Characterization of soft magnetic spinel ferrite coating prepared by plasma spray

The primary objective of this work is to investigate the microstructure and tribological performance of magnetic nickel–zinc–magnesium ferrite coating prepared through plasma spray. The phase composition, morphology and valence state of the ferrite coating are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). It is found that the ferrite coating shows a spinel structure. The as-sprayed coating exhibits nanocrystalline with the grain size of 100–200 nm. According to the XPS analysis, the ferrite coating contains both Fe2 + and Fe3 +, a few Ni ions are reduced to metallic Ni. Tribological performance of the ferrite coating is tested in dry friction and 3.5 wt.% NaCl solution using a ball-on-disk test. The wear loss of the ferrite coating is lower than the substrate in both dry friction and NaCl solution under the same wear test conditions. The wear mechanism of the ferrite coating is dominated by delamination and brittle fracture. Microwave absorbing property of the ferrite shows a high value of magnetic loss factor in the frequency range of 1–12 GHz. The results suggest that plasma spray is a promising technology for the production of magnetic ferrite coatings.