Al2O3 aerogels are used as high-temperature insulation materials, especially in the temperature range above 1000 degrees C, due to their excellent high-temperature resistance. However, they present notable drawbacks, such as hydrophilicity, which leads to easy water vapor absorption, and high brittleness. To address these issues, this work first synthesizes hydrocarbon chain polymer polyethyltrimethoxy-silane (PVTMS) from vinyltrimethoxysilane (VTMS). Then Al2O3-PVSQ aluminum-based aerogels are prepared by in situ co-polymerization using PVTMS and Al(NO3)3 & sdot;9H2O as precursors. The system introduces polyethylene chains into the Al2O3 backbone and realizes the transition from hydrophilicity to hydrophobicity by adjusting the content of organic components, with a contact angle of up to 136.8 degrees. Furthermore, the mechanical properties of Al2O3-PVSQ aerogels are improved due to the participation of organic components in forming the network, with the compressive modulus reaching a maximum of 3.89 MPa when n(PVTMS/Al) = 1. Otherwise, when n(PVTMS/Al) = 1, the thermal conductivity of Al2O3-PVSQ1 drops to as low as 0.025 W/(m & sdot;K).

This work aimed to explore the effect of cBN (cubic boron nitride) content on the microstructures and wear-corrosion resistance of the CoCrFeNiTi0.8-xcBN (x = 0, 2, 4, 6 wt.

In situ-grown Mg-Al layered double hydroxide(LDH)films were obtained on an anodized AZ31 substrate,with the immersion of sample in different concentrations of Al3+solution.The structure,composition and morphology of LDH films were investigated by X-ray diffraction(XRD),Fourier transform infrared(FTIR)and scanning electronic microscopy(SEM),and the corrosion behavior of LDH films was further studied by electrochemical impedance spectroscopy(EIS).The influence of Al3+concentration on the growth behavior of LDH was also discussed.The results indicated that the nest-like structure of MgAl-LDH film was composed of interconnected MgAl-LDH nanosheets.Besides,the LDH obtained in 0.032 mol·L-1 Al3+solution,possessing dense laminated structure,could effectively seal the porous surface of anodic oxide film.EIS results revealed that the samples coated with LDH films showed a higher electrochemical impedance,and thus,the corrosion resistance of samples coated with LDH films was signally improved compared with the anodized alloy.

Thermal barrier and anti-ablation coatings play essential roles in protecting jet nozzles, gas turbine engines and other machines from high temperatures. In this work, a novel curved structure of Mo/MSZ alternate multilayer was designed and fabricated by air plasma spraying. Two steps of the hot isostatic pressing were applied to improve the mechanical strength and interlayer bonding. The alternate structure enabled thick MSZ (Magnesium oxide stabilized Zirconia) layers and show an excellent thermal insulation ability under high-temperature ablation (4.3 MW/m2). Due to the curved surface, the thermal and residual stress is larger at the outer layer and edge, leading to cracks at the most out layer during the ablation. Moreover, during the ablation, the surface suffered steps in the order of hot flush damaging, MSZ and Mo melting, mixing, and Mo oxidizing. This work provided design, reinforcing method and ablation behavior analysis of alternate multilayer of TBC, supporting a solution to increase the performance of thermal insulation and anti-ablation.

