Wire Arc Additive Manufactured Research Articles

Anisotropic behavior of super duplex stainless steel fabricated by wire arc additive manufacturing

Broadening the understanding of the anisotropic behavior of super duplex stainless steel (SDSS) fabricated by wire arc additive manufacturing (WAAM) can provide valuable insights for designing and optimizing WAAM components. The purpose of this study is to investigate the anisotropic behavior between mechanical properties, corrosion resistance, microstructure and crystallographic features of wire arc additive manufactured (WAAMed) SDSS thin-wall component, by means of optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), hardness testing, tensile testing and electrochemical corrosion testing. Meanwhile, a control sample set prepared from commercial hot-rolled SAF 2507 SDSS was also investigated for comparison. The results show that the mechanical properties and corrosion behaviors of WAAMed SDSS are anisotropic, which are attributed to the nonequilibrium phase ratio and anisotropic crystal features in the as-built WAAMed SDSS affected by the repeated thermal cycles inherent to WAAM process.

Interplay between microstructure, micromechanical, and tensile properties in wire arc additive manufactured nickel-aluminum bronze: As-built and heat treated

The generalized hardness-strength relationship in additively manufactured materials may differ from that observed in cast/wrought materials. To investigate this, the present study focuses on wire-arc additive manufactured (WAAM) Nickel-Aluminum Bronze (NAB) in both its as-built state and three distinct heat-treated conditions. Tensile tests and nanoindentation hardness tests were conducted simultaneously to establish a correlation between hardness and strength. Additionally, a comparison is made between the cast-NAB material and WAAM-NAB in this article. By considering the variations in grain size (coarse vs. fine) and intermetallic compounds in the cast and WAAM-NAB materials (in their as-built and post-heat treated forms), the correlation factor is found to differ based on the specific manufacturing processes and heat treatments employed. This paper aims to develop empirical equations that account for the various influencing factors, including rigid plasticity and uniform plastic work hardening conditions. Moreover, the study reports several indentation-based quantitative variables, such as the plasticity index, elastic recovery, recovery resistance, and wear resistance index of the WAAM-NAB material. By providing a comprehensive analysis of these factors, this research contributes to a better understanding of the hardness-strength relationship and the associated material properties in WAAM-NAB.

Influence of build direction and heat treatment on the microstructure and tensile characteristics of cold metal transfer based wire arc additive manufactured SS 304L

Wire arc additive manufacturing has gained a noble position in the field of manufacturing metallic structures. This paper aims to evaluate the effect of build direction and heat treatment on the tensile behaviour along three different orientations: transverse (T), longitudinal (L), and diagonal (D). Microstructural investigations have been conducted to identify the microstructural features caused by CMT-based WAAM and its relation to mechanical properties. The results revealed a fine microstructure with austenite and ferrite phases and the formation of ferrite morphologies. For the untreated and treated specimens, respectively, the ferrite percentage was greater in the middle of the samples and is 12.29% and 11.21%. The WAAM components exhibited good tensile properties with a clear indication of anisotropic behaviour with respect to building direction. The diagonal specimen from WAAM and heat-treated WAAM resulted in better tensile properties. Additionally, it demonstrates a significant rise in Young's modulus value compared to the standard value for SS304L and other directional specimens in both treated and untreated circumstances. The percentage of anisotropy in WAAM and heat-treated specimen ranges from 6.42% to 57.76%. Fine microstructure creation and directional grain growth have produced resistance to slip movement in different orientations in different ways, resulting in the anisotropic behaviour of WAAM fabricated components.

Effect of Severe Shot Peening on Mechanical Properties and Fatigue Resistance of Wire Arc Additive Manufactured AISI 316L

The wire arc additive manufacturing (WAAM) technology has become very popular recently. However, the properties of printed pieces are not yet examined properly. In this paper the effect of severe shot peening (SSP) on mechanical properties of wire arc additive manufactured AISI 316L is investigated. The effect of SSP on the surface hardness of the WAAM 316L is investigated by performing microhardness measurements. Changes to the surface microstructure caused by SSP are evaluated in the EBSD investigation. The effects of SSP on tensile and fatigue strength are investigated experimentally. The EBSD analysis showed that there has been remelting of each printed layer due to the heat input from the next printed layer, and heavy epitaxial grain growth was present in the microstructure. This led to coarse columnar grain structure. Investigation of deformed SSP surface layer indicated that the main deformation type was either conventional dislocation glide or twinning. This meant that no martensite formation was present on the surface. The SSP increased the surface hardness of WAAM printed 316L by 225% and the hardened layer was 0.4 mm thick. The SSP improved the yield strength of WAAM 316L by 34%. The SSP significantly improved WAAM 316L fatigue resistance in both low-cycle and high-cycle regime.

