Structure property and wear correlations in Al–Ni intermetallic coatings produced by atmospheric plasma spraying

Abstract Atmospheric plasma spraying (APS) is widely employed to fabricate protective coatings for engineering components requiring enhanced wear resistance and thermal stability. This study establishes structure property wear correlations in Al–Ni intermetallic coatings deposited on AISI 304 stainless steel using Ni/Al–Al and Ni₅Al–Al powder mixtures with varying nickel contents (10–50 wt%) and coating thicknesses (300–900 μm). Phase constitution, microstructure, porosity, microhardness, and tribological performance were systematically characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and pin-on-disc wear testing. A three-dimensional finite element (FE) wear model incorporating a modified Archard wear law and adaptive remeshing was developed to predict wear evolution and validate the experimental observations. XRD confirmed the formation of β-NiAl in all coatings, whereas γ′-Ni 3 Al was detected only in coatings containing the highest Ni-based powder content, coinciding with improved coating densification and hardness. Increasing the Ni-based powder content enhanced the coating hardness from 74 to 167 HV (126%) for the Ni/Al–Al system and from 81 to 178 HV (120%) for the Ni₅Al–Al system. The 5A9 coating (50 wt% Ni/Al [80Ni–20Al] powder–50 wt% Al, 900 μm) exhibited the best tribological performance, achieving the lowest experimental weight loss (11.2 mg) and minimum FE-predicted wear volume (0.153 mm 3 ), representing approximately a 76% reduction in wear loss compared with the poorest-performing 5B9 coating (50 wt% Ni₅Al [95Ni–5Al] powder–50 wt% Al, 900 μm) (47.1 mg, 0.274 mm 3 ). While increasing coating thickness progressively improved the wear resistance of the Ni/Al–Al coatings, the Ni₅Al–Al system exhibited an opposite thickness-dependent trend. The close agreement between experimental and numerical results validates the proposed FE model and demonstrates its capability for optimizing high-performance APS Al–Ni intermetallic coatings.