关键词: 气膜孔, 蠕变, 单晶高温合金, 筏化, 再结晶

Abstract: In order to meet the increase of the turbine inlet temperature of advanced aeroengines, film cooling is used to re-duce the blade temperature. However, the geometrical integrity of the blade structure is destroyed by the film cool-ing holes, which makes the turbine blade more susceptible to creep damage around the film cooling holes under the influence of centrifugal and thermal stresses. Therefore, it is important to understand the creep performance of nickel-based single crystal superalloys with film cooling holes. In this paper, the creep damage mechanism of DD6 single crystal superalloy with the cylindrical, dustpan and dovetail film cooling holes were studied through the creep experiment and finite element simulation at 1000℃/300MPa, and the detailed microscopic characterizations were conducted. The results show that the average creep lives of cylindrical and dustpan holes are similar to each other, and are increased by 17.4% and 15.8% respectively compared with the dovetail hole. Based on the fracture analy-sis, stress concentration and oxidation around the hole edge led to cracking first. Combined with SEM, EBSD and finite element simulation, the plastic deformation zone obtained by EBSD corresponds to the high stress region obtained by finite element analysis, and the γ' phase rafting morphology and the oxidation is related to the stress distribution. EDS analysis indicates that oxides can be divided into three layers, i.e. the outer layer is mainly NiO and CoO, the middle layer is mainly a mixture of Cr，Ni and Ta oxides, and the inner layer is Al2O3. The γ' phase rafting occurs adjacent to the oxide layer, and the plastic deformation and γ' phase rafting around the hole edge facilitate recrystallization formation.

Key words: Film cooling holes, Creep, Single crystal superalloy, Rafting, Recrystallization