Comparison and evaluation of creep crack growth rate and fracture time forAlloy 800 by the Q* parameter

Creep crack growth tests were carried out under several temperature and str ess conditions for Fe-based superalloy Alloy 800 and the Q* parameter was a pplied to an evaluation of the crack growth rate at elevated temperatures f or DEN and CT specimens. Creep fracture times were evaluated with the param eter derived by integrating the creep crack growth rate formula expressed i n terms of the Q* parameter for DEN, CT and smooth specimens of Alloy 800 u nder several temperature and stress conditions. It was found that the creep crack growth rate for CT specimens is represented as the different data ba nds by the Q*; parameter for DEN specimens. However, it can be evaluated by parallel movement along the Q*; axis in the Q*; parameter-da/dt diagram fo r Alloy 800. The parameter {T(log(10)t(f) + 20) X 10(-3)} derived from the Q* parameter can compare and evaluate the difference in specimen shape and loading mechanism on creep fracture time using the identical parameter for Alloy 800. (C) 1999 Elsevier Science Ltd. All rights reserved.