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Article

Enhancing Welding Productivity and Mitigation of Distortion in Dissimilar Welding of Ferritic-Martensitic Steel and Austenitic Stainless Steel Using Robotic A-TIG Welding Process

by
Tushar Sonar
1,*,
Mikhail Ivanov
1,
Igor Shcherbakov
1,
Evgeny Trofimov
2,
Emiliya Khasanova
1,
Muralimohan Cheepu
3,4 and
Kun Liu
5
1
Department of Welding Equipment and Technology, Institution of Engineering and Technology, South Ural State University (National Research University), Chelyabinsk 454080, Russia
2
Department of Materials Science, Physical and Chemical Properties of Materials, Institution of Engineering and Technology, South Ural State University (National Research University), Chelyabinsk 454080, Russia
3
Research and Development, Vitzronextech Co., Ltd., Ansan 15603, Republic of Korea
4
Department of Materials System Engineering, Pukyong National University, Busan 48547, Republic of Korea
5
School of Materials Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212100, China
*
Author to whom correspondence should be addressed.
J. Manuf. Mater. Process. 2024, 8(6), 283; https://doi.org/10.3390/jmmp8060283
Submission received: 3 November 2024 / Revised: 3 December 2024 / Accepted: 4 December 2024 / Published: 5 December 2024
Browse Figures
Versions Notes

Abstract

:
The P91 martensitic steel and 304L austenitic stainless steels are two mainly used structural steels in power plants. The major problem in conventional multipass tungsten inert gas (TIG) welding of P91/304L steel is high heat input and joint distortion, increased cost and time associated with V groove preparation, filler rod requirement, preheating and welding in multiple passes, and labor efforts. Hence, in this study, a novel approach of robotically operated activated flux TIG (A-TIG) welding process and thin AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA) sheet as the interlayer was used to weld 6.14 mm thick P91 and 304L steel plates with 02 passes in butt joint configuration. The joints were qualified using visual examination, macro-etching, X-ray radiography testing and angular distortion measurement. The angular distortion of the joints was measured using a coordinate measuring machine (CMM) integrated with Samiso 7.5 software. The quality of the A-TIG welded joints was compared to the joints made employing multipass-TIG welding process and Inconel 82 filler rod in 07 passes. The A-TIG welded joints showed significant reduction in angular distortion and higher productivity. It showed a 55% reduction in angular distortion and 80% reduction in welding cost and time compared to the multipass-TIG welded joints.

1. Introduction

The P91 ferritic-martensitic steel (FMS) and 304L austenitic stainless steel (ASS) are two mainly used structural materials in thermal power stations owing to their outstanding mechanical properties and corrosion resistance [1,2]. The P91 steel mainly contains 1% molybdenum (Mo), 0.05% niobium (Nb), 0.25% vanadium (V), 9% chromium (Cr) and a small amount of other elements [3,4]. The application of P91 steel is recommended at increased temperatures between 610 and 630 °C [5,6]. The 304L is the 300 series grade of ASS often utilized in elevated temperature and severe corrosive applications of thermal power plants [7,8]. The 304L steel has an alloying composition of 8–12% Ni, 18–20% Cr and 0.03% C [9,10]. The 304L steels are recommended for elevated temperature conditions in power generation industries up to 450–550 °C [11,12]. The primary purpose of DMW of P91/304L steel is to combine the higher creep endurance strength of low-cost P91 steel with superior corrosion resistance of high-cost 304L steel [13,14]. The P91 steel is employed on a comparatively lower temperature and less corrosive side, such as for developing the different sections of boilers, pressurizers, main steam headers and steam generators. The 304L steel is utilized for applications such as for steam carrying pipes and tubes of heat exchanges and end sections of superheaters and reheaters [15,16,17]. The structural sections made of P91 steel are required to be welded with the pipes and components made of 304L steel to complete the power generation circuit. The dissimilar joints of P91 and 304L steel are needed to perform safely at 450–550 °C [18].
Since the P91 and 304L steel have different alloying compositions, metallurgical characteristics and mechanical and physical properties, welding them together to develop sound and defect-free joints is extremely difficult. The dissimilar welds of P91/304L steel are susceptible to the issues of hot cracking, cold cracking, distortion and premature joint failure due to the generation of detrimental unsymmetric tensile residual stresses in joint assembly [19]. The DMW of P91/304L steel is done by employing manual multipass tungsten inert gas (TIG) welding and Inconel-based filler rods such as Inconel 82 [20,21,22], Inconel 718 [23] and Inconel 625 [24,25,26] filler rods to minimize the issues of cracking and develop clean and good quality joints compared to manual metal arc welding (MMAW) and metal inert gas welding (MIG) [19]. In multipass-TIG welding, the joining side of base metal plates are beveled to form a V-groove with a 60–75° included angle. The V-groove is then filled with weld metal (WM) in the number of passes depending on the plate thickness to be joined [27]. However, the multipass-TIG welding has some issues, such as porosity in WM due to the entrapment of shielding gases, lower joint penetration, higher heat input, very slow weld traverse speed, special edge preparation before welding, interpass heating and a greater number of welding passes. Hence, there is more consumption of welding power, filler rods, shielding gases such as argon and preheating flame gas such as propane. This increases the welding time, cost and labor efforts and subsequently lowers the welding productivity [28].
The activated flux-TIG (A-TIG) welding is successfully employed by researchers for DMW of the thick plates of FMS and ASS [29,30,31]. It involves the application of a thin layer of different fluxes (oxides of silicon—SiO2, titanium—TiO2, chromium—Cr2O3, molybdenum—Mo2O3 or a mixture of these oxides) coating over the joint surface before welding for constricting the welding arc [32,33]. It offers the advantages of two to three times increased joint penetration, single pass welding, no edge preparation, lower heat input, deep narrower weld and increased weld traverse speed [34]. Huang et al. [35] reported that the hot cracking issue in 304 steel joints was reduced by employing A-TIG welding due to the increasement in the residual δ-ferrite phases. The angular distortion of weldments was reduced by A-TIG welding due to the lower input of heat. Vidyarthy et al. [36] welded P91 and 316L steel plates of 12 mm thickness employing A-TIG welding in one pass without filler using a combination of 10% CuO, 35% TiO2, 40% SiO2 and 15% NiO fluxes. Sharma and Dwivedi [37] fabricated the dissimilar joints of 8 mm thick P92 and 304H steel in a single pass employing A-TIG welding (TiO2 flux) compared to multipass-TIG welded joints, which required eight welding passes of Inconel 82 filler rod. The A-TIG welded joints showed lower angular distortion than multipass-TIG welded joints due to the reduced number of welding passes and overall heat input. Kulkarni et al. [38] observed that the strength of the P91 and 316 steel joints fabricated by employing A-TIG welding can be enhanced without compromising on toughness and ductility by using Inconel-based interlayers. The A-TIG welded joints of P91 and 316L steel welded with Incoloy 800 interlayers showed 98% joint efficiency. It showed 41.37% and 196% improvement in ductility and toughness of the interlayered joints than the A-TIG welded joints made without an interlayer. The interlayer also reduced the severity of carbon diffusion.
The problems in DMW of P91/304L steel can be overcome by using the fillers that exhibit a higher nickel content, sluggish atomic diffusion and higher mixing entropy. This can be achieved using the high entropy alloy (HEA). The HEA is fabricated by melting equal or larger proportions of 05 or additional alloying elements in the range of 5 to 35 at. % [39]. The HEAs exhibit superior tensile properties, corrosion and oxidation resistance at room, elevated and cryogenic temperature ranges due to its excellent microstructural stability at different temperature ranges compared to conventional alloys [40]. It is principally attributed to its sluggish atomic diffusion, extreme lattice distortion, higher mixing entropy and combined effects. The investigation is focused on the CoCrFeMnNi and AlCoCrFeNiTi HEAs, which have single-phase FCC and BCC structures separately. The application of a single-phase HEA is limited in the engineering sector, and hence, there is a need for dual-phase HEA to offer higher strength and elongation [41]. The AlCoCrFeNi2.1 is an eutectic two-phase FCC (L12) and BCC (B2) lamellar structured HEA that has gained major attention from the industrial sector recently because of its excellent mechanical properties, thermal stability and creep strength at elevated temperatures and greater hot corrosion resistance in severe environments [42,43]. The eutectic HEA (E-HEA) offers a promising approach to gain the ideal combination of strength–ductility, because it combines the higher strength of the BCC phase with the higher elongation of the FCC phase [44]. The success of using HEAs in welded structures depends, to a large extent, on their weldability. It has been proven that it is possible to fabricate the similar and dissimilar joints of HEAs with traditional engineering alloys, which increases their demand in the structural section of advanced industrial units [45,46]. Furthermore, it has been shown that the fillers and interlayers of HEAs have more potential to enhance the joint performance and prevent the development of detrimental intermetallic phases [47,48,49].
Welding of the boiler and pressure vessel sections is critical to ensure their structural integrity and safety. Hence, the welded plates of FMS and ASS must be free from the defects of undercuts, blow holes, inclusions, porosities, cracking and partial penetration [50,51]. Hence, the welded joints must be qualified following ASME BPVC section IX standards. The DMW of P91/304L steel is carried out by either employing multipass-TIG welding with Inconel-based filler wires or A-TIG welding. The research work related to the application of the EHEA interlayer in the DMW of P91/304L steel employing A-TIG welding has not been reported so far. There is a lack of systematic investigation on the weld qualification using visual inspection, X-radiography, defect analysis and distortion analysis of dissimilar P91 and 304L steel joints. The economic assessment of A-TIG and multipass TIG joints of P91 and 304L steel has been reported in very few investigations. Therefore, the primary purpose of this work is to develop the dissimilar joints of P91/304L steel employing A-TIG welding and AlCoCrFeNi2.1 E-HEA as the interlayer. This study aims to increase welding productivity and reduce the distortion, and the cost associated with welding time and manufacturing in thermal power plants.

