Fatigue crack retardation associated with creep deformation induced by a tension hold in a single crystal Ni-base superalloy

Effect of creep deformation at crack tip on fatigue crack propagation in a single crystal Ni-base superalloy was investigated. Crack propagation test was conducted at 900 degrees C, introducing a single tension hold during fatigue loading. After the tension hold, nascent crack was immediately initiated when the fatigue loading was restarted. Subsequently, crack propagation rate significantly decreased and remained low for a certain distance, followed by its rapid acceleration and convergence on that under pure fatigue condition. This phenomenon was attributed to mechanisms based on two different concepts of crack closure and residual compressive stress. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.