Cold Metal Research Articles

Tribological Behaviour of Austenitic Stainless Steel-Clad Surface Over Low Carbon Steel Produced by Cold Metal Transfer Welding Process

Tribological Behaviour of Austenitic Stainless Steel-Clad Surface Over Low Carbon Steel Produced by Cold Metal Transfer Welding Process

Optimization of process parameters of cold metal transfer welding-based wire arc additive manufacturing of super Duplex stainless steel using response surface methodology

The parameter selection is essential to achieving the desired bead geometry and minimizing the various defects such as discontinuous weld beads, cracks, porosity, and waviness during the fabrication of wire arc additive manufacturing (WAAM) samples. The purpose of this study is to examine the effect of three input process parameters (current, welding speed, and gas flow rate) at three distinct levels on the properties (weld bead width, bead height, and dilution) of samples fabricated using super Duplex 2507 stainless steel through the cold metal transfer (CMT)–WAAM process using response surface methodology (RSM). To create a design of experiment involving three process parameters, a central composite design (CCD) matrix was utilized, and adequacy was checked by ANOVA analysis. The maximum values for weld bead width and bead height were 6.57 mm and 3.43 mm, respectively; the minimum dilution observed was 31.30%. The predicted optimal input parameters were 190.46 A current, 8.94 mm/s welding speed, and 15 l/min shielding gas flow rate. The results indicated that current was the most influential factor in determining the multiple responses, followed by welding speed and gas flow rate. The microstructures were characterized by optical microscopy, and results indicated that the microstructure of weld bead region consisted of ferrite and austenite. The microhardness of the CMT-based WAAM fabricated samples was also evaluated. This study holds significant potential for the fabrication of stainless-steel additive manufacturing products using a CMT-based arc welding process.

The influence of CMT-MAG and MAG welding-processes on microstructure and mechanical behaviour of C-Mn E410 structural-steels

PurposeAn experimental investigation for developing structure-property correlations of hot-rolled E410 steels with different carbon contents, i.e. 0.04wt.%C and 0.17wt.%C metal active gas (MAG) and cold metal transfer (CMT)-MAG weldments was undertaken.Design/methodology/approachMechanical properties and microstructure of MAG and CMT-MAG weldments of two E410 steels with varying content of carbon were compared using standardized mechanical testing procedures, and conventional microscopy.Findings0.04wt.%C steel had strained ferritic and cementite sub-structures in blocky shape and large dislocation density, while 0.17wt.%C steel consisted of pearlite and polygonal ductile ferrite. This effected yield strength (YS), and microhardness being larger in 0.04wt.%C steel, %elongation being larger in 0.17wt.%C steel. Weldments of both E410 steels obtained with CMT-MAG performed better than MAG in terms of YS, ultimate tensile strength (UTS), %elongation, and toughness. It was due to low heat input of CMT-MAG that resulted in refinement of weld metal, and subzones of heat affected zone (HAZ).Originality/valueA substantial improvement in YS (∼9%), %elongation (∼38%), and room temperature impact toughness (∼29%) of 0.04wt.%C E410 steel is achieved with CMT-MAG over MAG welding. Almost ∼10, ∼12.5, and ∼16% increment in YS, %elongation, and toughness of 0.17wt.%C E410 steel is observed with CMT-MAG. Relatively low heat input of CMT-MAG leads to development of fine Widmanstätten and acicular ferrite in weld metal and microstructural refinement in HAZ subzones with nearly similar characteristics of base metal.

A comparative study on Al-Mg-Sc-Zr alloy fabricated by wire arc additive manufacturing with controlling interlayer temperature and continuous printing: Porosity, microstructure, and mechanical properties

