Oxidation behaviour of platinum modified aluminide coatings deposited by CVD method on nickel-based superalloys under air atmosphere

Purpose: In this paper the oxidation resistance of platinum modified aluminide coating deposited by CVD method on nickel-based superalloy was evaluated. Design/methodology/approach: Platinum coatings 3 and 7 ^m thick by the electroplating process were deposited. The heat treatment of electroplating coatings at the temperature 1050°C for 2 h under argon atmosphere was performed. Low activity CVD aluminizing process of platinum heat treated coatings (3 and 7^m thick) at the 1050°C for 8 h using IonBond equipment was performed. Oxidation resistance at 1100°C for 1000 h in air atmosphere using furnace of Czylok company was evaluated. The microstructure investigations of platinum and palladium modified aluminide coatings were conducted by the use of optical microscope (Nikon Epiphot 300) and a scanning electron microscope (Hitachi S-3400N) equipped with an Energy Dispersive Spectroscope EDS (VOYAGER of NORAN INSTRUMENTS). The phase composition was identified by X-ray (ARL X’TRAX) diffractometer. The surface roughness parameter -Ra of modified aluminide coatings was evaluated by Perthometer S2 MAHR equipment. Findings: The microstructure of platinum modificated aluminide coatings (3 and 7 m thick) consists of (Ni,Pt)Al phase and two zones: outer and internal one. Low activity CVD aluminizing at 1050°C for 8 h causes the increase of surface roughness parameter of modified coatings. The increase of platinum thickness from 3 to 7 μm lets to get a greater surface roughness parameter of aluminide coatings. On the ground of the obtained results, it was found that platinum modification of aluminide coatings provides to increase of oxidation resistance Ni-based substrates. Practical implications: The platinum modified aluminide coatings are widely used as coatings for turbine blades of aircraft engines. Originality/value: It was proved that platinum modification of aluminide coatings has a positive effect on the oxidation resistance of substrate.