Hard films play essential roles in the wear protection of metal moving components. In this study, the TiCN/Cr3C2- NiCr and TiCN/WC-CoCr duplex coatings were designed and fabricated by utilizing the high-velocity oxygen fuel and the high-temperature chemical vapor deposition processes. The effects of two cermet interlayers on the microstructure, mechanical characteristics, stress distribution, and sliding wear behavior of the top TiCN films were thoroughly explored. Results evidenced that the TiCN/WC-CoCr duplex coating had a smoother surface than the TiCN/Cr3C2-NiCr duplex coating. The load-bearing capacity and fracture toughness of TiCN/WC-CoCr duplex coating were superior to TiCN/Cr3C2-NiCr duplex coating due to WC-CoCr coating possessing higher hardness, elastic modulus and high-temperature stability. The TiCN/WC-CoCr duplex coating also exhibited lower Von Mises stress compared to TiCN/Cr3C2-NiCr duplex coating, and the stress concentration zone was further away from the interface between the TiCN film and the cermet interlayer. The wear resistance of TiCN/ WC-CoCr duplex coating was approximately 2 and 1.5 times that of the single TiCN film and TiCN/Cr3C2-NiCr duplex coating under 20 N load. Moreover, the wear mechanisms of the duplex coatings involved abrasive wear, adhesive wear and oxidative wear. This work significantly enhanced the wear resistance of TiCN films, which will broaden the application of TiCN film in non-load-bearing metal moving components.

目的 探讨平衡肘断裂原因,消除故障隐患和防止类似问题发生.方法 采用单反相机、扫描电镜、金相显微镜、硬度计、电感耦合等离子体原子发射光谱仪等对平衡肘故障件的宏观形貌、微观形貌、显微组织、硬度、化学成分等开展表征分析.利用ANSYS有限元软件对内花键进行应力分析,并对2 次淬火的试样尺寸进行测量.结果 右4 平衡肘裂纹源断口为撕裂和沿晶的混合断裂,断口芯部为解理断裂;右2 平衡肘断口内表层淬火层为沿晶和韧窝的混合断裂,芯部为韧性断裂.故障件显微组织和化学成分均无明显变化,仅表面硬度值较实验前降低了 7%～9%.断裂失效原因是由于内花键二次高频淬火后收缩变形,齿根圆弧部位在腐蚀介质和交变载荷的共同作用下因应力集中而形成裂纹,在后期循环应力作用下,裂纹继续扩展导致疲劳断裂.结论 从加强腐蚀控制和热处理的角度出发,通过选用抗腐蚀性能好的材料、进行表面防护处理、控制车体环境的湿度和温度等加强腐蚀控制,并增加采用电脉冲等方式对变形花键齿进行修形工序严格控制尺寸范围,避免产生过大拉应力,确保装备质量.

使用光学方法测量发动机喷嘴内部情况时,由于喷嘴透明固壁的曲面形状会引起光学畸变,从而影响测量的精度.针对该现象,采用理论分析的方法,以一个全新的角度详细阐述了一种光学修正方法,该方法适用于任意曲面状的透明固壁.将得到的光学修正方法应用在圆管中,获得的结果与现有的理论推导结果、实验结果一致.

某船用湿式多片摩擦离合器内置于齿轮箱,受结构限制,内部花键传动采用径向供油方式,在长时间的使用中,会造成供油环密封老化和磨损,使进入离合器内部润滑减少,造成花键损坏,对航行安全产生一定的影响,因此研究某船用摩擦离合器内部润滑油对花键长期运行磨损失效机理,进一步提高离合器长期运行可靠性.采用有限元仿真分析离合器内部油路在不同泄漏量下的流场、出口流量,通过离合器流量运转试验进行离合器花键失效的定性验证.通过离合器内部供油环密封间隙分别在0、0.3、0.5、0.7 mm时的出口流量和流场仿真可知,其出口润滑流量分别损失为3.67％、20.26％、35.57％、39.36％,导致出口流量减少1/3,无法满足离合器润滑量的需要,离合器无法得到及时冷却,使离合器花键的寿命大幅度降低;通过离合器流量运转试验,尤其是在极端缺油试验中,花键运行6h就已经开始出现变色情况.某船摩擦离合器花键失效机理在于离合器长时间运行后,供油环密封长期磨损造成离合器内部供油泄漏,引起离合器花键供油不足,蠕动花键产生的热量无法快速被带走,使花键寿命快速下降.研究成果可为离合器长寿命周期可靠性研究提供参考.