2. Materials and Methods

2.1. Material Selection

The P91 and 304L steel plates of 6.14 mm thickness were chosen as parent metals for this study. The P91 steel was accepted in heat treatment conditions of normalizing and tempering. The 304L steel was accepted in a solutionized state. The chemical composition of P91 and 304L steel was analyzed using a spark spectrometer. The P91 and 304L steel plates were confirmed as ASME SA387 grade 91 class 2 and ASTM A240 Type 304L (HR) standards, respectively. The chemical composition of the P91 and 304L steel plates, Inconel 82 filler rod and AlCoCrFeNi2.1 EHEA interlayer are presented in Table 1. The mechanical properties of P91 and 304L steel plates are presented in Table 2. The thin 1.50 mm thick sheet of AlCoCrFeNi2.1 EHEA was used as an interlayer in A-TIG welding of P91/304L steel. The EHEA was prepared by mixing the buttons of pure Al, Co, Cr, Fe and Ni in induction with melting the vacuum furnace. The molten mixture was poured into a rectangular ceramic mold of size 120 × 65 × 20 mm3. The cast EHEA block was machined using a milling machine to the size of 100 × 60 × 15 mm3. The thin sheets (1.5 mm thick) of EHEA were sliced from the cast block using a wire cut electro discharge machine. The sheets of EHEA were subjected to solutionizing at 1000 °C for 2 h and were water-quenched. The sheets were then further aged at 780 °C for 8 h. For multipass-TIG welding of P91/304L steel, the Inconel-82 filler rods with a diameter of 1.6 mm and length of 1000 mm were chosen that conformed to the AWS A5.14 ErNiCr-3 and ASME SFA 5.14 Section II part C 2017 standards.

2.2. Fabrication of Welded Joints

The robotically operated TIG welding machine was used for A-TIG welding of P91/304L steel using the EHEA interlayer. The TIG welding torch was mechanically clamped to the robotic arm. The x-y-z position of the robotic arm can be controlled using the programming module. The manually operated TIG welding machine was used for multipass-TIG welding of P91 and 304L steel plates using the Inconel 82 filler rod. The preheating was performed using flame torch and gas cylinder arrangement. The preheating and interpass temperatures of the plates were measured using laser infrared thermometer gun. Figure 1 and Figure 2 show the schematic and pictures of the butt joint configuration and V-groove joint configuration for A-TIG welding and multipass-TIG welding of P91 and 304L steel. The pictures of the experimental setup and equipment utilized in this investigation are shown in Figure 3. The picture of the arrangement of the P91 and 304L steel plates in fixtures for A-TIG welding and multipass-TIG welding is shown in Figure 4. The procedure of the fabrication of the joints is detailed below. A total of three A-TIG joints and three multipass-TIG joints were fabricated from the optimized parameters without the defects of cracks and porosity.

