Stainless Steel Weld Research Articles

Electrochemical Analysis on Intergranular Corrosion of Austenitic Stainless Steel Weld in Molten Nitrate Salt

An investigation of intergranular corrosion (IGC) sensitization in molten nitrate salts of austenitic stainless steel welds of AISI 304, AISI 304H, and AISI321 produced by GTAW with ER 308L and ER 347 fillers was performed. The degree of sensitization (DOS) to IGC was assessed using a double loop electrochemical potentiokinetic reactivation and pitting potential. It was found that DOS levels in weld zones were quite low, not exceeding 15%, while those in HAZs were up to 60% after exposure at 600 °C for 300 h. The low DOS levels were due to low carbide precipitation. However, another cause of DOS was the delta-ferrite to sigma transformation in weld zones. Linear sweep voltammetry was used to quantify the sigma phase.

Effects of laser power on the microstructure, mechanical properties, and corrosion resistance of welded joints in dissimilar laser welding of 05Cr17Ni4Cu4Nb stainless steel and HR-2 stainless steel

Effects of laser power on the microstructure, mechanical properties, and corrosion resistance of welded joints in dissimilar laser welding of 05Cr17Ni4Cu4Nb stainless steel and HR-2 stainless steel

Stress Corrosion Cracking of Stainless Steel Weldments in Nuclear Power Plants

Stress Corrosion Cracking of Stainless Steel Weldments in Nuclear Power Plants

Experimental Investigation of Temperature Field, Fusion Zone Microstructure and Mechanical Properties During Dissimilar Laser Welding of Nickel-Base Alloy and Duplex Stainless Steel

Experimental Investigation of Temperature Field, Fusion Zone Microstructure and Mechanical Properties During Dissimilar Laser Welding of Nickel-Base Alloy and Duplex Stainless Steel

Optimization of the Thermokinetic Method for the Control of Weld Decay in AISI 304L and AISI 316L Stainless Steel Weldment

This study investigates the control of weld decay in AISI 304L/316L alloy weldments for liquefied natural gas (LNG) and cryogenic environments using the Tungsten Inert Gas (TIG) welding technique. Weldment samples were thermokinetically treated at 1050, 1100, and 1150°C and cooled in five mediums: Water, Salt, Natural Air, Salt with annealing, and Water with annealing, to retain carbon and chromium in solid solution at approximately 30°C. Furthermore, evaluation methods based on metallography i.e. optical microscopy (OM), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDX), Wear Test (i.e. wear rate and wear track) and electrochemical corrosion potential measurements were adopted. An experimental design table was developed using the design expert software 13.0. This helped develop a predictive mathematical model for ascertaining the optimum operating service conditions of the material. From the results, the optical microscopy analysis revealed that the control sample exhibited a more irregular pattern than others. Results showed that the control sample had a more irregular structure, while air-cooled samples exhibited smoother surfaces, indicating better bonding. SEM revealed a coarse surface with uneven particle distribution post-heat application. The predominant elements were Iron (Fe), Chromium (Cr), and Nickel (Ni). Corrosion potential varied between -0.5 to 0.15 V, demonstrating wave-like behaviour over time. Wear analysis indicated that lower coefficients of friction correlate with better wear resistance. Finally, response surface methodology (RSM) revealed that increasing temperature proportionally increased yield and corrosion rates. While the identified optimal values for Temperature are (1112.68°C), Material (316L), and Quenching Medium (SQ+SA), resulting in specific values such as Wear Rate (5.76896E-06), Coefficient of friction (0.224254), Corrosion Rate (0.395566), and Weight of Heat-Treated Sample (14.7797). The study enhances understanding of the mechanisms affecting welding and contributes to optimizing welding procedures for improved mechanical properties and corrosion resistance.

