NiCoCrAIY和NiCr粘接层抗热震性能的对比

为了提高GH907合金的抗高温和抗热腐蚀性能,利用低压等离子喷涂技术在其表面制备了NiCoCrAlY 粘接层和NiCr粘接层,并对2种粘接层的抗热震性能进行了研究.结果表明,NiCoCrAIY粘接层和NiCr粘接层经过10次热震后,表面都有裂纹产生,且NiCoCrAlY粘接层的裂纹较NiCr粘接层的粗大;在横截面上NiCr粘接层只有沿喷涂颗粒断裂的垂直裂纹,而NiCoCrAlY粘接层不仅有垂直裂纹,还存在沿界面扩展的横向裂纹;NiCr粘接层的抗热震性能相比NiCoCrAlY粘接层的更好一些.     

石墨高温粘接部件的抗热震性能研究

以酚醛树脂（Phenol-Formaldehyde Resin,PF)和B4C、SiO2为原料制备了高温粘结剂，并对石墨材料进行高温粘接，同时考察了粘接石墨制品经历ΔT=800℃和ΔT＝1000℃温度交变后的抗热震性能。结果表明，用该粘结剂粘接的石墨样品有着优良的抗热震性能，经历数次热震后其强度保持率仍然较高。此外，还对影响粘接样品抗热震性能的因素进行了理论探讨，指出优化原料性质、提高热处理温度、控制胶层厚度等对提高抗热震性能有重要的影响。     

环氧树脂钢铅钢粘接工艺优化程度评价方法

为了改善环氧树脂钢-铅-钢粘接件的粘接可靠性,提高粘接性能,采取一套比较全面的综合评判方法,从粘接强度及其离散性、粘接的胶层粘附率、粘接断面的微观形貌及其表面分析五个角度的综合分析、评价钢-铅-钢环氧树脂粘接件的粘接工艺的优化程度.通过对粘接面的表面处理来改进粘接工艺,将试样的平均粘接强度从原来的4.2 MPa提高到10.9 MPa,同时强度离散性参数从19%下降到3.3%,总体胶层粘附率参数从50%提高到76%～97%,微观形貌下表面粗糙度有所改善,表面分析表明铅合金与环氧树脂胶层结合较为紧密.综合评判方法验证了改进后的粘接工艺具有较高的优化程度,该评价方法对评价粘接工艺是否优化具有较好的效果.     

Ti2AlNb合金表面射频溅射Al/Al2O3复合层的抗热震性能

为进一步提高Ti₂AlNb合金的抗高温氧化性能,在其表面射频溅射Al/Al₂O₃复合层,并于650℃下进行了抗热震性能研究,采用扫描电镜及能谱仪观察复合层形貌并分析其成分。结果表明:Al/Al₂O₃复合层平整致密,无贯穿裂纹,复合层中Al₂O₃层厚约1μm,Al层厚约14μm;热震循环50次时复合层表面出现了微小裂纹,随着热震循环次数增加,裂纹不断扩展,表层Al₂O₃颗粒增大;Al/Al₂O₃复合层能有效提高Ti₂AlNb合金的抗热震性能。     

固体推进剂装药领域丁羟衬层研究进展

丁羟衬层是一种壳体粘接式固体火箭发动机装药常用的粘接材料,主要作用是实现固体推进剂与绝热层的可靠粘接,保证推进剂按照设计规律进行燃烧,保证发动机的正常工作。主要介绍了壳体粘接式固体火箭发动机装药领域丁羟衬层力学性能、装药粘接性能、老化性能及成型工艺方面的研究进展,并对今后丁羟衬层的研究方向提出了展望。     

飞机炭刹车盘粘接修复技术研究

探讨了适用于Ｃ／Ｃ复合材料粘接的新方法、新工艺,对Ｃ／Ｃ复合材料粘接试样进行了常温性能、抗热冲击性能的测试,采用ＳＥＭ对粘接界面和破坏断面进行了观察和分析。同时,进行了粘接法修复的Ｂ７５７－２００飞机炭盘地面动力模拟试验。说明了 妆修复是一种有效的修复方法。     

