The paper aims to examine the effect of different strain rates on a mechanical behavior and structure of additively manufactured Inconel 718. The material was prepared by the powder bed fusion method, which is commonly employed for high-performance components subjected to both high static and dynamic loading. To analyze the material’s behavior at various strain rates, a conventional hydraulic testing machine and a split hopkinson pressure bar apparatus were utilized. Additionally, the effect of these conditions on mechanical properties and microstructure was investigated. Results of compressive tests revealed a positive strain rate sensitivity of the material. Furthermore, the microhardness exhibited an increase by 33.9% in the horizontal direction after deformation caused by 2·10^–2 strain rate and 35.8% in the vertical direction, respectively. Additionally, the average grain size decreased by 43.3%, and the high-angle grain boundaries decreased by 5.4% in the horizontal direction after the excessive plastic deformation at the strain rate of 1.8·10³ s^-1. Scanning electron microscopy images showed that the as-built structure predominantly consisted of Laves phases in a long strip shape, while the structure after dynamic testing featured a granular shape. Transmission electron microscopy analysis of a sample tested at strain rate of 0.002 s^-1 revealed finely developed grains within the structure, many of which contained a dislocation substructure. This study’s novelty and robustness lie in its significant contribution to practical industrial energy applications, in which parts are exposed to dynamic load such as gas turbines.

This paper deals with a study of additively manufactured (by the Selective Laser Melting, SLM, method) and conventionally produced AISI 316L stainless steel and their comparison. With the intention to enhance the performance of the workpieces, each material was post-processed via hot rotary swaging under a temperature of 900 °C. The samples of each particular material were analysed regarding porosity, microhardness, high cycle fatigue, and microstructure. The obtained data has shown a significant reduction in the residual porosity and the microhardness increase to 310 HV in the sample after the hot rotary swaging. Based on the acquired data, the sample produced via SLM and post-processed by hot rotary swaging featured higher fatigue resistance compared to conventionally produced samples where the stress was set to 540 MPa. The structure of the printed samples changed from the characteristic melting pools to a structure with a lower average grain size accompanied by a decrease of a high fraction of high-angle grain boundaries and higher geometrically necessary dislocation density. Specifically, the grain size decreased from the average diameters of more than 20 µm to 3.9 µm and 4.1 µm for the SLM and conventionally prepared samples, respectively. In addition, the presented research has brought in the material constants of the Hensel-Spittel formula adapted to predict the hot flow stress evolution of the studied steel with respect to its 3D printed state.