纯钛表面超细晶组织的扫描热显微镜分析

通过喷丸处理方法在纯钛表面形成一定厚度的超细晶组织(纳米及亚微米组织),利用扫描热显微镜(SThM)对超细晶组织的热性能进行分析。在实验基础上建立理论模型。根据从SThM扫描探针针尖传输到试样各种组织中的热流变化,分析材料的热导率与组织的变化关系。结果表明,超细晶组织的热导率与具有较大晶粒的基体相比有明显的降低,其原因主要与细晶组织中导电电子浓度的降低、晶格缺陷密度的增加及电子与声子在该类组织中的强烈散射有关。     

等离子体喷涂纳米结构热障涂层微观组织及性能

以纳米结构氧化钇部分稳定的氧化锆热喷涂粉末为原料,采用大气热等离子体喷涂法制备了纳米结构热障涂层。利用扫描电子显微镜和X射线衍射仪对粉末原料及涂层的微观组织和结构进行分析,并对涂层的结合强度及热导率进行测定。结果表明,纳米结构热障涂层具有优异的性能,热导率为1.1 W/(m.K),界面结合强度为47 MPa。并分析了涂层纳米结构组织对涂层性能的影响,明确了优化涂层微观组织结构和提高涂层性能的具体方法。     

NiCrCoAlY粘结层表面等离子喷涂(La_(0.4)Sm_(0.5)Yb_(0.1))_2-Zr_2O_7涂层的热性能研究（英文）

采用大气等离子喷涂制备了(La_(0.4)Sm_(0.5)Yb_(0.1))_2-Zr_2O_7(LSYZO)涂层,并在相同的条件下制备了Sm_2Zr_2O_7涂层作为对比。分别用扫描电子显微镜(SEM)和X射线衍射仪(XRD)分析LSYZO涂层的微观形貌和相结构,并对2种涂层的热导率进行测定。结果表明,等离子喷涂后LSYZO涂层的相结构未发生变化。LSYZO涂层的结合强度为22 MPa,与SZO涂层相当。LSYZO涂层热震40次后发生失效,其热导率明显低于SZO涂层,这主要与LSYZO陶瓷自身的复杂结构有关。     

等离子喷涂(La0.4Sm0.5Yb0.1)2Zr2O7涂层的热性能研究

本文采用大气等离子喷涂制备了(La0.4Sm0.5Yb0.1)2Zr2O7涂层,并在相同的条件下制备了Sm2Zr2O7涂层作为对比。分别用扫描电子显微镜和X射线衍射仪分析 LSYZO涂层的微观形貌和相结构,并对两种涂层的热导率进行测定。结果表明,等离子喷涂后LSYZO涂层的相结构未发生变化。LSYZO涂层的结合强度为22 MPa,与SZO涂层相当。LSYZO涂层热震40次后发生失效,其热导率明显低于SZO涂层,这主要与LSYZO陶瓷自身的复杂结构有关。     

纳米ZrO2-Y2O3-La2O3热障涂层的结构与性能研究

采用喷雾造粒工艺在纳米ZrO2-8wt％Y2O3(8YSZ)基体中添加了纳米La2O3,并进行团聚、热处理,作为喷涂喂料.NiCrAlY(Ni-25Cr-5Al-0.5Y,wt％)作为粘结层材料,采用等离子喷涂技术制备热障涂层.对涂层的组织结构和性能进行了表征与分析.结果表明:喷涂后涂层相组成只有稳定的t相;涂层具有典型的等离子喷涂结构;添加纳米LaO3能够降低涂层的热导率,且涂层的结合强度随掺杂量的增多而提高.     

