Cold Metal Transfer Research Articles

Cold metal transfer welding of 316L/430 dissimilar stainless-steel welds

Purpose This paper aims to examine dissimilar joints for various applications in chemical, petrochemical, oil, gas, shipbuilding, defense, rail and nuclear industry. Design/methodology/approach This study examined the effects of cold metal transfer welding on stainless steel welds for 316L austenitic and 430 ferritic dissimilar welds with ER316L, ER309L and without (autogenous) fillers. The microstructural observation was done with an optical microscope. The mechanical test was done to reveal the strength, hardness and toughness of the joint. The electrochemical polarization tests were done to reveal intergranular and pitting corrosion in the dissimilar joints. Findings This microstructural study shows the presence of austenitic and ferritic phases with vermicular ferrite for ER309L filler weld, and for ER316L filler weld specimen shows predominately martensitic phase in the weld region, whereas the autogenous weld shows lathy ferrite mixed with martensitic phase. Mechanical test results indicated that filler welded specimen (ER316L and ER309L) has relatively higher strength and hardness than the autogenous weld, whereas ER316L filler weld exhibited the highest impact toughness than ER309L filler weld and lowest in autogenous weld. The electrochemical corrosion results displayed the highest degree of sensitization (DOS) in without filler welded specimen (45.62%) and lower in case of filler welded specimen ER309L (4.95%) and least in case of ER316L filler welded specimen (3.51%). The high DOS in non-filler welded specimen is correlated with the chromium carbide formation. The non-filler welded specimen shows the highest pitting corrosion attack as compared to the ER316L filler weld specimen and relatively better in ER309L filler welded specimen. The highest pitting corrosion resistance is related with the high chromium content in ER309L composition. Originality/value This experimental study is original and conducted with 316L and 430 stainless steel with ER316L, ER309 and without fillers, which will help the oil, shipbuilding and chemical industries.

Establishing Interconnections and Predictive Modelling for CMT Cladding on 316L Stainless Steel

Background Austenitic stainless-steel cladding is vital for corrosion resistance in industries such as petrochemicals, marine, and nuclear. Weld bead geometry and dilution, governed by process parameters, impact cladding quality. This study examines weld bead geometry with welding current, speed, and nozzle-to-plate distance, creating equations to predict dimensions and control geometry. Method This research explores Cold Metal Transfer (CMT) cladding, emphasizing its interaction with parameters using ANOVA and orthogonal arrays. It uncovers patterns and correlations, leading to a robust mathematical model derived from a Definitive Screen Design in Surface Methodology. Results Process parameter changes particularly affect internal shape (bead width, dilution, penetration area) compared to external shape (penetration, reinforcement) using mathematical model. And the validity of the model is defined. Penetration is primarily affected by welding current and nozzle-to-plate distance, with higher current and smaller distances leading to deeper penetration. Reinforcement is minimally impacted by welding current, speed, and error but decreases with a larger nozzle-to-plate distance. Bead width increases with higher welding current and larger nozzle-to-plate distances, while the effects of welding speed and error are relatively small. Dilution is reduced by higher welding current and larger distances, but error can significantly increase dilution. Welding speed has minimal impact on dilution. Conclusion This study enhances the understanding of CMT cladding. By analyzing parameter interactions, it predicts and controls weld dimensions. Statistical tools reveal patterns, aiding in a strong mathematical model. Significant for industrial applications, it emphasizes the impact of parameters on the quality and structure of cladding using austenitic stainless steel.

