Creep behaviour of 14Cr-15Ni-Ti stainless steel at 923 K

Abstract

Creep behaviour of 14Cr-15Ni-Ti austenitic stainless steel has been investigated in the 20% cold worked condition at 923 K at various stress levels. The rupture lives were in the range 100-14,000 h. The stress dependence of minimum creep rate obeyed a power law and exhibited two slope behaviour with stress exponents of 5 at low stresses and 10 at high stresses. The two slope behaviour is also reflected in the apparent activation energy values in the low and high stress regimes. The high value of stress exponent is rationalized using modified Dorn equation invoking the concept of resisting stress. The resisting stress in the high stress regime is attributed to dislocation precipitate interaction. Creep ductility of the steel was low due to the presence of creep damage in the form of cracks. The precipitation of titanium carbides during creep provides strengthening to the matrix and prevents recovery of the cold worked structure.