2.2.1. A-TIG Welding of P91/304L Steel Using an AlCoCrFeNi2.1 EHEA Interlayer

The butt joint design was selected in the DMW of P91/304L steel employing A-TIG welding and an EHEA interlayer. The machining of welding surfaces of P91 and 304L steel plates was done using vertical grinding machining. The welding surfaces were made flat. The surface near to the joining edge up to 10 mm wide was finished using a hand-grinding machine. The plates of P91 and 304L steel were positioned flat in the 1G position and were separated by 1.5 mm distance. The thin 1.5 mm thick strip of AlCoCrFeNi2.1 EHEA was kept in between them. The joint arrangement was mechanically clamped, and the ends of the plates and EHEA interlayer were tack welded on both sides for fixing its position. The butt joint assembly was mechanically clamped in the fixture using nuts and bolts. To attain deeper penetration in A-TIG welding of P91/304L steel, powder of Titanium oxide flux at the size of 50 µm was used. The flux powder was first dried in the furnace at 150 °C for 15 min to remove the moisture content. The flux powder was then mixed with ethyl alcohol for forming a paste. The paste of flux was then applied by paint brush over the butt region to be welded on the front and back sides of the weld assembly for a width of 20 mm covering the surface of P91 and 304L steel near the HEA interlayer. The butt joint assembly was preheated at 250 °C for 30 min. The trajectory of the welding path was set up on the monitor, and the program was made for the welding of P91 and 304L steel plates at the preset weld traverse speed. The tungsten electrode (2% thoriated) was used in this investigation. The tip angle of the tungsten electrode was set at 60°. Several trials were done to set the welding parameters. The process parameters giving the higher depth of penetration were chosen as the optimal welding parameters. The A-TIG welding was performed on the front and back sides of the weld assembly to fabricate the joints using the optimal welding parameters to attain full penetration. The welding should be performed carefully, since the dissimilar joints of P91/304L steel are susceptible to hot cracking, cold cracking, porosity and incomplete penetration-related defects. Table 3 shows the optimal welding parameters used for the DMW of P91/304L steel employing A-TIG welding and an EHEA interlayer. The joints were then post-heated to a temperature of 250 °C to minimize the issues of cracking and distortion. The joints were then cooled to room temperature and removed from the fixture.

2.2.2. Multipass-TIG Welding of P91/304L Steel Using an ErNiCr-3 Filler Rod

The V-groove joint design with an angle of 60° was selected for multipass-TIG welding of P91/304L steel. The machining of the welding surfaces of the P91 and 304L steel plates to a beveled angle of 30° and 1.5 mm root height was done using a milling machine. The plates of P91 and 304L steel were set in a V-groove joint configuration, and a 1.5 mm root gap was maintained between the plates. The ends of the P91 and 304L steel plates were tack welded for fixing its position. The tack welded P91/304L steel plates were then clamped mechanically in the fixture using nuts and bolts. The tack welded P91/304L steel plates were then preheated to the temperature of 250 °C for 30 min. The preheating temperature of the plates was measured using an infrared thermometer gun. The P91/304L steel plates were then welded for a total of 07 passes manually using multipass-TIG welding and ErNiCr-3 filler rods. The 01 root pass was performed at a higher level of welding current to ensure complete joint penetration followed by 06 filling passes in the DMW of P91/304L steel plates. The filling passes were done at a comparatively lower level of welding current. The interpass temperature of 180–250 °C was kept during multipass-TIG welding. The joints were post-heated to a temperature of 250 °C to minimize the issues of cracking and distortion. The joints were then cooled to room temperature and removed from the fixture.

2.3. Qualification of the Welded Joints

The 02 A-TIG and 02 multipass-TIG joints were subjected to visual inspection and radiographic testing after 48 h. The visual inspection was carried out with naked eyes for the surface finish, macro-level surface cracks, porosities, etc. The macro-etching test sample of size 40 × 15 × 6.14 mm3 was cut from the joint for the macro-etching test. The cross-section of the macro-etching test samples was subjected to standard mirror polishing. The mirror polished metallographic samples of the welded joints were etched using marbles reagent to revel the joint penetration depth, WM area and width of HAZ. The joints were subjected to X-ray radiographic testing in the horizonal position to identify the weld defects such as incomplete joint penetration, undercuts, cold laps, presence of internal cracks, porosities, etc. The X-radiography testing was done with film as per the ISO 17636-1 class-A standards [52]. A picture of the radiographic testing machine is displayed in Figure 5. The X-ray radiographic film was carefully analyzed following the ASME BPVC section IX standard.

2.4. Distortion Measurement

The angular distortion of the joints was evaluated using a coordinate measuring machine. In all the conditions, the A-TIG joints exhibited lower angular distortion than multipass-TIG joints. The quantitative distortion test using the coordinate measuring machine was performed on the 01 A-TIG joint and 01 multipass-TIG joint, showing higher distortion. The test was conducted at 03 different locations, and the average of 03 is reported as the final reading. The picture of the coordinate measuring machine setup is shown in Figure 6. The measuring positions were marked as lines on the P91/304L steel joints at three different positions on P91 and 304L steel. The reference coordinates were first set by touching the probe on the flat reference plate. The welded joints were kept on the reference plate, and the probe was moved along the reference lines marked on the welded joints. The probe was moving along the line from P91 steel to the weld center and then to the 304L steel. The measuring lines were marked at the initial, middle and end surfaces of the welded joints. The schematic showing the location of the probe touching points on the welded joints for the distortion measurement is given in Figure 7. The tracing lines were recorded in the 3D model, and the angle of distortion was measured with reference to the flat surface using Samiso 7.5 software. The picture showing the 3D tracing lines is shown in Figure 8.

