Showing papers on "Filler metal published in 2019"

Wire and Arc Additive Manufacturing of Aluminum Components

Abstract: An increasing demand for flexibility and product integration, combined with reduced product development cycles, leads to continuous development of new manufacturing technologies such as additive manufacturing. Wire and arc additive manufacturing (WAAM) provides promising technology for the near net-shape production of large structures with complex geometry, using cost efficient production resources such as arc welding technology and wire materials. Compared to powder-based additive manufacturing processes, WAAM offers high deposition rates as well as enhanced material utilization. Because of the layer-by-layer built up approach, process conditions such as energy input, arc characteristics, and material composition result in a different processability during the additive manufacturing process. This experimental study aims to describe the effects of the welding process on buildup accuracy and material properties during wire arc additive manufacturing of aluminum structures. Following a process development using pulse cold metal transfer (CMT-P), linear wall samples were manufactured with variations of the filler metal. The samples were analyzed in terms of surface finishing, hardness, and residual stress. Furthermore, mechanical properties were determined in different building directions.

Weldability of Duplex Stainless Steels - Thermal Cycle and Nitrogen Effects : Duplex stainless steel weld microstructures were investigated as a function of weld thermal cycles and shielding gas nitrogen content

Abstract: Much development work has been performed worldwide on the welding of duplex stainless steels (DSSs), where losses in base metal nitrogen during welding have been compensated by filler metal and nitrogen additions to the shielding gas. However, some heat-affected zone (HAZ) microstructural changes have not always responded consistently to nitrogen mixtures added to the shielding gas. In this work, DSS weld microstructures were investigated as a function of weld thermal cycles and shielding gas nitrogen content. Physical simulations, actual gas tungsten arc welding (GTAW) in controlled atmospheres, and entrapped nitrogen measurements were used to relate to the weld austenite-to-ferrite (A/F) phase ratios. Results showed the thermal cycles had a stronger effect on the weld A/F ratio than shielding gas nitrogen content. Physical simulations and actual GTAW trials also showed the A/F ratio changes in the opposite way in the fusion zone than in the HAZ. Reheating was also found to have an important effect on the microstructure. The above findings should allow fabricators to better design the welding process with DSS. Better control of nitrogen-containing shielding gas mixtures, along with heat input limitations, should result in more consistent weld properties and wider use of DSS by industry.

Improving the weld microstructure and material properties of K-TIG welded armour steel joint using filler material

Abstract: Motivated by the undesired microstructure and unsatisfactory weld properties during keyhole tungsten inert gas (K-TIG) welding process, the use of filler materials was introduced for the first time in K-TIG to modify the weld microstructure and improve weld properties. Single pass full penetration was achieved on 6.2 mm armour steel plate at a welding speed of 350 mm/min. The metal transfer behaviour, microstructure and mechanical properties of weld joint were analysed in detail. The results showed that the introduction of filler material was very effective in modifying microstructure and improving joint properties. The wire feeding speed can reach up to 300 cm/min without compromising full penetration, providing a great scope for microstructure modification. The applied austenitic filler material can significantly change the weld microstructure with just 6.7% dilution, along with much increased weld metal hardness and joint efficiency, matching the welds produced by using conventional arc welding processes with V-joint preparation and matching filler metal. The introduction of filler material dramatically expands the capability of K-TIG process and also shows great potential to produce high performance armour steel joint with high productivity.

Transient liquid phase bonding of Inconel 617 superalloy: effect of filler metal type and bonding time

Abstract: Transient liquid phase (TLP) bonding has enormous potential to repair cracks in the gas turbine hot section parts that are made of Ni-based alloys. The experiments were carried out by BNi-1 and BNi-2 filler metals in a vacuum furnace at the bonding times of 45 and 300 min. The shear strength, microhardness, microstructure, and homogeneity of chemical composition during TLP bonding of Inconel 617 superalloy, which is the base metal, were evaluated. The shear strength of about 620 MPa was obtained using the BNi-1 filler metal. Hence, the BNi-1 filler metal and the bonding time of 300 min are recommended for repair of hot section components of a gas turbine. The gap size is an important parameter on the diffusion especially at the lower bonding times but the preliminary difference in the chemical composition may play an important role at the longer bonding times. The results show that the type of filler metal is an important parameter in this process.

