Stainless Steel Dissimilar Joints Research Articles

Characterization and optimization of TIG welding parameters for AISI 304 and AISI 316 stainless steel dissimilar joints

This study explores the impact of tungsten inert gas (TIG) welding parameters on the mechanical properties and microstructure of dissimilar welds between AISI 304 and AISI 316 austenitic stainless steels. Given the growing industrial demand for these materials, the research focuses on optimizing welding current, shielding gas flow rate, and voltage to enhance tensile strength, hardness, and impact toughness. Using the L9 orthogonal array based on Taguchi’s methodology, the experiments revealed that Relatively highs currents and voltages significantly improved the ultimate tensile strength (up to 673.67 MPa) and impact energy absorption (up to 36.5 J). Microstructural analysis indicated refined grain structures in the heat-affected zones, with pronounced grain growth in AISI 316 due to its thermal sensitivity. The micro-hardness analysis revealed that the highest hardness occurred in the HAZ of AISI 304, with samples 5 and 6 exhibiting the optimal hardness profile, reflecting the most favorable welding parameters. The study concludes that a current range of 80-90 A and a voltage range of 10-11 V and a shielding gas flow rate of 12-16 L/min provide optimal welding conditions, offering robust guidelines for industrial applications requiring high-performance dissimilar welds.

Investigating the microstructure and mechanical properties in furnace brazing Ti–6Al–4V to 17-4 PH stainless steel dissimilar joint with BNi-2 filler metal

Due to the distinct physical and metallurgical characteristics of titanium and steel, the welding of these two materials poses challenges and holds significant importance. This study investigates the impact of brazing time and temperature on the microstructure and mechanical properties of dissimilar brazing between 17-4 PH stainless steel and Ti–6Al–4V using BNi-2 as a filler metal, focusing on the formation of brittle compounds like FeTi and Fe2Ti during the brazing process. The joint between these materials is commonly utilized in various industrial applications. The assessment involved the use of optical microscope, scanning electron microscope, shear – tensile test, microhardness test, and wettability measurement. Brazing of the base metals was conducted at temperatures of 1050/1100 °C for durations of 15 and 30 min to determine the optimal temperature and time combination. The results indicated that the best joint properties were achieved at 110 °C for 15 min, with an average shear strength of 38.46 MPa. Contact angle measurements revealed that BNi-2 exhibited superior wettability on 17-4 PH compared to Ti–6Al–4V. Furthermore, increasing the temperature from 1050 to 1100 °C led to a reduction in contact angle from 9.98 to 8.83° for 17-4 PH, and from 16.51 to 10.12° for Ti–6Al–4V indicating an improvement in wettability.

Joining mechanism evolution of fusion welded TC4 titanium alloy/304 stainless steel dissimilar joint by GTAW

Gas tungsten arc welding with a pure Cu filler wire was carried out to join the TC4 titanium alloy and 304 stainless steel. Filling pure Cu filler wire assisted with regulating welding current could effectively restrain the concentrated generation of Ti–Fe brittle intermetallic compounds. Three joining modes exist in the fusion welding titanium alloy and stainless steel. In the partial fusion welding mode, the TiCu phase decreased and the fine granular τ2 phase formed in the Ti/Cu interfacial zone, simultaneously, the molten zone consisted of a Cu solid solution and α-(Fe, Cr) phase formed at the Cu/Fe interface, resulting in mechanical interlocking effect and consequent high tensile strength of 363 MPa. Increasing the welding current would lead to the alloying of Ti x Cu y phases, and then enhance the Ti/Cu interface.

Interface and microstructural characteristics of titanium and 304 stainless steel dissimilar joints by upset butt welding using a gleeble thermo mechanical simulator

This work discusses joining dissimilar material combinations of commercial pure titanium and 304 stainless steel utilizing an upset butt welding process. The process involves rapid heating to a temperature of 1150 °C at a heating rate of 200 °C/s with simultaneous application of pressure at a level of 1.5 MPa to achieve fusion. Then, the joints are post-heated to 850 °C during the soaking period for 90 min to relieve the welding residual stresses and achieve good bond strength. The upset welding experiments are conducted with the help of a Gleeble thermomechanical simulator. This process does not require the conventional severe metallographic preparation generally used for the typical diffusion bonding process. The weld joint achieves an ultimate tensile strength of 274 MPa, approximately 60% of the strength of commercial pure titanium. Moreover, intermetallic compounds occurred at the interfaces, which were attributed to significant changes in the microhardness of the Ti/SS alloy.