Wire arc additive manufacturing (WAAM) technique is a promising approach to producing large-scale metal components due to high deposition efficiency and low production cost. However, fundamental research about WAAM-processed Al-Mg-Sc-Zr alloy was still fewer. In this study, Al-6.54Mg-0.36Sc-0.11Zr (wt%) components were successfully manufactured by WAAM with an interlayer temperature at 100 °C (named IW) and continuous printing (named CP), and the corresponding porosity, microstructure, and mechanical properties of components were studied in detail. The porosity of components as-deposited was relatively low, about 0.385% and 0.116%, respectively. The microstructures of the two components exhibited the same distribution characteristics in XZ and YZ planes: fine equiaxed grains (FEG) at remelted zone + FEG and coarse equiaxed grain (CEG) alternative distribution at middle zone + FEG at the top zone of the molten pool. The average grain size of component IW was about 10.51 ± 6.01 μm, and that of component CP significantly increased, to about 11.85 ± 5.86 μm. The short-circuit transition mode of cold metal transfer technology and the heterogeneous nucleation effect of primary Al3(Sc, Zr) and Al3(Sc, Zr, Ti) phases together promoted the formation of equiaxed grains and refined the microstructures. After heat treatment at 325 °C and 6 h, nano-Al3Sc precipitated with a size of about 15–50 nm. The yield strength (YS) of components IW and CP increased from 171 ± 3 to 261 ± 1 MPa and 168 ± 7 to 240 ± 17 MPa, respectively. Component IW had the highest ultimate tensile strength, about 400 ± 1 MPa. For WAAM-processed Al-Mg-Sc-Zr alloys, the contribution of the strengthening mechanism to YS was solid solution strengthening > precipitation strengthening > fine grain strengthening > dislocation strengthening.

Effect of energy input on fatigue crack growth behavior of titanium alloy Ti6Al4V made by WAAM‐CMT

AbstractThis work deals with the investigation and characterization of Ti6Al4V parts produced with an intriguing manufacturing process belonging to the Wire Arc Additive Manufacturing (WAAM) family: the Cold Metal Transfer technology (CMT). Wall‐shaped parts were produced according to different process parameters, namely the wire feed speed and voltage–current combinations, leading to different energy inputs. The parts were characterized in terms of surface morphology, microhardness, microstructure, tensile properties, and fatigue crack growth. The results suggested that the investigated deposition parameters led to similar results. Moreover, the mechanical and fatigue crack growth behavior was in line with parts of the same alloy produced through other manufacturing routes, whereas the microstructure type was the result of the fast cooling of the molten material. Finally, considering the simple system adopted to avoid oxidation during the deposition stage, the results suggested that CMT is a promising manufacturing technique for titanium alloy semifinished parts.

Metallurgical characteristics of AA6061 aluminium and AZ31B magnesium dissimilar joints by fusion welding technique.

Aluminium (Al) and magnesium (Mg) alloys are extensively used in the automobile sector because of their high strength-to-weight ratio, excellent castability low density and simplicity of recycling. Al-Mg structures used in the automotive sector can potentially reduce their weight. Although there is a significant opportunity for substantial cost reduction, the use of magnesium in aluminium structures remains restricted. This study aims to weld 3 mm-thick rolled sheets of AA6061 Al and AZ31B Mg alloy using the cold metal transfer (CMT) arc welding process. Three different filler wires (ER1100, ER4043, and ER5356) were used in the experiment. In this article, the mechanical and microstructure characteristics of Al/Mg dissimilar joints manufactured by CMT are evaluated and discussed in detail. Optical microscope (OM), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), and x-ray diffraction (XRD) were used to analyze the CMT-welded Al/Mg dissimilar joints. Of the three filler wires used, ER4043 (Al-5%Si) filler wire yielded defect-free sound joints due to the presence of Si, which improves the flow ability of molten filler during welding. The presence of Mg-rich intermetallics-Al12Mg17)and Al-rich intermetallics-Al3Mg2 were observed. The fractured area of the CMT-welded Al/Mg dissimilar joints revealed the presence of the Mg-rich intermetallics (Al12Mg17), which is responsible for the decrease in tensile strength. The reduction of intermetallics, particularly of Mg-rich intermetallics (Al12Mg17) is important for improving joint strength. RESEARCH HIGHLIGHTS: Cold metal transfer (CMT) arc welding was used to control the Al-Mg-rich intermetallics in the Al/Mg dissimilar joints. The microstructure, morphology and phase composition of the welded joints were studied by OM, SEM, TEM, EDS and XRD. The weld metal and AL substrate bonded with a strong interface, while weld metal and Mg substrate were joined at the epitaxial solidification area where the intermetallic compounds of Mg2Al3, Mg17Al12 and Mg2Si are generated. The weld metal on the Mg side experienced brittle fracture, with a continuous distribution of Mg2Al3, Mg17Al12 and Mg2Si.

