Development and Evaluation of Chromium- Modified Aluminide Diffusion Coating


AbstractIn this work nickel superalloy Inconel 600 was coated with two different types of coatings Cr modified aluminide coating this is called(Aluminizing- Chromizing) and Y-doped Cr modified aluminide coating this is called (Aluminizing- Chromizing- Yttriumizing) using pack cementation method. Diffusion coating was carried out in one step process by simultaneous aluminizing –chromizing process and by simultaneous aluminizing- chromizing- yttriumizing process using the conversion reaction of 10 wt.% Cr2O3, 10 wt.% Al, 2 wt.% NH4Cl, 4 wt% NaCl and 72 wt.% Al2O3 and 2% Y2O3 when required. The diffusion coating processes were carried out at 1050 oC for 8hrs. After diffusion coating the coating layer was found to be consisted of: -NiAl.Cyclic oxidation test in air was conducted on the Inconel 600 coated with Cr-modified aluminide coating and on the Inconel 600 alloy coated with Y-doped Cr modified aluminide coating in the temperature range 700- 1100 oC. The oxidation cycles include 10 hrs. at furnace temperature. The results indicate that Y-doped Cr modified aluminide coating is more effective in increasing the oxidation resistance of Inconel 600 alloy. The role of yttrium can be attributed to an improvement of the adherence of the oxide scales.