电子束重熔对机械合金化法制备TiC/Ti复合涂层组织及摩擦性能的影响

对机械合金化（MA）法制备的TiC/Ti复合涂层进行电子束重熔处理,分析了经过不同电子束扫描速度的重熔工艺后TiC/Ti复合涂层组织和耐磨性能的变化规律。结果表明,当扫描速度为5~15 mm/s时,重熔处理消除了MA法制备的TiC/Ti复合涂层中的孔隙和裂纹,使其硬度与耐磨性能显著提高;但扫描速度过快（20 mm/s）时,TiC/Ti复合涂层内部出现重熔导致的孔洞缺陷。随着扫描速度由5 mm/s增加至15 mm/s,重熔后TiC/Ti复合涂层中的TiC相由粗大树枝状晶体逐渐转变为弥散分布的短棒和颗粒状晶体,弥散强化作用和固溶强化作用逐渐增强,TiC/Ti复合涂层的硬度由重熔前HV 554逐渐提高至HV 783,磨损速率由5.93×10-4 mm3（N·m）-1逐渐下降至1.75×10-4 mm3（N·m）-1,扫描速度为15 mm/s重熔后TiC/Ti复合涂层的性能最佳。      

脉冲电子束作用下热障涂层微观结构及热循环性能

利用强流脉冲电子束(HCPEB)技术对大气等离子喷涂(APS)技术制备的热障涂层(TBCs)进行表面处理,探究HCPEB辐照对TBCs微观结构以及热循环性能的影响。热循环实验采用950℃炉温加热并随后水淬。采用X射线衍射,扫描电子显微镜详细分析了辐照前后涂层表面微观结构及相组成。X射线分析结果表明,HCPEB辐照后陶瓷层中单斜相m相含量降低;此外,衍射峰发生宽化及偏移说明伴随有晶粒细化以及残余应力产生。微观结构观察表明,HCPEB辐照后热喷涂缺陷消失,涂层发生重熔,涂层表面粗糙度降低,且重熔层内部有网状垂直微裂纹以及柱状晶产生。热循环实验表明,250次热循环后原始涂层发生整体剥落,涂层失效;而HCPEB辐照后涂层并未出现明显的剥落迹象,仅存在水平裂纹的扩展,涂层的热循环寿命明显提高。     

等离子喷涂涂层重熔后处理的研究现状与展望

鉴于喷涂涂层存在的较高孔隙率和较大残余应力而常常需要进行适当的后处理,介绍了等离子喷涂涂层的几种重熔后处理技术,对各种处理方式进行归纳总结,并分析了各种处理方式的优缺点。对未来喷涂涂层重熔后处理技术进行展望,提出了根据涂层性质选择合适后处理方式、进一步优化后处理工艺、建立涂层寿命监测系统并进行涂层失效预测等提高涂层使用性能的建议。有关研究说明：喷涂涂层的激光重熔后处理技术能让涂层与基体间由机械结合为主转为以冶金结合为主,可有效增强涂层的硬度、耐磨性、耐腐蚀性及抗高温氧化性等,且其选材的来源广泛,热影响区和工件的变形量较小,但激光重熔时涂层易出现裂纹,因此不宜对大面积涂层进行激光重熔后处理;喷涂涂层的感应重熔后处理技术热影响区较小,可消除涂层中的气孔和微裂纹,有效增强涂层的耐磨性和耐腐蚀性,但感应重熔过程会受到涂层自身电阻率的限制而降低重熔后处理的效率;喷涂涂层的电子束重熔后处理技术适用范围广,成本较低,无污染,可有效提高涂层的硬度、耐磨性和抗氧化性能,减少涂层间的气孔,降低涂层表面的粗糙度,但电子束重熔过程对工作环境要求较高;喷涂涂层的火焰重熔后处理技术操作简单、成本较低,喷涂涂层的钨...     