Effect of welding mode on selected properties of additively manufactured AA5087 aluminium alloy parts

Wire and arc additive manufacturing (WAAM) is a popular direct energy deposition (DED) method for producing large-scale metallic components. The main advantages of the technique are a high deposition rate and low cost. Furthermore, the utilization of the WAAM is prevalent in the aerospace industry. The AA5087 aluminium alloy with 4.5 wt.% of magnesium has been investigated because of its excellent properties. The present research deals with the study of thermal cycles and fields developed in the alloy during additive manufacturing with two different Cold metal transfer (CMT) modes, namely conventional (CMT) and cycle-step (CMT-CS). The welding system was equipped with a Fronius TransPulse Synergic 3200 CMT power source, a Fanuc Arc Mate 1000iC 6-axes robot with an R 30iA control unit, a welding torch, and a 1-axis positioner. The AA5087 aluminium alloy welding wire with a diameter of 1.2 mm was deposited onto the AA5083 aluminium alloy plate with dimensions of 70 mm x 200 mm x 3 mm during the experiment. The thermal cycles were documented using an Ahlborn Almemo 5690-2 measuring station equipped with K-type thermocouples. The thermal fields were monitored with a FLIR E95 thermography camera. The results showed the evident influence of arc mode on the temperatures developed in manufactured aluminium alloy parts during the process of WAAM.

A comparative study of interface characteristics and properties of bronze coatings on steel by plasma arc and cold metal transition deposition

A comparative study of interface characteristics and properties of bronze coatings on steel by plasma arc and cold metal transition deposition

Numerical Study of the Cold Metal Transfer (CMT) Welding of Thin Austenitic Steel Plates with an Equivalent Heat Source Approach

The CMT (cold metal transfer) arc welding process is a valuable joining method for assembling thin sheets, minimizing heat transfers, and reducing subsequent deformations. The study aims to simulate the CMT welding of thin stainless-steel sheets to predict temperature fields and deformations. Both instrumented tests and numerical simulations were conducted for butt-welding of sheets with a thickness of 1 to 1.2 mm. Weld seam samples were observed to identify equivalent heat sources for each configuration. The electric current and voltage were monitored. Temperature measurements were performed using K-type thermocouples, as well as displacement measurements via the DIC (digital image correlation) technique. Thermomechanical simulations, considering phase changes and the actual seam geometry induced by filler material, were conducted using an equivalent heat source approach. A unique heat exchange coefficient accounting for thermal losses was identified. By incorporating these losses into thermal calculations, a good agreement was found between measured and calculated temperatures. Mechanical calculations allowed for the recovery of the horse saddle form after actual welding, with a relative difference of less than 10% in angular distortion between calculated and measured values.

An overview of cold metal transfer welding of similar materials

An overview of cold metal transfer welding of similar materials

Retracted: Complex Behavior of Droplet Transfer and Spreading in Cold Metal Transfer

Retracted: Complex Behavior of Droplet Transfer and Spreading in Cold Metal Transfer

Modulation of characteristic zones in NiTi alloys fabricated via wire arc additive manufacturing

The application of additive manufacturing (AM) is gradually extending to different industrial sectors. Most additively manufactured metallic components typically exhibit an inherent columnar grain structure, the control of which has been a challenging issue. In this study, the microstructures of the characteristic zones (heat-affected zone and transition zone) were controlled by adjusting the deposition strategy and arc mode during wire arc additive manufacturing (WAAM) of NiTi alloy. Compared to the sample fabricated by cold metal transfer (CMT) mode, the oscillating (O) sample shows a higher tensile strength of 793.6 MPa, while the pulsed (P) sample shows a better elongation of 5.8%. The high strength of the O samples is mainly due to the significantly lower aspect ratio of its columnar grains, while fine equiaxed grain structure in the transition zone of the P samples is responsible for the better plasticity. Different microstructures in the characteristic zones can be tailored by combining the forced melt flow, pulse frequency and undercooling, which provides vast freedom for the associated mechanical properties control. Our work provides a new strategy to regulate the microstructure and thus mechanical properties of additively manufactured NiTi alloys.

