Measurement of the distribution of cavities on grain boundary and evaluation of damage parameters of SUS304 stainless steel under creep-fatigue condition
Tada Naoya; Fukuta Tetsufumi; Kitamura Takayuki; Ohtani Ryuichi
Abstract:Creep-fatigue tests of SUS304 stainless steel were conducted and creep cavities initiated on grain boundaries inside the specimen were observed on the longitudinal cross-section by means of a scanning laser microscope. The results obtained were as follows. (i) The shape of cavities was almost spherical when they were small. (ii) There was no preferential direction of grain boundaries for the cavity initiation. (iii) Since cavities preferentially grew and coalesced along grain boundaries perpendicular to the stress axis direction, the shape became slit like. Based on the experimental determination of cavities, four kinds of creep damage parameters, such as area fraction of cavities on cross section, fraction of cavities on grain boundary lines, areal cavity density, and A parameter were evaluated. Key Words:cavity, grain boundary, creep-fatigue, SUS304, scanning laser microscope, creep damage parameter