抄録
Creep cavity populations and resultant density changes have been measured on interrupted creep specimens with aim of assessing the bulid up of creep damage in Cr-Mo-V steel that eventually leads to fracture.
Metallographic observations have shown two types of creep cavities associated with either grain boundary carbides or with non-metallic inclusions. The number of creep cavities associated with grain boundary carbides increases linearly with increasing creep strain and growth of the cavities along grain boundaries leads to grain boundary cracks, whereas nucleation and growth of the creep cavities associated with non-metallic inclusions are limited by the number and size of the inclusions. The data of density change is expressed reasonably by the empirical equation
-ΔD/D=2.5×103εtσ3.0exp(-234000/RT)
where ΔD/D is the density change, εis the creep strain (%), t is the time (h), σis the stress (kgf/mm2), R is the gas constant (8.314 J·mol-1·K-1), and T is the absolute temperature (K). This equation can be used to estimate the residual life of Cr-Mo-V steel components working under creep conditions.
