Cold Metal Transfer Technique Research Articles

Mechanical and Metallurgical Characteristics of Wire-Arc Additive Manufactured HSLA Steel Component Using Cold Metal Transfer Technique

Recently, the application of wire-arc additive manufacturing (WAAM) for the production of metallic products is gaining traction. WAAM is associated with the direct energy deposition technique and therefore has a higher deposition rate (approximately 4 kg/h). For this reason, it is of greater interest than powder-based additive manufacturing techniques. Industrial applications such as marine and offshore structures and pressure vessels for space programs commonly utilize high-strength low-alloy (HSLA) steel. HSLA steel components produced by casting methods exhibit defects due to oxidation. Therefore, cold metal transfer (CMT)-WAAM was adopted in this study to fabricate HSLA steel components. The metallurgical properties were analyzed using microscopic and diffraction techniques. The effects of the evolved microstructures on mechanical properties, such as strength, microhardness, and elongation to fracture, were evaluated. To analyze and test the structure, two regions were selected, namely, top and bottom. Microstructural analyses revealed that both regions were primarily composed of acicular ferrite, polygonal ferrite, and bainitic structures. The bottom region exhibited superior mechanical properties compared with the top region. The improved strength at the bottom region can be ascribed to the formation of a high density of dislocations and finer grains.

Exploring the cutting edge: Recent trends in cold metal transfer welding

Cold metal transfer welding is known for its automated welding process, which is equipped with shortcircuit-based deposition of filler wire, which allows it to control its heat input parameter properly along with a wire feed rate. Cold metal transfer’s main characteristic, which greatly affected the manufacturing industries, is joining thin, similar, or dissimilar metal sheets as the processing heat input is minimal. This review paper (covering 104 studies) examines how joining different metals with varying welding parameters affects their weld appearance, microstructure, tensile strength, and the formation of joint failure. The main focus was on what additional methods, like hardfacing or post-heat treatment of material, must be adopted to enhance the joint's weld quality and appearance. The paper starts with the investigation of numerous dissimilar weld joints formed by the cold metal transfer technique, along with the effect of varying welding parameters and ultrasonic-assisted cold metal transfer hybrid welding on the weld quality and post–pre-weld heat treatment of materials. A comparison of different cold metal transfer arc modes employed in wire-arc additive manufacturing has also been discussed briefly. At the end of the analysis, it was noted that some metal joints had a positive impact, and some gained a negative effect while increasing the heat input. The research articles studied in this paper indicate that not every material would exhibit the same welding property when subjected to a specific set of varying welding parameters.

Microstructural and mechanical properties analysis of SS 316L structure fabricated using CMT-wire arc additive manufacturing

Integrating robotic arm technology with cold metal transfer (CMT) has revolutionized wire arc additive manufacturing (WAAM). The research work consists of the fabrication of SS 316L WAAM using the CMT technique. Investigations of mechanical and microstructural properties, i.e. residual stress measurement (RSM), microhardness (MH), ultimate tensile strength (UTS), percentage elongation (PE), and microstructure of WAAM sample and cold rolled (CR) plate, results were compared. WAAM attained an UTS of 590 MPa, with an average yield strength (YS) of around 302 MPa, exceeding the CR plate’s UTS of 557 MPa while maintaining a similar YS of 305 MPa. WAAM and the CR plate exhibited nearly identical PE, with 64% and 62% values, respectively. Residual stress analysis revealed that the WAAM sample showed an average compressive residual stress of 124 MPa, accounting for 87% of the average residual stress observed in the CR plate, which measured 142 MPa. The MH profile of WAAM revealed an average value of 230 HV0.5, accounting for 88% of the MH observed in the CR plate at 260 HV0.5. The performance of WAAM closely matched that of the CR plate in terms of residual stress and MH.

