Influence of KMnO(4) Concentrationon Infrared Emissivity of Coatings Formed on TC4 Alloys by Micro-Arc Oxidation

Ceramic coatings with high emissivity were fabricated on TC4 alloys by micro-arc oxidation technique (MAO) in mixed silicate and phosphate electrolytes with varying KMnO(4) addition. The microstructure, phase and chemical composition were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), and the infrared emissivity of the MAO coatings was measured in a waveband of 5–20 μm. The results show that the thickness of the coatings increased with the addition of KMnO(4), but the roughness of the coatings first decreased and then increased slightly due to the inhibitory effect of KMnO(4) on Na(2)SiO(3) deposition. The main phase composition of the coatings was anatase and rutile TiO(2), amorphous form of SiO(2) and MnO(2). The infrared emissivity value of the coatings strongly depended on KMnO(4) concentration, the coating formed at the concentration of 0.8 g/L KMnO(4) reached the highest and an average of up to 0.87 was observed.