Electroless Ni-P + diamond-like carbon multilayer: Influence on tribological behaviour of AlSi10Mg produced by powder bed fusion - Laser beam

Powder Bed Fusion – Laser Beam (PBF-LB) technology has recently become popular for producing aluminium alloy complex-shaped components. However, the poor surface quality and relatively low hardness limit industrial applications where adequate tribological behaviour is critical. In this context, dry-sliding tests (ball-on-disk vs. Al2O3) were carried out on PBF-LB AlSi10Mg coated with a Ni-9%P + Diamond-Like Carbon (DLC) multilayer (belonging to the sub-type “hydrogenated amorphous carbon” i.e., a-C:H, with a Cr-W based bond layer), to investigate the influence on tribological behaviour of as-built and heat-treated substrates. Rapid solution treatment (10 min at 510 °C) after Ni-P deposition promoted an important decrease (-49 %) in wear depth compared to non heat-treated Ni-P coating without significantly affecting the coefficient of friction. The multilayer Ni-P + DLC coating further improved the tribological behaviour of the system, reducing about 5 times the coefficient of friction and the wear depth by 2 orders of magnitude compared to uncoated and Ni-P coated conditions. However, applying rapid solution in air after Ni-P deposition may cause interlayer oxidation and then DLC adhesive failure. In conclusion, the multilayer system significantly improved the tribological behaviour of the PBF-LB AlSi10Mg, providing an adequate load-bearing of the DLC topcoat regardless of the substrate microstructure, thus extending its use in sliding applications.