## 1 Introduction  
Additive manufacturing (AM) is a relatively new innovative processing technology with exceptionally high design freedom that cannot be achieved with conventional manufacturing methods. Components can be manufactured directly from CAD (computer aided design) models. Due to layered build-up of the component, sophisticated geometries such as complex inner cooling structures in thermally loaded components or local modification of the materials can be implemented. These featuresmake them particularly interesting for applications in power engineering. Residual porosity of the products after manufacturing is a significant impact factor on the mechanical-technological properties of additively manufactured components. This may affect the mechanical properties, especially fatigue and fracture behavior of the final structures. In fact, pores [1; 2; 3; 4] and resulting notch effects [2; 4; 5; 6] are considered to be the main reason for the lower fatigue strength of additively manufactured materials in comparison to conventionally produced materials. The application of fracture mechanics-based damage tolerance concepts in condition assessment during the service life of components has been evaluated and regulated over many years in various industries such as aviation [7], nuclear [8], pressure vessel technology [9], and offshore wind power [10]. Ideally, these concepts should already be implemented in the design and manufacturing phase for strength and service life evaluation. For the application of fracture mechanics concepts including the damage tolerance concept, knowledge not only of the strength parameters but also of the crack propagation parameters are necessary. This is reflected in a series of publications on the experimental investigation of crack propagation parameters of laser powder bed fusion (LPBF)-manufactured, austenitic 316L steel specimens [1; 11; 12]. 316L was chosen because it is a commonly used steel grade with a wide range of applications (process, food, power conversion, etc.) and good powder availability. The fatigue crack propagation rates in all the three build directions (XY, ZX, ZY) of LPBF-manufactured 316L were found to be higher compared to wrought material [1]. This was attributed to the porosity of the LPBF manufactured material. For this reason, fatigue crack growth experiments were carried out on LPBF-manufactured 316L specimens, produced with process parameters according to the current state of technology. The experiments were accompanied by extensive microstructure investigations of the tested specimens. In addition, an advanced strategy will be presented to ensure safe application of AM-processed, pore-containing materials--in most cases, materials established in the market (e.g., 316L stainless steel) are applied in additive manufacturing processes and efforts are made to optimize the process towards reduced component porosity. Safe application of AM-manufactured components necessitates careful non-destructive porosity inspection and implementation in adapted lifetime models, such as those outlined in the following. In addition to this, we present a tailor-made material based on HiperFer [13; 14; 15; 16; 17; 18; 19] for additive manufacturing, which (i) develops its full performance potential in being processed by additive manufacturing (e.g., in situ heat treatment, high cooling rate, tailored microstructure) and (ii) counteracts probable process-related flaws by \"active\" crack-obstructing mechanisms (e.g., thermomechanically induced precipitation and sub-grain formation, such as that outlined in [18]). Furthermore, this paper demonstrates the implementation of the porosity aspect into fracture mechanics-based damage tolerance analysis for the design and manufacturing process of additively manufactured steel components. Using an additive manufactured downscaled pressure vessel model, the pore density was analyzed by means of computer tomography and the stress distribution was calculated on the basis of pore position in critical design areas of the component.