低压等离子喷涂纳米YSZ涂层的结构及力学性能

采用低压等离子喷涂技术制备具有新型结构的纳米YSZ涂层,研究电弧电流和粉末松装密度对涂层微观结构以及力学性能的影响。结果表明,松装密度为0.95g/cm3的粉末在喷涂过程中因电流升高而引起的晶粒生长的程度远低于松装密度为1.4g/cm~3的粉体。当电流超过350A后,两种粉末所对应的涂层的Weibull模量分布均发生从二元结构向单一值的转变,但转变后涂层的结构均呈现出有别于传统涂层结构的细等轴晶结构。硬度与弹性模量的分析结果表明具有细等轴晶结构的涂层较在350A电流下形成的二元结构纳米涂层具有更高的平均硬度与弹性模量。当采用密度为1.4g/cm~3的粉末时,所对应涂层的断裂韧性Weibull曲线随电流波动较大。     

等离子喷涂纳米复合陶瓷涂层的组织结构及其形成机理

以Al2O3-13%TiO2(质量分数)团聚体复合陶瓷粉末为材料,采用等离子喷涂工艺在TiAl合金表面制备纳米结构陶瓷涂层.用扫描电镜(SEM)和X射线衍射仪(XRD)分析粉末和涂层形貌、微观结构及相组成,讨论涂层的微观组织形成机理.结果表明:纳米结构复合陶瓷涂层由部分熔化区以及与常规等离子喷涂类似的片层状完全熔化区组成;根据组织结构的不同,部分熔化区又分为液相烧结区(亚微米Al2O3粒子镶嵌在TiO2基质相的三维网状或骨骼状结构)和固相烧结区(经过一定程度长大但仍保持在纳米尺度的残留纳米粒子);等离子喷涂使部分α-Al2O3以及全部θ-Al2O3转变为亚稳态γ-Al2O3;纳米结构复合陶瓷涂层中的完全熔化区、液相烧结区及固相烧结区分别由等离子喷涂过程中纳米团聚体粉末中温度高于Al2O3熔点、介于TiO2熔点到Al2O3熔点之间以及低于TiO2熔点区域沉积获得,纳米结构涂层中不同部分熔化组织源于复合陶瓷粉末中Al2O3与TiO2之间的熔点差异.     

等离子喷涂纳米Al2O3-13TiO2陶瓷涂层研究

以常规和纳米团聚体Al2O3-13TiO2(ω/%,下同)复合陶瓷粉末为原料,采用等离子喷涂工艺在TiAl合金表面制备常规和纳米结构陶瓷涂层.用扫描电镜(SEM)和X射线衍射(XRD)仪分析粉末和涂层形貌、微观结构及相组成,同时对纳米结构涂层的微观组织形成机制进行了讨论.结果表明:常规复合陶瓷涂层呈典型的等离子喷涂层状堆积特征;纳米结构复合陶瓷涂层由部分熔化区以及与常规等离子喷涂类似的片层状完全熔化区组成.根据组织结构的不同,部分熔化区又分为亚微米A12O3粒子镶嵌在TiO2基质相的三维网状或骨骼状结构的液相烧结区和经过一定长大但仍保持在纳米尺度的残留纳米粒子的固相烧结区,不同的部分熔化组织源于复合陶瓷粉末中A12O3与TiO2之间的熔点差异.由于等离子喷涂过程中涂层沉积时的快速凝固作用,不管是常规还是纳米涂层都以亚稳相γ-A12O3为主.     

