Creep life prediction of service-exposed turbine blades

The aim of this research work was to study the possibility of predicting the operational creep life of service-exposed blades used in industrial gas turbines. This prediction is based on the determination of blades creep life using stress–rupture test under accelerated test conditions where the applied stresses were 400,500 and 600 MPa and the test temperature was 850 °C. The study concentrated on creep behavior of service-exposed blades having different actual service lifes. The test specimens were prepared from first stage turbine blades made of Ni-based superalloy (IN-738). Larson–Miller parameter was used to extrapolate the stress–rupture test results to the actual operating conditions of blades. The operational creep life and the residual life of service-exposed blades were determined employing the life fraction rule.