Weld Filler Metal Research Articles

Evaluation of microstructure, mechanical properties and pitting corrosion in dissimilar of alternative low cost stainless steel grade 204Cu and 304 by GTA welding joint

In this present work, solutions are sought regarding the problems of dissimilar welding of austenitic stainless steel for industrial fabrication work. There is support for the popular 200 grade stainless steel as a low-cost alternate to for 300 series grade in developing countries in Southeast Asia, especially Thailand, Vietnam, Myanmar, Laos and Cambodia. This study evaluates the microstructure, mechanical properties and pitting corrosion of dissimilar welding of the alternative low cost stainless steel grades 204Cu and 304 employing a GTA welding process by using different filler metals, namely 309L and 316L. It was found that for both weld metals and both filler metals the melting area in 204Cu BM side was larger than the 304 BM side. The delta-ferrite content in the weld metal of 309L was lower than 316L, HAZ and PMZ on the 204Cu side was wider than the 304 side of both welded metals. For the mechanical properties, the hardness volume of the welded metal of the 309L was higher than the 316L. Hardness adjacent to the fusion line of the 304 side was lower than the 204Cu side of both the filler metals. The tensile strength of the welded metal of 316L was more than the 309L and both welded metals ductile fractured in the welded zone (close to the 304 BM side). The pitting corrosion resistance of the welded metal for 309L was higher than for 316L and both welded metals initiated pitting at the boundary between the austenite phase and the delta-ferrite phase.

Effects of Ni powder addition on microstructure and mechanical properties of NiTi to AISI 304 stainless steel archwire dissimilar laser welds

In this study, dissimilar laser welding of NiTi to stainless steel (SS) orthodontic archwires was investigated. As a novel and more operational approach, Ni powder was used as a weld filler metal to improve the properties of joints in laser welding of these alloys. Therefore, welding was performed in two conditions, with and without Ni powder addition, and the results were compared. Optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and focused X-ray diffraction (micro-XRD) analysis were used to study the microstructure, chemical composition and phase characteristics of joints. The Fe-Ni-Ti ternary phase diagram was used as a tool to analyze the phase changes in weld zone with chemical composition variations in two conditions. Results showed that brittle intermetallics such as Fe2Ti and Cr2Ti were formed in zones close to NiTi weld interface in joints without Ni powder addition. However, Ni powder had favorable effects on microstructure, chemical composition and mechanical properties of laser welded joints. In fact, use of Ni powder changed primary solidifying phase region from Fe2Ti to ductile phases of Ni3Ti and γ, and consequently promotes the formation of these ductile phases in the weld zone. Moreover, as a result of chemical composition dilution by Ni, the microstructure of weld zone changed from dendrite to dendrite-cellular structure by suppressing the constitutional undercooling in Ni powder added condition. Furthermore, microhardness tests revealed that the addition of Ni powder caused the average hardness of weld zone to decrease from 580 HV down to 325 HV due to aforementioned intermetallic phase replacement. On the other hand, tensile properties of joints were improved and reached to a tensile strength of 300 MPa and a fracture strain of 2.9 % by adding Ni powder. These values for the welding without Ni powder addition were 150 MPa and, 1.8 %, respectively.

Microstructure and grain boundary engineering of a novel Fe-Cr-Ni alloy weldment made with self-developed composition-matched weld filler metal

The microstructure, texture, and yield strength of an advanced heat-resistant alloy weldment made with composition-matched weld filler were investigated. Scanning electron microscopy, energy dispersive spectroscopy, and electron backscatter diffraction were used to characterize the microstructural and textural changes. Various grain boundary engineering (GBE) processes were performed on the weldment. The yield strengths of the weldment at 973 K were obtained before and after GBE processing, and were mostly consistent with the theoretically predicted values. The coincident-site lattices, misorientation, and recrystallization of the weld metal after GBE were analyzed, and the results indicate that the increase in dislocation density and the improvement in special grain boundaries in the weld metal are the main reasons for the yield strength elevation of the weldment after GBE. The variation in elongation after high-temperature tests has the same tendency as that in the impact toughness with different GBE parameters, which is related to the coarsening behavior of carbides.

