TENSILE BEHAVIOR AND MICROSTRUCTURE OF THE HELIUM AND HYDROGEN IMPLANTED 12-PERCENT CR-STEEL MANET

Tensile specimens of the tempered martensitic 12% CT-steel MANET have been homogeneously implanted with 500 appm helium and/OT 500 appm hydrogen between 80 and 500-degrees-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 450-degrees-C. The remaining total elongation was found to still be 2% below 400-degrees-C. However, in the temperature region of dynamic strain aging near 300-degrees-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 100-degrees-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.