Tribological behavior of Ni/Al2O3 and Ni/Al2O3–MoS2 coatings prepared via brush plating

Given the inherent limitations in hardness and wear resistance of UNS S32205 duplex stainless steel, enhancing its surface mechanical properties is a significant research area. This study investigates the performance of pure Ni, Ni/Al 2 O 3 , and Ni/Al 2 O 3 –MoS 2 composite coatings deposited onto UNS S32205 duplex stainless steel substrates via the automatic brush plating method. The phase structure, micromorphology, thickness, adhesion, microhardness, and wear behavior of the coatings were evaluated. EDS analysis revealed uniform elemental distribution on the coating surfaces. XRD analysis demonstrates that the incorporation of Al 2 O 3 and MoS 2 nanoparticles significantly reduced the grain size of the coating. Under identical preparation conditions, the addition of Al 2 O 3 and MoS 2 nanoparticles decreased the deposition rate and thickness of the coatings while enhancing their adhesion and microhardness. The Ni/Al 2 O 3 and Ni/Al 2 O 3 –MoS 2 coatings achieved adhesion strengths of 168.5 N and 151.5 N, respectively. The microhardness of the Ni/Al 2 O 3 –MoS 2 coating reached 737.9 HV 0.1 , which represents an increase of 119.9% over the substrate. Wear tests showed that incorporating nanoparticles improved wear resistance by reducing the coefficient of friction (COF) and wear rate and mitigating susceptibility to abrasive wear. Under a 320 gf (approximately 3.14 N) load and a sliding speed of 2000 mm/min against a Si 3 N 4 counter ball, the Ni/Al 2 O 3 –MoS 2 coating exhibited a COF of 0.083 and a specific wear volume of 3.935×10 -6 mm 3 /Nm. These values are significantly lower than those of the S32205 substrate, representing reductions of 86.8% and 53.9%, respectively, which confirms the excellent wear resistance of the coating.