喷雾干燥法制备PS-PVD用8YSZ纳米团聚粉末

目的 通过喷雾干燥法制备用于等离子喷涂-物理气相沉积法（Plasma Spray-Physical Vapor Deposition,PS-PVD）多相沉积柱状/致密涂层的ZrO2-8%Y2O3 (8YSZ)纳米团聚粉末。方法 采用平均粒度为20 nm的8YSZ纳米粉为原料并配制成浆料,球磨后通过喷雾干燥法制备出8YSZ的纳米团聚粉末,并研究不同含量粘结剂（NJ-3）对粉末的影响。利用TEM、SEM表征粉末及涂层的微观结构。通过XRD、激光粒度及拉伸试验对粉末及涂层性能进行表征。结果 纳米8YSZ粉末在添加适当种类及含量的分散剂、粘结剂并通过喷雾干燥加工后,成功制备出球形度高、粒度小且适用于气/液/固多相沉积的PS-PVD用喷涂粉末。当粘结剂含量低于8%时,粉末球形度低,表面存在明显坑孔。而当粘结剂含量高于12%时,PS-PVD气相沉积效率低,涂层质量差。当粘结剂含量为10%时,粉末球形度高,D90=12.24 μm,可气/液/固多相沉积制备形貌良好的柱状涂层及致密涂层。其中气相沉积所制备柱状涂层结合强度可达33 MPa,且原始粉末中的m-ZrO2完全转变为t-ZrO2。结论 当粘结剂含量为10%时,所制备粉末能够流畅送粉,并进行气/液/固多相沉积,且涂层质量最优。粘结剂在粉末内部分布均匀,并主要起粘结和支撑作用,同时可改善粉末表面形貌。喷雾干燥后粉末粒度随着粘结剂含量增加而增大,但非线性变化。     

大气等离子喷涂的YSZ纳米热障涂层的微观结构

采用YSZ(8％Y2O3-Zr02，质量分数)纳米粉末，经大气等离子喷涂(APS)方法制备得YSZ纳米热降涂层(TBC)．喷涂前的粉末额粒直径为30—50nm，晶粒尺寸约12nm．对涂层的分析结果表明：YSZ纳米涂层平均晶粒尺寸在20—30nm，有个别粗晶直径达200—300nm．涂层由立方相c—ZrO2和四方相t′—ZrO2组成，t′相内存在畴结构．涂层内孔洞细小弥散，多呈闭合式．TEM下可见位错缠结和富层错的板条带结构．     

等离子喷涂纳米团聚体粉末的熔化特性研究

纳米陶瓷粉末(CYZ:ZrO2-4.5wt%Y2O3-25wt?O2和YSZ:ZrO2-8wt%Y2O3)经过团聚后,采用等离子喷涂(APS)方法在GH30高温合金表面制备热障涂层(TBC).用透射电镜(TEM)、扫描电镜(SEM)、场发射显微镜(FESEM)和X射线衍射仪(XRD)对团聚体粉末在等离子焰流中的熔化情况、制备的涂层组织结构进行了分析研究.结果表明:团聚后的球形粉末经过等离子弧后对于较大的团聚体颗粒只是表层约1μm被熔化,颗粒内部仍保持原始粉末的纳米结构;制备的涂层主要由熔化结晶部分和未熔化的纳米粒子构成,熔化结晶部分晶粒尺寸为60～80nm,大于原始粉末尺寸;CYZ涂层组成相为稳定的t相和c相,涂层中分布有大量的微裂纹和闭合的孔隙;两种涂层的孔隙率分别为6.2%和7.6%.     

金属喷涂、堆焊与修复——金属喷涂工艺与设备

富氧条件下电弧喷涂反应合成纳米氧化铝粉末;高速电弧喷涂FeCrNi／CBN复合涂层的组织与性能;含碳化物陶瓷粉芯丝材电弧喷涂层的结构和性能;应用于反应釜的超音速电弧喷涂涂层的耐蚀性;高速电弧喷涂涂层的结合强度与结合方式研究;等离子喷涂纳米团聚体粉末的熔化特性研究;等离子熔覆铁基涂层开裂行为研究。     

多功能微弧等离子喷涂技术

根据空气动力学和等离子喷涂理论,按照"一专多能"的设计指导思想,采用IGBT逆变技术、微电脑控制技术、软开关变换技术、拉瓦尔喷嘴和中心轴向送粉等,设计了多功能微弧等离子喷涂系统,且具有体积小、重量轻、抗干扰强、控制精确、喷涂粒子速度高、粉末沉积效率高等特点,可制备各种金属合金、金属陶瓷以及氧化物涂层.通过试验测定,多功能微弧等离子喷涂制备的纳米结构Al2O3 13%TiO2涂层的结合强度、显微硬度等性能优于9M等离子喷涂制备的纳米结构的Al2O3 13%TiO2涂层,这表明通过改进电源设计、喷枪结构设计、送粉方式等,低功率多功能微弧等离子喷涂能够与大功率等离子叶涂性能相当甚至更优异性能的涂层.     

