Additive manufacturing using fine wire-based laser metal deposition

• Published in: Rapid prototyping journal 2020-04, Vol.26 (3), p.473-483
• Main Authors: Shaikh, Muhammad Omar, Chen, Ching-Chia, Chiang, Hua-Cheng, Chen, Ji-Rong, Chou, Yi-Chin, Kuo, Tsung-Yuan, Ameyama, Kei, Chuang, Cheng-Hsin
• Format: Article
• Language: English
• Subjects: 3-D printers; Accuracy; Additive manufacturing; Beads; Cross-sections; Crystal defects; Diameters; Electron backscatter diffraction; Feasibility; Grain growth; Laser beam welding; Laser deposition; Lasers; Microhardness; Monolayers; Morphology; Multilayers; Neodymium lasers; Process parameters; Pulse duration; Pulsed lasers; Rapid prototyping; Raw materials; Semiconductor lasers; Solidification; Stainless steel; Stainless steels; Substrates; Surface roughness; Tensile tests; Thickness; Wire; YAG lasers
• ISSN: 1355-2546; 1758-7670
• DOI: 10.1108/RPJ-04-2019-0110

Purpose Using 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/approach The 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. Findings An 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/value To the best of the