High Temperature Oxidation Resistance of FeCrAlTiY-MCrAlY (M = Co and Ni) Coatings On Carbon Steel Prepared By Flame Spray Technique

Four different composition of FeCrAlTiY-x MCrAlY (M = Co and Ni, x = 0, 10, 20, and 30 in mass %) coatings were prepared onto carbon steel substrate using a flame spray technique. The high temperature oxidation resistance of the coating and uncoated samples was studied cyclically at 700°C for 8 times. X‑ray diffraction (XRD) and scanning electron microscope equipped with energy dispersive X-ray spectrometer (SEM-EDX) were used to investigate the phase composition and morphologies of the coating before and after oxidation. Depending on the coating composition, the coatings are composed of FeCr, Fe(Cr,Al)2O4, (Co,Ni)Cr2O4 and FeO. After high temperature oxidation test, it was found that the carbon steel experienced high oxidation rate at the aforesaid temperature, forming a thick Fe-oxides layer. Even if a protective Al2O3 or Cr2O3 layer is not formed on the coating surface, the flame sprayed FeCrAlTiY–MCrAlY coatings effectively improve the resistance of carbon steel toward oxidation at high temperature due to the formation of Fe2O3 and spinel oxides. According to the results, the 30 mass % MCrAlY coating exhibited a lowest mass gain after exposure at 700°C for 8 cycles.