Favorable deposition of γ-Al2O3 coatings by cathode plasma electrolysis for high-temperature application of Ti-45Al-8.5Nb alloys

Abstract

Cathode plasma electrolysis deposition (CPED) has been used to prepare γ-Al2O3 coatings on Ti-45Al-8.5Nb alloys for high-temperature application. The effect of deposition voltage and duty cycle on microstructure and high-temperature oxidation resistance of the coatings has been studied. The surface and cross-section morphologies before and after high-temperature oxidation test, chemical composition and phase identification of the coatings have been investigated by scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), and X-ray diffraction (XRD). The results show that the thickness and high-temperature oxidation kinetics of as-prepared Al2O3 coatings initially increase and then decrease, with the increase of deposition voltage from 110V to 150V and duty cycle from 40% to 80%. The minimum weight gain of only 0.495mg/cm2 after oxidation duration of 100h at 900°C can be achieved for the coatings formed with deposition voltage of 130V and duty cycle of 60%. The deposition mechanism of the coatings and effect of CPED parameters are also explained in this work.