Performance evaluation of interfacial characteristics between cold metal transfer-wire arc additive manufactured SS308LSi and wrought SS304L with controlled and uncontrolled interlayer temperature

The present work investigates the mechanical behavior and microstructure evolution of the interface between the cold metal transfer (CMT)-wire arc additive manufactured (WAAM) SS308LSi and wrought SS304L via controlled interlayer temperature (CIT) of 100–120°C and uncontrolled interlayer temperature (UIT). The thermal cycles on the substrate were recorded using K-type thermocouples and correlated with the mechanical and microstructure properties of deposited walls. Microstructure analysis of the interface cross-section revealed a defect-free interfacial bond with a columnar solidification structure with slightly coarser grains under UIT deposition compared to CIT deposition. The microhardness of wrought SS304L is in the range of 196 ± 9 HV, while that of UIT and CIT deposited 308LSi is 178.4 ± 7.02 HV and 183.4 ± 6 HV, respectively, with no aberrant hardness values at the interface. Tensile tests were performed on the wrought SS304L and WAAM SS308LSi transverse to their interface. The results revealed that interface strength is higher than that of WAAM deposits and failed with average ultimate tensile strengths of 589.1 and 580.9 MPa under CIT and UIT depositions, respectively. This work reveals that CMT-WAAM can produce high-quality interfacial bonding between WAAM SS308LSi and wrought SS304L.

Microstructure and mechanical properties of wire arc additive manufactured ZL205A alloy

The evolution of grain structure, precipitates and mechanical properties of the ZL205A alloy prepared by wire arc additive manufacturing were investigated. The results show that the as-deposited alloy consists of equiaxed and columnar grains in the bottom region. As the deposition height increases, the alloy mainly consists of equiaxed grains. The evolution of columnar to equiaxed grains is explained by the solidification theory. The needle-like θ′-Al2Cu precipitates in Cu-rich regions surrounding the α-Al+θ-Al2Cu eutectics. As the part deposited first is subjected to multiple cycles of heating by the subsequently deposited layers, the volume fraction and average size of θ′ precipitates gradually decrease with the increase of deposition heights. The microhardness of the as-deposited alloy fluctuates in the range of 74.6–84.5 HV. The mechanical properties of the horizontal specimens at different heights are affected by the combination of grain structure, precipitates and pores, and that of the specimens in the middle region are optimal. The mechanical properties of the horizontal and vertical specimens show isotropic. Attributed to the grain boundary strengthening and precipitation strengthening, the yield strength (132.9 MPa) and elongation (15.9%) of the as-deposited alloy are approximately 31.3% and 211.8% higher than that of the as-cast alloy, respectively.

Fatigue characterization of wire arc additive manufactured AWS ER100S-G steel: fully reversed condition

To overcome the limitations associated with the conventional fabrication (e.g., casting, forging, assembly) of large-sized complex structures, in this study, we assess large format additive manufacturing (wire arc additive manufacturing) as a potential replacement using high-strength low alloy wire feedstock (AWS ER100S-G). The process/microstructure/property/fatigue correlations of AWS ER100S-G (a low carbon high strength electrode filler utilized in gas metal arc welding) fabricated by wire arc additive manufacturing (WAAM) are presented in detail. Characterization tools such as the optical microscope, scanning electron microscope with electron backscattered diffraction, μ-CT scan, and mechanical testing (tensile, hardness, fully reversed fatigue tests) were utilized to quantify the property correlation of the WAAM’d AWS ER100S-G. To identify the controlling mechanism of fatigue crack initiation and fatigue crack growth pattern, scanning electron microscopy-based fractography assessments were conducted on the fracture surface of the broken specimens. Our findings were then compared against WAAM’d chemically closed steel (e.g., AWS ER100S-1 and AWS ER70S-6) reported in the literature. Regarding fatigue performance, the AWS ER100S-1 outperformed the studied AWS ER100S-G, and the AWS ER100S-G outperformed the AWS ER70S-6.

Strengthening of wire arc additive manufactured aluminium alloy through interlayer rotary friction processing

To eliminate porosity and refine the grains in aluminium alloys fabricated via wire arc additive manufacturing (WAAM), a novel strengthening method – robotic rotary friction processing (RFP) – was introduced. The feasibility of RFP was assessed by processing the deposited beads under various average peak loads. During RFP, a rotating tool pressed the deposited beads to induce sufficient plastic deformation. After 3.5 kN-RFP, the WAAM densification ratio was improved to >99.5%, and pores were completely closed and eliminated owing to compression deformation and sub-grains bonding. The processed deposits exhibited effective grain refinement and high-density dislocation entanglement, which led to 22.8% and 34.2% improvements in the horizontal and vertical tensile strengths, respectively. Furthermore, the strengthening mechanism of RFP on deposited metals was clarified.

