热浸镀铝硅镁涂层组织与腐蚀性能研究

利用热浸镀技术在铁基体表面制备了铝硅镁涂层，探讨热浸镀时间对涂层的影响，研究了涂层的腐蚀性能。结果表明：随着热浸镀时间的增加，铝硅镁涂层中铁铝反应层厚度呈现抛物线式增长，当Mg和Si添加量达到3%时，铁铝反应受到明显的抑制作用，反应增厚的速度较慢。3.5%NaCl溶液中的电化学腐蚀表明，随着Mg和Si的增加，涂层的自腐蚀电位呈现下降趋势，Al-6Mg₂Si涂层具有最低的自腐蚀电位和较小的自腐蚀电流。     

喷涂聚脲应用于悬索桥主缆防护涂层的耐腐蚀性能研究

应用电化学阻抗谱技术(EIS)研究了处于模拟海洋环境中的镀锌涂层钢绞线、镀环氧涂层钢绞线、热挤高密度聚乙烯(HDPE)套防护钢绞线和喷涂聚脲涂层钢绞线在干湿交替环境中涂层的腐蚀程度。研究结果表明:镀锌涂层和镀环氧涂层的涂膜阻抗值均在涂层失效阻抗106Ω·cm2之下,涂层已经处于腐蚀后期;HDPE防护层的涂膜阻抗值的数量级为106,涂层即将进入腐蚀后期;喷涂聚脲防护层仍具有较大阻抗,防护性能良好。     

军事装备腐蚀现状及对策

简述了军事装备腐蚀及防腐蚀的现状，并论述了大气腐蚀、海水腐蚀和联合腐蚀的特点。着重介绍了高速电弧喷涂长效防蚀技术、纳米电刷镀防腐耐磨涂层技术，非晶态合金化学镀层防腐技术、纳米固体薄膜减摩防腐技术和纳米防腐涂料及涂装技术。提出了腐蚀防护工作重点，介绍了国家对腐蚀防护的策略。     

硅和镁含量对双镀Zn–23Al合金组织结构和耐蚀性的影响第一部分──Zn–23Al–xSi镀层的组织结构和耐蚀性

采用"双镀法"在钢板表面热浸镀不同硅含量的Zn–23Al–xSi合金镀层(x=0.1,0.3,0.5,0.7,1.1).采用扫描电镜、能谱仪、电化学测试和中性盐雾试验研究了浸镀液中硅含量对镀层组织结构和耐蚀性的影响.结果表明,随着浸镀液中硅含量升高,Zn–23Al–xSi合金层厚度先减小后稳定在2μm左右,耐蚀性先改善后变差.当浸镀液中硅含量不低于0.7％时,镀层表面出现单质硅富集相.浸镀液中硅含量为0.5％时所得Zn–23Al–0.5Si合金镀层的耐蚀性最佳.     

NiCrAlY含量对NiCrAlY/Al2O3涂层机械性能及介电性能的影响

采用大气等离子喷涂技术,以镍基合金(NiCrAlY合金)粉为吸收剂、氧化铝(Al2O3)为基体,制备出NiCrAlY/Al2O3(NA)复合涂层.分析了复合涂层的相组成及显微结构,研究了 NiCrAlY含量变化对复合涂层的机械性能及介电性能的影响.结果表明:喷涂后的涂层中出现了刚玉、铬刚玉等非金属相及唯一的金属相Ni.随着NiCrAlY含量的增加,复合涂层的抗弯强度、断裂韧性逐渐增强;在8.2～12.4 GHz频率范围内,涂层的介电常数实部与虚部值都随着NiCrAlY含量的变化而明显变化,且在NiCrAlY含量为25％时达到最高值,这主要与喷涂过程中分离出金属Ni的含量、冷却后的形状及分布状态有关.     

铈元素对热浸锌–铝–镁合金镀层显微组织及耐蚀性的影响

在Zn–Al–Mg镀液中添加不同量的稀土Ce以提高热浸镀Zn–Al–Mg合金层性能。通过分析合金镀层的表面形貌和截面形貌以及中性盐雾试验,系统地研究了镀液中Ce添加量对合金镀层显微组织结构和耐蚀性的影响。当铈的添加量≤0.05%(质量分数)时,随铈添加量增大,热浸镀Zn–Al–Mg合金层的晶粒逐渐细化,尺寸逐渐均匀;δ相层的厚度变化不大,而ζ相层略微减薄。当铈添加量0.05%时,随铈添加量增大,镀层合金相厚度骤减。中性盐雾试验表明,镀液中添加Ce有利于提高Zn–Al–Mg合金镀层的耐蚀性,但其添加量不宜超过0.05%。     

