Sample records for zharostojkim pokrytiem nicraly

  1. Behavior of NiCrAlY coating on the TC6 titanium alloy

    Changqing Xia; Xiaomin Peng; Jia Li


    A NiCrAlY coating was deposited on the TC6 titanium substrate by arc ion plating (AIP). The structure and morphologies of the NiCrAlY coating were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the influence of vacuum heat treatment on the element diffusion behavior was studied. The results showed that the γ'-Ni3Al phase was precipitated on the NiCrAlY coating after heat treatment. The Ni3(Al,Ti), TiNi, and Ti2Ni intermetallic layers appeared at the interface from the outside to the inside at 700℃, and the thickness of the intermetallic layers increased with the increase in temperature. At 700℃ Ti and Ni were the major diffusion elements, and the diffusion of Cr was observed when the heat treatment temperature increased up to 870℃. The violent inward diffusion of Ni at 950℃ resulted in the degradation of the NiCrAlY coating.

  2. Formation of NiCrAlY laser cladding with preplaced method; Funtai tofu reza kuraddingu ho ni yoru NiCrAlY himaku no keisei

    Iwamoto, H. [Chiyoda Chemical Engineering and Construction Co. Ltd., Tokyo (Japan)] Sumikawa, T. [Isuzu Motors Ltd., Tokyo (Japan)] Nishida, K. [Ehime Univ., Ehime (Japan). Graduate School; Nishida, M.; Araki, T. [Ehime Univ., Ehime (Japan). Faculty of Engineering


    Cladding technique on the surface of structure materials using high corrosion resistance and wear resistance materials has been used in many fields as compared to conventional one. The heat source for cladding was mainly arc welding, however, these recent years, laser cladding where laser having special characteristics like high control, high output density and so forth is used as a heat source, has been studied. In this report, in order to cope with the change in composition of base material, coating layer formation with preplaced method was studied systematically using NiCrAlY powder formed by mixing mechanically commercial metal powder with raw material powder and low power (1200W) CO2 laser. As a result, good NiCrAlY cladded layer with good composition and with no defect was achieved using basic powder formed by mixing mechanically the metallic powder and commercial organic binder. Cladding of broad area was possible by weaving method even at low power (1200W) CO2 laser. Cladded layer with lower dilution ratio and higher cross sectional area was achieved with smaller powder particle diameter. 9 refs., 11 figs., 4 tabs.

  3. Microstructure and Oxidation Resistance of Laser Remelted Plasma Sprayed Nicraly Coating

    Niemiec D.


    Full Text Available The article presents results of research relating to the impact of laser treatment done to the surface of plasma sprayed coatings NiCrAlY. Analysis consisted microstructure and oxidation resistance of coatings subjected to two different laser melting surfaces. The test were performed at a temperature 1000°C the samples were removed from the furnace after 25, 300, 500, 750 and 1000 hours. The investigations range included analysis of top surface of coatings by XRD characterization oxides formed types and microscopic investigations of coatings morphology

  4. Diffusional transport during the cyclic oxidation of gamma + beta, Ni-Cr-Al(Y, Zr) alloys

    Nesbitt, J. A.; Heckel, R. W.


    The cyclic oxidation behavior of several cast gamma + beta, Ni-Cr-Al(Y, Zr) alloys and one low-pressure plasma spraying gamma + beta, Ni-Co-Cr-Al(Y) alloy was studied. Cyclic oxidation was found to result in a decreasing Al concentration at the oxide-metal interface due to a high rate of Al consumption coupled with oxide scale cracking and spalling. Diffusion paths plotted on the ternary phase diagram showed higher Ni concentrations with increasing cyclic oxidation exposures. The alloy with the highest rate of Al consumption and the highest Al content underwent breakaway oxidation following 500 1-hr cycles at 1200 C.

  5. Diffusional transport during the cyclic oxidation of gamma + beta, Ni-Cr-Al(Y, Zr) alloys

    Nesbitt, J. A.; Heckel, R. W.


    The cyclic oxidation behavior of several cast gamma + beta, Ni-Cr-Al(Y, Zr) alloys and one low-pressure plasma spraying gamma + beta, Ni-Co-Cr-Al(Y) alloy was studied. Cyclic oxidation was found to result in a decreasing Al concentration at the oxide-metal interface due to a high rate of Al consumption coupled with oxide scale cracking and spalling. Diffusion paths plotted on the ternary phase diagram showed higher Ni concentrations with increasing cyclic oxidation exposures. The alloy with the highest rate of Al consumption and the highest Al content underwent breakaway oxidation following 500 1-hr cycles at 1200 C.

  6. Microstructure and Properties of HVOF-Sprayed NiCrAlY Coatings Modified by Rare Earth

    Chen, S. F.; Liu, S. Y.; Wang, Y.; Sun, X. G.; Zou, Z. W.; Li, X. W.; Wang, C. H.


    Rare earth (RE)-modified NiCrAlY powders were prepared by ultrasonic gas atomization and deposited on stainless steel substrate by high-velocity oxygen fuel spraying. The effects of the RE on the microstructure, properties, and thermal shock resistance of the NiCrAlY coatings were investigated. The results showed that the NiCrAlY powders were refined and distributed uniformly after adding RE, while the number of unmelted particles in the coatings was reduced. Moreover, the RE-modified coatings showed improved microhardness and distribution uniformity. The microhardness of the coating reached a maximum after adding 0.9 wt.% RE, being 34.4 % higher than that of coatings without RE. The adhesive strength increased and reached a maximum after adding 0.6 wt.% RE, being 18.8 % higher than that of coatings without RE. Excessive RE decreased the adhesive strength. The thermal cycle life of NiCrAlY coatings increased drastically with RE addition. The coating with 0.9 wt.% RE showed optimum thermal shock resistance, being 21.2 % higher than that of coatings without RE.

  7. Effect of enamel top coating on oxidation behavior of multi-arc ion plating NiCrAlY coating in oxygen containing water vapor

    XIE Dong-bai; ZHU Sheng-long; WANG Fu-hui


    The oxidation behavior of Ni-Cr-Al-Y coating produced by multi-arc ion plating with and without an enamel coating was investigated in flow oxygen and oxygen containing water vapor at 900 ℃. The results show that Ni-Cr-Al-Y coating exhibits low oxidation rate at 900 ℃ in pure oxygen and the oxidation kinetics follow the parabolic rate law. The presence of water vapor accelerates the oxidation rate of Ni-Cr-Al-Y coating and K38G alloy.The enamel top coating is very effective in protecting the Ni-Cr-Al-Y coating from water vapor corrosion attack, but the corrosion attack beneath the enamel coating is not observed.

  8. Interface bonding of NiCrAlY coating on laser modified H13 tool steel surface

    Reza, M. S.; Aqida, S. N.; Ismail, I.


    Bonding strength of thermal spray coatings depends on the interfacial adhesion between bond coat and substrate material. In this paper, NiCrAlY (Ni-164/211 Ni22 %Cr10 %Al1.0 %Y) coatings were developed on laser modified H13 tool steel surface using atmospheric plasma spray (APS). Different laser peak power, P p, and duty cycle, DC, were investigated in order to improve the mechanical properties of H13 tool steel surface. The APS spraying parameters setting for coatings were set constant. The coating microstructure near the interface was analyzed using IM7000 inverted optical microscope. Interface bonding of NiCrAlY was investigated by interfacial indentation test (IIT) method using MMT-X7 Matsuzawa Hardness Tester Machine with Vickers indenter. Diffusion of atoms along NiCrAlY coating, laser modified and substrate layers was investigated by energy-dispersive X-ray spectroscopy (EDXS) using Hitachi Tabletop Microscope TM3030 Plus. Based on IIT method results, average interfacial toughness, K avg, for reference sample was 2.15 MPa m1/2 compared to sample L1 range of K avg from 6.02 to 6.96 MPa m1/2 and sample L2 range of K avg from 2.47 to 3.46 MPa m1/2. Hence, according to K avg, sample L1 has the highest interface bonding and is being laser modified at lower laser peak power, P p, and higher duty cycle, DC, prior to coating. The EDXS analysis indicated the presence of Fe in the NiCrAlY coating layer and increased Ni and Cr composition in the laser modified layer. Atomic diffusion occurred in both coating and laser modified layers involved in Fe, Ni and Cr elements. These findings introduce enhancement of coating system by substrate surface modification to allow atomic diffusion.

  9. The influences of heat treatments and interdiffusion on the adhesion of plasma-sprayed NiCrAlY coatings

    Richard, C.S. [Universite de Technologie de Compiegne (France). Departement de Genie Mecanique; Beranger, G. [Universite de Technologie de Compiegne (France). Departement de Genie Mecanique; Lu, J. [Universite de Technologie de Troyes, Departement de Genie des Systemes Mecaniques, 10000, Troyes (France); Flavenot, J.F. [Centre Technique des Industries Mecaniques (CETIM), Departement Materiaux, 60306 Senlis (France)


    Most coatings are applied with a specific aim in mind, such as improving the base material resistance to corrosion or wear, or providing a barrier against high temperatures. These aims can obviously only be achieved if the coating is properly bonded to the substrate. This study is focused on a NiCrAlY metallic bonding layer and its adhesion on to nickel-based superalloy substrate. It also looks at the influence of different spraying methods (atmospheric plasma spraying and vacuum plasma spraying) and the influence of a post-heat treatment on adhesion of the coatings. In order to determine adherence, a Vickers indentation test was performed at the substrate/coating interface. In each case, the residual stresses were evaluated by a step-by-step hole drilling method and these were taken into account in assessing the adhesion parameters. The results were supplemented by a microstructural study of the interface. (orig.)

  10. An empirical-statistical model for coaxial laser cladding of NiCrAlY powder on Inconel 738 superalloy

    Ansari, M.; Shoja Razavi, R.; Barekat, M.


    In this study, coaxial laser cladding of NiCrAlY powder on a nickel-based superalloy is investigated from an experimental point of view so as to propose an empirical-statistical model for the process. The correlations between main processing parameters (i.e. scanning speed, powder feeding rate, and laser power) and geometrical characteristics (i.e. width, height, penetration depth, dilution and wetting angle) of single clad tracks have been predicted and are discussed using regression analysis (RA). The validity of the predictions is confirmed by providing correlation coefficient and analysis of the residuals. The correlations are established as a combined parameter (PαVβFγ) for each studied characteristic of single clad tracks. These correlations finally lead to the design of a processing map that can be practically used to select proper processing parameters for laser cladding of the particular material.

  11. Morfología de los óxidos superficiales en los recubrimientos convencionales y nanocristalinos de NiCrAlY sometidos a alta temperatura

    Picas, J. A.


    Full Text Available HVOF thermal spray process was used to produce conventional and nanostructured NiCrAlY coatings. The oxidation behaviour at 1000oC of both coatings has been studied. The morphology of the oxides suggests that the nanostructured coating exhibited improved oxidation behaviour compared to conventional counterparts.

    El objetivo del presente trabajo es el estudio de la morfología de los óxidos formados en la superficie de los recubrimientos convencionales y nanocristalinos de NiCrAlY, obtenidos mediante proyección térmica HVOF, al someter el material a 1000 ºC. El afino de grano obtenido en el recubrimiento nanocristalino de NiCrAlY parece ser el responsable de la variación de la morfología de los óxidos formados después del tratamiento a alta temperatura, lo cual sugiere que podrán presentar un mejor comportamiento frente a la oxidación en comparación con los recubrimientos convencionales.

