Synthesis of a novel Ni–B/YSZ metal-ceramic composite coating via single-step electrodeposition at different current density

Abstract

A novel metal-ceramic composite coating of Ni–B/YSZ has been synthesized via single-step electrodeposition process at different current density. Influences of electrodeposition current density on its structure (morphology, phase structure, roughness, crystallite size), composition (YSZ content) and properties (hardness, corrosion resistance) were evaluated. These coatings are compact, without cracks, showing nodular or cauliflower-like morphology in a nanocrystalline structure with crystallite size about 9–11 nm. Ni (111) plane was the only preferred orientation and is independent of current density. Current density affects YSZ particle content in coating, nodule size, hardness, and anti-corrosion properties. The roughness of these coatings is about 67–71 nm (Sa) dependent on current density, and low current density could slightly reduce the roughness. The doped YSZ particles changed Ni–B matrix to a crystalline structure and enhanced the hardness. The maximum hardness was 920.5 HV at 5 A dm-2. Electrochemical impedance spectroscopy results indicated that the best corrosion-resistant properties combined electrochemical stability (long service life) of the nanocrystalline coating could be obtained at 4 A dm-2. The corrosion mechanism has gone through three stages corresponding to one-time, two-time and three-time constant of EEC models, respectively. Ni–B/YSZ has large potential merits in field of corrosion and wear resistance.