Structure and Infrared Emissivity Properties of the MAO Coatings Formed on TC4 Alloys in K(2)ZrF(6)-Based Solution

Micro-arc oxidation (MAO) ceramic coatings were formed on TC4 alloy surface in silicate and metaphosphate electrolytes based with K(2)ZrF(6) for various concentrations. X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) were used to characterize the phase composition, microstructure and chemical compositions of the coatings. The infrared emissivity of the coatings was measured at 50 °C in a wavelength range of 8–20 µm. The microstructural observations all revealed the typical porousstructures. Moreover, adecline in roughness and thickness of the prepared coatings can be observed when the concentration of K(2)ZrF(6) increases. Combined with the results of XRD and XPS, it was found that all the oxides existed as the amorphous form in the coatings except the TiO(2) phase. The coatings exhibited the highest infrared emissivity value (about 0.89) when the concentration of K(2)ZrF(6) was 6 g/L, which was possibly attributed to the defect microstructure and the optimal role of ZrO(2).