Investigation of kinetics behavior high temperature isotherm oxidation MCrAlY coatings applied by HVOF method

Today, in Power plant industry, especially gas turbine hot corrosion and oxidation resistance of high temperature superalloys used. These superalloys good resistance to attack and entry of hot gases and ash fines resulting from fuel combustion, as well as atmospheric corrosion of the show. As a result of these superalloys used in Power plant industry, especially are considering today. The thermal spray coating on these superalloys can be hot corrosion resistance and high temperature oxidation increase. In this research isothermal oxidation behavior of CoNiCrAlY coating and kinetic of growth thermally grown oxide layer (TGO) was investigated. For deposit of the CoNiCrAlY Amdry 9954 coating on superalloy nickel-base (Inconel 738) substrate used to the high-velocity oxygen-fuel (HVOF) technology. These specimens coatings were oxidized at 1100°C for 5 upto 100 h in a normal electric furnace under air atmosphere. The test specimens were examined using scanning electron microscope (SEM) and energy dispersive spectrometry analysis (EDS) together with the X-ray diffraction (XRD) analysis. Microstructural characterization showed that the growth of continuous and uniform TGO scale onto bond coat. Also, in oxidation process observed the formation of mixed oxides (as spinel) CoCo2O4 and Ni(Cr,Al)2O4 and CrO3 and Y3Al5O12 onto Al2O3 (TGO layer).