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

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

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.

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]

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

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

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

A comparative study was carried out on GTAW AISI 316 welds fabricated by three different filler metals including ER-317M, ER-316 and ER-308. Filler metals were selected in a way to induce varying Molybdenum (Mo) concentrations in the weld metal, so that the effect of Mo on the microstructural, mechanical and corrosion behavior of the welds was investigated. Microstructural studies revealed that as Mo concentration increased in the weld metal, the dendritic morphology of this zone gradually was changed from cellular dendritic to columnar dendritic and a noticeable amount of austenitic phase and precipitations were formed. Mo-containing ER-316 and ER-317M welds showed appreciable amount of Mo- and Cr-rich carbides such as (Fe,Cr)23C6 which formed at the grain boundaries of δ-ferrite phase resulting in increased the hardness and strength of welded samples. The highest microhardness value of 188 HV and yield strength of 330 MPa belonged to ER-317M welds containing the highest Mo concentration. Also, corrosion resistance of the welds significantly improved by increasing Mo concentration and a minimum corrosion rate of 4.178 mm/year was accounted for ER-317M welds in which, the formation of passive film was more facilitated due to the higher concentration of Mo.

The wire and Arc Additive Manufacturing process has marked attention due to its higher deposition rates and lower fabrication cost. Many of the researchers have investigated the effect of process parameters of arc-based process like current, wire feeding speed, distance between two adjacent beads i.e. scan spacing on the forming quality and geometry of the deposited thin walled structures. This article gives an impression on the potential of the Wire Arc Additive Manufacturing process to manufacture a fully dense3D metallic structure. The experiments are carried out for the deposition of a fully dense 3D metallic structure with fine dimensional accuracy. A cuboid shaped structure has been successfully deposited by using GTAW based additive manufacturing system. The dimensional accuracy of the cuboid structure deposited by GTAW based additive manufacturing process has been evaluated in this paper. The results showed that the developed process can produce dense metallic structure with enhanced dimensional accuracy and mechanical properties. [ABSTRACT FROM AUTHOR]

The gas tungsten arc weldability of micro-alloyed hot-rolled ferritic XPF800 steel, which is newly produced by Tata Steel, has been studied. The weld geometry profile, mechanical properties and microstructure affected by heat input have been investigated. The micro examination of the welded joint has been characterized utilizing optical microscope and scanning electron microscope. Atomic concentrations of metallic elements in carbides have been determined by energy dispersive X-ray spectrometry. The optimum parameters for current, welding speed and heat input have been found to be 140 A, 100 mm/min and 0.62 kJ/mm in the GTAW of XPF800 plates, respectively.

This study presents an appropriate filler metal or welding electrode to join aluminum alloy (AA2024-T3) sheet of 3.2 mm thickness with a square butt joint using Gas Tungsten Arc Welding (GTAW) process. This process was carried out at three different welding currents with three various filler metals: ER4047 (12% Si), ER4043 (5% Si), and ER5356 (5% Mg). Experiments were conducted to investigate the microstructure and the mechanical properties. The effect of various filler metals upon the weld joints quality were analyzed via an X-ray radiographic and tensile test. Hardness test, microstructures, SEM, and XRD also conducted to the welded specimens. It was found that the best result was at 100 Ampere with using filler metal (ER5356) which produced the highest strength of 240 MPa in comparison with welded joints with utilizing fillers (ER4043) and (ER4047) having values of 235 MPa and 225 MPa, correspondingly. The hardness results showed that the highest hardness values were at the weld metal for ER4047 and ER4043, then decreased to HAZ and increased in the base metal. While in the case of ER5356, the highest hardness was in HAZ and decreased in the weld metal. The fractography of the fracture surface of the welded joints after the tensile test was analyzed using SEM