铝合金裂纹板的阳极化处理与复合材料补片胶接修理效果

采用磷酸阳极化方法对胶接修理铝合金裂纹板的粘接表面进行了处理,并用单向碳纤维/环氧复合材料补片对铝合金进行了修补.测试了阳极化铝合金的粘接性能、修补结构的静态力学性能和疲劳性能,考察了粘接表面的阳极化处理对修补结构的静态力学性能和疲劳性能的影响.结果表明,磷酸阳极化在铝合金表面形成多孔膜,复合材料补片修补胶接时胶粘剂能渗透进入阳极化铝合金表面的多孔膜,在粘接界面上形成一层过渡层,该过渡层的形成能有效提高其与复合材料的粘接性能,其粘接副的拉剪强度提高了104%;铝合金裂纹板胶接修理前的粘接表面的阳极化处理能大幅度地提高修复结构的静态强度和疲劳寿命,当用单向碳纤维/环氧复合材料补片单面修补时,修补结构的破坏强度为418.13MPa,恢复到完好板的93.42%;修补结构的疲劳寿命相对裂纹板延长了1.42倍,比未阳极化的修补板的疲劳寿命增加了27.59%.修补前的阳极化处理也使修补结构在一定周次疲劳后的剩余强度有所提高.     

低能离子束表面改性对聚碳酸酯(PC)粘接性能的影响

利用氩氧混合低能离子束对双酚A型聚碳酸酯(PC)透明材料进行表面改性,并用自制丙烯酸酯胶黏剂表征了改性前后的粘接性能.结果表明:改性后的PC与丙烯酸酯胶黏剂的压剪强度得到了明显的改善.经分析,粘接性能的改善是由于低能离子束表面改性后的PC表面润湿性能的改善、表面活性的提高、表面弱电层的剥蚀和表面微交联层的生成引起的.     

石墨高温粘接界面的组成及其与粘接强度间的关系

以酚醛树脂和碳化硼为原料制备了性能良好的调温粘结剂并对石墨材料进行粘接。通过XPS的测试，研究了石墨调温粘接样品在不同的温度热处理后的界面组成，相对含量变化及其与粘接性能间的相关性。结果表明，粘接界面上主要存在着C，B，O等元素，其中，酚醛树脂（PF）炭化产生的无定形炭构成了胶层骨架，其相对含量的变化影响着胶层结构的致密稳定性；B在粘接样品中以B4C或B2O3形式存在，其存在形式对粘接强度有着重要的影响。     

金属Ni修饰的石墨烯及其对等离子喷涂NiCoCrAlY涂层力学性能的影响

为了解决石墨烯(GNPs)易团聚、高温易烧损等问题,本研究将利用化学镀工艺对石墨烯进行表面金属Ni修饰(Ni@GNPs),并通过等离子喷涂技术在K465高温合金表面制备NiCoCrAlY、NiCoCrAlY+GNPs和NiCoCrAlY+Ni@GNPs三种涂层,重点探究超声辅助、化学镀反应温度以及反应时间等因素对石墨烯表面修饰的影响,研究了Ni@GNPs外来添加相对等离子喷涂NiCoCrAlY涂层组织结构与力学性能的影响.结果表明,经过化学镀处理,石墨烯表面沉积了均匀分布的金属Ni镀层,在50℃下辅助超声反应40 min可进一步提高石墨烯表面的修饰效果;与NiCoCrAlY和NiCoCrAlY+GNPs涂层相比,添加Ni@GNPs能够显著减少涂层的孔洞与裂纹数量、提高涂层的致密性、大幅降低涂层的孔隙率;与NiCoCrAlY相比,NiCoCrAlY+Ni@GNPs涂层的硬度提升了30.9％,冲蚀率下降了7.4％,说明添加相Ni@GNPs能提高NiCoCrAlY涂层的力学性能与抗冲蚀性能.     

等离子喷涂ZrO2热障涂层的抗热震性能

为了进一步了解等离子喷涂ZrO2涂层的制备及失效控制措施,提高涂层的使用寿命,研究了涂层在水淬和火焰喷烧两种条件下的抗热震性能.结果表明:水淬条件下垂直裂纹主要分布在距涂层中心12mm范围内,随热震次数的增加,垂直裂纹最终进入次表层,靠近中心处裂纹扩展较快;火焰喷烧条件下垂直裂纹分布在距涂层中心10 mm范围内,随热震次数的增加,裂纹在表面层和次表层界面处发生偏转,中心处裂纹扩展较快;火焰喷烧条件下涂层的抗热震性能优于水淬下,涂层中孔隙的存在加速了两种条件下裂纹的扩展.     

