Hot corrosion and cyclic oxidation performance of a PtAl2-dispersed (Ni,Pt)Al coating prepared by low-activity high-temperature aluminizing

The dual phase PtAl2-dispersed (Ni,Pt)Al coating (DP coating) and single phase (Ni,Pt)Al coating (SP coating) have been prepared simultaneously with an intermediate Pt content at the surface before low-activity high-temperature aluminizing process. Hot corrosion and cyclic oxidation performance of these two Pt-modified coatings are investigated in comparison with unmodified NiAl coating (UM coating). The results show that DP coating displays better hot corrosion resistance than SP and UM coating due to its higher Al content and faster Al diffusion rate in PtAl2 phase. The cyclic oxidation resistance of DP coating is comparable to SP coating, while lighter rumpling is achieved at the surface of DP coating. This is because the volume change accompanied by phase transformation from ζ-PtAl2 to β-(Ni,Pt)Al in DP coating is less than that from β-(Ni,Pt)Al to γ’-Ni3Al in SP coating. Moreover, ζ-PtAl2 is superior to β-(Ni,Pt)Al in creep resistance, which also qualifies DP coating with less rumpling than SP coating with the same residual stress.