Effect of Concentration of Lithium Tetraborate Electrolyte on the Micro-Arc Oxidation Ceramic Layer on Zr-4 Alloy

In order to improve the service performance of Zr-4 alloy in nuclear industry and avoid introducing impurity elements， the micro-arc oxidation ceramic layer was prepared on the surface of Zr-4 alloy with Li2B4O7 as electrolyte.The effects of lithium tetraborate concentration on phase composition， microstructure， film thickness， hardness， roughness， wear resistance and corrosion resistance of micro-arc oxidation ceramic layer were investigated.Results showed that as the concentration of Li2B4O7 increased in the range of ρ(Li2B4O7)＝3～15 g/L， the conductivity of the electrolyte continued to increase， and the roughness of the ceramic layer continued to increase overall， which only slightly decreased when the electrolyte concentration changed from 6 g/L to 9 g/L.The thickness of micro-arc oxidation ceramic layer first continuously decreased in the range of ρ(Li2B4O7)＝3～9 g/L and then increased in the range of ρ(Li2B4O7)＝9～15 g/L.The hardness of the ceramic layer first decreased in the range of ρ(Li2B4O7)＝3 ～6 g/L，