Analysis of Anisotropy Effects Induced by Grain Orientation on the Cyclic Fatigue Behavior of Nickel-Based Alloys Produced by Selective Laser Melting and Comparison with Conventionally Machined Samples

Abstract

In recent years, additive manufacturing—especially the Selective Laser Melting (SLM) method—has emerged as a key technology for producing complex engineering components. One of its main challenges is the anisotropy of mechanical properties caused by grain orientation and the microstructure formed by rapid melting and solidification. This study aims to analyze the effect of such anisotropy on the cyclic fatigue behavior of nickel-based alloy Inconel 718 produced via SLM, compared with conventionally machined samples. Fatigue tests were conducted under tension–compression cyclic loading, and results were analyzed using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). The influence of build orientation angles (0°, 45°, and 90° relative to the loading axis) on fatigue life was evaluated. Results revealed significant anisotropy in the SLM specimens, with the 90° orientation showing the lowest fatigue life. Conversely, machined samples exhibited nearly isotropic behavior. Fracture analysis indicated that crack initiation predominantly occurred at grain boundaries and solidification defects. Overall, the findings highlight the necessity of controlling layer orientation and optimizing SLM parameters to reduce anisotropy and improve fatigue performance of engineering components.