Stress corrosion cracking of an uranium-6 weight per cent niobium in gaseous oxygen, nitrogen and hydrogen

Stress corrosion cracking (SCC) of uranium-6 weight per cent niobium alloy is studied in gaseous oxygen at room temperature (for pressures between 4.10-7 and 0.15MPa) and 1000C (pressure of 0.15 MPa) and in gaseous hydrogen (for pressures between 10-6 and 0.15 MPa). SCC map and cracking kinetics are determined as fonctions of stress-intensity factor, pressure and temperature. For oxygen, temperature seems to have no effect on the alloy embrittlement within the range of this study but the pressure influence is more complex. At room temperature, hydrogen pressure less than 0.15 MPa has no influence on the cracking kinetics. For a pressure of 0.15 MPa, fracture occurs by hydriding reaction. Complementary analyses on fracture surfaces lead to propose different mechanics responsible for cracking kinetics in these environments