On TC4 Alloys by Micro-Arc Oxidation (Materials EISSN 1996-1944)
Ceramic coatings with high emissivity were fabricated on TC4 alloys by micro-arc oxidation technique (MAO) in mixed silicate and phosphate electrolytes with varying KMnO4 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 KMnO4, but the roughness of the coatings first decreased and then increased slightly due to the inhibitory effect of KMnO4 on Na2SiO3 deposition.
The main phase composition of the coatings was anatase and rutile TiO2, amorphous form of SiO2 and MnO2. The infrared emissivity value of the coatings strongly depended on KMnO4 concentration, the coating formed at the concentration of 0.8 g/L KMnO4 reached the highest and an average of up to 0.87 was observed.
Materials 2017, 10(11), 1301; doi:10.3390/ma10111301