Steel-Reinforced Polyethylene Pipe: Extrusion Welding, Investigation, and Mechanical Testing

This work presents extrusion welding with a square butt joint of V-shaped steel-reinforced polyethylene (SRPE) corrugated pipe. The SRPE pipe was welded in a single pass on the inside of the pipe. The welding temperature was controlled at 190°–200°C. The welding extruder was modified for controlling the travel speed and preheating conditions for welding. A high-density polyethylene (HDPE) rod was used as the welding filler metal, which was inserted into the extruder with a speed of 2.20 m/min. Welding progressed downhill from the overhead position with a travel speed of 3.0 cm/min. The effects of welding methods, with and without preheat conditions, on the weld quality were investigated by visual and radiographic inspections. From the results, the preheated welding condition showed complete fusion of the weld without any defects, while that of the nonpreheat exhibited a great number of voids inside the weld. The crystal structures of the preheated and nonpreheated welds were analyzed with an x-ray diffractometer and compared with the HDPE base material. From mechanical testing, the weld from the preheat condition showed a good ability to endure the tension force of 46 MPa and compressive stress of up to 0.41 MPa at 5%deflection. In addition, it was found the welded SRPE could tolerate hydrostatic pressure of up to 0.18 MPa without any water leakage when being used as a water-containing tank.

Effect of Molybdenum on Metallurgical and Wear Properties of Fe–Cr–C Hard facing alloy

In this research, Surface hardening was performed by two types of Flux Cored Arc Welding (FCAW) filler metals based on Fe–Cr–C and Fe–Cr–C–Mo at the single, two and three- pass modes on the plain carbon steel. To evaluate the metallurgical and mechanical properties of hard facing layers, the optical microscope metallography, Scanning Electronic microscope, X-ray Diffraction test, hardness testing, Microhardness test and abrasion test was applied. Adding (1.1– 1.3) molybdenum to the Fe–Cr–C filler rod led to the formation of complex carbides of M7C3, in the microstructure. By increasing molybdenum, the wear resistance and hardness of the weld layers increased so that three-layers weld hardness reached to 62 HRC. Also, the hardness of complex carbides is 1299 HV which increased to 1596 HV by adding molybdenum.

Microstructure and mechanical properties of laser welded TC4 titanium alloy/304 stainless steel joint with (CoCrFeNi)100-xCux high-entropy alloy interlayer

The feasibility of (CoCrFeNi)100-xCux high-entropy alloy filler metal for laser welding between TC4 titanium alloy and 304 stainless steel is investigated. Reliable metallurgical bonding was achieved between weld zone and 304 stainless steel. The weld zone consisted of ductile FCC solid solution phase and Cu-rich phase which segregated at the grain boundary of FCC phases. The Ti/Cu transition zone is composed of Ti-rich layer near TC4 titanium alloy substrate and Ti-depleted layer adjacent to the weld zone. Ti-rich IMCs and β-Ti phases formed in Ti-rich layer, and Ti(Fe,Co,Cr)2 and Ti(Fe,Ni)2 phases formed in Ti-depleted layer. With increase of Cu content in filler metal, the segregated Cu-rich phase in weld zone increased, and Ti(Fe,Co,Cr)2 and Ti(Fe,Ni)2 phases decreased along with the increase of (Fe,Cr)-rich phase and segregated Cu-rich phase. The tensile strength of the joint with CoCrFeNi filler metal was 158 MPa, and it decreased with increase of Cu in filler metal until the atomic percent of Cu reached 27.27 at. %, but raised to 161 MPa while using (CoCrFeNi)66.67Cu33.33 filler metal. All joints fractured through the transition zone, and the maximum microhardness of the transition zone reached 803 HV, higher than those of substrates and weld zone. The formation of Ti(Fe,Co,Cr)2 and Ti(Fe,Ni)2 phases resulted in the limited tensile strength and high microhardness in the transition zone.

The Welding of Dissimilar Joints with Low Temperature Martensitic Transformation Filler Material

Abstract The welding of dissimilar joints is very common in systems used in oil exploration and production in deep waters. This commonly involves welding low carbon steel pipes with valves, pumps or other pipes, all of them made of alloy steel. Inconel has been used in such welding as filler material; however, this welding is preceded by a process of buttering in the low alloy steel side and a stress relief heat treatment. An alternative technique presented in this paper is the use of a welding filler metal that, during the cooling process, undergoes a martensitic transformation at a relatively low temperature, so that the resulting deformation processing offsets the contraction that occurs as a result of the cooling process. This study evaluates the application of Maraging 250 weld in a dissimilar joint of the oil industry. Tests were performed on joints of ASTM steels A516 grade 70 and AISI 8630M welded with Maraging 250. The residual stress profiles, hardness, microstructure, tensile strength and impact energy absorbed were evaluated. The welded joint with Maraging 250 showed a high intensity of compressive residual stress. The microstructure of different welding regions was analysed and compared.

