in the HAZ of ASS 304L. EBSD analysis shows the improved texture of the weld zone exhibiting fine equiaxed recrystallized microstructures. EBSD/Kernel average misorientation (KAM) micrographs reveal the existence of high strain at the weld metal grain boundaries. Vickers microhardness assessment of the dissimilar weld demonstrates the high hardness of 257.5 HV for the IN 625 weld zone because of the occurred NbC, laves phases, and Mo-rich carbides. Room temperature tensile characterization shows the failure of tensile specimens from ASS 304L BM reflecting the high strength of the IN 625 weld metal (662 MPa). Tensile tests at high temperatures were performed at 550 °C, 600 °C, and 650 °C. High-temperature tensile result exhibits a higher tensile strength of IN 625 weld zone than the ASS 304L BM, as the tensile specimens fails from 304L BM. The specimen exposed at 550 °C exhibits the highest tensile strength of 388 MPa. The Charpy impact toughness test was conducted, with notches at the HAZ of ASS 304L, HAZ of IN 718, and the weld center being evaluated. The toughness value of the weld metal decreases (99 J) due to occurrence of the secondary precipitates. To analyze residual stress, the deep hole drilling (DHD) technique was used, which revealed that the peak residual stress (230 MPa) is induced at 6 mm from the weld surface and falls into the tensile stress category.

Metallographic and Extraction Replica Methods for Characterization of Tungsten Heavy Alloy: H13 Clads

Tungsten heavy alloys are used in demanding high pressure die casting applications due to their high temperature strength, high thermal conductivity, and low thermal expansion. High cost limits applications to small sintered die inserts and manual gas tungsten arc weld repairs. A new tungsten heavy alloy consumable, Anviloy wire, was developed for automated cladding of hot work tool steel dies. Literature regarding characterization of tungsten heavy alloy die steel clads was lacking. Understanding base metal dilution effect on clad microstructure is critical but required new sample preparation methods. An Anviloy wire-H13 clad was made using hot wire gas tungsten arc cladding and analyzed with metallography. Samples were found to have grain boundary M6C carbide phase as-welded with the help of an alkaline sodium picrate etchant. An isothermally aged arc crucible melted sample of the same composition was characterized using metallography, scanning electron microscopy, and transmission electron diffraction. The clad representative arc crucible melted sample was subjected to isothermal aging at 725°C for 100 hours. Isothermal aging resulted in precipitation of a high volume fraction of intermetallic platelets. Using a new carbon extraction replica sample preparation method involving two chemical polishing steps, transmission electron diffraction of precipitates indicated they were mu phase intermetallic.

Characterisation of a New Generation of AlMgZr and AlMgSc Filler Materials for Welding Metal–Ceramic Composites

When manufacturing the welded joints of components made of metal–ceramic composites of the Al-Si/SiC type, we encounter significant difficulties. This is related to the presence of a ceramic phase in the aluminium alloy matrix. The interaction between the molten metal matrix and the ceramic particles in the weld pool influences a complex of physicochemical phenomena resulting in, among other things, the structure of the welded joint. This is particularly true of the effect of the distribution of ceramic particles and their influence on the crystallisation process in the weld pool. An important issue is the influence of the reinforcing particles on the susceptibility of the aluminium matrix to both hot and cold cracking. The scope of the research included the development of the chemical composition of an additive material for the TIG welding of aluminium–ceramic composites. This material was made in the form of so-called sticks, cast from alloys containing elements such as magnesium, scandium or zirconium in addition to aluminium. The appropriate composition of the mass content of the individual components was intended to change the crystallisation mode of the weld pool and to obtain strengthening precipitates. The most favourable structure was obtained in the case of a modification of the AlMg5 alloy by the addition of scandium. Minor dispersions of Al3Sc became the nucleation pads of fine grains, which improved the mechanical properties of the alloy. Also, in the case of the addition of zirconium, the crystallisation shifted from dendritic to fine-grain growth. In this paper, the basic strength properties of the developed materials were tested and the most favourable chemical compositions of the filling materials were selected.