  12. Research and fabrication of NiCrAlY thin-film strain gauges%NiCrAlY薄膜应变计的研制

    张洁; 杨晓东; 蒋书文; 蒋洪川; 赵晓辉; 张万里


    NiCrAlY thin film strain gauges are deposited on the nickel-based superalloy by radio-frequency magnetron sputtering. The effects of stabilized heat treatment at 1 000℃ on structure and surface morphology of NiCrAlY thin films are investigated and the electromechanical properties of NiCrAlY thin film strain gauges are measured. After stabilized heat treatment at 1 000℃,a layer of Al2 O3 is formed on the surface of NiCrAlY thin film,which is important cause for excellent high-temperature oxidation resistance. The variation of strain gauge resistance with temperature is linear in the temperature range from room temperature to 800℃. The temperature coefficient of resistance( TCR) is about 290 × 10-6/℃,and gauge factor( GF) is about 2. 1 at room temperature.%采用射频磁控溅射法在Ni基高温合金拉伸件上制备NiCrAlY薄膜应变计。研究了热稳定处理对NiCrAlY薄膜结构、表面形貌的影响,并且测试了NiCrAlY薄膜应变计的电学与应变性能。结果表明:热稳定处理后 NiCrAlY 薄膜应变计由于在表面形成了一层 Al2 O3膜,具有抗高温氧化的特性,在室温~800℃范围内,应变计电阻同温度呈线性变化,电阻温度系数( TCR)约为290×10-6/℃,室温下的应变计系数( GF)为2.1。

  13. Thermal failure of nanostructured thermal barrier coatings with cold sprayed nanostructured NiCrAlY bond coat

    Zhang, Q.; Li, Y.; Zhang, S.L.; Wang, X.R.; Yang, G.J.; Li, C.X.; Li, C.J. [Xi' an Jiaotong Univ., Xi' an (China)


    Nanostructured YSZ is expected to exhibit a high strain tolerability due to its low Young's modulus and consequently high durability. In this study, a porous YSZ as the thermal barrier coating was deposited by plasma spraying using an agglomerated nanostructured YSZ powder on a Ni-based superalloy Inconel 738 substrate with a cold-sprayed nanostructured NiCrAlY as the bond coat. The heat treatment in Ar atmosphere was applied to the cold-sprayed bond coat before deposition of YSZ. The isothermal oxidation and thermal cycling tests were applied to examine failure modes of plasma-sprayed nanostructured YSZ. The results showed that YSZ coating was deposited by partially melted YSZ particles. The nonmelted fraction of spray particles retains the porous nanostructure of the starting powder into the deposit. YSZ coating exhibits a bimodal microstructure consisting of nanosized particles retained from the powder and micro-columnar grains formed through the solidification of the melted fraction in spray particles. The oxidation of the bond coat occurs during the heat treatment in Ar atmosphere. The uniform oxide at the interface between the bond coat and YSZ can be formed during isothermal test. The cracks were observed at the interface between TGO/BC or TGO/YSZ after thermal cyclic test. However, the failure of TBCs mainly occurred through spalling of YSZ within YSZ coating. The failure characteristics of plasma-sprayed nanostructured YSZ are discussed based on the coating microstructure and formation of TGO on the bond coat surface. (orig.)

  14. Hot Corrosion Studies of Detonation-Gun-Sprayed NiCrAlY + 0.4 wt.% CeO2 Coated Superalloys in Molten Salt Environment

    Kamal, Subhash; Jayaganthan, R.; Prakash, Satya


    Rare earth oxide (CeO2) has been incorporated in NiCrAlY alloy and hot corrosion resistance of detonation-gun-sprayed NiCrAlY + 0.4 wt.% CeO2 coatings on superalloys, namely, superni 75, superni 718, and superfer 800H in molten 40% Na2SO4-60% V2O5 salt environment were investigated at 900 °C for 100 cycles. The coatings exhibited characteristic splat globular dendritic structure with diameter similar to the original powder particles. The weight change technique was used to establish corrosion kinetics. X-ray diffraction (XRD), field emission scanning electron microscopy/energy-dispersive analysis (FE-SEM/EDAX), and x-ray mapping techniques were used to analyze the corrosion products. Coated superfer 800H alloy showed the highest corrosion resistance among the examined superalloys. CeO2 was found to be distributed in the coating along the splat boundaries, whereas Al streaks distributed non-uniformly. The main phases observed for the coated superalloys are oxides of Ni, Cr, Al, and spinels, which are suggested to be responsible for developing corrosion resistance.

  15. Corrosion behavior of Fe-Si metallic coatings added with NiCrAlY in an environment of fuel oil ashes at 700 C

    Salinas-Bravo, V.M.; Porcayo-Calderon, J.; Romero-Castanon, T. [Instituto de Investigaciones Electricas, Gerencia de Procesos Termicos., Av. Reforma 113, C.P. 62490 Col. Palmira. Temixco. Morelos (Mexico); Dominguez-Patino, G.; Gonzalez-Rodriguez, J.G. [U.A.E.M. Centro de Investigaciones en Ingenieria y Ciencias Aplicadas., Av. Universidad 1001, C.P. 62210, Col. Chamilpa. Cuernavaca, Morelos (Mexico)


    Electrochemical potentiodynamic polarization curves and immersion tests for 300 h at 700 C in a furnace have been used to evaluate the corrosion resistance of Fe-Si metallic coatings added with up to 50 wt.% of NiCrAIY. The corrosive environment was fuel oil ashes from a steam generator. The composition of fuel oil ashes includes high content of vanadium, sodium and sulfur. The results obtained show that only the addition of 20 wt.% NiCrAlY to the Fe-Si coating improves its corrosion resistance. The behavior of all tested coatings is explained by the results obtained from the analysis of every coating using electron microscopy and energy dispersive X-ray analysis. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

  16. Properties of plasma sprayed NiCrAlY + (ZrO2 + Y2 O3 ) coating on refractory steel surface

    L(U) Tao; CHEN Fei; DING Hua-dong; HAN Dan-feng


    NiCrAlY + (ZrO2 + Y2 O3 ) thermal barrier coating was prepared on the surface of refractory steel 1Cr18Ni9Ti with plasma spraying technique. The phases and microstructure of the thermal barrier coating were determined by scanning electron microscopy(SEM) and X-ray diffraction(XRD). The results show that the bonding between thermal barrier coating and substrate is sound. The surface hardness of 1Cr18Ni9Ti reaches up to 1 000 HV, but that of substrate is only 300 HV. The patterns sprayed with CoNiCrAlY+(ZrO2+Y2 O3 ) ceramic coating have a good heat insulation effect at 800 ℃ for heat insulation temperature difference reaches 54 ℃, which increases the operating temperature and service life of refractory steel.

  17. Pengaruh NiCrAlY, Ni/Cr2O3/CrxCy Sebagai Variasi Bond Coat Dengan Penambahan Lapisan Al2O3 dan YSZ Pada Inconel 625 Terhadap Struktur Mikro Lapisan Menggunakan Metode Flame Spraying

    Aprian Immanuel


    Full Text Available Thermal Barrier Coating (TBC berfungsi untuk mengurangi temperatur substrat serta meningkatkan daya tahannya terhadap korosi dan oksidasi. Pada penelitian ini, digunakan flame spraying dari variasi bond coat (Ni-Cr-Al-Y, (Ni/CrO3/CrXCY dan tanpa bond coat serta melapisi kembali lapisan bond coat dengan Al2O3 dan ZrO2 – 8%Y2O3 sebagai Thermal Barrier Coating untuk diteliti pengaruhnya terhadap struktur mikro lapisan yang terbentuk. Hasil flame spray diamati dengan SEM pada variasi bond coat NiCrAlY ditemukan beberapa serbuk dari material top coat dengan beberapa kondisi yaitu meleleh (melted, meleleh sebagian (semi melted, dan tidak meleleh (unmelted. Ditemukan poros yang merata hampir di seluruh permukaan sampel dan munculnya pengintian retak. Perbedaan sebelum dan sesudah perlakuan ada pada persebaran setiap unsur di setiap spesimen, dan lapisan oksida yang terbentuk pada seluruh variasi bond coat

  18. Phase transformation and tribological properties of Ag-MoO3 contained NiCrAlY based composite coatings fabricated by laser cladding

    Wang, Lingqian; Zhou, Jiansong; Xin, Benbin; Yu, Youjun; Ren, Shufang; Li, Zhen


    Ag-MoO3 contained NiCrAlY based composite coating was successfully prepared on GH4169 stainless steel substrate by high energy ball milling and laser cladding. The microstructure and phase transformation were investigated by scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffraction spectrum (XRD). The tribological behavior and mechanism from room temperature to 800 °C were investigated. Results showed that MoO3 in the composite powders transformed to Mo2C reinforcement under the high energy density of laser, and a series of opposite transformation occurred during friction process. The coating showed the lowest friction coefficient and low wear rate at 600 °C and 800 °C due to the generation of Ag2MoO4 during tribo-chemical reactions and the formation of lubrication glaze on the worn surface. Ag made effective lubrication when the temperature rose up to 200 °C. The coating displayed a relatively high friction coefficient (about 0.51) at 400 °C, because though MoO3 (oxidation products of Mo2C) and Ag2MoO4 were detected on the worn surface, they could not realize effective lubrication at this temperature. Abrasive wear, adhesive wear and plastic deformation contributed to the increased friction and wear.


    于大千; 卢旭阳; 马军; 姜肃猛; 刘山川; 宫骏; 孙超


    采用电弧离子镀技术及后续热处理工艺在镍基高温合金上制备了均匀NiCrAlY涂层和梯度NiCrAlY涂层,分析了2种涂层的组织结构,对比研究了2种涂层静态空气下1000和1100℃恒温氧化行为以及1100℃的循环氧化行为.结果表明:均匀NiCrAlY涂层由γ'/γ相和少量β-NiAl相、α-Cr相组成,成分分布均匀;梯度NiCrAlY涂层具有外层富Al和内层富Cr的结构,其中外层由β-NiAl相和少量γ'/γ相、α-Cr相组成.一方面,梯度涂层的初始Al含量较高;另一方面,氧化过程中其富Cr区两侧出现了对富Al区的Al向基体扩散起阻碍作用的Cr(W)析出带.这两方面使梯度涂层长时间维持更多的Al存储相,提升了氧化膜的迅速生成及再生成能力,从而使涂层具有较好的抗氧化性能.%MCrAlY(M=Ni and/or Co) overlay coatings are wildly adopted on hot components in gas turbine engines to protect them from rapid oxidation. Various methods can be applied to prepare MCrAlY overlay coatings, which formed by the arc ion plating method possess outstanding properties in terms of interfacial strength, porosity and componential distribution, and thus excellent oxidation properties. To increase the Al content is deemed an economical and effective solution for enhancing the service performance and life for MCrAlY coatings at elevated temperature because the degradation process relies greatly on the ceaseless forming and spallation process of the protective α-Al2O3 scales during high-temperature oxidation. However, high content of Al will lower the melting point and decrease the ductility of the coating. This phenomenon can be partly resolved through a gradient coating design. In this paper, a conventional NiCrAlY coating and a gradient NiCrAlY coating have been prepared by the combined method of arc ion plating and subsequent diffusion treatment on Ni-base superalloy substrate. The microstructures, morphologies, isothermal oxidation behavior at 1000 and

  20. Resistencia a la corrosión a alta temperatura de recubrimientos NiCrAlY y NiCrFeNbMoTiAl depositados por APS

    José Luis Tristancho-Reyes


    Full Text Available La corrosión a alta temperatura de las tuberías utilizadas en equipos generadores de vapor (calderas ha sido reconocida como un grave problema que trae consigo el adelgazamiento de éstas y, por consiguiente, la falla de los equipos. En la última década se han incrementado las investigaciones que involucran recubrimientos protectores que ayudan de alguna manera a prolongar la vida útil de estos equipos. Esta investigación determinó el comportamiento de los recubrimientos NiCrAlY y NiCrFeNbMoTiAl depositados por proyección térmica asistida por plasma (APS sobre la aleación SA213 – T22 (2¼Cr – 1Mo, en un ambiente corrosivo de 80%V2O5–20%K2SO4 a 800°C. Los valores de la cinética de corrosión fueron determinados mediante resistencia a la polarización lineal (RPL y espectroscopia de impedancia electroquímica (EIE. Los resultados obtenidos muestran una menor cinética de corrosión en el recubrimiento NiCrFeNbMoTiAl que la presentada por el recubrimiento NiCrAlY, corroborado por Microscopia Electrónica de Barrido (MEB.

