Thermal cycling performance of La_(2)Ce_(2)O_(7)/YSZ TBCs with Pt/Dy co-doped NiAl bond coat on single crystal superalloy

Thermal barrier coatings(TBCs) consisting ofLa_(2)Ce_(2)O_(7)(LCO) and Y_(2)O_(3)-stabilized-ZrO_(2)(YSZ) doubleceramic layer and Dy/Pt co-doped NiAl bond coat were produced by electron beam physical vapor deposition(EBPVD). Thermal cyclic performance of the TBCs was evaluated by flame shock testing at 1300 ℃. For comparison, the TBCs with a undoped NiAl bond coat were also studied. The microstructural evolution and failure mechanisms of the above TBCs during thermal cycling were investigated. Spallation failure of the TBCs with the undoped bond coat occurs after around 500 cycles by cracking at the interface between YSZ ceramic layer and thermally grown oxides(TGO) layer. The TBCs with Pt/Dy modified bond coat reveal improved interface bonding even after 1200 thermal cycles, whereas some delamination cracks are presented in the LCO layer. On the other hand,the Pt/Dy modified bond coat effectively suppresses the formation of the needle-like topologically closed packed phases(TCP) in the single crystal superalloy.

Cyclic Corrosion Behavior of Pt/Ru-Modified Bond Coatings Exposed to NaCl Plus Water Vapor at 1050℃

In the present investigation,Pt/Ru-modified bond coating consisted of 2 μm Pt＋2 μm Ru was deposited on a nickel-based superalloy by electroplating method and followed by conventional Al pack cementation.The cyclic corrosion behavior of Pt/Ru-modified bond coating exposed to NaCl plus water vapor has been investigated under atmospheric pressure at 1050℃.The result shows that the cyclic corrosion life of Pt/Ru-modified bond coating is longer than that of the conventional Pt-modified aluminide coating in the presence of NaCl plus water vapor.The addition of Ru makes the coating possess the increased strength and suppress the rumpling behavior.The absence of rumpling may be responsible for the improved corrosion resistance of Pt/Ru-modified aluminide coating.

Optimized composition for bonding assistant coat in carbon steel sandwich panels

On the basis of the alloying theory of bonding assistant coat （BAC）, taking into account of the interaction of alloy elements, the regressive equation, which relates the wetting ability of bonding assistant coat with the contents of Mn, Ni, Si, Sn, and B, was es- tablished by using quadratic regression orthogonal design of five factors. The influence of elements and their interaction on the wetting ability was analyzed. The ranges of alloy elements were optimized. The melting point of bonding assistant coat was measured by using differential thermal analysis. The results show that the interactions of Ni and Mn, Ni, and Sn can increase the wetting ability obviously and the melting point of bonding assistant coat has been decreased.

The effect of zirconium coating on bonding strength of porcelain to titanium

The Zr coating was deposited on titanium surface using the magnetron sputtering technique. Effects of Zr coating on microstructure and mechanical properties of porcelain fired to titanium have been investigated. The results show that interdiffusion of elements occurs during porcelain firing, and the Zr coating can effectively protect titanium surface from excess oxidation. The strength of bond zone with Zr coating deposited for 1 hour reaches 29. 7 MPa, which has increased by 26.4% as compared with that of bond zone without coating （23.5 MPa）.

Electrochemical and Reaction Bonding Processing of Thick ZrO_2/Al_2O_3 Composite Coatings

A novel technique combining electrophoretic deposition (EPD) and reaction bonding process (RBP) is developed to fabricate thick ZrO2/Al2O3 composite coatings. Mixed organic solvents are used here to make suspension containing yttria stablised zirconia (YSZ) and aluminium (Al). The results show that densely packed green form coatings are deposited using a mixture of ethanol and acetylacetone as suspension medium and ball milling for 48 hours. On subsequent heat treatment, melting and oxidation of aluminium in the green forms promote densification during sintering. By these means, thick, uniform and crack-free ZrtVA^Oa composite coatings have been fabricated on metal substrate.