TiAl合金表面激光重熔热障涂层组织及抗高温氧化性能

为了进一步提高TiAl合金表面等离子喷涂ZrO2-7%(质量分数)Y203热障陶瓷涂层的性能,采用激光重熔工艺对涂层进行处理,研究了激光重熔对涂层微观组织和抗高温氧化性能的影响.用扫描电镜(SEM)分析了涂层形貌和微观结构,同时对其抗高温(850℃)氧化性能进行了考察.结果表明,等离子喷涂热障陶瓷涂层呈典型的层状堆积特征,有一定的孔隙且分布有微裂纹;经过激光重熔处理后,陶瓷涂层片层状组织得以消失,致密性提高,获得了基本没有裂纹等缺陷的重熔层;整个重熔层包括界面没有明显特征的平面晶和上部沿热流方向生长的柱状晶组织.等离子喷涂热障涂层具有较好的抗高温氧化性能,经过激光重熔后可进一步提高其抗高温氧化能力.     

倾斜陶瓷耐热涂层的研究

报道了Ｃｕ材表面喷涂斜陶瓷耐热涂层的组织及其性能，介绍了一种火焰喷涂陶瓷基复合涂层的新方法－－倾斜过渡和重熔层法。实验结果表明：涂层间有扩散反应和液相烧结、涂层具有良好的结合强度、耐热蚀和抗热震性能。采用倾斜陶瓷涂层，可使高炉渣口寿命提高２倍。     

Al-Zn-Mg-Cu合金表面Al2O3-MoO2-SiO2微弧氧化复合陶瓷涂层的制备及其耐腐蚀性能

为了增强Al-Zn-Mg-Cu合金零件的耐腐蚀性能,通过在硅酸盐微弧氧化(MAO)电解液中增加钼酸根离子的方法,在合金表面制备了Al2O3-MoO2-SiO2复合陶瓷涂层.通过扫描电子显微镜、X射线衍射和电化学方法分析了钼酸钠的浓度对复合陶瓷涂层的形成、结构特征以及耐蚀性的影响.涂层的扫描电子显微镜(SEM)结果显示:经过15 min的MAO处理后,制备的Al2O3-MoO2-SiO2复合陶瓷涂层由约2μm厚的致密内层和约5μm厚的多孔外层组成,涂层表面出现了2种不同的形貌区域.X射线衍射结果表明:Al2O3-MoO2-SiO2复合陶瓷涂层主要由MoO2、γ-Al2O3和3Al2O3-2SiO2组成.电化学试验表明:当电解液中加入3 g/L钼酸盐时,涂层的孔隙率降低了4个数量级,涂层的腐蚀速率降低约100倍,表现出最好的耐腐蚀性能.     

碳化物衍生碳涂层的表面划痕织构能降低摩擦(英文)

研究了碳化物衍生碳涂层表面的划痕对其摩擦学性能的影响。扫描电子显微镜形貌图证实碳化硅基底的划痕为V-型和U-型,氯化处理后得到的碳化物衍生碳涂层的表面划痕也有相似的形貌。在干摩擦和水润滑条件下,与研磨处理的碳化物衍生碳涂层相比,未研磨处理的碳化物衍生碳涂层与氮化硅陶瓷对摩时表现出更加优异的摩擦学性能。在水润滑条件下,未研磨处理的碳化物衍生碳涂层与氮化硅陶瓷对摩时的摩擦系数仅为0.05,且比经研磨处理的碳化物衍生碳涂层的摩擦系数低。主要归因于未研磨的碳化物衍生碳涂层表面的划痕产生的流体润滑作用,而经研磨处理后的碳化物衍生碳涂层上不存在这种机制。碳化物衍生碳涂层表面的划痕有利于降低碳化物衍生碳涂层在水中与氮化硅陶瓷对摩时的摩擦。     

超音速火焰喷涂Cr3C2-NiCr层激光重熔后的冲蚀性能

利用激光重熔技术对超音速火焰喷涂(HVOF)涂层进行改性处理,可改善涂层质量.采用HVOF技术在低碳钢表面喷涂Cr3C2-NiCr层,然后对其进行激光重熔处理,考察了熔覆后涂层的冲蚀性能.结果表明:HVOF层激光重熔后以不同角度冲蚀,30°冲蚀时冲蚀率最大,表现为塑性材料的冲蚀性能;激光重熔HVOF层在冲蚀初期冲蚀率较大,随着冲蚀次数的增加,冲蚀率降低,冲蚀性能最终优于低碳钢和HVOF层;HVOF层激光重熔后致密性提高.     