Digital twin-based tig welding quality prediction using electrode tip angle degradation influencing Industry 5.0 in manufacturing sector

Automation in tungsten inert gas (TIG) welding is important to achieve high production rates and quality in manufacturing industries. To improve the welding process and quality inspection methodologies, the intelligent welding robot and vision-based inspection system have been researched and deployed in many engineering fields. Hence to enhance the performance and production, a digital twin-based welding system with the prediction of weld quality based on the consideration of electrode tip angle degradation. The proposed system will capture real-time electrode tip angle and weld pool temperature using a forward looking infrared (FLIR) camera along with welding current and speed correlated with tensile strength as the output parameter. To validate the analysis, support vector machine (SVM) and random forest (RF) algorithms were implemented in which the RF model performs well on the prediction of welding quality by mapping with tensile strength. RF model confirms maximum accuracy of 90% with 0.29 seconds computation time to perform prediction on the next execution of welding operation. It is inferred that if the tip angle degradation increases consecutively welding current decreases drastically impacting the weld quality from good to poor. To forecast the need for immediate or scheduled maintenance to reduce the tip angle degradation, a linear regression algorithm is implemented to enable the inspection engineer to perform maintenance without delay in production.

A Study on the Residual Stresses in Tungsten Inert Gas and Laser Welded Nitinol Superelastic Alloy

A Study on the Residual Stresses in Tungsten Inert Gas and Laser Welded Nitinol Superelastic Alloy

Methods to Improve TIG Welding Efficiency

Methods to Improve TIG Welding Efficiency

The relationship between austenite stabiliser element and post-weld heat treatment on the corrosion behaviour of the welded duplex stainless steel made by gas tungsten arc welding

The corrosion behaviour and the influence of nickel and post-weld heat treatment (PWHT) on the susceptibility to corrosion in welded duplex stainless steels were investigated. After PWHT, the amount of nickel for the weld region increases resulting in the generation of austenite and consequently, helping to obtain a favourable ferrite-to-austenite ratio. Comparing the experimental outcomes, it is noticed that the pits initiate and propagate in HAZ indicating this area is more susceptible to corrosion resistance compared to the fusion zone. The pitting resistance equivalent number alone is not sufficient reason to study the complex corrosion phenomenon, and the influence of other parameters namely microstructural evolution on the breakdown of passivity by pitting and the existence of intermetallic phases should be determined together.

Effect of alloy 625 buffer layer on corrosion resistance of nickel base hardfacing

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.

Microstructure and mechanical properties of a dissimilar metal welded joint of Inconel 617 and P92 steel with Inconel 82 buttering layer for AUSC boiler application

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 M23C6 and Mo6C 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.

Role of TiB2 inoculation particles during welding of a AlCoCrFeNi high entropy alloy

High entropy alloys (HEAs) are a novel class of materials that represent an evolution of common engineering alloys to a wider array of compositional and properties possibilities. As such, the exploration of methodologies to achieve improved microstructure and mechanical characteristics of these materials for potential applications in industry is a requirement that is experiencing extended research efforts. One example of a processing method able to expand the potential applications of these alloys is Gas Tungsten Arc Welding (GTAW), which allows to evaluate the metallurgical evolution and corresponding mechanical performance, associated to the impact of a localized heat input on the material. However, GTAW and related fusion-based welding processes are known to generate large grain sized-structures in the fusion zone, which often is detrimental to the joint performance. Thus, the integration of high temperature inoculant particles on the fusion zone during welding is a potential way to improve this region’s microstructure and, therefore, its mechanical performance. In this work, we discuss the effect that the addition of TiB2 micron-sized particles have on the microstructure of a GTAW AlCoCrFeNi-based HEA. For this, the microstructure of the welds was evaluated by means of optical and electron microscopy, synchrotron X-ray diffraction and CalPhaD-based simulations. Mechanical testing was performed using microhardness mapping and tensile testing coupled with digital image correlation. The results evidenced that successful inoculation with TiB2 proved capable of altering the microstructure of the fusion zone (FZ), refining it. Nevertheless, preferential deformation in the relatively softer heat affected zone during tensile testing resulted on premature failure of the inoculated joints, due to the concomitant higher hardness of the FZ.