Effect of cold metal transfer and gas tungsten arc welding processes on the metallurgical and mechanical properties of Inconel® 625 weldings

Abstract: Inconel® 625 weld metal has lower mechanical properties than its corresponding annealed base metal due to the precipitation of brittle phases during solidification. To control the precipitation of these phases, a reduction in heat input and amount of iron and silicon in the weld metal and an increase in the cooling rate are proposed. Cold metal transfer (CMT)–gas metal arc welding (GMAW) is a process that digitally controls filler metal transfer to the weld, which reduces the heat input and dilution ratio. In this work, weldments of 2-mm-thick Alloy 625 sheets were prepared using CMT and gas tungsten arc welding (GTAW) process to compare the mechanical properties (tensile and stress-controlled fatigue life tests) of the welded joints. An increment in the tensile properties and fatigue life of CMT welds was found when compared with the GTAW welds. Microstructure characterization, grain size in the heat-affected zone, phase content in the weld metal, secondary arm spacing, and Vickers hardness measurements were performed to establish the causes of the observed differences. This result was a consequence of the lower dilution of the base metal and amount of particles in the weld metal produced by a lower heat input supplied by CMT.

Multi-Material Design in Welding Arc Additive Manufacturing

Abstract: Due to the inherent properties of the process, arc-based generative manufacturing offers the possibility, of specifically applying different material properties locally. One possibility to realize this is the use of different materials. Three approaches are presented to illustrate this option. First, anisotropic behavior in the welding direction is generated. For this purpose, a FeNi36 is specifically combined with a low-alloy ultra-high-strength fine-grained structural steel filler metal. It will be shown that the integral component properties can be specifically adjusted in the welding direction. In addition, the metallurgical and welding characteristics will be discussed. As a second possibility, the use of well plasticizable materials to locally increase the material strength under cyclic loading with locally notched components is presented. For this purpose, an austenitic FeNi36 with good plasticizability and a good yield strength ratio for the application was applied to a fillet weld of a high-strength fine-grained structural steel in the weld seam toe. It is shown that the tolerable cyclic load can be improved by 35% by this procedure. Thirdly, it is shown that the required thickness of corrosion protection layers can be reduced by 50% through a targeted production sequence in arc-based generative manufacturing.

Fatigue life enhancement of TIG-welded 304L stainless steels by shot peening

Abstract: Shot peening is a cold working process that leads to changes of residual stress in the surface layer and the microstructure. In this paper, we studied the effect of the stress ratio and shot peening on the fatigue life of AISI 304L austenitic stainless steel welded using a fully manual gas tungsten arc welding process (GTAW). The specimens are prepared by welding flat plates with thickness of 1 mm using GTAW process and the 308 stainless steel as the filler metal. Results indicate that the fatigue life of the as-welded material under tension–compression loading (stress ratio R = − 1) is longer compared to fatigue life under tension–tension loading (stress ratio R = 0). Furthermore, the microhardness and fatigue life are found to be improved after shot peening post-welding treatment for durations ranging from 5 to 7 min. The improvement in tensile stress and microhardness of treated material is as good as the results reported using the more advanced and costly techniques. Also, the findings suggest that influence of duration of shot peening is more significant on the fatigue life than on the microhardness.

Fast Isothermal Solidification During Transient Liquid Phase Bonding of a Nickel Alloy Using Pure Copper Filler Metal: Solubility vs Diffusivity

