Preparation of high-performance Ni-Co-Y2O3 coating by optimizing surfactant concentration and its application in nut reinforcement

In this study, the effects of sodium dodecyl sulfate (SDS) concentration (2–8 g/L) on the microstructure and properties of Ni-Co-Y 2 O 3 composite coatings were systematically investigated. A composite coating is prepared with Cu as the substrate. XRD analysis reveals that Ni and Co form an alloy phase (Ni-Co). Moreover, when the SDS concentration is 6 g/L, the diffraction peak intensity reaches its maximum value, indicating optimal crystallinity. The SEM and AFM results demonstrated that when the SDS concentration was 6 g/L, the agglomeration of Y 2 O 3 particles could be effectively suppressed, resulting in a dense and smooth coating surface. However, insufficient dispersion at low concentrations (2–4 g/L) or interference from high-concentration micelles (8 g/L) caused an increase in surface roughness. The cyclic voltammetry curve shows that the reaction is easy to carry out and the deposition is efficient when the concentration of SDS is 6 g/L high concentration will increase the viscosity of the electrolyte and shield the electrode. XPS confirmed that the chemical states of Ni, Co and Y were stable at this concentration, and when the concentration of SDS was 8 g/L, the chemical valence of Ni/Co was significantly changed. The friction and wear and hardness tests show that the coating prepared with SDS concentration of 6 g/L has the lowest friction coefficient and the highest hardness. Electrochemical tests showed that the coating prepared with SDS concentration of 6 g/L had the highest corrosion potential and the best corrosion resistance. The uncoated M8 nut has low hardness and is easy to be corroded. The hardness of the nut prepared with Ni-Co-Y 2 O 3 coating using SDS as surfactant is 518 HV, which is 71.5 % higher than that without coating, and the corrosion resistance is remarkable after 48 and 96 h of salt water immersion. • Ni-Co-Y 2 O 3 coating prepared with 6 g/L SDS performs best due to the uniform distribution of Y 2 O 3 . • Y 2 O 3 is poor dispersion with 2–4 g/L SDS. Micelles are excess with 8 g/L SDS. Properties are worse. • Coating on M8 nuts prepared with 6 g/L SDS is harder, dense, better corrosion resistance than others.