不同尺度碳化物粉末冷喷沉积WC-17%Co涂层的组织及性能

采用团聚烧结和机械混合工艺制备的4种纳米与微米碳化物比例的WC-17%Co粉末,运用冷喷涂进行涂层定点沉积试验,通过扫描电镜和X-射线衍射分别分析了涂层的组织结构和相结构,并测定了涂层的显微硬度和磨粒磨损失重量.结果表明,4种碳化物尺度粉末沉积涂层具有致密的组织结构,喷涂态涂层保持与原始粉末相同的相结构,涂层显微硬度随碳化物尺度在12 897～15 925 MPa范围变化,粉末中纳米碳化物与微米碳化物颗粒重量比为50∶50时,沉积涂层具有较好的磨粒磨损性能.涂层磨损表面分析表明,涂层的磨损行为表现为涂层的磨粒磨损失重量在2.67～5.53 mg范围变化.     

电弧喷涂技术的现状与发展

介绍了电弧喷涂技术的发展历程、特点及应用，重点阐述了电弧喷涂材料及设备的研究现状与发展。指出粉芯丝材作为电弧喷涂材料新的发展方向，可以用其尝试获得非晶涂层、金属陶瓷涂层及纳米涂层。电源和喷枪是电弧喷涂设备的关键部件，逆变技术的应用是电弧喷涂电源的发展方向，而喷枪则向着高速、高效和稳定送丝的方向发展。     

Fabrication of conventional and nanostructured NiCrC coatings via HVAF technique

The conventional and nanostructured NiCrC （with chemical composition of 80%NiCr-20%CrC） coatings with high quality were fabricated via high velocity air-fuel（HVAF） spraying technique. The microstructures of these coatings were characterized by means of metallographic microscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffractometry. A Vickers microhardness tester was used to determine the mechanical properties of the as-sprayed coatings. The single-line approximation（SLA） method was employed to calculate the grain size and microstrain of as-sprayed nanostructured coating based on the XRD data. The results show that nanostructured NiCrC coating possesses a more uniform and denser microstructure, much higher microhardness and better fracture toughness than its conventional counterpart. Both TEM observation and calculation results based on XRD profile show that as-sprayed nanostructured NiCrC coating has a homogeneous nanocrystalline microstructure with an average grain size of 40 nm.     

Formation of nanostructured YSZ/Ni anode with pore channels by plasma spraying

YSZ/Ni is the conventionally most used material for making the anode of a solid oxide fuel cell. Agglomerated nanostructured YSZ/NiO powders and plasma spray are applied to produce nanostructured YSZ/NiO coatings on porous support substrates. After reduction in an ambient atmosphere of 7% hydrogen and 93% argon at about 800 °C for 4 hours, a novel SOFC anode with nanostructured characteristics such as nano YSZ particles, nano Ni particles, nano pores and nano pore channels is produced. This new YSZ/Ni anode provides larger triple phase boundaries for hydrogen oxidation reactions. X-ray diffraction patterns of these YSZ/NiO coatings after 1 h of heat treatment at temperatures from 700 to 1100 °C are obtained and Scherrer analysis is conducted to study the effect of temperature on grain size. The results obtained from SEM, TEM, XRD and EDX measurements and analyses are presented in this investigation.     

Microstructure and Thermal Characterization of Plasma-Sprayed Nanostructured La2Ce2O7-Doped YSZ Coatings

Nanostructured La₂Ce₂O₇-doped YSZ coatings were developed using atmospheric plasma-spraying technique by optimizing various process parameters. To ensure the retention of nanostructure, the molten state of nanoagglomerates was monitored using plasma and particle diagnostic tools. It was observed that the morphology of the coating exhibits a bimodal microstructure consisting of nanozones reinforced in a matrix of fully-molten particles. The thermal diffusivity of nano-LaCeYSZ coatings is lower than that of nano and bulk YSZ. The reason for this change in thermal diffusivity may be attributed to scattering of phonons at grain boundaries, point defect scattering and higher inter-splat porosity. Also, the thermal conductivity of the nanocomposite coatings was lower than those of nanostructured and bulk YSZ coatings. XRD results show cubic zirconia with a small amount of tetragonal zirconia. The average grain size of the as-sprayed La₂Ce₂O₇-YSZ nanocomposite coatings is ~150-200 nm. The improved thermal behavior is mainly due to a dense, packed, and more compact structure of the coatings.     