四种涂层在模拟油田环境下的腐蚀性能评价

采用不同表面处理方法在N80钢表面上分别制备化学镀Ni—P、电镀Zn—Ni、热喷涂Ni—Cr—Fe—Ta—Mo—Ti和热浸镀Al—Zn—Si合金涂层,利用CO2高温高压腐蚀试验等方法评价其在模拟油田环境下的耐腐蚀性能。试验结果表明：四种涂层的耐腐蚀性能按Ni—P、Ni—Cr—Fe—Ta—Mo—Ti、Zn—Ni和Al—Zn—Si合金涂层的顺序依次减小。     

粘结层的铝含量及热处理对航空发动机热端部件DZ40M合金上热障涂层静态氧化行为的影响

采用超音速火焰喷涂在航空发动机热端部件DZ40M合金表面制备了铝含量不同(6%、8%和12%)的Ni-Co基粘结层,再等离子喷涂YSZ(氧化钇稳定氧化锆)陶瓷面层,制得了热障涂层。通过扫描电镜、X射线衍射仪和拉曼光谱仪研究了粘结层成分及其真空热处理对热障涂层显微形貌、物相组成以及界面热生长氧化物(TGO)的影响。结果表明,3种粘结层的致密性均较高,与基材以及陶瓷层结合较好。3种喷涂态粘结层中的物相组成与原始粉末相似,随着Al含量增加,原始粉末和喷涂态粘结层中β相的含量逐渐增加。粘结层的真空热处理可以有效降低3种热障涂层在静态氧化过程中TGO的增厚速率。未经粘结层真空热处理制成的热障涂层中,TGO的增速与粘结层中Al的含量有关。粘结层真空热处理后,晶界扩散会显著影响TGO的增厚速率,TGO晶粒尺寸的增加会造成晶界数量减少,相应地会降低TGO的增厚速率。     

氧化钇稳定氧化锆涂层的研究现状

由于氧化钇稳定氧化锆(YSZ)陶瓷材料在作为热障涂层的使用过程中存在因抗烧结性能差、应力裂纹、涂层脱落等导致涂层失效的问题,本文主要从热障涂层的制备工艺,抗烧结性能、控制TGO的生长、抗CMAS腐蚀及YSZ面层应变容限等方面的改善方法进行论述,通过提高涂层纯度、改变粘接层及涂层成分、涂层结构及制备柱状结构YSZ陶瓷面层释放热失配应力等可有效改善涂层在使用过程中的失效问题。     

镍基高温合金用 AlSi/AlSiY涂层抗高温氧化性能研究

采用热浸镀的方法，在镍基高温合金 DZ125样品表面制备 Al、AlSi和 AlSiY三种不同的铝化物涂层，研究 1 000 ℃时涂层的抗高温氧化性能。利用扫描电子显微镜（SEM）以及能谱仪（EDX）对合金涂层的形貌以及元素成分分布进行观察分析。研究结果表明：在高温环境下， Al元素快速与氧反应生成氧化铝层。由于元素之间的相互扩散，纯 Al涂层中的 Al元素快速消耗，导致整个涂层的快速失效。 AlSi和 AlSiY涂层由于 Si富集层的形成，有效地阻止了元素的互扩散，提高了涂层的抗氧化性能。 AlSiY涂层中 Y元素的添加， Si富集层更加均匀致密，并且 Y与 Si、Cr、Mo电负性差值较大，更易形成稳定化合物，极大提高了涂层使用寿命。 AlSiY涂层的抗高温氧化性能更优于纯 Al和 AlSi涂层。     

Comparison of microstructure and mechanical properties of plasma-sprayed nanostructured and conventional yttria stabilized zirconia thermal barrier coatings

The main goal of this paper was to evaluate and compare the microstructure and mechanical properties of plasma-sprayed nanostructured and conventional yttria stabilized zirconia (YSZ) thermal barrier coatings (TBCs). To this end, NiCrAlY bond coat, nanostructured, and conventional YSZ coatings were deposited on Inconel 738LC substrate by atmospheric plasma spraying (APS). The mechanical properties of the coating were evaluated using nanoindentation and bonding strength tests. The microstructure and phase composition of the coating were characterized by field emission scanning electron microscopy (FESEM) and X-ray diffractometry (XRD). The nanostructured YSZ coating contained both nanosized particles retained from the powder and microcolumnar grains formed through the resolidification of the molten part of the powder, whereas the microstructure of the conventional YSZ coating consisted of columnar grain splats only. The phase composition of the as-sprayed nanostructured coating consisted of the non-transformable tetragonal phase, while the conventional coating showed the presence of both the monoclinic and non-transformable tetragonal phases. The results of nanoindentation and bonding strength tests indicated that the mechanical properties of the nanostructured coating were better than those of the conventional coating.     