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

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

In this research, the microstructural, mechanical and corrosion properties of the dissimilar joint of ASTM A537CL1 to AISI A321 steels produced by GTAW process were studied. The welding process was done with ER308L filler metal without pre and post weld heat treatment. The scanning electron microscope and optical microscope were used to study the microstructure and fracture surface of the welded samples. Also, the mechanical behavior of the joint was evaluated by impact, tensile, bending and microhardness tests. The results illustrated that the microstructure of the weld metal was austenite with dendritic structure contained skeletal and lathy ferrite. In tension tests, all weldments failed from A537 base metal. The results of impact test indicated that all specimens exhibit ductile fracture and indicated high impact energy of about 205 J. In fine grain HAZ of A537 steel, because of formation of fine equiaxed grains due to the allotropic transformation, high microhardness was seen. While, in coarse grain HAZ, due to the formation of bigger grains, carbon migration and decreasing in the amount of pearlite phase, the microhardness slightly decreased. The exsistence of chromium in microstructure improved the corrosion resistance and the weld metal indicated acceptable corrosion resistance as compared with both base metals. [ABSTRACT FROM AUTHOR]

In this work, the influence of filler wire diameter on AA5083-H111 weldments was studied. For that, square butt joints were made using an AC square wave gas tungsten arc welding process with the addition of filler wires of diameter 1.2 and 2.4 mm separately. The experimental results revealed that changing the filler wire diameter influenced the bead geometry and a complete penetration was achieved in both welds. The weldment processed with smaller diameter filler wire consisted of a wider heat affected zone with recrystallized grains and a fusion zone with coarser grain structure, thus reducing the mechanical properties and corrosion resistance. However, the use of larger diameter filler wire assisted in faster torch speed, resulting in lower heat input and thus finer equiaxed grains were produced in fusion zone. Also, finer grains along with the dispersion of finer Al6(Fe,Mn) particles supported in obtaining the superior tensile and corrosion properties. [ABSTRACT FROM AUTHOR]

Al 3003 alloy is well known for its industrial use as heat exchangers, radiators, oil tanks and household utensils. In case of heat exchangers, fabrication becomes mandatory by a welding process which is carried out by gas tungsten arc welding (GTAW). It is preferred due to its advantages of superior mechanical properties. Thus by involving GTAW process and reinforcing with suitable nanoparticles, the strength of Al 3003 alloy can be improved at the joints. Hence this technical paper deals with the fabrication of Al 100–x – x wt% TiO 2 (x = 0, 0.75, 1.5, 2.25 and 3) nanocomposite filler metal through accumulative roll bonding (ARB) technique to weld Al 3003 alloy through GTAW. Further characterization studies have been made through various electron microscopic techniques besides X‐ray diffraction analysis (XRD), vicker's microhardness and tensile testing. It was observed that the incorporation of TiO 2 nanoparticles reduced the grain size much due to the formation of more nucleation sites and deceleration growth. XRD results revealed the presence of TiO 2 peaks in the composite. FESEM confirmed the distribution of second phase nanoparticles regularly in the Al matrix. TEM analysis showed that the nanoscale TiO 2 distribution and strain fields due to thermal mismatch between matrix and reinforcement. The improvement in mechanical properties was owing to good interfacial bonding between the Al matrix and ceramic nanoparticles. [ABSTRACT FROM AUTHOR]

Gas tungsten arc welding (GTAW) was used to join plates of Inconel 718. The mechanical properties were determined by tensile, microhardness, and instrumented Charpy impact tests. An ERNiFeCr-2 filler metal fed by a semi-automatic mechanism was used. Partial dissolution of the strengthening phases, γ' and γ", induced a soft region (~ 225 HV1.0) in the heat-affected zone (HAZ) during welding. The yield strength (371.3 MPa) of the as-welded joint is approximately 45% of the base material in aged condition (822.7 MPa). The welds were subjected to a hardening recovery post weld heat treatment (HRPWHT). Impact testing of the hardened welds revealed a reduction of 17% in energy absorbed with respect the aged base material. Hardness measurements showed an increase to ~ 410 HV0.1 in the fusion zone; however, due to segregation of Nb and formation of carbides, the precipitation of γ" is not fully completed, and the yield strength (719 MPa) of the heat-treated welded joint is lower than the base material in aged condition. [ABSTRACT FROM AUTHOR]

