minimize Header

Prof. Dr.-Ing. Bernd Kuhn

Hydrogen: Electrolysis / Fuel Cells

Centre for Applied Research

Technology Campus Wörth-Wiesent

Professor

TC Wörth-Wiesent

0991/3615-8722

publications

Sortierung:

Journal article

P. Lehner
B. Blinn
T. Fischer
Bernd Kuhn
T. Beck

Influence of the strain rate on the fatigue behaviour of fully ferritic high chromium steel and P91 steel at high temperatures.

In: International Journal of Fatigue vol. 186 pg. 108388

(2024)

DOI: 10.1016/j.ijfatigue.2024.108388

show abstract

Fully ferritic, high-chromium HiperFer alloy presents a promising option, providing a combination of both, high corrosion resistance and material strength above 600 °C. Although these steels show improved strength at creep and thermomechanical loading compared to conventionally used 9–12 % Cr-steels, a comprehensive understanding of their fatigue behaviour and the influence of different strain rates is required. Hence, in this study the fatigue behaviour of HiperFer-17Cr2 was analysed in stress-controlled fatigue tests performed at temperatures above 600 °C and at 0.05 Hz and 5 Hz. Moreover, a martensitic steel P91 was investigated as a reference. The results obtained for HiperFer–17Cr2 reveal an increase in fatigue strength with a decrease in frequency and an increase in stress. Additionally, an influence of the frequency on the cyclic deformation behaviour of HiperFer-17Cr2 was observed, which is characterized by cyclic hardening. This cyclic hardening correlates with an increase in hardness, which is associated with the deformation induced formation of Laves phase particles. After LCF load with lower frequency a stronger hardness increase as well as a higher amount of Laves phase particles and smaller particle-free zones at the grain boundaries were observed, contributing to the higher fatigue strength obtained at lower strain rate.

Journal article

S. Möller
M. Reinhart
Bernd Kuhn
A. Kreter

Temperature dependence of sputtering yields of steels with various W content for plasma facing applications.

In: Fusion Engineering and Design vol. 215 pg. 114950

(2025)

DOI: 10.1016/j.fusengdes.2025.114950

show abstract

Materials are a key issue in any nuclear fusion reactor. For plasma-facing materials irradiation and sputtering limit their lifetime in a fusion power reactor. Steels allow for lower costs, reduced activation, and proven long irradiation lifetimes compared to tungsten at the expense of a lower sputtering lifetime. Several studies investigated the connected effects showing W-fuzz like surface morphology and a W enrichment through preferential sputtering, opening up a potentially significant increase of this sputtering lifetime of steels. The role of the W content in the steel is an open question. The presented exposure of 3 steels with W content from 0.5 to 2 at. % in deuterium plasma at 693–843 K sample temperature aims at resolving this. The experiments combine in-situ infrared imaging and passive spectroscopy with ex-situ ion-beam analysis. At the given conditions, a flux density independent exponential W enrichment within 70 s time-constant followed by a 1400 s time-constant nano-structure formation is observed. The overall effect is a reduction of the Fe sputtering yield by a factor 4.4, 3.0, and 2.5 for 2 %, 1.1 %, 0.5 % W steels, respectively. This factor reduces slightly with temperature by up to 20 % towards higher temperatures.