Corrosion resistance by HVOF coating on gas turbine materials of cobalt based superalloy

Abstract

Abstract In the parts of gas turbines, external degradations such as corrosion occur at places like turbine blades, when the temperature is high. The turbines become less operative and flare with sound because of the degradation due to corrosion. The thermocyclic hot corrosion performance of the 25%(Cr3C2-NiCr) + 75%NiCrAlY coatings as well as the cobalt based super alloy (Superco-605) substrate alloy was studied in a molten salt environment of Na2SO4 −50%V2O5 at 750 °C for 50 cycles. Each cycle consists of an hour heating followed by 20 min of cooling, in room temperature environments. The response and kinetics were studied by means of thermogravimetry. The samples subjected to corrosion will be investigated using techniques of Optical microscopy, X-ray diffraction (XRD), Scanning electron microscopy/Energy dispersive X-ray analysis (SEM/EDX) and Electron probe microanalysis. The major phases observed on coated material shows the formation of oxides of Chromium Oxide (Cr2O3), Nickel Oxide (NiO), and Aluminium oxide (Al2O3) which gives high protection against corrosion and prevents the penetration of corrosive species into the coating.