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  • Exclusive: Corrosion and protection technology of aviation materials
    ZHANG Huanhuan, LIU Wenchao, TIAN Haoliang, WEI Shicheng, LIANG Yi
    Science & Technology Review. 2022, 40(5): 28-33.
    A corrosion-resistant and wear-resistant coating is prepared on the inner wall of red copper pipe by centrifugal self propagating melting technology. The morphology of functionally gradient coating on ceramic lining is analyzed by means of SEM, hardness test and electrochemical test, and the hardness, wear resistance and corrosion resistance of the ceramic coating are studied. The results show that the functionally gradient coating is composed of a ceramic lining layer, a metal transition layer and a copper matrix layer. The hardness of the coating is significantly improved and has good resistance to dry wet alternating salt spray corrosion. The wear resistance of the ceramic lining is twice that of the copper matrix.
  • Exclusive: Corrosion and protection technology of aviation materials
    TIAN Yong, GUAN Zhenwei, LI Jing
    Science & Technology Review. 2022, 40(5): 34-43.
    Through simple chemical reactions, 3-aminopropyl triethoxysilane and 3-glycidyl ether oxypropyl trimethoxysilane have been successfully grafted onto graphene oxide to prepare composite of a sandwich structure. The two surface modifiers make it easier for the graphene oxide to form chemical bonds with epoxy resin/polyamine. Through electron microscope and visibleinfrared full-band transmittance tests it is found that the graphene oxide treated by the modifier can evenly disperse in the resin system. Compared with the pure epoxy amine resin coating, the water vapor transmittance of the GO-APTES/Resin coating is reduced by 30%. A "labyrinth effect" is formed, which is a good barrier against water vapor. Moreover, the anti-corrosion mechanism of the composite coating is studied by Bode and Nyquist spectra. The shielding of the coating against the corrosive medium is enhanced after adding modified graphene oxide, and the ability of the corrosive medium to penetrate the coating is reduced. Therefore, the coating is better attached to the metal and the area of electrochemical corrosion is smaller, having a better corrosion protection ability. Neutral salt spray test shows that the coating surface will not fall off or present blister after 7000 hours.
  • Exclusive: Corrosion and protection technology of aviation materials
    FANG Bing, YANG Rui, YANG Liang, JIANG Guojie
    Science & Technology Review. 2022, 40(5): 44-51.
    Well dispersed graphene slurry is prepared with silane-functionalized graphene oxide (f-GO). This graphene slurry is then combined with solved resin and pre-dispersed zinc slurry to prepare the cold-coating zinc paint. The best addition dosage of graphene oxide in the coating is determined by salt spray fog, contact angle test and electrochemical measurements. Properties of the cold-coating zinc paint containing f-GO are tested, and the time of resisting salt spray in the test is above 2500 h, which is about twice the time of the hot-dip galvanizing counterpart with the same thickness.
  • Exclusive: Corrosion and protection technology of aviation materials
    FANG Bing, CHEN Haohui, WANG Shouze, TIAN Haoliang, ZHANG Shu'ai
    Science & Technology Review. 2022, 40(5): 52-62.
    The effect of alloying elements on the basic properties of associated metal coatings is investigated. A seamless steel pipe with diameter of Ф78 mm*8 mm*550 mm is selected, and a long groove of 150 mm*10 mm*4 mm is set in advance at 200~350 mm from the inner wall of the pipe to the end of the pipe, and the associated metal coatings with different contents of alloying elements are prepared by self propagating high temperature synthesis technology. The effects of different alloy elements on pores, cracks, hardness and corrosion resistance of associated metal coatings are then investigated by Vickers hardness measurement, electron microscopic scanning and acid immersion corrosion test. After adding Nb and Cr elements, the hardness of the associated metal layer increases, pores and cracks are obviously reduced, and microstructure tends to be homogenized. The corrosion resistance of the associated metal layer is directly proportional to the amounts of Cr and Nb, but the amount of ZrO2 has minor effect. The weight loss of associated metal coating with the best corrosion resistance is only 0.271 g, the weight loss rate is 2.71%, and the weight loss rate is only 21.22% of the pure iron layer. Addition of Nb and Cr can effectively improve the basic properties of the associated metal coating, while Zr has minor effect on the properties of the coating.
  • Exclusive: Corrosion and protection technology of aviation materials
    LI Haiyang, ZHAN Zhongwei, LUO Chen, SUN Zhihua
    Science & Technology Review. 2022, 40(5): 63-68.
