Morphology and Microstructure of NiCoCrAlYRe Coatings after Thermal Aging and Growth of an Al2O3-Rich Oxide Scale

Abstract

Abstract:The surface of metal parts operating at high temperature in energy production and aerospace industry is typically exposed to thermal stresses and oxidation phenomena. To this aim, plasma spraying was employed to deposit NiCoCrAlYRe coatings on metal substrates. The effects of early-stage oxidation, at ~1100 °C, on their microstructure were investigated. The partial infiltration of oxygen through some open pores and microcracks embedded in coating microstructure locally assisted the formation of a stable Al2O3 scale at the splat boundary, while the diffusion of Cr and Ni and the following growth of Cr2O3, Ni(Cr,Al)2O4 and NiO were restricted to Al depleted isolated areas. At the same time, a continuous, dense and well adherent Al2O3 layer grew on the top-surface, and was somewhere supported by a thin mixed oxide scale mainly composed of Cr2O3 and spinels. Based on these results, the addition of Re to the NiCoCrAlY alloy is able to enhance the oxidation resistance.

Design of newly developed burner rig operating with hydrogen rich fuel dedicated for materials testing

“…The bond coat protects surface against oxidation and hot corrosion and might be formed from MCrAlYtype alloys (Zakeri et al, 2022) or by production of aluminide coatings (Góral et al, 2021;Kopec et al, 2021). For production of TBCs different method might be uses such as diffusion aluminizing (Cocojaru et al, 2022), atmospheric plasma spraying (Girolamo et al, 2014) or electron beam physical vapour deposition (EB-PVD) (Qiu et al, 2021). In new Environmental Barrier Coatings (EBC) the outer ceramic layer might contain different ceramic materials such as Y2SiO5-YS, Yb2Si2O7-YDS, Gd2Zr2O7, Y3Al5O12, Yb2Si2O7-YDS, Y2O3 produced using different thermal spraying processes (Vassen et al, 2019).…”

Failure mechanism of MCrAlY coating at the coating‐substrate interface under type I hot corrosion

“…MCrAlY coatings (M = Ni and/or Co) are widely used to protect the superalloys against high‐temperature oxidation and hot corrosion in gas turbine engines and also provide protection as a bond coat in thermal barrier coating system . Hot corrosion due to deposition of a thin film of fused salt accelerates the oxidation of a material at elevated temperature .…”

“…MCrAlY coatings (M = Ni and/or Co) are widely used to protect the superalloys against high-temperature oxidation and hot corrosion in gas turbine engines and also provide protection as a bond coat in thermal barrier coating system. [1][2][3][4][5][6][7][8] Hot corrosion due to deposition of a thin film of fused salt accelerates the oxidation of a material at elevated temperature. [9,10] There are two types of hot corrosion depending on the mechanism induced by corrosive salt: type I at "high" temperature between 850-1000°C [11,12] and type II at "low" temperature below 800°C.…”

Influence of oxidation temperature on the oxide scale formation of NiCoCrAl coatings

“…Further, oxidation resistance of several materials is very important for some high temperature applications. Coatings with sufficient amounts of aluminium or chromium can form an Al 2 O 3 or Cr 2 O 3 layer on their surface by reacting with oxygen, in order to protect the base material from interaction with the high temperature environment [4]. A dense, continuous, stable, and adherent either -Al 2 O 3 or Cr 2 O 3 scale is always desirable because it offers excellent protection for the substrate due to its slow growth rate and thermodynamic stability at high temperatures [5].…”