Physical survey on the health hazards of welding activities on welding operators in Uyo, Nigeria

Background: Welding operators are subjected to several forms of hazards during welding activities. Aim: The study aimed to identify the common practices in welding operations, assess the potential health hazards associated with these practices, and propose recommendations for improving the well-being of welding operators. Methodology: The survey was conducted at different welding workshops in Uyo, Akwa Ibom State, Nigeria. A total of 100 welding operators were observed and interviewed to gather data on their working practices and the health effects they experienced. Results: The findings revealed that the most common welding practices included manual metal arc welding, gas metal arc welding, and gas tungsten arc welding. These practices involved exposure to various hazards such as fumes, gases, noise, and ultraviolet radiation. The survey also found that a significant number of welding operators reported experiencing health issues such as respiratory problems, skin irritation, eye injuries, and hearing loss. These health effects were attributed to the lack of proper ventilation, inadequate personal protective equipment, and poor ergonomic practices in the welding workshops. Conclusion: The findings of this study highlights the importance of addressing the health hazards associated with welding operations to ensure a safer and healthier work environment for improved work conditions and well-being of welding operators. In light of the findings, several recommendations including the implementation of proper ventilation systems, provision of adequate personal protective equipment, regular health screening for welding operators, and training programs on safe welding practices is proposed in order to improve the well-being of welding operators

Influence of inconel interlayer on microstructural, mechanical and electrochemical characteristics in single-pass ATIG welding of dissimilar austenitic and duplex stainless steel

This study investigates the impact of Inconel 625 interlayer on dissimilar welded low nickel austenitic stainless steel (LNiASS) and super duplex stainless steel (S32760) using activated tungsten inert gas (ATIG) welding. Two weldments were prepared: with and without (autogenous) interlayer. Geometrical investigation of the weld cross sections revealed that interlayer-based welding significantly increased the depth of penetration and decreased weld width as compared to autogenous welding at the same welding current. The dual microstructure was observed in the weld zone (WZ) of autogenous weldment while fully austenitic structure with few intermetallics was observed in the WZ of interlayer-based weldment. Mechanical properties, particularly impact strength observed to be improved in the case of interlayer-based weldment (91 ± 2 J) compared to autogenous weldment (68 ± 2 J). Lower microhardness was noticed for the WZ of interlayer-based weldment (258 ± 3 HV0.2) than WZ of autogenous (279 ± 2 HV0.2) weldment due to the presence of higher content of Ni. However, UTS of interlayer-based weldment (654 MPa), falls short in comparison to the autogenous weldment (693 MPa), indicating a compromised joint efficiency of 5.96%. The corrosion resistance was observed to be higher for the WZ of interlayer-based weldment attributed to the higher content of Ni and Mo. The sensitization study revealed 47.33% degree of sensitization in the WZ of autogenous weldments due to dual microstructure, while interlayer-based weldments showed no sensitization.

Characterization of the spin arc welding technique for dissimilar materials Hastelloy C-2000 and C-276

Hastelloy C-2000 and C-276 are primarily employed in the petrochemical and pharmaceutical industries. Finding an effective way to combine these alloys is still a complex task in industry. The main focus of this study is to investigate the potential efficacy of the spin arc welding process on Hastelloy C-2000 and C-276. The welding process was carried out under various conditions, such as weld current, spinning speed, and spin diameter. ERNiCrMo-4, with a diameter of 1.2 mm, was employed as a filler. Optical microscopy, XRD and FESEM were used for microstructural examination. The mechanical properties of the welded samples were critically analyzed. The results of the ultimate tensile strength (UTS), hardness value (HV), and impact tests of spin arc welding were compared with those of the multipass pulsed current gas tungsten arc welding process (MPCGTAW). In spin arc welding, Hastelloy C-2000 and C-276 exhibited higher UTS, HV, and toughness compared to MPCGTAW because there was no secondary TCP phase formation in the weld centre and hot cracking in spin arc weldments. Additionally, compared to MPCGTAW, the elongation with spin arc welding was noted to be lower. Moreover, microstructural analysis revealed no evidence of grain segregation, which may have contributed to the improved UTS and HV of the materials during spin arc welding. Thus, spin arc welding proves to be superior for dissimilar Hastelloy joints of C-2000 and C-276.

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.

