CHARACTERIZATION OF 7 POWER-GENERATING TURBINE ROTORS USING MICROSCOPY-BASED TECHNIQUES

Seven turbine generating rotors, either currently in service or recent ly retired, have been metallurgically examined using nondestructive te chniques, including hardiness testing and replication for optical and transmission electron microscopy. The aim has been to understand the m icrostructural changes occurring in a range of rotors due to service e xposure. A decrease in hardness of up to 7 % was noted, possibly arisi ng from carbide-induced loss of molybdenum from solid solution. Optica l microscopy was unable to detect service-induced microstructural chan ges. However, tine scale secondary precipitation of MC and M2C were ob served using transmission electron microscopy. A range of carbide comp ositional parameters associated with M3C were found to vary with servi ce exposure time.