Infragilimento da idrogeno nell'Inconel 718 prodotto mediante Selective Laser Melting

Inconel 718 is widely used to produce components subjected to relatively high temperatures and heavy loads. However, this alloy is also employed in aggressive environments promoting the production of hydrogen on the metal surface. Selective Laser Melting (SLM) is an emerging technology for the production of structural components, thanks to its ability to create complex geometries and reduce material consumption. Components produced by SLM are typically characterized by a peculiar microstructure and residual stresses that can affect hydrogen migration and accumulation. While the mechanical properties and fatigue endurance were deeply investigated in recent years, the resistance of SLMed Inconel 718 to the Hydrogen Embrittlement (HE) requires further investigation. The present paper deals with the effects of the SLM process on reducing the strength and ductility of Inconel 718. Standard tensile tests and slow strain rate tests were carried out on notched and unnotched specimens for different hydrogen concentrations. A coupled structural diffusion Finite Element model was developed and used to predict the hydrogen migration promoted by the hydrostatic stress gradients. Hydrogen-assisted damage processes are discussed and correlations between the hydrogen concentration and the mechanical strength under uniaxial and multiaxial stress state are derived.