Effects of deposition paramaters on the microstructure evolution of wire arc additive manufactured Al–Zn–Mg–Cu alloy

Wire arc additive manufacturing (WAAM) is a suitable method for fabricating large high-strength components made of the Al–Zn–Mg–Cu alloy. However, the solidification behavior of this alloy is complex due to its composition. The inhomogeneous solidification microstructure results in numerous defects during the deposition process, hindering the application of the deposited Al–Zn–Mg–Cu alloy. This study aims to analyze the microstructure evolution under different process parameters and reveal the relationship between the solidification behavior of the molten pool, pore defects, and grain morphology. Thin-walled components based on Al–Zn–Mg–Cu alloy were fabricated using WAAM under different parameters. The results showed that increasing deposition current initially decreased and subsequently increased pore defects, while the proportion of twinned dendrites exhibited the opposite trend. A lower deposition speed reduced pore defects by promoting gas escape, whereas a higher deposition speed led to the precipitation of Al3Zr, grain refinement, and the suppression of twin dendrite growth. A faster wire feeding speed had a better suppression effect on defects, while a slower wire feeding speed inhibited the growth of twinned dendrites, promoting the directional growth of regular dendrites.

Influence of the interlayer temperature on structure and properties of CMT wire arc additive manufactured NiTi structures

A potential method for producing intricate Shape Memory Alloy (SMA) structures for uses like actuators and vibration dampers is wire arc additive manufacturing (WAAM). However, excessive heat build-up during the multi-layer deposition procedure in WAAM can result in process instability and departures from the intended mechanical qualities and dimensions. To address these problems, the interlayer temperature was optimized for printing on NiTi walls in this work. Without interlayer temperature control (WITC), 200 °C, and 400 °C were used to create three samples in order to study the impacts on the porosity level, morphology, and mechanical characteristics of the NiTi walls generated by WAAM. The Shape memory behavior of the manufactured NiTi walls was further examined through shape recovery investigations utilizing hot plate actuation. The findings demonstrated that regulating the interlayer temperature below 300 °C, preferably at 200 °C, enhanced the mechanical characteristics, decreased the porosity content, and enhanced the microstructure of the NiTi walls. The development and improvement of WAAM techniques for the manufacture of premium NiTi SMA components can benefit greatly from these findings.

Role of δ-phase on Mechanical Behaviors of Additive Manufactured Inconel 718: Detailed Microstructure Analysis and Crystal Plasticity Modelling

In this work, a multi-scale approach was applied to reveal the evolution mechanisms of the δ (Ni3Nb) phase and the resultant mechanical responses in wire-arc additive manufactured (WAAM) Inconel (IN) 718. Several heat treatment strategies, consist of homogenization, intermediate heat treatment and aging process, were firstly conducted to produce δ phases with different characteristics. The early evolution of the δ phase was then analyzed in detail via transmission electron microscopy. The nanoindentation and tensile tests were also used to verify the strengthen response of δ phase. Moreover, a crystal plasticity finite element (CPFE) model, taking into account the different configurations of δ phase, was developed to study and predict the micro deformation behavior. Results revealed that when the intermediate heat treatment time exceeded 1 h, the formation of the main strengthening phase γ" was constrained by the δ phase, accompanied by the coarsening of γ". The decrease of γ" phase and the destruction of coherent γ"/γ interface are the main causes of strength loss in the WAAMed IN718. The intergranular dislocation transmission was hindered by the δ phase, thereby increasing the grain boundary strength. However, the needle-like δ phase within the grain may cause premature fracture due to strain localization, thereby reducing the material properties. The evolution mechanisms of the δ phase obtained in this study provides theoretical guidance for the optimization of the microstructures and mechanical properties of WAAM Inconel 718.

Achieving high strength-ductility properties of wire-arc additive manufactured Al-Mg-Sc aluminum alloy via friction stir processing post-treatment and high temperature aging treatment

In this study, the high strength-ductility properties of wire-arc additive manufactured (WAAM) Al-Mg-Sc aluminum alloy were achieved by friction stir processing post-treatment (FSPPT) and high temperature aging treatment (HTAT). The FSPPT significantly refined the microstructure and eliminated porosity defects, which the average grain size was about 2.4 ± 0.2 μm in stirring zone (SZ). There was no obvious growth in grain size after HTAT and the average grain size was about 2.7 ± 0.4 μm in SZ. Many fine secondary Al3(Sc,Zr) phases were precipitated. Compared to WAAM sample, the average ultimate tensile strength (UTS), yield strength (YS) and elongation (EL) of FSPPT + HTAT sample increased by 57.9%, 54.7% and 205.9%, respectively.

