Abstract
The application of protective aluminide coatings is an effective way to increase the oxidation resistance of the treated parts and prolongs their lifetime. The addition of small amount of noble metals (platinum or palladium) or reactive elements such as: hafnium, zirconium, yttrium and cerium has a beneficial effect on oxidation behavior. This beneficial effect includes an improvement of adhesion of alumina scales and reduction of oxide scale growth rate. Platinum and hafnium or zirconium modified aluminide coating were deposited on pure nickel using the electroplating and CVD methods. The coatings consisted of two layers: an outer, β-NiAl phase and the interdiffusion γ’-Ni3Al phase. Palladium dissolved in the whole coating, whereas hafnium and zirconium formed inclusions on the border of the layers. Samples were subjected to cyclic oxidation test at 1100 °C for 200h. Oxidation resistance of the palladium, Hf+Pd and Zr+Pd modified coatings deposited on pure nickel does not differ significantly, but is better than the oxidation resistance of the non-modified one.
Highlights
Protective aluminide coatings, characterized by low density, high melting point and oxidation resistance, are deposited on superalloys as bond coats in thermal barrier coatings (TBC) [1]
That has been achieved by alloying them with small amount of noble metals or reactive elements
3.1 Palladium modified aluminide coating on pure nickel
Summary
Protective aluminide coatings, characterized by low density, high melting point and oxidation resistance, are deposited on superalloys as bond coats in thermal barrier coatings (TBC) [1]. This way the scale adhesion is improved and the growth rate of the scale is reduced. Zirconium forms nanoparticles in aluminide coatings on pure nickel [13]. After oxidation, it is homogeneously distributed within the scale, delays spallation and improves adhesion [14]. “Co-doping” - the idea of using more than one dopant is a promising way for improvement of oxidation resistance of coatings [11,15]. This paper presents analysis of oxidation resistance of the Pd+Hf and Pd+Zr co-doped aluminide coatings deposited on pure nickel
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