Evaluation of the forming quality of Inconel 625 thin-walled parts manufactured via cold metal transfer additive manufacturing

Introduction: Wire arc additive manufacturing (WAAM) is a metal additive manufacturing technique that uses an arc source to melt metallic wires, depositing molten metal layer by layer to form parts. Controlling the forming quality of parts in the WAAM process poses significant challenges. This study evaluated the shape quality of thin walls produced via WAAM using Inconel 625 alloy. Additionally, the impacts of the welding speed (v) and linear heat input (LHI) on the geometric quality of the fabricated components are investigated. Methods: A cold metal transfer (CMT)-WAAM system was employed to construct thin-walled samples on low-carbon substrates. Three samples were fabricated at three different welding speeds (v = 35, 50, and 65 cm/min), while the other parameters remained constant. The samples were scanned via a Kreon Zypher II scanner, and their geometric properties, including average layer height (ALH), total wall width (TW), effective wall width (EW), and material deposition efficiency (DE), were measured via Geomagic Design X and AutoCAD software. Surface roughness parameters (e.g., Sz, Sa, and Sq) were assessed via Omnisurf 3D software. Results and Discussion: Increasing the welding speed from 35 to 65 cm/min led to reductions in all measured characteristics - ALH, TW, EW, and DE. For example, ALH decreases from 2.63 mm to 1.87 mm, TW decreases from 9.39 mm to 6.83 mm, and EW decreases from 5.90 mm to 4.30 mm. An increase in the LHI from 19.08 to 35.22 J/mm tends to inversely affect these geometric characteristics. Additionally, as v or LHI increases, Sz, Sa, and Sq initially decrease to a certain level before rising again. Conclusions: The results obtained from this study offer valuable insights into the relationship between processing and forming quality in the CMT-WAAM process for Inconel 625 thin-wall components. These insights provide a foundation for selecting optimal process parameters and providing informed recommendations for the CMT-WAAM process of Inconel 625 alloys.