SiC涂层对高温气冷堆用石墨摩擦磨损性能的影响

利用MM-200磨损试验机对高温气冷堆反射层用石墨（IG11）及HTR-10高温气冷堆燃料元件基体石墨（MG）的摩擦磨损性能进行了研究。结果发现,摩擦系数随载荷增加而逐渐减小,两种石墨的摩擦系数基本相同。石墨的磨损速率随载荷增加而增大,石墨IG11的耐磨性优于MG的。利用气相反应扩散法在石墨基体上涂覆SiC涂层后可以明显改善其耐磨性,且随着涂覆温度的升高改善效果更为明显;低温涂覆SiC涂层后IG11的耐磨性优于MG的,高温涂覆SiC涂层后MG的耐磨性优于IG11的。     

SiC/SiO2抗氧化涂层的热稳定性分析

改善高温气冷用石墨抗氧化性能对高温气冷堆安全性具有重要意义.本文利用HSC-CHEMISTRY 4.1计算软件分析了SiC涂层、SiO2涂层和SiC/SiO2复合涂层在高温气冷堆正常服役条件和事故条件下的热稳定性,并用氧化试验对热稳定性和抗氧化性能进行了研究.结果表明,SiC/SiO2复合涂层在高温气冷堆正常服役条件和事故条件均能保持长期稳定.在纯氦气及氦气-空气混合气体氧化条件下,SiC/SiO2复合涂层均具有很好的热稳定性,并且能显著改善高温气冷堆用石墨的抗氧化性能.     

高温气冷堆包覆燃料颗粒ZrC涂层的研究进展

高温气冷堆包覆燃料颗粒关键涂层为SiC涂层,随着高温气冷堆提升功率和向超高温气冷堆发展的趋势,SiC涂层已不能满足包覆燃料颗粒性能要求.ZrC材料具有优良的组织和性能,作为一种最具潜力的包覆颗粒涂层材料,其研究和应用逐渐得到重视和发展.本文介绍了高温气冷堆包覆燃料颗粒ZrC涂层的研究背景、晶体性质、制备方法、组织结构和性能特征.指出了ZrC涂层研究中的现存问题,并预言了进一步的发展趋势.     

石墨抗氧化SiC涂层的制备与性能研究

本文以SiC、Si和酚醛树脂为主要原料,通过浸涂和气相渗硅两步法在石墨表面制备了SiC抗氧化涂层。利用XRD、SEM研究了涂层的相组成与形貌。结果表明,气相渗硅后涂层的主相为α-SiC,β-SiC和Si,其中Si是气相渗硅过程中残留的。涂层与基体之间具有过渡结构,致密度良好。抗氧化和抗热震实验表明：由气相渗硅工艺制备的SiC涂层结构致密,具有良好的抗氧化性能,1200℃空气条件下氧化16 h后试样每小时增重量约为2.18 mg/cm₂。涂层具有良好的抗热震性能,经1000 ℃—室温循环热震15次后试样质量变化百分率仅为-0.17%。     

Cf/SiC复合材料SiC/Yb2SiO5抗氧化复合涂层研究

硅酸镱(Yb2SiO5)是Cf/SiC复合材料非常理想的抗氧化涂层材料.用脉冲CVD法在Cf/SiC复合材料上先制备SiC粘附层.用溶胶凝胶法制备粒径为200~300 nm的单相Yb2SiO5粉体,然后用PCS-SiC-Yb2SiO5浆料浸涂法制备SiC-Yb2SiO5过渡层,因PCS粘结强度大,且热解后能在原位生成SiC,故能大大增加涂层的结合力.配备低粘度、高固含量的Yb2SiO5浆料,并用浆料浸涂烧结法制备致密、细晶粒的Yb2SiO5涂层.1500 ℃静态空气中氧化实验表明:SiC/Yb2SiO5复合涂层具备优异的抗氧化性能.     

炭/炭复合材料表面SiC/ZrSiO4-SiO2复合涂层的抗氧化性能与红外发射特性研究

为提高炭/炭(C/C)复合材料的高温抗氧化性能并降低其红外发射率,采用包埋–刷涂法在其表面制备了SiC/ZrSiO_4-SiO_2复合涂层。借助XRD、SEM等表征分析了涂层的成分与微观结构,并研究了SiC/ZrSiO_4-SiO_2复合涂层包覆C/C复合材料在1500℃动态空气条件下的抗氧化性能,以及在90和500℃下的红外发射率。结果表明:由疏松结构SiC内涂层和镶嵌结构ZrSiO_4-SiO_2外涂层组成的SiC/ZrSiO_4-SiO_2复合涂层具有优异的抗氧化性能,在1500℃流动空气(0.6 L/min)等温氧化条件下氧化50 h后试样的氧化失重率仅为0.03%。在C/C复合材料表面制备SiC/ZrSiO_4-SiO_2复合涂层后其红外发射率明显降低,并随温度升高而越低。复合涂层包覆试样在90℃时3~5μm和8~14μm波段的平均红外发射率分别为0.55和0.66;在500℃时3~5μm和8~14μm波段的平均红外发射率分别为0.48和0.62。SiC/ZrSiO_4-SiO_2复合涂层包覆C/C复合材料可作为优良的低红外发射率高温热结构材料应用于航空航天领域。     

