SIM-AM 2023

Parametric Study of Directed Energy Deposition Of Duplex Stainless Steels To Optimize Ferrite-Austenite Phase Ratio And Residual Stresses

  • Weisz-Patrault, Daniel (CNRS, Ecole Polytechnique)

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Optimal material properties of duplex stainless steels generally require near 50-50 ferrite-austenite microstructures. The delta-ferrite to gamma-austenite phase transition generally occur between 1600K to 1300K. Thus, the development of additive manufacturing of duplex steels is hindered by difficulty controlling cooling conditions near the melt pool to ensure a balanced phase ratio. In addition, non-uniform phase distribution is usually observed as cooling conditions strongly depend on heat accumulation, distance to the substrate or local power and heat source speed variations. Thus, sufficiently fast part-scale process simulations are interesting to optimize process parameters to better predict and control the temperature history during fabrication and therefore solid state phase transitions. Furthermore, residual stresses also strongly depend on the complex temperature history, which should also be taken into account in the optimization of the phase field. In this contribution, we present a fast modeling of directed energy deposition including thermal analysis and diffusion of alloying element to take into account phase transitions [1], and residual stress computation [2]. This simulation tool is used as part-scale digital twin of the process. On this basis, a parametric study is proposed to obtain a uniform and balanced ferrite-austenite phase field and reasonable residual stresses by controlling (i) process parameters (e.g., power, heat source speed etc.), (ii) substrate temperature, and (iii) an additional heat source preheating the part in front of the melt pool. REFERENCES [1] A. Edwards, D. Weisz-Patrault, E. Charkaluk, Analysis and fast modelling of microstructures in duplex stainless steel formed by directed energy deposition additive manufacturing. Additive Manufacturing, 61 (2023), 103300. [2] D. Weisz-Patrault, P. Margerit, A. Constantinescu, Residual stresses in thin walled-structures manufactured by directed energy deposition: In-situ measurements, fast thermo-mechanical simulation and buckling, Additive Manufacturing (2022) 102903.