Wire-feed Additive Manufacturing Research Articles

Controlling the porosity using exponential decay heat input regimes during electron beam wire-feed additive manufacturing of Al-Mg alloy

Electron beam wire-feed additive manufacturing is given less attention in research community compared with other additive manufacturing methods, despite it allows higher deposition rate and less porosity. However, both gas and shrinking porosity are still met even with this method especially if applied to light alloys. The excess heat input may be the reason for evaporation of volatile metals, and forming the gas pores especially in the top layers of the built sample where cooling rate is reduced. Therefore, exponential decay heat input was used to grow AA5356 samples. Microstructural and mechanical characterization of the samples obtained at mean low, medium, and high heat input levels was carried out. An optimal heat input gradient was determined which allowed growing a defect-free metal in the bottom part of the sample and forcing out the shrinkage cavities to the top part. Shrinkage and gas pore structure formation was analyzed as a function of the heat input gradient and along the building direction. Gas pores resulted at two higher heat input regimes as a result of evaporation of magnesium as supported by the results of EDS and XRD. Tensile test showed the ultimate strength of the defect-free part equal to that of the base AA5356.

An in-situ monitoring system for electron beam wire-feed additive manufacturing

Wire-feed additive manufacturing (AM) is a promising method for fabricating large metal components with complex geometry. Plenty of studies proved that wire transition status has critical influence on the forming quality in wire-feed AM process. It is important to develop a high adaptive system for in-situ monitoring wire transition status, due to common methods such as CCD monitoring fail in smoky, high temperature and vacuum environment. In this paper, in order to overcome this problem, an in-situ monitoring system based on the electromagnetic principle was firstly designed and fabricated. The experiments indicated that triple common states of wire transition can be distinguished with the system. The results showed that 0.5–mm spatial resolution and 0.4-s response time satisfy the demand for monitoring in AM process. In addition, the system adaptability for complex situation was validated and enhances performance with the lifting voltage. In practical, the monitoring system successfully worked over a long period in the high temperature, vacuum environment during the electron beam AM process. This study provided a new design for process monitoring, which is feasible and valuable for developing AM technology.

State of art on wire feed additive manufacturing of Ti-6Al-4V alloy

Titanium alloys have high strength to low weight ratio, good creep resistance and high temperature strength properties. Based on these properties, Ti alloys are used as a ‘workhorse’ material in the aerospace industry such as engine blades, landing gear assemblies, large structural parts, airframe and drums etc. Traditional fabrication methods of Ti alloy are expensive and inferior in their mechanical properties. Due to continuous development in science and technology, many researchers have been attracted towards Wire Feed Additive Manufacturing (WFAM) for the fabrication of titanium and its alloys. WFAM has set a new trend by accomplishing the production demand of components from medium to large scale with moderate complexity. This additive manufacturing technology generally employes for high material utilization and higher deposition. This state of art highlights the remarkable achievements of WFAM processes followed by their effect of process parameters, microstructural changes, residual stresses and mechanical properties of Ti-6Al-4V alloy.

