Oxidation and thermal fatigue of EB-PVD thermal barrier coatings on tube superalloy substrate

Two-layer structure thermal barrier coatings （TBCs） （NiCoCrAIY （bond coat）＋（6%-8%, mass fraction） Y2O3-stabilized ZrO2（YSZ top coat）） were deposited by electron beam physical vapor deposition （EB-PVD） on tube superalloy substrates. The samples were investigated by isothermal oxidation and thermal shock tests. It is found that the mass gains of the substrate with and without TBCs are 0.165 and 7.34 mg/cm^2, respectively. So the TBCs system is a suitable protection for the substrate. In thermal shock tests the vertical cracks initiate at the top coat and grow into the bond coat, causing the oxidation of the bond coat along the cracks. Failure of the TBCs system occurs by the spallation of the YSZ from the bond coat, and some micro-cracks are found at the location where the fragment of the YSZ top coat spalled from.     

Macro-microscopic morphology and phase analysis of TiAl-based alloys sheet fabricated by EB-PVD method

TiAl-based alloys sheet with thickness of 0.3-0.4 mm as well as dimension of 150 mm×100 mm was fabricated successfully by using electron beam-physical vapor deposition（EB-PVD） method. The microscopic morphology and phase composition of specimens in various states were analyzed by atomic force microscope（AFM）, scanning electron microscope（SEM） and X-ray diffractometer（XRD）, respectively. The results indicate that the as-deposited TiAl-based alloys sheet has good surface quality and is composed of γ, α2 and r phase. There is natural delamination inside the sheet, of which the microstructure is columnar crystal, and the component shows a gradient change along the normal direction of substrate. After the vacuum hot pressing treatment and subsequent homogenization treatment, the columnar crystal transforms into the coarse fully lamellar microstructure, the delarnination phenomenon and τ phase disappear, α2 phase decreases obviously, and the composition tends to uniformization.     

垂直裂纹对EB-PVD热障涂层热循环失效模式的影响

对电子束物理气相沉积（EB-PVD）双层结构热障涂层在热循环过程中形成的陶瓷层垂直裂纹对涂层失效模式的影响进行了研究.结果表明,陶瓷层表面垂直裂纹出现在热循环初期,但并未造成涂层的早期剥落;随着热循环次数增加,垂直裂纹网格变密.有限元计算表明,垂直裂纹的形成在试样中部产生了类似于试样边缘的剪应力集中效应.经过长时间热循环后,当陶瓷层等轴晶区的强度或者热氧化生长层（TGO）的强度小于边缘效应产生的剪应力时,涂层在试样的中部以垂直裂纹网格形状发生剥落失效.     

EB-PVD梯度热障涂层的制备及其热疲劳性能

采用ＥＢ－ＰＶＤ的方法,连续蒸发按一一分比混合的Ａｌ＋Ａ１２Ｏ３＋ＺｒＯ２混合源,在Ｎｉ基高温合金基体上制备了一种新型结构的热障涂层,ＳＥＭ和ＥＤＳ的观察、分析表明,这作层实现了由金属粘结层向陶资顶层的微观结构的梯度过渡和化学成分的连续变化。涂层的基本结构为ＮｉＣｏＣｒＡ１Ｙ／Ｎｉ３Ａｌ＋Ａ１２Ｏ３／Ａ１２Ｏ３ＺｒＯ２／ＺｒＯ２。这北度热障涂层在１０５０℃的抗高温氧化性能优于传统的二层结构的热障涂     

一种多层厚微叠层材料再结晶行为的研究

在1050℃的真空条件下,对一种NiCoCrAl/ZrO2-8Y2O3(质量分数,%,下同)(YSZ)多层厚微叠层材料试样分别进行了0.5,2和4h热处理,以研究其再结晶行为。该微叠层材料除了含有金属/陶瓷薄叠层结构外,还包含5层厚度在5~25μm之间的厚金属韧性层。研究表明,在热处理过程中,厚度小于13μm金属层较容易发生再结晶,而且再结晶的晶粒尺寸随着层厚的增加而增加;而厚度超过20μm的金属层则较难发生再结晶。此外,结合对试样中热应力的有限元分析,探讨了金属韧性层厚度对其再结晶行为的影响机理。     

