Effect of Y2O3 content in the pack mixtures on the cyclic-oxidation of Y2O3-modified low temperature aluminide coatings on 309 stainless steel

By using Y2O3 nanoparticles, instead of part or all of Al2O3, acting as filler, Y2O3-modified aluminide coatings were produced on 309 stainless steel using a conventional pack-cementation method at 700 °C for 6 h. Effect of Y2O3 content in the pack mixtures on the cyclic-oxidation resistance of different aluminide coatings was comparably investigated. The results show that the phase of aluminide coatings was Fe24Al76.8. With the increase of Y2O3 content in the pack mixtures, the thickness of aluminide coatings decreased but the cyclic-oxidation resistance at 900 °C in air increased, because of prevention of cavities at the alumina scale/coating interface, and because of mitigation of degradation of the aluminide coating due to decreased outward diffusion and inward interdiffusion between the aluminide and the 309 stainless base. The reasons for the results are discussed.