MORPHOLOGY OF γ' PRECIPITATES AFTER SIMPLE AGING IN FIRST STAGE LOW PRESSURE TURBINE BLADE OF Ni-BASED SUPERALLOY AFTER SERVICED

摘要

To estimate the distribution of the temperature and the stress, and the stress direction of the blade in service, the morphology of the γ' precipitates in the Ni-based superalloy serviced as the 1st LPT blade of the aircraft engine and this aged one was investigated. Microstructure observations by a FE-SEM were carried out on the forty portions of the both sides of the perpendicular and the orthogonal sections at the vicinity of the blade surface in the suction and pressure sides. Most of the γ' precipitates kept cuboidal in shape in serviced blade. A lot of the secondary γ' precipitates in the γ matrix were observed at the root part. On the contrary, at the leading edge of the tip part, there were no secondary γ' precipitates. After simple aging, the low complete rafted γ/γ' structures were appeared at the suction sides of 70mm part, while the other portions, coarsening of the γ' precipitates was observed. Consequently, the 1st LPT blade in service, at the leading edge of the tip part was exposed to the highest temperature condition. However, the stress is extremely low in all portions.