等离子喷涂碳化钨涂层的静摩擦性能

叙述了等离子喷涂碳化钨(WC)涂层与不同材料组成摩擦副的静摩擦性能.结果显示,摩擦副的静摩擦系数与偶件的表面粗糙度和显微硬度相关.与WC涂层配对的偶件材料的显微硬度越低,摩擦副的静摩擦系数越高;提高WC涂层的粗糙度以及降低与WC配对的偶件材料的粗糙度可有效地提高摩擦副的静摩擦系数.     

Thermophysical Properties of Thermal Sprayed Coatings on Carbon Steel Substrates by Photothermal Radiometry

Laser infrared photothermal radiometry (PTR) was used to measure the thermophysical properties (thermal diffusivity and conductivity) of various thermal sprayed coatings on carbon steel. A one-dimensional photothermal model of a three-layered system in the backscattered mode was introduced and compared with experimental measurements. The uppermost layer was used to represent a roughness-equivalent layer, a second layer represented the thermal sprayed coating, and the third layer represented the substrate. The thermophysical parameters of thermal sprayed coatings examined in this work were obtained when a multiparameter-fit optimization algorithm was used with the backscattered PTR experimental results. The results also suggested a good method to determine the thickness of tungsten carbide and stainless-steel thermal spray coatings once the thermophysical properties are known. The ability of PTR to measure the thermophysical properties and the coating thickness has a strong potential as a method for in situ characterization of thermal spray coatings.     

Corrosion Behavior of Aerosol Thermal Sprayed ZrO2 Coatings

ZrO2 coatings of 2–7 m thickness were obtained by the aerosol thermal spraying process on 316L stainless steel. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) showed that these films consisted of nanocrystalline ZrO2 aggregates with a monoclinic structure. Corrosion tests were performed in aqueous NaCl (0.5 M) and H2SO4 (20 wt%) using potentiodynamic cyclic polarization curves. Surfaces and cross-sections of coated samples were compared with the uncoated substrate. This evaluation indicated decreased pitting of the steel with coating. The protection against corrosion in NaCl solution depended strongly on coating thickness. No protection was found for thicknesses less than 5 m. Meanwhile, a marked reduction of the current density was produced by thicker coatings that acted as an effective corrosion barrier. Coatings thicker than 5 m also provided significant protection against corrosion in H2SO4.     

热处理对热喷涂层接触疲劳性能和寿命影响的研究现状

热喷涂层由于其形成过程的特殊性,致使其内部不可避免地出现一些裂纹、孔隙等微观缺陷,对涂层的接触疲劳性能以及使用寿命产生了恶劣影响,因此极大限制了其应用及发展。热处理不但可以改善涂层表面完整性,而且还能提高其滚动接触疲劳性能和使用寿命。较全面地分析比较了重熔、化学热处理、热等静压等工艺的不同,综述了各工艺对涂层接触疲劳性能和寿命演变规律的影响,并展望了其未来的研究及发展方向,以期为涂层的接触疲劳寿命预测提供一定的理论支持和技术指导。     

等离子喷涂TiC-Graphite复合涂层摩擦磨损性能

等离子喷涂TiC涂层具有良好的综合性能, 在极端环境能起到较好的耐磨保护作用, 而石墨是一种优异的自润滑材料。通过喷雾干燥与真空烧结技术制备不同石墨添加量(1.25%、2.5%、5%和10%, 质量分数)的TiC-Graphite球形粉体, 并采用大气等离子喷涂技术制备TiC-Graphite复合涂层。对涂层的相组成、显微结构和力学性能进行了表征, 并对涂层的摩擦磨损性能进行了比较研究。结果发现, TiC-Graphite涂层主要由TiC和石墨相组成。随石墨添加量增大, TiC-Graphite涂层截面微裂纹增多, 表面粗糙度增大, 硬度下降。石墨对TiC涂层在高载荷的磨损性能影响更显著。在50 N高载荷条件, 随石墨添加量增大, TiC-Graphite涂层磨损率降低后急剧增大, 而摩擦系数持续减小。当石墨添加量为2.5%时, 涂层获得最低的磨损率为0.67×10^-5 mm³/(N·m), 同时具有较低的摩擦系数(0.35), 与不添加石墨的TiC涂层相比, 分别降低了72.4%和27.8%。     

制备参数对等离子喷涂热障涂层高温冲蚀性能的影响

燃机热端部件热障涂层实际服役过程中不可避免发生高温冲蚀,引起涂层失效。采用等离子喷涂工艺制备不同喷涂距离、不同喷涂功率的热障涂层,并对其进行1 000℃/60°高温冲蚀试验,研究制备参数对热障涂层耐高温冲蚀性能的影响规律。结果表明:42 kW功率制备涂层,随喷涂距离的增加(110,120,130 mm),涂层耐高温冲蚀性能降低,冲蚀率显著增大(31.40,45.11,76.79 mg/g);110 mm喷涂距离下制备涂层,随喷涂功率的增加(39,42 kW),涂层耐高温冲蚀性能提高,冲蚀率减小(58.86,31.40 mg/g);涂层力学性能是影响其高温冲蚀性能的重要因素。     

