Progress has been made in the research on corrosion of aero engine sealing

As a key technology in aircraft engines, abrasible sealing coating can improve the overall air tightness of aero engines under the premise of protecting blades, which is an effective means to improve the efficiency of the engine and ensure its safe operation. With the vigorous development of China’s maritime aviation, in the marine atmospheric environment of high humidity, high salt and high heat, the corrosion problem of wearable sealing coating has become a key problem that plagues the stability and safety of engine operation, and it is imperative to develop a new generation of wearable sealing coating resistant to marine atmospheric corrosion at room temperature. 

Recently, the corrosion electrochemistry research group of the Center for Materials Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences has made new progress in the field of corrosion of wearable sealable coatings. It was found that the CuAl-Ni/C sealing coating prepared by replacing part of Al with Cu on the basis of Al-BN sealing coating had excellent abrasionability, erosion resistance and high temperature oxidation resistance (Fig. 1). Due to the presence of the CuAl interphase in the coating, the coating’s resistance to corrosion at room temperature is significantly improved (Figure 1). It is found that in the initial stage of corrosion at room temperature, the active dissolution of Cu in the coating is higher than that of Al, which is contrary to the conventional perception that the activity of Al is significantly higher than that of Cu. Furthermore, the team used first-principles calculations and molecular dynamics calculations (Fig. 2) to comprehensively analyze the activities of Cu and Al atoms on the surface of each alloy phase of the coating and the adsorption and diffusion capacity of Cl- on the surface of each alloy phase, and explained that the fundamental reason why the dissolution rate of Cu is higher than that of Al is due to the preferential corrosion of CuAl interphase.

Fig. 1.(a) Comprehensive mechanical properties evaluation of two types of sealing coatings;(b) High-temperature performance evaluation of CuAl-Ni/C coatings; (c-d) surface morphology of two sealing coatings after salt spray test; (e-f) Comprehensive mechanical properties evaluation of two kinds of sealing coatings after corrosion.

Figure 2. (a-b) OCP curves and polarization curves; (c) In-situ ICP-OES test results; (d-e) work function calculation model and its results; (f) Schematic diagram of the interaction between Cl- ions and metal surfaces; (g-h) adsorption energy calculation model and its results; (i-j) Diffusion coefficient calculation model and its results.

This study not only verifies that the comprehensive service performance of the sealing coating can be effectively improved through reasonable composition design, but also demonstrates the potential of theoretical calculation methods such as first-principles calculation and molecular dynamics calculation in predicting and elucidating the corrosion activity of alloying elements, which provides a new way for the theoretical study of corrosion electrochemistry. The research results were published in the Chemical Engineering Journal under the title of An abradable and anti-corrosive CuAl-Ni/C seal coating for aero-engine. (Source: Institute of Metal Research, Chinese Academy of Sciences)

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