Alloy design of welding filler metal for 9Cr/2.25Cr dissimilar welded joint and mechanical properties investigation

In the work, a 5%Cr weld metal for the 9Cr/2.25Cr dissimilar welded joint was designed. The creep rupture, tensile, and impact behaviors of the weld metal and welded joint were tested and compared with those of the dissimilar welded joint with the 2.25%Cr weld metal. The result showed that the alloy design of the 5%Cr weld metal had a significant effect on reducing the degree of carbon migration at the joint interface. The interfacial creep damage and early failure tendency were reduced greatly. V and Nb in combination with N were added to enable creep strength at elevated temperatures by the formation of MX particles. Creep rupture tests at 540 °C showed good agreement with the alloy design, and no failures were observed in the weld metal for long-term cross-weld creep specimens, indicating that the newly designed 5%Cr weld metal was of adequate creep strength for use with dissimilar welded joint. The excellent tensile strength and adequate toughness showed good agreement with the rationality of tempering parameters.

Effect of Laser Welding Process Parameters and Filler Metals on the Weldability and the Mechanical Properties of AA7020 Aluminium Alloy

This research work aims at finding the optimum process parameters for the laser welding of AA7020 aluminium alloys. The use of 7xxx series alloys is limited because of weldability problems, such as hot cracking, porosity, and softening of the fusion zone despite its higher specific strength-to-weight ratio. AA7020 aluminium alloy was welded while varying the process parameters so as to obtain optimal welding efficiency. The welded samples were analysed to reveal the microstructure, defects, and mechanical properties of the welded zone. The samples were prepared from a plate of AA7020, which was hot rolled at a temperature of 470 °С to a thickness of 1 mm. The welding was carried out at an overlap of 0.25 mm, duration of 14 ms and argon shield gas flow rate of 15 L/min. Process parameters, such as peak power, welding speed, and pulse shaping, were varied. The samples were welded with Al-5Ti-B and Al-5Mg as filler metals. The welding speed, peak power, and pulse shaping have a great influence on the weldability and hot cracking susceptibility of the aluminium alloy. Al-5Ti-B improves the microstructure and ultimate tensile strength of AA7020 aluminium alloy.

Design and performance of weld filler metal to match an advanced heat-resistant Fe-Cr-Ni alloy

In the present study, a novel welding filler metal with alloying system of Fe–22.5Cr–25Ni–2Mn–0.45Si–1.5Co–3.8W–3Cu–0.5Nb–0.2N–C–B was manufactured to match an advanced heat-resistant alloy Sanicro 25. The corresponding all-weld-metal deposits were prepared to carry out microstructure and mechanical properties inspection with compared to Sanicro 25. Elemental redistribution occurs in interfaces between intermediate layer and deposited metal, which has an influence on toughness and microhardness. The filler metal presents superior strengths than Sanicro 25, which was checked by comparatively calculating the yield tensile stress. Transmission electron microscope observation verified the existence of nano-sized precipitation in the deposit after high-temperature tests. Moreover, the quantitative fractography analysis were conducted over the ruptured specimens after tensile tests, which confirms the influence of element boron on eradicating the coarse intergranular carbides.

Effect of Pulse Laser Welding Parameters and Filler Metal on Microstructure and Mechanical Properties of Al-4.7Mg-0.32Mn-0.21Sc-0.1Zr Alloy

The effect of pulse laser welding parameters and filler metal on microstructure and mechanical properties of the new heat-treatable, wieldable, cryogenic Al-4.7Mg-0.32Mn-0.21Sc-0.1Zr alloy were investigated. The optimum parameters of pulsed laser welding were found. They were 330–340 V in voltage, 0.2–0.25 mm in pulse overlap with 12 ms duration, and 2 mm/s speed and ramp-down pulse shape. Pulsed laser welding without and with Al-5Mg filler metal led to the formation of duplex (columnar and fine grains) as-cast structures with hot cracks and gas porosity as defects in the weld zone. Using Al-5Ti-1B filler metal for welding led to the formation of the fine grain structure with an average grain size of 4 ± 0.2 µm and without any weld defects. The average concentration of Mg is 2.8%; Mn, 0.2%; Zr, 0.1%; Sc, 0.15%; and Ti, 2.1% were formed in the weld. The ultimate tensile strength (UTS) of the welded alloy with AlTiB was 260 MPa, which was equal to the base metal in the as-cast condition. The UTS was increased by 60 MPa after annealing at 370 °C for 6 h that was 85% of UTS of the base alloy.

