Optimizing mechanical performance of LPBF Inconel 718 for turbo-engine applications though tailored heat treatment and process parameter strategies

Abstract

Additive manufacturing (AM) with laser-based technologies such as for instance Laser Powder Bed Fusion (LPBF) offers the possibility to produce structurally complex components rapidly and cost-effectively while maintaining a high quality. However, for demanding aerospace applications such as gas turbine components, ensuring an optimal material performance requires a thorough understanding of the relationship between the manufacturing process, the thermomechanical treatments, the microstructure, and the resulting mechanical properties. This study focuses on LPBF of Inconel 718 (IN718), a nickel-based superalloy widely used in aerospace applications due to its good high-temperature properties. While IN718 has a lower maximum temperature limit for applications (~ 650 °C) compared to newer alloys more recently developed for use in AM, it is already a well-understood, validated and easy-to-process choice with a potential that has not yet been fully exploited. Different heat treatment strategies including solutioning, double aging, and hot isostatic pressing were applied to LPBF-manufactured IN718 to assess their impact on phase composition, microstructure, and mechanical performance. Synchrotron high-energy diffraction analysis was used to analyze phase evolution, and mechanical properties were tested with focus on fatigue on specimens fabricated at build orientations 0°, 45°, and 90° relative to the load axis in the mechanical tests. The findings reveal a strong correlation between the process parameters, post-processing methods, microstructure and texture, phase composition, and fatigue strength. The results provide valuable insights for defining tailored process chains aiming at customized and improved material performance in specific aerospace applications.