Future, flexible thermal energy conversion systems require new, demand-optimized high-performance materials. The High performance Ferritic (HiperFer) stainless steels, under development at the Institute of Microstructure and Properties of Materials (IEK-2) at Forschungszentrum Jülich GmbH in Germany, provide a balanced combination of fatigue, creep and corrosion resistance at reasonable price. This paper outlines the scientific background of alloy performance development, which resulted in an age-hardening ferritic, stainless steel grade. Furthermore, technological properties are addressed and the potential concerning application is estimated by benchmarking versus conventional state of the art materials.

The 22 wt.% Cr, fully ferritic stainless steel Crofer^®22 H has higher thermomechanical fatigue (TMF)- lifetime compared to advanced ferritic-martensitic P91, which is assumed to be caused by different damage tolerance, leading to differences in crack propagation and failure mechanisms. To analyze this, instrumented cyclic indentation tests (CITs) were used because the material’s cyclic hardening potential—which strongly correlates with damage tolerance, can be determined by analyzing the deformation behavior in CITs. In the presented work, CITs were performed for both materials at specimens loaded for different numbers of TMF-cycles. These investigations show higher damage tolerance for Crofer^®22 H and demonstrate changes in damage tolerance during TMF-loading for both materials, which correlates with the cyclic deformation behavior observed in TMF-tests. Furthermore, the results obtained at Crofer^®22 H indicate an increase of damage tolerance in the second half of TMF-lifetime, which cannot be observed for P91. Moreover, CITs were performed at Crofer^®22 H in the vicinity of a fatigue crack, enabling to locally analyze the damage tolerance. These CITs show differences between crack edges and the crack tip. Conclusively, the presented results demonstrate that CITs can be utilized to analyze TMF-induced changes in damage tolerance.

Strong efforts are made internationally to optimize the process control of laser additive manufacturing processes. For this purpose, advanced detectors and monitoring software are being developed to control the quality of production. However, commercial suppliers of metal powders and part manufacturers are essentially focused on well-established materials. This article demonstrates the potential of optimized process control. Furthermore, we outline the development of a new high temperature structural steel, tailored to best utilize the advantages of additive manufacturing techniques. In this context, the impact of production-induced porosity on fatigue strength of austenitic 316L is presented. Additionally, we discuss the first conceptual results of a novel ferritic steel, named HiperFer (High Performance Ferrite), which was designed for increased fatigue strength. This ferritic, Laves phase-strengthened, stainless steel could be used for a wide range of structural components in power and (petro)chemical engineering at maximum temperatures ranging from about 580 to 650 °C. This material benefits from in situ heat treatment and counteracts process-related defects by “reactive” crack obstruction mechanisms, hampering both crack initiation and crack propagation. In this way, increased fatigue resistance and safety can be achieved.