Microstructure and dynamic mechanical behavior of wire-arc additive manufactured high-strength steel

The working environment of high-strength steel components produced by wire-arc additive manufacturing (WAAM) often faced challenges of explosion and impact, but the microstructure evolution and dynamic mechanical behavior of WAAM produced high-strength steel were still unclear. In this study, low alloy high-strength steel （HSS） components were produced by WAAM. Split Hopkinson Pressure Bar (SHPB) tests at different strain rates were carried out on WAAM-HSS, and the specimens before and after dynamic compression were characterized by techniques such as SEM, EDS, XRD, EBSD, etc. The results showed that： The as-built WAAM-HSS plate mainly consists of five typical structures: lath martensite (ML), acicular ferrite (AF), polygonal ferrite (PF), martensite-austenite (M-A), and precipitated phase δ. The central area of the precipitated phase is Si and Mn, and the C element is mainly distributed in the surrounding area of the precipitated phase. Under dynamic compression, the as-built WAAM-HSS exhibited obvious yield phenomenon, and the yield stress increased with the increase of strain rate. The yield-strengthening mechanism is mainly contributed by grain refinement strengthening mechanism and dislocation density strengthening mechanism. Under dynamic compression, the martensite transformation occurred in the WAAM-HSS. The deformation mechanism is dislocation slip and twinning, which compete with each other. Dislocation slip deformation is dominant at low strain rate and twinning deformation is more dominant at high strain rate.

Effect of Heat Input on the Wire-Arc Additive Manufactured Steel Structures

Wire arc additive manufacturing (WAAM) is one of the less-explored metal 3D printing technologies that hold up a huge potential for large-scale product manufacturing across multiple industries. The low-cost AM uses arc energy as a heat source and metallic wire as a feedstock material. The process is sustainable and supports green manufacturing. However, the major challenge associated with the WAAM is that heat management leads to the development of residual stress causing dimensional inaccuracy and poor surface finish. Therefore, four-layer straight wall structures are fabricated by depositing material layer-upon-layer with nine distinct heat inputs (HI). The prime focus of the work is to study the effect of HI on the dimensional accuracy and the quality of deposited structures. The influence of deposition height on the surface topography is investigated. Furthermore, the effect of HI on the mechanical properties of the WAAM-printed thin wall is examined. The results show that with increase in the number of depositing layers, surface roughness values get increased under the similar process parameter used for the part fabrication. Therefore, it is recommended to re-adjust the process parameter after certain layers of deposition with proper monitoring of the thermal condition in the deposited layers while fabricating medium to large WAAM components. The outcomes from the studies show that increases in the HI while fabricating the WAAM component deteriorates the surface quality of the deposited layer and are responsible for reducing the mechanical properties of the WAAM-printed component.

Hot oxidation and corrosion behaviour of boiler steel fabricated by wire arc additive manufacturing

Boiler Steels undergo severe degradation in corrosion resistance due to oxide scale formation at elevated temperatures. In this study, the comparative hot oxidation and hot corrosion resistance of wire arc additive manufactured SS 308L (WAAM 308L) was examined in hot air and Na2SO4–60% V2O5 molten salt environments at 700 °C. The corrosion resistance at elevated temperature was analysed using thermo-kinetic curves, corrosion products, and morphology of the oxides. The hot oxidation kinetics revealed that WAAM processed SS 308L specimens has excellent resistance and the weight gain reached 3.10 mg/cm2 with thinner oxide scale formation. Hot corrosion kinetics of WAAM processed SS 308L specimens highlighted the higher weight gain (37.0 mg/cm2) in molten salt environment and is attributed to the acceleration of oxide scale formation by the salts at elevated temperatures. Also, the development of Ni3V2O8 and Fe2O3 along with the depletion of Cr2O3 significantly influenced the corrosion resistance at elevated temperatures. The findings of this study reveal the potential of WAAM to produce customized parts for high-temperature applications.

