Cathode electrolytic plasma deposition of (Al0.9Cr0.1)2O3/γ-Al2O3 composite coatings onto Ti45Al8.5Nb0.1Y0.2W alloys for high-temperature applications

Abstract

The anti-oxidation properties of TiAl-based alloys at above 900 °C are of particular interesting for high-temperature applications. Here, novel (Al0.9Cr0.1)2O3/γ-Al2O3 composite coatings have been fabricated on the surface of Ti45Al8.5Nb0.1Y0.2W alloys by cathode electrolytic plasma deposition technique (CEPDT). The effects of as-prepared composite coatings on the microstructure and long-term oxidation behavior of Ti45Al8.5Nb0.1Y0.2W alloys are investigated through X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersion spectrometry (EDS), and isothermal oxidation measurements. Benefited from Cr3+ doping at the Al3+ sites of Al2O3, there shows a much denser structure for the (Al0.9Cr0.1)2O3/γ-Al2O3 composite coatings than single γ-Al2O3 coatings. This favors the decrease of weight gain into 0.773 mg/cm2 for CEPDT-modified alloys with the composite coatings after overall oxidation of 720 h at 900 °C, as compared to mass gains of 3.213 mg/cm2 and 2.331 mg/cm2 for pristine alloys and CEPDT-modified alloys with γ-Al2O3 coatings. It is also found that the microstructural characteristics of the composite coatings after oxidation shows much favorable impact on high-temperature application of TiAl-based alloys in a protective way.