Tribological response of AA 2024-T3 aluminium alloy coated with a DLC duplex coating

• Sliding wear of 2024-T3 aluminum alloy coated with a DLC duplex coating was analyzed.
• Presence of a new CNiPCr graded layer was found by means of EPMA analysis.
• The DLC/CrC/CNiPCr/NiP coated system has been characterized by nanoindentation tests.
• A modified form of the model earlier advanced by Perriot and Barthel is employed.
• The integrity of the coated system was evaluated by means of a Hertzian formulation.

Considerable improvement in the tribological response was achieved during sliding wear tests against alumina ball, when AA 2024-T3-aluminium alloy substrate was coated with DLC/NiP duplex coating. Quantitative EPMA analysis carried out on the coated sample cross-section coupled with nanoindentation techniques allowed the identification of the coated system architecture as composed of 4 main layers, with distinct mechanical properties, on top of the aluminium substrate: DLC (a:C-H chromium dopped layer and graded layer of CrC), a newly formed graded layer of CNiPCr, product of the interdifusion during PVD processing, and the NiP coating. The change in the elastic modulus with penetration depth was described by means of an original approach that was developed for its specific application to multilayer coatings.