Influence of Ni-P + DLC multilayer coatings on the tensile properties of the AlSi10Mg alloy produced by Laser-based Powder Bed Fusion

The peculiar microstructure of the AlSi10Mg alloy produced by the laser-based powder bed fusion (L-PBF) process requires the development of specific heat treatments and coatings to exploit its potential fully. The study aims to evaluate the effect of the deposition of an anti-friction/wear Ni-9%P + DLC (hydrogenated amorphous carbon, a-C:H) multilayer coating produced in an industrial environment by the electroless process followed by Arc-Evaporation Physical Vapor Deposition (PVD), on the mechanical properties of the L-PBF AlSi10Mg alloy. In the processing sequence, the DLC deposition phase replaces the artificial aging step in the T5 (direct aging) and T6R (solution treatment, quenching, and aging) heat treatments to reduce industrial costs thanks to comparable temperatures and soaking times. Therefore, the coated samples undergo the following post-production cycles: (i) Ni-P + DLC deposition (T5-like heat treatment) and (ii) rapid solution (SHTR) (10 min at 510°C) + Ni-P + DLC deposition (T6R-like heat treatment). Tensile tests highlight a significant reduction in ductility for T6R-like and T5-like specimens due to the different mechanical responses under static load between the multilayer coating and the substrate. At the same time, no significant differences are found in terms of strength properties. In conclusion, the variation in the static mechanical property trade-off of L-PBF AlSi10Mg induced by this processing cycle reveals critical points to be taken into account when applying a multilayer coating to structural components.