纳米氧化锆热障涂层组织结构和高温稳定性能分析

采用大气等离子喷涂技术制备了纳米氧化锆热障涂层.利用FESEM和XRD对纳米氧化锆热障涂层的微观组织和物相组成进行研究.微观组织分析结果表明,纳米氧化锆热障涂层展现出独特的微观复合结构,包括未熔纳米颗粒和柱状晶组织.物相分析结果表明,纳米氧化锆热障涂层主要由非平衡四方相组成.纳米氧化锆热障涂层高温稳定性能试验结果表明,涂层晶粒度随着服役温度和服役时间的增加而增加,但仍保持纳米结构;涂层物相组成不随服役环境的变化而变化.     

Transmission electron microscopy observation of microstructure of plasma-sprayed nanostructured zirconia coating

Nanostructured zirconia coatings deposited by plasma spraying technique were observed using transmission electron microscopy (TEM). It was found that the as-sprayed nanostructured zirconia coating had bimodal microstructures in terms of grain size distribution in the direction parallel to substrate surface. One was in the range 30–120 nm, which was the dominative structure of the coating, and the other was about 150–400 nm. The cross-section micrograph of the plasma sprayed nanostructured zirconia coating revealed that the coating still exhibited lamellar structure with columnar grains extending through its thickness. In conjunction with partially molten zirconia grains, amorphous regions were found. Domain structure and superlattice structure were observed in the plasma-sprayed nanostructured zirconia coating. The formations of the domain and superlattice structures are discussed in this paper.     

Nanostructured yttria stabilized zirconia coatings deposited by air plasma spraying

Nanostructured yttria partially stabilized zirconia coatings were deposited by air plasma spraying with reconstituted nanosized powder. The microstructures and phase compositions of the powder and the as-sprayed nanostructured coatings were characterized by transmission electron microscopy（TEM）, scanning electron microscopy（SEM） and X-ray diffxaction（XRD）. The results demonstrate that the microstructure of as-sprayed nanostructured zirconia coating exhibits a unique tri-modal distribution including the initial nanostructure of the powder, equiaxed grains and columnar grains. Air plasma sprayed nanostructured zirconia coatings consist of only the nontransformable tetragonal phase, though the reconstituted nanostructured powder shows the presence of the monoclinic, the tetragonal and the cubic phases. The mean grain size of the coating is about 42 nm.     

Microstructure and properties of Al2O3-13%TiO2 coatings sprayed using nanostructured powders

The microstructure and wear performance of M203-13% TiO2 coatings prepared by plasma spraying of agglom- erated nanoparticle powders were investigated. SEM analysis showed that the as-sprayed Al2O3-TiO2 coatings comprise of two kinds of typical region： fully melted region and unmelted/partially melted nanostructured region, which is different than the conventional coating with lamellar structure. It is shown that the microhardness of the nanostructured coatings was about 15%-30% higher than that of the conventional coating and the wear resistance is significantly improved, especially under a high wear load. The nanostructured coating sprayed at a lower power shows a lower wear resistance than the coatings produced at a higher power, because of the presence of pores and microstructural defects which are detrimental to the fracture toughness of the coatings.     

Structure and photocatalytic activity of TiO2 coatings deposited by atmospheric plasma spraying

Titanium dioxide coatings were deposited by utilizing an atmospheric plasma spraying (APS) system, at different spray parameters like argon flow rate and arc current. The structure and crystallite size of the as-sprayed TiO₂ coatings were characterized by X-ray diffraction (XRD) and Transmission electron microscopy (TEM). The photo-catalytic efficiency was determined in an environmental test chamber and evaluated from the conversion rate of ethanol. The as-sprayed TiO₂ coatings were photo-catalytically reactive for the degradation of ethanol and the photo-catalytic activity was influenced by spray conditions.     

高速电弧喷涂锌涂层性能研究

使用高速电弧喷涂枪和普通电弧喷涂枪分别制备锌涂层。通过对结合强度、孔隙率、粒子尺寸和粒子飞行速度的测试表明,高速电弧喷涂比普通电弧喷涂的粒子尺寸减小,飞行速度提高,制备的锌涂层结合强度高,孔隙率低。对两种锌涂层进行的强化腐蚀试验表明,封孔处理后的高速喷涂锌涂层具有较好的抗腐蚀性能。