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

Wire-arc directed energy deposition super martensitic stainless steel with excellent strength and plasticity

Super martensitic stainless steel (SMSS) is wildly used in hydroelectric, petrochemical, and nuclear power industries relying on high strength and sound weldability. While the low ductility and high strength make it difficult to be deformed and machined. The wire-arc directed energy deposition (DED) process allows a high deposition rate and can produce high-quality parts. In this study, the SMSS thin-wall parts were fabricated through wire-arc DED with the cold metal transfer technique. This research aims to investigate the microstructural evolution regulation and mechanical performance improvement mechanism of the additive manufacturing SMSS parts and achieve good comprehensive performance. The microstructure of the as-deposited wall consists of full lath martensite with columnar and fine equiaxed grains in periodic alternation layer by layer. By regulating the temperature between each layer, the overall wall's microstructure is kept consistent. The yield strength and ultimate tensile strength of the as-deposited wall are 1046 and 903 MPa with total elongation of 9 % and impact energy of 16 J. Thus, the toughness and plasticity needed to be improved by heat treatment. Based on the energy dispersive spectroscopy (EDS) technique and diffraction pattern analysis using transmission electron microscopy (TEM), the phases formed during the intercritical tempering process were identified as tempered martensite and reversed austenite. The enhancement of toughness is associated with austenitic transformation-induced plasticity. The amount of reversed austenite is 29.5 % at 600 °C and then disappeared at 700 °C. The best comprehensive mechanical properties were obtained at a temperature of 550 °C with an ultimate tensile stress of 927 MPa, yield stress of 850 MPa, impact energy of 33 J, and elongation of 18 %, comparable to the rolled parts.

Microstructure and Mechanical Properties of Weaving Wire and Arc Additive Manufactured AZ91 Magnesium Alloy Based on Cold Metal Transfer Technique.

Based on the cold metal transfer (CMT) technique, a deposited wall of AZ91 magnesium alloy was fabricated by weaving wire and arc additive manufacturing (WAAM), the shaping, microstructure, and mechanical properties of the sample with the weaving arc were characterized and discussed by compared with the sample without the weaving arc, and the effects of the weaving arc on grain refinement and property enhancement of the AZ91 component by CMT-WAAM process were investigated. After introducing the weaving arc, the effective rate of the deposited wall could be increased from 84.2% to 91.0%, and the temperature gradient of the molten pool could be reduced with an increase in constitutional undercooling. The equiaxed α-Mg grains became more equiaxial due to the dendrite remelting, and the β-Mg17Al12 phases distributed uniformly induced by the forced convection after introducing the weaving arc. Compared to the deposited component fabricated by the CMT-WAAM process without the weaving arc, the average ultimate tensile strength and elongation of the component by weaving the CMT-WAAM process both increased. The weaving CMT-WAAM component showed isotropy and has better performance than the traditional cast AZ91 alloy.

Optimization of processing parameters of cold metal transfer joined 316L and weld bead profile influenced by temperature distribution based on genetic algorithm

Austenitic stainless steel alloys find the wide range of application in modern industries like pipework, containers, food production and in medical industries for its excellent processing properties and corrosion resistance. There is enormous literature report on the mechanical properties, appropriate joining of materials using different fusion welding processes. Consequently, the cold metal transfer technique appears to weld materials with low heat input which is a noticeable feature of this welding process. In this paper, cold metal transfer welding is performed on austenitic stainless steel material 316L and its bead geometries such as reinforcement height, depth of weld penetration and bead width profile are examined. The temperature distribution at the welding line is observed by means of the data acquisition unit. Genetic algorithm based optimization technique is used to achieve the desired combination of input variables and weld bead geometry. This developed genetic algorithm optimizes the welding process parameters and geometry of the weld bead, by minimizing the least square error based objective function. The investigation outcome of this paper provides an insight into the characterization of the weldment, the effects of weld current and weld travel speed on temperature profile and mechanical properties include hardness, tensile and residual profiles.

Microstructure and Pitting Corrosion Resistance of AISI 430 Ferritic Stainless Steel Joints Fabricated by Ultrasonic Vibration Assisted Cold Metal Transfer Technique

The influences of ultrasonic vibration during cold metal transfer welding process on the microstructure, element distribution and pitting resistance of AISI 430 ferritic stainless steel joints with ER 308L as filler metal were investigated. The combined effects of mechanical vibration, acoustic streaming and cavitation of ultrasonic vibration significantly refined the primary ferrite grain in the weld metal and then impacted the subsequent solid-phase transition process, leading to the ~45% reduction of ferrite content in the weld metal. Moreover, these effects also resulted in the homogenization of alloying elements in the weld metal. The pitting corrosion resistance of the welded joints with ultrasonic vibration was increased compared with that of without ultrasonic vibration, but lower than the base metal. The pitting resistance of the weld metal with ultrasonic vibration was higher than that of the weld metal without ultrasonic vibration and base metal, while that of the one without ultrasonic vibration was lower than the base metal.