Influence of Fusion Zone Metallurgy on the Mechanical Behavior of Ni-Based Superalloy and Austenitic Stainless Steel Dissimilar Joint

Influence of Fusion Zone Metallurgy on the Mechanical Behavior of Ni-Based Superalloy and Austenitic Stainless Steel Dissimilar Joint

Rotary friction welding of Inconel 718 – AISI 304 stainless steel dissimilar joint

Nickel-based superalloy Inconel 718 and austenitic stainless steel AISI 304 are joined by rotary friction welding. The changes in microstructure and mechanical properties of the dissimilar joint for solutionising, solutionising + aging, and post-weld aging treatment, with a prior solution heat treatment, are studied. Two distinct microstructural zones, the FDZ (fully deformed zone) and the TMAZ (thermo-mechanically affected zone) are observed in all weldments. The post-weld aged joint sample shows the highest tensile strength and hardness due to the precipitation of γ′ (Ni3(Ti, Al)) and γ″ (Ni3Nb) strengthening precipitates. The solution-treated sample shows the highest yield strength, while the solutionising + aging treatment is found to deteriorate the mechanical properties of the dissimilar joint. The observed changes in the mechanical properties are investigated based on microstructure and electron dispersive spectroscopy.

Enhancement on the low-pressure shot peened process of monotonic plastic deformation behaviors of Ni–4Cu–3Mo alloy/super austenite stainless steel dissimilar joints using laser beam welding

This research paper mainly discusses the low-pressure shot-peened (LPSP) process of 2 mm thick sheet plates of monotonic mechanical behaviors of Ni–4Cu–3Mo alloy/super austenite stainless steel (SASS) dissimilar materials joint by laser beam welding. Three types of butt joint (Sample-1, Sample-2, and Sample-3) configuration methods of the laser beam welding process were implemented at the Ni–4Cu–3Mo alloy/SASS dissimilar weldments and LPSP weldments. The microstructure image of the fusion zone revealed that the high heat inputs were distributed at the grain boundary and the prior coarse grain structures were converted into NiCr and C–Cr with significant improvement in the α'-martensite structure. To achieve continuous improvement in yield strength of LPSP weldments compared to the dissimilar weldments, the plastic deformations rate was decreased in the shot-peened weldments. The base metals of tensile samples length were prepared as ±5 mm; however, samples clearly indicated that the dissimilar weldments and LPSP weldments showed the failure in the fusion zone. The average elongation of dissimilar LPSP weldments was increased by 13%; however, the heat inputs collapsed the grain boundaries growth and the structure was converted into twin boundaries and α-martensite structures. The hardness measurement at the fusion zone of dissimilar and LPSP weldments was performed and the average hardness value of 290 HV at the fusion zone and 211 HV at the heat-affected zone was observed for LPSP weldments. The fracture morphology revealed that neither major cracks nor minor voids at the fusion zone of the tensile sample were formed.

The effects of filler metal and butter layer on the microstructure and mechanical properties of API 5L X65/AISI 304L joint

The effects of different filler metals on the microstructure and mechanical properties of buttered API X65/AISI 304L stainless steel dissimilar joint have been investigated. The use of a butter layer and a suitable filler metal have major implications for the properties of dissimilar joints. In this study, API X65 high-strength low-alloy (HSLA) steel was first buttered with an austenitic Ni-based ERNiCr3 layer, followed by a post-weld heat treatment (PWHT) at 650 °C. ER308L (W308), ER309L (W309), and ERNiCr3 (WNiCr3) filler metals were then used to join the buttered API X65 side to AISI 304L stainless steel. All joints were first evaluated by radiographic testing to make sure that a flawless weldment has been attained. A scanning electron microscope (SEM), an optical microscope (OM), and energy-dispersive X-ray spectroscopy (EDS) were used to study microstructures of joints. Standard-sized and sub-sized tensile and impact tests were carried out. Microhardness profilometry was also conducted across the joint. Results showed that the finest grain structure was attained in the heat affected zone (HAZ) at the AISI 304L side and the lowest δ ferrite content was achieved in samples with the filler metal ERNiCr3 (WNiCr3). It appears that the heat input, generated by WNiCr3 filler metal, is comparatively lower than those generated in W308 and W309 samples. WNiCr3 weldment showed the highest hardness due to the formation of fine carbide particles such as NbC and TiC. Results of sub-sized impact tests showed that the highest impact energy was attained in the HAZ of the WNiCr3 sample.