EB-PVD制备Ni-20.3Cr-4.6Co-2.1Al薄板微观组织结构研究

对采用电子束物理气相沉积(EB-PVD)技术制备Ni-20.3Cr-4.6Co-2.1Al高温合金薄板的微观组织结构进行了研究。结果表明:制备态合金薄板相组成为-γNi基固溶体,不存在第二相。合金在制备过程中的宏观、微观应力以及晶粒细化作用,导致相同位置衍射峰叠加,产生衍射峰宽化现象,具有不对称性。在OM和SEM下观察组织致密均匀、晶粒细化,晶粒间耐蚀程度存在差异;TEM观察其组织结构,存在应变条纹,亚结构缺陷主要为孪晶;AFM三维形貌图反映出晶粒光整、没有棱面,说明合金蒸气在结晶时,发生由气相→液相→固相的转变过程。     

基体温度对TC11钛合金EB-PVD修复层组织及振动疲劳寿命的影响

为了研究温度对修复层性能的影响,采用电子束物理气相沉积(EB-PVD)技术在TC11平板试样上制备了修复层,利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和能谱仪(EDS)研究了不同温度下修复层的成分及组织形貌变化,并通过振动疲劳试验等方法研究了温度对修复层振动疲劳寿命的影响。结果表明:在600~800℃进行修复时,修复层为柱状晶组织。修复层的致密性随温度升高而变大,这种变化也会影响修复后试片的振动疲劳性能,修复层柱状晶结构间隙处形成的裂纹源会造成试片疲劳性能的下降。     

电子束物理气相沉积TiAl基合金薄板的物相及显微分析

采用电子束物理气相沉积（EB-PVD）技术，成功制备了尺寸为150mm×100mm的TiAl基合金薄板，并利用光学显微镜（OM）、扫描电子显微镜（SEM）和x射线衍射（XRD）等测试手段，对真空退火或热压前后试样的显微形貌、物相组成等进行了分析。结果表明，蒸镀态TiAl基合金薄板由 γ相、α2相和ι相组成，成分呈梯度变化，内部自然分层，显微组织结构为柱状晶；经1000℃，16h的真空退火处理后，柱状晶和τ相消失，α2相含量显著减少，成分趋于均匀化；而经1250℃，1h的真空热压处理后，材料致密度得到明显提高。TiAl基合金薄板经真空退火或热压处理前后，断裂方式由沿晶断裂转变为解理断裂和沿晶断裂的混合断裂方式。     

高温拉压环境下DZ125高温合金的热障涂层失效

采用电子束物理气相沉积法（EB-PVD）在定向凝固Ni基高温合金DZ125基体上制备了NiCoCrAlY粘结层和YSZ陶瓷层，研究了高温拉压环境下热障涂层的失效模式，并对其进行了有限元分析。实验结果表明，热障涂层的失效与仅受热载荷作用下的有很大不同，仅有热载荷作用下的热障涂层裂纹多萌生于热氧化层（TGO）内部，进而扩展引起热障涂层的失效。而高温拉压试验后热障涂层体系存在两种裂纹，分别萌生于TGO／粘结层界面和粘结层／扩散层界面附近。有限元模拟结果显示TGO／陶瓷层和TGO／粘结层处存在应力状态的转变和应力值的突变，径向应力的突变导致了界面分离现象的产生，而轴向应力的突变加速了垂直于界面裂纹的扩展，并导致了试样的最终断裂。     

用EB-PVD技术制备Ni-Co-Cr基高温合金的组织和力学性能

采用电子束物理气相沉积（EB-PVD）技术制备出厚度为0．3mm的Ni-Co-Cr基高温合金薄板，并用X射线衍射仪、光学显微镜、扫描电镜和拉伸设备研究了该合金热处理前后的显微组织及力学性能。结果表明，制备态合金为微晶结构，缺陷相对较多；热处理后晶粒迅速长大，缺陷密度大幅下降，并在晶粒内部形成了主要的沉淀强化相γ’相。与制备态合金相比，热处理后合金的力学性能得到明显改善，说明EB-PVD技术可以为制备性能优良的高温合金薄板提供一条新途径。     

Microstructure and electrical conductivity of high volume Al2O3-reinforced copper matrix composites produced by plasma spray

A mixture of Cu/-Al₂O₃ (30:70 in vol.%) feedstock powder was plasma-sprayed onto a graphite substrate in order to investigate the electrical conductivity and microstructure of the deposits. As input power increased, the amount of phase transformed γ-Al₂O₃ and the volume fraction of Al₂O₃ in the plasma-sprayed composites increased, while the electrical conductivity decreased. Cuprite (Cu₂O) was also found in the deposits. The electrical conductivities of the plasma-sprayed Cu/Al₂O₃ composites were compared to those of the different predictive models. It was revealed that the two-phase self-consistent predictive model had the closest agreement with the measured values.     

