|Title||Competing Modes for Crack Initiation from Non-metallic Inclusions and Intrinsic Microstructural Features During Fatigue in a Polycrystalline Nickel-Based Superalloy|
|Publication Type||Journal Article|
|Year of Publication||2018|
|Authors||Stinville JCharles, Martin E, Karadge M, Ismonov S, Soare M, Hanlon T, Sundaram S, Echlin MLLP, Callahan PG, Lenthe WC, Miao J, Wessman AE, Finlay R, Loghin A, Marte J, Pollock TM|
|Journal||Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science|
Cyclic fatigue experiments in the high and very high cycle fatigue regimes have been performed on a René 88DT polycrystalline nickel-based superalloy. The microstructural configurations that favor early strain localization and fatigue crack initiation at high temperature from 400 °C to 650 °C have been investigated. Competing failure modes are observed in the high to the very high cycle fatigue regime. Fatigue cracks initiate from non-metallic inclusions and from intrinsic internal microstructural features. Interestingly, as stresses are reduced into the very high cycle regime, there is a transition to initiation only at crystallographic facets. At higher stress in the high cycle fatigue regime, a significant fraction of specimens initiate cracks at non-metallic inclusions. This transition is analyzed with regard to microstructural features that favor strain localization and accumulate damage early during cycling.