High Cycle Fatigue Behaviour of 316L Stainless Steel Produced via Selective Laser Melting Method and Post Processed by Hot Rotary Swaging

• Published in: Materials Vol. 16; no. 9; p. 3400
• Main Authors: Opěla, Petr, Benč, Marek, Kolomy, Stepan, Jakůbek, Zdeněk, Beranová, Denisa
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 26.04.2023; MDPI
• Subjects: 316L steel; Additive manufacturing; Aging; Analysis; Austenitic stainless steels; Data acquisition; Deformation; Dislocation density; Ductility; Fatigue strength; Grain boundaries; Grain size; Hardness; High cycle fatigue; hot compression testing; hot rotary swaging; Laser beam melting; Laser sintering; Mechanical properties; Metal fatigue; Methods; Microhardness; microstructure; Nickel alloys; Porosity; Power; Residual stress; Rotary swaging; selective laser melting; Stainless steel; Swaging; Tensile strength; Three dimensional printing; Titanium alloys; Workpieces; Yield strength; United Kingdom; Czech Republic; high cycle fatigue; selective laser melting; microstructure; hot compression testing; 316L steel; hot rotary swaging
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma16093400

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.