Approaches to fatigue lifing in a high strength polycrystalline nickel alloy.

• The paper provides a lifing approach for the polycrystalline nickel alloy RR1000. • The paper uses a novel approach of a temperature dependent version of the Walker strain equation. • The paper investigates the effects of inclusions on the fatigue life of RR1000 at high temperature. The development of high strength alloys with complex chemistries has led to modern nickel disc alloys being produced through a powder metallurgy process which often produces melt anomalies within the material microstructure. The current research investigates the effect of these melt anomalies on overall lifing approaches for the alloy RR1000, utilised here in its fine grained form. A Walker strain approach is applied to investigate the effect of temperature and R ratio on lifing parameters, and a temperature dependent version of the equation is suggested and used to produce predictions of notched specimen fatigue behaviour. It is found that hard particle inclusions dominate fatigue failures at long fatigue lives whereas failure occurred at the peened surface for shorter fatigue lives. However, lifing approaches were able to provide good fits across the entire data set irrespective of this behaviour change. [ABSTRACT FROM AUTHOR]