Wetting,infiltration and interaction behavior of CMAS towards columnar YSZ coatings deposited by plasma spray physical vapor

Thermal barrier coatings (TBCs) produced by electron beam physical vapor deposition (EB-PVD) or plasma spray (PS) usually suffer from molten calcium-magnesium-alumino-silicate (CMAS) attack. In this study, columnar structured YSZ coatings were fabricated by plasma spray physical vapor deposition (PS-PVD). The coatings were CMAS-infiltrated at 1250?°C for short terms (1, 5, 30?min). The wetting and spreading dynamics of CMAS melt on the coating surface was in-situ investigated using a heating microscope. The results indicate that the spreading evolution of CMAS melt can be described in terms of two stages with varied time intervals and spreading velocities. Besides, the PS-PVD columnar coating (～100?μm thick) was fully penetrated by CMAS melt within 1?min. After the CMAS attack for 30?min, the original feathered-YSZ grains (tetragonal phase) in both PS-PVD and EB-PVD coatings were replaced by globular shaped monoclinic ZrO₂ grains in the interaction regions.     

Effect of molten V2O5 salt on the corrosion behavior of micro- and nano-structured thermal sprayed SYSZ and YSZ coatings

The corrosion resistance of micro-and nano-structured scandia and yttria codoped zirconia (nano-4 mol%SYSZ and micro-8.6SYSZ) and yttria doped zirconia (4YSZ) in the presence of molten vanadium oxide were investigated. To this end, duplex TBCs (thermal barrier coatings), composed of a bond coat (NiCrAlY) and a top coat (4SYSZ or 4YSZ), were deposited on the IN738LC Ni-based supper-alloy by atmospheric plasma spraying (APS). The corrosion studies of plasma sprayed TBCs were conducted in 25 mg V₂O₅ molten salt at 910 °C for different times. The nanostructured coating, as compared to its micro-structured counterpart, in spite of a further reaction with the V₂O₅ salt, showed a higher degradation resistance during the corrosion test due to increased compliance capabilities resulting from the presence of an extra source of porosity associated with the nano-zones. Finally, the corrosion resistance and degradation mechanism of SYSZ and YSZ coatings were compared with the presence of molten NaVO₃ and V₂O₅ salt, respectively.     

钛合金搪瓷涂层的制备与性能研究

在钛合金表面制备搪瓷涂层,并对其性能进行了研究。结果表明,搪瓷涂层具有较好的抗高温氧化性及抗热震性,能有效提高钛合金的抗腐蚀能力,使其在700°C熔融盐(Na2SO4+NaCl)浸没100h而免遭腐蚀。     

Columnar and DVC-structured thermal barrier coatings deposited by suspension plasma spray: high-temperature stability and their corrosion resistance to the molten salt

High-temperature stability of SPS YSZ coatings with the columnar and deep vertically cracked (DVC) structures and their corrosion resistance to 56 wt% V₂O₅+44 wt% Na₂SO₄ molten salt mixture were investigated. Both the columnar and DVC-structured YSZ coatings were sintered at 1000 °C, but a significant increase in porosity in combination with significant reductions in Vickers’ hardness and Young's modulus were observed at the temperatures from 1200 °C to 1400 °C. The DVC-structured YSZ coating exhibited superior corrosion resistance against the molten salt mixture attack to the columnar-structured one due to its higher density behaving as a sealing protective top layer at 950 °C.     