等离子喷涂纳米结构与传统结构热障涂层的残余应力对比研究

热障涂层的残余应力是影响其服役寿研究不多.在45钢基体上,用超音速火焰喷涂NiCocrAlY打底层,再用大气等离子喷涂ZrO2-8%(质量分数)Y2O3(8YSZ)工作层,制备了纳米结构与传统结构2种类型的热障涂层(TBC).采用SEM、XRD对这2种涂层的粉末及涂层进行了组织结构分析,用纳米压痕仪测得了2种涂层的弹性模量.用X射线衍射应力测试仪测得了2种涂层的表层残余应力.结果表明:喷涂工艺参数相同条件下,对于打底层及工作层的厚度均相同的2种涂层,纳米结构热障涂层的表层残余应力比传统结构热障涂层约低24.7%;相同打底层的纳米结构热障涂层表层残余应力随着陶瓷层厚度增加而增加,陶瓷层厚度在240 um以下时,表层为残余压应力;厚度超过300 um时,表层为残余拉应力.最后提出了相应的物理力学模型.     

钴铁氧体纳米管阵列制备及其磁学性能(英文)

为了研究一维钴铁氧体纳米管阵列的磁学性质,应用氧化铝模板具有的约束作用和毛细管作用,结合溶胶凝胶技术合成了钴铁氧体纳米管阵列.在140℃条件下,通过包含Fe(AO)3和Co(AO)2(物质的量之比为2∶1)的柠檬酸和乙二醇混合溶液(物质的量之比为1∶4)酯化反应得到溶胶.将氧化铝模板浸入溶胶几次后取出,取出充满溶胶的氧化铝模板,在大气气氛中,以0.6℃/min～5℃/min的升温速度将样品由室温升温至500℃,保温8 h.结果表明,在控制Fe3+离子浓度的条件下也可以合成钴铁氧体纳米线(Fe3+离子浓度大于1 mol/L)和"竹节"型纳米管(Fe3+离子浓度介于0.5 mol/L～1.0 mol/L),但重点进行了其纳米管阵列(Fe3+离子浓度小于0.5 mol/L)合成和磁学性能测试.透射电子显微镜(TEM)、高分辨电镜(HRTEM)的观察以及粉末X光衍射(XRD)测试结果表明纳米管组成为多晶结构.纳米管的直径取决于氧化铝模板的孔径,大约为200 nm,其长度约几个微米.应用样品振动磁强计对样品磁性进行了表征,结果表明纳米管阵列未表现出方向特性,矫顽力随着升温速率的降低而升高,在0.6℃/min的升温速率时,矫顽力达到最高的1 445 kOe,简单讨论了其形成原因.     

Experimental Investigation on the Reliability of Thermal Wave Interferometry in the Thermophysical Characterization of Plasma Sprayed Coatings

The main focus of this work is to compare thermal diffusivity and effusivity data resulting from thermal wave interferometry (TWI) experiments on tungsten coatings of different thicknesses with those obtained using reference techniques, namely, the laser flash method and scanning electron microscopy (SEM). The deviations between TWI and the latter techniques are discussed in terms of lack of data in the low frequency range. The investigation shows that the lack of data at low frequencies does not affect diffusivity measurements, while it has a strong effect on effusivity measurements for thermally thick coatings. The conclusions of this experimental study are in good agreement with theoretical predictions resulting from a sensitivity analysis reported in a previous study.     

等离子喷涂ZrO2涂层显微结构表征和热导率分析（英文）

利用大气等离子喷涂制备了ZrO2涂层,采用扫描电子显微镜结合图像分析的方法对涂层的显微结构特征(总气孔率和大气率)进行了量化表征.同时利用扫描电子显微镜附带X射线扫描成像对涂层内部的微裂纹和大的分隔裂纹的三维分布进行了表征.据此建立了ZrO2涂层显微结构与热导率之间的关系.室温下,涂层N2的热导率较N1的低,因为涂层N2内气孔和微裂纹数较多;在1000℃,由于微裂纹的烧结作用导致热导率增大,所以涂层N2的热导率较N1反而高.高温下,涂层内由微裂纹汇聚而形成的大的分隔裂纹的存在则可以有效地抑制烧结,降低涂层的热导率.     