3. Results

3.1. Visual Inspection

Visual inspection was carried out to verify the integrity of the fabricated joints. Prior to radiographic testing, accessible parts of joints were assessed and visually checked as per the ISO 17637 standard [52]. The pictures of the top and bottom surfaces of the P91/304L steel joints fabricated employing A-TIG and multipass-TIG welding are presented in Figure 9 and Figure 10. The acceptance levels for a visual inspection of the joints as per the ISO 6520-1 standard are given in Table 4 [53]. The joints welded employing A-TIG and multipass-TIG welding were qualified for acceptance level 1. The joints were visually inspected by naked eye for weld defects and discontinuities such as surface cracks, surface porosities, undersized welds, overlap, excessive root penetration, incomplete root penetration, excessive reinforcement, underfill and undercuts. The A-TIG and multipass-TIG joints were sound- and defect-free in the visual inspection. The joints welded employing A-TIG welding and the EHEA interlayer showed the rough weld bead surface and the formation of a keyhole at the end section of the joints. This mainly refers to the sluggish fluidity of molten WM due to the addition of EHEA as the interlayer. However, the defects of cold laps were not noticed in the X-ray radiographs. The joints welded employing multipass-TIG welding showed smooth weld beads with a number of ripples formed during welding. The addition of filler metal in multiple passes offers better fluidity of molten WM due to the tempering effect of the weld bead. A minor porosity was observed in both types of welded joints. However, the porosity formation in the joints made employing A-TIG welding and the EHEA interlayer was comparatively more compared to the joints made employing multipass-TIG welding and Inconel 82 filler wire. This mainly refers to the loss of aluminum from the EHEA during welding. The Al evaporates during welding in A-TIG welding because of the high input of heat and its lower boiling point. The sluggish viscosity of molten WM due to the addition of EHEA also results in entrapment of the gases released from the melting of EHEA and shielding gases. This results in minor porosity issues in A-TIG welding of P91/304L steel using EHEA as the interlayer. However, these issues can be overcome by optimization of the weld traverse speed. The porosity formation in these joints is much lower (<1% for 100 mm length) than the acceptance limit (<2.5% for 100 mm length) as per the ISO 6520-1 standard [53].
The in-process inspection was also carried out during the fabrication of welded joints to obtain good quality joints. The joints welded employing multipass-TIG welding showed the solidification cracking in the WM region after the root pass and third pass of the weld. The crack was formed at the centerline of the weld running longitudinally along the weld. The picture showing the solidification cracks in WM of the joints welded employing multipass-TIG welding is displayed in Figure 11. The dissimilar joints of P91/304L steel are susceptible to hot cracks during welding due to the differences in the TEC and k of the base metals. The Inconel and Ni-based fillers (Inconel 82 and 625) are utilized to minimize the issues of hot cracking in the DMW of P91/304L steel. However, the hot cracking can be observed due to the higher overall heat input in multipass-TIG welding. The interpass temperature is also required to be maintained in the range of 180–250 °C to minimize the issue of cold cracking in multipass-TIG welding. The joints welded employing the A-TIG welding did not show any tendency of hot cracking during welding because of the lower overall heat input than multipass-TIG welding. The AlCoCrFeNi2.1 EHEA is featured by the higher mixing entropy and extreme lattice distortion. These characteristics of the EHEA may also be responsible for the reduced hot cracking tendency of the joints. Furthermore, there is no need to control the interpass temperature during welding in A-TIG welding, as is required in multipass-TIG welding. This reduces the cold cracking tendency of joints employing A-TIG welding.

3.2. Macrostructure

The macrostructure of the joints welded employing A-TIG and multipass-TIG welding is displayed in Figure 12. The joints were observed to be free of weld defects, including porosity, inclusions, internal cracks and partial penetration. The macrostructure of the joints welded employing A-TIG welding displayed the good solidification of EHEA as the filler with the P91 and 304L steel BMs. The joints were welded in a double pass employing A-TIG welding for obtaining the full joint penetration. The macrostructure of the joints welded employing multipass-TIG welding displayed that the ErNiCr-3 filler exhibited good melting and solidification with the P91 and 304L steel. The joints were welded in a total of seven passes, including one root pass, five filling passes and one cap pass, in multipass-TIG welding to fill the filler metal in the V-groove region of the joints. The width of HAZ was observed to be narrower in 304L steel sides of joints whereas it was wider in P91 steel sides of joints welded employing A-TIG and multipass-TIG welding. This is because of the lower k of 304L steel (16.20 W/m⋅K) than P91 steel (25 W/m⋅K). The HAZ width was measured at four different locations. The macrographs showed that the joints welded employing A-TIG welding showed HAZ widths up to 8.52 mm, whereas the joints welded employing multipass-TIG welding showed HAZ widths up to 5.11 mm on P91 steel sides of the joints, respectively. The joints welded employing A-TIG welding exhibited 66.73% wider HAZ widths on the P91 steel side of the joints than the joints welded employing multipass-TIG welding. This is due to the higher input of heat in a single pass (1.404 kJ/mm) of A-TIG welding compared to a single pass (root pass: 0.946 kJ/mm and filling pass: 0.624 kJ/mm) of multipass-TIG welding.
The macrostructure of joints fabricated employing the A-TIG welding and EHEA interlayer in a single pass is displayed in Figure 13. When the A-TIG welding was made in one pass employing the current of 210 A and traverse speed of 70 mm/min, the P91 steel side of the joints displayed joint penetration up to 5.01 mm, whereas the 304L steel side of the joints displayed joint penetration up to 3.83 mm. Therefore, the optimal process parameters were set as a current of 210 A and traverse speed of 70 mm/min that show complete joint penetration in two passes. The EHEA showed the solidification gradient in the WM region due to the differences in the melting and solidification of P91 and 304L steel. Hence, the second pass was performed on the back side of the joints to obtain complete joint penetration. Thus, the joints were fabricated in a double pass employing A-TIG welding and the EHEA interlayer for obtaining full joint penetration. The defects observed during the trials for A-TIG welding of P91/304L steel using an EHEA interlayer are shown in Figure 14. When the current was increased to 220 A while maintaining a traverse speed at 70 mm/min, the defect of weld burn through was observed. Similarly, when the weld traverse speed was decreased to 60 mm/min while maintaining the current at 210 A, the defect of weld burn through was observed. This mainly refers to the high heat input and arc force.

3.3. X-Ray Radiography

The radiographic films of the joints welded employing A-TIG welding and multipass-TIG welding are shown in Figure 15. The radiographic films were analyzed for their acceptance level following the ISO 6520-1 standard [53]. The acceptance levels are essentially valid for assessing the surface and subsurface defects such as undercuts, microcracks and porosities on the surface, internal cracks and porosities that cannot be found or assessed by visual inspection. In accordance with ISO 5817 [54], the IIW Reference radiographs were utilized to evaluate the weld defects. Table 5 shows the acceptance criteria and levels for weld defects in the joints welded employing A-TIG and multipass-TIG welding. The results showed that the joints employing A-TIG and multipass-TIG welding were qualified for acceptance level 1 criteria as per the ISO 17636-1 standard [55]. Thus, the welded joints were proven to be sound and of good quality.

3.4. Angular Distortion

The angular distortion of the joints was measured precisely, as shown in Figure 16. The angular distortion measurement of the joints is reported in Table 6. The results showed that the joints welded employing multipass-TIG welding showed a higher angular distortion up to 1.17° and mean angular distortion up to 1.15°. The joints welded employing A-TIG welding showed a lower angular distortion up to 0.86° and mean angular distortion up to 0.51°. Thus, the angular distortion of the joints was minimized by 55% employing A-TIG welding due to the lower overall heat input (2.80 kJ/mm) compared to multipass-TIG welding (4.69 kJ/mm). The distortion of the 304L steel side was observed to be higher compared to the P91 steel side of the welded joints. This is because of the higher TEC of 304L steel up to 18.0 × 10−6 °C compared to that of P91 steel up to 13.5 × 10−6 °C. Figure 17 shows the picture of the joints welded employing multipass-TIG welding. The joints showed higher angular distortion up to 9°. During the welding of P91/304L steel plates, strong clamping is necessary. Multipass-TIG welding involves higher overall heat input and filling of WM in the V-groove at several passes, resulting in repeated heating and cooling cycles. A larger volume of molten and solidified WM in multipass-TIG joints results in greater stresses after cooling, leading to larger distortions. The distortion of joints was observed to be strong enough to break the weld of the clamping bolt.

