Hot corrosion behavior of Pt-Ir modified aluminide coatings on the nickel-base single crystal superalloy TMS-82+

Platinum-iridium films (Ir = 0, 32, 46, 83, 100 at.%) were deposited on the nickel-base single crystal superalloy through magnetron sputtering. After annealing and aluminizing, the Pt-Ir modified aluminide coatings mainly consisted of PtAl₂ and β-(Ni,Pt,Ir)Al phases. Hot corrosion resistance of Pt-Ir modified aluminide coatings with the different Ir contents were evaluated by exposure at 1173 K in the presence of the 90%Na₂SO₄ + 10%NaCl (wt%) salt deposits. The corrosion kinetics curves of the specimens were plotted up to 100 h heating time. The phase constitution, morphology of corrosion products, and element concentrations along the cross section were also measured. The lowest mass gain (0.299 mg/cm², after 100 h) was observed for Pt-46Ir aluminide coating because the dense and continuous protective Al₂O₃ scale formed. Phase transformation from β-(Ni,Pt)Al to γ′-(Ni,Pt)₃Al, characteristics of the scale, and protection by Pt/Ir enriched layer had the important effects on the hot corrosion behavior of modified aluminide coatings.