Effects of electric parameters on structure and thermal control property of PEO ceramic coatings on Ti alloys

The aim of this work is to analyze the thermal control performance of the coatings prepared on Ti6Al4V alloys by plasma electrolytic oxidation (PEO) under different electric parameters in zirconate electrolytes. The composition and structure of the coatings were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), thickness measurement gauge and roughness measuring instrument, respectively. The infrared emissivity and solar absorptance of the ceramic coatings were evaluated by the UV-vis-NIR spectrophotometer and infrared reflectometer. The results show that the coatings have typical porous structure and the main phase composition is KZr2(PO4)3 phase. With the increase of current density, extension of duty ratios and decrease of working frequency, the absorptance (αs) decreases and the emissivity (ε) increases, due to the increase of the real surface area for radiating energy of coating and the thicker coating composed of nonmetallic inhibiting the absorptance of solar energy. Besides, the thermal shock tests and repeated experiments show outstanding thermal stability of coatings and satisfactory reusability of the electrolyte. In general, the coatings have better thermal control performance than the other coatings in the previous reports, and the above results indicate that the coatings prepared in this work have significantly promising industrialization potential in spacecraft field.