EVALUATION OF TEMPERATURE AND STRESS IN FIRST STAGE HIGH PRESSURE TURBINE BLADES OF A DIRECTIONALLY-SOLIDIFIED SUPERALLOY DZ125 AFTER SERVICE IN AEROENGINES

摘要

To get the actual service temperature and stress distribution of turbine blades is very important for the design and maintenance in aeroengines. However, the measurement of temperature and stress in serviced blades has always been a challenge. It is necessary to develop an evaluation method based on the microstructural degradation of turbine blades. In this study, the microstructure of three turbine blades made of DZ125 alloy, which have been serviced for different service cycles, was investigated. The dissolution and rafting extent of γ' precipitates were quantitatively characterized by using the volume fraction (V_f) and rafting degree (Ω), respectively. The results show that the extent of microstructural degradation varies with the service time and location of three turbine blades. The V_f values decreased gradually and Ω values raised gradually in a certain location of turbine blades with the increase of service time. According to the service simulation experiments of DZ125 superalloy, the quantitative and approximate monotonic relationship was established among temperature, stress, V_f and Ω. The service temperature and stress of turbine blades have been evaluated by the above relationship. This study is helpful to understand the effect of service temperature and stress on microstructural degradation of directionally-solidified turbine blades, and probes for a new way to evaluate temperature and stress.