3.5. Economic Assessment of the Fabricated Joints

The improved economics, including the cost and time required for the fabrication of joints, are prerequisites for the power plants. The cost of the fabrication of dissimilar joints of P91/304L steel involves the cost of labor, welding consumables (shielding gases and filler rods), edge preparation of joining plates, preheating flame gas and welding power consumption. The cost of the fabrication of the joints was determined based on the expenses incurred in making the joints employing A-TIG and multipass-TIG welding, respectively. The cost of fabrication of the joints may differ based on the location and market. The cost of fabrication of joints employing A-TIG and multipass-TIG welding is shown in Table 7. The cost of labor is higher in employing A-TIG and multipass-TIG welding of P91/304L steel. The labor cost is reduced in A-TIG welding by 80% compared to multipass-TIG welding due to the reduced welding time. The economic assessment of the joints is shown in Figure 18. The welder, filler rod, groove machining, preheating flame, shielding gases and welding power consumption costs contribute 53.7%, 25.8%, 9.7%, 6.2%, 4.4% and 0.1% of the total cost of the fabrication of joints employing multipass-TIG welding. The welder cost is higher in fabricating the joints employing multipass-TIG welding and an Inconel 82 filler rod, since the welding time is increased due to the number of welding passes and a highly skilled welder is required to make the dissimilar joints of P91/304L steel. The welder, preheating flame, EHEA interlayer, shielding gases and welding power consumption cost contribute 28.6%, 23.8%, 19%, 14.3%, 26.7% and 4.8% of the total cost of the fabrication of joints employing A-TIG welding. The total cost of the fabrication of joints is minimized by 80% employing A-TIG welding compared to multipass-TIG welding. This mainly refers to the reduced welding and no requirement of filler metal and edge preparation in A-TIG welding. A highly skilled welder is not required to fabricate dissimilar joints employing robotically operated A-TIG welding.
The A-TIG welding involves welding plates in a single pass on the front and back sides, respectively. Thus, the P91 and 304L steel plates of 6.14 mm thickness were welded in two passes employing A-TIG welding. The multipass-TIG welding involves seven welding passes in making the joint. The plates were welded in a total of 2 min employing the robotically operated A-TIG process, whereas the plates were welded in a total of 10 min employing manually operated multipass-TIG welding. The welding time required of the fabrication of joints is minimized by 80% employing A-TIG welding compared to the multipass-TIG welding.

4. Discussion

The P91 and 304L steel plates were welded successfully employing A-TIG welding and AlCoCrFeNi2.1 eutectic HEA as the interlayer. The joints were welded on the front and back sides of the weld. The A-TIG welding showed full joint penetration in the welding of stainless-steel plates up to 12 mm thick in a single pass. Sharma and Dwivedi [25] fabricated dissimilar joints of FMS and ASS steel of 8 mm thickness using TiO2 flux without an interlayer at a current of 220 A, traverse speed of 80 mm/min and a heat input of 2.39 kJ/mm. In the present study, complete penetration was not obtained in the DMW of P91/304L steel of 6.14 mm thickness employing A-TIG welding and EHEA in a single pass when welded at different parametric combinations of welding currents of 180–220 A and weld traverse speeds of 40–80 mm/min. The highest joint penetration was observed when the joints were welded using the current of 210 A, traverse speed of 70 mm/min and heat input of 2.52 kJ/mm. This mainly refers to the increased viscosity of molten WM because of the addition of the EHEA interlayer. During welding, the EHEA mixes with P91 and 304L steel. This increases its viscosity and results in a sluggish fluidity of molten WM. The arc loses its stiffness while passing through the viscous molten WM and reduces its joint penetration. This necessitates an increased arc force and heat input at an optimum level. This is achieved by the optimum current of 210 A and traverse speed of 70 mm/min, which offers higher joint penetration up to 5.01 mm on the P91 steel side and 3.00 mm on the 304L steel side. The EHEA interlayer showed a solidification gradient after the first pass of welding. The greater joint penetration was noted on the P91 steel side, and lower joint penetration was observed on the 304L steel side. The 304L steel also has issues of joint penetration due to the addition of more alloying elements, which results in sluggish fluidity of the molten WM. The addition of EHEA further increases its viscosity and results in a sluggish fluidity of molten WM on the 304L steel side. This results in lower joint penetration on the 304L steel side compared to the P91 steel side of the joints. To overcome, the issues of incomplete and nonuniform joint penetration in A-TIG welding of P91/304L steel using EHEA as the interlayer, the plates were welded on both the front and back sides, respectively. Thus, the A-TIG welding of P91/304L steel using an EHEA interlayer was performed in two passes.
The keyhole formation observed on the end section of the joints welded employing A-TIG welding was due to the increased arc force, constriction of the arc and reversed Marangoni effect. The joints made employing the A-TIG welding and EHEA interlayer show a keyhole formation at the end section of the joints. A keyhole formation is a characteristic feature of deeper penetration attained by A-TIG welding. A deeper penetration was seen in the A-TIG joints. The mechanics of deeper penetration in A-TIG welding is well explained by previous researchers [28,32]. Figure 19 presents the mechanism of deeper joint penetration achieved in A-TIG welding in the presence of flux and shallower penetration in TIG welding without flux. The deeper penetration in A-TIG welding is attributed to the flux-assisted constricted arc and reversal of the Marangoni effect because of a change in the surface tension (ST) of molten WM. As per the Marangoni effect, the WM flow occurs from the lower ST region to higher ST region. In conventional TIG welding, the temperature coefficient of ST (δρ/δT) is negative (−ve). The central region of the weld with molten WM exhibits lower ST due to the higher temperature, whereas the surrounding base metal region exhibits higher ST due to the lower temperature. Thus, the molten WM flow takes place following the Marangoni effect from the central region of the WM having a lower ST in the outward direction to the surrounding region of solid base metal having a higher ST. This results in greater heat transfer to the surrounding area of molten WM than the WM center, leading to a wider weld bead width and lower joint penetration in conventional TIG welding. In A-TIG welding, the TiO2 flux dissociates, leading to the higher O-content in molten weld pool and the formation of nano-thin film of the metal oxide. However, as the temperature increases in the central region of molten WM, the oxygen dissociates due to the greater configurational entropy at high temperatures. This results in an increase in the ST of molten WM at the center and changes the δρ/δT from −ve to +ve. Thus, it changes the molten WM flow direction from the outward region to the inward region. This is the reversal of the Marangoni effect. The inward flow of molten WM results in a downward flow in the center of the weld pool. This increases the heat transfer by convection and melting the WM in a downward direction, leading to deeper joint penetration in a single pass. This mechanism is mainly related to the fluxes that ensues oxygen during melting, as per Sandor et al. [56]. The welding arc is constricted by the electrical resistive flux coating. This reduces the heat loss of the welding arc on the outer flare of the TIG arc to the surrounding environment.
Due to the presence of flux, the density of charged particles also increases in the constricted TIG welding arc. This enhances the energy density of the welding arc. As the TIG-arc is constricted and the density of the charged particles is increased due to the dissociation of the flux, the unit area of the workpiece stroked by the number of charged particles striking per increase. This results in deeper penetration of the joints. In conventional TIG-welding, the arc is wider and has a bell-shaped profile. There is greater heat loss from the wider TIG arc to the surrounding atmosphere and on the outer flare. The wider TIG arc minimizes the density of the charged particles striking per unit area of the workpiece. This results in shallower penetration of the joints.

