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This paper details the experimental validation of a multi-scale simulation strategy that we developed for predicting the stresses and distortions induced by Powder Bed Fusion processes. The strategy comprises a meso-scale model, a macro-scale model, and a scaling method named Pointwise Strain Superposition. The first model evaluates the temperature, stress, and strain fields produced by a single scan line. The scaling method transfers the meso-scale results to the macro-scale model, which is then able to simulate the entire manufacturing process with a reasonable computational cost. The simulation strategy was validated by comparing its results with the stresses and distortions measured on several specimens made of selective laser melted Inconel 718. Stresses were measured through the blind hole drilling method on a cylindrical specimen printed with two different scanning strategies, while distortions were measured on a hollow cylinder and on a cantilever-shaped specimen after removing its supports. In both cases the simulation showed first- or higher-order accuracy despite the significant uncertainties regarding the input parameters and material properties. This robustness, coupled with its computational efficiency, leads us to believe that our simulation strategy could enhance the process optimization and provide a better understanding of the underlying physical phenomena along with their effects on the manufactured parts.

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 for different hydrogen concentrations. Hydrogen content was measured in each specimen after the mechanical test. Fractographic analyses, along with hydrogen diffusion models, were carried out to preliminarily investigate the hydrogen effect on the material strength.