  1. Effect of NiCrAlY Content on Mechanical and Dielectric Properties of NiCrAlY/Al2O3 Composite Coatings%NiCrAlY含量对NiCrAlY/Al2O3涂层机械性能及介电性能的影响

    武志红; 周万城; 罗发; 朱冬梅


    采用大气等离子喷涂技术,以镍基合金(NiCrAlY合金)粉为吸收剂、氧化铝(Al2O3)为基体,制备出NiCrAlY/Al2O3(NA)复合涂层.分析了复合涂层的相组成及显微结构,研究了 NiCrAlY含量变化对复合涂层的机械性能及介电性能的影响.结果表明:喷涂后的涂层中出现了刚玉、铬刚玉等非金属相及唯一的金属相Ni.随着NiCrAlY含量的增加,复合涂层的抗弯强度、断裂韧性逐渐增强;在8.2~12.4 GHz频率范围内,涂层的介电常数实部与虚部值都随着NiCrAlY含量的变化而明显变化,且在NiCrAlY含量为25%时达到最高值,这主要与喷涂过程中分离出金属Ni的含量、冷却后的形状及分布状态有关.%NiCrAlY/Al2O3 (NA) composite coatings were fabricated by a plasma spraying method with nickel-based (NiCrAlY) par-tides as an absorber and A12O3 as a matrix. The phase composition and microstructure of these coatings were characterized by X-ray diffraction and scanning electron microscopy, respectively. The mechanical and dielectric properties of the NA composite coatings with different NiCrAlY contents were investigated. The results indicate that the non-metallic phases (i.e., corundum and chromium corundum) and the metal phase nickel generate in the composite coatings. The bending resistance and fracture toughness all increased with increasing NiCrAlY content. The real part and the imaginary part of permittivity both changed in the frequency range of 8.2-12A GHz, and they reached the maximum values at NiCrAlY content of 25% mainly due to various amounts, solidified shapes and distributions of nickel in the composite coatings.


    Y.X.Lu; W.X.Chen; R.Eadie


    The high temperature corrosion resistance of Ni-25.gCr-13.5Al-1.2Y-0.6Si and Ni-10.2Co-12.4 Cr-16.0A l-0.5 Y-0.2Hf alloys was assessed in sulfidation/oxidation environments.In the environment with a sulfur partial pressure of 1Pa.and an oxygen partial pressure of 10-19Pa,both these alloys exhibited three distinct stages in the weight gain-time curve when tested at 700℃.In the initial stage,selective sulfidation of Cr suppressed the formation of the other metal sulfides,resulting in lower weight gains.In the transient stage,breakdown and cracking of Cr sulfides and insufficient concentration of Cr at the outer zone led to the rapid formation of Ni sulfides and a rapid increase in weight.In the steady-state stage,corrosion was controlled by the diffusion of anions and/or cations,which led to a parabolic rate law.



    Проанализированы экспериментальные данные о влиянии режимов облучения сильноточными импульсными электронными пучками (СИЭП) на адгезию защитного покрытия NiCrAlY на лопатках из сплава ЖС26НК. Показано, что сильноточный импульсный электронный пучок микросекундной длительности является высокоэффективным инструментом для контроля адгезии жаростойких покрытий на поверхности монокристаллических лопаток из жаропрочных сплавов. Применение СИЭП позволяет на стадии модификации физико-химич...

  4. Oxidation behavior of nickel-chromium-aluminum-yttrium - Magnesium oxide and nickel-chromium-aluminum-yttrium - zirconate type of cermets

    Zaplatynsky, I.


    The 1100 and 1200 C cyclic oxidation resistance of dense Ni-Cr-Al-Y - MgO, Ni-Cr-Al-Y - CaZrO3, Ni-Cr-Al-Y - SrZrO3, Ni-Cr-Al-Y - MgZro3 cermets and a 70 percent dense Ni-Cr-Al-Y developmental material was determined. The cermets contained 60 and 50 volume percent of Ni-Cr-Al-Y which formed a matrix with the oxide particles imbedded in it. The cermets containing MgO were superior to cermets based on zirconates and to the porous Ni-Cr-Al-Y material.

  5. Erosion-corrosion of as-plasma-sprayed and laser-remelted NiCrAlY bond coats in working conditions of a coal-fired boiler

    Sidhu, B.S.; Prakash, S. [College of Engineering & Technology, Bathinda (India). Dept. of Mechanical Engineering


    Ni-22Cr-10Al-1Y plasma spray coating has been formulated on boiler tube steels. namely, low-carbon steel ASTM SA210-Grade A1. 1Cr-0.5Mo steel ASTM SA213-T-11, and 2.25Cr-1Mo steel ASTM SA213-T-22. The coated steels also have been laser-remelted using a Nd:YAG laser. The degradation behavior of as-sprayed and laser-remelted coatings have been evaluated in actual conditions in a coal-fired boiler for 1,000 h at 755{sup o}C. The laser remelting has been found to be effective to increase the degradation resistance of plasma-sprayed boiler steels. ASTM SA213-T-22-coated and laser-remelted steel has proved to be most effective in resistance to degrading species.

  6. Process of Electrospark Deposition of Gun Steel with a NiCrAlY Electrode%炮钢表面电火花沉积NiCrAlY的工艺研究

    陈瑞峰; 鲍雪; 赵博远; 刘丽; 杨彦卿




    M.H.Li; X.F.Sun; Z.Y.Zhang; H.R.Guan; W.Y.Hu; Z.Q.Hu


    A bond coat for thermal barrier coating (TBC), NiCrAlY coating, is subjected to vac-uum heat treatment in order to remove internal stress before ceramic top coat is de-posited. The effect of vacuum heat treatment on the oxidation behavior of the sputteredNiCrAlY coating has been investigated. The as-sputtered NiCrAlY coating consists ofγ-Ni and β-NiAl phases. After vacuum heat treatment, the sputtered NiCrAlY coatingmainly consists of γ-Ni3Al, β-NiAl, γ-Ni, and trace of α-Al2O3 phases. The isother-mal oxidation of sputtered NiCrAlY coating with and without vacuum heat treatmenthas been performed at 1000C. It is shown that α-Al2O3 formed during vacuum heattreatment acts as nuclei for the formation of α-Al2O3, and the protective α-Al2O3scale is formed more rapidly on the vacuum heat treated NiCrAlY coating than thatformed on the untreated coating. Also the α-Al2O3 scale has a better adherence to thevacuum heat treated NiCrAlY coating. Therefore the vacuum heat treatment improvesthe oxidation resistance of sputtered NiCrAlY coating.

  8. Microstructure and properties of sputtered thermal barrier coatings

    Yang Gao; Lun Xie; Feng Pan; Mengcheng Chen


    A 3 kW radio frequency (RF) magnetron-sputtering unit was used to produce zirconia ceramic coatings on hollow turbine blades and vanes, which had been deposited a NiCrAlY bond coat layer by cathodic arc deposition. The NiCrAlY coating surface was shot-peened, and the residual stress in the bond coat layer and the effects of heat treatment on the residual stress are presented.After shot peening porosities and microgaps disappear in the NiCrAlY bond coat, the whole depth profile is residual compressive stress. Coarseness tests show that the roughness value (Rz) decreases from 16.4 to 3.3 μm. The microstructure and phase composition of the coatings were investigated using electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The results show that the NiCrAlY bond coat is composed of γ' and Cr phases, and the Al2O3 scales are formed near the interface between the ZrO2 ceramic layer and the NiCrAlY bond coat. No degradation occurred to RF sputtered ceramic coatings after oxidating at 1150℃ for 100 h,heating at 1150℃ for 5 min and then air-cooling for 500 thermal cycles.

  9. Friction and Wear Behavior of Two NiCrA1Y Coatings at Room Temperature%两种NiCrAlY涂层的室温摩擦磨损性能

    张健; 郭策安; 张罡; 郝士明


    The friction and wear properties of a sputtered NiCrAlY coating and an electrospark deposited (ESD) NiCrAlY on CrNi3MoVA steel substrate coating were investigated at room temperature. The results show that the friction coefficient of the two coatings is lower than that of the substrate during stable wearing course. The electrospark deposited NiCrAlY coating has a significant antifriction effect because its friction coefficient value is much lower than the sputtered one. The wear mechanism of the sputtered NiCrAlY coating could be mainly characterised by adhesive wear while the dominant wear mechanism for electrospark deposited NiCrAlY coating is micro-abrasive wear.%分别测试在CrNi3MoVA钢表面溅射NiCrAlY涂层和电火花沉积NiCrAlY涂层的室温摩擦磨损性能,研究了磨损机制.结果表明:在稳定磨损阶段,两种涂层的摩擦系数均低于基体,其中电火花沉积层的摩擦系数最小,具有显著的减摩效果.溅射涂层的磨损机制主要是粘着磨损,而电火花沉积层的磨损机制主要是微切削磨料磨损.

  10. A study of the oxide dispersion and recrystallization in NiCrAl prepared from preoxidized powder

    Glasgow, T. K.


    The SAP technique of dispersion strengthening (formation of an oxide dispersion by preoxidation of metal powders) was applied to atomized powder of the alloy Ni-17Cr-5Al-0.2 Y. SAP-NiCrAl was worked by extrusion and rod rolling at 1205 C and by swaging at 760 C. A variety of annealing treatments were applied after working to determine the recrystallization response. NiCrAlY, similarly prepared from atomized powder, but without a preoxidation treatment, was examined for comparison. The SAP-NiCrAl of this study exhibited oxide particle size and spacing much larger than that usually observed in oxide dispersion strengthened alloys; nonetheless, it was possible to achieve abnormal (secondary) recrystallization in the SAP-NiCrAl as has been reported for other oxide dispersion strengthened alloys. In contrast, unoxidized NiCrAlY exhibited only primary recrystallization.