MoSi2涂层高温抗氧化性能研究进展

综述了MoSi2作为C/C复合材料和难熔金属的高温抗氧化涂层的氧化性能的研究进展,比较研究了MoSi2高温抗氧化涂层的制备工艺,提出了MoSi2涂层技术的未来发展方向,即研发高温长寿命高可靠性抗氧化涂层、超高温抗氧化涂层,以满足航空发动机及航天飞机在恶劣工况条件下的使用要求.     

C／C复合材料防氧化涂层SiC／SiC—MoSi2的制备与抗氧化性能

采用包埋法和涂刷法在C/C复合材料表面依次制备了SiC内涂层和SiC-MoSi2外涂层,借助XRD与SEM对涂层的微观结构进行了分析,研究了涂覆后的C/C复合材料在高温静态空气中的防氧化性能.结果表明:SiC/SiC-MoSi2复合涂层有效缓解了MoSi2与C/C热膨胀不匹配问题,涂层无裂纹;复合涂层在900和1500℃静态空气环境下均可对C/C复合材料有效保护100 h以上;涂层的多层、多相结构以及在高温氧化后表面生成的SiO2薄膜是其具有优异防氧化性能的原因.     

TaSi2改性ZrB2/SiC复合粉末制备及涂层抗氧化性能研究

目的 提高ZrB2/SiC涂层的致密性及抗氧化烧蚀能力。方法 设计向ZrB2/SiC涂层中掺杂TaSi2,以提升ZrB2/SiC涂层的致密度和抗氧化性能。首先通过喷雾造粒法制备了4种不同成分配比的复合团聚粉,然后采用大气等离子喷涂(APS)在C/C基体表面制备了4种团聚粉复合涂层,最后使用氧-乙炔火焰法对所制备的涂层进行了烧蚀考核。结果 通过涂层致密度对比发现,随着TaSi2的增加,涂层共晶区会有所增加,涂层致密度得到了明显改善。通过烧蚀考核发现,TaSi2的加入能够增加SiO2的含量,并产生热稳定性好的TaZr2.75O8。此外致密TaZr2.75O8的产生还能够有效改善涂层的抗氧化烧蚀性能。结论 最终得出的ZrB2/SiC涂层硅化物掺杂改性方案为30%TaSi2/42%ZrB2/28%SiC(体积分数)大气等离子喷涂制备的抗氧化烧蚀涂层,其在1 600 ℃烧蚀5 min后的质量损失率为‒1.70×10^‒4 g/s。     

钽合金高温抗氧化复合涂层制备研究

目的 制备钽合金在高温氧化环境下的防护涂层。 方法 采用料浆熔烧法,在 Ta-12W 合金表面依次制备底层和面层,通过两次熔烧处理,获得硅化物复合涂层。 分析涂层的形貌、元素含量及成分分布,测试涂层在 1800 ℃ 下的高温抗氧化性能和室温 ~ 1800 ℃ 热循环寿命, 并初步探讨涂层失效机理。结果 制备的复合涂层与基体之间通过扩散形成过渡层,达到冶金结合;涂层在 1800 ℃ 下可连续工作 9h,室温 ~ 1800 ℃ 热循环寿命为 151 次。 结论 在高温氧化环境中,复合涂层表面生成了一层玻璃状薄膜,有效阻止了外界氧向基体的进一步扩散,对基体形成了良好的保护。     

Protective coatings for very high temperature reactor applications

The future very high temperature reactors (VHTR) are nuclear systems that shall operate at a maximum temperature of about 950 °C. Primary circuit materials thus require good creep and corrosion resistance on very long time. Use of high‐strength alloys with protective coatings could significantly improve the service life of high temperature reactor components. However, coating systems are mainly designed for shorter term purposes, often under extremely aggressive atmospheres, that cannot be extrapolated to the VHTR environment. We present our first investigations on the environmental resistance of Alloy 800H coated with two different protective systems under VHTR representative conditions: NiAl(Pt)/EBPVD ZrO₂(Y) and NiCrAl(Y)/CVD ZrO₂(Y). Isothermal exposures were carried out up to 1000 h at 950 °C in impure helium. This specific atmosphere was shown to induce formation of a surface oxide scale together with carburisation of the bare Alloy 800H. After high temperature exposure to impure helium, the microstructure of the coated specimens has changed due to both thermal ageing and corrosion. Performances of the two coating systems are compared regarding the VHTR application.     

