Improvement and characterization of additively manufactured EHLA3D surface properties

Abstract

In response to the industrial demand for sustainable manufacturing solutions and technologies capable of producing and repairing high-complexity, cost-effective, and high-performance components, Additive Manufacturing (AM) emerges as a viable method for a wide range of materials susceptible to welding, including iron, nickel, titanium, and aluminum-based alloys. Among the array of AM processes, the Extreme High-Speed Laser Material Deposition 3D (EHLA3D) process distinguishes itself as a variant of Laser Metal Deposition (LMD). This method offers notable advantages, such as the capacity to fabricate intricate 3D parts by depositing metal at exceptionally high speeds, in thin layers, and incorporating combinations of materials with low weldability or distinct melting points. Moreover, it results in a smaller thermally affected zone compared to conventional LMD, and due to its proximity to the final geometry (near-net-shape), it entails fewer operations to achieve a part whose geometric shape approaches the desired final design. Nevertheless, the EHLA3D process yields final parts with inherent surface roughness attributed to the process conditions. Melted metal powder particles are projected onto the surface, adhering and generating characteristic process roughness. The current study investigates laser remelting as a post-processing step to refine surface finish, concentrating on the roughness and waviness of surfaces with two primary characteristics: narrow wall side surfaces with rougher finishes and flat tops representing the upper part of a component with roughness and waviness due to the clustering of multiple adjacent weld beads. Various parameters for remelting were considered, including beam diameter (1 mm, 2 mm, and 3 mm), feed rate (2 m/min, 5 m/min, 10 m/min, 20 m/min, and 30 m/min), overlap distance (30%, 50%, and 80%), and laser power (ranging from 200 W to 2700 W). Measurements using a White Light Interferometer (WIM) were conducted both before and after the remelting process to compare initial and final roughness and waviness values. The study demonstrates that improvements of up to 95.08% in narrow wall side surfaces and up to 76.6% in flat top surfaces are achievable. While waviness reduction on wall surfaces reached 72.24%, waviness on flat tops showed no significant improvement, remaining stable throughout the process.