EVALUATIONS OF INTERFACE BOND STRENGTH BETWEEN THERMAL SPRAYED COATINGS AND SUBSTRATS

A novel test method of measuring the interface bond strength between a thermal sprayed coating and substrate is put forward first in this paper. The test method is simple and reliable, and exists no any inherent shortcoming and controversy. The interface bond strength obtained by the test method is completely the inherent property of the interface and depends only on coating material properties, spray conditions, and technique of depositing the coating. By extensive tests, it is shown that the test tesults are very tepeatable and reliable. Furthermore, from this test, the critical coating thickness under which the coating spall can not emerge is also obtained.

Colloidal Alumina-bonded TiB_2 Coating on Cathode Carbon Blocks in Aluminum Cells

Self-propagating high-temperature synthesis (SHS) with reduction process was used to fabricate TiB2 powder from TiO2-B2O3-Mg system. The colloidal alumina-bonded TiB2 paste was prepared and coated on the cathode carbon blocks. Various properties of the baked paste such as the corrosive resistance, thermal expansion and wettability were tested. Experimental results showed that the colloidal alumina-bonded TiB2 coating could be well wetted by liquid aluminum; and the thermal expansion coefficient of the coated material was 5.8x10(-6) degreesC(-1) at 20-1000 degreesC, which was close to that of the traditional anthracite block cathode (4x10(-6) degreesC(-1)); the electrical resistivity was 8 mu Omega (.)m at 900 degreesC when the content of alumina in the coated material was about 9% in mass fraction. In addition, some other good results such as sodium resistance were also reported.

PREPARATION AND ITS WEAR RESISITANCE OF WC-Co/NiCrBSi METALLURGICAL BONDED COMPOSITE COATING

A WC-Co/NiCrBSi composite coating was made on 42CrMo steel through vacuum brazing technology. The effects of cobalt and WC-17Co content on the properties of the coating were analyzed. The abrasive wear resistance decreased as the cobalt content increased. The tensile strength of the coating increased with the increase of the WC-17Co content and the maximum strength approaches to 184MPa. The abrusive property of the composite coating is better than that of the WC-17Co/NiCrBSi flame overlaying and CoCrW overlaying.

Bonding strength of graded anti-corrosive coatings of fluoroethylenepropylene (FEP)/polyphenylene sulfide (PPS)

Fluororesin-based anti-corrosive coatings including graded FEP/PPS were prepared on carbon steel by melt powder coating, the bonding strength of all coating systems was determined by the pull-off test. It is found that the poor adhesion of fluororesin coatings to metallic substrates is improved obviously by the graded coating structure of FEP/PPS, and the bonding strength reaches up to 11.8 MPa for the five-layer system. Examination by electron probe microanalysis （EPMA） verifies that the distribution of main components is graded in the five-layer system, which is responsible for the enhancement of the interfacial bonding.

Effects of intermixing process on bonding strength of IBED CrN coatings

The coating substrate bonding strengths under different intermixing processes were evaluated by scratch and spherical rolling contact fatigue methods. The results show that for low bombarding energy of N ions dynamic recoiling at 10 keV and 20 keV, the coating layers are of excellent bonding strengths. The bonding strength of CrN coating with 40 keV static recoiling is higher than that of low energy(20 keV). On the other hand, the bonding strength of coating with 40 keV dynamic recoiling is much lower than that of static recoiling at the same energy and even less than that of dynamic recoiling intermixings at 10 keV and 20 keV energy. The results of scratch and spherical rolling contact fatigue methods exhibit the same trend for each group of recoiling methods, yet the results of the scratch and fatigue tests for two groups do not agree with each other.

