High voltage resistance ceramic coating fabricated on titanium alloy for insulation shielding application

To endow the insulation shielding of electromechanical devices, a TiO₂ based ceramic coating with high voltage resistance was fabricated on titanium alloy by plasma electrolytic oxidation (PEO). The effects of PEO coatings with different phase composition and microstructure on insulation performance were determined. The results show that the ceramic coating formed in the silicate-based solution was mainly composed of rutile, anatase TiO₂ and Al₂TiO₅. As the coating thickens from 10 to 36 µm, the increasing cross-sectional porosity enables the dielectric strength decrease from 32.94 ± 2.1 V/μm to 11.9 ± 0.71 V/μm and the electric resistivity drop from 1.17 × 10⁸ Ω cm to 0.99 × 10⁸ Ω cm respectively. With 2 g/L KOH added into the basic electrolyte, the thickness of coating significantly increased to 50.0 ± 2.1 µm, accompanied by the enhanced crystalline degree of rutile TiO₂ phase and the decreasing of internal defects. In this way, the optimum coating with preferable resistivity of 1.08 × 10¹⁰ Ω cm, high breakdown voltage of 617.78 ± 26.31 V and dielectric strength of 12.36 ± 0.53 V/μm was achieved.