超高温陶瓷涂层的研究进展

综述了近年来超高温陶瓷涂层的研究现状及其在航空航天领域的应用,归纳了常用的硅化物涂层、碳化物涂层、硼化物涂层、氧化物涂层以及复合涂层的研究进展。从其结构、性能及作用机理等方面进行了阐释,并对超高温陶瓷涂层的发展方向进行了展望。     

激光重熔过程中激光功率对镁合金表面等离子喷涂YSZ涂层结构的影响

为了提高铝合金的综合性能,采用等离子喷涂技术在AZ31B镁合金表面沉积氧化钇部分稳定二氧化锆(YSZ)涂层,并采用二氧化碳激光器对涂层表面进行重熔处理,利用X射线衍射仪、扫描电镜及三维激光成像显微镜研究了重熔激光功率对涂层物相组成、组织结构及表面形态的影响规律。结果表明:YSZ涂层在激光表面重熔过程中保持了相结构的稳定性,即喷涂态及激光重熔后的涂层均由非转变型的四方相组成;随激光功率的增大,重熔区厚度不断增加,且喷涂态涂层的层状组织结构在激光重熔后消失,气孔率降低;在激光处理过程中,产生了大量的内应力,导致纵向(垂直于涂层表面)裂纹的萌生及扩展;涂层表面粗糙度随激光功率的增加而不断降低,并且在功率低于400 W时下降更明显。     

表面粗糙度对PS-PVD热障涂层陶瓷层沉积的影响

研究基于等离子喷涂-物理气相沉积(PS-PVD)工艺的沉积表面的粗糙度对YSZ陶瓷层结构的影响,初步阐明了表面粗糙度对陶瓷层气相沉积过程的影响和涂层结构的形成规律。采用PS-PVD工艺在预制有NiCoCrAlYTa黏结层的K417G高温合金上制备YSZ陶瓷层;采用SEM、粗糙度检测仪、3D表面形貌仪等方法分析PS-PVD YSZ陶瓷涂层的形貌和结构特征。基体表面粗糙度对PS-PVD涂层结构有很大影响。结果表明:当基体表面粗糙度分别为 R a≤2μm, 2μm< R a<6μm, R a≥6μm时,涂层粗糙度分别在3.5~5,6~10,10~15μm区间;特征表面形貌"菜花头"的直径随着基体表面粗糙度的增加而逐渐增大, d P=38.5μm, d 280S =25.5μm, d 60S =38.7μm, d 24S =102μm, d S=137μm。表面粗糙度主要通过PS-PVD气相沉积过程中的阴影效应来影响涂层生长和形成差异性结构,随着基体表面粗糙度的增加,YSZ陶瓷层受阴影效应影响增大,表面形貌"菜花头"尺寸和柱状结构间间隙增大,形成更加疏松的结构。     

Patterning the mechanical properties of hydrogen silsesquioxane films using electron beam irradiation for application in mechano cell guidance

Hydrogen silsesquioxane (HSQ) is a material with the potential for studying the effect of surface stiffness on stem cell differentiation. Here, the effects of electron beam dose on the topography and the mechanical properties of HSQ obtained with or without trimethylamine (TMA) development are characterised by atomic force microscopy imaging and indentation. A correlation between the surface stiffness (uniform across the sample) and electron beam exposure is observed. Surface roughness of HSQ samples developed in TMA decreases exponentially with increasing electron beam exposure. Surface coating with plasma polymerised allylamine (ppAAm) leads to an overall decrease in stiffness values. However, the increase in surface stiffness with increasing electron beam exposure is still evident. The ppAAm coating is shown to facilitate human mesenchymal stem cell adhesion.     

