Showing papers on "Filler metal published in 2018"

Wire and arc additive manufacturing: a comparison between CMT and TopTIG processes applied to stainless steel

Abstract: Wire and arc additive manufacturing (WAAM) enables the building of near net-shape components layer by layer by using arc welding technologies and wire filler metal as feedstock. The study aims at comparing the applicability of two innovative robotic arc welding technologies (cold metal transfer (CMT) and TopTIG) for additive manufacturing (AM) of stainless steel parts. Initially, a process development has been completed with the goal of optimizing material deposition rate during arc time. Both continuous and pulsed current programs were implemented. Then, different thick-walled samples composed of more than one overlapped weld bead per layer were manufactured in 316L stainless steel grade by CMT and TopTIG. Mechanical properties have been determined in as-build samples in different building orientations. WAAM applying CMT and TopTIG welding technologies is analyzed in terms of part quality (defined as the absence of defects such as pores, cracks, and/or lack of fusion defects); surface finishing; part accuracy; productivity; microstructural characteristics; and mechanical properties. Achieved mechanical properties and deposition rates are compared with the state of the art. Findings and conclusions of this work are applicable to the industrial manufacturing of stainless steel parts and requirements to apply these technologies to other expensive materials are finally discussed.

Hot wire-assisted gas metal arc welding of hypereutectic FeCrC hardfacing alloys: Microstructure and wear properties

Abstract: The deposition welding of hypereutectic FeCrC hardfacing alloys requires low dilution rates in order to ensure the specified chemical composition and thus the precipitation of primary M7C3 (M = Fe, Cr) carbides, which affect the abrasive wear resistance of the hardfacing. Because dilution is critical in determining the above mentioned criteria during surfacing, the development of deposition welding processes with reduced thermal impact and hence reduced dilution of the base material is a main focus of current research. For the purpose of improving the processing properties of gas metal arc welding (GMAW) in hardfacing applications, the potential of an additional hot wire (HW-GMAW) was investigated. The application of a hot wire enabled the independent adjustment of the deposition and dilution rates. Furthermore, the dilution and microstructural properties could be adjusted independently of the deposition rate. HW-GMAW enabled hypereutectic solidification in the first layer, even at very high deposition rates of 9 kg/h. In this manner, a primary M7C3 carbide content reaching 17% by area (A%) was achieved in the first layer. In comparison to single-layer GMAW overlays the wear properties were improved.

Aluminium to steel resistance spot welding with cold sprayed interlayer

Abstract: Studies on bonding of aluminium alloys to steels are popular because these are structural materials widely used in a variety of industries. However, joining these dissimilar materials is difficult mainly because of the formation of brittle intermetallic compounds. This paper presents a study on welding aluminium to steel by resistance spot welding. Before the welding, steel surface was covered by cold spraying with the layer of aluminium, nickel and nickel–aluminium. This way, instead of the welding of dissimilar materials, the welding of aluminium to aluminium (or nickel) layer pre-deposited on the steel sample was performed. The feasibility of using interlayers for improving the welding of dissimilar materials was tested using SEM, EDX and XRD. Mechanical properties of welds were investigated by microhardness and shear strength tests. The results showed that the coating allowed to decrease hardness in the welding zone and to increase the shear strength of the weld.

Mechanical properties of Inconel 718 welds performed by gas tungsten arc welding

Abstract: Gas tungsten arc welding (GTAW) was used to join plates of Inconel 718. The mechanical properties were determined by tensile, microhardness, and instrumented Charpy impact tests. An ERNiFeCr-2 filler metal fed by a semi-automatic mechanism was used. Partial dissolution of the strengthening phases, γ′ and γ″, induced a soft region (~ 225 HV1.0) in the heat-affected zone (HAZ) during welding. The yield strength (371.3 MPa) of the as-welded joint is approximately 45% of the base material in aged condition (822.7 MPa). The welds were subjected to a hardening recovery post weld heat treatment (HRPWHT). Impact testing of the hardened welds revealed a reduction of 17% in energy absorbed with respect the aged base material. Hardness measurements showed an increase to ~ 410 HV0.1 in the fusion zone; however, due to segregation of Nb and formation of carbides, the precipitation of γ″ is not fully completed, and the yield strength (719 MPa) of the heat-treated welded joint is lower than the base material in aged condition.

