A STUDY OF CREEP CRACK-PROPAGATION OF HK-40 FURNACE TUBES WITH C-SHAPED SPECIMENS

C-shaped specimens are used to study the propagation of creep cracks in HK 40 furnace tubes. A potential difference equation is proposed to calibrate the creep crack. Experimental data are correlated with the linear elastic stress intensity factor K, net section stress sigma(net),, and creep energy integration C-t. Results show that the parameter C-t could describe fairly well the overall process of creep crack propagation. Furthermore, by examination of the microstructure in the crack tip region, it is concluded that the crack propagation is the result of the coalescence of the main crack and the cavities. On the basis of this observation, a creep crack propagation model is employed to estimate the crack growth rates. Good prediction of the crack growth behaviour has been achieved.