BEHAVIOR OF HELIUM GAS ATOMS AND BUBBLES IN LOW-ACTIVATION 9CR MARTENSITIC STEELS

The behavior of helium-gas release from helium-implanted 9Cr martensit ic steels (500 appm implanted at 873 K) during tensile testing at 873 K was studied. Modified 9Cr-1Mo, low-activation 9Cr-2W and 9Cr-0.5V we re investigated. Cold-worked AISI 316 austenitic stainless steel was a lso investigated as a reference which was susceptible helium embrittle ment at high temperature. A helium release peak was observed at the mo ment of rupture in all the specimens. The total quantity of helium rel eased from these 9Cr steels was in the same range but smaller than tha t of 316CW steel. Helium gas in the 9Cr steels should be considered to remain in the matrix at their lath-packets even if deformed at 873 K. This is the reason why the martensitic steels have high resistance to helium embrittlement.