  11. Development of Oxidation Resistant Coatings on GRCop-84 Substrates by Cold Spray Process

    Karthikeyan, J.


    GRCop-84, a Cu-CR-Nb alloy, has been developed for rocket engine liner applications. For maximum life additional oxidation protection is required to prevent blanching. NiCrAlY was identified as a suitable coating, and efforts were initiated to develop suitable coating techniques. Cold spray is one technique under consideration. Efforts at ASB Industries to produce dense, adherent coatings are detailed. The work culminated in the production of samples for testing at NASA Glenn Research Center.

  12. Vibration Analysis of Commercial Thermal Barrier Coatings


    different thermal barrier coatings, magnesium aluminate spinel and yttria stabilized zirconia; the confirmation that sweep rate does not cause data...coatings which have been extensively researched are discussed in this study: magnesium aluminate spinel (Blackwell, 2004; Ivancic, 2003; Reed, 2007...Reed, 2007). Objective In this study, the elastic modulus and loss factor will be evaluated for magnesium aluminate spinel with a NiCrAlY bond

  13. Corrosion behavior of plasma-sprayed coatings on a Ni-base superalloy in Na2SO4-60 Pct V2O5 environment at 900 °C

    Singh, Harpreet; Puri, D.; Prakash, S.


    The shrouded plasma spray process was used to deposit NiCrAlY, Ni-20Cr, Ni3Al, and Stellite-6 metallic coatings on a Ni-based superalloy (62Ni-23Cr-1.48Al-0.80Mn-0.37Si-0.10Cu-0.025C-bal Fe). NiCrAlY was used as a bond coat in all cases. Hot corrosion studies were conducted on uncoated as well as plasma-spray-coated superalloy specimens after exposure to molten salt at 900 °C under cyclic conditions. The thermogravimetric technique was used to establish the kinetics of corrosion. X-ray diffraction (XRD), scanning electron microscopy/energy-dispersive X-ray analysis (SEM/EDAX) and electron-probe microanalysis techniques were used to analyze the corrosion products. The uncoated superalloy suffered accelerated corrosion in the form of intense spalling of the scale. The NiCrAlY coated specimen showed a minimum weight gain, whereas the Stellite-6 indicated a maximum weight gain among the coatings studied. All the coatings were found to be successful in developing resistance against hot corrosion, which may be attributed to the formation of oxides, and spinels of nickel, aluminum, chromium, or cobalt.

  14. Microstructural features and properties of plasma sprayed YPSZ/NiCrAlY thermal barrier coating (TBC)

    孙大谦; 王文权; 宣兆志; 宫文彪


    The plasma sprayed thermal barrier coating (TBC) consists of NiCrAlY bond coating and yttria partially stabilized zirconia (YPSZ) top coating. NiCrAlY coating mainly contains Ni solid solution with face centered cubic lattice, Al2O3 oxides and pores. The most obvious feature of YPSZ coating with tetragonal zirconia is a lot of vertical microcracks in this coating. The thermal insulation capability of the TBC increased with an increase in YPSZ coating thickness, the temperature drop across the TBC increasing from 60℃ to 92℃ with increasing YPSZ coating thickness with increasing YPSZ coating thickness and cracks initiated mainly in original vertical microcrack tips of the YPSZ coating and propagated not only along YPSZ coating / NiCrAlY coating interface but also through into two stages: transient oxidation stage with rapid oxidation rate and steady oxidation stage with slow oxidation. Their transition time was favorable to increase YPSZ coating toughness and to decrease the pores and oxides of the TBC system for improving thermal shock resistance and oxidation resistance of the TBC.

  15. Vacuum plasma spray coating

    Holmes, Richard R.; Mckechnie, Timothy N.


    Currently, protective plasma spray coatings are applied to space shuttle main engine turbine blades of high-performance nickel alloys by an air plasma spray process. Originally, a ceramic coating of yttria-stabilized zirconia (ZrO2.12Y2O3) was applied for thermal protection, but was removed because of severe spalling. In vacuum plasma spray coating, plasma coatings of nickel-chromium-aluminum-yttrium (NiCrAlY) are applied in a reduced atmosphere of argon/helium. These enhanced coatings showed no spalling after 40 MSFC burner rig thermal shock cycles between 927 C (1700 F) and -253 C (-423 F), while current coatings spalled during 5 to 25 test cycles. Subsequently, a process was developed for applying a durable thermal barrier coating of ZrO2.8Y2O3 to the turbine blades of first-stage high-pressure fuel turbopumps utilizing the enhanced NiCrAlY bond-coating process. NiCrAlY bond coating is applied first, with ZrO2.8Y2O3 added sequentially in increasing amounts until a thermal barrier coating is obtained. The enchanced thermal barrier coating has successfully passed 40 burner rig thermal shock cycles.

  16. Microscale characterization of metallic coatings for a high strength high conductivity copper alloy

    Jain, Piyush

    NiCrAlY overlay coatings are being considered by NASA's Glenn Research Center to prevent blanching and reduce thermo-mechanical fatigue of rocket engine combustion chamber liners made of GRCop-84 (Cu-8%Cr-4%Nb) for reusable launch vehicles (RLVs). However, their successful application depends upon their integrity to the GRCop-84 during multiple firings of rocket engines. This study focuses on determining the adhesion of NiCrAlY coatings and their microstructural stability on GRCop-84 as a function of thermal cycling. Specimens were prepared by depositing NiCrAlY top coat on GRCop-84 by vacuum plasma spaying with a thin layer of Cu-26Cr as a bond coat. A thermal cycling rig was built to thermally cycle the NiCrAlY/Cu-26Cr/GRCop-84 specimens from RT to 600°C in an argon environment, with 10 minutes hold at 600°C, and 4 minutes hold at RT. Samples were cut from the coupons in as-received condition (AR), after 100 thermal cycles (TC-100), and after 300 thermal cycles (TC-300) for characterization. A newly developed interfacial microsample testing technique was employed to determine the adhesion of the coatings on GRCop-84, where bowtie shaped microsamples having interfaces normal to the tensile axis were tested. Interfacial microsamples of NiCrAlY/Cu-26Cr/GRCop-84 in all the conditions (AR, TC-100, and TC-300) failed cohesively in the substrate at a UTS of 380+/-5 MPa and their interfaces remained intact. The microstructural characterization revealed that microstructure of the NiCrAlY/Cu-26Cr/GRCop-84 specimens does not degrade as a function of thermal cycling. Constitutive properties of NiCrAlY, Cu-26Cr, and GRCop-84 were measured by testing monolithic samples and were used to build the finite element model (FEM) of the interfacial microsamples. The FE model analyzed the local stress-strain in the interfacial microsamples during the testing and confirmed the strength of the interfaces to be higher than 380+/-5 MPa. Depleted zones, devoid of Cr2Nb particles, were

  17. Evaluation of Performance and Emission characteristics of Turbocharged Diesel Engine with Mullite as Thermal Barrier Coating

    P. N. Shrirao; A. N. Pawar


    Tests were performed on a single cylinder, four stroke, direct injection, diesel engine whose piston crown, cylinder head and valves were coated with a 0.5 mm thickness of 3Al2O3 .2SiO2 (mullite) (Al2O3= 60%, SiO2= 40%) over a 150 μm thickness of NiCrAlY bond coat. Tests were carried out on standard engine (uncoated) and low heatrejection (LHR) engine with and without turbocharger. This paper is intended to emphasis on energy balance and emission characteristic for standard engine (uncoated) ...

  18. TBCs for better engine efficiency. [thermal barrier coatings

    Brindley, William J.; Miller, Robert A.


    State-of-the-art thermal barrier coatings (TBCs) developed for aircraft engines can achieve both hot-section component operating temperature reductions and superior oxidation resistance. Such TBCs typically consist of two layers: a metallic, often NiCrAlY 'bond' inner layer in contact with the superalloy structural component, and an outer, insulating ceramic layer. A ceramic frequently used in this role due to its high durability is plasma-sprayed ZrO2, partially stabilized with 6-8 wt pct Y2O3. TBCs can also be useful in nonaircraft gas turbines, which frequently use highly contaminated fuels.

  19. Some adhesion/cohesion characteristics of plasma-sprayed ZrO2-Y2O3 under tensile loading

    Mullen, Robert L.; Vlcek, Brian L.; Hendricks, Robert C.; Mcdonald, Glen


    A set of 12.7 mm diameter stainless steel tubes were coated with ceramic and expanded. The bond cast was 0.08 to 0.13 mm NiCrAlY with 0.38 mm of ZrO2-8Y2O3 ceramic. Upon pressurization, the tube substrate yielded and overstressed the coatings in tension. The coatings cracked (i.e., they failed) but did not come off the tube. These results demonstrate that tensile failure of plasma-sprayed coatings is not catastrophic as is compressive failure, which leads to spallation.

  20. Developing Corrosion Prevention Coating Solutions for the Canadian SCWR Concept

    Huang, Xiao


    The development of coating materials and processes was carried out with the objective to reduce material degradation in supercritical water. Based on the test results of bulk coating alloys (FeCrAlY and NiCrAl), two coating processes, plasma spray of dense NiCrAlY and pack aluminizing, have been developed to apply coatings to candidate stainless steels and Ni-based alloys. The SCW test results and microstructure characterization of both coating alloys and coated candidate alloys are presented in this short paper.

  1. Effects of yttrium, aluminum and chromium concentrations in bond coatings on the performance of zirconia-yttria thermal barriers

    Stecura, S.


    A cyclic furnace study was conducted on thermal barrier systems to evaluate the effects of yttrium, chromium and aluminum in nickel-base alloy bond coatings and the effect of bond coating thickness on yttria-stabilized zirconia thermal barrier coating life. Without yttrium in the bond coatings, the zirconia coatings failed very rapidly. Increasing chromium and aluminum in the Ni-Cr-Al-Y bond coatings increased total coating life. This effect was not as great as that due to yttrium. Increased bond coat thickness was also found to increase life.


    H. Jamali


    Full Text Available Nanostructured scandia, yttria doped zirconia (SYSZ, 7wt. % yttria stabilized zirconia (7YSZ and 15YSZ thermal barrier coatings (TBCs were produced by plasma spraying on nickel-based superalloy substrates with NiCrAlY as the bond coat. The thermal shock behavior of the three as-sprayed TBCs at 1000 °C was investigated. The results indicated that the thermal cycling lifetime of SYSZ and 7YSZ TBCs was longer than the 15YSZ TBCs due to the lower thermal mismatch stress between the ceramic layer and the metallic layer at high temperature and higher amount of tetragonal phase.

  3. Advanced ceramic coating development for industrial/utility gas turbines

    Vogan, J. W.; Stetson, A. R.


    A program was conducted with the objective of developing advanced thermal barrier coating (TBC) systems. Coating application was by plasma spray. Duplex, triplex and graded coatings were tested. Coating systems incorporated both NiCrAly and CoCrAly bond coats. Four ceramic overlays were tested: ZrO2.82O3; CaO.TiO2; 2CaO.SiO2; and MgO.Al2O3. The best overall results were obtained with a CaO.TiO2 coating applied to a NiCrAly bond coat. This coating was less sensitive than the ZrO2.8Y2O3 coating to process variables and part geometry. Testing with fuels contaminated with compounds containing sulfur, phosphorus and alkali metals showed the zirconia coatings were destabilized. The calcium titanate coatings were not affected by these contaminants. However, when fuels were used containing 50 ppm of vanadium and 150 ppm of magnesium, heavy deposits were formed on the test specimens and combustor components that required frequent cleaning of the test rig. During the program Mars engine first-stage turbine blades were coated and installed for an engine cyclic endurance run with the zirconia, calcium titanate, and calcium silicate coatings. Heavy spalling developed with the calcium silicate system. The zirconia and calcium titanate systems survived the full test duration. It was concluded that these two TBC's showed potential for application in gas turbines.

