Investigation of phase transformations in a two-layer Ti–Al–C+Y–Al–O coating on a heat-resistant nickel alloy

Abstract

Currently, an active increase in requirements for fuel efficiency and specific gravity of aircraft turbojet engines is observed. Existing coatings based on zirconium dioxide intended for protecting engine parts are largely outdated and have exhausted their development potential, so new ceramic systems for the production of protective coatings based on them are an area of research. The authors carried out a study of a heat-resistant two-layer coating based on the Y–Al–O system (outer layer) and the Ti2AlC MAX phase of the Ti–Al–C system (sublayer) produced using vacuum-arc deposition on the Inconel 738 heat-resistant nickel alloy and molybdenum by alternate deposition of layers based on Ti–Al–C and a Y–Al–O layer. Using synchrotron radiation, phase transformations in the coating were examined when samples were heated to 1400 °C in a vacuum and to 1100 °C in the atmosphere to study the process of oxidation and coating formation in the presence of oxygen. Using scanning electron microscopy, the authors studied the microstructure and chemical composition of the coating. The study identified that heating the coating in a vacuum and in the atmosphere causes various phase transformations in it, but in both cases, the formation of a mixture of oxides of the Y–Al–O group and destabilization of the Ti–Al–C-based sublayer are observed. After heating the coating in the atmosphere without preliminary heat treatment, the coating was destroyed upon cooling, which was not observed when the coating was heated in a vacuum.

Keywords

• heat-resistant coating
• ceramic coating
• max phase
• yttrium oxide
• vacuum-arc deposition
• synchrotron radiation