Utilization of Powder Additivation and In-Situ Alloy Formation to Expand the Availability and Sustainability of Stainless Steel Alloy Powders for Additive Manufacturing

• Applicants: Professor Dr.-Ing. Christoph Broeckmann; Professor Dr.-Ing. Sebastian Weber
• Subject Area: Materials in Sintering Processes and Generative Manufacturing Processes ; Mechanical Properties of Metallic Materials and their Microstructural Origins ; Metallurgical, Thermal and Thermomechanical Treatment of Materials
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 560087872

Powder bed fusion of metals using a laser beam (PBF-LB/M)) is attracting significant industrial and scientific interest due to its geometric flexibility and high resource efficiency potential. However, the selection of processable iron-based materials is limited to alloys with a low cold cracking tendency due to the high temperature gradients and residual stress formation during the PBF-LB/M process. Therefore, the standard material for the PBF-LB/M process used in industry is the stainless steel X2CrNiMo17-12-2 due to its good weldability and high ductility. Its application is often limited by its low strength. One way to overcome the limited processability of standard grades and to expand the number and range of properties of processable materials can be found in powder additivation. The main objective of the project is to extend the basic understanding of the additivation of steel powder with silicon nitride particles (Si3N4) in the context of the production of nitrogen (N)-alloyed stainless steels, which was developed on a laboratory scale in the previous project, to an industrial production scale in order to improve the mechanical and corrosive properties through N. Two process routes will be pursued to achieve this. Firstly, X2CrNiMoN17-12-2 steel powder (DIN EN 1.4429, AISI 316LN) is to be produced quickly and economically by adding Si3N4 from the standard atomization of X2CrNiMo17-12-2 (DIN EN 1.4404, AISI 316L). This will expand the range of materials that can be used. On the other hand, the N content of pre-alloyed steel powders of the alloy X2CrNiMoN17-12-2 is to be increased by adding Si3N4 powder. In the selected approach, the Si3N4 particles should not interact with the molten steel during the PBF-LB/M process and should remain in the component as ceramic particles. In a subsequent hot isostatic pressing (HIP) process, the Si3N4 particles are then to be dissolved in such a way that the N is distributed as homogeneously as possible in an interstitial solution state in the austenitic metal matrix and thus serves as an alloying element. To achieve this goal on an industrial scale, it is necessary to control the segregation of large quantities of powder during storage, transport and processing of powder mixtures of stainless steel and Si3N4. To this end, mechanical alloying and simple mixing with different grain sizes are to be investigated to enable a uniform distribution and sufficient quantity of Si3N4 particles in the component after industrial PBF-LB/M production. Subsequently, the microstructure development in PBF-LB/M and subsequent HIP will be characterized and thus optimized by cross-scale microstructure analyses and thermodynamic simulations. At the same time, the static and dynamic mechanical properties will be determined and understood in the context of the manufacturing process chain and the dependent microstructure.

• DFG Programme: Research Grants (Transfer Project)
• Application Partner: Outokumpu Nirosta GmbH