Dissimilar welding between SAF 2507 stainless steel and Incoloy 825 Ni-based alloy: The role of microstructure on corrosion behavior of the weld metals

The effect of the filler metal type, welding process and the welding pass number on the corrosion behavior of Incoloy 825 Ni-based alloy to SAF 2507 super duplex stainless steel weld zones were addressed utilizing scanning electron microscopy, cyclic potentiodynamic polarization and electrochemical impedance spectroscopy. The results detailed the formation of some secondary phases in the weld metals. The welds employing Ni-based filler wires revealed the highest general corrosion resistance, while super duplex stainless steel weld metals displayed the best pitting corrosion behavior. Pulsed current gas tungsten arc welding and super duplex stainless steel filler metal were recommended to obtain the optimum surface corrosion resistance.

Effect of mechanical mismatch on fracture mechanical behavior of SA 508 – Alloy 52 narrow gap dissimilar metal weld

In modern pressurized water reactor (PWR) designs, dissimilar metal welds (DMW) between the reactor pressure vessel (RPV) nozzles and safe-ends connected to the main coolant pipes are manufactured using a narrow-gap welding (NGW) technique. In addition to the new weld design, the filler metals have been changed from conventional Alloys 82 and 182 to higher Cr containing Alloys 52 and 152 to ensure the structural integrity of the welds during long term operation. The changes in weld design and filler metal have an effect on the mechanical mismatch state of the DMW which has an effect on the fracture behavior of the weld. For the experimental determination of the local strength variations and the fracture mechanical behavior of a modern NG-DMW, a weld mock-up consisting of SA 508 pressure vessel steel with AISI 309L/308L cladding, AISI 304 piping steel, and Alloy 52 weld metal was manufactured. The NG-DMW was characterized in both as-welded and post-weld heat treated (PWHT) conditions. The results showed that the highest strength mismatch existed between the carbon-depleted zone (CDZ) in the SA 508 heat-affected zone (HAZ) and the Alloy 52 weld metal. High fracture toughness values were observed for the different zones of the weld and the crack propagation occurred towards the softer SA 508 HAZ CDZ.

Microstructure and mechanical properties of Al/ZrC/TiC hybrid nanocomposite filler metals of tungsten inert gas welding fabricated by accumulative roll bonding

In this study, a new type of nanocomposite tungsten inert gas (TIG) welding filler metals with a matrix of 4043 aluminum alloy and hybrid reinforcement of ZrC and TiC nanoparticles was fabricated for the first time by accumulative roll bonding (ARB). After welding, microstructural characterizations were performed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Furthermore, the mechanical properties of hybrid nanocomposite welds were investigated by tensile and microhardness tests. The microstructural observations revealed that employing the ARB process has led to a significant grain refinement and a uniform distribution of the ceramic nanoparticles in the weld. The test results showed that using Al/ZrC/TiC hybrid nanocomposite filler metals improved considerably the tensile strength of weld.

Gas Metal Arc Welding Using Novel CaO-Added Mg Alloy Filler Wire

Novel “ECO Mg” alloys, i.e., CaO-added Mg alloys, which exhibit oxidation resistance during melting and casting processes, even without the use of beryllium or toxic protection gases such as SF6, have recently been introduced. Research on ECO Mg alloys is still continuing, and their application as welding filler metals was investigated in this study. Mechanical and metallurgical aspects of the weldments were analysed after welding, and welding behaviours such as fume generation and droplet transfer were observed during welding. The tensile strength of welds was slightly increased by adding CaO to the filler metal, which resulted from the decreased grain size in the weld metal. When welding Mg alloys, fumes have been unavoidable so far because of the low boiling temperature of Mg. Fume reduction was successfully demonstrated with a wire composed of the novel ECO Mg filler. In addition, stable droplet transfer was observed and spatter suppression could be expected by using CaO-added Mg filler wire.

An Investigation of the Microstructure of an Intermetallic Layer in Welding Aluminum Alloys to Steel by MIG Process.

Butt joints of A5052 aluminum alloy and SS400 steel, with a new type of chamfered edge, are welded by means of metal inert gas welding and ER4043 Al-Si filler metal. The microhardness and microstructure of the joint are investigated. An intermetallic layer is found on the surface of the welding seam and SS400 steel sheet. The hardness of the intermetallic layer is examined using the Vickers hardness test. The average hardness values at the Intermetallic (IMC) layer zone and without the IMC layer zone were higher than that of the welding wire ER4043. The tensile strength test showed a fracture at the intermetallic layer when the tensile strength is 225.9 MPa. The tensile value test indicated the average of welds was equivalent to the 85% tensile strength of the A5052 aluminum alloy. The thickness of the intermetallic layers is non-uniform at different positions with the ranges from 1.95 to 5 μm. The quality of the butt joint is better if the intermetallic layer is minimized. The Si crystals which appeared at the welding seam, indicating that this element participated actively during the welding process, also contributed to the IMC layer’s formation.