Effect of the composition profile and density of LPPS sprayed functionally graded coating on the thermal shock resistance

Low Pressure Plasma Spraying (LPPS) is a promising coating method for Functionally Graded Material (FGM) expected to beable to reduce the thermal stress in high temperature environments such as a gas turbine. In this paper, we report the effect of the composition profile and coating density of LPPS sprayed FGM, consisting of ZrO₂–8 wt%Y₂O₃ (YSZ) top coating, YSZ–Ni–20 wt%Cr (NiCr) FGM coating, NiCr under coating and copper substrate, on the thermal shock resistance evaluated by a modified temperature difference test. The density of YSZ and NiCr coating was successfully controlled by the chamber pressure and initial particle size in the range from 5.43 to 5.79 g/cm³ and from 7.89 to 8.09 g/cm³, respectively. For an YSZ composition profile from NiCr under coating to YSZ top coating (in FGM), the highest thermal shock resistance was obtained when the fraction of YSZ increased with gentleslope just over NiCr coating and acute slope just under YSZ coating. Also, the higher density coatings tended to perform the higher thermal shock resistance. Initial cracks formed in the YSZ top coating propagated into YSZ parts in FGM coating through the grain boundary of YSZ and/or the interface between flattened NiCr and YSZ particles. After the cracks connected, the coupled cracks caused the coating spallation.

©2003 Elsevier Science Ltd. All rights reserved.     

Effect of the composition profile and density of LPPS sprayed functionally graded coating on the thermal shock resistance

Low Pressure Plasma Spraying (LPPS) is a promising coating method for Functionally Graded Material (FGM) expected to be able to reduce the thermal stress in high temperature environments such as a gas turbine. In this paper, we report the effect of the composition profile and coating density of LPPS sprayed FGM, consisting of ZrO₂–8 wt%Y₂O₃ (YSZ) top coating, YSZ–Ni–20 wt%Cr (NiCr) FGM coating, NiCr under coating and copper substrate, on the thermal shock resistance evaluated by a modified temperature difference test. The density of YSZ and NiCr coating was successfully controlled by the chamber pressure and initial particle size in the range from 5.43 to 5.79 g/cm³ and from 7.89 to 8.09 g/cm³, respectively. For an YSZ composition profile from NiCr under coating to YSZ top coating (in FGM), the highest thermal shock resistance was obtained when the fraction of YSZ increased with gentle slope just over NiCr coating and acute slope just under YSZ coating. Also, the higher density coatings tended to perform the higher thermal shock resistance. Initial cracks formed in the YSZ top coating propagated into YSZ parts in FGM coating through the grain boundary of YSZ and/or the interface between flattened NiCr and YSZ particles. After the cracks connected, the coupled cracks caused the coating spallation.     

Characteristics of Plasma-Sprayed Ceramic Coatings and Their Engineering Application

The microstructure, porosity, microhardness and adhesive strength of three plasma- sprayed ceramic coatings (Al2 O3, Cr2 O3 and Cr3 C2 NiCr) were tested. The wear resistance of the coatings was characterized through sand blasting test. The results showed that the erosion resistance of Cr2 O3 coating was better than Al2 O3 and Cr3 C2 NiCr coatings'.Through depositing the coating on the surface of boiler overheater tubes and on the surface of baffle- wall of carrying- coal grain blower to test its anti- erosion performance after a period of running, it was confirmed that the coatings present excellent wear resistance. Accordingly, it also demonstrates that ceramic coating has a promising prospects in surface protection in thermal power stations.     

圆柱基体热障涂层热冲击下失效的瞬态应力分析

用等离子喷涂方法在合金圆柱体上制备了热障涂层,并用水冷的方法进行了热冲击实验,试样的失效现象为轴向的开裂和剥落.利用有限元分析工具对热障涂层的热冲击进行模拟,通过对涂层内部应力随时间分布的分析发现:热冲击过程中陶瓷层表面的周向应力随着时间由拉转变为压,冷却初期陶瓷层的周向拉应力值较大,超过了陶瓷层的抗拉强度,因而淬冷初期的周向应力是导致轴向裂纹萌发的主要原因;陶瓷层与粘结层接触面上的径向拉应力与粘结层的氧化生长引起界面开裂;轴向裂纹和界面开裂共同导致陶瓷层的剥落.     

