Grain Size Dependence of Creep Crack Growth in Ni-Cr Austenitic Steels

From single phase to two-phase alloys, creep crack growth behavior of Fe-15Cr-25Ni austenitic steels has been examined for different grain sizes at 973 and 1123 K. The creep crack growth rate increases with increasing grain size. An equation was found to describe the relation between the initiation time t_i or rupture time t_r and grain size d: t_r(i)d^β=C. The precipitation of grain boundary carbide decreases the effect of grain size on creep crack growth. Different grain size dependences on creep crack growth in other materials were also analysed. A damage model based on constrained cavity growth was shown to provide good predictions on the grain size effect on creep crack growth behavior.