电子束表面改性技术质量控制与性能影响分析

电子束表面改性技术能够赋予材料优异的表面性能,具有广阔的应用前景。分别从裂纹、气孔、表面粗糙度、改性层与基体结合强度等方面综述了材料电子束表面改性层性能研究现状,并从抗氧化性能、耐磨损性能、抗腐蚀性能、断裂韧性方面综述了电子束表面改性对材料表面性能的影响,简要介绍了用于电子束表面改性的设备,并展望了该项技术的发展前景。     

SINTERING AND COATING OF CERAMICS USING CARBON DIOXIDE LASER

Laser sintering and ceramic coating techniques for synthesis of new ceramics have been investigated. The laser sintering method is useful instead of furnace treatment for the densification of materials having high melting points. The new ceramics, ZrO₂-V₂O_-HfO₂ which have a melting point of 2850^°C and a hardness of about 1850 kgf/cm have been sintered. The single crystal of AI₂O₃3WO₃ was found to form under nonequilibrium states in the Al₂O₃-WO₃ system. A ceramic coating that forms a solid electrolyte layer of a fuel cell was also developed. The laser beam was parallel to the substrate surface on which melted ceramics were deposited by a powder gun. The properties of the coated layer are discussed with the melted particles passing through the laser beam     

烧结温度对3D打印硅基陶瓷型芯表面形貌及粗糙度的影响

单晶高温合金空心叶片是航空发动机的重要部件, 其内腔结构是采用陶瓷型芯制备的。随着航空发动机推重比提高, 型芯结构越来越复杂, 传统制备工艺受限, 光固化3D打印陶瓷型芯技术为复杂结构型芯的制备提供了一种可行方案。为了改善光固化3D打印陶瓷型芯因台阶效应导致的表面粗糙度较大的问题, 本研究利用固含量体积分数63%的硅基型芯浆料进行光固化3D打印型芯, 并在1100~1300 ℃对型芯素坯进行烧结, 对烧成的硅基陶瓷型芯的微观结构、元素分布、相组成、型芯打印面和打印堆积方向的表面形貌和粗糙度进行分析。研究发现型芯打印面平整, 无明显表面缺陷, 1100、1200和1300 ℃烧结型芯的打印面粗糙度分别为1.83、1.24和1.44 μm; 片层堆积方向的表面有片层结构特征, 片层间出现微裂纹, 1200 ℃以上烧结的型芯表面粗糙度达到空心叶片使用要求(R_a≤2.0 μm)。结果表明不同烧结温度会改变型芯烧结过程中的液相含量、莫来石生成量、莫来石生成形态和颗粒间玻璃相的分布, 从而对光固化3D打印硅基陶瓷型芯的表面粗糙度产生明显影响。光固化3D打印陶瓷型芯技术结合烧结工艺能制备出满足先进空心叶片用硅基陶瓷型芯表面要求的粗糙度。     

Study on the fabrication accuracy of ceramic parts by direct stereolithography

Parameters in the stereolithography, drying, and sintering processes of ceramic components had significant influences on the fabrication accuracies. Taguchi's experimental design method was utilised to investigate the relationships between parameters and the fabrication accuracies. In the stereolithography process, line-width compensation had a significant influence on the part's dimensions. On the contrary, scanning speed had an insignificant effect. The vacuum-freeze drying method was used to decrease shrinkage (less than 2.0%) in the drying process. Sintering temperature was the most important factor in the sintering process. According to analysis of the influence of the ladder effect on surface roughness, small layer thickness and large inclination angle (more than 30°) were proposed to improve the surface quality of the produced ceramic parts.     

