High Temperature Fatigue Crack Growth in Nickel-Based Alloys Refurbished by Additive Manufacturing

Hybrid additive manufacturingAdditive manufacturing plays a crucial role in the restoration of gas turbine bladesTurbine blades, where, e.g., the damaged blade tip is reconstructed by the additive manufacturingAdditive manufacturing process on the existing blade made of a parent nickel-based alloy. However, inherent process-related defects in additively manufactured material, along with the interface created between the additively manufactured and the cast base material, impact the fatigue crack growthFatigue crack growth behavior in bi-material components. This study investigates the fatigue crack growthFatigue crack growth behavior in bi-material specimens of nickel-based alloysNickel-based alloys, specifically, additively manufactured STAL15 and cast alloy 247DS. The tests were conducted at 950 °C with stress ratios of 0.1 and −1. Metallographic and fractographic investigations were carried out to understand crack growth mechanisms. The results revealed significant retardation in crack growth at the interface. This study highlights the potential contributions of residual stressesResidual stress and microstructural differences to the observed crack growth retardation phenomenon, along with the conclusion from an earlier study on the effect of yield strength mismatch on crack growth behavior at a perpendicular interface in bi-material specimens.