STRENGTH AND DUCTILITY CHARACTERISTICS OF METAL ALLOYS AND STAINLESS STEELS CREATED BY WIRE-ARC SURFACING IN A WIDE RANGE OF STRAIN RATES

To select rational parameters of the process of hybrid additive manufacturing of structures made of structural metal alloys and stainless steels, mechanical characteristics capable of serving as indicators of material quality were determined. The most advanced technologies of additive manufacturing by wire-arc surfacing (plasma, plasma arc with a melting electrode, including cold metal transfer) with layer-by-layer forging with a pneumatic impact tool and subsequent heat treatment were used. Aluminum-magnesium alloy AlMg5, titanium alloy Ti-6Al-4V, austenitic stainless steels 12Cr18Ni10Ti (AISI 321) and AISI 308LSi have been studied. Samples were cut from the blanks created by additive manufacturing – blades for standard tests for static uniaxial tension and cylinders for high-speed compression tests by the Kolsky method on a Hopkinson split bar. According to the registered and processed stress–strain curves for all materials, standard strength and ductility characteristics and the Johnson – Cook law of deformation and speed hardening were determined. For a correct assessment of the mechanical properties of additively produced materials, these tests were also carried out for each of them in the form of annealed rolled products. It is established that to compare the efficiency of various technological parameters of additive manufacturing, it is advisable to use static tensile strength and uniform elongation to rupture, having the smallest statistical variation. It was also found acceptable to approximate the Johnson – Cook law of the deformation curves of each of the studied materials according to averaged data, including various technological modes. Certain mechanical characteristics seem to be necessary for the search for effective modes of hybrid additive manufacturing and numerical calculation of various elastic-plastic problems in a dynamic formulation for the studied materials for design and technological needs.

Corrosion and stress corrosion cracking characteristics of 4043 aluminium alloy fabricated through directed energy deposition process

Additive manufacturing (AM) has emerged as a crucial element of Industry 4.0. In the pursuit of fabricating lightweight components, AM of aluminium alloys has become the centre of focus in recent years. This study investigates aluminium alloy (ER4043) components fabricated by arc-based directed energy deposition (DED-arc) for their corrosion and stress corrosion cracking (SCC) behaviour in 0.6 M NaCl solution at room temperature. Electrochemical characteristics in 0.6 M NaCl solution were investigated using open circuit potential (OCP), potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) tests. Electrochemical results revealed that the DED samples fabricated using a tungsten inert gas (TIG) welder as the energy source demonstrated better resistance against corrosion when compared to those developed through cold metal transfer (CMT) based DED. The prolonged exposure of samples in 0.6 M NaCl facilitated the growth of a stable passive oxide film leading to enhanced corrosion resistance. Slow strain rate tests (SSRT) conducted in air and 0.6 M NaCl solution showed that DED samples are susceptible to SCC. The fractography of the fractured SSRT samples indicated the mode of failure to be intergranular.

Improvement of microstructure and mechanical properties of CMT wire arc additive manufacturing Al-Si alloy deposition via interlayer coating TiC nanoparticles

Although cold metal transfer (CMT) wire arc additive manufacturing (WAAM) technology is commonly used in depositing aluminum alloy components, it encounters challenges and areas for improvement, particularly in Al-Si alloys. This study applies layer-by-layer TiC nanoparticle coating in the CMT-WAAM of ER4043 Al-Si alloy, investigating the impact of TiC nanoparticles on forming quality, electrical arc behavior, grain size, and mechanical properties. Results indicate that TiC nanoparticles enhance forming quality by influencing electrical arc behavior and altering the molten pool’s surface tension. Owing to the minor lattice mismatch between TiC nanoparticles and the Al matrix, these nanoparticles serve as non-uniform nucleation sites, encouraging the formation of fine grains. The grain size in CMT-WAAM specimens coated with TiC nanoparticles layer-by-layer decreased from 118.24 µm to 96.13 µm, a refinement of 18.67 %. Specimen hardness increased from 52.58 HV to 64.79 HV, and tensile strength improved by 17.65 %. Additionally, the specimens’ elongation at break was significantly enhanced.