  4. Development of a CuNiCrAl Bond Coat for Thermal Barrier Coatings in Rocket Combustion Chambers

    Fiedler, Torben; Rösler, Joachim; Bäker, Martin


    The lifetime of rocket combustion chambers can be increased by applying thermal barrier coatings. The standard coating systems usually used in gas turbines or aero engines will fail at the bond coat/substrate interface due to the chemical difference as well as the different thermal expansion between the copper liner and the applied NiCrAlY bond coat. A new bond coat alloy for rocket engine applications was designed previously with a chemical composition and coefficient of thermal expansion more similar to the copper substrate. Since a comparable material has not been applied by thermal spraying before, coating tests have to be carried out. In this work, the new Ni-30%Cu-6%Al-5%Cr bond coat alloy is applied via high velocity oxygen fuel spraying. In a first step, the influence of different coating parameters on, e.g., porosity, amount of unmolten particles, and coating roughness is investigated and a suitable parameter set for further studies is chosen. In a second step, copper substrates are coated with the chosen parameters to test the feasibility of the process. The high-temperature behavior and adhesion is tested with laser cycling experiments. The new coatings showed good adhesion even at temperatures beyond the maximum test temperatures of the NiCrAlY bond coat in previous studies.

  5. Effect of magnesium oxide content on oxidation behavior of some superalloy-base cermets

    Zaplatynsky, I.


    The effect of increasing magnesium oxide (MgO) content on the cyclic oxidation resistance of hot-pressed cermets of MgO in NiCrAlY, MgO in Hoskins-875, MgO in Inconel-702, and MgO in Hastelloy-X was investigated. The cermets with magnesium oxide levels of 5, 10, 20, and 40 vol percent were examined. The cyclic oxidation behavior of these cermets at 1100 and 1200 C in still air was determined by a thermogravimetric method supplemented by X-ray diffraction analysis and light and electron microscopy. In all instances, MgO prevented grain growth in the metallic phase. No evidence of oxidation along interphase boundaries was detected. Cermets of MgO in NiCrAlY and MgO in Hoskins-875 were superior to cermets of MgO in Inconel-702 and MgO in Hastelloy-X. Their oxidation resistance was degraded only when the MgO content was 40 vol percent. The oxidation behavior of MgO-in-Inconel-702 powder cermets containing 5- and 10-vol percent MgO was approximately similar to that of pure Inconel-702 compacts. The 20- and 40-vol percent MgO content reduced the oxidation resistance of MgO-in-Inconel-702 powder cermets relative to that of pure Inconel-702.

  6. Vacuum Plasma Spray (VPS) Material Applications for Thruster Components

    Elam, Sandra; Holmes, Richard; Hickman, Robert


    A variety of vacuum plasma spray (VPS) material systems have been successfully applied to injector and thrust chamber components. VPS offers a versatile fabrication process with relatively low costs to produce near net shape parts. The materials available with VPS increase operating margins and improve component life by providing superior thermal and oxidation protection in specific engine environments. Functional gradient materials (FGM) formed with VPS allow thrust chamber liners to be fabricated with GRCop-84 (an alloy of copper, chrome, and niobium) and a protective layer of NiCrAlY on the hot wall. A variety of thrust chamber liner designs have been fabricated to demonstrate the versatility of the process. Hot-fire test results have confined the improved durability and high temperature performance of the material systems for thrust chamber liners. Similar FGM s have been applied to provide superior thermal protection on injector faceplates with NiCrAlY and zirconia coatings. The durability of the applied materials has been demonstrated with hot-fire cycle testing on injector faceplates in high temperature environments. The material systems can benefit the components used in booster and main engine propulsion systems. More recent VPS efforts are focused on producing rhenium based material systems for high temperature applications to benefit in-space engines like reaction control system (RCS) thrusters.

  7. Formation and behavior of thermal barrier coatings on nickel-base superalloys

    高阳; 解仑; 曾飞


    Plasma-sprayed thermal barrier coatings (TBCs) have been used to extend the life of combustors. Electron beam physical vapor deposited (EB-PVD) ceramic coating has been developed for more demanding rotating as well as stationary turbine components. Here 3 kW RF magnetron sputtering equipment was used to gain zirconia ceramic coatings on hollow turbine blades and vanes, which had been deposited NiCrAlY by cathodic arc deposition.NiCrAlY coating surface was treated by shot peening; the effects of shot peening on the residual stress are presented. The results show that RF sputtered TBCs are columnar ceramics, strongly bonded to metal substrates. NiCrAlY bond coat is made of β, γ′ and Cr phases, ZrO2 ceramic layer consists of t' and c phases. No degradation occursto RF ceramic coatings after 100 h high temperature oxidation at 1 150 ℃ and 500 thermal cycles at 1 150 ℃ for 2 min,air-cooling.

  8. Effects of bond coat and top coat (including nano zones) structures on morphology and type of formed transient stage oxides at pre-heat treated nano NiCrAlY/nano ZrO2-8%Y2O3 interface during oxidation

    Mohammadreza Daroonparvar


    Bond coat geometry is able to significantly influence thermally grown oxide (TGO) layer formation and growth in thermal barrier coating systems at the onset of oxidation. Moreover, nanostructured yttria stabilized zirconia coating with three model struc-ture (including nano zones) could reduce oxygen partial pressure to the formation pressure of continues alumina oxide scale which was able to protect the substrate from extra oxidation and corrosion. Thus, nano NiCrAlY/nano YSZ and normal NiCrAlY/nano YSZ coatings were prepared by air plasma spray method and then evaluated by high temperature oxidation test at 1000 °C for 160 h. As-sprayed samples were also pre-oxidized at 1000 °C for 48 h and then examined by electrochemical polarization test. The corrosion rate of the pre-oxidized nano NiCrAlY/nano YSZ coating was estimated to be the lowest compared to that of the other samples. It might be related to the formation of continues alumina layer on the nano NiCrAlY at the onset of oxidation. This continuous layer could reduce the penetration of the aggressive solution into the NiCrAlY coating and acted as a protective layer (with the lowest an-odic current density). This layer also lessened TGO growth rate at the stages II and III of the growth.

  9. Comparison of molybdenizing and NiCrA1Y coating on Ti and Ti-6A1-4V

    PENG Xiaomin; XIA Changqing; LIU Yingying; ZHANG Zhigao


    Two surface treatments, molybdenizing and depositing NiCrAIY coating, were applied to improve the microhardness and the oxidation re-sistance of titanium and Ti-6Al-4V. Coupons were analyzed using optical microscopy (OM), scanning electron microscopy (SEM) with X-ray energy dispersive spectrometer (EDS), and X-ray diffraction (XRD). Vickers hardness and isothermal oxidation tests were carded out to evaluate the effects of these two surface treatments on the microhardness and oxidation resistance of the substrates. The post vacuum heat treatment of the NiCrAlY coating and the molybdenizing parameters were also discussed. It is found that molybdenizing can obviously in-crease the surface hardness of titanium due to the formation of β,α", and α' phases in the diffusion layer. As γ' phase is formed after vacuum heat treatment, the NiCrAIY coating is effective in improving the surface hardness of Ti-6Al-4V. The NiCrAlY coating can obviously de-crease the oxidation rate of Ti-6Al-4V at 700-900℃, which can be attributed to the formation of Al2O3 and Cr2O3 mixed scale during the oxidation.

  10. Young's Moduli of Cold and Vacuum Plasma Sprayed Metallic Coatings

    Raj, S. V.; Pawlik, R.; Loewenthal, W.


    Monolithic metallic copper alloy and NiCrAlY coatings were fabricated by either the cold spray (CS) or the vacuum plasma spray (VPS) deposition processes. Dynamic elastic modulus property measurements were conducted on these monolithic coating specimens between 300 K and 1273 K using the impulse excitation technique. The Young's moduli decreased almost linearly with increasing temperature at all temperatures except in the case of the CS Cu-23%Cr-5%Al and VPS NiCrAlY, where deviations from linearity were observed above a critical temperature. It was observed that the Young's moduli for VPS Cu-8%Cr were larger than literature data compiled for Cu. The addition of 1%Al to Cu- 8%Cr significantly increased its Young's modulus by 12 to 17% presumably due to a solid solution effect. Comparisons of the Young s moduli data between two different measurements on the same CS Cu- 23%Cr-5%Al specimen revealed that the values measured in the first run were about 10% higher than those in the second run. It is suggested that this observation is due to annealing of the initial cold work microstructure resulting form the cold spray deposition process.

  11. Thermal cycling, oxidation behaviour and mechanical properties of graded and duplex PSZ TBC coatings

    Musil, J. [SKODA, Plzen (Czech Republic); Alaya, M.; Oberacker, R. [Univ. of Karlsruhe (Germany)


    Plasma sprayed duplex and graded ZrO{sub 2} thermal barrier coatings (TBCs) on an Inconel 617 substrate with a NiCrAlY bond coat were investigated and compared with regard to their thermal cycling, oxidation behaviour and mechanical properties. On the basis of FE - calculations the stress distribution within thermally cycled coating systems was analyzed. The calculations show that the graded coating structure relaxes considerably the stresses resulting from the internal constraint due to thermal expansion difference between both metallic and ceramic materials and hence must lead to a better thermal cycling behaviour of the graded TBC systems. Mechanical tests confirm it. However, taking into account their poor oxidation behaviour, the lifetime of duplex TBC systems which are under steady-state thermal load conditions is much higher than that of graded ones.

  12. Thermal barrier coatings for heat engine components

    Levine, S. R.; Miller, R. A.; Hodge, P. E.


    A comprehensive NASA-Lewis program of coating development for aircraft gas turbine blades and vanes is presented. Improved ceramic layer compositions are investigated, along the MCrAlY bond films and the methods of uniform deposition of the coatings; the thermomechanical and fuel impurity tolerance limits of the coatings are being studied. Materials include the ZrO2-Y2O3/NiCrAlY system; the effects of the bond coat and zirconia composition on coating life and Mach 1 burner rig test results are discussed. It is concluded that Diesel engines can also utilize thermal barrier coatings; they have been used successfully on piston crowns and exhaust valves of shipboard engines to combat lower grade fuel combustion corrosion.

  13. Friction and wear of sintered fiber-metal abradable seal materials

    Bill, R. C.; Shiembob, L. T.


    Three abradable gas path seal material systems based on a sintered NiCrAlY fibermetal structure were evaluated under a range of wear conditions representative of those likely to be encountered in various knife-edge seal (labyrinth or shrouded turbine) applications. Conditions leading to undesirable wear of the rotating knife were identified and a model was proposed based on thermal effects arising under different rub conditions. It was found, and predicted by the model, that low incursion (plunge) rates tended to promote smearing of the low density sintered material with consequent wear to the knife-edge. Tradeoffs benefits between baseline 19 percent dense material, a similar material of increased density, and a self lubricating coating applied to the 19 percent material were identified based on relative rub tolerance and erosion resistance.

