Book/Report

FZJ-2018-03053

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Der Einfluß von implantiertem Helium auf die mechanischen Eigenschaften des martensitischen Stahls DIN 1.4914 bei hohen Temperaturen

Stamm, U. (Corresponding author)FZJ*

1988
Kernforschungsanlage Jülich, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/18598

Report No.: Juel-2225

Abstract: Experiments with low helium concentrations suggest that ferritic-martensitic steels are more resistant against helium embrittlement than austenitic steels. In this work the effects of fusion-relevant high helium concentrations on the mechanical properties of the fully martensitic steel DIN 1.4914 (the reference material for NET) has been studied. Foil specimens of 90 um thickness of two different heats were homogeneously implanted with helium by a cyclotron under various conditions. Tensile tests were performed at temperatures from 273 K to 973 K and creep tests at 873 K and 973 K with specimens preimplanted at test temperatures. "In-beam" tests (creep to rupture under simultaneous implantation) were carried out at 873 K and 973 K with helium concentrations up to 3000 and 2700 appm, respectively. The ruptured specimens were investigated for fracture mode (SEM) and helium bubble microstructure (TEM). The main results are: Small variations in chemical composition lead to large differences in strength and ductility. The mechanical data obtained with nonimplanted foil specimens are in good agreement with literature data on bulk specimens. The rupture mode is always transcrystalline and ductile. Helium concentrations of 100 appm have no influence on the mechanical data in all experiments. Creep tests after implantation with 300 to 1000 appm show increasing rupture times and decreasing rupture strains, compared with unimplanted controls. "In-beam" tests show small differences in rupture time but no loss in ductility compared with the controls. The fracture mode remains transcrystalline. Only at the highest concentration of 2700 appm at 973 K a transition to intercrystalline fracture occurs. TEM observations shows facetted helium bubbles with {100} facets. The bubble radii increase with the square root of the helium content, whereas their density remains constant. Bubble radii and densities do not differ strongly from the values of austenitic steels and give no hints for differences in bubble nucleation and growth in those steels. For this reason the theoretical models developed for austenitic steels cannot explain the high resistivity of the martensitic steel against helium embrittlement.

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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