Experimental study on mechanical, damping and corrosion properties of Inconel 718 hard-faced stainless steel 304 using cold metal transfer

Cold Metal Transfer process is used to hard-face the Inconel 718 alloy onto the Stainless Steel 304 material. The optimized parameters from the Bead on Plate trials were determined as a wire feed rate of 7 m/min, deposition speed of 15 cm/min, welding current, and voltage of 175 A and 14.9 V, respectively. Hard-facing is carried out with the sinewave weaving technique along 30 % of overlapping beads. The analysis is focused on revealing the hard-faced specimens' microstructural, mechanical, and electrochemical corrosion properties. The hard-face layer exhibits grains of mixed modes, including columnar, cellular, and fine equiaxed grains. The increased heat transfer disintegrates grain formation and reduces secondary arm spacing development. SEM-Elemental mapping shows the reduction of Niobium (3.61 %) segregation and laves formation. The overlay layer has a maximum hardness of 343.1 HV0.5 over the base substrate with 204 HV0.5. The impact test reveals the hard-faced layer absorbs more energy (26.3 %) than the substrate. Dynamic Mechanical Analysis results indicate overlay layer enhancing damping properties. The electrochemical corrosion test findings suggest that the hard-faced layer's high corrosion potential (Ecorr = 8.533 mV) corresponds to a high corrosion resistance. Phase and intermetallic formations, distribution of elements, fractured and corrosive surface morphologies are analyzed using SEM, EDX, and elemental mapping results.

Arc and molten pool behavior on quality of hybrid cold metal transfer and tandem pulsed narrow gap gas metal arc welds: a study

ABSTRACT This research proposes a novel hybrid cold metal transfer (CMT) and tandem Pulsed gas metal arc welding (P-GMAW) process for narrow gap welding (NGW) of high strength low alloy (HSLA) steel plates. Investigating three sets of lead and trail wire feed speed (WFS) ratios [WFSL/T - 1.4, 1, 0.7], the study delves into the complex arc and metal transfer behavior within the narrow gap. Utilizing synchronized arc images and current-voltage waveforms, the research assesses their influence on fusion and mechanical properties. The root pass employs the single wire CMT process, while filling and closing passes leverage tandem P-GMAW, effectively minimizing incomplete fusion and reducing heat input. Results indicate that a lower WFSL/T (0.7) reduces the molten pool hump and overflow within the narrow gap while enabling direct weld arc engagement with the previously deposited layer, enhancing weld penetration. WFSL/T of 1.4 and 0.7 revealed higher and lower Charpy impact toughness.

Effect of gas metal arc and cold metal transfer arc welding processes on microstructure and mechanical properties of AA8011-H18 alloy joints

Abstract The main objective of this study is to investigate the effect of gas metal arc welding (GMAW) and cold metal transfer arc welding (CMTAW) processes on microstructure and mechanical properties of AA8011-H18 aluminum alloy joints. The AA8011-H18 alloy sheets of thickness 3 mm were welded in butt joint configuration using conventional GMAW and CMTAW processes. The optical microscopy was employed for analyzing the microstructure of weld metal (WM) and heat-affected zone (HAZ) of the developed joints. The tensile properties and hardness of welded joints were evaluated using universal testing machine (UTM) and Vickers microhardness testing machine. The GMAW and CMTAW joints disclosed the joint efficiency of 58.33 % and 75.98 %, respectively. The CMTAW joints showed 30.25 % and 27.28 % improvement in tensile and yield strength compared to GMAW joints. However, there is a loss of 20 % ductility in CMTAW joints compared to GMAW joints. The superior tensile strength of CMTAW joints is correlated to microstructural refinement of WM and reduced grain growth in HAZ. It alludes to the wire retraction mechanism, which help to regulate the droplet transfer and lower the heat input.

Fuzzy control of backside weld width in cold metal transfer welding of X65 pipeline in the vertical-up position

Fuzzy control of backside weld width in cold metal transfer welding of X65 pipeline in the vertical-up position

Mechanical behavior of austenitic stainless steels produced by wire arc additive manufacturing