In the present work, dissimilar welding between UNS S32205 duplex stainless steel (DSS) and 316L austenitic stainless steel (ASS) was performed by using gas tungsten arc welding and ER2209 filler at two different heat inputs (0.52 and 0.98 kJ/mm). Microstructures were characterized using reflected light optical microscope and scanning electron microscope. Micro-hardness and tensile properties were measured across the weld for both the heat inputs. The microstructure of the welded region was primarily austenitic (for both heat inputs) with Widmanstätten morphology. The grain size of the heat affected zone on DSS side was very large (~200 µm) for the high heat input sample with the presence of partially transformed austenite and acicular austenite. The precipitation of intermetallic phases and carbides was not observed for both the heat inputs. The proportion of ferrite in the weld metal (as measured by feritscope) was higher for the high heat input sample than the low heat input sample. During the tensile test, fracture occurred in 316L ASS base metal (because of its lower strength) in ductile manner. For high heat input welds, the impact tested sample showed the presence of fine spherical precipitates rich in Cr, Mn and Fe in the fracture surface of weld metal. [ABSTRACT FROM AUTHOR]

In the present study, SiC powder was added in situ for bead-on-plate weldments and fusion butt joints to modify the microstructure and the corresponding mechanical properties. Cross sections of bead-on-plate welds demonstrated that the SiC addition resulted in significant changes of the titanium microstructure. Specifically, a fine lamellar structure of α-phase with a small amount of intergranular β-titanium within the fusion zone could be established. Moreover, the size of prior β-grains was significantly reduced. After welding, no intermetallic silicides were observed. In the fusion zone of the SiC-enhanced samples, a small increase in hardness resulted, and the samples showed an increase in tensile strength, yield strength and elongation. [ABSTRACT FROM AUTHOR]

Celem pracy była ocena wpływ u metody napawania Inconelem 625 rur kotłowych ze stali P235GH i 16Mo3 na mikrostruk- turę i własności podłoża i napoiny. Badania prowadzono na odcinkach rur kotłowych napawanych stopem niklu Inconel 625. Rury zostały dostarczone do Fabryki Kotłów SEFAKO S.A. przez czterech dostawców, stosujących różne metody napawania, a mianowicie CMT, GMAW i GTAW. Badania wykazały, że mikrostruktura i własności mechaniczne rur napawanych istotnie zależą od zastosowanej metody napawania oraz od składu chemicznego materiału podłoża.

Postproduction heat treatments were carried out on additively manufactured γ-TiAl alloys that were produced by using the gas tungsten arc welding (GTAW) process. The microstructural evolution and mechanical properties of both as-fabricated and heat-treated specimens were investigated to assess the effect of different heat treatment conditions, by using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Neutron Diffraction and tensile tests. The results indicated that heat treatment promotes the formation of the γ phase in the majority region after heat treatment at 1200 °C for 24 h, while a fully lamellar structure was formed in the near-substrate zone. The response to heat treatment at 1060 °C/24 h was markedly different, producing a fine lamellar structure with differing sizes in the majority region and near-substrate zone. These various microstructural characteristics determined the mechanical properties of the heat-treated samples. The heat-treated samples at 1200 °C/24 h exhibited lower UTS and microhardness values but higher ductility than the as-fabricated samples without heat treatment, while the 1060 °C/24 h heat treatment resulted in higher UTS and microhardness values but lower ductility. Due to the homogenous microstructure in the majority region after each postproduction heat treatment, the tensile properties were similar for both the build direction (Z) and travel direction (Y), thereby minimising the anisotropy that is exhibited by the as-fabricated alloy prior to heat treatment. [ABSTRACT FROM AUTHOR]

