Material Property Studies of Two High-Pressure Turbine Rotors for Remaining Life Assessment

A remaining life assessment study was performed on two no-bore HP rotors after 169,000 hours of operation. These rotors were manufactured from 1CrMoV (ASTM A470, Class 8) steel. Southwest Research Institute conducted a materials evaluation program to generate pertinent material property data necessary to perform a SAFER analysis by Lehigh University. Two ring samples were removed from periphery locations of a rotor. One of the rings was from a packing location where the operating metal temperature was 860°F (460°C), and the other ring from the cold coupling end. Evaluation tests included chemical analysis, metallography, Auger analysis, tension and hardness, Charpy impact, fracture toughness, and stress rupture. A small sliver sample was available from the second rotor. Limited metallurgical analysis was conducted on this sample. Results indicated that the hot end embrittled in service with a shift in FATT of 240°F (116°C) when compared to the cold end. Fracture toughness versus temperature data were developed using various correlations available from the literature. Good correlation was found among the various procedures and lower bound curves were established for the hot and cold ends. Hot end toughness properties were significantly lower than those of the cold end. Auger results indicated segregation of phosphorus on the grain boundaries at the hot location. After service FATT can be predicted using the bulk phosphorus content and correlations available from the literature.