Wire arc additive manufacturing (WAAM) is an innovative technology with the potential to drive the transformation and upgrading of metallic manufacturing industry and construction sector. The advantages of WAAM technology in rapid manufacturing, design freedom, and energy saving have attracted attentions in the construction field. This research study focuses on investigating the microstructural and mechanical behavior of austenitic stainless steels produced by wire arc additive manufacturing through test programs. The stainless steel plates were first additively manufactured using cold metal transfer technology with three types of feedstock wires (ER304, ER308L, ER316L). Tensile coupon specimens and microstructural observation samples were extracted from the WAAM plates. The electron backscatter diffraction (EBSD) experiments were conducted to identify and analyze the microstructures of the WAAM austenitic stainless steels. Five test orientations, namely θ = 0˚, 30˚, 45˚, 60˚, 90˚ relative to the printing layer direction, were designed to investigate the mechanical properties anisotropy. Two types of specimen surface condition (milled type and as-built type) were considered to assess the impact of geometric undulation. The geometric features of the as-built specimens were obtained using 3D laser scanning. A total of 60 tensile tests with the aid of digital image correlation (DIC) system were conducted to obtain the stress–strain responses of the WAAM austenitic stainless steels. The mechanical properties anisotropy of the WAAM austenitic stainless steels was analyzed in detail.

Study on the effect of Ar–He shielding gas on the weld formation, microstructure and mechanical properties of 5083 aluminum alloy weld

In this paper, the ER5356 aluminum alloy wire was used for cold metal transfer (CMT) welding of the 5083-H111 base metal with 20 mm thickness. The effects of four shielding gases, which were 100%Ar, 75%Ar+25%He, 50%Ar+50%He and 100%He on the weld formation, microstructure and mechanical properties were investigated using optical microscope, scanning electron microscope (SEM), x-ray diffraction (XRD) and mechanical testing. The results showed that with the increase of He in the shielding gas, the weld penetration and width increased, and the porosity in the weld zone decreased significantly; the microstructure changed from coarse dendrites to fine equiaxed crystals, and the microstructure was gradually refined; the tensile strength of deposited metal increased from 220 MPa to 270 MPa, with an increase of 22.7%, the tensile fracture was quintessential ductile fracture, and the hardness increased from 64.2 HV to 68.4 HV. The addition of He in the shielding gas can effectively inhibit the generation of pores and promote the β-Al3Mg2 phase in the weld microstructure, thus improving the mechanical properties of the deposited metal.

Effect of coating submicron-sized La2O3 particles on regulating grain structure and mechanical properties of 6061 aluminum alloy CMT welded joints

In order to further optimize the microstructure and obtain desirable mechanical properties of cold metal transfer (CMT) welded aluminum alloys joints, this study investigated the effect of coating submicron-sized La2O3 particles on the CMT welded joints of 6061 aluminum alloy. The results showed that the introduction of La2O3 particles improved the welded wettability. However, it did not form any strengthening phase or had a grain refining effect. The introduction of La2O3 at the grain boundaries exhibited a significant segregation phenomenon, accompanied by a tendency for consistent grain orientation. To quantify this effect, the misorientation crack factor (M) was introduced, and the analysis was conducted using a combination of electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The deposition of La2O3 particles at the grain boundaries resulted in increased energy storage due to the grain size effect. As a consequence, the high energy storage region decreased the primary slip plane normal (s→) and the unit vector of the primary slip direction (n→). The reduction in misorientation crack factor was achieved by the addition of La2O3 particles, reducing the dislocation density. The combination of these two factors effectively prevented cracking behavior. Coating the welded joints with the submicron-sized La2O3 particles resulted in a 35.7% increase in their average tensile strength, and the softened area of the welded joint exhibited significant improvements in hardness comparing with that of joints before coating La2O3 particles.

316L-Si Austenitic Stainless Steel Elaborated by Additive Manufacturing Process: Porosity and Dislocation Density Estimation

This investigation estimated porosity and dislocation density in austenitic stainless steel 316LSi thin walls fabricated by Cold Metal Transfer Wire and Arc Additive Manufacturing (CMT-WAAM). Porosity density was calculated using ImageJ software. MAUD software (Materials Analysis Using Diffraction) was used to analyze the microstructural parameters and dislocation density. The density of pores and microstructural parameters of 316LSi alloy exhibit typical values of AM conditions. The porosity values oscillate between 2.80 to 3.48 %. The obtained dislocation density values are 5.0 e+12, 4.3 e+12, and 3.2 e+12 for 2.4 e+12 m-2 for 70, 80, 90, and 140 A current source, respectively. In 316LSi thin walls, the increases in the current input in CMT-WAAM are accompanied by the very lowest decrease in the dislocation density state.