Additive manufacturing using fine wire-based laser metal deposition

PurposeUsing wire as feedstock has several advantages for additive manufacturing (AM) of metal components, which include high deposition rates, efficient material use and low material costs. While the feasibility of wire-feed AM has been demonstrated, the accuracy and surface finish of the produced parts is generally lower than those obtained using powder-bed/-feed AM. The purpose of this study was to develop and investigate the feasibility of a fine wire-based laser metal deposition (FW-LMD) process for producing high-precision metal components with improved resolution, dimensional accuracy and surface finish.Design/methodology/approachThe proposed FW-LMD AM process uses a fine stainless steel wire with a diameter of 100 µm as the additive material and a pulsed Nd:YAG laser as the heat source. The pulsed laser beam generates a melt pool on the substrate into which the fine wire is fed, and upon moving the X–Y stage, a single-pass weld bead is created during solidification that can be laterally and vertically stacked to create a 3D metal component. Process parameters including laser power, pulse duration and stage speed were optimized for the single-pass weld bead. The effect of lateral overlap was studied to ensure low surface roughness of the first layer onto which subsequent layers can be deposited. Multi-layer deposition was also performed and the resulting cross-sectional morphology, microhardness, phase formation, grain growth and tensile strength have been investigated.FindingsAn optimized lateral overlap of about 60-70% results in an average surface roughness of 8-16 µm along all printed directions of the X–Y stage. The single-layer thickness and dimensional accuracy of the proposed FW-LMD process was about 40-80 µm and ±30 µm, respectively. A dense cross-sectional morphology was observed for the multilayer stacking without any visible voids, pores or defects present between the layers. X-ray diffraction confirmed a majority austenite phase with small ferrite phase formation that occurs at the junction of the vertically stacked beads, as confirmed by the electron backscatter diffraction (EBSD) analysis. Tensile tests were performed and an ultimate tensile strength of about 700-750 MPa was observed for all samples. Furthermore, multilayer printing of different shapes with improved surface finish and thin-walled and inclined metal structures with a minimum achievable resolution of about 500 µm was presented.Originality/valueTo the best of the authors’ knowledge, this is the first study to report a directed energy deposition process using a fine metal wire with a diameter of 100 µm and can be a possible solution to improving surface finish and reducing the “stair-stepping” effect that is generally observed for wires with a larger diameter. The AM process proposed in this study can be an attractive alternative for 3D printing of high-precision metal components and can find application for rapid prototyping in a range of industries such as medical and automotive, among others.

Temperature and Microstructure Evolution in Gas Tungsten Arc Welding Wire Feed Additive Manufacturing of Ti-6Al-4V.

In the present study, the gas tungsten arc welding wire feed additive manufacturing process is simulated and its final microstructure predicted by microstructural modelling, which is validated by microstructural characterization. The Finite Element Method is used to solve the temperature field and microstructural evolution during a gas tungsten arc welding wire feed additive manufacturing process. The microstructure of titanium alloy Ti-6Al-4V is computed based on the temperature evolution in a density-based approach and coupled to a model that predicts the thickness of the α lath morphology. The work presented herein includes the first coupling of the process simulation and microstructural modelling, which have been studied separately in previous work by the authors. In addition, the results from simulations are presented and validated with qualitative and quantitative microstructural analyses. The coupling of the process simulation and microstructural modeling indicate promising results, since the microstructural analysis shows good agreement with the predicted alpha lath size.

Obtaining the bimetallic composition by the electron beam freeform fabrication

This paper is devoted to obtaining the multimaterials using the electron-beam wire-feed additive manufacturing technology. The sample of titanium alloy Ti-6Al-4V and stainless steel 321 composition was obtained. It was found that steel and Ti-alloy form a transitional intermediate layer between themselves. The Ti-alloy layer does not undergo major changes, while the layer of stainless steel undergoes significant cracking.

Wire Arc Additive Manufacturing of Mn4Ni2CrMo Steel: Comparison of Mechanical and Metallographic Properties of PAW and GMAW

Wire arc additive manufacturing, WAAM, is a popular wire-feed additive manufacturing technology that creates components through the deposition of material layer-by-layer. WAAM has become a promising alternative to conventional machining due to its high deposition rate, environmental friendliness and cost competitiveness. In this research work, a comparison is made between two different WAAM technologies, GMAW (gas metal arc welding) and PAW (plasma arc welding). Comparative between processes is centered in the main variations while manufacturing Mn4Ni2CrMo steel walls concerning geometry and process parameters maintaining the same deposition ratio as well as the mechanical and metallographic properties obtained in the walls with both processes, in which the applied energy is significantly different. This study shows that acceptable mechanical characteristics are obtained in both processes compared to the corresponding forging standard for the tested material, values are 23% higher for UTS and 56% for elongation in vertical direction in the PAW process compared to GMAW (no differences in UTS and elongation results for horizontal direction and in Charpy for both directions) and without significant directional effects of the additive manufacturing technology used.

