*Article* **Additive Manufacturing of 17-4PH Alloy: Tailoring the Printing Orientation for Enhanced Aerospace Application Performance**

**Sandor Endre Kovacs 1, Tamas Miko 2, Enrico Troiani 3, Dionysios Markatos 4, Daniel Petho 2, Greta Gergely 2,\*, Laszlo Varga <sup>1</sup> and Zoltan Gacsi <sup>2</sup>**


**Abstract:** Additive manufacturing (AM) is one of the fastest-growing markets of our time. During its journey in the past 30 years, its key to success has been that it can easily produce extremely complex shapes and is not limited by tooling problems when a change in geometry is desired. This flexibility leads to possible solutions for creating lightweight structural elements while keeping the mechanical properties at a stable reserve factor value. In the aerospace industry, several kinds of structural elements for fuselage and wing parts are made from different kinds of steel alloys, such as 17-4PH stainless steel, which are usually milled from a block material made using conventional processing (CP) methods. However, these approaches are limited when a relatively small element must withstand greater forces that can occur during flight. AM can bridge this problem with a new perspective, mainly using thin walls and complex shapes while maintaining the ideal sizes. The downside of the elements made using AM is that the quality of the final product is highly dependent on the build/printing orientation, an issue extensively studied and addressed by researchers in the field. During flight, some components may experience forces that predominantly act in a single direction. With this in mind, we created samples with the desired orientation to maximize material properties in a specific direction. The goal of this study was to demonstrate that an additively manufactured part, produced using laser powder bed fusion (LPBF), with a desired build orientation has exceptional properties compared to parts produced via conventional methods. To assess the impact of the build orientation on the LPBF parts' properties, one-dimensional tensile and dynamic fracture toughness tests were deployed.

**Keywords:** additive manufacturing; 17-4PH stainless steel; 3D printing; laser powder bed fusion; printing orientation