等离子喷涂超高温热障涂层用纳米结构La2(Zr0.75Ce0.25)2O7球形喂料的研究

目的通过纳米粉体造粒技术制备出适合热喷涂超高温用纳米结构La2(Zr(0.75)Ce(0.25))2O7球形喂料,进而采用热喷涂方法制备出纳米结构的热障涂层,以满足下一代热障涂层服役温度需求。方法以化学共沉淀法合成的纳米La2(Zr(0.75)Ce(0.25))2O7粉末为原料,通过球磨、喷雾干燥及热处理工艺制备出纳米结构的La2(Zr(0.75)Ce(0.25))2O7喂料,进而采用大气等离子喷涂方法制备出纳米结构La2(Zr(0.75)Ce(0.25))2O7热障涂层。利用扫描电镜(SEM)和透射电镜(TEM)对原始纳米粉体、纳米喂料及喷涂态涂层进行显微形貌和组织结构分析。此外,通过电感耦合等离子体原子发射光谱法(ICP-AES)对制备的纳米喂料进行成分分析。结果制备出的纳米结构La2(Zr(0.75)Ce(0.25))2O7喂料表面光滑、呈球形,成分与化学计量比基本一致。相对于原始纳米粉末,喂料晶粒长大并不显著。喷涂态涂层部分晶粒长大,但仍保留纳米结构。结论成功制备出纳米结构La2(Zr(0.75)Ce(0.25))2O7球形喂料及纳米结构热障涂层,有望作为下一代超高温热障涂层材料。     

TC4钛合金表面等离子喷涂Al2O3-13wt%TiO2涂层及激光重熔研究

采用等离子喷涂技术在TC4钛合金表面制备了常规Metco130陶瓷涂层及纳米结构Al2O3-13wt%TiO2涂层,并利用CO2激光器对涂层进行了激光重熔,采用X射线衍射分析(XRD)、扫描电镜分析(SEM)、微区成分分析(EDAX)及维氏硬度试验研究了激光重熔前后涂层的组织性能变化.结果表明,等离子喷涂涂层与基体形成了较好的机械结合,但涂层中存在孔隙,激光重熔后,重熔层与基体形成了良好的冶金结合,其组织结构更为均匀而致密.采用谢乐公式估算了重熔后涂层中各相的平均粒径,结果表明,等离子喷涂纳米结构的涂层在激光重熔后仍然处于纳米结构.另外,选择合理的激光工艺参数,涂层的硬度得到了较大提高.     

纳米Al2O3改性三聚氰胺-脲醛自修复微胶囊的制备及应用

以纳米Al_2O_3改性三聚氰胺-脲醛树脂(MUF)为壁材,环氧树脂为芯材,采用原位聚合法合成了微胶囊,并采用光学显微镜(OM)、扫描电子显微镜(SEM)、红外光谱仪(FTIR)、X射线光电子能谱分析仪(XPS)、热重分析仪(TGA)等对其表面形貌、结构及热性能等进行了表征和测试;将改性后的微胶囊加入自修复环氧树脂涂层中,并对其热性能、力学性能、自修复性能及电化学性能进行测试。结果表明,当芯壁比为1.5:1、纳米Al_2O_3质量分数为4.5%时,纳米Al_2O_3在壁材中均匀分布,微胶囊的表面粗糙度和热稳定性均增加。当涂层中改性微胶囊质量分数为5%时,涂层的热稳定性提高,且涂层的拉伸强度、弯曲强度、冲击强度及粘结强度分别提高了111.9%、55.1%、10.6%和51.9%;制备的涂层具备较好的自修复性能;涂层的耐腐蚀性能随着微胶囊质量分数的增大而增强。     

等离子喷涂Gd_2Zr_2O_7-SrZrO_3复合陶瓷涂层的微观结构和性能

通过固相反应法合成了Gd_2Zr_2O_7-SrZrO_3 (GZSZ,Gd_2Zr_2O_7:SrZrO_3=7:3)复合陶瓷粉末,并采用喷雾造粒法和大气等离子喷涂法分别制备了适合等离子喷涂使用的相应喷涂粉末及涂层。使用X射线衍射、扫描电子显微镜对粉末和涂层的相组成、显微结构进行分析。借助激光热导仪、高温热膨胀仪对涂层的热扩散系数和热膨胀系数、烧结系数进行了表征。结果表明,制备的GZSZ复合陶瓷粉末和涂层都由Gd_2Zr_2O_7和SrZrO_3两相组成,粉末中的Gd_2Zr_2O_7为烧绿石结构,而涂层中的Gd_2Zr_2O_7为萤石结构,SrZrO_3都为钙钛矿结构。制备态GZSZ涂层的孔隙率为～14%。GZSZ涂层1400℃热处理5 h后的热膨胀系数为(9.8～11.2)×10~(-6) K~(-1)。制备态GZSZ涂层的热导率为～0.8 W·m~(-1)·K~(-1),与制备态SrZrO_3涂层的热导率～1.0 W·m~(-1)·K~(-1)相比降低～20%。1400℃热处理360 h后GZSZ涂层的热导率增加到～1.5 W·m~(-1).K~(-1)。综上表明,GZSZ涂层是一种很有前景的复合陶瓷热障涂层材料。     