    Electrochemical machining is usually used to shape titanium and titanium alloys because it has high efficiency and great capability to manufacture thin-walled and special-shaped components. However,the passive film and formation of pitting corrosion on both workpiece surface and the non-machined part are the main drawbacks when the machining uses low working electric currents. Therefore, research on pits initiation, pits growth and pits control during electrochemical machining is in great need. This paper reviews the research progress on cause, prevention, and control of pitting corrosion of titanium alloys during electrochemical machining. Meanwhile, the advantages and weaknesses of each strategy are well illustrated. The research trend in pitting corrosion for electrochemical machining of titanium is also presented.
  • Exclusive: Corrosion and protection technology of aviation materials
    ZHAN Zhongwei, SUN Zhihua, GE Yulin
    Science & Technology Review. 2022, 40(5): 69-77.
    Shipborne environment is the main service circumstance of aircraft equipment in the future, which combines features of high temperature, high relative humidity, high salinity from marine environment and acidic gas from shipborne equipment. Aluminum alloys suffer severe corrosion in such an environment. In this study acidic salt spray test is used to simulate the shipborne environment and applied to 2124 aluminum alloys with three different anodic oxidations, i.e., chromic acid anodization (CAA), boric-sulfuric acid anodization (BSAA) and malic-sulfuric acid anodization (MSAA). The corrosion resistance and fatigue property of anodized 2124 alloys are evaluated at different cycles of the test. The structure evolution of anode oxide films is characterized by electrochemical impedance spectroscopy(EIS). The axial fatigue life of anodized samples is measured after different cycles of the test. The fracture morphology is also studied. The results suggests that anodic oxidation can significantly enhance the corrosion resistance of 2124 alloy. BSAA and MSAA samples exhibit better corrosion resistance than CAA samples. Corrosion signs of the substrate of CAA appear after 4 cycles of the test, while after 6 cycles for BSAA and MSAA. The fatigue life generally declines with salt spray test cycles, which is consistent with the corrosion resistance performance. However, MSAA has the highest residual fatigue life.
  • Exclusive: Corrosion and protection technology of aviation materials
    LUO Chen, LI Haiyang, CUI Yongjing, SUN Zhihua, TANG Zhihui
    Science & Technology Review. 2022, 40(5): 78-87.
    Compressor blades and fan blades of aero engine encounter the blasting load from sand particles during service, as well as the influence of temperature, humidity and air pollution. In this paper, test methods related to sand environment and sand particle erosion are investigated, with emphasis on the common and difference of these methods using high speed sand stream to impact on samples. Gas jet test is chosen as a proper method to carry out erosion test and research for compressor blade and fan blade. An erosion method is designed according to the sand composition and particle size listed in GJB 241A-2010, GJB 242A- 2018. Sand feeding rate and testing time are controlled so as to meet the sand mass loads of compressor blade and fan blade in real service. The sand mass load is equivalent to the sand blast environment for aero engine in 1 year. Sand particle erosion testing and GJB 150.11A-2009 salt fog testing are carried out alternatively so that the testing scheme is closer to real service condition. Such methods may provide a technique foundation for aero engine compressor blade and fan blade to establish damage evolution rules and models considering the effect of corrosion environment and erosion load.
  • Exclusive: Corrosion and protection technology of aviation materials
    WANG Zhanbin, LI Chunguang, XIAO Shuhua
    Science & Technology Review. 2022, 40(5): 88-94.
    Fluoroether rubber is usually used as a sealing material in high temperature oil environment. In this study, FM-1D fluoroether rubber is the research object and is aged at high temperature in No. 15 aviation hydraulic oil. Its tensile strength, elongation at break, compression permanent deformation, mass change, volume change, surface and fracture morphology after aging are studied and compared with those of nitrile butadiene rubber. The results are as follows. Fluoroether rubber has excellent aging resistance to aviation hydraulic oil medium. Its tensile strength, elongation at break and compression permanent deformation may keep stable after aging in the hydraulic oil medium below 170℃. Its heat resistance basically remains unchanged. Changes of mass and volume of fluoroether rubber in hydraulic oil increase with increase of temperature and keep stable over time. It is better than the nitrile butadiene rubber compound in terms of mass, volume changes and stability. In the aging process of fluoroether rubber, degradation of compression permanent deformation basically conforms to the exponential decay law, but degradation of tensile property obviously does not conform to that law, and model Arrhenius (P=Ae-Kt) equation does not apply to life prediction either.