Microstructural evolution mechanism during brazing of Hastelloy X superalloy using Ni–Si–B filler metal

Abstract: The paper aims at understanding solidification phenomena and solid state precipitations during diffusion brazing of Hastelloy X nickel base superalloy using a ternary Ni–4.5Si–3.2 B (in wt-%) fille...

Dissimilar Joining of Stainless Steel and 5083 Aluminum Alloy Sheets by Gas Tungsten Arc Welding-Brazing Process

Abstract: The dissimilar joining using gas tungsten arc welding - brazing of 304 stainless steel to 5083 Al alloy had been conducted with the addition of Al-Cu eutectic filler metal. The interface microstructure formation between filler metal and substrates, and spreading of the filler metal were studied. The interface microstructure between filler metal and aluminum alloy characterized that the formation of pores and elongated grains with the initiation of micro cracks. The spreading of the liquid braze filler on stainless steel side packed the edges and appeared as convex shape, whereas a concave shape has been formed on aluminum side. The major compounds formed at the fusion zone interface were determined by using X-ray diffraction techniques and energy-dispersive X-ray spectroscopy analysis. The micro hardness at the weld interfaces found to be higher than the substrates owing to the presence of Fe2Al5 and CuAl2 intermetallic compounds. The maximum tensile strength of the weld joints was about 95 MPa, and the tensile fracture occurred at heat affected zone on weak material of the aluminum side and/or at stainless steel/weld seam interface along intermetallic layer. The interface formation and its effect on mechanical properties of the welds during gas tungsten arc welding-brazing has been discussed.

Welding of S960MC with undermatching filler material

Abstract: High strength structural steels are in high demand thanks to their favorable mechanical properties. They offer high strength with sufficient toughness and good forming capabilities. Applications range from shipbuilding, to offshore constructions, cranes, and pipelines. A lot of current research focuses on weldability of high strength low alloy (HSLA) steels, especially improving the toughness in the weld zone, i.e., weld metal (WM) and heat affected zone (HAZ). In the present work, four different fusion welding processes using undermatching filler metal are compared on 8-mm thick sheets of S960MC structural steel. The welding processes include electron beam, laser hybrid, plasma, and gas metal arc welding. The welded joints are characterized by means of mechanical testing, tensile, impact, and hardness testing, and microstructural investigaton, light optical, and scanning electron microscopy. Furthermore, microprobe analysis of the weld metal was used to investigate the chemical composition of the weld metal.

Determination of residual stresses in fibre laser welded AA2024-T3 T-joints by numerical simulation and neutron diffraction

Abstract: This paper presents an experimental and numerical study of residual stress states and deformation in fillet welded AA2024-T3 T-joints produced using a high-power fibre laser. Welded sheets with one and three stiffeners were prepared, respectively, to determine changes in microstructure, residual stress, distortion and micro-hardness. 3D sequentially coupled thermo-mechanical finite element models were developed to analyse welding temperature fields, and accurately simulate welding residual stresses and deformation. The simulated results were calibrated using the experimental database on weld pool geometry obtained from optical metallography and temperature fields measured using thermocouples. Residual stress measurements were made using neutron diffraction techniques and sheet distortions were measured using a coordinate measuring machine. The influence of various mechanical boundary conditions on angular and cambering sheet distortions was examined to optimise the restraint parameters. The application of element death and rebirth and dummy element techniques were studied and compared to incorporate the effect of filler metal deposition during welding. The level of residual microstrain was evaluated by diffraction peak width analysis, which indicated the maximal values in the weld metal. The effect of grain growth with respect to strength was of minor importance, whereas, considerable softening in the weld metal was observed.

Microstructure and properties of a dissimilar weld between alloy 617 and A387 steel using different filler metals

Abstract: In this study, microstructural and mechanical properties of a (butt) weld, joining two base metal alloys 617 and A387-Gr.11 steel, were investigated. Fusion welding was performed using gas tungsten arc welding. Three different filler metals of ERNiCrMoCo-1, ERNiCr-3, and ER309L were used to perform welding. Microstructural analysis was conducted with optical and scanning electron microscopes. Microstructural observations revealed that the extent of carbon migration and martensite phase formation in the transition zone is reduced by using filler metals of higher Ni content. For the ERNiCrMoCo-1 filler metal, unmixed zone in alloy 617 base metal side was eliminated. Microhardness, impact, and tensile tests were carried out to determine the mechanical properties of the dissimilar metal welds (DMWs). The welds made by using ERNiCrMoCo-1 filler metal resulted in highest hardness and impact energy, whereas ERNiCr-3 filler metal weld displayed the highest tensile strength, yield strength, and elongation in comparison with other fillers. Based on the results, the ERNiCrMoCo-1 filler metal was found to be the best filler metal choice for the DMWs of these two base metals.

