Mechanism-based assessment of the influence of powder production and process parameters on the microstructure and the deformation behavior of SLM-compacted C + N steels in air and in corrosive environments

在“粉末生产和工艺参数对slm压缩C + N钢在空气和腐蚀环境中微观组织和变形行为影响的基于机理的评估”研究项目中，可以了解N合金起始粉末的生产、N合金钢在L-PBF加工（激光粉末床熔合）过程中的微观组织形成过程及其相关性能之间的基本关系。在研究项目期间，提出了一些新的科学问题，这些问题现在需要在这里要求的继续项目中得到回答。更新申请的总体目标是更深入地了解L-PBF处理的氮合金奥氏体和双相钢的微观结构形成机制和相关性能。为此，该项目采用整体方法，其中粉末生产和生产的粉末的L-PBF加工，以及后处理步骤和所得微观结构和性能的表征都被考虑在内。特别是，关于粉末流动过程中单个粉末颗粒之间相互作用的研究将用于解释粉末的整体特性，并将与粉末生产和调理参数相关联。在此基础上，将推导出适合L-PBF工艺的粉末性能。在这种情况下，还将研究粉末回收的影响。此外，考虑到L-PBF过程中特定的热条件，氮合金奥氏体和双相钢的凝固顺序取决于它们的铬和镍当量，这是特别有趣的。因此，应收集有关初次凝固方式、相形成动力学、缺陷形成与所得材料性能之间关系的基本知识。此外，还将确定使用增强压力（HIP）或材料部分熔化（SLPS）的后处理步骤对氮合金钢的显微组织和性能的影响。为了表征材料性能，将在空气和腐蚀性介质中进行循环测试，重点关注l - pbf双相钢的失效顺序和裂纹的产生和扩展。根据项目合作伙伴的专业知识，所研究钢的机械和化学性能的表征考虑了完整的工艺链。

In the research project "Mechanism-based assessment of the influence of powder production and process parameters on the microstructure and the deformation behavior of SLM-compressed C + N steels in air and in a corrosive environment", fundamental relationships between the production of N-alloyed starting powder, the microstructure formation process during the L-PBF processing (Laser-Powder Bed Fusion) of N-alloyed steels and the properties associated with them, could be understood. During the research project, a number of new scientific questions were raised, which are now to be answered within the continuation project requested here.The overarching goal of the renewal application is to create a deeper understanding of the microstructure formation mechanisms and the associated properties of nitrogen-alloyed austenites and duplex steels processed by L-PBF. For this purpose, the project takes an integral approach, in which the powder production and the L-PBF processing of the produced powders, as well as post processing steps and the characterization of the resulting microstructures and properties are regarded. In particular, investigations concerning the interactions between single powder particles during flowing of the powder will be used to explain the global powder properties and will be correlated to the powder production and conditioning parameters. Based on this, suitable powder properties will be derived for the L-PBF process. In this context, the influence of recycling of the powders will be also investigated. Furthermore, the solidification sequences of nitrogen-alloyed austenites and duplex steels depending on their chromium and nickel equivalents are of special interest considering the process specific thermal conditions during L-PBF. Thereby, fundamental knowledge shall be gathered on the relation of primary solidification mode, phase formation kinetics, defect formation and the resulting material properties. Additionally, the influence of post processing steps using enhanced pressure (HIP) or partly melting of the material (SLPS) on the microstructure and the properties of the nitrogen-alloyed steels will be determined. In order to characterize the material properties, cyclic testing will be performed in air and in corrosive media, focusing on the failure sequence and the initiation and propagation of cracks in L-PBF-built duplex steels. According to the expertise of the project partners, the characterization of the mechanical and chemical properties of the investigated steels considers the complete process chain.