Study On The Interface Interdiffusion Behavior Of NiAlRu-nickel Based Superalloy And Phase Equilibria Of The Related System

In order to cope with the increasingly harsh working environment,nickel-based superalloys must be used with high-temperature protective coatings,but there is a serious interdiffusion of elements between the coating and the substrate,which affects the service effect of superalloys.The Ru-modified aluminide coating can slow down the Al diffusion rate and inhibit the interdiffusion of elements between the coating and the substrate.Therefore,the research on the interface interdiffusion behavior between the Ru-modified aluminide coating and the substrate is helpful to guide the composition design of the coating.In this work,the interface interdiffusion behavior of Ni Al Ru alloy-nickel based superalloy was studied by solid-solid diffusion couple method and the isothermal section of Al–Cr–Ru ternary system at 950℃was measured by equilibrium alloy method,and characterized by SEM,EDS,XRD and other means,and the main conclusions are as follows:1.Thirteen three-phase regions exist in the isothermal section of the Al–Cr–Ru ternary system at 950℃,and eleven three-phase regions were experimentally determined Al Ru+Cr₂Ru+Cr₃Ru,（Ru）+Al Ru+Cr₂Ru,Al Ru+Cr₃Ru+（Cr）,Al Ru+Al₂Ru+（Cr）,（Cr）+Al₂Ru+α-Al₈Cr₅,Al₂Ru+Al₁₃Ru₄+α-Al₈Cr₅,Al₁₃Ru₄+α-Al₈Cr₅+τ₂,τ₂+τ₁+Al₄Cr,τ₂+τ₁+Al₁₃Ru₄,τ₁+Al₄Cr+L-Al,τ₁+Al₁₃Ru₄+L-Al.Two three-phase region are inferred:α-Al₈Cr₅+τ₂+Al₄Cr,Al Ru+Al₂Ru+Al₃Ru₂.The composition range ofτ₁ andτ₂ phases which can exist stably at 950°C was determined.2.In the as-cast microstructure ofβ-（Ni,Ru）Al alloy with Ru content of 0,5,10,15 at.%,Ru is enriched in dendrites,while Ni is enriched in interdendrites,and the distribution of Al is uniform.Therfore,the content of Ru has no obvious effect on the as-cast microstructure ofβ-（Ni,Ru）Al alloy.3.The Ru-freeβ-Ni Al alloy/matrix was annealed at 900℃and 1150℃for 16days and 3 days,respectively.Theβ-Ni Al alloy and the matrix alloy had severe interdiffusion,a large number of topological close-packed phase（TCP）rich in Cr,W and Mo elements are formed in the interdiffusion zone（IDZ）,and also formed a secondary reaction zone（SRZ）at 900℃;the addition of Ru in theβ-Ni Al alloy has a great effect on the coating alloy and the coating alloy at 900℃and 1150℃.The interdiffusion of elements betweenβ-Ni Al alloy and base alloys has an inhibitory effect,and with the increase of Ru content,the inhibitory effect on the TCP phase in IDZ becomes more and more obvious.when the content of Ru is 15 at.%There are only a few TCP phases in IDZ.4.The Ru-freeβ-Ni Al alloy/matrix degenerated from the initial Al-richβ-Ni Al phase to Ni-richβ-Ni Al phase and formed a small amount ofγ′-Ni₃Al phase after vacuum diffusion annealing at 950℃for 30,40,and 50 days,respectively.Harmful TCP phase was formed in IDZ,and SRZ was also formed;while theβ-Ni Al alloy containing Ru/matrix did not form TCP and SRZ in the interdiffusion zone after annealing for 30-50 days,and theβ-Ni Al alloy still maintained theβphase as the the main phase structure,but in the Ru-poor and Ni-rich region will degenerate intoγ′-Ni₃Al phase over time,the increase of Ru content can slow down the degradation ofβ-Ni Al alloy.The Ru addition of 15 at.%β-Ni Al alloy Ni Al alloy formed the leastγ′-Ni₃Al phase after 50 days of diffusion annealing,which effectively slowed down the degradation ofβ-Ni Al alloy,and the diffusion resistance effect was more obvious.