Hot Corrosion Behavior of Pt Modified Gradient NiCrAlY Coatings
For further enhancing the hot corrosion resistance of the NiCrAlY coating,the NiCrAlY/NiAl/Al coating(coating A)and the NiCrAlY/Pt/NiAl/Al coating(coating B)were deposited on the surface of DZ125 alloy by arc ion plating technology,and then the gradient coating structure with gradually changing composition was formed by vacuum diffusion annealing.The modified element Pt was introduced into the coating to enhance the hot corrosion resistance of the coating,and the hot corrosion behavior of two coating systems in different mixed salts at 900 ℃ was studied.Additionally,the microstructure,phase composition and element distribution of the coating after hot corrosion were ana-lyzed by SEM,EDS,XRD and EPMA.Results showed in a mixed salt of K2SO4+Na2SO4 at 900 ℃,the extensive spalling of the oxide film occurred on the surface of coating A.Pt in coating B inhibited the segregation of S at the coating/oxide film interface,and enhanced the adhe-sion of the oxide film.In the mixed salt of NaCl+Na2SO4 at 900 ℃,the Cr element and O element of coating A underwent outward diffusion and inward diffusion,respectively.The outward diffusion of Cr was easy to react with S to form a harmful phase CrxSy.In contrast,the Pt in coating B inhibited the outward diffusion and inward diffusion of Cr and O elements.Overall,the addition of Pt layer between NiCrAlY and NiAl layers significantly enhanced the hot corrosion resistance of the NiCrAlY coating in mixed salts.
arc ion platinggradient NiCrAlY coatingα-CrPt modifiedhot corrosion
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