Preparation and thermal stability of black ceramic coatings on Ti alloys by micro arc oxidation

摘要

In this work, micro arc oxidation technique is used for the in situ preparation of black ceramin coatings on Ti-6A1-4V alloys in two different electrolytes.The chroma values of the coatings were calculated according to CIE L * a * b * colormetric system and the thermal stablilty was investigated in details.The results shows that both coatings (S1 and S2) are black with the L * of 8.81 and 14.88, respectively.Both coating are porous, amorphous and the thickness of S2 coating is larger than that of S1 coating.Under 200 ℃, both coatings are stable in color, composition and the structure and the thickness changes little as well.Further increasing the temperature, the coating color, surface morphologies and composition begin to change due to the oxidation effect of the coatings and the substrate.According to the thickness change after calcination,S2 coating is more stable than S1 under 400 ℃ and 500 ℃.