Recent Developments in Cladding and Coating Using Cold Metal Transfer Technology

Recent Developments in Cladding and Coating Using Cold Metal Transfer Technology

Effect of cold metal transfer (CMT) on the unmixed zone formation in Stellite 6 overlays on ferritic steels

ABSTRACT The segregation of elements and formation of a UMZ is an unfavorable but inevitable phenomenon in dissimilar welding. The present study employed conventional GMAW welding and the CMT process with the same welding parameters to clad a flux-cored Stellite 6 electrode on an A516 Grade 60 steel. The effect of the CMT welding process on the formation of UMZ in the Stellite 6 overlay was investigated. OM and SEM were used to observe the cross-section of the samples. The distribution of the alloying elements across the interface between the weld and base metals was measured using EDS analysis. It was observed that the UMZ in the CMT welding process was thinner and more uniform which was attributed to the steady arc energy and convection flow during welding. Smaller heat input, lower penetration, and higher build-up were the main reasons for uniformity and reduced UMZ width.

Wetting mechanisms in the mass transfer process of CuSi3 droplets on the TC4 and 304SS multi-metal system controlled by the hybrid shielding gas atmosphere

To explore the synergistic wettability of the Ti-Cu-Fe multi-metal system, the wetting behaviors of CuSi3 droplets on the TC4 and 304SS plates during the cold metal transfer welding process in various gas atmospheres were studied in this work. The effects of Ti, Fe, Si, C, and O on the spreading dynamics of liquid Cu were analyzed in detail. The results reveal that the CO2 + Ar hybrid gas shielding atmosphere significantly affects the interfacial mass transfer. The sufficient interfacial reaction and increased element diffusion promoted the formation of Ti2Cu/TiCu multiphase microstructure at the Cu/Ti interface instead of a continuous Ti2Cu layer, and a thicker and loose Fe (s, s) layer was formed at the Cu/Fe interface. The variations of surface phase composition and the generation of inward flow weakened the wettability of CuSi3/TC4 and CuSi3/304SS systems. The dissolution of Si and surface adsorption of O decreased the σlv of liquid Cu, whereas Ti and Fe had the opposite effect. When the shielding gas changed from pure Ar to CO2 + Ar hybrid gas, the potential spreading model of the CuSi3/TC4 system changed from reaction-limited to diffusion-limited, and the wetting activation energy increased from 46 kJ/mol to 57 kJ/mol. Removing oxide film, forming Ti2Cu and diffusion of Ti controlled the wetting. Whereas for the CuSi3/304SS system, the potential spreading model changed from diffusion-limited to a molecular dynamics model. Removing oxide film, diffusion of Fe and interfacial adsorption were the dominant factors for wetting.

Microstructure and mechanical properties of Mg-Gd-Y-Zn-Zr alloy fabricated by cold metal transfer wire arc additive manufacturing

Wire arc additive manufacturing (WAAM) offers significant advantages in rapid manufacturing of complex integral parts. In this study, Mg-Gd-Y-Zn-Zr alloy deposited walls were fabricated by cold metal transfer (CMT) based WAAM. The interface bonding relationship between the additive zone and the substrate was studied, as well as the effect of the microstructure of the additive zone on the mechanical properties. The precipitated phase Mg24Y5 mainly distributed at the grain boundary was found in the additive zone of deposited walls, nano-scale contact interface and diffusion bonding interface were formed between β-Mg24Y5 and α-Mg (OR: [001]β-Mg24Y5//[10 1‾ 0]α-Mg), and a portion of the 18 R-LPSO phase to 14H-LPSO phase transition occurred in the substrate zone. In each layer of deposited metal, the bottom zone had a higher cooling rate than the top zone, which led to the supersaturation of rare earth elements. The precipitated phases between different deposition layers showed a decreasing trend from the bottom zone to the top zone due to the complex multiple thermal cycles in the additive manufacturing process. Compared with the cast Mg-Gd-Y-Zn-Zr alloy, the mechanical properties (UTS, YS and EL) of the Mg-Gd-Y-Zn-Zr alloy fabricated by WAAM were significantly increased. The ultimate tensile strength of the deposited walls along the travel direction was 227.27 MPa, and the elongation was 8.08 %.