Stress analysis of high temperature ZrO2 insulation coatings on Ag using finite element method

The aim of this study is to investigate residual stresses occurred during cooling procedure of ZrO₂ insulation coating on Ag substrate for magnet technologies. ZrO₂ coatings were produced on Ag tape substrate by using a reel-to-reel sol–gel technique. SEM inspection showed that ZrO₂ coatings had mosaic structures. ANSYS finite element software was used to calculate the temperature and stress distribution of the ZrO₂/Ag structure. The effect of coating thickness on residual stresses was also examined. The results obtained showed that thermal stresses in ZrO₂ coating and Ag substrate were considerably affected by the cooling time and coating thickness. It is concluded the thermal stresses increase with increase of film thickness.     

Al含量及SiC预处理对SiCp/Ti基复合材料高温抗氧化性能的影响

通过800℃氧化试验,研究了不同Al含量以及SiC经600℃×3 h预处理后,SiCp/Ti基复合材料的氧化行为.利用SEM、EDS以及XRD分析了表面氧化层的形貌以及相组成.结果表明,未加Al复合材料氧化层的氧化产物主要为金红石TiO2,添加Al的材料中有少量Al2O3;对于SiC颗粒增强的Ti基复合材料,未加Al的抗氧化性能最好;当比较所有含Al的复合材料时,随着Al含量的增加,抗氧化性增强;对于具有相同Al含量的材料,SiC预处理可以促使界面较好结合,故可提高材料的抗氧化性.     

Cr与B对镍基高温钎料在Cf/SiC陶瓷基复合材料上润湿性的影响

研究了Cr和B元素对镍基高温钎料在3D-Cf/SiC陶瓷基复合材料上的润湿性的影响.试验结果发现,在真空度小于10-3 Pa,工作温度1100 ℃,保温时间10 min条件下,当钎料中的Cr元素含量为15%,B元素含量为0.6%时,镍基钎料在Cf/SiC上的润湿角为10°,然而B元素含量增加到2.4%后,润湿角增大到62°,表明钎料中的元素B降低钎料在Cf/SiC上的润湿性.钎料中的活性元素Cr对润湿有重要影响.镍基钎料在Cf/SiC上的润湿过程属于反应润湿,润湿界面生成多种碳化物和硅化物.采用扫描电镜与能谱仪分析界面的微观结构与成分,通过X射线衍射仪检测界面产物.     

石墨表面化学气相沉积SiC及C涂层的制备

以C3H8和CH3SiCl3（MTS）为先驱体原料,用化学气相沉积法在石墨基体表面分别制备了C涂层、SiC涂层。采用X射线衍射仪和扫描电镜分析了两种涂层的成分和表面微观形貌,研究了温度和气体流量对涂层微观形貌的影响。结果表明,当C3H8＋N2流量为140 L/h,沉积温度为1300℃时,石墨基体表面可获得致密度较高的C涂层,而且涂层比较平整、均匀,而流量为160 L/h时涂层比较粗糙。当MTS＋H2流量为60 L/h、沉积温度1100℃时在石墨基体表面可以形成致密的SiC涂层,1300℃时生长的SiC晶体形貌发生改变,涂层厚度增加,表面有较多圆形凸起。当MTS-H2气体流量增大可使SiC涂层晶粒尺寸增大,但大流量易产生涂层剥落。采用C和SiC共沉积涂层作过渡层,涂层与石墨基体界面结合增强;SiC涂层与石墨基体之间存在厚度较大的过渡区域,过渡区域平均厚度约2μm。     

The performances of TiB2-contained iron-based coatings at high temperature

The TiB₂-contained composite Fe-B-C coatings are deposited by the plasma transferred-arc (PTA) powder surfacing process. The coating's thermal ability, arc ablation resistance and wear resistance at high temperature were analyzed. It is concluded that TiB₂-contained composite Fe-B-C coating having excellent wear resistance at 600 °C and tempering resistance at 900 °C. Furthermore, this coating can effectively resist the arc ablation (120 A arc currents) within 7 s.     

HfB2/SiC as a protective coating for 2D Cf/SiC composites: Effect of high temperature oxidation on mechanical properties

In the field of thermal shielding for aerospace applications C_f/SiC composites are raising great interest, provided that they are protected from oxidation by suitable coatings. Conversely, ultra high temperature ceramics, and in particular HfB₂, are among the best oxidation resistant materials known. A coating made of a HfB₂/SiC composite (20% weight SiC) was tested as an oxidation protection on a C_f/SiC composite. The composite was produced by Polymer Impregnation Pyrolysis (PIP), which is a simple and low cost method; the coating was applied by painting a slurry on the surface of the composite and by heat treating. The thermal behaviour was studied by thermo-gravimetric analysis, and mechanical tests were conducted before and after oxidation. The HfB₂/SiC composite seems to effectively protect the underlying C_f/SiC composite, with a mechanical strength reduction of only 20% after 30 min at 1600 °C, even if some weight loss due to partial carbon fibre damage is observed. A first analysis of thermal cycling in oxidizing environment suggested that the HfB₂/SiC coating reduces continual damage thanks to the sealing effect of the glassy surface layer.