Stainless Steel Dissimilar Joints Research Articles

Microstructure evolution of TC4 titanium alloy/316L stainless steel dissimilar joint vacuum-brazed with Ti-Zr-Cu amorphous filler metal

TC4 titanium alloy was vacuum-brazed to 316L stainless steel (SS) with Ti-Zr-Cu amorphous filler metal. The effect of brazing time and temperature on the interfacial microstructure and mechanical properties of joints was investigated. Electron probe micro-analyzer (EPMA) and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) were used to study the joint microstructure; meanwhile, the reaction phases on fracture surfaces were identified by X-ray diffraction (XRD). The results show that all joints had similar interfacial microstructure of TC4 titanium substrate/Widmanstatten/β-Ti + Ti2Cu/(α-Ti + λ-Cu2TiZr) + Ti2Cu/Ti-Fe-Cu/TiFe/(Fe, Cr)2Ti/σ-phase + Fess/316L stainless steel substrate. Three reaction layers TiFe/(Fe, Cr)2Ti/σ-phase + Fess formed close to 316L stainless steel substrate and could benefit the mechanical properties of joints. The maximum shear strength of 65 MPa was obtained at 950 °C for 10 min. During shear test, cracks initiated at the interface of Ti-Cu-Fe layer/TiFe layer and propagated along the brazed seam/316L interface with a large amount of cleavage facets existing on the fracture surface.

Microstructural Characterization and Mechanical Properties of TIG-Welded API 5L X60 HSLA Steel and AISI 310S Stainless Steel Dissimilar Joints

Dissimilar joining of API 5L X60 ferritic HSLA steel and AISI 310S austenitic stainless steel was conducted by tungsten inert gas (TIG) welding process using ERNiCr-3, ER310, ER2209, and ER309L filler metals. Microstructural characteristics and mechanical properties of the weldments were studied using optical and scanning electron microscopy, ferritometry, microhardness, tensile, and impact tests. The microstructure investigations revealed macro-segregation occurrence and formation of Type II boundaries at the interface of welds with API 5L X60 steel. In tension tests, the joints prepared by ER2209 filler metal showed the maximum yield and ultimate tensile strength values, and the failures were always obtained at the side of API 5L X60. The results of Charpy impact tests indicated that the maximum fracture energy is related to the weld made by ER2209 filler metal. At last, it was concluded that for the dissimilar welding between API 5L X60 and AISI 310S, the weld metal prepared by ER2209 duplex stainless steel filler metal offers the optimum properties at room temperature.

The effect of filler metal and butter layer on microstructural and mechanical properties of pure Cu to AISI304 stainless steel dissimilar joint

In this research, dissimilar joint properties of pure Cu to AISI304 stainless steel using three different filler metals were studied. In this regard, the welding process was done with gas tungsten arc welding process using ER308L, ER309L, and ERNiCrMo3 filler metals and ERNi1 butter layer. The microstructural evaluations were carried out using optical microscope and scanning electron microscope. The mechanical tests were conducted by microhardness, tensile, bending and impact tests, and the fracture surfaces of impact and tensile tests were studied by scanning electron microscope. The results show that there is no crack or discontinuity in the welded samples. Energy-dispersive spectroscopy analysis revealed that the diffusion of Cu from base metal to butter layer has been occurred during welding. The microhardness profiles indicated the increase of hardness in heat-affected zone and butter layer. The welded sample with ERNiCrMo3 filler metal showed higher microhardness (200 HV) as compared with two other welded samples. The welded sample with ER309L filler metal had lower microhardness of about 150 HV. The tensile test revealed that the welded sample with ER309L filler metal showed maximum (193 MPa) and the welded sample with ER308L showed minimum (147 MPa) of ultimate tensile strength. In bending test of the welded samples with ER308L and ERNiCrMo3 filler metals, the crack and discontinuity were revealed in weld metal and heat-affected zone of Cu, respectively, while in the welded sample with ER309L filler metal no crack and discontinuity were seen. Also the welded sample with ER309L filler metal had highest impact energy of about 90 J as compared to other samples (81 and 88 J for the welded samples with ER308L and ERNiCrMo3 filler metals, respectively). The welded sample with ER309L filler metal showed more ductile fracture surface as compared with other samples.

