Droplet transfer behavior in bypass-coupled wire arc additive manufacturing

Energy characteristics of droplet transfer in wire-arc additive manufacturing based on the analysis of arc signals

Electric current evaluation for process monitoring in electron beam directed energy deposition

Laser-MIG hybrid welding of 316L stainless steel was carried out to investigate influence of welding process parameters, i.e., laser power (P), welding current (I), distance between laser and arc (D), and welding speed (V) on arc characteristics, droplet transfer, and weld quality. Arc characteristics and droplet transfer behavior were investigated using high-speed imaging technology. Microstructures of the joint were observed by optical microscope, and microhardness was measured by microhardness tester. The results showed that the maximum deviation angle of the arc from the wire axis decreases with the increasing laser power. Welding current played a dominant role in arc length and droplet transfer mode. Optimal weld with no spatters and humps was obtained when P = 3 kW, I = 140 A, D = 3 mm, and V = 1.2 m/min. Microstructures in the weld zone mainly consist of columnar and equiaxed dendrites. Microhardness decreased toward the center of the weld zone, increased toward the WZ boundary, and decreased sharply at the heat-affected zone (HAZ).

Influence of pulsed arc on the metal droplet deposited by projected transfer mode in wire-arc additive manufacturing

Influence of Ship-based Vibration on Characteristics of Arc and Droplet and Morphology in Wire Arc Additive Manufacturing

Additive manufacturing has the potential to revolutionize industrial hardware and unlock efficiency gains through the fabrication of geometries and architectures not possible by conventional processing. Wire Arc Additive manufacturing (WAAM) process is a class of directed energy deposition process enabling higher build rate and allowing custom wire feedstock allowing spatial variation of microstructure. The larger spot size and lower speed creates a larger melt pool, reducing residual stress and often time creating directional/columnar microstructure for Ni-superalloy. The use of flexible platform provides freedom in deposition strategy, which can accommodate complex substrates, including feature addition onto existing structures, non-flat layers, and repair methods. However, the certification of the final component needs to match the strength requirement. Hence, the quality of the component produced is stringently monitored to avoid buildup of residual stress, cracks, porosity and to reduce detrimental segregated phases commonly observed during alloy solidification. Simulation plays a huge role in predicting the melt pool dimension and can be used to optimize the process parameter. Similar development is also required to perform physics-based modeling of microstructural development in WAAM that can predict the microstructural features during solidification and can be used to optimize the process more effectively. To move toward this goal, Raytheon Technologies Research Center together with Siemens worked to create a set of computational tools to control the process parameters, enable on-line measurements and acquisition with feedback to the optimized process parameters, and eventually track material evolution through each step of the additive process. Computational fluid dynamics is used for accurate prediction and calibration of the thermal field during WAAM process. and phase field models for microstructure evolution as a function of processing parameters to establish a connection between additive parameters and the final microstructure. Here we report cellular automata (CA) model development to predict the dendritic microstructure evolution with surface and bulk nuclei for single track and multiple layers. The CA model was developed to account for secondary element addition and predict segregation, local melting, and latent heat release as well as prediction of Euler angles from orientation information and validated against experiments. This framework was utilized to tailor spatially-varying composition in a part by appropriately controlling the microstructure evolution during the additive process. Functionally graded Haynes 282 alloy with high Cr content at the surface was tested for oxidation and mechanical properties. An advanced physics-based reaction-diffusion model predicting the simultaneous creation of chromium oxide and alumina is developed and validated to extend life expectancy of the WAAM manufactured high temperature part. A machine-learning data-driven framework establishing the process-structure relationship from a dataset of real microstructure images and corresponding process history data has been developed and implemented in the NX Siemens design system. The digital twin configuration along with the tool path generation enabled prediction of WAAM component buildup time and the techno-economic analysis provided a favorable option for all 4 cases with 15-40% cost reduction.

