Structure and composition of MCrAlY coatings modified by Al additions

Plasma spray techniques have been used to increase the Al content on existing NiCoCrAlY films in order to obtain high temperature resistant coatings on Ni-base superalloys for gas turbine applications. Surface alloying has been produced by thermal diffusion under vacuum of the Al and MCrAlY films. This treatment reduces the surface roughness and increases the coating density by sealing its porosity. The aluminides formed have been analyzed in terms of their structural composition and oxidation resistance. Al additions are effective in reducing the oxidation rates, in particular for the MCrAlY coatings which are APS deposited. By increasing the temperature over 1100 °C, the coating efficiency rapidly decreases.