Inhomogeneous interface structure and mechanical properties of rotary friction welded TC4 titanium alloy/316L stainless steel joints

The inhomogeneous interface structure and mechanical properties along the radius direction of rotary friction welded TC4 titanium alloy/316 L stainless steel dissimilar joints were investigated under as-welded and post-weld heat treated conditions. The interface in the joint is convex-shaped on TC4 titanium alloy side and concave-shaped on 316 L stainless steel side. The mechanical properties of joints are highly correlated with the inhomogeneous interface structure and the dimension of tensile samples. The tensile strength of the as-welded entire joint was 117 MPa, while it dramatically increased to 419 MPa after post-weld heat treatment at 600 °C for 2 h due to homogenization of aggregated atoms. However, the sliced samples was relatively weak even after post-weld heat treatment, because the internal defects became surface crack sources after machining, and caused stress concentration and sharply reduced the strength of samples. All tensile samples failed through the interface. The X–ray diffraction patterns of TiC, Cr23C6, Fe2Ti, FeTi, FeNi3, AlTi3, CrTi4, NiTi and TiCr phases and the river-like features on fracture surfaces indicate a brittle quasi-cleavage fracture mode. C and Cr aggregated around the interface under as-welded condition. Nonetheless, elemental homogenization occurred in the joint after post-weld heat treatment.

Effects of austenitic and duplex electrodes on microstructure, mechanical properties, pitting, and galvanic corrosion resistance of ferritic and dual-phase stainless steel dissimilar joints

Abstract

Mechanical and microstructural evaluation of SAF 2507 and incoloy 825 dissimilar welds

This research work articulated a comparative study on Incoloy 825 Ni-based alloy and SAF 2507 super duplex stainless steel dissimilar joints. Welding was accomplished by ER2594 and ERNiFeCr-1 filler wires, pulsed current (PCGTAW) and continuous current gas tungsten arc welding (CCGTAW) techniques. Characterizations were conducted by optical microscopy, scanning electron microscopy equipped with an energy dispersive spectroscopy and X-ray diffraction. In order to investigate the evolution of mechanical properties of the weld joints’ micro-hardness, impact and tensile tests were employed. The results showed that Ti-rich phase was formed in weld zones employing ERNiFeCr-1 filler metal. On the other hand, Cr-rich phase was characterized in the weld zone of ER2594 sample employing CCGTAW. The welds of PCGTAW method displayed finer microstructure, lower ferrite contents and lack of Cr-rich phase formation. In tensile tests, fracture occurred at weaker base metals (Incoloy 825) in all cases. The use of ER2594 caused higher hardness and lower toughness than ERNiFeCr-1 filler metal. Based upon comparative investigations, ERNiFeCr-1 filler metal and PCGTAW technique were recommended to improve dissimilar joint efficiency.

Effect of Austenitic and Austeno-Ferritic Electrodes on 2205 Duplex and 316L Austenitic Stainless Steel Dissimilar Welds

This study addresses the effect of different types of austenitic and austeno-ferritic electrodes (E309L, E309LMo and E2209) on the relationship between weldability, microstructure, mechanical properties and corrosion resistance of shielded metal arc welded duplex/austenitic (2205/316L) stainless steel dissimilar joints using the combined techniques of optical, scanning electron microscope, energy-dispersive spectrometer and electrochemical. The results indicated that the change in electrode composition led to microstructural variations in the welds with the development of different complex phases such as vermicular ferrite, lathy ferrite, widmanstatten and intragranular austenite. Mechanical properties of welded joints were diverged based on compositions and solidification modes; it was observed that ferritic mode solidified weld dominated property wise. However, the pitting corrosion resistance of all welds showed different behavior in chloride solution; moreover, weld with E2209 was superior, whereas E309L exhibited lower resistance. Higher degree of sensitization was observed in E2209 weld, while lesser in E309L weld. Optimum ferrite content was achieved in all welds.