Wire Arc Additive Manufacturing (WAAM) is a metallic additive manufacturing process based on the fusion of metallic wire using an electric arc as a heat source. The challenge associated with WAAM is heat management and understanding bead geometry. The printing process involves high temperatures, which results in the build-up of residual stresses can often cause deformations in a component. All of the process variables, such as torch speed (TS), wire feed speed (WFS), idle time, combine to produce the geometry of the deposit bead that results in the desired component shape. So, determining a method for choosing a good combined parameter process is very important to obtain a high-quality part. This article presents a study on how to use the WAAM process to produce a complexity part of aluminium alloys. The step of the determination process parameter is concentrated to develop in this study. An experimental design is determined to study the influence between the process parameters, for example, WFS, TS, high layer, length of bead. Different samples are made using the Yaskawa robot, using the classic CMT (Cold Metal Transfer) as a manufacturing method, using zigzag filling as a manufacturing strategy with the same WFS and same idle times and different TS, different bead lengths. A new manufacturing method using the zigzag filling strategy is proposed by adding an important step in determining the process parameters. The results indicate that the length of the bead has a significant impact on another parameter of the process.

Surface roughness is a critical design parameter that has been shown to have a major impact on qualities like wear resistance and fatigue strength. Wire arc additive manufacturing (WAAM) is a metal additive manufacturing technology that is gaining popularity in the aerospace and automotive industries due to its use in the maintenance and repair of key high-cost goods. As a result, in today’s manufacturing industry, surface roughness modeling and prediction of printed components are crucial. The purpose of this research is to develop an optimal neuro-fuzzy system that can represent surface roughness in the WAAM process using a set of input process variables such as welding speed, wire feed speed, and overlap ratio. During hybrid learning of the first-order Sugeno fuzzy system, three distinct membership functions, such as trapezoidal, bell, and Gaussian-shaped, were used to examine the accuracy in prediction of surface roughness by three membership functions. The experimental data were compared to the anticipated surface roughness values produced from the proposed adaptive neuro-fuzzy expert system. According to the results of the comparison research, the suggested technique may provide an ideal database and rule foundation for predicting deposition characteristics in the metal additive manufacturing process.KeywordsMetal additive manufacturingWire arc additive manufacturingAdaptive neuro-fuzzy systemSurface roughness

To guarantee good quality of butt laser welding with filler wire, a sensor, that is used to detect gap width and seam tracking and a wire feeding system have been developed in this paper. The sensor contains a laser diode as assistant optical source and a photoelectric cell as receiving component. A step-motor drives the sensor transversally scanning above the work piece so as to detect the gap width as basis of adjusting welding parameters and the center position of the butt gap as benchmark of seam tracking. A computer calculates the required wire feeding speed and welding speed according to the gap width and transfers these values to wire feeding system and speed adjusting system. In the welding of 2mm-thick low carbon steel sheet, the wire feeding speed and welding speed are respectively changed according to gap width detection and weld bead appearance is analyzed. The results show that it is better to adjust wire feeding speed for narrower gap and adjust welding speed for wider gap. According to the detected signal of the sensor, the appearance quality of the total weld could be guaranteed by choosing wire feeding speed or welding speed as the control variable for different gap widths.

A defect detection system for wire arc additive manufacturing using incremental learning

In this paper, the droplet transfer mode during in-situ synthesis of NiTi alloys by dual-wire electron beam additive manufacturing by pure Ni and Ti wires was comprehensively studied. This work shows that the droplet transfer was jointly determined by the droplet transfer distance together with spatial position between two wires and electron beam. By reasonable control of the above factors, an ideal stable continuous liquid bridge transfer mode could be achieved. In this mode, Ni wire and Ti wire could be melted together and form a shared molten pool, which avoids the occurrence of spatter and guarantee the credibility of wire fed amount. Results show that NiTi alloys in-situ synthesized by liquid bridge transfer mode could obtain NiTi alloys with good forming quality and typical phase transformation behavior.

Objectives: Fabrication of a cylinder-shaped High-Strength Low Alloyed steel wall component through wire (metal cored) arc additive manufacturing and assess the homogeneity and integrity of the built component. Method: Mechanical testing and microstructural characterizations such as optical microscopy, scanning electron microscopy and electron backscattered diffraction techniques were performed at distinct regions (namely, bottom and top). Findings: The conducted tensile test at the bottom area recorded a tensile strength of 864 MPa, which is 5.9 % higher than the top region but with a lower total elongation. The microhardness study revealed that the average hardness at the bottom region was 266 HV0.5, while the top region was 241 HV0.5. The microstructural analysis conducted in both areas indicates that the bottom region exhibits better hardness and strength due to the presence of a high value of geometrically necessary dislocations, High-Angle Grain Boundaries and increased grains with reduced size. However, the built component proves to have better homogeneity with marginal deviations in the properties estimated. Novelty: Solid wire was used as a predominant filler material for the Wire-Arc Additive Manufacturing (WAAM) process, which requires high heat input to melt the material. Hence, to reduce the heat input, metal-cored wire was used instead of solid wire for the Gas Metal Arc -WAAM process. Keywords: Gas metal arc welding, Metal cored wire, Mechanical properties, Direct energy deposition, Wire-arc additive manufacturing

