Cyclic oxidation behaviour of the Al2TiO5/TiO2/ZrO2 composite coating on Ti–6Al–4V alloy with plasma electrolytic oxidation

Al2TiO5/TiO2/ZrO2 plasma electrolytic oxidation coating deposited on the surface of Ti–6Al–4V alloy was prepared in NaAlO2–NaH2PO2–NaOH electrolytes system, which was doped with ZrO2 micro-particles by a kind of pulsed bipolar plasma electrolytic oxidation. The microstructure, surface morphology and phase composition of the Al2TiO5/TiO2/ZrO2 coatings were studied by SEM and XRD, respectively. Its cyclic oxidation behaviour was studied over the temperature of 1000°C for 100 hours in dry air. After high-temperature oxidation, the original crater eruption topography of plasma electrolytic oxidation coating has disappeared and it obviously took a decreasing tendency of both pore numbers and their diameters. The scales of original plasma electrolytic oxidation coating consisted mostly of Al2TiO5, R-TiO2 and α-Al2O3intermixed with small amounts of ZrO2 particles. They were transferred into R-TiO2, α-Al2O3 and ZrO2 with small amounts of Al2TiO5 after high-temperature oxidation procedure. The weight gains of plas...