等离子喷涂纳米氧化锆涂层的热震失效机理研究（英文）

采用合理的喷涂工艺参数制备了纳米氧化锆涂层并在1100℃下测试了其热震性能,利用X射线衍射(XRD),扫描电镜(SEM)和透射电镜(TEM)对涂层的结构及表面/界面形貌进行了分析。根据实验分析结果提出了纳米涂层的热震失效机理,即孔隙或早期存在的微裂纹由于能提供更好的生长空间而使得附近的纳米颗粒在热震实验过程中优先长大,其长大过程会造成新的微裂纹生成,从而导致其它的纳米颗粒长大。随着纳米结构涂层中的大多数或者全部的纳米颗粒长大后,纳米结构随之变为准微米结构,其热震失效模式将类似于传统微米涂层的失效方式。     

Study of microstructure and thermal shock behavior of two types of thermal barrier coatings

Gas turbines provide one of the most severe environments challenging material systems nowadays. Only an appropriate coating system can supply protection particularly for turbine blades. This study was made by comparison of properties of two different types of thermal barrier coatings (TBCs) in order to improve the surface characteristics of high temperature components. These TBCs consisted of a duplex TBC and a five layered functionally graded TBC. In duplex TBCs, 0.35 mm thick yittria partially stabilized zirconia top coat (YSZ) was deposited by air plasma spraying and ～0.15 mm thick NiCrAlY bond coat was deposited by high velocity oxyfuel spraying. ～0.5 mm thick functionally graded TBC was sprayed by varying the feeding ratio of YSZ/NiCrAlY powders. Both coatings were deposited on IN 738LC alloy as a substrate. Microstructural characterization was performed by SEM and optical microscopy whereas phase analysis and chemical composition changes of the coatings and oxides formed during the tests were studied by XRD and EDX. The performance of the coatings fabricated with the optimum processing conditions was evaluated as a function of intense thermal cycling test at 1100 °C. During thermal shock test, FGM coating failed after 150 and duplex coating failed after 85 cycles. The adhesion strength of the coatings to the substrate was also measured. Finally, it is found that FGM coating has a larger lifetime than the duplex TBC, especially with regard to the adhesion strength of the coatings.     

等离子喷涂和激光熔覆热障涂层隔热性能比较

采用多种方法制备不同类型的Al2O3-13％TiO2热障涂层,即等离子喷涂常规涂层、纳米结构涂层及激光熔覆纳米结构涂层．在分析三类涂层微观组织的基础上,对其隔热性能进行了比较．结果表明,即等离子喷涂常规陶瓷涂层呈典型的层状堆积特征,纳米结构涂层都为特殊的两相结构,其中部分熔化区由类似的残留纳米粒子组成,等离子喷涂纳米结构涂层的完全熔化区为片层状结构,而相应的激光熔覆涂层的完全熔化区则为细小等轴晶．在相同条件下,等离子喷涂纳米结构热障涂层具有最好的隔热性能,而激光熔覆纳米结构涂层的隔热性能要好于等离子喷涂常规涂层．     

Modeling thermal conductivity of thermal spray coatings: comparing predictions to experiments

Thermal conductivity plays a critical role in the thermal transport of thermal-sprayed coatings. In this article, a combined image analysis and finite-element method approach is developed to assess thermal conductivity from high-resolution scanning electron microscopy images of the coating microstructure. Images are analyzed with a collection of image-processing algorithms to reveal the microscopic coating morphology. The processed digital image is used to generate a two-dimensional finite-element mesh in which pores, cracks, and the bulk coating material are identified. The effective thermal conductivity is then simulated using a commercial finite-element code. Results are presented for three coating material systems [yttriastabilized zirconia (YSZ), molybdenum, and NiAl], and the results are found to be in good agreement with the experimental values obtained using the laser flash method. The YSZ coatings are also annealed, and the analysis procedure was repeated to determine whether the technique can accurately assess changes in coating morphology. This article was originally published inBuilding on 100 Years of Success: Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials Park, 2006.     

