Oxidation Behavior of AISI 316 Steel Coated with Ni-P-TiO2-Al2O3 Composite Coating

Austenitic steels have numerous applications in high-temperature environments. The thermally-grown chromia scale on the steel surface may become unstable at high temperatures and as a result, oxidation resistance of steel will decrease. A potential method for improving oxidation properties is the use of composite coatings using techniques such as electroplating. In the present study, Ni-P-TiO2-Al2O3 composite coating was deposited on AISI 316 steel substrate by electroplating. The as-coated samples were examined with scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). X-ray diffraction (XRD) was also used to identify the formed phases in the as-coated structures. To evaluate oxidation behavior, isothermal oxidation, and cyclic oxidation were con-ducted at 800 ºC. Isothermal oxidation of uncoated steels revealed higher weight gain in comparison with Ni-PTiO 2-Al2O3 composite-coated samples. The coating layer limited the outward diffusion of Cr cation and the inward diffusion of oxy-gen anion and resulted in a better oxidation resistance. According to the results of cyclic oxidation, coated substrates demonstrated excellent resistance against spallation and cracking.