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航空发动机耐腐蚀可磨耗封严涂层的制备与性能研究
Alternative TitlePreparation and Properties of Corrosion Resistance Abradable Seal Coatings Used in Aircraft Engines
张峰
Subtype博士
Thesis Advisor张伟刚
2014-04
Degree Grantor中国科学院研究生院
Degree Discipline化学工程
Keyword可磨耗封严涂层 钛合金 钝化 盐雾腐蚀 抗氧化性能 等离子喷涂
Abstract航空工业的快速发展对航空发动机提出了更高的要求。通过减小发动机叶片与机匣之间的间隙可有效降低径向气流损失,提高发动机效率,同时可降低油耗。可磨耗封严涂层广泛用于航空发动机气路封严,该类涂层具有多孔、多物相、多层、多界面的结构特征,这导致了涂层极易遭受盐雾腐蚀破坏。新型耐腐蚀可磨耗封严涂层对提高海军飞机发动机封严涂层的服役安全具有重要意义。 论文基于对目前铝基、镍基封严涂层盐雾腐蚀机理的剖析,以金属钝化理论为材料的设计依据,首次将钛铝合金和镍钛合金包覆BN复合结构材料应用于可磨耗封严涂层。 采用粘结包覆法制备了Ti/BN、Ti-Al/BN以及Ti3Al/BN复合粉体,结合真空等离子喷涂制备了钛基封严涂层;采用加氢还原和固相合金化技术制备了NiTi/BN、NiTiAl/BN以及NiCrAl/BN复合粉体,结合大气等离子喷涂制备了相应的涂层。论文对涂层物相、组织结构、耐盐雾腐蚀性、抗氧化性及力学性能进行了详细研究,主要研究结果如下: (1) 钛基封严涂层的金属相为Ti或Ti3Al金属间化合物。涂层在NaCl溶液中优异的钝化性能使得涂层具有很好的耐腐蚀性。960h盐雾腐蚀试验后,Ti/BN和Ti3Al/BN涂层未产生腐蚀产物,而Ti-Al/BN涂层表面生成了少量的腐蚀产物Al(OH)3。Ti-Al/BN涂层金属相的元素分布分析发现,Ti、Al元素在涂层中分布不均匀。元素分布不均会导致微观区域间存在自腐蚀电位差,进而诱发微观电偶腐蚀,这是导致Ti-Al/BN涂层发生腐蚀的主要原因。 (2) NiTi/BN涂层耐腐蚀性能研究表明,涂层在5%NaCl水溶液中的至钝电位为-900mV,涂层的钝化区间跨度约为520mV,在钝化区间内涂层保持较低的钝化电流密度。经960h盐雾腐蚀,仅在涂层的边缘处出现了少量的腐蚀产物Ni(OH)2。涂层表层的钝化阻止了腐蚀介质的深入渗透,使得涂层内部未受到腐蚀,涂层结合强度未受到腐蚀影响。 (3) NiTi/BN涂层的氧化试验结果表明,涂层在600℃下经过105h氧化后,材料表面生成厚度约为1μm的TiO2氧化膜;在700℃下氧化,材料表面生成了TiO2、NiO和NiTiO3的混合氧化物膜。600℃氧化形成的TiO2膜提高了涂层的耐腐蚀性;700℃条件下氧化,由于氧化过程中大量Ti迁移至表面形成了TiO2,使得涂层的再钝化能力减弱。为提高NiTi/BN涂层的抗氧化性,制备了NiTiAl/BN涂层,对两种涂层的氧化动力学研究表明,两种涂层在500℃~800℃范围内的氧化规律都满足抛物线规律;NiTiAl/BN涂层的氧化增重明显低于NiTi/BN涂层。计算两种涂层的氧化反应表观活化能发现NiTiAl/BN涂层的氧化活化能为25.8kJ/mol,NiTi/BN涂层为19.3kJ/mol,说明Al的引入及合金化提高了涂层在500℃~800℃范围内的抗氧化性能。 (4) NiCrAl/BN涂层的耐腐蚀性能研究表明,涂层在NaCl水溶液中的至钝电位为-800mV,击穿电位为-520mV,钝化电流密度为10μA/cm2。960h盐雾试验后涂层仅表面边缘处出现腐蚀产物,腐蚀后涂层的结合强度仅下降约0.3MPa,下降后涂层的结合强度为6.3MPa,满足封严涂层的使用要求。涂层断口处有少量Ni和Al的腐蚀产物。涂层耐高温氧化性能研究表明,800℃下,涂层氧化后生成了厚度200nm的氧化膜,氧化膜的物相为NiCr2O4、CrBO3和NiO。对NiCrAl/BN涂层氧化动力学研究表明,NiCrAl/BN涂层在600℃~800℃温度范围内的氧化反应表观活化能为32.7kJ/mol。 (5) 可磨耗封严涂层在海洋盐雾环境下会受到多重腐蚀机制的共同作用。孔隙加大了涂层的腐蚀面积,同时会导致氧浓差腐蚀以及局部微区腐蚀。涂层中各相间的腐蚀电位差会导致微观电偶腐蚀,各层间的电位差会导致层间电偶腐蚀。由热震或外力作用引起的微裂纹会导致缝隙腐蚀。非金属相对腐蚀介质的吸附和持续释放会使得涂层长期经受腐蚀破坏。可磨耗封严涂层的制备要考虑层间和相间的电偶腐蚀,涂层的钝化是实现涂层耐盐雾腐蚀的有效途径。
Other AbstractAs the rapid development of aviation industry, the aircraft engines have to satisfy higher requirements. Minimizing the gap between rotating and stationary can reduce the leakage flows, thereby enhance the aero-engine efficiency and reduce the fuel consumption. Abradable seal coating is always used in the sealing system in aircraft engines. The structure characters of porosity, multiphase, multilayer and multi-interface lead to its vuluerability to be corroded. It is of momentous significance to research and develop novel corrosion resistant abradable seal coating to enhance the safty of the naval aircraft flights. Based on the research of salt spray corrosion mechanism of Al-based and Ni-based abradable seal coatings, and the basis of the theory of metal passivation, TiAl alloy and NiTi alloy clad BN composite materials are applied in the abradable seal coating for the first time in the dissertation. Ti/BN, Ti-Al/BN and Ti3Al/BN composite powders were prepared by mechanically clad, and the Ti-based coatings were deposited using vacuum plasma spray (VPS) technigue. NiTi/BN, NiTiAl/BN, NiCrAl/BN composite powders were manufactured by pressurized hydrogen reduction and solid state alloying technigue, and the as-sprayed coatings were deposited using atmospheric plasma spray (APS) technology. The constituents and phases, micro-morphology, the corrosion resistance, the oxidation resistance and the mechanical properties of the coatings were studied in detail. The major results are summarized as follows: (1) The metal matrixes of Ti-based seal coatings are Ti or Ti3Al intermetallic. The excellent passivation of the coatings granting them very good corrosion resistance. After 960h salt spray corrosion test, no corrosion product formed on Ti/BN and Ti3Al/BN coatings, while some corrosion products (Al(OH)3 eta) were detected on the surface of Ti-Al/BN coating. The analysis of metal matrix in Ti-Al/BN shows that, the non-uniform elements distribution in the metal matrix of Ti-Al/BN coating resulted in micro galvanic corrosion. It is the main reason that the corrosion occurred on the surface of Ti-Al/BN coating. (2) The investigation of NiTi/BN coating’s corrosion resistance indicates that, the coating exhibits much lower passivation potential (about -900mV) and wider steady passive region (about 520mV) with low passive current density (about 39.8μA?cm-2) in 5wt.% NaCl solution. Under 960h salt spray test, few corrosion products (amorphous Ni(OH)2) were detected on the edge of the coating. The passivation in the surface of the coating prevented the electrolyte from penetrating to the interior of the coating and causing corrosion. The bonding strength of the coating shows a negligible decrease. (3) The oxidization test of NiTi/BN coating indicate that, after a 105h test under 600℃, a TiO2 oxide film with a thickness of 1μm formed on the surface of the specimen; while under 700℃, a mixed oxide film formed on the surface of the specimen and its phases include TiO2, NiO and NiTiO3. The oxidation of the coating under 600℃ improved the corrosion resistance of the coating because of the formation of TiO2 film. Under 700℃,most of the Ti migrated to the surface and resulted in the decrease of the coating’s repassivation. To improve the oxidation resistance at elevated temperatures, NiTiAl/BN coating was prepared. Oxidation kinetics of the NiTi/BN and NiTiAl/BN coatings indicate that, the oxidation of the two coatings complies with the parabolic line law in the temperature range of 500℃ to 800℃. It is obvious that the weight gains of NiTiAl/BN coating are lower than those of NiTi/BN coating. The oxidation activation energies of the NiTi/BN and NiTiAl/BN coatings are 19.3 kJ/mol and 25.8kJ/mol, respectively. The addition of Al and alloying enhance the oxidation resistance of the coating. (4) The corrosion behavior of NiCrAl/BN coating shows that, the passivation potential of the coating is -800mV, the breakdown potential is -520mV and the pas
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/15534
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
张峰. 航空发动机耐腐蚀可磨耗封严涂层的制备与性能研究[D]. 中国科学院研究生院,2014.
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