The synthesis of nanostructured NiCrAlY powders for plasma sprayed thermal barrier coatings

Abstract

Thermal barrier coatings (TBCs) are used to protect hot sections of industrial gas turbine blades against high temperature corrosion and oxidation. They usually consist of a thermally insulating ceramic top layer (Yittria Stabilized Zirconia or YSZ) and an oxidation resistant metallic bond coat (MCrAlY) thermally sprayed onto the nickel-based superalloy substrate surfaces. Currently MCrAlY powders, up to 100µm in diameter are used in the production of thermal barrier coatings by the industrial gas turbine component manufacturers. It has been found that the nanocrystalline MCrAlY layer provide better oxidation behavior than the currently used microstructured MCrAlY layer at elevated temperatures. In this research work, nanocrystalline NiCrAlY powders were manufactured using a conventional Ni22Cr10Al1.0Y powder as the base material using a planetary ball mill device. The microstructural characterization of NiCrAlY powders before and after milling were explored using X-ray diffraction, scanning electron microscope equipped with energy dispersive spectrometer. The results indicated that the synthesized NiCrAlY powders mainly consists of two phases: ? (Ni,Cr-rich) and ?^’ (Ni₃Al) .

Key words: MCrAlY powders, High temperature oxidation, Ball milling, Air-plasma sprayed coatings.