Metal Additive Manufacturing Conference - MAMC 2022

One of the main advantages of Additive Manufacturing (AM) processes such as Laser Powder Bed Fusion (L-PBF) is the possibility to manufacture complex near-net-shape components. Therefore, the L-PBF process is becoming increasingly important for the manufacturing and repair of gas turbine blades. Despite the great freedom in design, there are also limitations to the process. Manufacturing overhangs or bridging voids are some of the main challenges, as it is not possible to print into loose powder. In the conventional L-PBF process, overhangs with angles $\alpha_{crit}>45^{\circ}$ are supported by support structures, which are subsequently removed. Gas turbine blades feature voids for cooling, which have to be bridged in L-PBF. However, such cooling voids are closed in the upper area by the bottom of the squealer tip. Therefore, no support structures can be used, as subsequent removal is not possible. In this work, different concepts for bridging voids are developed for future application in gas turbine blade repair. For this purpose, a test geometry is derived from the tip area of a gas turbine blade as a reference. By changing the initial geometry of the reference body, different designs for bridging cavities are developed. For the design, the requirements of the L-PBF process are analyzed and considered. Subsequently, these different designs are manufactured by L-PBF. The different approaches are compared with respect to the increase in mass relative to the reference body. In addition, the specimens are visually inspected for warpage, shrinkage and imperfections by overheating. From the seven developed bridging concepts, one concept is selected based on low weight increment, warpage and shrinkage and allows for a 20$\,$mm void to be bridged.