  14. Improving thermal barrier coatings by laser remelting.

    Múnez, C J; Gómez-García, J; Sevillano, F; Poza, P; Utrilla, M V


    Thermal barrier coatings are extensively used to protect metallic components in applications where the operating conditions include aggressive environment at high temperatures. These coatings are usually processed by thermal spraying techniques and the resulting microstructure includes thin and large splats, associated with the deposition of individual droplets, with porosity between splats. This porosity reduces the oxidation and corrosion resistance favouring the entrance of aggressive species during service. To overcome this limitation, the top coat could be modified by laser glazing reducing surface roughness and sealing open porosity. ZrO2(Y2O3) top coat and NiCrAlY bond coating were air plasma sprayed onto an Inconel 600 Ni base alloy. The top coat was laser remelted and a densified ceramic layer was induced in the top surface of the ceramic coating. This layer inhibited the ingress of aggressive species and delayed bond coat oxidation.

  15. High-temperature thermo-mechanical behavior of functionally graded materials produced by plasma sprayed coating: Experimental and modeling results

    Choi, Kang Hyun; Kim, Hyun-Su; Park, Chang Hyun; Kim, Gon-Ho; Baik, Kyoung Ho; Lee, Sung Ho; Kim, Taehyung; Kim, Hyoung Seop


    Thermal barrier coatings are widely used in aerospace industries to protect exterior surfaces from harsh environments. In this study, functionally graded materials (FGMs) were investigated with the aim to optimize their high temperature resistance and strength characteristics. NiCrAlY bond coats were deposited on Inconel-617 superalloy substrate specimens by the low vacuum plasma spraying technique. Functionally graded Ni-yttria-stabilized zirconia (YSZ) coatings with gradually varying amounts of YSZ (20%-100%) were fabricated from composite powders by vacuum plasma spraying. Heat shield performance tests were conducted using a high- temperature plasma torch. The temperature distributions were measured using thermocouples at the interfaces of the FGM layers during the tests. A model for predicting the temperature at the bond coating-substrate interface was established. The temperature distributions simulated using the finite element method agreed well with the experimental results.

  16. Thermal barrier coating on high temperature industrial gas turbine engines

    Carlson, N.; Stoner, B. L.


    The thermal barrier coating used was a yttria stabilized zirconia material with a NiCrAlY undercoat, and the base engine used to establish improvements was the P&WA FT50A-4 industrial gas turbine engine. The design benefits of thermal barrier coatings include simplified cooling schemes and the use of conventional alloys in the engine hot section. Cooling flow reductions and improved heating rates achieved with thermal barrier coating result in improved performance. Economic benefits include reduced power production costs and reduced fuel consumption. Over the 30,000 hour life of the thermal barrier coated parts, fuel savings equivalent to $5 million are projected and specific power (megawatts/mass of engine airflow) improvements on the order of 13% are estimated.

  17. Continued development of abradable gas path seals. [for gas turbine engines

    Shiembob, L. T.


    Major program objectives were the continued development of NiCrAlY feltmetal and honeycomb systems for knife edge seal applications in the 1144 to 1366 K temperature range, and to initiate abradable seal material evaluation for blade tip seal applications in the 1366 to 1589 K temperature range. Larger fiber size, higher density feltmetal showed greatly improved erosion resistance with a slight reduction in abradability compared to the baseline feltmetal. Pack aluminide coating of the honeycomb extended the oxidation resistance and slightly improved the abradability of this material. Evaluation through selected abradability, erosion and oxidation testing, and pertinent metallography led to selection of a plasma sprayed yttria stabilized zirconia (ZrO2)/CoCrAlY layered system as the system with the most potential to meet the 1589 K requirement for blade tip seals. This system demonstrated structural integrity, erosion resistance, and some degree of abradability.

  18. Mechanical degradation of coating systems in high-temperature cyclic oxidation

    Pennefather, RC


    Full Text Available Alloy Thickness CPOA CPO B CPO c CPO D CPO E CPO F CPO G CPO F + TCC Cl9 LPPS CoNiCrAlY IN738 172 LPPS CoCrAlY IN738 152 LPPS NiCoCrAlY + Si IN738 166 LPPS NiCoCrAlY + Si,Ta IN738 134 LPPS NiCrAlY + Si IN738 166 LPPS NiCoCrAlY IN738 125... and number of cycles to failure of the coated test samples Designation CPO A CPO B CPO c CPO D CPO E CPO F CPO G CPOF + TCC Cl9 Number Average &phase of cycles thickness content Rumpling Cycles to failure 500 168 0 17.4 745 500 146 0 24.1 500...

  19. Fireside Corrosion Behavior of HVOF and Plasma-Sprayed Coatings in Advanced Coal/Biomass Co-Fired Power Plants

    Hussain, T.; Dudziak, T.; Simms, N. J.; Nicholls, J. R.


    This article presents a systematic evaluation of coatings for advanced fossil fuel plants and addresses fireside corrosion in coal/biomass-derived flue gases. A selection of four candidate coatings: alloy 625, NiCr, FeCrAl and NiCrAlY were deposited onto superheaters/reheaters alloy (T91) using high-velocity oxy-fuel (HVOF) and plasma spraying. A series of laboratory-based fireside corrosion exposures were carried out on these coated samples in furnaces under controlled atmosphere for 1000 h at 650 °C. The tests were carried out using the "deposit-recoat" test method to simulate the environment that was anticipated from air-firing 20 wt.% cereal co-product mixed with a UK coal. The exposures were carried out using a deposit containing Na2SO4, K2SO4, and Fe2O3 to produce alkali-iron tri-sulfates, which had been identified as the principal cause of fireside corrosion on superheaters/reheaters in pulverized coal-fired power plants. The exposed samples were examined in an ESEM with EDX analysis to characterize the damage. Pre- and post-exposure dimensional metrologies were used to quantify the metal damage in terms of metal loss distributions. The thermally sprayed coatings suffered significant corrosion attack from a combination of aggressive combustion gases and deposit mixtures. In this study, all the four plasma-sprayed coatings studied performed better than the HVOF-sprayed coatings because of a lower level of porosity. NiCr was found to be the best performing coating material with a median metal loss of ~87 μm (HVOF sprayed) and ~13 μm (plasma sprayed). In general, the median metal damage for coatings had the following ranking (in the descending order: most to the least damage): NiCrAlY > alloy 625 > FeCrAl > NiCr.

  20. Cyclic oxidation behavior of plasma surface chromising coating on titanium alloy Ti-6Al-4V

    Wei Dongbo, E-mail: [College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211100 (China); Zhang Pingze; Yao Zhengjun; Zhou Jintang; Wei Xiangfei; Zhou Peng [College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211100 (China)


    Highlights: Black-Right-Pointing-Pointer A chromising coating in gradient distribution was obtained on Ti-6Al-4V titanium alloy. Black-Right-Pointing-Pointer The cyclic oxidation behavior of chromising coating was studied at 650-850 Degree-Sign C. Black-Right-Pointing-Pointer The Ti-Cr mutual diffusion layer changed into the Ti(Cr, Al){sub 2} laves phase layer, which prevented the inward diffusion of oxygen. Black-Right-Pointing-Pointer A multi-layers structure of Cr{sub 2}O{sub 3}, TiO{sub 2} and Al{sub 2}O{sub 3} formed during oxidation. Black-Right-Pointing-Pointer Ti, Al diffused toward the oxide-gas interface, Cr diffused predominantly outward. - Abstract: The cyclic oxidation behavior of plasma surface chromising coating on titanium alloy (Ti-6Al-4V) was researched in air at 650 Degree-Sign C, 750 Degree-Sign C and 850 Degree-Sign C. A NiCrAlY coating was prepared by multi-arc ion plating as a comparison. The surface morphologies, microstructures and phases of both coatings before and after oxidation were investigated using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffractometry (XRD). The results show that the chromising coating consisted of an outer layer of loose Cr deposition, an intermediate layer of compact Cr deposition and an inner Ti-Cr mutual diffusion layer. The multilayer oxide scales formed in the oxidation process, which has the better cyclic oxidation resistance compared with NiCrAlY thermal barrier coating. However, the brittleness of Ti(Cr, Al){sub 2} laves phase resulted in spallation of oxide scales at 750 Degree-Sign C and 850 Degree-Sign C.

  1. Thermal Expansion of Vacuum Plasma Sprayed Coatings

    Raj, S V.; Palczer, A. R.


    Metallic Cu-8%Cr, Cu-26%Cr, Cu-8%Cr-1%Al, NiAl and NiCrAlY monolithic coatings were fabricated by vacuum plasma spray deposition processes for thermal expansion property measurements between 293 and 1223 K. The corrected thermal expansion, (DL/L(sub 0) varies with the absolute temperature, T, as (DL/L(sub 0) = A(T - 293)(sup 3) + BIT - 293)(sup 2) + C(T - 293) + D, where, A, B, C and D are thermal, regression constants. Excellent reproducibility was observed for all of the coatings except for data obtained on the Cu-8%Cr and Cu-26%Cr coatings in the first heat-up cycle, which deviated from those determined in the subsequent cycles. This deviation is attributed to the presence of residual stresses developed during the spraying of the coatings, which are relieved after the first heat-up cycle. In the cases of Cu-8%Cr and NiAl, the thermal expansion data were observed to be reproducible for three specimens. The linear expansion data for Cu-8% Cr and Cu-26%Cr agree extremely well with rule of mixture (ROM) predictions. Comparison of the data for the Cu-8%Cr coating with literature data for Cr and Cu revealed that the thermal expansion behavior of this alloy is determined by the Cu-rich matrix. The data for NiAl and NiCrAlY are in excellent agreement with published results irrespective of composition and the methods used for processing the materials. The implications of these results on coating GRCop-84 copper alloy combustor liners for reusable launch vehicles are discussed.