Resistance spot welding of metal/carbon-fibre-reinforced plastics and applying silane coupling treatment

Abstract: Dissimilar materials joining of SUS304 and carbon-fibre-reinforced plastics consisting of short fibres and thermoplastics was performed. The materials were joined by series resistance spot welding. The electrodes were pressed on the metal plate of the lap joint of metal/carbon-fibre-reinforced plastics. The SUS304 plate was heated by resistance heating, causing the thermoplastic near the interface to melt slightly because of heat conduction. SUS304 could be joined directly to carbon-fibre-reinforced polyamide and modified polypropylene, but not to polyphenylene sulphide. The joining area increased with an increase in the welding current and welding time, so did the tensile shear fracture load. Furthermore, the silane coupling agent treatment of SUS304 was highly effective in increasing the joining strength.

Wetting behaviour of Zn–Al filler metal on a stainless steel substrate

Abstract: This work offers an analysis of the wetting behaviour of the Zn–xAl filler metal spreading on the stainless steel. Effects of Al content on wetting kinetics and microstructures of the re-solidified filler metal were studied in this important system of dissimilar substrates. Experimental results have confirmed that the wetting of Zn–xAl filler metal on stainless steel features the trend of triple-line kinetics. In the main spreading phase, the spreading radius and time can be correlated with a power law of Rn ∼ t, n = ∼0.4. The content of Al in the filler metal has a minimal effect on the value of n for the investigated range of Al concentrations. However, the spreading area of the filler metal after re-solidification decreases with an increase of the content of Al. Moreover, the thickness of the Fe–Al intermetallic layer at the cross-section increases with an increasing Al content.

Evaluating the Properties of Dissimilar Metal Welding Between Inconel 625 and 316L Stainless Steel by Applying Different Welding Methods and Consumables

Abstract: The current work was carried out to characterize welding of Inconel 625 superalloy and 316L stainless steel In the present study, shielded metal arc welding (SMAW) and gas tungsten arc welding (GTAW) with two types of filler metals (ERNiCrMo-3 and ERSS316L) and an electrode (ENiCrMo-3) were utilized This paper describes the selection of the proper welding method and welding consumables in dissimilar metal joining During solidification of ERNiCrMo-3 filler metal, Nb and Mo leave dendritic cores and are rejected to inter-dendritic regions However, ERSS316L filler metal has small amounts of elements with a high tendency for segregation So, occurrence of constitutional super-cooling for changing the solidification mode from cellular to dendritic or equiaxed is less probable Using GTAW with lower heat input results in higher cooling rate and finer microstructure and less Nb segregation The interface between weld metal and base metal and also unmixed zones was evaluated by scanning electron microscopy and energy dispersive X-ray (EDX) analysis Microhardness measurements, tensile test, and Charpy impact test were performed to see the effect of these parameters on mechanical properties of the joints

Investigations on microstructure and mechanical properties of TiO2 Nanoparticles addition in Al 3003 alloy joints by gas tungsten arc welding

Abstract: Al 3003 alloy is well known for its industrial use as heat exchangers, radiators, oil tanks and household utensils. In case of heat exchangers, fabrication becomes mandatory by a welding process which is carried out by gas tungsten arc welding (GTAW). It is preferred due to its advantages of superior mechanical properties. Thus by involving GTAW process and reinforcing with suitable nanoparticles, the strength of Al 3003 alloy can be improved at the joints. Hence this technical paper deals with the fabrication of Al100–x – x wt% TiO2 (x = 0, 0.75, 1.5, 2.25 and 3) nanocomposite filler metal through accumulative roll bonding (ARB) technique to weld Al 3003 alloy through GTAW. Further characterization studies have been made through various electron microscopic techniques besides X‐ray diffraction analysis (XRD), vicker's microhardness and tensile testing. It was observed that the incorporation of TiO2 nanoparticles reduced the grain size much due to the formation of more nucleation sites and deceleration growth. XRD results revealed the presence of TiO2 peaks in the composite. FESEM confirmed the distribution of second phase nanoparticles regularly in the Al matrix. TEM analysis showed that the nanoscale TiO2 distribution and strain fields due to thermal mismatch between matrix and reinforcement. The improvement in mechanical properties was owing to good interfacial bonding between the Al matrix and ceramic nanoparticles.