Process Variable Optimization of Cold Metal Transfer Technique in Cladding of Stellite-6 on AISI 316 L Alloy Using Grey Relational Analysis (GRA)

In this work, an attempt was made to identify the optimised parameter combination in cold metal transfer (CMT) cladding process of AISI 316 L austenitic stainless steel. cladding process was carried out using stellite 6 filler wire. Experiments were carried out based on L31 central composite design (CCD). Cladding was done with current, Voltage, torch angle and travel speed as input parameters. Quality of the clad was analysed by measuring depth of penetration, weld area, hardness of the clad surface, corrosion rate and clad interface thickness. Grey relation analysis was used to identify the optimised parameter combination. Trial number 18 was identified as the optimised parameter combination. The optimised input parameters are Welding Current 200 Amps, Voltage 19 V, Torch Angle 70⁰ and Welding Speed 150 m/min. ANOVA was used to identify the most influencing parameters on the overall multi-objective function and it was understood that the combined effect of torch angle, travel speed had a significant influence on the clad quality. Further investigation was carried out through an optimised set of parameters. The cladding experiment was conducted and their surface was investigated through clad profile, hardness of the cladded area, interface thickness of cladding region and corrosion rate.

Influence of Silicon and Magnesium on the Mechanical Properties of Additive Manufactured Cu-Al Alloy.

By using cold metal transfer technique, Cu-Al alloy with addition of silicon (Si) and magnesium (Mg), viz (1) Cu-6.5% Al and (2) Cu-6.5% Al-1.2% Si-0.5% Mg were manufactured additively. Four samples were deposited: Cu-6.5% Al alloy as samples 1 and 2, and Cu-6.5% Al-1.2% Si-0.5% Mg alloy as samples 3 and 4. The alloys were homogenized by heat treatments: (1) 800°C (2 h) for sample 2 and (2) sample 4, to improve their mechanical properties. Detailed microstructural investigation conducted using scanning and transmission electron microscopies showed formation of various intermetallic phases. Results revealed that (1) the addition of Si and Mg increases the strength properties and ductility and (2) heat treatments improved strength properties but reduce the ductility of the alloys. The article discusses the correlation of the identified microstructure and the evaluated mechanical properties of the additively manufactured alloys.

Effect of friction stir processing on microstructure and properties of AZ91 magnesium alloy CMT cladding layer

AZ91 magnesium alloy cladding layer obtained by cold metal transfer technique was subjected to friction stir processing (FSP). The results showed that, after FSP, the grains of the deposited layer were significantly refined, and the coarse β-Mg17Al12 phase was broken and dispersed into the α-Mg matrix, leading to the microstructure modification. Compared with the unprocessed cladding layer, the FSPed samples exhibited better corrosion resistance. Due to the grain refinement and disintegration of the second phase, the tensile strength and elongation of the cladding layer after FSP increased from 233.4 MPa and 5.6% to 278.5 MPa and 13.4%, respectively.

Microstructural Evolution and Mechanical Properties of Ti Alloy/Stainless Steel Lap Joints during Cold Metal Transfer Technique with CuSi3 Filler Wire

Joining of dissimilar titanium (Ti) alloy to stainless steel is a very significant challenge during conventional fusion welding. In this study, cold metal transfer (CMT) technique is developed for lap joining of Ti alloy to stainless steel with CuSi3 filler wire. The microstructure evolution, mechanical properties and fracture mechanism of Ti alloy/stainless steel joints are investigated. When low heat input is applied, many fine spherical particles are distributed in the fusion zone, which are indicated as iron-rich phase in the Cu matrix. With an increase in the heat input, the particles become irregular and coarser in the fusion zone, inferring as Fe-Si-Ti ternary phase and Fe2Ti phase. Since the fractions of the melted Ti alloy and stainless steel increase, the reaction of Ti with Fe and Si becomes more intense and Fe-Si-Ti ternary phase and Fe2Ti phase thus appear in the fusion zone. The shear strength of the lap joints decreases with an increase in the heat input. There are two fracture modes in the lap joints, suggesting different fracture mechanisms. The fracture path of the joints is along the Ti-Cu interface under low heat input. The brittle Ti-Cu intermetallics are observed on the fracture surface, indicating that the shear strength and fracture feature of the joints are associated with the compound layer. The fracture failure of the lap joints occurs in the fusion zone under large heat input. The Fe-Si-Ti ternary phase and Fe2Ti phase have detrimental effects on the joint strength, resulting in a brittle fracture in the fusion zone.