镁合金表面DCPD涂层的制备及其界面结合机制研究

目的研究CaHPO_(4)·2H_(2)O(DCPD)与Mg的界面结合机制,以提高DCPD在镁合金表面的界面结合强度。方法利用电镀法在AZ31镁合金表面制备DCPD涂层,采用SEM、XRD、XPS等对涂层形貌及结构进行表征。同时,运用分子动力学模拟(MD)对DCPD在Mg表面形成机制进行研究,通过统计界面层中不同组分的径向分布函数、密度分布、均力势、总能量等的变化,揭示DCPD/Mg的界面结合能、结合位点及结合方式。结果通过电镀法形成的DCPD涂层形貌为致密的荷花瓣状晶体,主要成分为CaHPO_(4)·2H_(2)O。模拟结果表明,CaHPO_(4)·2H_(2)O的4个晶面(010)、(-120)、(11-1)、(111)、(-120)与Mg的结合能最强(163.63 kJ/mol)。其中起“铆钉”作用的基团是HPO_(4)^(2-)和H_(2)O,结合位点主要为O与Mg,即HPO_(4)^(2-)和H_(2)O通过静电作用及范德华力与Mg形成Mg-HPO_(4)^(2-)和Mg-H_(2)O偶极对。研究发现,形成的偶极对中HPO_(4)^(2-)及H_(2)O的配位数分别为0.75和1.16,Mg-H_(2)O的解离能更大,结构更稳定。结论提出改善DCPD/Mg结合强度的方法,电镀前可将镁合金置于NH4H_(2)PO_(4)溶液中浸泡片刻,促进CaHPO_(4)·2H_(2)O(-120)晶面的形成。

涂层界面反射超声的梳状滤波效应及其结合质量成像检测研究

涂层结构的界面结合质量可以通过超声无损检测技术进行有效表征。基于涂层界面超声传播模型及其反射信号特征研究,发现其回波信号具有梳妆滤波效应。理论分析表明,超声反射系数和相位都会随界面刚度而变化,在此基础上基于梳状滤波效应构建了适用于界面结合强度检测的频域特征参数。利用高频水浸超声扫查系统对不同结合质量的涂层样品进行了成像测试,并与标准划格法测试结果对比。研究结果表明,在涂层结合强度差异较小的情况下,通过回波信号的反射系数和梳状滤波效应频域特征参数都可以区分结合质量为0级和2级样品,而频域特征参数能够显著提升结合质量成像结果的对比度。该研究将为大批量涂层界面质量无损、在线、全覆盖检测提供理论基础与技术支撑。

稀土镁合金表面激光熔覆AlSi12/TiN复合涂层的组织及性能研究

采用高速激光熔覆技术在Mg-Gd-Y-Zr镁合金表面制备了AlSi12/TiN复合涂层。通过光学显微镜(OM)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)、摩擦磨损实验以及电化学分析测试等方法,研究不同含量陶瓷强化相Ti N涂层的显微结构、熔覆层结合强度、摩擦磨损性能以及耐腐蚀能力。结果表明,复合涂层主要由α-Mg、Mg_(2)Si枝晶、Al_(12)Mg_(17)、Al_(3)Mg_(2)金属间化合物以及Ti N强化相组成。由于存在强化的第二相和细化的晶粒,AlSi12/TiN复合涂层的摩擦系数、维氏硬度及结合强度分别达到0.45、210 HV0.1和40 MPa。此外,与镁合金基体相比,腐蚀电位提高683 m V,自腐蚀电流密度降低了2个数量级。利用激光熔覆技术可在Mg-Gd-Y-Zr镁合金表面制备结合强度高的Al Si12/TiN复合涂层,有合适含量强化相存在的涂层显著提高了基体表面的耐磨损与耐腐蚀性能。

改变聚合物表面张力的方法与案例

了解聚合物表面张力(或表面能),对研究聚合物在涂层、印刷、黏接等方面的操作具有重要指导意义[1]。本文介绍了聚合物表面张力定义和部分聚合物表面张力测试方法,分别对涂层、印刷、黏接过程中聚合物表面张力不适时,做出了改变聚合物表面张力的对应措施,结合案例进行一定的描述。解释了对涂层、印刷、黏接后样件检测其结果的主要试验方法。聚合物表面张力改变是较复杂的过程,涉及到聚合物各方面性能,改变表面张力目的是让聚合物发挥更大的作用,为人所用。