Titanium and its alloys have excellent combination of properties, such as low density, high specific strength and corrosion resistance, and they are extensively used in many industrial fields. This work is aiming at investigation on the microstructure and mechanical properties of Ti–6Al–3Nb–2Zr–1Mo (Ti6321) alloy joints by Gas Tungsten Arc Welding (GTAW) with filler materials. The results indicated that the microstructure of the fusion zone (FZ) is composed of acicular α , massive α , and Widmanstatten α + β . The heat affected zone (HAZ) near FZ consists of coarse and acicular α structures of grain boundary α , Widmanstatten α + β . The heat affected zone (HAZ) near base metal consists of primary α phase and transformed β containing acicular α . Microhardness values for HAZ are higher than that of FZ and base metal, and there are the peak values for the HAZ near the weld metal. The tensile strength of joint is almost equal to that of base metal, and the fracture locations of all the tensile specimens are in base metal, and it is well in accordance with the relationship between the content of strengthening and interstitial elements and microstructure and mechanical properties of welded joints. The tensile fracture morphology of joint presents obviously the characteristic of ductile fracture, which is related to the bigger and deeper dimples distributed on the surface of joint. The HAZ impact toughness is lower than that of the BM and FZ. [ABSTRACT FROM AUTHOR]

Grain growth in Ti6Al4V alloy during fusion welding decreases yield stress and tensile strength. This study examined the effect of mechanical vibration of the work piece during GTAW welding on the mechanical and metallurgical properties of Ti6Al4V. The structures of all welded specimens at different levels of vibration was examined and it was found that, during 330 Hz vibration, grain size in the welded metal zone decreased significantly over that of pieces welded without vibration. GTAW at 330 Hz significantly increased the mechanical properties and produced the highest yield strength, tensile strength and percentage of elongation. The highest level of hardness in the welded metal zone was achieved under this condition. [ABSTRACT FROM AUTHOR]

The Cr–Mo steel containing 9% Cr is generally preferred in producing high-temperature operating components (lower than 620 °C) like steam pipes and headers due to their outstanding combination of elevated temperature mechanical properties and creep strength. The components with an operating temperature of more than 620 °C (superheater and reheaters tubes) are mainly produced using stainless steel or Ni-based superalloy. Hence due to economic aspects of boilers, joining of P92 steel with Ni-based superalloy is inevitable in advanced ultra-supercritical (AUSC) plants. Thus the development of joining technology without diminishing the high-temperature mechanical properties of the weldments becomes essential. The present work introduces the microstructure evolution in gas tungsten arc welded (GTAW) dissimilar joint of P92 steel and Inconel 617 alloy produced by using the P92 filler. The microstructure study along weldments was examined using an optical microscope (OM) and field emission scanning electron microscope (FESEM). The mechanical properties of welded joint and joint integrity were determined by using the microhardness measurement, cross-weld tensile tests, and impact toughness test. The effect of the post-weld heat treatment (PWHT) on mechanical properties and microstructure evolution was also performed. The residual stresses were also examined using the blind hole drilling methods, and the effect of PWHT on the nature and magnitude of the residual stresses were also conducted. The microstructure observation showed the martensitic lath structure in the weld metal, which resulted in poor impact toughness (36 ± 5 J) and high hardness (458 ± 25 HV) of weld metal in the as-welded condition. A considerable increase in impact toughness (90 ± 4 J) and a decrease in hardness (371 ± 11 HV) of weld metal were observed after the PWHT. A wide region of the unmixed zone at the interface of weld metal and Inconel 617 was formed due to the difference in chemical composition and structure. The unmixed zone formation led to the poor tensile properties of the welded joint, and failure was observed both in P92 BM and at the interface of weld metal and Inconel 617 interface. The tensile tested sample failed from the interface region and showed the presence of Ti(C, N) particles, while secondary phase M 23 C 6 particles were obtained from the tensile sample fractured from P92 BM. The impact test results also showed the variation in impact toughness along the weldments. The P92 BM was found the strongest zone, while weld metal was noticed as the weakest zone in terms of impact toughness. The variation in residual stresses was also measured along with the thickness of the plate, and the peak magnitude of the residual stresses was measured in the capping pass, which was compressive in nature. • Study the microstructure and mechanical properties of dissimilar welded joints of P92 steel and Inconel 617 alloy. • Study the effect of PWHT on the microstructure evolution and mechanical properties. • Through thickness residual stress study in weld metal using the deep hole drilling method. [ABSTRACT FROM AUTHOR]