表面粗糙度对PS-PVD YSZ陶瓷层性能的影响EI北大核心CSCD

采用PS-PVD工艺在预制有NiCoCrAlYTa黏结层的K417G高温合金上制备YSZ陶瓷层;采用万能拉伸试验机、粒子冲刷仪、静态氧化炉等设备测试PS-PVD YSZ陶瓷涂层的结合强度、抗粒子冲刷和抗高温氧化性能;采用SEM和EDS分析涂层表面、截面形貌和元素分布等。结果表明:表面粗糙度对YSZ陶瓷层拉伸结合强度、抗粒子冲刷和抗高温氧化性能的影响很大。随着粗糙度的增大,结合强度先增大而后减小。Ra=0.40μm表面上沉积的YSZ涂层,其结合强度最高,达到23.5 MPa。拉伸断裂发生在涂层内部,并距离黏结层40~70μm的位置。随着表面粗糙度的增大,冲刷速率先减小而后增大,Ra=0.40μm涂层的抗粒子冲刷性能最好,冲刷速率仅为2.8×10^-3 g/g,表面起伏小和孔隙率低是涂层具有良好抗粒子冲刷性能的重要原因。不同表面粗糙度制备的YSZ涂层均能生成致密连续的热生长氧化物(TGO)层。粗糙度大则生长的TGO起伏大,更容易导致局部增厚和应力集中而失效。     

热震中7YSZ热障涂层结构演变

采用低温超音速等离子喷涂(LT-HVOF)在镍基高温合金基体上制备了NiCoCrAlYTa粘结层, 使用大气等离子喷涂(APS)在粘结层上`制备了7wt%Y₂O₃-ZrO₂ (7YSZ) 陶瓷层。基于动态试验即热震实验研究了粘结层的扩散氧化机制, 探讨了陶瓷层的烧结及相变过程并观察了涂层的结构演变。实验结果表明: 动态热循环下随着热震次数的增加, 粘结层组元扩散氧化形成热生长氧化物(TGO)且厚度逐渐增加。此外, 粘结层组元在温度梯度下沿陶瓷层内部裂纹向高温区扩散, 最终在陶瓷层表面裂纹区域出现大量的金属氧化物, 同时粘结层组元的扩散有助于陶瓷层的烧结, 导致其显微硬度逐渐增大, 而粘结层由于Kirkendall效应, 其内部出现大量的孔洞导致其显微硬度逐渐降低。另外, 陶瓷层在相变及热循环应力的作用下表面出现了大尺度的宏观裂纹。     

AFM and SEM characterization of iron oxide coated ceramic membranes

Alumina–zirconia–titania (AZT) ceramic membranes coated with iron oxide nanoparticles have been shown to improve water quality by significantly reducing the concentration of disinfection by-product precursors, and in the case of membrane filtration combined with ozonation, to reduce ozonation by-products such as aldehydes, ketones and ketoacids. Commercially available ceramic membranes with a nominal molecular weight cut-off of 5 kilodaltons (kD) were coated 20, 30, 40 or 45 times with sol suspension processed Fe₂O₃ nanoparticles having an average diameter of 4–6 nm. These coated membranes were sintered in air at 900 °C for 30 min. The effects of sintering and coating layer thickness on the microstructure of the ceramic membranes were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). AFM images show a decreasing roughness after iron oxide coating with an average surface roughness of ∼161 nm for the uncoated and ∼130 nm for the coated membranes. SEM showed that as the coating thickness increased, the microstructure of the coating changed from a fine grained (average grain size of ∼27 nm) morphology at 20 coating layers to a coarse grained (average grain size of ∼66 nm) morphology at 40 coating layers with a corresponding increase in the average pore size from ∼57 nm to ∼120 nm. Optimum water quality was achieved at 40 layers, which corresponds to a surface coating morphology consisting of a uniform, coarse-grained structure with open, nano-sized interconnected pores.     

Effects of Current Frequency on the Microstructure and Wear Resistance of Ceramic Coatings Embedded with SiC Nano-particles Produced by Micro-arc Oxidation on AZ91D Magnesium Alloy

To improve the surface wear resistance of the ceramic coating fabricated by micro-arc oxidation (MAO) on AZ91D magnesium alloy,ceramic coatings embedded with SiC nano-particles at different current frequency (500 Hz,700 Hz,and 900 Hz) were produced during the MAO process.The morphology and phase composition of the coatings were investigated by scanning electron microscopy (SEM),field emission scanning electron microscopy (FESEM),and X-ray diffraction (XRD).The surface roughness of the coatings was character...