## 4 Conclusions  
### Influence of Crack Propagation Rate on Component Lifetime  
According to the fracture-mechanics based damage tolerance concept, crack propagation rate is a crucial factor, controlling the residual lifetime of components and the estimation of in-service inspection intervals. To exemplarily illustrate this, we calculated the effect of the measured crack propagation rates on the growth of a postulated initial crack in the experimental vessel (outlined in Section 2.1, cf. Figures 1 and 25). The stress calculation was carried out by applying the finite element analysis (FEA) software package ANSYS 19.2. The calculated von Mises equivalent stress in the stress concentration area around the nozzle intersection of the pressure vessel under an internal pressure of 133.1 bar (permissible pressure according to technical code [36]) is given in Figure 26.  
Figure 23: Fatigue cracking within particle-free zones (PFZs) in conventionally produced and higher tungsten-alloyed HiperFer.  
Figure 24: EBSD micrographs (IPFs) of LMD-processed HiperFerAM: (**a**) 3 mm of beam diameter, showing rod-shaped grains (in the center region), adjacent to equi-axed grains and fine grain formation in re-molten regions; (**b**) 0.66 mm beam diameter, depicting less and thinner rod-shaped grains in the center and generally smaller grain size.  
For the analytical crack growth calculations, we postulated a semi-elliptical surface-crack, parallel to the vessel axis in the maximum stress zone at the nozzle intersection (cf. red area in Figure 1). The stress intensity factor solution for the two-dimensional stress fields (according to [PERSON] et al. [37]) was utilized for the calculation, applying the fracture mechanics software tool IWM VERB [38]. The postulated initial crack had a depth of 2 mm and a semi-axial aspect ratio of 1/10. Cyclic loading was accomplished by alternating the internal pressure between zero and 133.1 bar. To simulate and show any relevant and distinguishable fatigue crack growth and to exceed all threshold values for FCG, we used a scaling factor of 2 on the stresses of Figure 1.  
All the measured crack propagation curves were approximated by enveloping a linear relationship in double logarithmic plotting according to the Paris' Law [39] and compared to the standard crack propagation rates for ferritic and austenitic steels contained in the ASME Boiler and Pressure Vessel Code [40].  
Figures 27 and 28 display the impact of the measured crack propagation rates in calculated crack growth diagrams at ambient and elevated temperatures, respectively. In both diagrams, the standard crack propagation rates for ferritic and austenitic steels (in air) according to the ASME Boiler and Pressure Vessel Code [40] are included for comparison to the crack propagation rates measured at 316L,  
Figure 26: Stress distribution (von Mises) in the nozzle intersection area at 133.1 bar internal pressure.  
Figure 25: Finite element model of the pressure vessel with nozzle intersection geometry.  
Crofer22 H, and HiperFer. The results exemplarily show the enormous influence of material inherent resistance to crack growth on fatigue exhaustion and residual lifetime of components.