Effects of High Al Content On the Phase Constituents and Thermal Properties in Nicocraly Alloys

Abstract

MCrAlY (M = Ni and/or Co) metallic coatings are essential for the protection of hot-end components against thermal and corrosion damage. Increasing the Al content is considered a feasible solution to improve the high temperature performance of MCrAlY coatings. In this paper, the effects of high Al contents (12 – 20 wt.%) on the phase constituents and cast microstructures in MCrAlY alloys were studied by high-energy X-ray diffraction and electron microscopy techniques combined with phase equilibria calculations. High Al content improved the stability of β, σ, and α phases. Meanwhile, an evolution of cast microstructure morphology from dendrite structure to equiaxed grain structure was observed. The thermal properties were analyzed, which were closely related to the phase constituents and solid-to-solid phase transitions at evaluated temperatures. This work is instructive for developing high Al content MCrAlY coatings for next generation thermal barrier applications.

Keywords: Thermal barrier coatings, Solidification behavior, Phase constituent, Thermal property