Unravelling the microstructure – indentation creep resistance relationships for friction stir welded modified 9Cr-1Mo steel and LN-type 316 stainless-steel dissimilar joints

In this article, the indentation creep characteristics and the microstructures are assessed for the friction stir welded modified 9Cr-1Mo steel and LN-type 316 SS dissimilar joint. Microstructures are characterized for the post-weld heat treated and indentation crept samples at different conditions with optical microscopy, scanning electron microscope and energy dispersive X-ray spectroscopy. Distinct heat-affected zones were revealed with the refined and reformed martensite (α′) and austenite (γ) structures that formed in view of the distinct thermal conductivity property and the differences in lower critical(Ac1) and upper critical(Ac3) transformation temperatures. The size of prior austenite grain sizes was found to be varied significantly at the different regions. Indentation creep data were acquired in distinct weld zones at 873, 898 and 923 K. Zone-wise indentation depth, steady-state creep behaviour (SSCR) and activation energy ( Q) were evaluated and correlated with the microstructures. The formation of small prior austenitic grain (PAG) structures and the grain boundary vacancies has led to maximum creep deformation (86.83%) at the heat affected zone of the modified 9Cr-1Mo steel. Furthermore, the reduction in lath structures and the formation of tiny α′ with soft substructures have lowered the hardness values to around 210 ± 21 HV, which is 20 HV less than the post weld heat treated sample. In the stir zone, the presence of dynamically refined and rich γ along with fine α′ layers has improved the steady-state creep rate of 9.112 E-7, which is less than the modified 9Cr-1Mo steel and the heat affected zone at modified 9Cr-1Mo side. The coarse austenite structures that existed in the LN-type 316 base metal have resisted more creep damage and exhibited high activation energy (i.e. 490 kJ mol−1) than the stir zone and heat affected zone of the LN-type 316 SS.

Electron Beam Brazing of Titanium and Stainless Steel Dissimilar Joints with Ag-Based Filler

In this work, electron beam was used for butt brazing of austenitic stainless steel with grade 2 titanium. Due to its low solidus temperature and high silver content, AWS BAg-21 filler containing Ag, Cu, Sn and Ni was selected. The joints were brazed with a defocused oscillating beam using offset. The resulting brazed joints were subjected to static tensile testing, light microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) analysis and hardness tests. By using appropriate parameters it was possible to reduce the phenomenon of diffusion of titanium atoms into the joint, which improved the properties of the obtained joints. The maximum tensile strength obtained was 244.2 MPa.

Improvement in the microstructural properties of super duplex and austenitic stainless steel dissimilar joints by incorporating Ni-based austenitic interlayer

Tungsten inert gas welding (TIG) has remained a worldwide utilized welding technology in the industry to till date. Activated tungsten inert gas welding (ATIG) is also an advanced variant of TIG to enhance the penetration depth and reduce the width of the weld bead in single-pass compared to traditional TIG welding. The current study focuses on utilizing the Inconel interlayer approach to link dissimilar cold-rolled super duplex and austenitic stainless steels, which are mostly used in the offshore and marine industries. A systematic strategy is used to emphasize the studies conducted after using the ATIG interlayer procedure over the traditional TIG interlayer welding process. The research also studies and compares the microstructure, elemental mapping of the weld interface, phase identification and mechanical properties of dissimilar welded super duplex and austenitic steel samples. • ATIG welding approach for achieving single pass penetration of 6 mm thick plate with reduced weld heat input. • Without any weld defects such as weld porosity, undercut, overlap defect, and hot cracking a dissimilar welding of austenitic 202 and super duplex 32760 plates were successfully completed. • Microstructure evolution such as reduction in the width of heat affected zone, and reduction in the width of the unmixed zone was seen after using the ATIG interlayer weld technique. • Mechanisms such as reverse Marangoni and arc constriction in ATIG welding techniques could easily reduce parent metal loss in weld zones.

Interface microstructure and mechanical properties of copper/304 stainless steel dissimilar joint assisted by Ni transition layer using ultrasonic additive manufacturing (UAM)

The copper/304 stainless steel joints with high strength are obtained by preparing nickel transition layer on the steel surface using ultrasonic additive manufacturing (UAM) and pulsed TIG welding method. The results show that the addition of the nickel intermediate layer achieves metallurgical isolation between copper and steel, inhibits the infiltration of copper into steel grain boundaries and reduces joint stress, resulting in the formation of hybrid joints including fusion brazing (copper-nickel) and diffusion welding (nickel-steel). The weld and the vicinity of the interface are mainly composed of Cu-Ni solid solution and Ni-rich phase. The wavy texture produced by UAM on the nickel surface can form mechanical interlock at the interface to improve the joint strength, and finally all joints fracture near the fusion line on the copper side.

