The creep life can be evaluated by the degree of grain deformation since th
e grains of Cr-Mo base material deform in the direction of stress. The grai
n deformation method using image-processing technique is developed for life
assessment of in-service high temperature components. The new assessment m
odel for the method is presented to apply to in-service components and is v
erified by interrupted creep test for ex-serviced material of ICr-0.5Mo ste
el. The proposed model, which is irrespective of stress direction, is to ev
aluate mean of the absolute deviation for the measured aspect ratios of the
grains sections.