In this study, the effects of heat input variation in gas tungsten arc welding (GTAW), on structure and mechanical properties of commercially C86300 (containing addition of 0.6 wt% silicon) weld joint were investigated. Following microstructural characterization of Base metal, GTAW has been performed at welding currents 50 and 60 A and flow rates of argon shielding gas (10, 14 and 18 l/min) using the same filler metal composition. Therefore six GTAW samples were performed with various welding specifications. By structural investigations and hardness profiles, effects of increasing heat input on increasing average grain size in weld zone, heat affected zone width, penetration depth and alloying element losses were indicated. However increasing heat input increases penetration depth and has a positive effect on hardness and strength of the joint. In considering wear application of this alloy castings and probable GTAW for them, pin-on-disc wear test was performed and revealed better wear resistance of weld metal in comparison with base metal. Hence the optimum values of welding current and argon flow rates (in GTAW with the same composition filler) was determined for this alloy. [ABSTRACT FROM AUTHOR]

• Al 0.2 CoCrFeNiMo 0.5 two phase HEA was successfully welded. • Microstructural variation across different weld zones were investigated. • Marginal variation of hardness was observed in Fusion zone and HAZ. • Comparable strength with a reduction in the failure strain of the welded sample. In the present study, wrought processed Al 0.2 CoCrFeNiMo 0.5 high entropy alloy (HEA) was welded using gas tungsten arc welding (GTAW) to determine its potential as a structural material. The microstructural changes during welding were analyzed and correlated with the mechanical properties. The welded HEA specimen has shown similar microstructural constituents, a typical FCC matrix with BCT secondary phase (sigma). The microstructure changed from irregular and heterogeneous secondary phase in base metal (BM), to eutectic broken lamellae of sigma phase in FCC matrix at heat affected zone (HAZ) and as-cast structure (dendritic and interdendritic regions) of sigma phase in FCC matrix at fusion zone (FZ). Upon tensile testing, the welded specimens fractured in the FZ with comparable tensile properties. [ABSTRACT FROM AUTHOR]

Titanium alloys used in aerospace structures require joints of high integrity to meet the design requirements. Gas tungsten arc welding (GTAW), laser beam welding (LBW) and electron beam welding (EBW) are all processes capable of creating fusion welded joints. Gas tungsten arc welding offers the potential to achieve welds of equal quality to EBW or LBW at much lower capital costs; however, the application of GTAW involves gaining an understanding of the complex process characteristics. This paper reviews the process characteristics for GTAW titanium alloys and compares these characteristics with EBW and LBW titanium alloys. The characteristics of active flux tungsten inert gas welding and keyhole mode GTAW, two recent developments to GTAW, are considered, as is keyhole mode plasma arc welding. These variants are capable of greater penetration and, in some cases, faster processing speeds than conventional GTAW. Finally, the current knowledge of weld microstructural development in cast and wrought α/β titanium alloys and the mechanical performance of such welded joints are examined. Notably, conduction mode GTAWs are shown to have comparable mechanical properties with EBWs in relation to both cast and wrought base metals. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure and mechanical properties of fusion zones of medium strength Al–Zn–Mg alloy (RDE-40) welds obtained by using different fillers containing various amount of scandium was investigated. It was observed that addition of scandium led to very significant grain refinement in the fusion zone especially for scandium levels greater than the eutectic composition (0.55wt%). The grain refinement led to the reduction in solidification cracking and improved the tensile properties of fusion zone compared to the ones obtained by the commercial AA5556 filler. [Copyright &y& Elsevier]

