Comparative Surface and Interfacial Analysis of AlCrN Coatings Deposited on N-PIII-Treated and Plasma-Nitrided AISI H13 Steel

This study evaluates nitrogen plasma immersion ion implantation (PIII) effects on the microstructure, mechanical response, and tribological performance of duplex coatings on AISI H13 steel, produced by nitriding and AlCrN physical vapor deposition (PVD). Results were compared with conventional plasma nitriding (PN) performed at the same temperature (375 °C) and with an industrial duplex coating. PIII formed a thinner modified layer than PN (15 µm versus 55 µm); both mainly produced nitrogen-expanded martensite (α′N). PN yielded higher nitrogen contents and substantial γ′-Fe4N and ε-Fe2–3N formation in the compound layer. During PVD, this nitride-rich layer partially decomposed into low-nitrogen martensite due to chemical-potential gradients, impairing tribological resistance. PIII-treated surfaces developed much smaller depletion zones, attributed to the thinner nitride-layer and enhanced nitrogen mobility in α′N at the PVD temperature. Consequently, PIII + PVD improved wear performance by 20% under the severest condition compared with PN + PVD. The microwear tests employed here, still underexplored, impose contact pressures one order of magnitude above those typically encountered in conventional tests. Controlling the load enabled evaluation of wear-severity regimes and the hardness-to-elastic-modulus ratio as a wear-resistance indicator. The findings demonstrate that interface design and nitrided case stability govern load-bearing capacity in duplex-coated tool steels.