Impact of the hard facing technology and the filler metal on tribological characteristics of the hard faced forging dies

Subject review The forging dies are parts, which are operating at elevated temperatures, while simultaneously subjected to variable loads that can be compressive even impact and shear. Impact of the hard facing technology is very strong since varying of the hard facing parameters directly affects the output characteristics of the hard faced layers. The criterion for estimating that impact was based on results of performed tribological investigations. The tribological parameters that were monitored were the friction coefficient, the wear scar/trace width and the wear area of the hard faced layers, with the two different types of lubricants. Hard facing technology implied selection of the welding process, filler metals, preheating temperatures and other parameters of the hard facing process. The influence of the proposed hard facing technology was determined by monitoring hardness, microstructure and wear resistance of the executed joints after the hard facing and after tempering. The objective of this work was to establish the correlation between the selected hard facing technology, filler metals and applied heat treatment on mechanical and tribological characteristics of the executed hard faced layers.

Novel manufacturing process of nanoparticle/Al composite filler metals of tungsten inert gas welding by accumulative roll bonding

In the present work, accumulative roll bonding (ARB) was used as an effective method for manufacturing nanoparticle/Al composite filler metals of tungsten inert gas (TIG) welding. After welding, the distribution of ceramic nanoparticles and mechanical properties of welds were investigated. By applying ARB, ceramic nanoparticles were uniformly dispersed in the composite filler metals. Consequently, the welds produced by these filler metals had a uniform dispersion of ceramic nanoparticles in their compositions. The test results showed that the yield strength of welds was greatly increased when using the nanoparticle/Al composite filler metals. The improvement in the yield strength was attributed to the coefficient of thermal expansion mismatch and Orowan strengthening mechanisms. Therefore, according to the results presented in this paper, it can be concluded that the nanoparticle/Al composite filler metals can serve as a novel filler metal for TIG welding of aluminum and its alloys.

Numerical evaluation of the effects of a mitigation treatment on the residual stresses of a tubular dissimilar metal weld

Dissimilar metal welds (DMW) between ferritic steel pipes and austenitic steel nuclear components are located in the primary coolant circuit of pressurized water reactors. Those tubular joints, made using an Inconel weld filler metal which is known to be susceptible to stress corrosion cracking, showed in the past some weaknesses, as encountered in particular in the USA and Japan, where stress corrosion cracks have been observed. In this context, the goal of this work is to optimize the manufacturing of these dissimilar joints in order to decrease the negative effects of welding residual stresses regarding these integrity defects. We present in this paper a numerical evaluation of the residual stresses of a specific tubular dissimilar weld, and the numerical setup and evaluation of a mitigation treatment which allows redistributing more favorably the residual stresses. The present work focuses on identifying mitigation process key parameters affecting the residual stresses field. The feasibility of this mitigation treatment is quite encouraging for the studied geometry and materials which could justify an experimental evaluation in the future.

Benefits of low-yield weld filler metals for safe welding on live gas transmission pipelines

Making connections in gas pipelines that may not be taken out of service requires special techniques. Hot tapping is often applied. Split tees are welded to pipelines that are and remain completely operational. The split tees are placed on the pipeline and then welded together using longitudinal welds to make one tee piece. After inspection, circumferential welds are made to create the connection between the tee piece and the pipeline. This same welding technique is also used to repair damage to pipelines. This can be in the form of a buttering up (surfacing) repair as part of a pipeline rehabilitation program or installing full-encirclement repair sleeves. Installing repair sleeves can also be a follow-up to an in-line inspection that has established that there is damage to the pipeline or to an activity that has been reported as doing damage as a result of external interference (e.g., excavation, trenchless techniques for installation of cables or other pipelines, plowing). N.V. Nederlandse Gasunie has had research conducted since 1978 by, among others, Netherlands Organization for Applied Scientific Research (TNO) in order to obtain a sound basis for a reliable and safe way to weld on live gas pipelines. This article covers over 20 years of operational experience with welding on live gas transmission pipelines. The article addresses regulations, critical aspects of welding on operational gas pipelines, and the control of these critical aspects. The metallurgical background issues are also discussed.