Evolution of microstructure and mechanical properties of GTAW joint for magnesium alloy thin plate by post-weld reinforcement compression treatment

Gas tungsten arc welding (GTAW) joints of magnesium alloy thin plates generally exhibit low welding coefficients. Therefore, post-weld reinforcement compression treatment is utilized to improve mechanical properties of the joints in this experiment. The study shows that the grain shapes and sizes in various zones of the treated welded joints alter significantly, and the presence of twins is also detected especially in the base material (BM) and heat-affected zone (HAZ). The strength of the welded joints progressively rises with the increase in the compression reduction. The welding coefficient of the C3-joint reaches 91.6% when the compression reduction is 1 mm. The ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) are 271 MPa,173 MPa and 7.2% respectively. The post-weld reinforcement compression treatment introduces abundant dislocations in the fusion zone (FZ), contributing significantly to the increase in joint strength. In addition, solid solution strengthening and texture strengthening also exert a role.

Effect of heat input on the microstructure and hardness of AISI 321 stainless steel welds using ER 347 filler metal

Stainless steel is widely used in various fields, one of which is AISI 321, which is used for high-temperature applications because of its high resistance to creep and intergranular corrosion. The type of filler metal and heat input on stainless steel welds play an essential role in determining the microstructure and mechanical properties of the welded joints. The purpose of this experiment was to evaluate the microstructure and mechanical properties of AISI 321 stainless steel welds with variations in heat input. This study is expected to explore the performance of this weld joint, which can be anticipated in relevant fields. The welding method used in this experiment was Gas Tungsten Arc Welding (GTAW) with ER 347 as filler metal. Welding was carried out on three samples with a heat input of 0.92 kJ/mm, 0.64 kJ/mm, and 0.52 kJ/mm, respectively. The tests included tensile strength, Vickers microhardness, and microstructure observations. The tensile test results showed that a fracture occurred in the Base Metal (BM) area, indicating that the strength of the weld joint was higher than that in the BM. The Vickers microhardness test results showed that the Weld Metal's hardness (WM) was the highest, followed by the Heat-Affected Zone (HAZ) and BM. The welding experiment that used three variations in heat input demonstrated that higher heat input lowered the hardness of the weld joint. The microstructure observation results around the fusion line demonstrated the presence of step and ditch structures. The ditch structure indicates intergranular corrosion.

Overview of in-bore pipe cutting and welding tools for the maintenance of CFETR and EU-DEMO

In the remote maintenance of fusion nuclear devices, one of the most challenging tasks is the cutting and the re-welding of large pipes that feed the breeding blanket. The narrow space around some of the pipes hinders the suitability of conventional orbital processes. For such pipes, both the cutting system and the welding one have to be compact enough to move along their interior, lock against the pipe inner wall and keep the position during the operation. The inner diameter and thickness of the pipes together with the other severe requirements related to the remote maintenance drive the choice of the processing technologies and the design of the tooling configuration. In this work, activities carried out by a joint team from EU-DEMO and CFETR on the in-bore cutting and welding operations are presented and discussed. For the in-bore cutting system a solution for the simultaneous parting and bevelling has been developed opting for a mechanical cutting with a pair of symmetrically distributed knives. A preliminary dimensioning of the motors has been made assuming the radial feed and the cutting speed of the knives. For the in-bore welding system, the TIG welding with filler wire has been considered as the most reliable and suitable technology within prescribed requirements and constraints. A multi-pass welding operation has been assumed. A conceptual design of both tools has been developed. The space constraint remains the most critical issue. Further verification and validation work is planned in close collaboration between European laboratories and the Comprehensive Research fAcility for Fusion Technology (CRAFT) at ASIPP in Hefei.

ANALYSIS OF THE MICROSTRUCTURE AND MECHANICALPROPERTIES OF DUPLEX STEEL JOINTS

The article presents a study, the aim of which was to analyze the microstructure and mechanical propertiesof welded joints of austenitic-ferritic duplex steel X2CrMnNiN21-5-1. This steel is characterized by goodresistance to various types of corrosion, good strength properties and good weldability. Due to all theseadvantages, it is used in many industry sectors, and the main joining techniques are welding technologies. Inthis study, two joining techniques were used, SMAW (Shielded Metal Arc Welding) and GTA (Gas TungstenArc). The obtained welded joints were subjected to: macroscopic and microscopic metallographic tests,mechanical tests (static bending test and microhardness measurements), diffraction tests, and wear resistancetests. The results showed that the microhardness of the welds is similar and does not depend on the weldingmethod used. In the microstructure of the analyzed joints there are two phases: austenite (γ) and ferrite (δ),with different morphologies depending on the welding conditions, which affect the phase transformations.Material wear within the weld is greater than in the base material.