The Interface Structure of High-Temperature Oxidation–Resistant Aluminum-Based Coatings on Titanium Billet Surface

Abstract

A new type of high-temperature oxidation-resistant aluminum-based coating, on a titanium billet surface, was fabricated by the cold spray method, at a high temperature of 1050°C, for 8 h, under atmospheric pressure. The microstructure of the exposed surface was analyzed via optical microscopy, the microstructure of the coating and elemental diffusion was analyzed via field emission scanning electron microscopy, and the interfacial phases were identified via x-ray diffraction. The Ti–Al binary phase diagram and Gibbs free energy of the stable phase were calculated by Thermo-calc. The results revealed that good oxidation resistant 50-μm-thick coatings were successfully obtained after 8 h at 1050°C. Two layers were obtained after the coating process: an Al₂O₃ oxidation layer and a TiAl₃ transition layer on the Ti-based substrate. The large and brittle Al₂O₃ grains on the surface, which can be easily spalled off from the surface after thermal processing, protected the substrate against oxidation during processing. In addition, the thermodynamic calculation results were in good agreement with the experimental data.