Scatter in Dwell Time Cracking for a Ni-Based Superalloy in Combination With Overloads

Abstract

In this paper, scatter in crack growth for dwell time loadings in combination with overloads has been investigated. Multiple tests were performed for surface cracks at 550 °C in the commonly used high temperature material Inconel 718. The test specimens originate from two different batches which also provide for a discussion of how material properties affect the dwell time damage and overload impact. In combination with these tests, an investigation of the microstructure was also carried out, which shows how it influences the growth rate. The results from this study show that, in order to take overloads into consideration when analyzing spectrum loadings containing dwell times, one needs a substantial amount of material data available as the scatter seen from one batch to the other are of significant proportions.