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Abstract
High temperature oxidation occurs in many equipments ranging from gas turbines, boilers, heat treating retorts to heat exchangers. Superalloys are used for such applications due to their excellent mechanical properties and creep resistance, but lack resistance to oxidation. In the present investigation, Al2O3–40TiO2 coating has been deposited on nickel and cobalt based superalloys by low velocity oxyfuel (LVOF) process. The coating has been characterised for scanning electron microscopy (SEM), X-ray diffraction (XRD) and surface roughness. The high temperature oxidation behaviour of coated and uncoated superalloys has been evaluated at 800°C for 50 cycles of one hour duration. The LVOF coating has shown good adherence to the substrate. AE 435 superalloy has shown the highest weight gain amongst the tested materials, whereas Al2O3–40TiO2 coated Superco 605 superalloy has shown the lowest weight gain. The better oxidation resistance of Al2O3–40TiO2 coating might be attributed to the presence of protective Al2O3 phase along with TiO2 phase in it.