Thermal Radiative Properties and Temperature Measurement from Turbine Coatings

Recent studies have displayed the spectral radiative properties of ceramic thermal barrier coatings which are finding applications in high performance turbine engines. As a function of temperature, a region in the long wavelength infrared spectrum exhibits properties which will minimize the classical errors associated with temperature measurement by radiometric detection. Hollow sapphire waveguides transmit the portion of the long wavelength infrared spectrum which is optimum for radiometric temperature measurement from these materials, while the physical properties of the sapphire can withstand the combustion conditions within the engine. A prototype long wavelength infrared radiation thermometer was constructed to obtain surface temperature measurements from coated turbine blades subjected to high temperature combustion conditions.     

Template‐Free Pseudomorphic Synthesis of Tungsten Carbide Nanorods

A unique nanorod‐structured tungsten carbide material with high specific surface area of 198 m² g^?1 is successfully synthesized for the first time by pseudomorphic transformation of chemically synthesized WO₃ nanorods through a high‐temperature method. An electrocatalyst composed of Pt nanoparticles supported on WC nanorods demonstrates higher electrocatalytic activity for methanol electro‐oxidation, better tolerance to CO poisoning, and superior performance for cathodic electrocatalytic hydrogen evolution than a Pt/C catalyst. This work provides a novel method to synthesize high‐surface‐area nanorod‐structured WC materials by preparing oxide precursors with the desired external morphology, thus offering great potential for a broad range of applications of these materials in related reaction systems.     

真空等离子喷涂碳化硼涂层制备与抗激光辐照性能研究

采用真空等离子喷涂技术,在不锈钢基体上制备碳化硼(B₄C)涂层,并对涂层的组成、结构、沉积效率、结合强度以及抗激光辐照性能进行了表征.结果显示,真空等离子喷涂B₄C涂层中没有出现明显的B₂O₃相,表明真空等离子喷涂可有效避免B₄C氧化现象.采用较细的粉末制备的B₄C涂层较为致密.较高的喷涂功率和较大的氢气流量,有助于改善粉末的熔化程度,从而提高涂层的沉积效率和结合强度.在适宜的工艺参数下,涂层的沉积效率与结合强度可分别达72%与49MPa.激光辐照试验表明,在不锈钢表面沉积B₄C涂层,可以明显改善其抗激光辐照性能.     

热喷涂金属陶瓷复合涂层研究进展

从喷涂方法、粉末特性和工艺参数三个方面介绍了金属陶瓷复合涂层制备、组织结构及综合性能的最新研究进展.同时认为这三个方面综合控制着热喷涂过程中陶瓷相的分解、氧化以及复合粉末的沉积行为,并由此对复合涂层的组织结构、力学性能和摩擦磨损性能具有重要影响.在此基础上,选择合适的喷涂方法和复合粉末,优化喷涂工艺是获得优良性能的金属陶瓷复合涂层的关键.     

热喷涂制备二氧化钛涂层中锐钛矿相调控的研究进展

二氧化钛(TiO_2)涂层在许多领域具有重要的应用价值,如光催化降解和光电池,近年来引起了相关研究者的广泛关注。在众多涂层制备技术中,热喷涂技术可以快速、高效、大面积、大批量地制备TiO_2涂层,且得到的涂层力学性能良好,喷涂成本较为低廉,因而使热喷涂TiO_2涂层的应用更具前景。TiO_2涂层的晶相组成是影响涂层最终性能的一个重要因素,而控制涂层中晶相组成的关键是调控亚稳态的锐钛矿相含量。综述了近些年来国内外制备TiO_2涂层常用的热喷涂技术,如传统粉末热喷涂、液料热喷涂以及冷喷涂等,分别阐述了不同热喷涂技术中通过调节一些重要参数达到调控涂层中锐钛矿相的方法,并讨论了材料掺杂对TiO_2涂层中锐钛矿相的影响,指出了目前调控涂层中锐钛矿相存在的问题和后续的研究方向。     

热障涂层热冲击试验研究

随着先进发动机的研制和生产,对高温涂层的要求也不断提高。热障涂层（TBCs) 作为一种新型隔热涂层,在发动机涡轮叶片上的应用得到更多的重视。对利用电子束物理气相沉积（EB－PVD）制备的TBCs进行了高温热冲击试验,并对试验前后的TBCs进行了形貌、SEM和XRD分析。     

非烧蚀防隔热材料表面热防护涂层的研究进展

防隔热材料在高速飞行器中扮演着重要的角色,而其表面热防护涂层更是决定高速飞行器能否成功运行的关键。从制备、机理和性能等方面回顾了不同类别非烧蚀防隔热材料表面热防护涂层的研究进展和应用现状,总结了传统热防护涂层存在的问题,并对未来航天领域的热防护涂层的研究进行了展望。