Effect of Precipitation Behavior and Deformation Twinning Evolution on the Mechanical Properties of 16Cr–25.5Ni–4.2Mo Superaustenitic Stainless Steel Weld Metals

Effect of Precipitation Behavior and Deformation Twinning Evolution on the Mechanical Properties of 16Cr–25.5Ni–4.2Mo Superaustenitic Stainless Steel Weld Metals

A novel dissimilar resistance spot welding of Ti6Al4V alloy and 316L stainless steel via copper as interlayer by using optimal electrodes

A novel dissimilar resistance spot welding of Ti6Al4V alloy and 316L stainless steel was performed via copper as interlayer by using optimal electrodes. A significant improvement in nugget morphology being of less defects was achieved with increasing the copper interlayer thickness from 50 μm to 400 μm. Thinner interfacial reaction layers at both the nugget/titanium interface and the nugget/stainless steel interface and finer equiaxed dendritic grained structure at the inner nugget were formed with copper interlayer thickness of 300 μm compared with those without interlayer. The formation of TiCu and Ti2Cu was facilitated with the incorporation of Cu into the nugget, which effectively inhibited the formation of the brittle Ti–Fe intermetallic compounds including Fe2Ti. The nugget in the welded joint with copper interlayer in 300 μm thickness exhibited a far lower microhardness than that of the interlayer-free welded joint, and the average microhardness reduced to 604 HV in the inner nugget, which was about 36% lower than that of the interlayer-free welded joint. The tensile shear load of the welded joint exhibited an increased tendency with increasing interlayer thicknesses from 50 μm to 300 μm, and the maximum tensile shear load of 6.3 kN was obtained with the interlayer thickness of 300 μm, which was ∼97% higher than that of the interlayer-free welded joint. The welded joint with copper interlayer exhibited hybrid ductile and fragile fractured characteristics. The work would provide a facile and cost-effective method to achieve a reliable welded joint of Ti alloy and stainless steel.

Flux-bound TIG welding on UNS S32760 super duplex stainless steel using activating fluxes

In this article, the effect of activating flux powders viz., Silicon Dioxide (SiO2), Chromic Oxide (Cr2O3), Titanium Dioxide (TiO2) and Vanadium Pentoxide (V2O5) on Flux-Bound TIG (FB-TIG) welding of UNS S32760 Super Duplex Stainless Steel (SDSS) is investigated. Also, conventional TIG welding is done for a comparative study with the FB-TIG welds. The macrographs of the welds are obtained to analyze the depth, width and aspect ratio. The depths obtained with all the fluxes are found to be superior relative to the conventional TIG welds. The highest penetration of 6 mm is obtained for V2O5 welds. Then the microstructure and composition of the welds are analyzed using Optical Microscopy and Area-Mapping analysis. The authors observed the presence of three forms of austenite viz., Grain Boundary Austenite, Intragranular Austenite and Widmanstatten Austenite in the weldment zones. The micro-hardness profiles of the welds are also analyzed, and the profiles obtained with all the FB-TIG welds are found to be relatively smoother without any abrupt variations. Through this investigation, it is delineated that FB-TIG welding can increase the overall productivity in the welding of SDSS, as the penetration obtained is up to thrice relative to the conventional TIG welding.

Indentation-Free Resistance Spot Welding of SUS301L Stainless Steel

Paint-free bodywork has become an attractive alternative for rail vehicles, in the direction of easy maintainability and low manufacturing costs. However, conventional resistance spot welding inevitably leaves indentation marks to detrimentally reduce the optical homogeneity of the paint-free bodywork. In light of this, indentation-free resistance spot welding is proposed for joining SUS301L stainless steel sheets in order to achieve superior surficial integrity. A tiny SUS301L steel ball with a diameter of 1.5 mm was chosen as the intermediate filler between two steel sheets to avoid the formation of surficial indentation. The influence of welding current and welding time on the mechanical properties of joints was studied. The optimal parameters of the mechanical properties were obtained when the welding current was 8.0 kA, the welding time was 150 ms, the electrode pressure was 0.35 MPa, and the electrodes were cylindrical planar electrodes, which was determined by comparing the tensile shear test results. The surficial indentation depth was less than 1% of the plate thickness, and no observable indentations were seen on the surface of the optimized welding spots.

