Nickel Base Superalloy Rene®80 – The Effect of High Temperature Cyclic Oxidation on Platinum-Aluminide Coating Features

Nickel base superalloy alloys are used in the manufacture of gas turbine engine components, which in use are exposed to high temperatures and corrosive environments. The platinum aluminide coatings described here have been developed to protect nickel base superalloy alloys from oxidation. In this study, the effect of cyclic oxidation, platinum layer thickness and aluminizing process on behavior of Pt-Aluminide (Pt-Al) coating on nickel-based superalloy Rene®80 have been investigated. For this purpose, after applying different thicknesses of Pt-layer (2, 6 and 8µm), diffusion aluminide coating in two types, high temperature-low activity (HTLA) and low temperature-high activity (LTHA) methods was performed. The results of microstructural investigations by Scanning Electron Microscopy and the X-ray diffraction analysis indicated that coatings include three zones in all thicknesses of the platinum layer and in both methods of aluminizing. The results of cyclic oxidation (1100 °C and 120 cycles) test showed that Pt-Al in all conditions improved the oxidation resistance of Rene®80. The best oxidation resistance is related to the specimen coated with 6 µm Pt by LTHA method, whereas the lowest resistance was related to 2µm Pt in the case of HTLA method. The weight changes during cyclic oxidation of 6µm Pt (LTHA) and 2µm Pt (HTLA) coatings were 3.8 and 6 mg, respectively. Also, the parabolic oxidation rate constants of these coatings were calculated as 1.5*10-12 and 3.8*10-12, respectively.