Surface engineering of PBF-LB AlSi10Mg components: integration of Ni-P/DLC multilayer coating within a simplified post-processing route

Abstract Additive manufacturing of aluminium alloys via Powder Bed Fusion-Laser Beam (PBF-LB) enables lightweight components with complex geometries, but surface quality and post-processing remain major limitations for industrial applications. This study investigates the feasibility of applying a multilayer Ni-9%P + ( a -C:H)DLC (diamond-like carbon) coating to a real PBF-LB AlSi10Mg component through a simplified post-processing route. A motorcycle upper triple clamp (yoke) was manufactured via PBF-LB and subjected to minimal surface preparation, limited to depowdering and local finishing operations. An electroless Ni-P interlayer was deposited to provide conformal coverage and load support, followed by plasma-assisted chemical vapor deposition (PA-CVD) of the ( a -C:H)DLC topcoat. Surface morphology, coating thickness, interfacial characteristics, and mechanical properties were analysed using microscopy, profilometry, indentation, and scratch testing. The Ni-P interlayer provided conformal coverage over the rough surface: an average thickness of 22 ± 1.5 µm was measured in the analysed cross-sections. The DLC topcoat, successfully deposited even in geometrically complex regions, exhibited a thickness of approximately 1.5 ± 0.5 µm and a hardness of 27.0 ± 5.5 GPa. Scratch testing yielded a critical load (LC2) of 33.9 ± 2 N, indicating a good adhesion. Local DLC thickness variations were attributed to the line-of-sight nature of the PA-CVD process. The multilayer coating system largely replicated the underlying surface morphology, and representative residual particles from the depowdering media were observed to be encapsulated by the Ni-P layer. The proposed multilayer architecture can be integrated into a simplified PBF-LB AlSi10Mg manufacturing chain, reducing post-processing while enabling high-performance tribological coatings for lightweight structural applications.