Gas tungsten arc welding (GTAW) is a widely used joining technique due to its low welding cost and flexible process. To promote the application of titanium/copper dissimilar metal welded structure, the microstructures and properties of TA2 titanium and T2 copper butt joint prepared by GTAW with pure copper filler metal (S201) and Cu–Al filler metal (S214) were systematically investigated. The microstructures of the joints were analyzed by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), and the properties of the joints were evaluated by tensile, microhardness and electrochemical corrosion tests. The results suggested that the intermetallic compound layers of S201 filler metal weld joint were composed of rod-like Ti 2 Cu, plate-like TiCu, needle-like TiCu and a small amount Ti 3 Cu 4. While plate-like TiCu were not found when using S214 filler metal. Moreover, the weld joint with S201 filler metal displayed a better plasticity and a higher tensile strength having 73.0% tensile strength of copper base metal. The electrochemical corrosion tests indicated that Al elements in weld joint with S214 filler metal could inhibit the cathodic reaction, and decrease the dissolution of weld seam metal. [ABSTRACT FROM AUTHOR]

In the present investigation, a detailed microstructure and mechanical behaviour study for P91 welded joint were investigated. The welded joint was produced using the Gas Tungsten Arc welding (GTAW) process with dissimilar Ni-based filler IN625 (ERNiCrMo-3). For microstructure characterization of the weld joint, optical microscopy and scanning electron microscopy were utilized. The effort was made to get a relationship between microstructure and mechanical properties variation. The residual stress measurement was also carried out for both the condition by using the hole-drilling method. To evaluate the mechanical properties, tensile testing and Charpy testing was done at room temperature. The weld joint developed with dissimilar Ni-based filler processes the austenitic microstructure having equiaxed dendrites in bulk weld metal and columnar and cellular dendritic structure near the interface. The segregation of the alloying elements like Mo and Nb was also confirmed along the inter-dendritic areas. The welded joint qualified the tensile test and Charpy test with average value of 580 ± 12 MPa and 65 ± 5 J, respectively in as-welded. However, a reduction was observed in tensile strength and Charpy toughness after the PWHT. A significant variation in microhardness was measured across the welds joint, and peak hardness was measured about 344 HV in the coarse-grained heat affected region while in weld metal it was 263 HV. The peak hardness value in HAZ and variation in hardness also get reduced after the PWHT. In the weld metal, a significant variation in the residual stresses was measured along the thickness with peak magnitude 250 MPa and 172 MPa for longitudinal and transverse stress, respectively in the as-welded condition. A significant reduction in peak residual stresses (longitudinal stress and transverse stress) was obtained after the PWHT. • Study on the effect of Ni-based ERNiCrMo-3 filler on microstructure and mechanical behaviour of the P91 welded joint. • Study on combine effect of the filler and PWHT on mechanical properties of the P91 welded joint. • Measurement of the weld induced residual stresses by using the deep hole drilling method. [ABSTRACT FROM AUTHOR]