In order to explore the corrosion damage behavior of plasma-sprayed NiCoCrAlY/magnesia-stabilized zirconia (18~22 wt.% MgO-ZrO2, MSZ) thermal barrier and anti-ablation coatings in a salt spray environment, a series of neutral salt spray (NSS) tests for 96 h (N-2), 192 h (N-4) and 288 h (N-6) were carried out on the coatings. The microstructures, composition distributions, potentiodynamic polarization curves, bonding strengths and anti-ablation properties of the coatings before and after the NSS tests were characterized. The results show that, with the increase in salt spray time, the expansion and overflow of corrosion products (FexOy) led to more defects forming inside the coating; the porosity of the top coat (TC) of N-6 increased to 15.2% in comparison to that of the blank control sample (N-0), which was 8.5%. According to the potentiodynamic polarization curves, accelerated corrosion occurred in the coating samples after the salt spray time reached 192 h, and the corrosion current density rapidly surged from 2.2 × 10−8 A·cm−2 (N-4) to 2.2 × 10−5 A·cm−2 (N-6). Similar degradation tends could be found in the bonding strengths and mass ablation rates of the coatings due to the accumulation of loose corrosion products on the substrate, which affected the bonding states of the coatings and promoted their spalling under an oxyacetylene flame (OAF). As a result, the maximum service life of the NiCoCrAlY/MSZ coatings in the neutral salt spray environment was about 192 h. This work is instructive for studying the environmental adaptability of metal/ceramic double-layer coatings.

目的 研究海洋大气环境对冷喷涂Ni/Al2O3复合涂层腐蚀损伤行为的影响,为提高合金钢的耐腐蚀性能提供依据.方法 采用冷喷涂技术在合金钢30CrMnSi表面制备Ni/Al2O3复合涂层,在万宁近海岸户外和海洋平台分别暴露6个月后,采用扫描电镜、电化学工作站等分析检测技术,研究Ni/Al2O3复合涂层在万宁海洋大气环境下的腐蚀行为.结果 近海岸户外暴露6个月后,试样表面盐霜覆盖均匀,局部区域出现了浅红褐色的腐蚀锈迹;海洋平台暴露6个月后,表面盐霜覆盖不均匀,未观察到喷涂态涂层搭接的特征,涂层表层发生粉化.结论 在万宁近海岸户外暴露6个月后,冷喷涂Ni/Al2O3复合涂层只是表层发生了轻微腐蚀,主体结构较为完整,仍能有效防护基体腐蚀.近海岸平台暴露6个月后,大量Al2O3颗粒的剥落以及腐蚀介质的进一步扩散,导致涂层中出现裂纹,大大加速了涂层的腐蚀.

叙述了气垫船减速齿轮箱在海洋大气和海水溅射环境下腐蚀与防护工艺的研究进展.介绍了气垫船减速齿轮箱长期处于高温、高湿、高盐雾以及海水溅射环境下的腐蚀特征和主要腐蚀类型,总结了减速齿轮箱中铝合金、合金钢、不锈钢等不同材质零件腐蚀防护技术的研究进展.最后,提出了海洋环境下气垫船减速齿轮箱的腐蚀防护需从结构设计、材料选型、加工制造、运输贮存、维护保养等方面着手,在充分利用现有表面处理技术的基础上,加强阳极氧化、微弧氧化、电镀、涂料涂层等技术的组合;强化腐蚀监测技术,有效预警防护层失效,同时大力研发海洋环境下长期有效、绿色环保的表面处理和涂层技术.另外,采用系统工程来提高海洋环境下金属材料的环境适应性,进而提高减速齿轮箱等部件的可靠性和安全性.