  2. Influences of MCrAlY coatings on oxidation resistance of single crystal superalloy DD98M and their inter-diffusion behaviors

    Shi, Long [School of Materials and Metallurgy, Northeastern University, Shenyang 110819 (China); Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Xin, Li, E-mail: [Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Wang, Xinyue; Wang, Xiaolan; Wei, Hua; Zhu, Shenglong; Wang, Fuhui [Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)


    Oxidation and interdiffusion behaviors of Ni-based single crystal superalloy DD98M with nominal compositions Ni–5.0Co–6.0Cr–6.3Al–6.0W–2.0Mo–6.0Ta–1.0Ti (in wt.%) and two types of MCrAlY coatings at 1000 °C and 1050 °C were investigated. Complex oxides formed on the surface of DD98M alloy when oxidized at 1000 °C and 1050 °C, which stratified, cracked and spalled. The faceted-like AlN and the particle-like and strip-like TiN formed in the alloy. The application of the NiCrAlY and NiCoCrAlYHfSi coatings greatly improved the oxidation resistance of DD98M alloy. After 500 h oxidation, α-Al{sub 2}O{sub 3} was still the dominate phase in the oxide scales formed on the coated specimens. The adhesion of the oxide scale on the NiCoCrAlYHfSi coating was much better than that on the NiCrAlY coating. Interdiffusion occurred between the coatings and the substrate, which led to the formation of the IDZ and SRZ. The IDZ of the NiCrAlY coated specimen was composed of γ phase and Al- and Ta-rich γ′ phase. The γ′ phase in the IDZ accommodated most of the inward diffusing aluminum, so the SRZ formation was suppressed when oxidized at 1050 °C. However the formation of SRZ with μ-TCP still occurred when oxidized at 1000 °C probably due to the low solubility and slow diffusion rate of the alloying elements at lower temperature. The IDZ of the NiCoCrAlYHfSi coated specimen was a single γ phase. A large amount of μ-TCP precipitated in the SRZ of the NiCoCrAlYHfSi coated specimen when oxidized at 1000 °C and 1050 °C. It can be concluded coating composition has a significant effect on the development of the IDZ and SRZ. Thermal exposure temperature also has influences on the formation of the SRZ. The mechanism of SRZ formation and TCP precipitation are discussed. - Graphical abstract: The TEM micrograph of the IDZ and SRZ of the NiCoCrAlYHfSi-coated specimen oxidized at 1050 °C for 100 h and the respective diffraction patterns of the needle-like and the

  3. Evaluation of Performance and Emission characteristics of Turbocharged Diesel Engine with Mullite as Thermal Barrier Coating

    P. N. Shrirao


    Full Text Available Tests were performed on a single cylinder, four stroke, direct injection, diesel engine whose piston crown, cylinder head and valves were coated with a 0.5 mm thickness of 3Al2O3 .2SiO2 (mullite (Al2O3= 60%, SiO2= 40% over a 150 μm thickness of NiCrAlY bond coat. Tests were carried out on standard engine (uncoated and low heatrejection (LHR engine with and without turbocharger. This paper is intended to emphasis on energy balance and emission characteristic for standard engine (uncoated and low heat rejection (LHR engine with and without turbocharger. Tests were carried out at different engine load and engine speed conditions for standard and low heatrejection engine with and without turbocharger. The results showed that there was 2.18% decreasing on specific fuel consumption value of low heat rejection (LHR engine with turbocharger compared to standard engine at full load. There was as much as 12% increasing on exhaust gas temperature of LHR engine with turbocharger compared tostandard engine at full load. There was as much as 20.64% increasing on NOx emission of exhaust gas, 22.05% decreasing on CO emission of exhaust gas and 28.20% decreasing on HC emission of exhaust gas of LHR engine with turbocharger compared to standard engine at full load.

  4. Influence of Water Vapor on the Isothermal Oxidation Behavior of Thermal Barrier Coatings

    Chungen ZHOU; Jingsheng YU; Shengkai GONG; Huibin XU


    The oxidation of specimens with thermal barrier coating (TBC) consisted of nickel-base superalloy, low-pressure plasma sprayed Ni-28Cr-6Al-0.4Y (wt pct) bond coating and electron beam physical vapor deposited 7.5 wt pct yttria stabilized zirconia (YSZ) top coating was studied at 1050℃ respectively in flows of O2, and mixture of O2 and 5%H2O under atmospheric pressure. The thermal barrier coating has relatively low oxidation rate at 1050℃ in pure O2. Oxidation rate of thermal barrier coating in the atmosphere of O2 and 5%H2O is increased The oxidation kinetics obeys almost linear law after long exposure time in the presence of 5% water vapor. Oxide formed along the interface between bond coat and top coat after oxidation at 1050℃ in pure O2 consisted of Al2O3, whereas interfacial scales formed after oxidation at 1050℃ in a mixture of O2 and 5%H2O were mainly composed of Ni(Al,Cr)2O4,NiO and Al2O3. It is suggested that the effect of water vapor on the oxidation of the NiCrAlY coating may be attributed to the increase in Ni and Cr ions transport in the oxides.

  5. Fabrication of Pt/ITO Thin-Film Thermocouple on Metal Substrates%金属基Pt/ITO薄膜热电偶的制备

    赵文雅; 蒋洪川; 陈寅之; 张万里; 刘兴钊; 彭少龙; 唐磊


    采用多层膜结构制备了金属基Pt/ITO薄膜热电偶,薄膜热电偶由Ni基合金基片、NiCrAlY过渡层、热生长Al2O3层、Al2O3绝缘层、Pt/ITO功能层和Al2O3保护层构成.静态标定结果表明:样品的平均塞贝克系数为107.45 μV/℃.测试温度可达到1000℃.时效处理可以有效提高薄膜热电偶的输出热电势.%The Pt/ITO thin-film thermocouples with multilayer structure are fabricated on metal substrates. The thin-film thermocouple is composed of Ni-base alloy substrate, NiCrAlY buffer layer, thermal growth A12O3 layer, A12O3 insulating layer, Pt/ITO function layer and A12O3 protective layer. The results of the static calibration of the sample show that the average Seebeck coefficient is about 107.45 μV /℃. The test temperature can be up to 1000℃. The thermoelectric power of the sample can be effectively improved by aging treatment.

  6. Design of a Nickel-Based Bond-Coat Alloy for Thermal Barrier Coatings on Copper Substrates

    Torben Fiedler


    Full Text Available To increase the lifetime of rocket combustion chambers, thermal barrier coatings (TBC may be applied on the copper chamber wall. Since standard TBC systems used in gas turbines are not suitable for rocket-engine application and fail at the interface between the substrate and bond coat, a new bond-coat material has to be designed. This bond-coat material has to be chemically compatible to the copper substrate to improve the adhesion and needs a coefficient of thermal expansion close to that of copper to reduce thermal stresses. One approach to achieve this is to modify the standard NiCrAlY alloy used in gas turbines by adding copper. In this work, the influence of copper on the microstructure of NiCrAlY-alloys is investigated with thermodynamical calculations, optical microscopy, SEM, EDX and calorimetry. Adding copper leads to the formation of a significant amount of \\(\\beta\\ and \\(\\alpha\\ Reducing the aluminum and chromium content leads furthermore to a two-phase fcc microstructure.

  7. Comparative Study of Performance and Combustion Characteristics of Conventional and Low Heat Rejection (Mullite Coated) Diesel Engines

    Patond, S. B.; Chaple, S. A.; Shrirao, P. N.; Shaikh, P. I.


    Tests were performed on a single cylinder, four stroke, direct injection, diesel engine whose piston crown, cylinder head and valves were coated with a 0.5 mm thickness of 3Al2O3·2SiO2 (mullite) (Al2O3 = 60%, SiO2 = 40%) over a 150 μm thickness of NiCrAlY bond coat. The working conditions for the conventional engine (without coating) and LHR (mullite coated) engine were kept exactly same to ensure a comparison between the two configurations of the engine. This paper is intended to emphasis on performance and combustion characteristics of conventional and LHR (Mullite coated) diesel engines under identical conditions. Tests were carried out at same operational constraints i.e. air-fuel ratio and engine speed conditions for both conventional engine (without coating) and LHR (mullite coated) engines. The results showed that, there was as much as 1.8 % increasing on brake power for LHR (mullite coated) engine compared to conventional engine (without coating) at full load The average decrease in brake specific fuel consumption in the LHR engine compared with the conventional engine was 1.76 % for full engine load. However, there was increasing on cylinder gas pressure and net heat release rate for LHR engine compared to conventional engine. Also the results revealed that, there was as much as 22% increasing on exhaust gas temperature for LHR engine compared to conventional engine at full engine load.

  8. Thermal Barrier Coatings on Copper Substrates for Rocket Applications

    Schloesser, Jana; Fedorova, Tatiana; Bäker, Martin; Rösler, Joachim

    Currently a new generation of relaunchable space transportation system using liquid hydrogen/ liquid oxygen rocket engines is under development. The inner combustion chamber is exposed to extreme thermal loads and environmental attack during starts. To prevent failure of the cooling channels, a thermal barrier coating to provide thermal and oxidation protection could be applied. Thermal barrier coatings are state of the art for gas turbines and this concept should be transferred to copper substrates in rocket engine applications. The thermomechanical loading conditions are quite different from the gas turbine applications as heat fluxes and temperature gradients are much higher while overall service time is much shorter. As a start for optimization of a suitable coating, a material system known for gas turbines is employed. In this work a thermal barrier coating system is applied by atmospheric plasma spraying to the copper-based high strength alloy Cu-1%Cr-0.3%Zr. The bond coat consists of a NiCrAlY alloy, while partially stabilized zirconia is used as a top coat. Spraying parameter optimization for the new substrate is described. The reached coating system is tested in thermal cycling experiments, where no failure of the coating could be detected. In oxidation experiments good environmental protection of the coating is shown.

  9. Hot corrosion behavior of nanostructured Gd2O3 doped YSZ thermal barrier coating in presence of Na2SO4 + V2O5 molten salts

    Yixiong Wang


    Full Text Available Nickel-based superalloy DZ125 was first sprayed with a NiCrAlY bond coat and followed with a nanostructured 2 mol% Gd2O3−4.5 mol% Y2O3-ZrO2 (2GdYSZ topcoat using air plasma spraying (APS. Hot corrosion behavior of the as-sprayed thermal barrier coatings (TBCs were investigated in the presence of 50 wt% Na2SO4 + 50 wt% V2O5 as the corrosive molten salt at 900 °C for 100 h. The analysis results indicate that Gd doped YVO4 and m-ZrO2 crystals were formed as corrosion products due to the reaction of the corrosive salts with stabilizers (Y2O3, Gd2O3 of zirconia. Cross-section morphology shows that a thin layer called TGO was formed at the bond coat/topcoat interface. After hot corrosion test, the proportion of m-ZrO2 phase in nanostructured 2GdYSZ coating is lower than that of nano-YSZ coating. The result reveals that nanostructured 2GdYSZ coating exhibits a better hot corrosion resistance than nano-YSZ coating.

  10. Corrosion behavior of duplex coatings

    K. Raghu Ram Mohan Reddy


    Full Text Available The titanium alloys are used in defense, aerospace, automobile, chemical plants and biomedical applications due to their very high strength and lightweight properties. However, corrosion is a life-limiting factor when Ti alloys are exposed to different chemical environments at high temperatures. In the present paper, duplex NiCrAlY/WC–Co coating is coated onto Ti6Al4V substrate to investigate the corrosion behavior of both coated samples and the substrate. The duplex coating was performed with NiCrAlY as the intermediate coat of 200 μm thickness deposited by HVOF process and WC–Co ceramic top coat with varying thicknesses of 250 μm, 350 μm and 450 μm deposited by DS process. Potentiodynamic polarization tests were employed to investigate the corrosion performance of duplex coated samples and substrate in Ringer’s solution at 37 °C and pH value was set to 5.7. Finally the results reveal that 350 μm thick coated samples showed highest corrosion resistance compared to 250 μm thick samples as well as bare substrate. However, the 450 μm thick coated sample showed poor corrosion resistance compared to the substrate. The scale formed on the samples upon corrosion was characterized by using SEM analysis to understand the degree of corrosion behavior.