The effects of ceria on the mechanical properties and thermal shock resistance of thermal sprayed NiAl intermetallic coatings

The effects of ceria addition to thermal sprayed NiAl intermetallic coatings were investigated through micro-indentation, thermal shock testing and microstructural analysis techniques (scanning electron microscopy with energy-dispersive X-ray spectrometry and X-ray diffraction analysis). It has been found that the addition of CeO₂ to NiAl coatings reduces the tendency of brittle peeling during thermal spraying. This reduction in peeling is presumably due to the improved wetting of the substrate by the molten coating material, which leads to better coating adhesion. The addition of CeO₂ resulted in higher coating hardness and elastic modulus. The coatings containing CeO₂ also exhibited significant increases in thermal shock resistance compared with that of the pure NiAl coating. The NiAl coating containing 2 wt.%CeO₂ had the highest hardness, elastic modulus and thermal shock resistance of the four NiAl-based coatings tested. The possible mechanisms responsible for the improvement of the properties upon addition of CeO₂ are addressed.     

激光表面重熔对ZrO_2-8wt%Y_2O_3热障涂层组织与抗热震性能的影响

采用等离子喷涂设备在H13热作模具钢表面制备氧化钇部分稳定的氧化锆(ZrO2-8 wt%Y2O3)热障涂层,并用CO2横流激光器对热障涂层进行表面重熔处理,并采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、热震试验等手段研究激光重熔前后热障涂层的微观结构及其抗热震性能的变化。结果表明,重熔前后涂层均由四方结构钇锆氧化物和立方相的氧化锆组成,重熔后涂层结晶度增加,晶粒有长大现象。激光重熔后涂层产生明显分层,表层组织孔隙和裂纹明显减少,裂纹呈网状且沿晶界分布,重熔涂层内部仍保持等离子喷涂典型结构。激光重熔后涂层孔隙率降低了67%,涂层的抗热震性能也显著提高。     

激光重熔对等离子喷涂热障涂层冲蚀行为影响

研究了等离子喷涂和激光重熔ZrO<,2>-7%Y<,2>O<,3>热障涂层的微观结构,同时考察了两种涂层的抗冲蚀性能,并探讨了其冲蚀破坏机理.试验发现,等离子喷涂热障陶瓷涂层呈典型的层状堆积特征;经过激光重熔处理后,涂层表面形成了沿热流方向生长的柱状品重熔区;相对于等离子喷涂试样,激光重熔涂层有较好的抗冲蚀性能;不管等...     

Characterization of modified thick thermal barrier coatings

In gas turbines and diesel engines, there is a demand for thick thermal barrier coatings (TTBCs) due to the increased process combustion temperatures. Unfortunately, the increased thickness of plasma-sprayed thermal barrier coatings (TBCs) normally leads to a reduced coating lifetime. For that reason, the coating structures have to be modified. When modifying the structure of TTBCs, the focus is normally on elastic modulus reduction of the thick coating to improve the coating strain tolerance. On the other hand, coating structural modification procedures, such as sealing treatments, can be performed when increased hot-corrosion resistance or better mechanical properties are needed. In this article, several modified zirconia-based TTBC structures with specific microstructural properties are discussed. Coating surface sealing procedures such as phosphate sealing, laser glazing, and sol-gel impregnation were studied as potential methods for increasing the hot-corrosion and erosion resistance of TTBCs. Some microstructural modifications also were made by introducing segmentation cracks into the coating structures by laser glazing and by using special spraying parameters. These last two methods were studied to increase the strain tolerance of TTBCs. The coating microstructures were characterized by optical microscopy, a scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD). The effect of sealing procedures on the basic thermal and mechanical properties of the coatings was studied. In addition, some correlations between the coating properties and microstructures are also presented, and the advantages and drawbacks of each modification procedure are discussed.     