Abstract: This investigation aims at understanding the underlying fundamentals of the isothermal solidification phenomenon during the transient liquid phase (TLP) bonding process. The isothermal solidification is governed by solid-state diffusion of the melting point depressant (MPD) into the base material, which, in turn, is controlled by both kinetic and thermodynamic parameters; however, the latter factor is generally ignored. In this work, the competition between kinetics and thermodynamics of diffusion were considered in TLP bonding of a nickel alloy, Monel 400, using two distinct filler metals including pure copper (Cu) and Ni-Si-B filler metal. The joint generated by Ni-Si-B filler metal exhibited two key features including the presence of eutectic-type solidification products, an indication of incomplete isothermal solidification, and the presence of liquated grain boundaries in the substrate. However, the joint generated using pure Cu filler metal exhibited neither liquated grain boundaries nor precipitates in the diffusion-affected zone (DAZ). Interestingly, a fast isothermal solidification was observed when bonding using Cu filler metal. Despite the lower diffusivity of Cu, as a substitutional MPD in Ni-base substrate, compared to that of B, as an interstitial MPD, its higher solid solubility in the substrate provides a larger thermodynamic driving force for diffusion-induced isothermal solidification. Moreover, due to the high partitioning ratio of Cu in the Ni-base substrate and, hence, the lower difference between MPD solubility in liquid and solid phases, the required number of MPD atoms that should diffuse from the liquid phase into the base metal (BM) to complete isothermal solidification is much lower than that of B-containing filler metals. Therefore, both diffusivity and solubility of the MPD element should be considered in filler metal selection for achieving a fast isothermal solidification during TLP bonding.

Optimization of GTAW Al 3003 weld using fabricated nanocomposite filler metal

Abstract: Novel Al–3 wt.% TiO2 (fillers) nanocomposite has been successfully fabricated by accumulative roll bonding method to join Al 3003 alloy with the parameters of gas tungsten arc welding process such ...

Effect of post-bond heat treatment on microstructural evolution and mechanical properties of brazed ultrathin-walled structure

Abstract: A nickel-based superalloy Inconel 718 ultrathin-walled structure was manufactured by high-temperature brazing using Ni-Cr-Si filler metal. The microstructure in the brazed fillet was analysed, and the solidification behaviour and the formation of the eutectic island in the brazed fillet were investigated. The effects of post-bond heat treatment (PBHT) with different temperatures and durations on the microstructural evolution and mechanical properties of the brazed ultrathin-walled structure were investigated in detail. The results indicate that PBHT at a relatively high temperature significantly affects the mechanical properties of the ultrathin-walled structure, which is attributed to the formation of the precipitates at a deeper location in the base metal. In addition, the mechanical performance is enhanced by the generation of δ- and γ''-phases under relatively low temperatures (980 °C and 740 °C). On the other hand, the decrease in mechanical performance is caused by the formation of network-like precipitates and the Ni-Si-Nb phase at the grain boundary over extended ageing times. By analysing the fracture mode evolution and the propagation of cracks in the brazing fillet, the effect of PBHT on fracture morphology evolution is determined primarily by the proportion of brittle fractures and the formation of the strengthening phase in the base metal.

Comparative in Mechanical Behavior of 6061 Aluminum Alloy Welded by Pulsed GMAW with Different Filler Metals and Heat Treatments.

Abstract: Precipitation hardening aluminum alloys are used in many industries due to their excellent mechanical properties, including good weldability. During a welding process, the tensile strength of the joint is critical to appropriately exploit the original properties of the material. The welding processes are still under study, and gas metal arc welding (GMAW) in pulsed metal-transfer configuration is one of the best choices to join these alloys. In this study, the welding of 6061 aluminum alloy by pulsed GMAW was performed under two heat treatment conditions and by using two filler metals, namely: ER 4043 (AlSi5) and ER 4553 (AlMg5Cr). A solubilization heat treatment T4 was used to dissolve the precipitates of β”- phase into the aluminum matrix from the original T6 heat treatment, leading in the formation of β-phase precipitates instead, which contributes to higher mechanical resistance. As a result, the T4 heat treatment improves the quality of the weld joint and increases the tensile strength in comparison to the T6 condition. The filler metal also plays an important role, and our results indicate that the use of ER 4043 produces stronger joints than ER 4553, but only under specific processing conditions, which include a moderate heat net flux. The latter is explained because Mg, Si and Cu are reported as precursors of the production of β”- phase due to heat input from the welding process and the redistribution of both: β” and β precipitates, causes a ductile intergranular fracture near the heat affected zone of the weld joint.