Achieving fully equiaxed grain microstructure and isotropic mechanical properties in wire arc additive-manufactured Mg-Y-Nd-Zr alloys

The thin-wall Mg-3.82Y-2.46Nd-0.56Zr (WE43) alloy component was fabricated using cold metal transfer-based wire arc additive manufacturing technology (WAAM-CMT) and the way in which microstructure evolution influences the corresponding mechanical properties in different height zones was studied. The thin-wall WE43 alloy component was mostly composed of fully equiaxed grains that had low texture strength. As a result of the layer-by-layer deposition, its microstructure exhibited obvious layer characteristics, mainly including melt pools (MP) with coarse equiaxed grains and melt pool boundaries (MPBs) with fine equiaxed grains. The grain size of the thin wall in the building direction decreased from 25.3 ± 1.2 µm in the bottom zones to 22.3 ± 0.7 µm in the top zones, whereas the content of the second phase increased. No obvious anisotropy was observed in the mechanical properties of the thin wall. The top zone specimens were found to have the best mechanical properties with ultimate tensile strength (UTS) of 233 MPa, yield strength (YS) of 153 MPa and elongation (EL) of 10.4%. In comparison to the bottom zone specimens, improvement in the mechanical properties of the top zone specimens resulted from secondary phase strengthening and grain boundary strengthening.

Post-processing of wire arc additive manufactured Inconel-625 thin structure by electro-discharge machining with TLBO assistance

The lower fabricated shaped accuracy by wire-arc additive manufacturing (WAAM) consist a challenge to machine the thin features of hard surface. In this study, a non-conventional machining for thin Inconel-625 WAAM structure by Electro-discharge machining (EDM) is being proposed as an alternative post-processing technique. Effects and optimization of process parameters are examined by Taguchi analysis and a meta-heuristic technique of Teaching learning-based optimization (TLBO) algorithm. Multi-response optimization with the equal relative importance for material removal rate (MRR) and surface roughness (SR) is being performed and developed models were validated to be satisfactory under the considerable prediction errors.

Assessment of additive and subtractive sustainable manufacturing of Inconel 625

This study assesses the sustainable subtractive manufacturing of Wire Arc Additive Manufactured (WAAMed) Inconel 625 (IN625). Compared to other additive manufacturing techniques, WAAM is economically efficient and has a higher deposition rate. However, post-subtractive manufacturing operations are often required for additive manufactured (AMed) parts to make them ready for industrial applications. Drilling trials were conducted on AMed and wrought IN625 under three environments: dry, flood and cryogenic. Their machinability was evaluated in terms of cutting forces, torque, power consumption as well as surface roughness. Also, the surface morphology of drill tools, drilled holes and machined chips were analysed and compared. Results show that the cryogenic environment enhances tool life and surface integrity for drilling of WAAMed parts, whereas flood environment emerged as a better cooling/lubricating condition for machining wrought specimens.

Unraveling the failure mechanism of wire arc additive manufactured low carbon steel under tensile and high cycle fatigue loading

Wire arc additive manufacturing (WAAM) is one of the common additive manufacturing processes for efficiently building large components due to its high deposition rate and higher catchment efficiency with an easy and relatively simpler arrangement. However, WAAM components often observe defects that adversely affect some mechanical properties. The present work employs a two-camera digital image correlation (DIC)-based technique for simultaneous strain measurements on two mutually orthogonal surfaces to capture the strain accumulation due to defects and subsequent failure behavior under uniaxial tensile loading of WAAM deposited ER70S-6 low carbon steel samples. The elastic cyclic loading tests are also performed at different stress amplitudes, and their fracture surfaces are analyzed with scanning electron microscopy. Due to the weak interlayer consolidation, multiple delaminations and strain accumulation sites are observed. Propagation of delamination contributed towards the failure, and dimples as well as intergranular fractures are observed on failure surfaces. Premature failure with a reduced number of cycles to failure is observed during high cycle fatigue tests due to catastrophic fast failure in the neighborhood of the internal defects. While the fatigue crack initiation and propagation are distinctly observed on fracture surfaces, transition regions from fatigue fracture and fast fracture are mostly obscure.

Finite element simulation of residual stress of wire arc additive manufactured low alloy high strength steel component assisted by interlayer hammering

Residual stress is an important factor affecting structural deformation, which seriously reduces the dimensional accuracy, fatigue strength, and safety of structural parts. In this study, a coupled thermal-mechanical finite element model for wire arc additive manufacturing (WAAM) was established based on ABAQUS and Fortran subroutine and the accuracy of the simulation results was verified by experiments. The effects of hammering and hammering temperature on the residual stress in low alloy high strength (HSLA) steel built by the WAAM process were analyzed. The results showed that the effect of reducing the residual stress increased and then decreased with the hammer temperature in the hammer temperature range of this study. The optimal hammer temperature was found to be 800 °C. The maximum longitudinal, transverse, and Z-direction residual stress of the deposited wall after 800 °C interlayer hammering decreased by 20.7, 273.9, and 116.9 MPa, respectively.