Experimental investigation of microstructural, mechanical and corrosion properties of 316L and 202 austenitic stainless steel joints using cold metal transfer welding

The objective of the current experimental study is to investigate influence of dissimilar welding between 316 L Austenitic and 202 Austenitic Stainless Steel. This is achieved through the utilization of Cold Metal Transfer (CMT) Welding in conjunction with the GTAW mode. Various welding approaches are employed, including the use of ER316L and ER309L fillers, as well as a no-filler (autogenous) welding technique. Microstructural observation shows martensitic formation in the interface region. The tensile test was conducted by using Universal Testing Machine for the weldment and found that ER316L filler (721 MPa) has higher strength than ER309L (672 MPa) and autogenous weld (528 MPa). Charpy impact test was used to determine toughness of the weldment and found that ER309L Filler weld has toughness (87 J) which is higher than ER316L filler weld (5 4 J) and autogenous weld (23 J). Vicker's hardness test shows that autogenous weld hardness (avg. 193.34 HV) which is highest than ER309L filler (avg.188 HV) and ER316L filler weld (avg. 184.67 HV). The intergranular corrosion test by double loop electrochemical potentiokinetic reactivation (DLEPR) test shows sensitization at highest degree for autogenous weld (18.25 %) than ER316L filler weld (9.22 %) and ER309L filler weld (7.28 %).

A comparative study on weld-bead geometry of austenitic stainless-steel produced by cold metal transfer welding and pulse metal inert gas welding process

In recent years, weld cladding has become an emerging technique for the surface modification of carbon steel, which has various industrial applications such as chemical, marine, mining, agriculture, and power generation. In this research, cold metal transfer (CMT) welding and pulse metal inert gas (MIG) welding are utilized to study the weld-clad bead of 308L stainless steel over low-carbon steel. To examine the mechanical and wear characteristics of CMT weld-clad samples, welding speed (3, 4, 5, and 6 mm/s) was used as the input process parameter, while current (175 A), nozzle to workpiece distance (10 mm), and shielding gas flow rate (15 l/min) were kept constant. Microstructural analysis of weld bead samples was done through optical microscopy and field emission scanning electron microscopy. With an increase in welding speed, the microhardness and wear properties of the clad surface were improved. The CMT-clad surface had significant improvements in mechanical, wear properties, and lower residual stresses due to low dilution and lesser heat input.

Processing of Bimetallic Inconel 625-16Mo3 Steel Tube via Supercritical Bend: Study of the Mechanical Properties and Structure.

Incineration is currently the standard way of disposing of municipal waste. It uses components protected by high-temperature-resistant layers of materials, such as Inconel alloys. Therefore, the objective of the current paper is to study the mechanical properties and structure of a bimetallic Inconel 625-16Mo3 steel tube. The Inconel 625 layer was 3.5 mm thick and was applied to the surface of the tube with a wall thickness of 7 mm via the cold metal transfer method. The bimetallic tube was bent using a supercritical bend (d ≤ 0.7D). This paper is focused on the investigation of the material changes in the Inconel 625 layer areas influenced by the maximum tensile and compressive stresses after the bend. The change in layer thickness after the bend was evaluated and compared to the non-deformed tube. In addition, the local mechanical properties (nanohardness, Young modulus) across the indicated interfacial areas using quasistatic nanoindentation were investigated. Subsequently, a thorough microstructure observation was carried out in areas with maximum tensile and compressive stresses to determine changes in the morphology and size of dendrites related to the effect of tensile or compressive stresses induced by bending. It was found that the grain featured a stretched secondary dendrite axis in the area of tensile stress, but compressive stress imparted a prolongation of the primary dendrite axis.