Obtaining uniform deposition with variable wire feeding direction during wire-feed additive manufacturing

ABSTRACTWire-feed additive manufacturing is cost competitive and efficient in producing large and complex components in aerospace applications. However, for the additive manufacturing technologies with lateral wire feeding, including laser wire additive manufacturing, electron beam freeform fabrication, plasma arc welding, and gas tungsten arc welding, it is difficult to obtain uniform deposit due to the variable wire feeding direction. In this work, high-angle wire feeding method is proposed to obtain uniform deposit in gas tungsten arc welding-based additive manufacturing. The results illustrate that low wire feeding angle (30°–50°) causes the deposition to break at the back feeding, meanwhile too high wire feeding angle (70°) leads to many littered droplets on one side of the deposition at the condition of side feeding. A uniform deposition can be obtained at the optimal wire feeding angle of 60° in any wire feeding direction, and the reasons have been discussed based on the temperature distribution characteristics of the arc and molten pool. Furthermore, the deposition layers exhibit similar columnar prior β grains, basketweave microstructure, and tensile properties from different wire feeding directions.

Effect of laser scanning and powder addition on microstructure and mechanical properties for hot-wire-feed laser additive manufacturing

Powder is generally used as a filler material for laser additive manufacturing of metal components, but it is unsatisfactory for aspects such as deposition efficiency, material utilization ratio, environment adaptability, and powder milling cost. Wire-feed additive manufacturing of metal components has attracted more and more attention. However, the poor melting stability of filler wires hampers its industrial application, let alone other unbeneficial factors like weak material flexibility, low dimension accuracy, and low energy efficiency. The benefits of hot wires have been reported by preheating filler wires. However, it is still difficult to get equivalent properties after additive manufacturing without bulk heat treatment. This work aims to establish a hot-wire-feed laser additive manufacturing technology to repair metal components with high efficiency and quality. A martensite stainless steel wire was used as a filler material. The microstructure and mechanical properties of the deposited layers were investigated. The heterogeneous distribution of the microstructure was observed. The overall mechanical properties of the as-cladded layer deteriorated. Laser scanning during idling time between layers was used to temper the deposited metal and to obtain a homogeneous microstructure without bulk heat treatment. The effect of laser scanning parameters on the thermal history and microstructure evolution was discussed. With the addition of feeding TiC nanopowder, the chemical composition of deposited metals was adjusted further. The tensile strength of the clad layer got close to that of the substrate. The ductility and impact toughness of the clad layer are even better than those of the substrate.

Development of a cold wire-feed additive layer manufacturing system using shaped metal deposition method

Shaped metal deposition (SMD) method would be an alternative way to traditional manufacturing methods, especially for complex featured and large scale solid parts and it is particularly used for aerospace structural components, manufacturing and repairing of die/molds and middle-sized dense parts. This method is implemented by depositing continuous cold or hot-water melted via welding arc plasma heat. This paper presents the designing, constructing, and controlling of an additive manufacturing system using TIG plus wire based Shaped metal deposition (TW-SMD) method. The aim of the current study is to design and develop an integrated system which is able to reduce time consuming and boring task of deposition process. The developed additive system is capable of producing near net shaped components of sizes not exceed 400 mm in 3 directions directly from CAD drawing. The results showed that the developed system succeeded to produce near net geometries and error-free depositions for various features of SS308LSi components. Additionally, workshop tests have been conducted in order to verify the capability and reliability of the developed AM system.

Design and integration of WAAM technology and in situ monitoring system in a gantry machine

Wire arc additive manufacturing, WAAM, is a popular wire-feed additive manufacturing technology that creates components through the deposition of material layer-by-layer. WAAM has become a promising alternative to conventional machining due to its high deposition rate, environmental friendliness and cost-competitiveness. In this research work, an adaptation of a gantry machine with in-situ monitoring and a control system has been carried out, in order to expose the ability of the WAAM technology to fabricate complex-shaped parts. The retrofitting of the machine has been done in several layers called respectively hardware, control and software layers. For the validation of the implemented system, a stainless steel 316L demonstrator has been manufactured, and the required stages have been employed, including part design (CAD), process parameters selection, tool-path definition (CAM) and part manufacturing. This study has shown the feasibility of the adapted machine for additive manufacturing as a controlled process.

