Coatings of nanocrystalline metallic wires on steel substrate: mechanical characteristics of coating layer

Coatings are produced by wire arc spraying on a steel surface and the effect of coating thickness on the coating characteristics in terms of microhardness, residual stress and friction coefficient are examined. The wire used during coating is composed of FeCrBMnSi, which comprises nanocrystalline and amorphous phases. The twin wire arc spray system was incorporated to generate different coating thicknesses on steel substrate. The analytical tools including three-dimensional imaging optical and scanning electron microscopes, energy dispersive spectroscopy and X-ray diffraction (XRD) are used to assess the coating characteristics. It is found that the surface texture and surface roughness of the coatings change with coating thickness. Thus, reducing the coating thickness results in slightly increased texture height and surface roughness. Microhardness is almost 15% higher for the thin coating (300 μm) than the thick coating (550 μm). The residual stress developed in the coatings is tensile and it changes with coating thickness, such that it reduces for thick coating.