Mechanisms of laser non-uniform shock peening on the mechanical properties of SUS 304 stainless steel weld joints

The technique of Laser Non-Uniform Shock Peening (LNUSP) is proposed based on the residual stress distribution in welded joints and the shock wave peak pressure of SUS 304 stainless steel. The study investigated the effects of LNUSP on the mechanical properties of laser beam oscillation welded (LWW) joints of SUS 304 stainless steel. The results indicate that LNUSP induced residual compressive stress with an affected layer depth exceeding 0.9 mm, leading to a more uniform residual stress distribution. LNUSP also induced martensitic phase transformation, altered the grain structure orientation, formed parallel dislocation arrays that refined the grains, increased dislocation density leading to dislocation tangles, and induced mechanical twins of 20–70 nm. Furthermore, LNUSP significantly enhanced microhardness and promoted a more uniform hardness distribution, favoring a better balance between strength and ductility. LNUSP notably increased the yield strength (YS) and ultimate tensile strength (UTS) by 49.4% and 5.1%, respectively, compared to the original samples. The LNUSP-treated samples demonstrated superior strength and plasticity, attributed to the uniformity of internal plastic deformation.

Phase quantification in a duplex stainless steel welds using NDT techniques

ABSTRACT Duplex stainless steels are composed of ferrite and austenite in equal volume fractions of these phases, which provides an excellent combination of mechanical properties and corrosion resistance, especially when compared with conventional stainless steel grades. When these steels are welded, there are significant changes in the austenite-to-ferrite ratio therefore in their final properties. Nowadays, the ferritoscope is the unique non-destructive technique used to quantify these two phases content in situ. This tester instrument is limited to the evaluation of large areas, is not suitable for the heat affected zone and is also very sensitive to the surface finish, being considered an intermediate precision technique. So, it is necessary to develop more reliable field techniques. In this research, thermoelectric power measurements and induced current techniques are proposed to evaluate the phase quantification in S32205 welds. According to the results, both techniques are reliable and highly sensitive to phase changes in the weld bead, heat affected zone and base metal. For the thermoelectric power technique, a probe with nickel tip should be used to obtain the highest sensitivity and for the induced current technique, a probe type-pencil with a central frequency of 6 MHz should be used.

The effect of oxide scale on the corrosion resistance of SUS301L stainless steel welding joints

The effect of thermal oxidates on the corrosion of SUS301L stainless steel welded joint was investigated using electrochemical corrosion test and TEM microstructure observation. Activation dissolution behavior without passive region was found in the potentiodynamic polarization curves on the welding zone and heat affected zone. The activation corrosion is related to the preferential dissolution of the NiFe layer at the interface between chromium oxide and substrate. However, the passive region in the polarization curve reappears after the unstable NiFe dissolves in the salt-frog test. The passivation behavior due to microstructure evolution beneath the thermal oxide film was discussed during the corrosion process.

Electrochemical behavior and microstructure of diffusion welding of zirconium alloy and super duplex stainless steel

In this study, the effect of welding temperature on interface microstructure, mechanical properties, and electrochemical behavior of diffusion welded joints (DWJs) of zirconium alloy (ZrA, Zr702 grade) and super duplex stainless steel (2205 duplex stainless steel grade) were investigated. Alloys were welded in a vacuum atmosphere at four different temperatures (800, 850, 900, and 925 °C) for 75min under 4MPa compressive pressure. The optical, scanning electron microscopy, electron probe micro-analyzer, and X-ray diffraction techniques were used to characterize the interfacial microstructure of the DWJs. Layers of intermetallics were formed along the welded interface at 850 °C and above welding temperatures. At 850 °C, a single reaction layer (phase mixture of ZrFe2+ZrCr2) was observed; however, bilayers (ZrFe2+ZrCr2 and Fe2Zr+FeZr3 phase mixtures), and triple layers (ZrFe2+ZrCr2, Fe2Zr+FeZr3, and β-Zr+FeZr3 phase mixtures) were observed at the welded interface of the joints processed at 900 and 925 °C, respectively. Width of the reaction layer (phase mixtures) increases with an increase in the welding temperature. The DWJs processed at 900 °C reach the maximum joint strength of ~312MPa along with ~6.4% ductility. For corrosion analysis, studies of the base alloys and DWJs in 0.1mol/L HCl and 0.1mol/L NaOH solutions separately using electrochemical techniques, such as open circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization were undertaken.

