Interdiffusion performance and oxidation behaviours of NiCrAlY/Al coatings on γ-TiAl

Abstract

The interdiffusion behaviours and oxidation resistance of the NiCrAIY/AI duplex coated specimens during the isothermal oxidation test at 950°C were investigated. It was shown that the NiCrAlY coating system with an AI bondcoat outperformed the NiCrAlY single coating system and the substrate y-TiAl alloy during hot exposure. Analysis techniques such as X-ray diffraction, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to study the phase formation, microstructure and depth distribution of the elements in the coated specimens.The results showed that the NiCrAIY/AI duplex coating system exhibited better oxidation resistance and adhesion strength with the substrate during scratch test. The SEM-EDS profile analyses further showed that the outward Ti diffusion and the inward Ni diffusion were delayed apparently by the AI interlayer, which was also considered as AI source for forming protective a-Al2O3 scale on the NiCrAIY/AI coating surface.

High temperature tribological behaviour of Al/Al2O3 composite coating on γ-TiAl

“…Efforts to improve both the room temperature ductility and the high temperature oxidation resistance performance have been made in the last several decades. 3–5 Such progress, to some extent, satisfied the requirements for some aerospace and automobile parts. However, their high temperature applications are still limited due to the poor surface hardness and wear resistance.…”

High temperature oxidation behaviour of Al2O3/Al composite coating on γ-TiAl

“…The major differences between two curves are the intensity of acoustic emission peak and the starting position of first acoustic emission signals. Although the critical loads of coatings on c-TiAl alloy before and after oxidation test are larger than 50 N, above which the adhesion strength between the coating and substrate is generally sufficient for applications, [34][35][36] it is remarkable that the Al 2 O 3 /Al composite coated specimen after oxidation test displayed lower intensity of acoustic emission signal and higher critical load in comparison to that before oxidation test. The evidence of plastic deformation can be seen in the scratch track of the Al 2 O 3 /Al composite coating after oxidation test, which indicates better adhesion strength between the coating and the substrate than that before oxidation test.…”

Comparison of hot corrosion behaviour of FGM and usual TBCs

“…This TGO layer acts as a diffusion barrier and substantially reduces the degradation rate of the substrate. 1,4,[10][11][12][13] TBCs have some reliability and durability problems arise from the thermal stresses, induced by thermal expansion mismatch between the ceramic and metal layers, and oxidation. Recently, introduction of an interfacial zone with graded thermo mechanical properties between the topcoat and bond coat layer or replacement of coating with composite layer containing varying volume/weight ratio of ceramic/metallic materials are used as the effective ways to overcome the durability problems of common TBCs.…”

“…This TGO layer acts as a diffusion barrier and substantially reduces the degradation rate of the substrate. 1,4,10-13…”