Layer-level fabrication of continuous functionally graded materials (cFGMs) via Powder Bed Fusion – Laser Beam technology

Multi-material fabrication of metals through Additive Manufacturing (AM) processes is attracting more and more attention in recent years. This work presents a novel methodology that enables the fabrication of continuous functionally graded materials (cFGMs) at the layer level using Powder Bed Fusion – Laser Beam (PBF-LB) technology. This has been achieved by designing and building a customized powder separation system that can be easily installed on a currently operating PBF-LB system with a blade/roller-based powder spreading technique (extremely limited for layer-level multi-material fabrication). This technique overcomes one of the main drawbacks of AM multi-material fabrication by properly joining materials with very different mechanical properties and low compatibility, thus extending the productive capacity of this technology. Two steels, AISI 316 L and 18 Ni Maraging 300, with different physical, chemical and mechanical properties, were used to study the applicability and verify the proposed methodology. A high-resolution optical system was used to monitor, layer by layer, the different laser-matter interactions given by the different materials and thus the presence of a graded transition zone between them. Results in terms of statical mechanical properties, microstructure, chemical analysis and optical monitoring showed that the proposed solution is reliable and cost-effective, paving the way for future applications. • Layer-level production of continuous functionally graded materials via PBF-LB system. • Optical monitoring confirmed the presence of a graded transition zone between materials. • Optical microscope and EBSD analysis showed the presence of a fine dual-phase microstructure in the transition area. • EDS chemical analysis & mechanical tests showed the ductile behavior and good metallurgical bonding between two materials.