MCrAlY和AlCoCrFeNi高熵合金黏结层制备与研究进展OA

With the continuous development of aeroengines and gas turbines,the temperature of hot-section components keeps rising with the improvement of performance.To enhance the service performance and prolong the lifespan of hot-section components under high temperature conditions,thermal insulation measures such as superalloys,cooling systems,and thermal barrier coatings(TBCs)must be adopted.However,the mechanical properties of superalloys deteriorate significantly above 1 100℃,and film cooling reduces engine efficiency.TBCs can overcome high-temperature limitations and deliver greater benefits.TBCs consist of a superalloy substrate,a bond coating(BC),a thermally grown oxide layer(TGO,primarily α-Al2O3),and a top coat(TC)ceramics.The TGO inevitably forms between the BC and TC at high temperature conditions,serving as the true bonding interface for the TC.Its characteristics and thickness directly determine the lifetime and failure mechanisms of TBCs.The high-temperature failure causes of TBCs include:(1)thermal stress induced by coefficient of thermal expansion(CTE)mismatch between BC and TC;(2)erosion caused by high-velocity particle impact;and(3)corrosion from CaO-MgO-Al2O3-SiO2(CMAS)particles in the atmosphere.These mechanisms are primarily related to the TC;therefore,the TC must possess low thermal conductivity,excellent high-temperature chemical stability,high thermal shock resistance,erosion resistance,high melting point,high CTE,and good fracture toughness.As the first coating layer in TBCs,the BC plays a critical role in enhancing adhesion between the TC and the substrate and preventing high-temperature oxidation of the alloy substrate,because the TC has a porous structure with high oxygen diffusivity.Under elevated temperature conditions,wrinkling,oxidation deformation,and aluminum depletion of the BC exacerbate thermal stress between the BC and the TC,leading to cracking and reduced bonding strength.In industrial practice,MCrAlY(M=Ni or/and Co)coatings are commonly used as bond coatings,where Cr and Al enhance oxidation and hot corrosion resistance,while the Y element improves the bonding strength of the oxide layer.However,as inlet temperatures continue to rise,conventional MCrAlY bond coatings suffer from rapid TGO growth and degraded interfacial adhesion when operating above 1 100℃,providing insufficient oxidation resistance.Therefore,there is an urgent need to develop new bond coating materials with higher temperature capability to break through the temperature limitations of conventional MCrAlY bond coatings.In recent years,high-entropy alloys(HEAs)have attracted considerable attention due to their unique compositions and superior properties.HEAs are originally defined as multi-component alloys containing five or more alloying elements,each added in equiatomic proportions with concentrations between 5%to 35%.Current research has extended this to simple solid solutions where the elemental composition is no longer limited to at least five principal elements,while the atomic fraction of each element remains at 5%to 35%.As a novel alloy system,HEAs possess a multi-principal-element structure and exhibit synergistic effects including high-entropy,sluggish diffusion,severe lattice distortion,and a"cocktail"effect.These break the inherent performance trade-offs of conventional alloys,demonstrating high hardness,superior heat resistance,strong corrosion resistance,excellent wear resistance,and oxidation resistance.Under high temperature conditions,HEAs can promote the formation of continuous,dense,and uniform TGO while regulating interdiffusion between the bond coating and the substrate,showing great potential as bond coating materials.The selection of bond coatings is crucial for TBCs performance.This paper separately introduces MCrAlY and AlCoCrFeNi HEAs bond coatings through composition design,high-temperature oxidation resistance,and modification methods,and summarizes the high-temperature oxidation performance and modification mechanisms of both bond coating types.It points out that conventional MCrAlY bond coatings operating above 1 100℃lead to rapid TGO growth and interfacial adhesion degradation,failing to provide adequate high-temperature oxidation resistance.In contrast,AlCoCrFeNi HEAs bond coatings can form a protective α-Al2O3 scale at 1 100℃,exhibiting oxidation behavior similar to MCrAlY bond coatings.Compared with MCrAlY bond coatings,AlCoCrFeNi HEAs demonstrate superior thermal stability,higher hot hardness,lower thermal conductivity,and smaller coefficient of thermal expansion.The review also covers several preparation processes,summarizing the effects of processing flow and parameters on bond coating structure and properties.Within the HEAs bond coating system,AlCoCrFeNi HEAs further exhibit excellent oxidation resistance,thermal stability,and mechanical properties due to their unique characteristics.Therefore,AlCoCrFeNi HEAs bond coatings are promising candidates to replace conventional MCrAlY bond coatings in high-temperature environments.Finally,future research directions for bond coating composition design and preparation processes are proposed.