5. Conclusions

The 6.14 mm thick plates of P91 and 304L steel were welded successfully in two passes employing a robotically operated A-TIG welding process and AlCoCrFeNi2.1 EHEA as the interlayer without any issues of weld defects. The A-TIG joints qualified the acceptance level 1 criteria for visual inspection and radiographic testing as per the ISO 6520-1 standard. This proves the good weldability of EHEA in fabricating the dissimilar joints of P91 and 304L steel.
The angular distortion of the joints was significantly minimized by 55% employing a robotically operated A-TIG welding process due to the lower overall heat input compared to the manually operated multipass-TIG welding process.
The total cost of fabrication of the joints was significantly minimized by 80% employing the robotically operated A-TIG process and EHEA interlayer compared to the manually operated multipass-TIG welding and Inconel 82 filler wire. This mainly refers to the reduced welding time, labor efforts, no requirement of filler metal and edge preparation in the A-TIG welding process.
Thus, the modified approach of robotic A-TIG welding and the EHEA interlayer used for fabricating the dissimilar joints of P91 and 304L steel increases the welding productivity and reduces the distortion and manufacturing cost.

Author Contributions

Conceptualization, T.S.; methodology, T.S.; software, T.S. and M.I.; validation, T.S., M.I. and E.T.; formal analysis, T.S., M.I., I.S., E.T., E.K., M.C. and K.L.; investigation, T.S., M.I., I.S., E.T., E.K., M.C. and K.L.; resources, T.S., M.I., E.T. and I.S.; data curation, T.S.; writing—original draft preparation, T.S.; writing—review and editing, T.S., M.I., I.S., E.T., E.K., M.C. and K.L.; supervision, T.S., M.I. and E.T.; project administration, T.S.; funding acquisition, T.S. All authors have read and agreed to the published version of the manuscript.

Funding

This research work is funded by the Russian Science Foundation (RSF) under the scheme of Conducting fundamental scientific research and exploratory scientific research by small individual scientific groups—regional competition (Grant No. 24-29-20141). Grant recipient: Tushar Sonar.

Data Availability Statement

The authors confirm that the data supporting the findings of this study are available within the article.