Microstructure and Corrosion Properties of Austenitic and Duplex Stainless Steel Dissimilar Joints

In several applications duplex stainless steels should be joint welded to conventional austenitic stainless steels. In this research LDX 2101 lean duplex stainless steel sheets were welded to conventional 304 austenitic stainless steels, using gas tungsten arc welding. For the welded joints three different welding rods were used: ER 308L, ER 309LSi, and ER 2209. For gas shielding two different shielding gases were used: argon and argon +2% nitrogen. It was found that the nitrogen addition to the shielding gas promoted austenite formation in the weld metal. It was also found Schaeffler-diagram modified by Outokumpu showed a very good estimation to the ferrite content and chemical composition of the weld metal. The ferrite content estimated by the Outokumpu-diagram, showed a close correlation to measured ferrite contents, the highest error was 30%. In case of the chemical composition of the weld metal, the Cr- and Ni-contents were estimated with a maximum of 15% error. In terms of the corrosion resistance, the best pitting corrosion resistance was achieved using the 308L welding rod with argon shielding gas, where the weight loss was 1.6% after the 24 hours immersion test.

Study on the Weldability of Copper-304L Stainless Steel Dissimilar Joint Performed by Robotic Gas Tungsten Arc Welding.

The welding process of dissimilar metals, with distinct chemical, physical, thermal, and structural properties, needs to be studied and treated with special attention. The main objectives of this research were to investigate the weldability of the dissimilar joint made between the 99.95% Cu pipe and the 304L stainless steel plate by robotic Gas Tungsten Arc Welding (GTAW), without filler metal and without preheating of materials, and to find the optimum welding regime. Based on repeated adjustments of the main process parameters—welding speed, oscillation frequency, pulse frequency, main welding current, pulse current, and decrease time of welding current at the process end—it was determined the optimum process and, further, it was possible to carry out joints free of cracks and porosity, with full penetration, proper compactness, and sealing properties, that ensure safety in operating conditions. The microstructure analysis revealed the fusion zone as a multi-element alloy with preponderant participation of Cu that has resulted from mixing the non-ferrous elements and iron. Globular Cu- or Fe-rich compounds were developed during welding, being detected by Scanning Electron Microscope (SEM). Moreover, the Energy Dispersive X-ray Analysis (EDAX) recorded the existence of a narrow double mixing zone formed at the interface between the fusion zone and the 304L stainless steel that contains about 66 wt.% Fe, 18 wt.% Cr, 8 wt.% Cu, and 4 wt.% Ni. Due to the formation of Fe-, Cr-, and Ni-rich compounds, a hardness increase up to 127 HV0.2 was noticed in the fusion zone, in comparison with the copper material, where the average measured microhardness was 82 HV0.2. The optimization of the robotic welding regime was carried out sequentially, by adjusting the parameters values, and, further, by analyzing the effects of welding on the geometry and on the appearance of the weld bead. Finally, employing the optimum welding regime—14 cm/min welding speed, 125 A main current, 100 A pulse current, 2.84 Hz oscillation frequency, and 5 Hz pulse frequency—appropriate dissimilar joints, without imperfections, were achieved.

Investigation of weld defects, microstructural, and mechanical features of TWIP and austenitic stainless steel dissimilar joints by pulsed GTAW process

Investigation of weld defects, microstructural, and mechanical features of TWIP and austenitic stainless steel dissimilar joints by pulsed GTAW process

Metallurgical and Mechanical Characterization of Low Carbon Steel—Stainless Steel Dissimilar Joints Made by Laser Autogenous Welding

This paper addresses the metallurgical and mechanical characterization of dissimilar joints made by laser autogenous welding between thin sheets of low-carbon steel (CS) and austenitic stainless steel (SS). The welding technology applied, previously optimized to produce sound dissimilar joints, is based on the heat source displacement from the weld gap centerline towards CS, in order to reduce the SS overheating. The research includes optical microscopy observations, energy dispersive X-ray analysis (EDX) to assess the wt% of Cr, Ni, and Fe in all regions of the dissimilar welded joint, hardness measurements, and tensile tests of transverse-welded flat specimens. In comparison with classical determination of the joint overall mechanical characteristics, the novelty of this research consists of experimental assessment of the local mechanical behavior of the fusion and heat affected zones by using a digital image correlation technique (VIC-2D). This is an efficient tool for determining the constitutive properties of the joint, useful for modelling the mechanical behavior of materials and for verifying the engineering predictions. The results show that the positive difference in yielding between the weld metal and the base materials protects the joint from being plastically deformed. As a consequence, the tensile loading of flat transverse specimens generates the strain localization and failure in CS, far away from the weld.