Adaptive path planning for wire-feed additive manufacturing using medial axis transformation

Wire-feed additive manufacturing technologies have made it possible to significantly reduce material waste and energy consumption for fabricating large aerospace metal components that feature high buy-to-fly ratios. This paper presents an innovative path planning strategy using medial axis transformation for the wire-feed additive manufacturing process. The proposed path planning strategy is able to improve geometrical accuracy and produce void-free deposition by continuously altering the deposition width of the wire-feed process to accommodate the component geometry, while simultaneously minimising the number of interruptions to the deposition process at the component boundary. As a result, both buy-to-fly ratio and energy consumption are improved through reducing material waste. The algorithm for generating the adaptive path is described and validated through application to various typical geometries. Buy-to-fly ratios are calculated for a number of thin-walled complex structures. Savings of more than 27% in material usage are achieved using adaptive path planning, when compared with non-adaptive methods. The proposed method is tested experimentally through deposition of two metal components. The results demonstrate that the adaptive strategy is capable of generating void-free deposition with improved accuracy at the component boundary using the wire-feed additive manufacturing process.

Wire-feed additive manufacturing of metal components: technologies, developments and future interests

Wire-feed additive manufacturing (AM) is a promising alternative to traditional subtractive manufacturing for fabricating large expensive metal components with complex geometry. The current research focus on wire-feed AM is trying to produce complex-shaped functional metal components with good geometry accuracy, surface finish and material property to meet the demanding requirements from aerospace, automotive and rapid tooling industry. Wire-feed AM processes generally involve high residual stresses and distortions due to the excessive heat input and high deposition rate. The influences of process conditions, such as energy input, wire-feed rate, welding speed, deposition pattern and deposition sequences, etc., on thermal history and resultant residual stresses of AM-processed components needs to be further understood. In addition, poor accuracy and surface finish of the process limit the applications of wire-feed AM technology. In this paper, after an introduction of various wire-feed AM technologies and its characteristics, an in depth review of various process aspects of wire-feed AM, including quality and accuracy of wire-feed AM processed components, will be presented. The overall objective is to identify the current challenges for wire-feed AM as well as point out the future research direction.

Integrated control of solidification microstructure and melt pool dimensions in electron beam wire feed additive manufacturing of Ti-6Al-4V

The ability to deposit a consistent and predictable solidification microstructure can greatly accelerate additive manufacturing (AM) process qualification. Process mapping is an approach that represents process outcomes in terms of process variables. In this work, a solidification microstructure process map was developed using finite element analysis for deposition of single beads of Ti-6Al-4V via electron beam wire feed AM processes. Process variable combinations yielding constant beta grain size and morphology were identified. Comparison with a previously developed process map for melt pool geometry shows that maintaining a constant melt pool cross sectional area will also yield a constant grain size. Additionally, the grain morphology boundaries are similar to curves of constant melt pool aspect ratio. Experimental results support the numerical predictions and identify a proportional size scaling between beta grain widths and melt pool widths. Results further demonstrate that in situ indirect control of solidification microstructure is possible through direct melt pool dimension control.

Morphology, microstructure, and hardness of titanium (Ti-6Al-4V) blocks deposited by wire-feed additive layer manufacturing (ALM)

Abstract Additive layer manufacturing offers a potential for time and cost savings, especially for aerospace components made from costly titanium alloys. In this paper, the morphology, microstructure, chemical composition, and hardness of additive manufactured Ti-6Al-4V blocks are investigated and discussed. Blocks (7 beads wide, 7 layers high) were deposited using Ti-6Al-4V wire and a Nd:YAG laser. Two different sets of parameters are used and three different post heat treatment conditions (as-built, 600 °C/4 h, 1200 °C/2 h) are investigated. The experiments reveal elementary properties of additive manufactured Ti-6Al-4V material in correlation to process parameters and heat treatments, which are discussed comprehensively.