Temperature-dependent fatigue behavior of additively manufactured Hastelloy-X: The effect of manufacturing process

This study examined the strain-controlled, fully-reversed fatigue behavior of Hastelloy-X produced by two distinct additive manufacturing techniques, laser powder bed fusion (L-PBF) and laser powder directed energy deposition (LP-DED), across a temperature range from cryogenic conditions (-195 degrees C) to elevated temperatures (up to 760 degrees C). The fatigue crack initiation behavior was governed by persistent slip bands (PSBs) at lower temperatures (-195 degrees C to 427 degrees C) in contrast to temperatures above 427 degrees C where PSBs were absent. At elevated temperatures, in the absence of PSBs, the accumulation of fatigue damage appeared to be more rapid, leading to shorter fatigue lives. The room temperature fatigue lives at lower strain amplitudes were governed by fatigue crack initiation and were shorter for the LP-DED material that permitted easier slip. At-195 degrees C to 427 degrees C, fatigue lives of LP-DED material at higher strain amplitudes were governed by crack growth and were prolonged by the more plasticity-induced crack closure as compared to the L-PBF material. Above 427 degrees C, the absence of PSBs was equally damaging for both processes.