Effect of pulsed metal inert gas (pulsed-MIG) and cold metal transfer (CMT) techniques on hydrogen dissolution in wire arc additive manufacturing (WAAM) of aluminium

Aluminium is one of the most experimented metals in the WAAM field owing to a wide range of applications in the automotive sector. Due to concerns over reduction of strength, elimination of porosity from wire arc additive manufactured aluminium is one of the major challenges. In line with this, the current investigation presents findings on hydrogen dissolution in solid aluminium and hydrogen consumed to form porosity along with its distribution as a function of heat inputs and interlayer temperatures in a WAAM 5183 aluminium alloy. Two varieties of WAAM, pulsed metal inert gas (MIG) and cold metal transfer (CMT), were explored. Samples made with pulsed metal inert gas (pulsed-MIG) process picked up more hydrogen compared to samples produced by cold metal transfer technique. Correspondingly, pulsed-MIG samples showed increased number of pores and volume fraction of porosity than samples manufactured using the cold metal transfer (CMT) technique for different heat input and interlayer temperature conditions. However, CMT samples exhibited higher amount of dissolved hydrogen in solid solution compared to pulsed-MIG process. In addition, heat input, interlayer temperature, and interlayer dwell time also played a key role in pore formation and distribution in WAAM-produced aluminium 5183 alloy.

Macrostructure, microstructure and wear performance of Al alloy cladding fabricated by CMT technique

The macrostructure, microstructure and wear performance of Al cladding fabricated by cold metal transfer (CMT) technique were investigated. The overlaps were formed on both sides of Al cladding using CMT technique with direct current mode. The weld depth and contact angle increased, and the overlap length reduced with an increase of heat input, which can be realized by increasing wire feed speed (WFS) or arc length correction (ALC). The grain size and thickness of heat affected zone increased with an increase of heat input, which resulted from increasing WFS or ALC. Due to the increase of average grain size, the hardness value of the clad Al alloy reduced with the increase of ALC. Besides, wear rate increases with an increase of ALC under the scope of load between 80 and 120 N and time between 10 and 20 min. The grooves are clearer at the wear surfaces with an increase of ALC at the wear surface.

Effect of varying weld speed on corrosion resistance and mechanical behavior of Aluminium - steel welds fabricated by cold metal transfer technique

ABSTRACTLap welds of 19000 Al–Zinc layered mild steel were joined by Cold Metal Transfer technique using Al-12% Si filler wire as a function of varying weld speed (0.5–1 m.min−1). The weld cross-section was characterized by electron microscopy techniques. Micro XRD was used for the phase analysis of the intermetallic layer generated at welding bead–steel interface in the weld samples. The mechanical strength of joints was evaluated by lap shear testing and corrosion evaluation was done following ASTM G 67–04 and ASTM G 48–03, respectively. Results have shown that the IMC layer width decreased with an enhanced welding speed resulting in lower intergranular corrosion. The layer width ranged between 0.45 and 2.3 µm in both the weld samples. During weight loss evaluation, the sample with lower welding speed exhibited a weight loss of 41.8 mg and the sample welded with higher speed had shown a weight loss of 7.75 mg. At higher weld speeds, lower volume fraction of intermetallics was observed resulting in reduced corrosion. The welds have shown optimum mechanical strength during lap shear test and failed in the base material region of Aluminium alloy.

Influence of fuel ashes on corrosion of surface coatings cladded by CMT method

ABSTRACT The aim of the present research was to investigate the influence of different biomasses and sewage sludge ash (at 650°C for 1000 h and 2000 h, respectively) on the surface of weld cladded (Cold Metal Transfer technique, CMT) stainless steels 309 and 310. The biomass ashes were rich in K2O, CaO, SiO2, whereas sewage sludge ash in P2O5, CaO, Fe2O3, and SiO2. Characterization of the stainless steel cross-section and surface after the corrosion process inducted by the presence of ash were carried out by scanning electron microscopy (SEM) with EDAX analysis. Phase analysis of corrosion products was made by X-ray diffraction (XRD). Chromium, nickel, and iron oxides were the main oxides which occurred after the corrosion test. It has been proved that biomass ashes have the corrosive properties (because of their chemical composition) and are more aggressive than the sewage sludge ash for that kind of materials.