Effect of energy on the interface morphologies and tensile-shear properties of the electromagnetic pulse welding T2/SS304 joints

This investigation focused on the effect that electromagnetic pulse welding (EMPW) of copper (T2) and stainless steel (SS304) dissimilar materials with various discharge energies, which is interfacial morphology and tensile-shear properties of the joints. The results showed that the interface of T2/SS304 dissimilar material joints treated with EMPW exhibits a typical waveform morphology. The maximum wave peak distance reaches 36 μm (39 kJ), and the distance between peak and trough reaches 6 μm (37 kJ, 39 kJ). The tensile-shear properties of the joints were better than those of the base material, with the fracture mode changing from interfacial fracture (35 kJ) to base mental fracture (37 kJ, 39 kJ), and the maximum tensile-shear of the joints was 11.1 kN (39 kJ). The wave spacing after fracture was extended up to 3 μm.

Influence of arc energy on the microstructure and corrosion behavior of ER2209 duplex stainless steel deposited on Q345B low-alloy steel by GMAW

In order to eliminate the complex effects of thermal cycling and the thermal effects of the next pass on multi-layer multi-pass welding of low-alloy steel and duplex stainless steel, ER2209 welding wire was single-layer single-pass deposited on the surface of Q345B hot-rolled plate by gas metal arc welding (GMAW). The microstructure and corrosion resistance of welded joints were studied by different arc energies. The results showed that the arc energy had a significant impact on the “tongue-shaped” morphology and the width of heat affect zone in the welded joint, which in turn affected the corrosion performance of the welded joints. Due to the least distribution of “tongue-shaped” morphology and minimum width of heat affected zone in the welded joint with arc energy of 0.645kJ/mm, it owned the best corrosion resistance. The weld metals of the welded joints were composed of ferrite and austenite phases. The ferrite phases were distributed along grain boundaries and intergranular. As the heat input increases, the distribution of ferrite phase along grain boundaries gradually decreased. The corrosion products and corrosion morphology of the welded joint were also investigated and the corrosion mechanism was discussed in detail. The research results of this article provide a theoretical basis for improving the corrosion performance of multi-layer multi-pass welded joints of low-alloy and duplex stainless dissimilar steels.

A novelty in the precipitation of the σ-phase in superaustenitic stainless steel weld metals

A novelty in the precipitation of the σ-phase in superaustenitic stainless steel weld metals

Experimental Determination and Simulation Validation: Johnson–Cook Model Parameters and Grinding Simulation of 06Cr18Ni11Ti Stainless Steel Welds

Hydrogen permeation resistance in the welded region of 06Cr18Ni11Ti steel is relatively weak due to surface defects, which need high integrity surface machining. The parameters of the welding material for 06Cr18Ni11Ti steel are currently unavailable, which causes some inconvenience for simulation studies. To fill the lack of 06Cr18Ni11Ti steel weld material parameters in the relevant literature at the present stage, the quasi-static tensile test at different strain rates and notch specimen tensile tests were conducted in this paper and determined the Johnson–Cook (J-C) constitutive model parameters and Johnson–Cook failure model parameters. Subsequently, a multi-grain grinding simulation model was built based on W-M fractal dimension theory by using the determined material parameters. The influence of processing parameters on grinding heat was analyzed. Grinding experiments were conducted to analyze the influence of processing parameters on grinding heat and grinding force. By comparing the simulation and experimental results, it is revealed that the average error is 9.37%, indicating relatively small discrepancy. It is demonstrated that the grinding simulation model built in this paper could efficiently simulate the grinding process, and the determined weld material parameters of 06Cr18Ni11Ti steel have been verified to possess high accuracy and reliability.