A doublely-doped layered double hydroxide (LDH) film was produced on an anodized magnesium alloy AZ31. The Ce-doped Mg-Al LDH film was prepared by in-situ hydrothermal treatment method, and the intercalation of vanadate was realized by ion-exchange reaction. The structure, morphology and composition of as-prepared LDH film were investigated by X-ray diffractometer, field-emission scanning electronic microscope and energy dispersive spectrometry. Results indicated that a uniform and compact LDH film was formed and the intercalation of Ce3+ and vanadate would change the crystal structure of LDHs. The results of the potentiodynamic polarization, electrochemical impedance spectra, hydrogen evolution and corrosion weight loss tests showed the Ce3+ and vanadate anions significantly improve the impedance of LDH film, and the active double-doped LDH film could effectively protect the magnesium substrate from corrosion.

Highly oriented Mg-Al layered double hydroxide (LDHs) films were deposited on magnesium alloy AZ31 with different deformation processes by an easy in-situ growth method. The characteristics of the films were investigated by optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical, immersion and hydrogen evolution tests. The corrosion protection performance ranked the LDHs films as the increasing series: CS-LDHs (as-cast sample with LDHs) < AE-LDHs (asymmetric extrusion sample with LDHs) < SE-LDHs (symmetric extrusion sample with LDHs) < RS-LDHs (rolled sample with LDHs). A thicker and more compact LDH conversion coating was formed on the RS sample, and had the best corrosion protection performance.

A layer of pure aluminum coating was prepared on AZ80 magnesium alloy by cold spray, and then a pure aluminum/aluminum oxide composite coating was successfully fabricated on the surface of pure aluminum coating by micro-arc oxidation. The surface and cross-section morphology, composition and phase structure of the coatings were analyzed by scanning electron microscope (SEM), energy spectrometer (EDS) and X-ray diffractometer (XRD). The corrosion behavior of the coatings immersed in 3.5%NaCl(mass fraction) solution for different time (30 min and 7 days) was investigated using potentiodynamic polarization curves and electrochemical impedance spectroscopy. The results show that after 30 minutes of immersion, the corrosion current densities of the pure aluminum coating and the pure aluminum/aluminum oxide composite coating are 3.7×10-6 A·cm-2 and 8.0×10-7 A· cm-2, respectively; after 7 days of immersion, the corrosion current densities are 9.0×10-6 A·cm-2 and 1.8×10-6 A·cm-2, respectively. Both the pure aluminum/aluminum oxide composite coating and the cold sprayed aluminum coating can effectively delay the corrosion of the magnesium alloy substrate. Among them, the corrosion resistance of the micro-arc oxidation composite coating is nearly 5 times of the cold sprayed pure aluminum coating. The further improvement in corrosion resistance is attributed to the excellent physical barrier effect of the micro-arc oxidation ceramic layer.

A thick composite anodic oxide film was fabricated in an environmentally friendly malic acid electrolyte containing PolyTetraFluoroEthylene (PTFE) nanoparticles on Ti-10V-2Fe-3Al alloys. The influence of pulse frequency on the morphology, microstructure and composition of composite anodic oxide films containing PTFE nanoparticles was investigated using Field Emission Scanning Electron Microscopy (FE-SEM) equipped with Energy Dispersive Spectroscopy (EDS), Atomic Force Microscopy (AFM) and Raman spectroscopy. The tribological properties in terms of the friction coefficient, wear loss and morphology of worn surfaces were measured by ball-on-disc tests. The electrochemical property was evaluated by potentiodynamic polarization. The results indicated that the titanium dioxide of composite anodic oxide films transformed from anatase to rutile with the change of pulse frequency, which could result from the electrochemical dynamic equilibrium. The combination of PTFE nanoparticles and malic acid electrolyte molecules can influence the energy fluctuation of electrochemical equilibrium and formation of composite anodic oxide films. Moreover, composite anodic oxide films fabricated under the condition of 1.0–2.0 Hz exhibited the best wear resistance and corrosion property. The schematic diagram of the film formation and PTFE nanoparticles spreading process under different frequencies was elucidated.

