The mechanism behind the effect of building orientation and surface roughness on hydrogen embrittlement of laser powder bed fused Ti-6Al-4V
Liesbet Deconinck, Elena Bernardo Quejido, María T. Villa Vidaller, Eric A. Jägle, Kim Verbeken, Tom Depover
Abstract
The interaction between hydrogen and laser powder bed fused ( L -PBF) Ti-6Al-4V is investigated, in combination with the influence of (post-)processing parameters, i.e. the building orientation (horizontal vs. vertical) and the surface finish (as-built vs. polished). After an extensive characterisation of the intrinsic properties of the additive manufactured material (including porosity and surface roughness), its interaction with hydrogen is thoroughly assessed via electrochemical hydrogen charging at room temperature. The stressed martensitic α’ microstructure shows beneficial properties against hydrogen assisted degradation. The higher effective surface area of the as-built material compared to the polished condition offers more opportunities for hydrogen absorption . Hydrogen uptake is also influenced by the orientation of the prior β grains, depending on the building orientation. Furthermore, porosities tend to accumulate hydrogen. Therefore, a flawless (sub)surface layer and a maximal density are essential for optimal safe use of L -PBF Ti-6Al-4V in hydrogen-rich environments.