合金钢热障涂层等离子喷涂及高温力学特性研究

目的研究等离子喷涂热障涂层微观组织与高温力学性能,为热障涂层在合金钢的应用及其失效机制提供理论支撑。方法采用等离子喷涂技术在30Cr Mn Si A钢基体上制备Ni Co Cr Al Y/YSZ热障涂层,利用扫描电镜显微观察、物相分析、热震试验、拉伸试验等技术方法,考察涂层在高温条件下的失效行为。结果合金钢等离子喷涂热障涂层为典型双层层片状结构,YSZ涂层仅含有稳定四方相。800℃时,涂层试样拉伸试验后的断裂载荷与无涂层试样相比高10%。热障涂层的抗热震性良好,经900℃热震循环试验10次后,涂层完好;经1000℃热震循环6次后,涂层剥落失效,剥落面位于粘结层与基体之间。热震循环过程中,钢基体被氧化甚至腐蚀。涂层试样边缘产生应力集中,随着热震次数的增加,裂纹逐渐扩展,最终导致涂层成块剥落。温度由700℃升至900℃,Ni Co Cr Al Y涂层硬度下降幅度大于YSZ涂层和30Cr Mn Si基体。结论粘结层与钢合金基体的热膨胀不匹配是导致热震试验涂层剥落的主要原因。热障涂层的隔热作用使涂层试样的基体温度较低,导致其断裂载荷与无涂层试样相比较高。     

Preparation of cross sections of thermal spray coatings for TEM investigation

A technique for the preparation of cross sections for transmission electron microscopy (TEM) of thermal spray coatings has been developed. The procedure is designed to minimize specimen damage during mechanical thinning and to reduce the effect of differential thinning during ion milling. Specimens were made by two different coating systems— WC- Co coating produced by the FARE Gun process on a mild steel substrate and Tribaloy T- 800 sprayed by the HVOF process on a nickel- base superalloy. These specimens have large areas that are electron transparent on either side of the interface, and the results have shown the atomic scale microstructure of the interface between the thermal spray coating and the substrate.     

NiCoCrAlY粘结层喷涂工艺对8YSZ热障涂层抗氧化性能的影响

目的 提高热障涂层粘结层的抗高温氧化性能。方法 分别采用爆炸喷涂和等离子喷涂工艺制备了不同结构的NiCoCrAlY粘结层,之后通过等离子喷涂制备8YSZ陶瓷层,分析了两种粘结层结构的热障涂层的抗高温氧化性能。利用XRD、SEM和EDS对涂层物相、微观结构和成分进行分析,并对其与基体结合状态、抗高温氧化性能进行研究。结果 爆炸喷涂粘结层内部组织致密,缺陷较少,与基体结合处孔隙少;而等离子喷涂粘结层内部的层状特征明显,孔隙较多,表面粗糙度较低。爆炸喷涂粘结层氧化5 h后,表面生成了一层富Al2O3的致密氧化物膜;而等离子喷涂粘结层表面形成了富NiO、CoO、Cr2O3和Ni(Cr,Al)2O4的氧化物层,并出现了许多微裂纹和片层状氧化物。爆炸喷涂制备的热障涂层试样在前5 h氧化增重速率高于等离子喷涂试样,随后变平缓,而等离子喷涂试样氧化速率依然较高。爆炸喷涂热障涂层的热生长氧化物层（Thermally grown oxide, TGO）经50 h氧化后,仍呈连续状,厚度均匀,粘结层内氧化物缺陷较少。结论 爆炸喷涂粘结层组织均匀、致密,喷涂时涂层的氧化以及热处理的内氧化较少,使得足够的Al较快速地在粘结层表面形成致密的氧化铝,表面一定厚度的氧化铝层抑制了氧和其他金属原子的相向扩散反应,提高了涂层的抗高温氧化性能。