Microstructural characterization of gas phase aluminized TiAlCrNb intermetallic alloy

Abstract

This article presents a microstructure characterization of an alloy coating based on Ti-48Al-2Cr-2Nb-type γ + α 2 intermetallic phases deposited via an out-of-pack aluminizing process. The goal of the aluminizing process was to obtain a coating composed of aluminum-rich TiAl 2 or TiAl 3 phases with greater oxidation resistance compared to the base alloy. The results showed that the gas-phase aluminizing process produced a coating with specific microstructural properties. The thickness of the layer obtained, including the transition zone, was approximately 20 μm. X-ray diffraction (XRD) phase composition studies demonstrated that the outer coating zone was primarily composed of a TiAl 2 phase, and its thickness was approximately 10 μm. Microanalysis of the chemical composition showed that, in addition to the main components, i.e. titanium and aluminum, chromium and niobium were present in the outer coating. Electron backscatter diffraction (EBSD) studies further indicated the probable presence of a TiAl 2 phase. The coating obtained was of good quality, and cracks or pores, which are typical of coatings obtained via powder methods, were not detected.