Butt brazing of titanium alloys/stainless steel plates by MIG-TIG double-sided arc welding process with copper filler metal

Abstract: Butt brazing of titanium alloys with stainless steel by MIG-TIG double-sided arc welding (DSAW) process with copper filler metal has been performed. The microstructures and mechanical properties of the joint were investigated. The results show that a butt brazing joint with sound double-sided appearance was achieved. With low heat input of brazing mode and rapid cooling rate of arc welding process, the joint is free of brittle Ti-Fe intermetallic compounds (IMCs). The phase compositions in the joint are TC4/Ti2Cu + TiCu/TiCu + Ti5Si3/Cu + (Ti5Si3 + Cu + βTiCu4)/Fe5Si3 + (Cu) + FeSi/Fe(s,s)/304ss orderly from Ti6Al4V to 304ss. The average tensile strength of the butt joint reaches 278 MPa. Compared with the fusion welding joint, the tensile strength of the arc-brazing joint is significantly increased because of the elimination of Ti-Fe IMCs.

Stability analysis of the Cold Metal Transfer (CMT) brazing process for galvanized steel plates with ZnAl 4 filler metal

Abstract: In order to achieve lower CO2 emissions and lower fuel consumption, modern motor vehicle industries have been reducing automotive weight with an increasing degree in the past years by replacing steel structures with brazed and welded components of steel and lightweight metals. In this context, the combination of galvanized steel and aluminum admits considerable application potential. Joints of the two cited different types of materials can be produced by partial brazing, through the Cold Metal Transfer (CMT) process with addition of zinc-based wire alloys. However, stability analysis for this process is still not well understood. Most papers focus on metallurgical characteristics such as intermetallic phase formation and joint strength. In order to assess stability, bead on plate samples made of ZnAl4 deposits on an automotive DX56D + Z140 galvanized steel was statistically correlated to current and voltage oscillograms as well as high-speed images, after variation of the IBoost parameter from 30 to 150 A. Short-circuit and arc burning times were acquired and used to compute the Vilarinho Regularity Index for Short-Circuit Transfer (IVsc), which is based on variation coefficients. The lower the IVsc, the more stable is the metal transfer. The index was used to assess bead homogeneity. The results pointed that bead homogeneity was found only for IBoost values below 97 A. However, stability was reached for IBoost levels of 97 A (with homogeneous bead) and 150 A (without homogeneous bead). This means that to determine homogeneity, the metal transfer stability, determined through IVsc, is an indicator, but other factors such as current level and its effects over the melt pool must also be considered.

Research on reaction brazing of Ti layer-coated SiCp/Al composites using Al-based filler metal foil

Abstract: Aluminum metal matrix composites with high SiC particle content (SiCp/Al MMCs) was surface metalized with Ti layer by magnetron sputtering technology, and reaction brazing was performed on ...

Microstructure and mechanical properties of the SiC/Nb joint brazed using AgCuTi+B4C composite filler metal

Abstract: The residual stress is considered to be the driving force for the failure of ceramic/metal brazing joint. In this paper, the residual stress in a SiC/Nb joint is alleviated by using AgCuTi+B4C composite brazing filler. SEM, EDS and XRD are applied to characterised the microstructure of the joint, which is determined to be SiC/Ti3SiC2/Ag(s,s)+Cu(s,s)+TiB+TiC/TiCu+ Nb(s,s)/Nb. The effects of the B4C strengthening phase mass fraction and the brazing temperature on the microstructure and the mechanical properties of the joint are investigated. It is found that the reaction products between B4C and the brazing filler (TiB whisker and TiC particles) uniformly distribute inside the joint if the mass fraction of the B4C is not higher than 1.5 wt% and when the amount of B4C reaches 2 wt%, the reaction products begin to agglomerate. With the rising of the brazing temperature, the thickness of the Ti3SiC2 reaction layer next to the ceramic increases and when the brazing temperature reaches 910 °C, another reaction layer of Ti5Si3 can be found adjacent to the Ti3SiC2 reaction layer. The strength of the joint first increases and then decreases with the increase of both the strengthening phase and the brazing temperature. The highest shear strength of the joint reaches 98 MPa when the joint is achieved at 890 °C using AgCuTi+1.5 wt%B4C brazing filler.