热障涂层的CMAS腐蚀失效及对策研究综述

研制具有长寿命、高性能的热障涂层（TBCs）,是制造我国大功率航空发动机、发展新一代超音速战机的一项十分紧迫的任务。由于外来沉积物CaO-MgO-Al2O3-SiO2（CMAS）渗入涂层而导致TBCs失效的现象越来越受到人们的重视,在过去的一段时间里,很多学者对CMAS渗入后涂层的失效机理进行了大量的研究并尝试了一些缓解CMAS渗入涂层的方法。本文针对当前应用最为广泛的“层状多孔结构”的等离子喷涂涂层及“细长柱晶结构”的电子束辅助物理气相沉积涂层,系统地梳理了近年来国内外学者对TBCs在CMAS渗入条件下的失效机制及涂层缓解CMAS渗入方面的最新研究成果,为制备高性能的TBCs提供帮助。     

Oxidation behaviour of CoNiCrAlY bond coats produced by plasma, HVOF and cold gas dynamic spraying

This paper examines and compares the microstructure and oxidation behaviour of CoNiCrAlY coatings manufactured by the APS, HVOF and CGDS deposition techniques. The coatings microstructural features were characterized by means of SEM and XRD analyses. Coating samples were then subjected to isothermal heat treatments at 1000 °C. Oxide growth rates were obtained from a series of mass gain measurements while oxide scale compositions were determined from SEM, XRD and EDS analyses. Results obtained in this study show that the as-sprayed CGDS and HVOF coatings exhibit similar microstructures, whereas the APS coating features high levels of visible defects and oxide content. Oxidation experiments revealed low oxide growth rates for both the CGDS and HVOF coatings as a result of low porosity and oxide content. The oxide scale on the CGDS and HVOF coatings after 100 h of oxidation were composed mainly of alumina without the presence of detrimental fast-growing mixed oxides. The presence of Cr₂O₃ and dispersed NiO was however also observed for the HVOF coating. As expected, the APS coating featured the onset of mixed oxides in the early stages of oxidation. From these results, it appears that potential improvements to the bond coat oxidation behaviour can be achieved using low-temperature processing methods such as CGDS.     

High temperature properties of thermal barrier coatings obtained by detonation spraying

NiCrAlY/YPSZ and NiCrAlY/NiAl/YPSZ thermal barrier coatings (TBCs) were successfully deposited by detonation spraying. The results indicated that the detonation sprayed TBCs included a uniform ceramic coat containing a few microcracks and a bond coat with a rough surface. The lamellar structure and the presence of cracks and impurities could reduce the thermal conductivity of the ceramic coat. Oxidation kinetics at 1000–1150 °C of detonation sprayed TBCs have been measured and discussed. The role of a Ni–Al intermediate layer in improving the oxidation resistance of duplex TBCs has also been studied.     

Tribological performance of DLC films deposited on ACM rubber by PACVD

In this paper the tribological and adhesive performance of DLC films prepared by plasma assisted chemical vapor deposition on acrylic rubber (ACM) are studied. The effect of applied load and sliding velocity on the coefficient of friction and wear rate has been investigated. Effects of the rubber substrate and of ageing of the coated samples have also been explored. In addition, the adhesion of the DLC films to the rubber substrates is evaluated via stretch tests and the measured adhesion strength is larger than 40 MPa, indicating a superb adhesion to the substrate. It is shown that the tribological performance is greatly influenced by the viscoelastic properties of the substrate, and higher coefficients of friction are obtained at higher loads and velocities. The wear followed a similar trend, although very low in all the cases.     

Microstructure and wear resistance of double-layer TiN/PSZ coatings from alkoxide solutions by H2O-containing thermal plasma CVD

Double-layer TiN/PSZ coatings approximately 2 µm thick were deposited on Si wafers and WC-Co cutting tools from Ti-, Zr-, and Y-alkoxide solutions by Ar/H₂/N₂ thermal plasma chemical vapor deposition with water functioning as an oxidant. A PSZ layer was deposited on TiN films upon oxidation of Zr- and Y-alkoxides by H₂O using five-step-wise and pulse-type supply methods. The double-layer coatings were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), in-depth glow discharge optical emission spectrometry, and cutting tests. Two H₂O supply methods, two-stage pulse and five-step-wise supply methods, were shown to be suitable for the formation of the double-layer coatings by SEM and TEM observation of surface and cross-sectional microstructures. Cutting tests for the double-layer coatings deposited on WC-Co cutting tools prepared by the above two H₂O supply methods were carried out to evaluate their wear resistance.     

