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

在研究项目“基于机理的粉末生产和工艺参数对激光粉末冶金压缩C+N钢在空气和腐蚀环境中的组织和变形行为的影响的评估”中，可以理解N合金化起始粉末的产生、N合金钢L激光-粉末床熔化过程中的组织形成过程和与之相关的性能之间的基本关系。在研究过程中，提出了一些新的科学问题，这些新的科学问题现在需要在这里要求的续展项目中得到回答。续展申请的首要目标是加深对L-PBF处理的氮合金奥氏体和双相钢的组织形成机制和相关性能的了解。为此，该项目采取了一种综合的方法，其中考虑了粉末生产和所产生的粉末的L-PBF处理，以及后处理步骤和所产生的组织和性能的表征。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被用来解释全局粉末性质，并将与粉末生产和调质参数相关联。在此基础上，推导出适用于L-PBF工艺的粉末特性。在此背景下，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是特别有趣的。因此，应该收集关于一次凝固模式、相形成动力学、缺陷形成和由此产生的材料性能之间的关系的基础知识。此外，还将确定使用增压(HIP)或部分熔化材料(SLPS)的后处理步骤对氮合金钢的组织和性能的影响。为了表征材料的性能，将在空气和腐蚀介质中进行循环试验，重点研究L-PBF双相钢的失效顺序和裂纹的萌生和扩展。根据项目合作伙伴的专业知识，对所调查的钢材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.