Improved hot corrosion resistance of Dy-Co-modified aluminide coating by pack cementation process on nickel base superalloys

Dy-Co-modified aluminide coating was deposited onto Ni-based superalloy DZ125 using pack cementation method. The microstructure and hot corrosion behavior of the coating were investigated. The results show that as-deposited coating has a two-layer structure. The outer layer of the coating is composed mainly of Al_0.9Ni_1.1 with dispersed Dy₂Hf₂O₇. The mass gain of the coating is 0.23 mg/cm² after exposure to 75 wt.% Na₂SO₄ + 25 wt.% NaCl at 900 °C for 100 h. The corrosion product formed on the coating is characterized as Al₂O₃. Role of Dy in the improvement of the hot corrosion resistance has been discussed.