Disperse-strengthening by nanoparticles advanced tribological coatings and electrode materials for their deposition

Two types of electrode materials were developed using self-propagating high-temperature synthesis (SHS) and powder metallurgy: 1- composite with nanosized additives; 2- nanostructured cemented carbide WC-Co. Electrospark deposition (ESD) was applied to produce tribological coatings which were disperse-strengthened by incorporation of nanosized particles. Nanostructured electrodes of cemented carbides WC-8% Co provide increasing density, thickness, hardness, Young's modulus, and wear resistance of ESD-coatings. Positive effects of nanostructural state of the electrodes on the deposition process and structure/properties of the coatings are discussed. In that case the tungsten carbide phase becomes predominant in the coatings. A mechanism of the dissolution reaction of WC in Ni at the contact surface of the electrode was proposed. It was shown that formation of the coating structure is initiated on the electrode and accomplished on the substrate.     

Characterization of titanium nitride films deposited by cathodic arc plasma technique on copper substrates

TiN films were deposited directly on Cu substrates by a cathodic arc plasma deposition technique. The films were then characterized by X-ray diffraction (XRD), grazing incidence X-ray diffraction (GID), (TEM), Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). The preferred orientation of the film changed from (200) to (111) with increasing film thickness. Analyses of both the XRD and GID results showed that in the highly (111) textured grains, the (111) plane was approximately parallel to the film surface, while in the (200) textured grains, the (200) plane was tilted away from the film surface. Small-elongated crystallites with a large aspect ratio and textured grains were found on the TiN surface. AES, which was employed to examine the concentration depth profile, showed no apparent interdiffusion between Cu and TiN during the growth of the film. XPS results showed that amorphous TiO₂, as well as titanium oxynitride, was present on the TiN surface. The spectra of Ti-2p, N-1s, O-1s and Cu-2p before and after the film being sputter etched through the entire film region were also discussed.     

Role of thermal stability and vapor pressure of bis(2,2,6,6-tetramethyl-3,5-heptanedionato)magnesium(II) and its triamine adduct in producing magnesium oxide thin film using a plasma-assisted LICVD process

Thin films of magnesia were deposited on various substrates using plasma-assisted liquid injection chemical vapor deposition with volatile Mg(tmhd)₂·2H₂O (1) (tmhd = 2,2,6,6-tetramethyl-3,5-heptanedione). The precursor complexes, Mg₂(tmhd)₄·(2), and Mg(tmhd)₂·pmdien (3) (pmdien; N,N,N′,N″,N″-pentamethyldiethylenetriamine) were prepared from Mg(tmhd)₂·2H₂O (1). The temperature dependence equilibrium vapor pressure (p_e)_T data yielded a straight line when log p_e was plotted against reciprocal temperature in the range of 360–475 K, leading to standard enthalpy of vaporization (Δ_vapH°) values of 59 ± 1 and 67 ± 2 kJ mol^− 1 for (2) and (3) respectively. Thin films of magnesium oxide were grown at 773 K using complex (1) on various substrate materials. These films were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray for their composition and morphology.     

等离子喷涂热障涂层热震失效过程及残余应力分析

采用等离子喷涂技术在高温合金上制备了热障涂层(粘接层为NiCoCrAlY,陶瓷层为ZrO2-8%Y2O3),利用扫描电镜(SEM)、拉曼光谱(RFS)等试验手段研究了热障涂层热震失效的过程及残余应力大小和分布状态。结果表明:150次热循环后,陶瓷层和热生长氧化物(TGO)生成裂纹,其中陶瓷层的裂纹已扩展至TGO;350次热循环后,出现贯通陶瓷层与金属过渡层的纵向裂纹,涂层局部出现剥离,剥离位置位于TGO与陶瓷层界面;拉曼光谱(RFS)分析结果显示TGO内应力水平分布不均,局部厚大区和凸凹处残余应力较大,是裂纹萌生、扩展的主要部位。