Sustained peak low-cycle fatigue: The role of oxidation resistant bond coatings

Conference Dates

June 24-29, 2018


Important developments in turbine blade technology, including cast thin-walled airfoils with complex internal cooling passes, place significant thermal gradients and stresses on the multilayered coating systems used to thermally insulate the blade from the hot combustion gases. As gas turbine engine operating temperatures increase, the intermetallic bond coatings traditionally used in thermal barrier coating systems undergo increased creep deformation. Bond coats for single crystal turbine blades have been designed primarily for oxidation protection with minimal consideration of mechanical and microstructural optimization. At higher temperatures, intrinsic failure mechanisms of coatings such as rumpling and cracking due to sustained peak low-cycle fatigue (SPLCF), limit the lifetimes of engine blades [1]. Bond coatings have been shown to extend or reduce the SPLCF lifetime of a specimen as compared to uncoated single crystals. The mechanical and microstructural properties bond coatings and their oxides that impact fatigue crack propagation rates have been investigated.

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