| Turbine casings used in fossil power plants are typical thick-section components serviced under high-temperature, high-pressure conditions. Hence, there components experiences fatigue damage due to thermal stress during operational transients as well as creep damage during steady operation. Cracks of turbine casing usually propagate by creep and fatigue. In this study, creep-fatigue crack growth tests were carried out using 0.5Cr-0.5Mo-0.25V casing steel taken from a retired turbine casing. The crack growth rate due to creep was characterized by the C_t parameter and that due to fatigue was characterized by ΔK according to well-known Paris Law. From the experimental results, metals for creep-fatigue crack growth behavior of 0.5Cr-0.5Mo-0.25V casting steel were investigated based on various material constitutive laws. The proposed relation between crack growth rate and fracture parameters such as (C_t)_(avg), ΔK can be used in predicting residual life of turbine casings. |
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