镍钯金表面引线键合工艺的可靠性及应用

通过模拟前道工序的实际装配环境,研究了镀镍钯金基板在不同工况条件和不同钯/金层厚度情况下对表面键合强度的影响。结果表明,通过280℃高温回流后,镀层表面会出现少量Cu元素,但对键合强度影响不大。Au/Pd镀层厚度增加均有利于提高可键合性。在本文的镀层体系中,均可完成高可靠性键合。通过150±3℃,168 h的高温贮存试验表明,Pd和Au界面均可作为键合界面,高温贮存前后平均键合强度均在11 cN以上,满足标准且非常稳定。

碳化硅陶瓷基复合材料表面环境障涂层结合强度

SiC陶瓷基复合材料(SiC-based ceramic matrix composites,SiC-CMC)是发展高推重比航空发动机理想的高温结构材料。为了防止发动机服役环境下燃气(富含H2O和O_(2))对SiC-CMC的腐蚀,需要在其表面制备抗水氧腐蚀、抗燃气冲刷和抗热冲击性能优异的环境障涂层(environmental barrier coatings,EBCs)。在评价EBCs性能的诸多因素中,其与SiC-CMC基体之间的结合强度是一个重要技术指标,但结合强度的极限值一直未被探究清楚。本工作研究影响结合强度的主要因素,包含SiC-CMC基体状态、单晶Si的拉伸强度极限,以及Si黏结层的制备工艺等,获得了制备最高结合强度的有效途径。在EBCs与SiC-CMC组成的体系中,基体内部SiC纤维布之间的界面是结合强度最薄弱的部位,其次是EBCs的Si层。整个体系的结合强度极限值是15 MPa,它是单晶Si在[400]晶向的拉伸强度极限。采用大气等离子喷涂或者超音速火焰喷涂的Si黏结层结合强度相似,均低于同样工艺制备的莫来石或Yb2Si2O7涂层。

MCrAlY金属黏结层高温失效行为研究进展

随着航空发动机与燃气轮机涡轮进口温度的不断提高,MCrAlY(M=Ni,Co或NiCo)包覆型涂层因具有抗高温氧化以及高的热膨胀系数等优点,成为广泛应用的热障涂层金属黏结层材料。然而,高温服役环境下热障涂层中金属黏结层与陶瓷面层界面应力分布状态愈加复杂,黏结层界面失效导致陶瓷面层的剥落,限制了其在热防护涂层领域的发展。本文简述了黏结层的发展进程,重点阐述高温相转变、热应力和生长应力增加以及S元素扩散等因素导致的黏结层界面的失效行为,分析黏结层界面失效机理,归纳总结了国内外针对金属黏结层界面失效的改进研究工作,并在此基础上提出采用稀土及纳米颗粒协同强化MCrAlY材料,为未来热障涂层体系的优化设计提供了研究方向。

激光冲击金属黏结层高温热循环应力演化规律的有限元模拟

目的 探索激光冲击(LSP)对高温热循环(反复升温、保温和降温)过程中热障涂层中的热生长氧化物(TGO)表面及TGO/黏结层(BC)界面应力分布的影响规律。方法 基于真实TGO形貌,建立有限元模型,从应力演化角度分析LSP改性(LSPed)与未改性(Non-LSPed)试样危险区域的失效形式;使用拉曼光谱法(RFS)对氧化后的金属黏结层进行残余应力测试。结果 TGO应力分布随着形貌的起伏呈现相应的起伏变化。TGO表面压应力最大值出现在波峰位置,经10次热循环后LSPed试样TGO表面S11(平行于涂层表面的正应力)压应力最大值大于Non-LSPed试样,经50次热循环后LSPed试样TGO表面压应力最大值远小于Non-LSPed试样;随着热循环次数的增加,2类试样TGO/BC界面S11应力的差别变小。LSPed试样TGO表面S22(垂直于涂层表面的应力)应力随着热循环次数的增加逐渐增大,但S22拉应力小于250 MPa,应力总体偏低。TGO/BC界面S22、S12(平行于涂层表面的剪切应力)应力随循环次数的变化规律基本一致,经10次热循环后,LSPed试样的S22、S12应力均大于Non-LSPed试样;经50次热循环后,2类试样界面的S22、S12应力相差不大。结论 文中构建的TGO应力有限元仿真模型,模拟结果与测试结果吻合。LSP通过调控TGO生长速度,可以有效缓解TGO生长过程中应力的剧烈变化,大幅降低TGO表面S11和S12应力最大值,进而降低TGO表面产生垂直于表面贯穿裂纹和剪切破坏的风险,LSP对TGO表面(TGO/BC界面)应力状态的影响较小。