Additive manufacturing is a very popular word in the present day as various researchers are focused on this field all around the world. Every new researcher coming to this field of additive manufacturing is busy in developing new methods and techniques to make it more versatile and efficient in terms of applicability. Wire arc additive manufacturing (WAAM) process, a new addition to the AM processes, is growing rapidly in the field of the metal additive manufacturing process because of its high deposition rate, low equipment cost compared to laser and electron beam, saving lead time, high BTF (buy-to-fly) ratio, no limit on part size, and many other advantages. In this study, a wire arc additive manufacturing system based on cold metal transfer gas metal arc welding technology was used to fabricate a solid block component with ER70S6 MS alloy welding wire. This study presents the investigation on anisotropy behavior of resulted microstructure and mechanical properties including tensile, impact, and hardness of the manufactured block component. The samples were taken along the parallel and perpendicular to the welding direction. The tensile properties of the samples were found almost uniform in both the directions with values of the ultimate tensile strength (UTS), yield strength (YS), and elongation (%E) found to be 510 ± 5 MPa, 373 ± 5 MPa, and 37% ± 2%, respectively. The average Vickers hardness values at 10 kg load in parallel and perpendicular directions were found around 80 and 72 kg/mm2. The impact toughness at −30℃ was found to be 148 and 170 J in the parallel and perpendicular direction. The toughness obtained is much higher than the required minimum impact strength of 80 J at the subzero temperature as per the AWS requirement for the used ER70S6 welding wire. The microstructure observed in welded samples is ferrite and bainite which consists inside and along the prior austenite grain boundaries. Mostly grains were elongated in the welding direction. From the present work, it is evident that the near-net-shape component fabricated with the WAAM process has quite acceptable mechanical properties without much effect of directionality.

The wire arc additive manufacturing (WAAM) process often begins printing on a substrate. In some cases, the substrate could act as a functional part of the WAAM-fabricated parts. In this work, ER70S-6 is directly deposited onto a 316L substrate using the WAAM process. Microstructural studies reveal good fusion and bonding at the interface. Due to the dilution of ER70S-6 and 316L, a gradient change in composition and microstructure was observed in the first six layers. The first layer (Fe-10Cr-5.5Ni-1Mo-1Mn) and the second layer (Fe-4Cr-2Ni-1Mn-0.5Mo) exhibit a bainite microstructure. Ferritic grains were observed from the third layer onwards. The microhardness is high at 336.9 ± 6.3 HV for the first layer and 302.7 ± 5.7 HV for the second layer. A decrease in microhardness was observed with the increase of the building layer until layer six. The yield strength is 356.6 MPa and the UTS is 502.3 MPa for the 316L/ER70S-6 bimetal joint. The digital image correlation (DIC) method is used to analyse the deformation behaviour. During the tensile test, the 316L substrate side yields first, and then the deformation shifts to the ER70S-6 side. This study also holds the potential for the development of novel alloys.

With the synergistic effect of laser and arc heat sources, laser-arc hybrid welding (LAHW) technology can improve welding speed and penetration depth, and enhance gap-bridging ability. This review describes the fundamental concepts and characteristics of droplet transfer behavior in LAHW. Emphasis was placed on the physical interaction between the laser and arc and the effect of the combined laser/arc heat sources on the welding process. However, the physical understanding of these multivariable and complex interactions is still evolving. Through numerous research findings and summary, it is found that there are several critical factors, including the laser-to-arc distance, heat source leading mode, shielding gas composition, and laser power, affecting the droplet transfer characteristics. This review critically interprets the latest development in the basic understanding of LAHW. It lays great stress on the coupling effect of laser and arc in droplet transfer dynamic process of LAHW, and offers a direction for the future study and progress of LAHW. Significant fields for future research are also confirmed.