Effect of heat input on the hazardous gas emissions from galvanized steel during cold metal transfer welding

The impact of heat input on the hazardous gas emissions of cold metal transfer welded zinc-coated steel joints is the main focus of this study. The bulk formation of fumes during the arc-assisted metal joining process not only affects the characteristics of joints but also, affects the welder’s respiratory systems and environment. Hence, in this research work, using a stack-monitoring kit the welding fumes are collected for various heat inputs and characterized to understand the hazardous emission from zinc-coated steel by the Cold Metal Transfer - 400TPSi advanced technique. The experimental work conducted for the heat input of 0.624 kJ/mm showed superior results for fume formation rate, dust emission rate and emission factor when compared to other heat inputs. In addition, the dust emission rate and fume formation rate increased as the heat input increased. Also, Hazardous gas emissions of CO2, SO2, CO, Zinc and the concentration of total dust for the corresponding heat input were found to be within permissible limits. Furthermore, the TEM analysis exhibits that, the particle structure of the fume is agglomerated chains of spherical and faceted morphology. The outcomes prove outstanding results when compared to other welding processes and norms of the NIOSH and ISI 5182 standards.

High-temperature compression deformation strengthening mechanism of Mg–Gd–Y–Zn–Zr alloy formed by cold metal transfer (CMT) arc additive forming

The Mg–Gd–Y–Zn–Zr alloy structural parts were formed by CMT arc additive forming. The high-temperature compression deformation strengthening mechanism of the alloy at 623–723 K, 0.01–1s−1, and 50 % deformation was studied. Upon a decrease in the temperature or an increase in the strain rate, the effect of fine-grain strengthening was obvious, which led to the improvement of the mechanical properties of the alloy after deformation. The grain refinement was mainly attributed to the DDRX and CDRX processes during hot deformation. Because the compression specimen was loaded along the building direction, the twins after deformation were compression twins {10–11}, and the content increased with an increase in the strain rate or a decrease in the temperature. As the strain rate increased, the texture distribution on the {10-10} plane became more concentrated and the texture intensity decreased from 6.79 to 2.24. This was attributed to the fact that the alloy was mainly dominated by a non-basal slip during high-temperature deformation, which increased the sensitivity of the strain rate to the texture.

Numerical simulation of thermal processes in cold metal transfer-based additive manufacturing

Numerical simulation of thermal processes in cold metal transfer-based additive manufacturing

Investigation of Surface Residual Stress, Mechanical Properties, and Metallurgical Characterization of Inconel 625 Multilayer Thin-Wall Component Using Cold Metal Transfer Technique

Investigation of Surface Residual Stress, Mechanical Properties, and Metallurgical Characterization of Inconel 625 Multilayer Thin-Wall Component Using Cold Metal Transfer Technique

Multi-Objective Optimization for Forming Quality of Laser and CMT-P Arc Hybrid Additive Manufacturing Aluminum Alloy Using Response Surface Methodology

A thin-walled structure of high-strength aluminum alloy 2024 (AA2024) was fabricated using novel laser and cold metal transfer and pulse (CMT-P) arc hybrid additive manufacturing (LCAHAM) technology. The influence of the wire feeding speed, scanning speed, and laser power on the forming quality was systematically studied by the response surface methodology, probability statistical theory, and multi-objective optimization algorithm. The result showed that the forming accuracy was significantly more affected by the laser power than by the wire feeding speed and scanning speed. Specifically, there was an obvious correlation between the interaction of the laser power and wire feeding speed and the resulting formation accuracy of LCAHAM AA2024. Moreover, the laser power, wire feeding speed, and scanning speed all had noticeable effects on the spattering degree during the LCAHAM AA2024 process, with the influence of the laser power surpassing that of the other two factors. Importantly, these three factors demonstrated minimal mutual interaction on spattering. Furthermore, the scanning speed emerged as the most significant factor influencing porosity compared to the wire feeding speed and laser power. It was crucial to highlight that the combined effects of the wire feed speed and laser power played an obvious role in reducing porosity. Considering the forming accuracy, spattering degree, and porosity collectively, the recommended process parameters were as follows: a wire feeding speed ranging from 4.2 to 4.3 m/min, a scanning speed between 15 and 17 mm/s, and a laser power set at approximately 2000 W, where the forming accuracy was 84–85%, the spattering degree fell within 1.0–1.2%, and the porosity was 0.7–0.9%.

