Study on Growth Mechanism and Characteristics of Zirconium Alloy Micro-Arc Oxidation Film

Ceramic coatings on R60705 zirconium alloy were prepared on the surface by the micro-arc oxidation (MAO) technique in electrolytes containing Na2SiO3, NaOH, and Na(2)EDTA. The growth behavior of the MAO ceramic coatings at different stages, including growth rate, microstructure, and phase composition, was investigated using the method of direct observation of the boundary area. The results showed that the growth of the MAO coatings on R60705 zirconium alloy occurred in both inward and outward directions. At an oxidation time of 5 min, the thickness of the oxidation layer increased fastest, reaching 103.43 mu m, with a growth rate of 0.345 mu m/s. After 5 min, the growth rate decreased and tended to level off around 15 min, with a thickness and growth rate of 162.7 mu m and 0.181 mu m/s, respectively. The total thickness of the coatings continuously increased throughout the process, with the outward growth thickness always higher than the inward growth thickness. The composition of the zirconium alloy micro-arc oxidation coatings mainly consisted of monoclinic zirconia (m-ZrO2), tetragonal zirconia (t-ZrO2), and a small amount of SiO2. The main elements in the coatings were Zr, O, and Si. The corrosion resistance of the zirconium alloy micro-arc oxidation coatings increased first and then decreased with increasing oxidation time, with a corrosion current density of 8.876 x 10(-9) A.cm(-2) at 15 min, indicating the best corrosion resistance.

Automated summary

Ceramic coatings were prepared on the surface of R60705 zirconium alloy using the micro-arc oxidation (MAO) technique. The growth behavior of the MAO coatings at different stages was investigated, revealing both inward and outward growth. The composition of the coatings included m-ZrO2, t-ZrO2, and a small amount of SiO2, with Zr, O, and Si as the main elements. The corrosion resistance of the coatings increased initially and then decreased with increasing oxidation time, with the best corrosion resistance observed at 15 min.