Influence of build orientation on high temperature fatigue crack growth mechanisms in Inconel 718 fabricated by laser powder bed fusion: Effects of temperature and hold time

Inconel 718 manufactured by Laser Powder Bed Fusion has been characterized in terms of the microstructure, effect of post-processing heat treatment, and hence dependence of fatigue crack growth (FCG) on build orientation. Long crack fatigue tests were conducted at different temperatures and frequencies. It was found that at 350 ⁰C (transgranular crack propagation) build orientation had no effect on FCG rates. However, at higher temperatures (time-dependent crack propagation) build orientation had a significant effect on FCG rates. This was primarily related to microstructural differences caused by the printing strategy in grain size distribution, grain shape and grain boundary character.