Tensile behavior and microstructure of the helium and hydrogen implanted 12% Cr-steel MANET

Tensile specimens of the tempered martensitic 12% Cr-steel MANET have been homogeneously implanted with 500 appm helium and/or 500 appm hydrogen between 80 and 500deg C to investigate synergistic effects of helium, hydrogen and irradiation damage. No difference was found between He-implanted specimens and specimens simultaneously implanted with helium and hydrogen. The implantation-induced hardening decreases with increasing temperature and changes into softening above 450deg C. The remaining total elongation was found to still be 2% below 400deg C. However, in the temperature region of dynamic strain aging near 300deg C, yield strength is close to ultimate strength, and uniform elongation drops from 3 to 0.3%. Hydrogen concentrations of 500 appm are found to modify neither strength nor ductility above 100deg C. The fracture mode of hydrogen and/or helium implanted specimens remained always ductile and transgranular. The observed microstructural changes are correlated with the tensile properties. (orig.)