Conflicts of Interest

Muralimohan Cheepu is employed by Research and Development, Vitzronextech Co., Ltd. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Figure 1. Schematic representation of the joint configuration for DMW of P91/304L steel: (a) butt joint configuration for A-TIG welding and the EHEA interlayer; (b) V-groove joint configuration for multipass-TIG welding and Inconel 82 filler wire.
Figure 1. Schematic representation of the joint configuration for DMW of P91/304L steel: (a) butt joint configuration for A-TIG welding and the EHEA interlayer; (b) V-groove joint configuration for multipass-TIG welding and Inconel 82 filler wire.
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Figure 2. Pictures of the joint configuration for dissimilar welding of P91 and 304L steel: (a) butt joint configuration for A-TIG welding and the EHEA interlayer; (b) V-groove joint configuration for multipass-TIG welding and Inconel 82 filler wire.
Figure 2. Pictures of the joint configuration for dissimilar welding of P91 and 304L steel: (a) butt joint configuration for A-TIG welding and the EHEA interlayer; (b) V-groove joint configuration for multipass-TIG welding and Inconel 82 filler wire.
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Figure 3. Picture of the experimental equipements and device: (a) robotic arm; (b) welding machine; (c) cntroller unit and programming module; (d) preheating flame torch and gas cylinder; (e) laser infrared gun.
Figure 3. Picture of the experimental equipements and device: (a) robotic arm; (b) welding machine; (c) cntroller unit and programming module; (d) preheating flame torch and gas cylinder; (e) laser infrared gun.
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Figure 4. Picture of the joint setup for DMW of P91/304L steel employing: (a) A-TIG welding and EHEA interlayer, and (b) multipass-TIG welding and Inconel 82 filler rod.
Figure 4. Picture of the joint setup for DMW of P91/304L steel employing: (a) A-TIG welding and EHEA interlayer, and (b) multipass-TIG welding and Inconel 82 filler rod.
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Figure 5. Picture of the experimental setup for (a) the X-ray radiographic testing machine and (b) radiographic films.
Figure 5. Picture of the experimental setup for (a) the X-ray radiographic testing machine and (b) radiographic films.
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Figure 6. Picture of the coordinate measuring machine for measurement of the angular distrotion of the welded plates.
Figure 6. Picture of the coordinate measuring machine for measurement of the angular distrotion of the welded plates.
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Figure 7. Schematic of the measurement of the distortion of the joints.
Figure 7. Schematic of the measurement of the distortion of the joints.
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Figure 8. Picture of the Samiso 7.5 software view of 3D tracing lines for measurement of the distortion of the joints.
Figure 8. Picture of the Samiso 7.5 software view of 3D tracing lines for measurement of the distortion of the joints.
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Figure 9. Picture of the dissimilar joints of P91/304L steel fabrciated employing the A-TIG welding process and EHEA interlayer: (a) top surface of the joint, and (b) bottom surface of the joint.
Figure 9. Picture of the dissimilar joints of P91/304L steel fabrciated employing the A-TIG welding process and EHEA interlayer: (a) top surface of the joint, and (b) bottom surface of the joint.
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Figure 10. Picture of the dissimilar joints of P91/304L steel fabrciated employing the multipass-TIG welding process and Inconel 82 filler rod: (a) top surface of the joint, and (b) bottom surface of the joint.
Figure 10. Picture of the dissimilar joints of P91/304L steel fabrciated employing the multipass-TIG welding process and Inconel 82 filler rod: (a) top surface of the joint, and (b) bottom surface of the joint.
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Figure 11. Picture of the hot cracking observed in the DMW of P91/304L steel employing the multipass-TIG welding process and Inconel 82 filler rod.
Figure 11. Picture of the hot cracking observed in the DMW of P91/304L steel employing the multipass-TIG welding process and Inconel 82 filler rod.
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Figure 12. Macrostructrue of the dissimilar joints of P91/304L steel welded employing (a) A-TIG welding and an EHEA interlayer and (b) multipass-TIG welding and an Inconel 82 filler rod.
Figure 12. Macrostructrue of the dissimilar joints of P91/304L steel welded employing (a) A-TIG welding and an EHEA interlayer and (b) multipass-TIG welding and an Inconel 82 filler rod.
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Figure 13. Macrostructrue of the dissimilar joints of P91/304L steel welded employing A-TIG welding and an EHEA interlayer in a single pass.
Figure 13. Macrostructrue of the dissimilar joints of P91/304L steel welded employing A-TIG welding and an EHEA interlayer in a single pass.
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Figure 14. Weld defect observed at higher levels of the welding current and lower levels of weld traverse speed in A-TIG welding of P91/304L steel using an EHEA interlayer.
Figure 14. Weld defect observed at higher levels of the welding current and lower levels of weld traverse speed in A-TIG welding of P91/304L steel using an EHEA interlayer.
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Figure 15. Radiograhic films of the dissimilar joints of P91/304L steel welded employing (a,b) A-TIG welding and an EHEA interlayer and (c,d) multipass-TIG welding and an Inconel 82 filler rod.
Figure 15. Radiograhic films of the dissimilar joints of P91/304L steel welded employing (a,b) A-TIG welding and an EHEA interlayer and (c,d) multipass-TIG welding and an Inconel 82 filler rod.
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Figure 16. Distortion measurement of the A-TIG joint along (a) line 1, (b) line 2 and (c) line 3; distortion measurement of the multipass-TIG joint along (d) line 1, (e) line 2 and (f) line 3.
Figure 16. Distortion measurement of the A-TIG joint along (a) line 1, (b) line 2 and (c) line 3; distortion measurement of the multipass-TIG joint along (d) line 1, (e) line 2 and (f) line 3.
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Figure 17. Pictures of the dissimilar joints of P91/304L steel welded employing (a) A-TIG welding and an EHEA interlayer showing a lower distortion, and (b) multipass-TIG welding and an Inconel 82 filler rod showing a higher distortion.
Figure 17. Pictures of the dissimilar joints of P91/304L steel welded employing (a) A-TIG welding and an EHEA interlayer showing a lower distortion, and (b) multipass-TIG welding and an Inconel 82 filler rod showing a higher distortion.
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Jmmp 08 00283 g018
Figure 18. Economic assessment of dissimilar joints of P91/304L steel fabricated employing (a) the A-TIG welding process and an EHEA interlayer; (b) multipass-TIG welding and an Inconel 82 filler rod.
Figure 18. Economic assessment of dissimilar joints of P91/304L steel fabricated employing (a) the A-TIG welding process and an EHEA interlayer; (b) multipass-TIG welding and an Inconel 82 filler rod.
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Jmmp 08 00283 g019
Figure 19. Mechanism of (a,b) deeper penetration in A-TIG welding and (c,d) shallower penetration in TIG welding without flux.
Figure 19. Mechanism of (a,b) deeper penetration in A-TIG welding and (c,d) shallower penetration in TIG welding without flux.
Jmmp 08 00283 g019
Table 1. Chemical composition (wt.%) of the base metal plates of the P91 and 304L steel, Inconel 82 filler rod and AlCoCrFeNi2.1 EHEA interlayer.
Table 1. Chemical composition (wt.%) of the base metal plates of the P91 and 304L steel, Inconel 82 filler rod and AlCoCrFeNi2.1 EHEA interlayer.
MaterialCSiMnCrNiVMoTiAlNbCoCuBFe
P91 steel0.0520.410.468.20.250.191.00.010.010.0480.0140.060.00189.28
304L steel0.0150.451.5618.058.160.090.320.010.0050.010.170.410.00170.72
IN-82 filler rod0.050.1482.1518.270.70.010.030.20.092.10.150.0160.35.86
EHEA
Interlayer		------16.7338.81------7.25--18.60----18.61
Table 2. Mechanical properties of P91 and 304L steel plates.
Table 2. Mechanical properties of P91 and 304L steel plates.
BM PlateTensile Strength
(MPa)		Yield Strength
(MPa)		Elongation
(%)		Impact Toughness (J)
P91 steel71060024110
304L steel68037269155
Table 3. Process parameters used for the fabrication of joints.
Table 3. Process parameters used for the fabrication of joints.
Sr. No.ParametersA-TIGMultipass-TIG
1.Welding passes02
(01 Front and 01 back side)		07
(01 root pass + 06 filling pass)
2.Welding current210 ARoot pass: 160 A
Filling pass: 120 A
3.Welding voltage13 V11.5–13 V
4.Welding time70 mm/minRoot pass: 70 mm/min
Filling pass: 90 mm/min
5.Preheating temperature200–250 °C200–250 °C
6.Interpass temperature---200–250 °C
7.Heat input per pass1.404 kJ/mmRoot pass: 0.946 kJ/mm
Filling pass: 0.624 kJ/mm
8.Overall heat input2.808 kJ/mm4.69 kJ/mm
9.Shielding gas flow rate10 L/min10 L/min
10.Tungsten electrode diameter1.6 mm1.6 mm
11.Tungsten electrode angle60°60°
Table 4. Criteria for the acceptance levels of the joints for surface defects.
Table 4. Criteria for the acceptance levels of the joints for surface defects.
Sr. No.Type of Internal
Defects as per
ISO 6520-1 [53]		Acceptance Level 1Acceptance Level 2Acceptance Level 3Multipass-TIG JointsA-TIG Joints
1.Crater cracksNot allowedNot allowedNot allowedNo crater cracksNo crater cracks
2.Undercut, continuous and
Intermittent, t > 3 mm		Smooth transition is
required
h ≤ 0.05 t, max. 0.5 mm		Smooth transition is
required
h ≤ 0.1 t, max. 0.5 mm		Smooth transition is
required
h ≤ 0.2 t, max. 1 mm		No undercutsNo undercuts
3.Shrinkage groove (root
undercut)		Smooth transition is
required
l ≤ 25 mm,
h ≤ 0.05 t, max. 0.5 mm		Smooth transition is
required
l ≤ 25 mm,
h ≤ 0.1 t, max. 1 mm		Smooth transition is
required
l ≤ 25 mm,
h ≤ 0.2 t, max. 2 mm		No root undercutsNo root undercuts
4.Excess penetration
0.5 mm ≤ t ≤ 3 mm		h ≤ 1 mm + 0.1 bh ≤ 1 mm + 0.3 bh ≤ 1 mm + 0.6 bExcess penetration
h ≤ 1 mm + 0.1 b
h = 1.22 mm
1.22 ≤ 1.97		No excess penetration
5.SpatterAcceptance depends on application, e.g., material, corrosion protection.No spatterNo spatter
6.Root concavity
0.5 mm ≤ s ≤ 3 mm		Not allowedl ≤ 25 mm, h ≤ 0.1 th ≤ 0.2 mm + 0.1 tNo root concavityNo root concavity
7.Incompletely filled groove
0.5 mm ≤ s ≤ 3 mm		Not allowedl ≤ 25 mm, h ≤ 0.1 t,
max. 1 mm		l ≤ 25 mm, h ≤ 0.25 tNo lack of penetrationNo lack of penetration
8.Linear misalignment
0.5 mm ≤ s ≤ 3 mm		h ≤ 0.2 mm + 0.1 th ≤ 0.2 mm + 0.15 th ≤ 0.2 mm + 0.25 tNo linear misalignmentNo linear misalignment
Table 5. Criteria for the acceptance levels of the joints for internal defects.
Table 5. Criteria for the acceptance levels of the joints for internal defects.
Sr. No.Type of Internal
Defects as per
ISO 6520-1 [53]		Acceptance Level 1Acceptance Level 2Acceptance Level 3Multipass-TIG JointsA-TIG Joints
1.CracksNot allowedNot allowedNot allowedNo cracksNo cracks
2.PorosityA ≤ 1%
d ≤ 0.2 s, max. 3 mm
L = 100 mm		A ≤ 1.5%
d ≤ 0.3 s, max. 4 mm
L = 100 mm		A ≤ 2.5%
d ≤ 0.4 s, max. 5 mm
L = 100 mm		A ≤ 1%
d ≤ 0.2 s, max. 3 mm
L = 100 mm		A ≤ 1%
d ≤ 0.2 s, max. 3 mm
L = 100 mm
3.Clustered (localized)
porosity		dA ≤ wp/2, max. 15 mm
d ≤ 0.2 s, max. 3 mm		dA ≤ wp, max. 20 mm
d ≤ 0.3 s, max. 4 mm		dA ≤ wp, max. 25 mm
d ≤ 0.4 s, max. 5 mm		No clustered porosityNo clustered porosity
4.Linear Porosityl ≤ s, max. 25 mm
d ≤ 0.2 s, max. 2 mm
L = 100 mm		l ≤ s, max. 50 mm
d ≤ 0.3 s, max. 3 mm
L = 100 mm		l ≤ s, max. 75 mm
d ≤ 0.4 s, max. 4 mm
L = 100 mm		No linear porosityNo linear porosity
5.Lack of fusionNot allowedNot allowedNot breaking the surface
l ≤ 0.4 s, max. 4 mm		No lack of fusionNo lack of fusion
6.Elongated cavities
and wormholes		h < 0.2 s, max. 2 mm
Σl ≤ s, max. 25 mm
L = 100 mm		h < 0.3 s, max. 3 mm
Σl ≤ s, max. 50 mm
L = 100 mm		h < 0.4 s, max. 4 mm
Σl ≤ s, max. 75 mm
L = 100 mm		No elongated cavitiesNo elongated cavities
7.Lack of penetrationΣl ≤ 25 mm, L = 100 mmNot allowedNot allowedNo lack of penetrationNo lack of penetration
Table 6. Measurement of the angular distortion joints.
Table 6. Measurement of the angular distortion joints.
Sr. No.JointAngular Distortion
Line 1Line 2Line 3Mean
1.Multipass-TIG joint1.6°1.15°0.72°1.15°
2.A-TIG joint0.86°0.6°0.07°0.51°
Table 7. Economic assessment of joints.
Table 7. Economic assessment of joints.
Cost in RublesA-TIG WeldingMultipass-TIG Welding
Welder500/-2500/-
Shielding gas66.08/-205.33/-
Preheating flame gas125/-290/-
Filler wire--1200/-
EHEA interlayer100/----
Flux15/----
Welding power1.12/-5.78/-
Groove machining --450/-
Total cost807.2/-4651/-
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MDPI and ACS Style

