The effect of the MCrAlY composition and aluminizing cycle upon the microstructure and hot corrosion resistance of the over‐aluminized MCrAlY coating on IN738LC alloy substrate

Abstract

The aluminizing behavior of high-velocity oxy-fuel sprayed CoNiCrAlY, or NiCoCrAlY-coated IN738LC alloy has been investigated via asingle or two-step pack cementation aluminizing processes. The microstructural study showed that a more desirable low aluminum-containing MCrAlY coating is obtained through single-step aluminizing. The resultant over-aluminized coating microstructure consisted of the Co-containing beta-NiAl in the aluminide top layer and the Ni−Co−Cr-based austenitic gamma solid solution matrix decorated with the Co-containing beta-NiAl islands in the MCrAlY zone.

Recent Advances in the Deposition of Aluminide Coatings on Nickel-Based Superalloys: A Synthetic Review (2019–2023)

“…It has been reported that the NiAl coatings doped with zirconia [18][19][20] and hafnium [21] also reduce the oxidation rate of nickel-based superalloys since the addition of these elements leads to the formation of stable oxides, inhibiting aluminum depletion. Other significant studies report that a functional NiCoCrAlY coating improves the hot-corrosion resistance of Inconel 738L exposed to air for 100 h at 700 • C [22]. It is worth mentioning that aluminide coatings also improve the high-temperature corrosion resistance of Inconel 718 in a salty environment [23].…”

“…NiAl + Hf/PC Formed HfO2 acts as a diffusion barrier to prevent inter-diffusion during cyclic oxidation; the surface rumpling extent is much relieved due to a slower Al depletion rate and higher creep resistance by Hf addition [21] Inconel 738L NiCoCrAlY/PC Improved hot-corrosion resistance at 700 °C [22] Inconel 718 NiAl/PC Aluminized surface reduced the hot corrosion by 50% at 700 °C in an NaCl environment [23] Nickel Ni2Al3/PC Ultrafine-grained Ni2Al3 coating significantly enhances the oxidation resistance in air at 900 °C [24]…”

“…Interestingly, the most frequently modified nickel-based alloys are those with the highest oxidation resistance, possessing high mechanical strength. These involve Rene 80 [8,18,63], Inconel 625 [13,57,58], Inconel 713 [39,40,52], Inconel 718 [41], Inconel 738L [11,19,22,36,45,59,61,65,68] and CMSX-4 [17,30,42,44,46]. One should highlight that the research involving conventional nickel-based superalloys is mainly dedicated to future high-temperature applications.…”

“…A summary of the pack cementation-related research[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24].…”