Oxidation Properties in CO2 of Inconel Alloy 600 Coated by Simultaneous Aluminizing-Chromizing Process

IN 600 alloy was coated with two different types of coatings, Cr-modified aluminide coating this is called aluminizing-chromizing and Y-doped chromium modified aluminide coating this is called aluminizing-chromizing-yttriumizing. Diffusion coating was carried at 1 050 °C for 8 h under Ar atmosphere by simultaneous aluminizing-chromizing process and by simultaneous aluminizing-chromizing-yttriumizing. Cyclic oxidation tests were conducted on the uncoated and on the coated Inconel 600 alloy in the temperature range 800–1 000 °C in CO2 for 100 h at 10 h cycle. The results showed that the oxidation kinetics for uncoated Inconel 600 alloy in CO2 is parabolic and the phases present are NiO, (Fe, Cr)2O3, NiFe2O4 and NiCrO4. The oxidation kinetics for both coated systems in CO2 was found to be parabolic and the value of kP for both coated systems were found to be lower than that for uncoated Inconel 600 alloy. Oxide phases that formed on coated systems are Al2O3 and NiCrO4. The role of yttrium can be attributed to its ability to improve the adherence of the oxide scale.