Creep Deformation Behaviour and its Effect on Creep Life and Rupture Ductility of W-Mo-balanced 9Cr Steels

The creep deformation behaviour and its effect on the creep life and rupture ductility are investigated for W-Mo-balanced 9Cr steels at 600 degrees C to 700 degrees C. The creep life is described as t(r) = 1.5/[(min) (dln/d)], where (min) and dln/d reflect the creep deformation behaviour in the transient and acceleration creep regions, respectively. The creep life is also correlated with the time to minimum creep rate t(m) as t(r) = gt(m), where g slightly increases with decreasing stress. The logarithm of creep rate linearly increases with strain in the initial stage of acceleration creep region. This is followed by a decrease in dlnd with strain at high stresses, resulting in ductile failure at large strains, while it is followed by an increase in dln/d with strain at low stresses, resulting in rupture at small strains.