Comparison and evaluation of creep crack growth rate and fracture time for alloy 800 by the Ｑ parameter

摘要

Creep crack growth tests were carried out under several temperature and stress conditions for Fe-based superalloy Alloy 800 and the Q* parameter was applied to an evaluation of the crack growth rate at elevated temperatures for DEN and CTspecimens. Creep fracture times were evaluated with the parameter derived by integrating the creep crack growth rate formula expressed in terms of the Q* parameter for DEN, CT and smooth specimens of Alloy 800 under several temperature and stressconditions. It was found that the creep crack growth rate for CT specimens is represented as the different data bands by the Q* parameter for DEN specimens. However, it can be evaluated by parallel movement along the Q* axis in the Q* parameter-da/dtdiagram for Alloy 800. The parameter (T(log{sub}10{sup}(t{sub}f) + 20) ×10{sup}-3} derived from the Q* parameter car compare and evaluate the difference in specimen shape and loading mechanism on creep fracture time using the identical parameter forAlloy 800.