Search

Hot cracking free fusion welds of re-sulphurized, high machinable grade stainless steel AISI 416 were obtained while adopting Laser-arc Hybrid Welding (LAHW) with the use of Ni-Cr-Mo rich austenitic filler metal. The carbon enriched martensite was observed at the interface of weld region, which, in turn, contributed for an elevated hardness. Both gamma ray non-destructive testing and cross-sectional analysis further affirm the absence of porosity and solidification cracking in the weld region of AISI 416. Mechanical integrity of the joints were established using tension and Charpy V-notch impact tests. Notch tensile studies revealed that the joint strength was much higher compared to the base metal. A slight delineation in notch impact toughness of the LAHW joints is ascribed to the formation of sulphide inclusions. The outcomes of the study recommend the use of the LAHW for joining difficult-to-weld metals. [ABSTRACT FROM AUTHOR]

The fusion zone microstructure and mechanical properties of UNS S32750 joints obtained from gas tungsten arc (GTA), gas metal arc (GMA) and flux cored arc (FCA) welding processes were investigated. The formation of grain boundary, Widmanstätten and intragranular austenite were observed in the fusion zone of the weldments. Electron back scattered diffraction (EBSD) analysis confirmed the presence of chi (ψ) and sigma (σ) phases in the reheated fusion zones of all the weldments. Tensile failures occurred at the fusion zone for all the weldments and the joint efficiency was found to be greater for GTA welds than the others. The number of welding passes and heat input had a significant impact on the ferrite: austenite ratio. FCA weldments experienced inferior notch toughness at both room temperature and sub-zero temperature owing to the prominent amount of secondary austenite and precipitation of intermetallic phases compared to the other weldments. [ABSTRACT FROM AUTHOR]

This study addressed the use of activated flux SiO for the gas tungsten arc (GTA) welding of super-austenitic stainless steel plates of 5 mm thickness. Trials were carried out to investigate the effect of flux and the welding current to determine the depth of penetration. Bead-on-plate trials were carried out on the AISI 904L with and without flux. It was inferred from the macrostructure studies that with a welding current of 180 A, complete penetration could be achieved using flux-assisted GTA welding. The optimal process parameters were validated by conducting the experimental investigations to ascertain the structure-property relationships of flux-assisted GTA weldment. Experimental results corroborated that the average tensile strength and impact toughness of SiO flux-assisted GTA weldments of AISI 904L were observed as 553 MPa and 49.3 J. It was inferred from the studies that defect-free welds of super-austenitic stainless steel could be obtained on employing flux-assisted GTA welding process. [ABSTRACT FROM AUTHOR]

This research work articulated the effect of SiO 2 flux assisted tungsten inert gas (TIG) welding on the microstructure and mechanical properties of marine grade stainless steel weldments, such as super-duplex stainless steel (UNS S32750) and austenitic stainless steel (AISI 316L). The studies showed that the use of flux decreased the heat input required to obtain complete penetration. Microstructure studies revealed the presence of ferrite at the heat affected zone of AISI 316L and the fusion zone which obviated the hot cracking tendency. Tensile studies corroborated that the joint strength was sufficiently greater than that of the parent metals. Impact toughness slightly impoverished owing to the presence of large platelets of Widmanstätten austenite in the fusion zone. The study also explored the structure–property relationships of the flux assisted weldments using the combined techniques of optical and scanning electron microscopy analysis. Owing to the better metallurgical and mechanical properties, this study recommends the use of SiO 2 flux for joining the dissimilar metals involving austenitic and super-duplex stainless steels. [ABSTRACT FROM AUTHOR]

This study addresses the comparison of metallurgical and mechanical properties of autogeneous and activated compound flux assisted gas tungsten arc welding (GTAW) of super-austenitic stainless steel, AISI 904L. The use of compound flux containing 85% SiO 2 –15% TiO 2 acquainted for better depth of penetration compared to autogeneous welding. Segregation of Mo rich phases was witnessed in the fusion zone of flux assisted AISI 904L. Tensile studies showed that the fracture occurred at the fusion zone for both the weldments. Ductility was found to be greater for the flux-assisted weldments. The present study also investigates the structure–property relationships of AISI 904L weldments using the combined techniques of optical and scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Highlights: [•] Effect of filler metals on the weldability of super-duplex stainless steel plates. [•] Contemplative explanations on the metallurgical and mechanical properties of the weldments. [•] Enhanced mechanical properties of the welds at ambient room temperature. [ABSTRACT FROM AUTHOR]

The pulsating current approach in tungsten inert gas (TIG) welding is adapted for joining Hastelloy C-276. Microstructure examination revealed the absence of micro-segregation while employing UNS N06022 filler. Due to the prevalence of higher tensile stresses in the un-peened conditions, tensile failures were observed in the weld regions of both the joints irrespective of fillers. Low energy laser shock peening without coating (LSPwC) was carried out on the weld zones on both the sides of the joints with the pulse densities 2500 and 7500 pulses per cm2. This laser surface treatment had remarkably increased the tensile strength of the welded joints by shifting the location of tensile failures well away from the fusion zones for all the cases. Similarly, a considerable increase is observed in the notch toughness of both the joints in the LSPwC condition. The enhancement in tensile strength and notch impact toughness of the welds could be ascribed to the residual compressive stresses induced which were then confirmed by Sin2ψ method in X-ray diffraction (XRD) technique. [ABSTRACT FROM AUTHOR]

• Similar joining of alloy 625 was employed using ERNiCrMo-4 fillers by Pulsed GTA method. • Oxidation and corrosion studies were performed on the weldment at 700 °C. • Kinetics of weldments was expressed by the thermogravimetric method. • Oxide scale formation and damage mechanism were derived. Alloy 625 joining was employed by pulsing current gas tungsten arc (PCGTA) welding method using ERNiCrMo-4 filler wire. The cyclic high-temperature performance of the weldments was investigated at 700 °C in molten salt (MS) K 2 SO 4 -60 %NaCl and air environment. The weldments' corrosion kinetics were accessed by the weight change method. A thin scale with no significant failure was found on the surface of the oxidized weldment. The oxide scale cracking and spallation occurred on the weldment in MS condition due to the deposited salts. The damage mechanism of the scales developed on the weldments is discussed in MS condition. [ABSTRACT FROM AUTHOR]