Creep tests have been made on 2.9 Ni-1.1 Cr steel at 550 C under two stresses of 175 MPa and 195 MPa. Two quantitative analysis on the cavity size and density are followed by metallographic and fractographic method, and the results of 3-D data are compared with the 2-D result The relational equation is set as $\eta_B=ka^{\alpha}\eta^{\beta}$, where $eta_B$,$eta^$ cavity number density on the grain boundary and on the polished section, respectively, a the cavity diameter, k,α,β fitting constants, and the results show that the cavity diameter seems to be quite sensitive parameter in this relationship.
In two different hardness specimen, the cavity density and area fraction of cavity turn out to be larger in the specimen with the lower hardness level when the test duration is constants, while the reverse is found when the creep strain is constant.
