Computing the Durability of WAAM 18Ni-250 Maraging Steel Specimens with Surface Breaking Porosity

The durability assessment of additively manufactured parts needs to account for both surface-breaking material discontinuities and surface-breaking porosity and how these material discontinuities interact with parts that have been left in the as-built state. Furthermore, to be consistent with the airworthiness standards associated with the certification of metallic parts on military aircraft the durability analysis must be able to predict crack growth, as distinct from using a crack growth analysis in which parameters are adjusted so as to match measured data. To partially address this, the authors recently showed how the durability of wire arc additively manufactured (WAAM) 18Ni-250 maraging steel specimens, where failure was due to the interaction of small surface-breaking cracks with surface roughness, could be predicted using the Hartman-Schijve variant of the NASGRO crack growth equation. This paper illustrates how the same equation, with the same material parameters, can be used to predict the durability of a specimen where failure is due to surface-breaking porosity.

Automated summary

The durability assessment of additively manufactured parts must consider both surface-breaking material discontinuities and porosity, and how these factors interact with as-built parts. The authors have previously shown how the Hartman-Schijve variant of the NASGRO crack growth equation can predict the durability of wire arc additively manufactured specimens with surface-breaking cracks due to surface roughness. This paper demonstrates that the same equation can also be used to predict the durability of specimens with failure caused by surface-breaking porosity.