|About this Abstract
||2017 TMS Annual Meeting & Exhibition
||Materials for High Temperature Applications: Next Generation Superalloys and Beyond
||The Influence of Bond Coats on Crack Progression during Sustained Peak Low-Cycle Fatigue
||Marissa Lafata, Tresa Pollock
|On-Site Speaker (Planned)
Bond coats for single crystal turbine blades have been designed primarily for oxidation protection with minimal consideration of mechanical and microstructural optimization. Sustained peak low-cycle fatigue (SPLCF) cracks initiate at and subsequently propagate through the bond coating before entering the single crystal. Fatigue specimens of René N5 with several different bond coatings were compressively loaded in isothermal strain controlled tests. Initial results show that bond coatings can extend or reduce the lifetime of a specimen as compared to uncoated single crystals. Analysis using scanning electron microscopy, EBSD and EDS, provide insights into the deformation occurring as oxide-filled cracks propagate through the layers. Finite element modeling shows the oxide growth stresses on the crack faces significantly influence the crack propagation rate. Changes in composition, oxide growth stresses, and microstructure occur through the coating, IDZ, and superalloy. The role of microstructure and oxidation properties in minimizing crack propagation rates will be discussed.