Interfacial reaction and mechanical properties of diffusion bonded titanium/17-4 PH stainless steel dissimilar joint using a silver interlayer

Diffusion bonding of titanium (Ti) to 17-4 PH high strength stainless steel is challenging owing to the formation of brittle Ti-Fe intermetallic compounds (IMCs) at joint interface. In the current study, it was demonstrated that such detrimental Ti-Fe IMCs can be effectively eradicated by using a silver (Ag) interlayer. The diffusion bonded Ti/Ag/17-4 PH stainless steel is characterized by Ti-Ag solid solution, TiAg, remnant Ag interlayer and Ag-(Fe, Cr, Ni) interdiffusion layer. The interfacial reaction phase TiAg exhibited no detrimental effect on bonding strength. During tensile test, ductile fracture took place in the remaining Ag interlayer of resultant joint. Bonding strength up to ∼420 MPa was obtained over bonding durations in the range of 15 ∼ 25 min. It is thus concluded that using an Ag interlayer is highly appealing in improving bonding strength of diffusion bonded Ti/17-4 PH stainless steel dissimilar joint.

Investigation on regulating inter-granular penetration in CoCrMnFeNi high-entropy alloy and 304 stainless steel dissimilar joints

The inter-granular penetration inside CoCrMnFeNi high-entropy alloy (HEA) in the dissimilar brazing joint of 304 stainless steel and this HEA were regulated for the first time by using Ag72Cu as filler metal (FM) and by annealing HEA. The as-rolled HEAs were annealed at a series of temperatures for 1 h before brazing. The microstructural evolution of the dissimilar joints found that penetration was reduced with increasing annealing temperature because of the consistent decreases in grain boundary density, which reduces the channels for penetration, and the gradually stable grain boundaries in HEA, which decreases the driving force of inter-granular penetration. The direct inter-diffusion between the HEA grain and FM was limited. HEA atoms in FM originated from the dissolved HEA during brazing, manifesting the acceleration of penetration on the inter-diffusion between HEA and FM. Regulating inter-granular penetration in the dissimilar joint decreased the stress concentration at the HEA side and ensured the solution-strengthening effect of Mn in FM and the contact area between FM and HEA. The tensile strength of the dissimilar joint with regulated inter-granular penetration could reach 514.98 MPa and is considerably higher than that of the joint with few penetration, which hints that penetration does not always impair the mechanical performance of joints.

Maintenance of the Austenite/Ferrite Ratio Balance in GTAW DSS Joints Through Process Parameters Optimization.

The present work describes the influence of the parameters employed in the gas tungsten arc welding process (GTAW) when nickel powder is used as a filler metal in 2304/2507 duplex stainless-steel dissimilar joints. Multi-objective optimization was applied in order to maintain the austenite/ferrite percentage in the welded zone. A microstructural and phase quantification analysis was performed in each sample through optical and scanning electron microscopes. It was found that a nickel powder addition combined with low heat input increased the biphasic ratio across the different zones of the dissimilar welded samples. Although the austenite volume fraction increased in the 2304 heat-affected zone (HAZ) near to 25%, it was not sufficient according to international standards. The obtained results led to the maintenance of the 50/50 phase percentage in the 2507 HAZ welded joint side, as well as to the increment of the austenite percentage in the 2304 HAZ.

Microstructure and performance of hybrid laser-arc welded high-strength low alloy steel and austenitic stainless steel dissimilar joint

Effects of hybrid laser-arc welding process parameters on the weld formation of a dissimilar steel joint were studied. A full penetrated weld with minimum defects was obtained under the optimized parameters. Different thermal conductivities and phase transition temperature resulted in a wider heat affected zone (HAZ) of high-strength low alloy steel (EH36) than that of austenitic stainless steel (316L). Owing to the limited penetration of arc, the laser zone could be only heated by laser while the hybrid zone was heated by not only laser but also arc, resulting in higher heat input and larger grain size in hybrid zone than in laser zone. The addition of filler wire led to higher contents of chromium (Cr) and nickel (Ni) in hybrid zone than laser zone, which inhibited the formation of austenite and led to the formation of martensite in laser zone. Small grain size and existence of martensite resulted in higher hardness of laser zone than hybrid zone. Tensile samples of both laser zone and hybrid zone failed at the EH36 side with massive dimples distributing on the fracture surfaces, indicating good tensile property of the welds and typical characteristics of ductile fracture. Corrosion resistance of laser zone was weaker than that of hybrid zone, which was closely related to the formation of martensite with poor corrosion resistance instead of austenite with good corrosion resistance.