Microstructural study and hot corrosion behavior of bimodal thermal barrier coatings under laser heat treatment

In this study, nanostructured YSZ powders were deposited on the Hastalloy X Superalloy substrate coated with a metallic bond coat by plasma spraying to produce a nanostructured thermal barrier coating with bimodal microstructure. After that, the coated samples were heat-treated using a Nd:YAG laser. Then, the microstructures of the conventional and nanostructured TBCs before and after the laser glazing process were examined using a scanning electron microscope (SEM). The coating phases were studied by X-ray diffractometry (XRD). The high-temperature corrosion behavior of the nanostructured plasma sprayed coating in the presence of Vanadium pentoxide and Sodium sulfate molten salt was compared with that of the conventional coatings before and after laser treatment at 1050 °C. The hot corrosion results showed that the coatings had a similar degradation mechanism based on which the corrosive molten salt reacted with the stabilizer of YSZ, producing hot corrosion products such as YVO₄. It led to an unwanted phase transformation from tetragonal (t) to monoclinic (m) Zirconia and the final degradation of the TBC system. However, reducing molten salt penetration, decreasing surface roughness and, reduction of the specific surface area are three important mechanisms that improved hot corrosion resistance, finally extending the lifetime of the glazed samples. The results also showed that the nanostructured TBC had higher hot corrosion resistance in comparison with other samples.     

Effect of carbon nanotubes and aluminum oxide on the properties of a plasma sprayed thermal barrier coating

To protect the structural components of a power generating unit from the corrosive environment, thermal spray coatings are applied to the components. In the present work, four different types of thermal barrier coating (TBC) viz. partially stabilised zirconia (8YSZ), zirconia-20% alumina (ZA) composite coating without carbon nanotube (CNT) reinforcement, and ZA with 1% and 3% CNT reinforcement. The coating was deposited on NiCrAlY coated P91 steel using a plasma spraying process. The coating microstructure and phases were characterised using field emission scanning electron microscope (FE-SEM) with energy dispersive spectroscopy (EDS). The phases of the coating were analyzed using X-ray diffraction technique. The effect of CNT reinforcement on the thermal conductivity, porosity, and hardness of the composite coatings was investigated. The protective behavior of the coatings was characterised by potentiodynamic polarization testing and electrochemical impedance measurements. The thermal conductivity of the composite coating was found to be increased with increasing CNT content. Hardness was found to be highest for 3% CNT reinforcement and the thermal conductivity was found to increase with decreasing porosity. The electrochemical measurements indicate that reinforcement of CNT in zirconia alumina composite coating improved its corrosion resistance.     

Thermal stability and sintering behavior of plasma sprayed nanostructured 7YSZ, 15YSZ and 5.5SYSZ coatings at elevated temperatures

Nanostructured scandia, yttria doped zirconia (5.5SYSZ), 7 wt% yttria stabilized zirconia (7YSZ) and 15YSZ thermal barrier coatings (TBCs) were produced by plasma spraying on nickel-based superalloy substrates with NiCrAlY as the bond coat. The thermal stability and sintering behavior of the three as-sprayed TBCs at 1480 °C were investigated. The results indicated that the thermal stability of SYSZ and TBCs was longer than the 7YSZ TBCs due to higher amount of tetragonal phase. Furthermore, the results demonstrated that the nanostructured 7YSZ coating exhibits higher sintering resistance than 5.5SYSZ TBC.     

High temperature corrosion resistance of electrically conductive nitrogen doped silicon carbide ceramics in molten fluorides

Electrically conductive nitrogen-doped SiC ceramics were exposed to molten FLiNaK at 700 °C for 100, 200, and 500 h, and at 1000 °C for 100 h in Ar atmosphere. The SEM-EDX investigations of corroded samples showed that the main corrosion attack proceeds through the intergranular phase, where the fluoride melt interacts with the oxide phases and partly dissolves also the SiC grains. It was proved that N-doped SiC has good corrosion resistance against molten FLiNaK. After corrosion at 700 °C for 100, 200, and 500 h the corroded layer thicknesses were 85, 90, and 120 µm, respectively.     

Comparative study on thermal shock behavior of thick thermal barrier coatings fabricated with nano-based YSZ suspension and agglomerated particles

Two kinds of segmentation-crack structured YSZ thick thermal barrier coatings (TTBCs) were deposited by suspension plasma spraying (SPS) and atmospheric plasma spraying (APS) with nano-based suspension and agglomerated particles, respectively. The phase composition, microstructure evolution and failure behavior of both TBCs before and after thermal shock tests were systematically investigated. Microstructure of the APS coating exhibits typical segmentation-crack structure in the through-thickness direction, similar with the SPS coating. The densities of segmentation-crack in APS and SPS coatings were about 3 cracks mm⁻¹ and 4 cracks mm⁻¹_, respectively. The microstructure observation also showed that the columnar and equiaxed grains existed in the SPS coating. As for the thermal shock test, the spallation life of the APS TTBCs was 146 cycles, close to that of the SPS TTBCs (166 cycles). Failure of the APS coating is due to the spallation of fringe segments and splats.