MCrAlY coating developed via a new electroless-like route: influence of deposition parameters

Abstract

Improvement in efficiencies of gas turbines can be achieved by increasing the gas inlet turbine temperature. This leads to increased blade and vane temperatures and therefore to enhanced oxidation and corrosion attack of the coatings on these components. Coatings such as MCrAlY are typically used to improve components’ high temperature properties. Various processing routes have been studied to produce MCrAlY coatings including plasma spray and electrolysis methods. Plasma spray is convenient and permits a large range of MCrAlY composition to be obtained but the directionality of the process leads to non-uniformity of the coating thickness distribution. More recently, an electrolytic route has been developed using sulfamate or sulfate baths, which cause contamination of the coatings and has a detrimental effect on the adherence of the protective oxide scale. A potentially attractive processing route is the electroless autocatalytic process, since this has the advantage of permitting non-directional and sulfur-free deposition. We have investigated MCrAlY deposition by an electroless-like autocatalytic process. Coatings were deposited on a single crystal nickel-based alloy (MC-NG) and the differences in microstructure and phase composition according to the different process stages are reported. The influence of process parameters on the coating characteristics is discussed.