Influence of film cooling holes and thermal barrier coating on the creep behavior of DD6 single crystal superalloy

In this study, creep tests were conducted on DD6 single crystal superalloy specimens containing different film cooling holes (FCHs) and thermal barrier coating (TBC) under conditions of 1000 degrees C and 300 MPa. Through the analysis of experimental data and characterization of the microstructure after creep fracture, the effects of FCHs and TBC on the high-temperature creep properties of DD6 alloy were evaluated. The results indicate that all specimens cracked from the FCH edges. During the creep process, oxide layer and recrystallization formed at the FCH surface, which facilitated the premature initiation of cracks. The gamma ' precipitates near the FCHs exhibit varying degrees of rafting due to different stress states, the high-stress zone with more significant gamma ' precipitate rafting near the FCHs provided a pathway for crack propagation. The interdiffusion of elements between the TBC and the substrate altered the microstructure of the alloy and reduced creep performance. These findings reveal the influence of FCHs and TBC on the creep properties of DD6 alloy and explain the mechanisms, providing practical insights for the assessment of creep performance of turbine blades.