In this study, malleable and heavy Ta particles were introduced into soft Al powders to prepare Al-Ta composite coatings through a low-pressure cold-spray process; for comparison, Al-A2O3 composite coatings were also deposited. The surface and cross-sectional morphologies, deposition efficiency, microstructure, hardness and composition of the coatings were investigated. The results demonstrated that the Al-Ta coatings had roughness values that were almost twice as large as those of the Al-Al2O3 coatings for the same volumetric fraction of reinforcement particles used in the feedstock. Ta particles were more effective in improving the deposition efficiency and densification than were Al2O3 particles. The formation mechanism of the Al-Ta coatings was mainly attributed to the malleable and heavy nature of Ta particles, which allowed them to bond with the formed coating and impact the coating strongly through the peening effect.

The effects of three pyridine derivative additives, 4-hydroxypyridine, 4-picolinic acid, and 4-cyanopyridine, on Al-Mn coatings were investigated in 1-ethyl-3-methylimidazolium chloride-AlCl3-MnCl2 (EMIC-AlCl3-MnCl2) ionic liquids. The smooth mirror-like bright Al-Mn coatings were obtained only in the EMIC-AlCl3-MnCl2 ionic liquids containing 4-cyanopyridine, while the matte Al-Mn coatings were electrodeposited from EMIC-AlCl3-MnCl2 without additives or containing either 4-hydroxypyridine or 4-picolinic acid. The scanning electron microscope and X-ray diffraction showed that the bright Al-Mn coatings consisted of nanocrystals and had a strong (200) preferential orientation, while the particle size of matte Al-Mn coatings were within the micron range. The brightening mechanism of 4-cyanopyridine is due to it being adsorbed onto the cathode to produce the combined effect of (1) generating an overpotential to promote Al-Mn nucleation; (2) inhibiting the growth of the deposited nuclei and enabling them grow preferentially, making the coating composed of nanocrystals and with a smooth surface. The brightening effect of 4-cyanopyridine on the Al-Mn coatings was far better than that of the 4-hydroxypyridine and the 4-picolinic acid. In addition, the bright Al-Mn coating was prepared in a bath with 6 mmol·L−1 4-cyanopyridine and displayed superior corrosion resistance relative to the matte coatings, which could be attributed to its unique nanocrystalline structure that increased the number of grain boundaries and accelerated the formation of the protective layer of the corrosion products.

Mg-AlLDHs (layered double hydroxides) coatings were deposited on the surface of titanium alloy Ti10V2Fe3Al, accompanied by modification with ZrO2 and MoS2 nanoparticles through electrophoretic deposition. FE-SEM, XRD and EDS measurements were used to investigate the microstructure and composition of the composite coatings. Corrosion resistance was measured by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) in 3.5 wt% NaCl solution. The LDHs/MoS2 composite coating exhibited the best corrosion resistance. Ball on disc tests was implemented to obtain morphology, the friction coefficient and wear loss of the worn surfaces. The LDHs/ZrO2 composite coating exhibited the best wear resistance. A mechanism for enhancing the wear-resistance of the different nanoparticles-modified MgAl-LDHs coatings was proposed.

目的 研究冷喷涂镍涂层对不锈钢焊点腐蚀行为的影响,为提高不锈钢焊接结构件的耐腐蚀性能提供依据.方法 采用冷喷涂技术在316L不锈钢电阻点焊结构件表面制备纯镍涂层,在金相组织、酸性盐雾腐蚀性能等检测分析基础上,研究不锈钢焊点在有涂层和无涂层条件下的腐蚀行为.结果 采用冷喷涂技术在不锈钢焊点表面制备出了孔隙率不大于0.5％的高致密纯镍涂层,带有涂层的不锈钢点焊结构件经过96 h酸性盐雾试验后,未发生腐蚀.结论 不锈钢表面钝化膜在点焊过程中发生破坏,基体裸露在腐蚀介质中,导致焊点区域发生腐蚀.在表面制备高致密镍涂层后,通过高耐蚀涂层对焊点进行屏蔽防护,有效提高其耐腐蚀性能,满足了某装备不锈钢结构件在酸性盐雾条件下的使用要求.