In the present study, the effect of using different filler metals on the microstructure, mechanical and corrosion properties of gas tungsten arc welding (GTAW) of S32750 super duplex steel joints has been investigated. Three different filler rods of 316 L, S32202, and S32750 containing different concentrations of ferrite and austenite stabilizer elements were used to fabricate GTAW S32750 joints. From the microstructural studies, it was found that elongated structure of austenitic-ferritic transforms into a dendritic γ-austenite structure within an α-ferrite matrix, when S32202 and S32750 were used. While, the microstructure of sample welded by 316 L was consisted of dendritic δ-ferrite phase in the austenite grain boundaries. Owning the higher percentage of α-ferrite phase, the sample welded by S32202 filler rod showed the highest microhardness and tensile strength. The best combination of tensile strength (826 MPa), ductility (27%) and absorbed energy prior to fracture (51 J) was observed in the sample welded by S32750 filler rod due to the higher percentage of γ-austenite phase or a decrease in the percentage of the α and δ-ferrite phase in the weld microstructure. The Tafel polarization test showed that the highest and lowest corrosion resistance belonged to the samples welded by S32750 and 316 L, respectively. The presence of higher percentage of γ-austenite phase caused an increase in the corrosion resistance of the weld metal, while the presence of higher percentage of α and δ-ferrite caused a significant decrease in the corrosion resistance. ❖ Effects of ferrite and austenite stabilizer elements, on the S32750 super duplex steel GTAW joints have been investigated. ❖ The percentage of austenite in the weld metal was proportional to the weight percentage of Nickel. ❖ The optimum mechanical properties obtained when an equal percentage of ferrite and austenite were observed. ❖ Corrosion resistance was improved as a result of an increase in the concentration of austenite phase. [ABSTRACT FROM AUTHOR]

The paper presents the detailed microstructure study and mechanical behavior of P91 welded joint produced by gas tungsten arc welding process (GTAW) using the dissimilar nickel grade superalloy Inconel 718 filler (ERNiFeCr2). The microstructural changes in the weld fusion zone (WFZ) and heat-affected zone (HAZ) were also studied for varying heat treatment conditions. The effect of the Inconel 718 filler on the tensile properties, hardness and Charpy impact toughness (CIT) of the welded joint was also studied for as-welded and heat-treated conditions. The post-weld heat treatment (PWHT) was performed in a temperature range of 650–1060 °C. The microstructure study showed the formation of an unmixed zone at the interface of the HAZ and weld metal and remain unaffected during the PWHT. The region of weld metal near the boat fusion line showed the cellular and columnar dendrites. The center region of the bulk weld metal was solidified as the columnar dendrites and cellular dendrites along with segregation of the elements at inter-dendritic boundaries. The dendrite core showed the segregation of the Ni, and Cr; however, at dendrite boundaries, major segregation was observed for the elements Nb, Mo and Ti. The heat treatment up to a temperature of 810 °C has observed a negligible effect on the WFZ microstructure; however, a significant change in microstructure was observed for the P91 HAZ region. A significant change in the microstructure of the WFZ was measured after the normalizing at 1060 °C, followed by tempering at 760 °C for 2 h (complex heat treatment). The tensile strength of the welded joint was measured 817 MPa with a joint efficiency of 146% for as-welded condition and a maximum of 901 MPa with a joint efficiency of 161% for complex heat treatment. The welded joint CIT was measured a maximum of 48 J in as-welded condition and get reduced after the PWHT and measured a minimum of 35 J after complex heat treatment. A hardness variation was observed along the welded joint for as-welded and PWHT condition. In the as-welded condition, the hardness of the WFZ was measured about 417 ± 21 HV and showed a minute change with an increase in tempering temperature. The minimum hardness was measured in the inter-critical HAZ region for the as-welded joint and produce a significant level of heterogeneity in hardness variation along the P91 HAZ. PWHT has observed a considerable reduction in the hardness value of the P91 HAZs except for ICHAZ. A negligible level of hardness variation along P91 HAZ was measured after PW 4. • Study the role of dissimilar Ni-based (ERNiFeCr2) filler on solidification behavior of the martensitic/ferritic P91 welded joint. • Study the effect of Ni-based (ERNiFeCr2) filler on mechanical properties of the P91 welded joint. • Study the microstructure and mechanical property relationship for the different heat-treatment conditions of the welded joint. [ABSTRACT FROM AUTHOR]