Improvement of carbon steel resistance against high temperature oxidation and corrosion by flame sprayed FeCrAlTiY-30 mass% CoNiCrAlY coating using N2 pressure

Abstract

Flame spray technique with nitrogen pressure was used to deposit FeCrAlTiY-30 mass% CoNiCrAlY coating on the surface of low carbon steel. The resistance of the sample against oxidation and corrosion at high temperature was studied cyclically at 700oC for 8 times. The sample was rapidly heated in a furnace at 700oC for 20 hours and then cooled for 4 hours at room temperature. XRD and SEM-EDX were used to investigate the phase composition and morphologies of the coating before and after high temperature oxidation and corrosion test. For corrosion evaluation, the test samples was sprayed using 20 mass% NaCl solution. After the test, it was found that the flame sprayed FeCrAlTiY-30 mass% CoNiCrAlY coating with N2 pressure effectively enhances the resistance of carbon steel toward oxidation and corrosion at high temperature due to the formation of FeCr, Fe2O3, Al2O3, (Ni,Co)Cr2O4 and Al2O3, Fe2O3, Fe(Cr,Al)2O4, respectively. On the contrary, the coating was degraded more easily in 20 mass% NaCl containing atmosphere than in air atmosphere, suggesting that the corrosion attack is more severe than oxidation.