Core-multishell globular oxidation in a new TiAlNbCr alloy at high temperatures

Abstract

Oxidation resistance is one of key properties of titanium aluminide (TiAl) based alloys for high-temperature applications such as in advanced aero-engines and gas turbines. A new TiAlNbCr alloy with micro-addition of yttrium has been developed, but its oxidation behavior is unknown. To provide some fundamental insights, high-temperature oxidation characteristics of this alloy are examined via scanning electron microscopy, transmission electron microscopy, electron probe microanalysis, and X-ray diffraction. We show that distinctive core-multishell globular oxidation and “daisy” flower-like oxidation occur exclusively around Y2O3 particles. Globular oxides exhibit multi-layered Y2O3/TiO2/Al2O3-rich/TiO2-rich shell structures from the inside to outside. Flower-like inner oxides consist of core Y2O3 particles surrounded by divergent Al2O3 and oxygen-rich α2-Ti3Al in the near-scale substrate. As the scale-substrate interface moves inward, the inner oxide structures suffer deeper oxidation and transform into the globular oxide structures. Our results demonstrate that the unique oxidation characteristics and the understanding of formation mechanisms pave the way for the exploration and development of advanced oxidation-resistant TiAl-based materials.

Site Occupation of Nb in γ-TiAl: Beyond the Point Defect Gas Approximation

“…0.5 at.% C and Cr increase the strength and ductility of TiAl [10][11][12]. W and Y increase oxidation resistance of TiAl [13,14]. C and Si enhance the creep properties of TiAl [15,16].…”

Bulletin of the Polish Academy of Sciences: Technical Sciences

“…The sample is placed in the vacuum process chamber at various distances from the nozzle and fixed with holders of samples (4). The products of electric explosion are a multiphase system, comprising both plasma component (Al) and condensed particles with different dispersion (Y 2 O 3 ), which set on the surface of the treated product and form a multicomponent coating (8). A supersonic front edge of the jet flowing over the surface The findings of local micro X-ray spectral analysis of a particular inclusion are given in Table 2.…”

Critical Raw Materials Saving by Protective Coatings under Extreme Conditions: A Review of Last Trends in Alloys and Coatings for Aerospace Engine Applications

“…In 2006, General Electric announced the use of Ti-48Al-2Nb-2Cr (Ti-48-2-2), for making low pressure turbine (LPT) blades for their GEnx™ engine, being the first time that a TiAl alloy was employed for rotating parts of a commercial aircraft engine. This alloy, was successful used in high-thrust GEnx jet engines for LPT blade materials in Boeing 747-8 and 787 Dreamliner, entered into commercial service in 2012 in substitution of Ni-based superalloys in the temperature range of 650–750 °C with the benefit of a weight reduction of about 50% [ 77 ]. GEnx engine allows up to 15% improved fuel efficiency, 15% less CO 2 compared to GE’s CF6 engine, and about 30% of noise reduction [ 78 ].…”

“…Moreover, in view of a wider application of titanium alloys in aerospace engines at elevated temperatures, the threat of oxidation should be prevented. Unlike Ni- based superalloys, Ti-based superalloys lack, in fact, the formation of an Al 2 O 3 scale and the degradation of Ti-based alloys is characterized by the formation of a rapidly growing scale of rutile TiO 2 or TiO 2 + Al 2 O 3 mixtures and a brittle oxygen-rich sublayer underneath the oxide scale with enhanced attitude to cracking [ 77 , 183 ].…”