Feasibility study of wire arc additive manufactured P91 steel by cold metal transfer deposition

The objective of this study was to analyze and evaluate the feasibility of utilizing Wire Arc Additive Manufacturing (WAAM) technology for the constructing components made from P91 steel, which is widely used material for high-temperature applications. The utilization of the Cold Metal Transfer (CMT) method enables the deposition of thin steel walls by virtue of its low heat input. Samples collected from the deposited wall have been tested in two different microstructural conditions, in the as-built (AB) condition and in a normalized and tempered (NT) condition. The latter condition is the microstructural state commonly employed for producing components used in power plants. This post-deposition heat treatments (PDHT) comprise a normalization process conducted at 1050 °C for 40 min, followed by a tempering step at 760 °C for 2 h. The results of mechanical testing and microstructural characterization were then compared against the established standards for commercial P91 steel. SEM-EDAX, XRD, and EBSD analyses were employed to conduct a comprehensive microstructural examination of the samples. The hardness of the AB samples ranged from 384 to 439 HV, while the NT samples had a hardness range of 205 to 223 HV. In terms of tensile strength, the AB samples demonstrated a range of 1064 to 1266 MPa, whereas the NT samples exhibited a range of 635 to 626 MPa. These results were found to be consistent with the observed strong texture and grain orientations in the {001} and {111} planes, as revealed by the EBSD analysis. The NT components demonstrated significant strength, ductility, hardness, and toughness compared to the specified ASTM standards. Based on the test performance and feasibility criteria, this process has significant potential as an additive manufacturing method suitable for complex boiler components.

Enhancing the Microstructure and Mechanical Properties of Cast Aluminum Matrix Composites Through Nano-Al2O3 Reinforcement via CMT and PMC Welding

In this investigation, two distinct composites were produced using the liquid metallurgy vortex-route method with an aluminum AA6013 matrix and 0.5% and 1% nano-Al2O3 reinforcement by weight. The effects of nano-Al2O3 ceramic particles added into the AA6013 alloy to increase the hardness and strength of the composite were investigated. Samples for welding were prepared from cast composite materials with dimensions of 250 × 110 × 60 mm. The obtained specimens were joined via butt welding at 110-A and 120-A current intensities, and at a constant speed of 400 mm/min by cold metal transfer (CMT) and pulse multi-control (PMC) welding methods. Using the use of micro- and macrostructural evaluations, hardness measurements, and tensile testing, the impacts of each welding parameter on the mechanical characteristics and weld structure of the cast composites were examined. The composite material with 0.5% nano-Al2O3 reinforcement that was joined at 120 A utilizing the CMT process achieved the highest tensile strength value at 96.6 MPa. At 110-A and 120-A welding current values, 0.5% reinforced composite demonstrated the maximum strength in both welding techniques.

Microstructures and mechanical properties of nano-TiC/Ti-refined Al[sbnd]Mg alloys prepared by wire arc additive manufacturing

In the current study, an AlMg alloy refined with a nano-TiC/Ti grain refiner was successfully printed by cold metal transition wire arc additive manufacturing (CMT-WAAM). The effects of the nano-TiC/Ti grain refiner on the microstructure and mechanical properties of the CMT-WAAM-prepared AlMg alloy were studied. The results indicated that the nano-TiC/Ti grain refiner has a significant refining effect on AlMg alloy and refined the coarse columnar crystals into uniform fine equiaxed crystals. The average grain size of the CMT-WAAM AlMg alloy refined with the 0.6 wt% nano-TiC/Ti grain refiner decreased from 53.06 μm to 25.32 μm (yz plane), and the average grain size in the xy plane decreased from 52.00 μm to 25.80 μm. The excellent grain refinement effect of the nano-TiC/Ti grain refiner was attributed to the presence of TiC particles at the grain, which acted as heterogeneous nucleation sites and improved the nucleation rate. Moreover, TiC particles located at the grain boundary inhibited the growth of the grain boundary. The mechanical properties, i.e., the tensile and yield strength, were improved by 20–25%, and there was an increase in the microhardness (~9.5%) of the CMT-WAAM AlMg alloy refined with the 0.6 wt% nano-TiC/Ti grain refiner.