Enhancement of corrosion and tribo resistance of electroless NiWP/B₄C composite coatings on aluminum alloys

Electroless NiWP alloy and NiWP-B4C composite coatings were produced at different B4C particle concentrations in the plating bath. The influence of B4C particle addition on surface morphology, distribution of particles, crystallite size, surface roughness, lattice strain, and phase composition were examined using FESEM equipped with Energy Dispersive Spectroscopy and X-ray diffraction (XRD) techniques. Surface roughness measurements were investigated using a 3D profilometer. To determine a stable suspension of dispersed particles, the zeta potentials of the plating baths were characterized. The microhardness of all coatings was determined according to the Vickers hardness test. The hardness was significantly enhanced by similar to 20 % for the 9 g/L B4C-reinforced NiWP coating compared to the pure NiWP. Electrochemical evaluations by Tafel polarization and electrochemical impedance spectroscopy (EIS) further demonstrated improved corrosion resistance, as evidenced by higher charge transfer resistance and enhanced barrier properties. This study investigates the dry sliding wear performance of NiWP alloy and its composites reinforced with B4C under varying sliding velocities (100-300 mm/s) and normal loads (2 N, 4 N, and 6 N). Worn surfaces were examined to elucidate the dominant wear mechanisms corresponding to each test condition, as characterized by scanning electron microscopy and energy-dispersive X-ray spectrometry analyses. Tribological analysis revealed that at lower velocities and loads, oxidative wear became the predominant mechanism. Unlike previous studies that primarily evaluated B4C-reinforced coatings under a single wear condition, this study systematically investigates the effect of B4C content on the tribological behavior of electroless Ni-W-P coatings under various loads and sliding speeds. This approach provides a comprehensive understanding of how B4C addition affects wear stability and friction response under different operating regimes, providing practical insights for real-world service environments. In contrast, high loading conditions led to a transition toward mechanisms such as plastic deformation, delamination, and abrasive wear. Overall, the work provides a comprehensive evaluation of how B4C concentration and tribological parameters influence the dry sliding wear behavior of NiWP alloys. The findings reveal that the 9 g/L B4C-reinforced NiWP coatings demonstrate superior wear performance, with the lowest wear rate and coefficient of friction observed among all tested conditions. These findings underscore the significance of delivering valuable insights into the design of multifunctional protective coatings for demanding applications in the automotive, aerospace, and energy sectors, where enhanced protection of aluminum alloys under wear and electrochemical conditions is required.