Abstract
Microstructural analyses by field emission-type scanning backscattered electron microscopy on chemical mechanically polished surfaces were performed for two types of ferritic heat-resisting steel that contained 12mass% chromium and 2mass% tungsten to characterize subgrain structures, which have the same tensile strengths but different creep-fatigue properties. The size distributions of the subgrains were quantitatively evaluated before and after creep-fatigue tests, respectively, to relate the creep-fatigue properties.
The steel that had a shorter creep-fatigue life showed denser precipitates on prior austenite grain boundaries and subgrains became coarse in local neighboring the grain boundaries. On the other hand, the steel with a longer creep-fatigue life, which showed less dense grain boundary precipitates and coarse subgrains exited in non-local. The analyses suggested that uniformity between microstructures on prior austenite grain boundaries and interior grains should be attained to improve the creep-fatigue properties.