Sonar, T.; Ivanov, M.; Shcherbakov, I.; Trofimov, E.; Khasanova, E.; Cheepu, M.; Liu, K. Enhancing Welding Productivity and Mitigation of Distortion in Dissimilar Welding of Ferritic-Martensitic Steel and Austenitic Stainless Steel Using Robotic A-TIG Welding Process. J. Manuf. Mater. Process. 2024, 8, 283. https://doi.org/10.3390/jmmp8060283

AMA Style

Sonar T, Ivanov M, Shcherbakov I, Trofimov E, Khasanova E, Cheepu M, Liu K. Enhancing Welding Productivity and Mitigation of Distortion in Dissimilar Welding of Ferritic-Martensitic Steel and Austenitic Stainless Steel Using Robotic A-TIG Welding Process. Journal of Manufacturing and Materials Processing. 2024; 8(6):283. https://doi.org/10.3390/jmmp8060283

Chicago/Turabian Style

Sonar, Tushar, Mikhail Ivanov, Igor Shcherbakov, Evgeny Trofimov, Emiliya Khasanova, Muralimohan Cheepu, and Kun Liu. 2024. "Enhancing Welding Productivity and Mitigation of Distortion in Dissimilar Welding of Ferritic-Martensitic Steel and Austenitic Stainless Steel Using Robotic A-TIG Welding Process" Journal of Manufacturing and Materials Processing 8, no. 6: 283. https://doi.org/10.3390/jmmp8060283

APA Style

Sonar, T., Ivanov, M., Shcherbakov, I., Trofimov, E., Khasanova, E., Cheepu, M., & Liu, K. (2024). Enhancing Welding Productivity and Mitigation of Distortion in Dissimilar Welding of Ferritic-Martensitic Steel and Austenitic Stainless Steel Using Robotic A-TIG Welding Process. Journal of Manufacturing and Materials Processing, 8(6), 283. https://doi.org/10.3390/jmmp8060283

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