The Assessment of Service Induced Degradation of Nickel Based Superalloy Gas Turbine Blading

Abstract

Residual stress rupture properties have been determined directly for service run gas turbine blades manufactured from forged Nimonic 115, equiaxed cast IN 738LC and directionally solidified PWA 1422. The validity of the isostress rupture extrapolation procedure at service stress levels has been demonstrated (i.e., linear relationship between test temperature and log of rupture life at a given stress). Rupture tests carried out at greater than service stress levels gave a more conservative indication of the residual properties than those conducted at the service stress. The lack of any simple relationship between the microstructures and the residual properties is discussed.