Microstructure, microsegregation and nanohardness of CMT clad layers of Ni-base alloy on 16Mo3 steel

Microstructure and properties of Inconel 625 coatings deposited by the Cold Metal Transfer technique on a 16Mo3 boiler tube were investigated. The clad layers were shown to have a typical cellular-dendritic structure with secondary phases in the interdendritic regions (e.g. Laves phases and complex nitrides/carbides (MX)). Nanohardness of the interdendritic regions was higher than of the ɣ matrix dendritic regions. Energy dispersive X-ray spectroscopy analysis revealed microsegregation of Ni, Cr, Fe to the dendritic regions, as well as interdendritic segregation of Nb and Mo. Based on the phase identifications performed, a new solidification path is proposed.

TEM Microstructure and Chemical Composition of Transition Zone Between Steel Tube and An Inconel 625 Weld Overlay Coating Produced by CMT Method

AbstractThe aim of this work was to investigate the microstructure and chemical composition of the transition zone between 16Mo3 steel and Inconel 625 weld overlay coating produced by the Cold Metal Transfer (CMT) method. Investigations were primarily carried out through transmission electron microscopy (TEM) on thin foils prepared by FIB (Focus Ion Beam).The chemical analysis demonstrated that the amount of certain elements (Fe, Ni, Cr, Mo, Nb) in the transition zone between the base material and the weld overlay changes quickly, from the composition of the steel to the composition of the composite zone. STEM and TEM investigations revealed that two areas are clearly visible in the transition zone. In the narrow band close to the fusion boundary where plates are clearly visible and theMstemperature is higher than room temperature, electron diffraction analyses show reflections of martensite and austenite. Moreover, the crystallographic relations between martensite and austenite can be described by the Kurdjumov-Sachs (K-S) relationship$\{ 110\} _{\alpha '} ||\{ 111\} _\gamma < 1\bar 11 > _{\alpha '} || < 1\bar 10 > _\gamma $). The microstructure of the part of the transition zone with anMstemperature lower than room temperature as well as that of the composite zone is austenite. The investigations proved that the width of the martensitic area can be significantly limited by using the CMT technique for weld overlaying.

Investigations on the parametric effects of cold metal transfer process on the microstructural aspects in AA6061

Aluminium alloy sheets are find utility in various diversities of industrial sectors due to its multifunctional features and global suitability. There have been several literatures reporting mechanical and microstructure analysis and suitability of joining of this material using various welding techniques. Subsequently, it has been proved successful for several welding processes irrespective of the heat flow phenomenon. However, the width of heat affected zone remains a challenge for all the conventional processes. In view of this, it is observed that cold metal transfer technique appears to reduce the HAZ width due to its low heat input to the base metal which is the most prominent feature of the process. In this paper, the effect of welding current and welding speed on heat input, depth of penetration, weld pool width, reinforcement height, dilution, weld bead contact angle parameters during cold metal transfer (CMT) process is investigated. The outcome of this research study is expected to provide a thorough insight into the heat input, strength, microstructures of weld zone and integrity of the weldments for different trails of welding current and welding speed which facilitates in determining the optimized parameter range.

Microstructure and Microsegregation of an Inconel 625 Weld Overlay Produced on Steel Pipes by the Cold Metal Transfer Technique

Abstract The aim of this work was to investigate the development of microstructure and variations in chemical composition in commercial Inconel 625 coatings on a ferritic-pearlitic steel overlaid by the CMT method.The investigation showed that microsegregation occurring during the weld overlay solidification makes the dendrite cores to be richer in Ni, Fe and Cr and in the between dendrite arms in Mo and Nb. Niobium shows the strongest tendency to segregation during solidification; molybdenum tends to segregate less and chromium has the lowest tendency to segregation. Although Inconel 625 is a solid solution strengthened alloy, Nb and Mo-rich phases are formed in the between dendrite arms of weld overlays.