Effect of Continuous and Pulsed Current on the Metallurgical and Mechanical Properties of Gas Tungsten Arc Welded AISI 4340 Aeronautical and AISI 304 L Austenitic Stainless Steel Dissimilar Joints

In this research work, the weldability of low alloyed AISI 4340 aeronautical steel and AISI 304L austenitic stainless steel joined by continuous current (CC) and pulsed current (PC) gas tungsten arc welding (GTAW) techniques, using ER309L and ERNiCr-3 filler metals was investigated. The main focus of the study involves the investigation on the effect of continuous and pulsed current mode of GTA welding process on the metallurgical and mechanical properties of these dissimilar weldments. Microstructure studies revealed the formation of different zones across the weldments, vis-a-vis martensite at the HAZ of AISI 4340, vermicular δ - ferrite /ferrite stringers at the HAZ of AISI 304L, pearlite colonies at the parent metal of AISI 4340 and equi-axed cellular and/or columnar dendrites at the weld zone. Tensile results showed that current pulsing accrued better tensile properties. The structure - property relationships of these weldments were established based on the current modes employed by utilizing combined techniques of optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS).

Zonular evaluation of Inconel 617/310 SS dissimilar joint by shear punch test

Shear punch test technique is a novel method for zonular evaluation of weldment mechanical behavior. In this study, changes in the mechanical behavior of different zones of an Inconel 617/310 austenitic stainless steel dissimilar joint, including base metal, heat affected and weld metal zones were investigated by shear punch test. ERNiCrCoMo1 (Inconel 617) filler metal was used in order to achieve dissimilar joint through gas tungsten arc welding process. Furthermore, microstructural evaluation was performed using optical and scanning electron microscopies. The results indicated that by increasing the distance from weld centerline, hardness and ultimate strength values were initially decreased and then increased while ductility was constantly decreased. In this regard, the difference in grain sizes and the type of precipitates were considered the effective parameters.

Fatigue behaviour of friction welded medium carbon steel and austenitic stainless steel dissimilar joints

This paper reports the fatigue behaviour of friction welded medium carbon steel–austenitic stainless steel (MCS–ASS) dissimilar joints. Commercial grade medium carbon steel rods of 12mm diameter and AISI 304 grade austenitic stainless steel rods of 12mm diameter were used to fabricate the joints. A constant speed, continuous drive friction welding machine was used to fabricate the joints. Fatigue life of the joints was evaluated conducting the experiments using rotary bending fatigue testing machine (R=−1). Applied stress vs. number of cycles to failure (S–N) curve was plotted for unnotched and notched specimens. Basquin constants, fatigue strength, fatigue notch factor and notch sensitivity factor were evaluated for the dissimilar joints. Fatigue strength of the joints is correlated with microstructure, microhardness and tensile properties of the joints.

Characterizations of 21-4N to 4Cr9Si2 stainless steel dissimilar joint bonded by electric-resistance-heat-aided friction welding

A new welding process, electric-resistance-heat-aided friction welding (ERHAFW), was introduced in this study. To further improve the joint quality and energy-saving, electric resistance welding was combined with the conventional continuous-drive friction welding. 21-4N (austenitic stainless steel) and 4Cr9Si2 (martensitic stainless steel) valve steel rods of 4 mm diameter were used as base metals. The results show that electric-resistance-heat-aided friction welding can be applied to join thin rods within a relatively short time, which is very difficult for conventional friction welding (FW). The microstructure of ERHAFW bonded 21-4N to 4Cr9Si2 presents non-uniform across the joint. Different structure zones are observed from the weld line to both sides, which are the weld center, thermo-mechanically affected zone (TMAZ) and heat affected zone (HAZ). These regions exhibit different structures owing to the difference in the thermophysical and mechanical properties of these two steels under the fast heating and cooling during welding. The variation of microhardness in the joint is attributed to the microstructure change. The higher microhardness is obtained in the weld center and TMAZ of 4Cr9Si2 corresponding to the presence of fine tempered martensite and carbides.

Interfacial structure and bond strength of ultrasonic brazed Al–304 stainless steel dissimilar joints

A filler alloy (Zn–14 at.-%Al) was used to join aluminium to 304 type stainless steel by ultrasonic brazing at 673 K for different ultrasound application times. Different reaction layers could be observed at the interface, containing Fe–Al, Fe–Zn, and Al–Zn solid solutions. As the amount of these solid solutions increased at the interface, there was a gradual improvement in the joint bond strength. The maximum bond strength of 146 MPa was obtained for the Al–304 joint brazed at 673 K for 3 s ultrasound application time. A critical remaining thickness of the filler alloy after ultrasonic application improves the interfacial joining. Extending the ultrasound application time beyond 3 s causes a bulk escape of the brazing alloy from the interface and leads to a direct interaction between aluminium and 304, which increases the possibility of forming intermetallics, and consequently decreases the joint bond strength.