Low and High Gas Tungsten Arc Welding Heat Inputs Influence on Corrosion of Stainless Steel Weldments

In this study, influence of low and high heat inputs on corrosion susceptibility of 304L austenitic stainless steel (ASS) in simulated 0.5 molar solution of NaCl was investigated. Gas tungsten arc welding (GTAW) was used to generate low and high levels welding heat input. Microstructures of the weldments were examined, using metallurgical optical microscope (OMM) (Olympus GX51), while the corrosion behaviours were evaluated by potentiodynamic polarization tests, and corrosion data were recorded, using a computer-based data logging system – Autolab PGSTAT 204N. From the results, the evolving microstructures of the weldments before corrosion were characteristically heterogeneous; austenite (γ) was the leading phase, while ferrite (α) grains were dispersed within the γ matrix. Fusion zone (FZ) and heat affected zone (HAZ) microstructures after corrosion were characterised by pits of varying sizes with different alignments. And at GTAW speed, current and voltage of 7.2 mm/s, 200A and 40V, corresponding to low heat inputs, there were few number and size of pits relative to 1.7 mm/s, 200A and 40V, corresponding to high heat input. Shift in corrosion potentials (Ecorr) toward less negative direction, that is more nobility was observed at the low heat inputs induced GTAW parameters as compared to the corresponding high heat inputs induced GTAW parameters. In general, corrosion susceptibility of 304L ASS in the simulated 0.5 molar solution of NaCl was heightened at high heat inputs induced GTAW parameters as compared to the corresponding low heat inputs parameters.

Effects of irradiation plus thermal aging on the phase boundary microstructure of austenitic stainless steel welds

Irradiation damage and thermal aging greatly affect the phase boundary microstructure and stress corrosion cracking of austenitic stainless steel weld metals (ASSWMs) in water-cooled nuclear reactors. However, the effects of irradiation plus thermal aging (I + A) on the phase boundary segregation and phase changes remain unclear. Phase changes and elemental segregation at the carbide and carbide-free phase boundaries of 308 L ASSWMs after I + A treatment were investigated using atom probe tomography and transmission electron microscopy. The I + A treatment induced Si depletion at the phase interfaces of δ-ferrite/austenite (δ/γ) and δ-ferrite/carbide (δ/C) and also induced Ni enrichment and Cr depletion with concentrations having the order Ni/Cr(δ/γ) > Ni/Cr(δ/C) > Ni/Cr(γ/C). The solute-defect binding model and the vacancy mechanism were applied to explain the phase boundary segregation. Furthermore, the I + A treatment affected microstructural evolution near the phase boundaries; this reduced spinodal decomposition and inhibited G-phase and Ni/Si-rich-cluster formation. The phase separation of δ-ferrite near δ/γ and δ/C phase boundaries differed with the distance from the boundary, forming a gradient microstructure from phase boundaries to δ-ferrite internally. The gradual precipitation of the G-phase was observed beyond about 15 and 10 nm from the δ/γ and δ/C interfaces, respectively; moreover, the growth of α'-phase in the δ-ferrite was accelerated with increasing distance from the δ/γ and δ/C interfaces.

Reducing capillary depth fluctuations in high-speed laser welding of stainless steel using multi-core laser technology

Laser welding was carried out in AISI304 (X5CrNi18-10) stainless steel using a multi-core fiber laser. High-speed X-ray imaging was used to monitor the process. When employing core-power only (400W) at high welding speeds (12m/min), the capillary depth was found to be inconsistent. The capillary penetration into the material varied from approximately 0.8 mm to approximately 0.2 mm, with fluctuation periods of between single milliseconds and tens of milliseconds. Employing a 0.5:0.5 ring-core power distribution (390W:390W) to achieve the same penetration (0.8mm) was found to reduce fluctuations in the depth of the welding process and the capillary penetration. Possible reasons for this reduction in depth fluctuations are discussed together with a detailed description of the resulting changes in weld cross-section.