Hydrogen environment embrittlement (HEE) of additive manufactured (AM) 316L steel

增材制造（AM）钢具有高强度和延展性的上级组合，为减轻重量和近净形生产建筑部件提供了潜力。在含氢环境中，316L钢由于其固有的抗氢环境脆化（HEE）能力而成为最广泛使用的结构材料之一。虽然关于AM316L的基本结构和机械性能的出版物数量正在迅速增加，但迄今为止对其与氢的相互作用知之甚少。AM316 L的机械性能与其独特的、缺陷丰富的微观结构有关，这些微观结构具有尺度桥接特征，例如熔池边界、大角度晶界、亚晶粒胞状网络中的孔隙和高密度位错，以及变形诱导结构，例如位错和孪晶或新相，如马氏体。氢被认为可以改变缺陷自能，例如通过降低材料中的微结构缺陷如位错、堆垛层错和裂纹的形成能。这可能导致部件过早和灾难性的故障。最初的研究已经证明，AM316L在氢的存在下会受到精神上的影响，并降低了对HEE的抵抗力。该项目旨在研究AM316L在不同长度尺度上的HEE敏感性，直至纳米尺度。这里的主要假设是，HEE基于AM材料的独特微观结构，其中特定的主要缺陷类型是HEE的主要原因。在这个项目中，我们打算阐明这些缺陷类型，并了解在AM316L的主要脆化机制。通过连续的缺陷类型减少，我们打算提高AM316 L HHE敏感性，同时尽可能保持AM材料的上级机械性能。 因此，通过本项目建议书，我们打算对AM316L的HEE的基本理解做出贡献。这些知识可以改善基础材料的微观结构，并设计暴露于氢气的AM316L结构部件

Additively manufactured (AM) steel with its superior combination of high strength and ductility offers the potential of weight reduction and near net-shaped production of construction parts. In hydrogen-containing environments, 316L steel is among the most widely used structural materials due to its inherent resistance against hydrogen environmental embrittlement (HEE). While the number of publications on basic structural and mechanical properties of AM316L is rapidly increasing, little is known on its interaction with hydrogen to this day. The mechanical properties of AM316L are related to its unique, defect-rich microstructure with scale-bridging features such as melt-pool boundaries, high-angle grain boundaries, pores and high-density dislocations in sub-grain cellular networks as well as deformation-induced structures such as dislocations and twins or new phases like martensite. Hydrogen is considered to modify the defect self energies, for example by lowering the formation energy of microstructural defects such as dislocations, stacking faults and cracks in materials. This can result in parts’ premature and catastrophic failure. First studies have already demonstrated that AM316L is detrimentally affected by the presence of hydrogen and provides reduced resistance against HEE. This project aims to study the HEE susceptibility of AM316L on different length scales, down to the nano-scale. Main hypothesis is here, that HEE bases on the unique microstructure of the AM material, with specific dominant defect types being mainly responsible for HEE. In this project we intend to elucidate these defect types and to understand the main embrittlement mechanisms in AM316L. By successive defect type reduction, we intend to improve the AM316L HHE susceptibility while maintaining as much as possible the superior mechanical properties of the AM material. Hence, with this project proposal we intend to contribute to the fundamental understanding of HEE of AM316L. This knowledge allows for microstructural improvements of the base material and to design AM316L construction parts exposed to hydrogen