Considerations in the Fatigue Lifing of a High Strength Nickel Alloy

Nickel-based superalloys are strategically of great importance due to their impressive high temperature properties, which render them a strong candidate for critical rotating parts within the gas turbine engine. With new engine designs continually evolving towards the use of higher strength alloys, the sensitivity of these materials to flaws such as microstructural anomalies, also increases. It is therefore key to understand such failure mechanisms and develop accurate life prediction methodologies.

The current submission seeks to collate the findings of a significant test programme, which is representative of in-service conditions and utilises strain controlled fatigue testing of the nickel superalloy RR1000. This project aims to consider failure mechanisms as a function of grain size, with particular focus on inclusion characteristics and surface finish. Through the development of lifing techniques, appropriate to microstructure and inclusive of melt anomaly consideration, a broader understanding of the constitutive behaviour of RR1000 is provided.