Using ESPI system to measure high temperature fatigue deformation of ceramics thermally sprayed SUS304 steel

The strains in an Al₂O₃/NiCr coating, which was thermally sprayed on SUS304 steel, were analyzed using an electronic speckle pattern interferometry (ESPI) system during fatigue testing (R = 0, _max = 173 MPa) at high temperature of 873 K. The strain changes with the crack initiation in the coatings and the delamination at the coating/substrate interface are accordingly discussed.Surface cracks originated from the top coating of Al₂O₃ and stopped at the bond coating of NiCr after 2 cycles test at 873 K. Many surface cracks and delamination along the NiCr/substrate interface were confirmed after 1 × 10⁵ cycles test. The strain values of un-sprayed specimens obtained from the ESPI system agreed with those measured by the strain gauge when tensile stresses were applied at room temperature. The deformation by thermal expansion and stress application at high temperatures can also be easily measured using this method. The strain on sprayed specimens was almost the same with that on un-sprayed specimens at 873 K, indicating the deformation in the coatings are always associated with that of the substrate surfaces at high temperature. By comparing and analyzing the strain distribution on the coating surface, the presence of cracks in the coatings and delamination at the coating/substrate interface can be in-situ and nondestructively detected.     

等离子喷涂ZrO2-N iCoCrAlY 梯度涂层的成分分布与力学性能

在ZrO₂-NiCoCrAlY 梯度涂层中, 由基体到涂层表面, ZrO₂ 的含量逐渐增多,NiCoCrAlY 的含量逐渐减少,形成一种无宏观结合界面的成分连续变化的组织结构。随ZrO₂ 组元含量的升高, ZrO₂-NiCoCrAlY 复合涂层的密度基本呈线性降低; 涂层硬度则先降低后升高, 含60 vo l%ZrO₂ 的复合涂层具有最低的硬度值; 富含NiCoCrAlY 组元的复合涂层的孔隙率略低。与双层涂层相比, 成分梯度化的分布使梯度涂层的内聚强度和涂层与基体的结合强度都得到了明显地提高; 涂层与基体的结合界面是梯度涂层2基体体系中的最薄弱之处。     

Cyclic oxidation behavior of glass-ceramic composite coatings on superalloy K38G at 1100 °C

The SiO₂-Al₂O₃-ZrO₂-CaO-ZnO glass-ceramic composite coatings (GC), nanocrystalline NiCoCrAlY coating, and their combinations (bi-layer GC/NiCoCrAlY) were prepared on K38G specimens. The thicknesses of the glass-ceramic coatings and the NiCoCrAlY coatings were about 10 μm and 20 μm, respectively. Cyclic oxidation tests were carried out at 1100 °C for 120 cycles. Microstructures of the specimens before and after oxidation tests were characterized by SEM, EDS and XRD. The glass-ceramic coatings with or without a NiCoCrAlY intermediate layer improved the isothermal and cyclic oxidation resistance of the Ni-base superalloy K38G at 1100 °C, and performed better than the NiCoCrAlY coatings. An alumina layer formed at the glass/metal interfaces of the specimens coated by the glass-ceramic coatings with or without a NiCoCrAlY intermediate layer. The NiCoCrAlY intermediate layer was beneficial to the cyclic oxidation resistance of the glass-ceramic coatings.     

SiCP/AZ31镁基复合材料微弧氧化膜结构与性能分析

采用微弧氧化表面处理技术在SiC颗粒增强AZ31镁基复合材料表面制备保护性陶瓷膜.分析了陶瓷膜的表面形貌、截面组织和相组成,并测量了膜层的硬度、热震和电化学腐蚀特性.结果表明,陶瓷膜由MgO、Mg₂SiO₄和少量同电解液组成元素相关的相所组成,膜内还残留少量SiC_P增强体.膜层的最高硬度可达到HV800,比复合材料基体提高五倍以上.经过100次热循环(500℃→水淬)后膜层与复合材料结合良好,显示该膜层有较好的抗热震性能.微弧氧化处理后,SiC_P/AZ31镁基复合材料的抗腐蚀能力得到较大提高.     

电子束沉积SiC/ZrO2热防护层的结构优化及其抗热震性能

高性能辐射热防护层是高超声速飞行器金属热防护系统的重要组成部分。为获得高性能的热防护层,利用L5 EB-PVD电子束物理气相沉积设备在Haynes 214镍基合金表面沉积了SiC/ZrO2防护层,测试了其在热循环条件下的抗热震性能;通过分析其沉积温度及厚度对残余热应力的影响,确定了热防护层的沉积工艺参数。结果表明:热防护层在800℃和900℃循环80次后未出现明显的宏观裂纹;1000℃循环60次后,SiC表面层应力集中区出现裂纹,在交变热应力作用下,裂纹不断扩展形成网状龟裂纹,最终导致热防护层剥落;热膨胀系数不匹配导致热防护层在急冷急热热震过程中产生热应力是导致其失效的主要原因。