润滑耐磨耐蚀功能一体化有机黏结涂层的研究进展

随着现代化装备技术的快速发展,高端机械装备服役工况变得愈加复杂苛刻,磨损与腐蚀耦合损伤加速了高端机械装备运动部件的损伤失效,导致装备服役寿命大幅缩减,带来了严重的安全问题。润滑耐磨耐蚀功能一体化有机黏结涂层克服了润滑耐磨涂层和防腐蚀涂层的单一功能局限,为解决运动部件的磨损和腐蚀问题提供了有效方案。文中首先探讨了关键运动部件面临复杂服役工况的严峻挑战、材料磨损与腐蚀耦合的损伤机制;然后分别由黏结剂、填料和润滑剂3个方面介绍了目前润滑耐磨耐蚀功能一体化有机黏结涂层的研究进展,对涂层的组成结构与力学性能、摩擦学性能、耐腐蚀性能间的构效关系进行了分析,并对不同涂层的局限性进行了概述;之后详细总结了润滑耐磨耐蚀功能一体化涂层的应用现状;最后对润滑耐磨耐蚀功能一体化涂层的发展方向进行展望。

高粗糙度NiCrB打底层对陶瓷颗粒增强聚合物基复合涂层性能的影响

目的提高水电装备过流部件表面聚合物基复合抗空蚀涂层与碳钢基材的结合强度,解决因聚合物涂层局部分层,使得水进入聚合物涂层与碳钢界面,引起碳钢快速氧化膨胀,导致涂层快速剥落的难题。方法采用电弧喷涂技术在碳钢基材表面制备NiCrB高粗糙度耐腐蚀打底层,然后在其上涂覆聚氨酯基复合涂层。通过激光共聚焦显微镜、扫描电镜,以及结合强度测试、电化学测试和中性盐雾测试,分别表征打底层的表面形貌、致密度,并评价打底层对聚氨酯基复合结合强度和防腐蚀性能的影响。结果通过调控参数,在NiCrB打底层表面形成由熔滴气化后沉积形成的规则排布凸起颗粒,涂层的表面粗糙度相较于常规热喷涂涂层得到显著提高,在Ra 10.95~37.24μm内可有效调控,且涂层的孔隙率均低于1.5%。添加高粗糙度致密NiCrB打底层后,聚氨酯基复合涂层的结合强度由13.6 MPa升至30.5 MPa。在基体添加NiCrB打底层后,其开路电位由−0.73 V升至−0.54 V,腐蚀电位(vs.SCE)由−0.76 V升至−0.58 V,电荷转移电阻由1729Ω·cm^(2)升至8425Ω·cm^(2)。在上层聚合物涂层破损的情况下,带有NiCrB打底层的样品在接受300 h中性盐雾测试后无明显锈点,相较于无打底层样品,其盐雾腐蚀寿命提高了11倍以上。结论通过电弧喷涂NiCrB打底层可以在较大范围内实现表面粗糙度的调控,打底层的高粗糙度显著提升了聚合物基复合涂层的结合强度,打底层优异的耐腐蚀性能显著提升了聚合物基复合涂层的长效耐腐蚀性能,保障了水力过流部件的长效服役。