  11. In-flight behavior of dissimilar co-injected particles in the spraying of metal-ceramic functionally gradient materials

    Fincke, J.R.; Swank, W.D.; Haggard, D.C. [Idaho National Engineering Lab., Idaho Falls, ID (United States)


    In the spraying of functionally gradient coatings the particle ensemble delivered to the substrate can vary from a relatively low melting point metallic particle to a significantly higher melting point ceramic particle. At various stages in the spray process the particle ensemble can be either predominantly metallic, ceramic, or an intermediate combination. For co-injected particles the mixtures do not behave as a simple linear superposition of the spray patterns of the individual particle types. The particle temperature, velocity, size distributions, and pattern characteristics of the resulting spray fields is examined for all ceramic particle sprays (ZrO{sub 2}), all metallic particle sprays (NiCrAlY), and for a 1:1 mixture. The major particle-particle interaction occurs in the injector itself and results in a modified spray pattern which is different from that of either material sprayed alone. The particle velocity distributions generally exhibit a bimodal nature which is dependent on the size and density of the injected particles.

  12. Coatings for directional eutectics

    Rairden, J. R.; Jackson, M. R.


    Coatings developed to provide oxidation protection for the directionally-solidified eutectic alloy NiTaC-B (4.4 weight percent Cr) were evaluated. Of seven Co-, Fe- and Ni-base coatings that were initially investigated, best resistance to cyclic oxidation was demonstrated by duplex coatings fabricated by depositing a layer of NiCrAl(Y) by vacuum evaporation from an electron beam source followed by deposition of an Al overlayer using the pack cementation process. It was found that addition of carbon to the coating alloy substantially eliminated the problem of fiber denudation in TaC-type eutectic alloys. Burner rig cycled NiTaC-B samples coated with Ni-20Cr-5Al-0.1C-0.1Y+Al and rupture-tested at 1100 deg C performed as well as or better than uncoated, vacuum cycled and air-tested NiTaC-13; however, a slight degradation with respect to uncoated material was noted in air-stress rupture tests at 870 deg C for both cycled and uncycled samples.

  13. Influence of Different Interfacial Conditions on Bond Strength of Plasma - Sprayed Tungsten Coatings

    Song, S.X. [Research Center on Fusion Materials (RCFM), University of Science and Technology Beijing (USTB), 10008 3 Beijing (China); Zhou, Z.; Ge, C. [Lab. of Special Ceramic and P/M, University of Science and Technology, 100083 Beijing (China)


    Full text of publication follows: How to improve the interfacial performance and obtain high bond strength is a common problem in plasma-sprayed W coatings onto Cu substrates as plasma-facing components (PFC). This phenomenon results from the high interfacial residual stress state created by different thermal expansion coefficients, melting points and elastic modulus between W and Cu during the spraying processes. In this paper, tungsten coatings were deposited onto the oxygen free copper by plasma spraying. Various interlayers were designed to relieve the residual stress between W coatings and Cu substrates. These interlayers included NiCrAl, NiAl, NiCrAlY, W(50 %) Cu (50%) and functionally graded bonding coatings NiCrAl/AlCu, W/Cu and so on. SEM, EDS and XRD were employed to investigate the microstructure, photographs and compositions of the interfacial layers. Finite element coupled heat transfer and elastic-plastic thermal stress analysis using finite element analysis (FEA) were utilized to simulate the residual stress generation during the depositing process. The residual stresses were also calculated using this method to explain the variations of the interfacial characteristics with the various interlayers. In addition, tensile tests in conjunction with finite element analysis (FEA) were also performed to better understand the influence of both material selection and component distribution on bonding strength between the coatings and the substrates. As a result, a predicted coating system with the possibility of reducing the residual stress level was also proposed. (authors)

  14. Investigation on plasma-sprayed ZrO2 thermal barrier coating on nickel alloy substrate

    卢安贤; 常鹰; 蔡小梅


    The thermal barrier coatings with NiCrAlY alloy bonding layer, NiCrAlY-Y2O3 stabilized ZrO2 transition layer and Y2O3 stabilized ZrO2 ceramic layer are prepared on nickel alloy substrates using the plasma spray technique. The relationship among the composition, structure and property of the coatings are investiga-ted by means of optical microscope, scanning electronic microscope and the experiments of thermal shock resistance cycling and high temperature oxidation resistance. The results show that the structure design of introdu-cing a transition layer between Ni alloy substrate and ZrO2 ceramic coating guarantees the high quality and properties of the coatings; ZrO2 coatings doped with a little SiO2 possesses better thermal shock resistance and more excellent hot corrosion resistance as compared with ZrO2 coating materials without SiO2 ;the improvement in performance of ZrO2 coating doped with SiO2 is due to forming more dense coating structure by self- closing effects of the flaws and pores in the ZrO2 coatings.

  15. Corrosion resistance of plasma sprayed NiCrAl + (ZrO2 + Y2O3 ) thermal barrier coating on 18 -8 steel surface

    CHEN Fei; L(U) Tao; DING Hua-dong; ZHOU Hai; LIU Kai


    The corrosion resistance of NiCrAl +(ZrO2 + Y2 O3 )thermal barrier coating, formed with the plasma spraying technique, on the 18 - 8 steel surface was investigated. The phase structure and morphology of the coating were analyzed by means of X-ray diffraction(XRD) and scanning electron microscopy(SEM). The electrochemical corrosion behavior of the coating in 1.0 mol/L H2 SO4 solution was studied by using electrochemical measurement methods. The results show that the gradient plasma spraying coating is composed of the NiCrAlY primer coating and the (ZrO2 + Y2O3 ) top coating, and the coating thickness is 360 μm. The microhardness of coating reaches 1 100 HV. The corrosion resistance of the plasma sprayed coating of the 18 - 8 steel surface is about 5 times as great as that of the original pattern. The corrosion resistance of the coating is enhanced notably.

  16. Residual Stresses in Thermal Barrier Coatings for a Cu-8Cr-4Nb Substrate System

    Ghosn, Louis J.; Raj, Sai V.


    Analytical calculations were conducted to determine the thermal stresses developed in a coated copper-based alloy, Cu-8%(at.%)Cr-4%Nb (designated as GRCop-84), after plasma spraying and during heat-up in a simulated rocket engine environment. Finite element analyses were conducted for two coating systems consisting of a metallic top coat, a pure copper bond coat and the GRCop-84. The through thickness temperature variations were determined as a function of coating thickness for two metallic coatings, a Ni-17%(wt%)Cr-6%Al-0.5%Y alloy and a Ni-50%(at.%)Al alloy. The residual stresses after low-pressure plasma spraying of the NiCrAlY and NiAl coatings on GRCop-84 substrate were also evaluated. These analyses took into consideration a 50.8 mm copper bond coat and the effects of an interface coating roughness. The through the thickness thermal stresses developed in coated liners were also calculated after 15 minutes of exposure in a rocket environment with and without an interfacial roughness.

  17. Plasma Spray-Physical Vapor Deposition (PS-PVD) of Ceramics for Protective Coatings

    Harder, Bryan J.; Zhu, Dongming


    In order to generate advanced multilayer thermal and environmental protection systems, a new deposition process is needed to bridge the gap between conventional plasma spray, which produces relatively thick coatings on the order of 125-250 microns, and conventional vapor phase processes such as electron beam physical vapor deposition (EB-PVD) which are limited by relatively slow deposition rates, high investment costs, and coating material vapor pressure requirements. The use of Plasma Spray - Physical Vapor Deposition (PS-PVD) processing fills this gap and allows thin (coatings of less than 100 microns to be generated with the flexibility to tailor microstructures by changing processing conditions. Coatings of yttria-stabilized zirconia (YSZ) were applied to NiCrAlY bond coated superalloy substrates using the PS-PVD coater at NASA Glenn Research Center. A design-of-experiments was used to examine the effects of process variables (Ar/He plasma gas ratio, the total plasma gas flow, and the torch current) on chamber pressure and torch power. Coating thickness, phase and microstructure were evaluated for each set of deposition conditions. Low chamber pressures and high power were shown to increase coating thickness and create columnar-like structures. Likewise, high chamber pressures and low power had lower growth rates, but resulted in flatter, more homogeneous layers

  18. Effect of heat treatment on corrosion behavior of duplex coatings

    K. Raghu Ram Mohan Reddy


    Full Text Available In the present paper, duplex WC-Co/NiCrAlY coating is coated onto Ti6Al4V substrate and vacuum heat treatment is employed to investigate the corrosion behavior of heat treated samples as well as Ti6Al4V substrate for comparison. In this duplex coating system, High Velocity Oxy Fuel (HVOF process is used to deposit NiCrAlY interlayer with a constant thickness of 200 μm and WC-Co ceramic top layer with varying thickness of 250 μm, 350 μm and 450 μm deposited by Detonation Spray (DS process. Different heat treatment temperatures (600–1150 °C were employed for the coated samples to study the microstructure and the effect on corrosion resistance of the duplex coatings. Potentiodynamic polarization tests were carried to investigate the corrosion performance of duplex coated heat treated samples and the substrate in Ringer’s solution at 37 °C and prepared the pH to 5.7. The microstructure upon corrosion after heat treatment was characterized by SEM analysis to understand the corrosion behavior. The results disclosed that at all heat treatment temperatures, all the coated samples exhibited better corrosion resistance than the base substrate. However, during 950 °C and 1150 °C heat treatment temperatures, it was observed highest corrosion potential than 600 °C and 800 °C. The 350 μm thickness, coated sample exhibited highest corrosion resistance compared to other two coated samples and the substrate at all heat treatment temperatures.

  19. Hot Corrosion of Nickel-Base Alloys in Biomass-Derived Fuel Simulated Atmosphere

    Leyens, C.; Pint, B.A.; Wright, I.G.


    Biomass fuels are considered to be a promising renewable source of energy. However, impurities present in the fuel may cause corrosion problems with the materials used in the hot sections of gas turbines and only limited data are available so far. As part of the Advanced Turbine Systems Program initiated by the U.S. Department of Energy, the present study provides initial data on the hot corrosion resistance of different nickel-base alloys against sodium sulfate-induced corrosion as a baseline, and against salt compositions simulating biomass-derived fuel deposits. Single crystal nickel-superalloy Rene N5, a cast NiCrAlY alloy, a NiCoCrAlY alloy representing industrially used overlay compositions, and a model {beta}NiAl+Hf alloy were tested in 1h thermal cycles at 950 C with different salt coatings deposited onto the surfaces. Whereas the NiCoCrAlY alloy exhibited reasonable resistance against pure sodium sulfate deposits, the NiCrAiY alloy and Rene N5 were attacked severely. Although considered to be an ideal alumina former in air and oxygen at higher temperatures, {beta}NiAl+Hf also suffered from rapid corrosion attack at 950 C when coated with sodium sulfate. The higher level of potassium present in biomass fuels compared with conventional fuels was addressed by testing a NiCoCrAlY alloy coated with salts of different K/Na atomic ratios. Starting at zero Na, the corrosion rate increased considerably when sodium was added to potassium sulfate. In an intermediate region the corrosion rate was initially insensitive to the K/Na ratio but accelerated when very Na-rich compositions were deposited. The key driver for corrosion of the NiCoCrAlY alloy was sodium sulfate rather than potassium sulfate, and no simple additive or synergistic effect of combining sodium and potassium was found.

  20. Microstructural characterization of thermal barrier coating on Inconel 617 after high temperature oxidation

    Mohammadreza Daroonparvar


    Full Text Available A turbine blade was protected against high temperature corrosion and oxidation by thermal barrier coatings (TBCsusing atmospheric plasma spraying technique (APS on a Ni-based superalloy (Inconel 617. The coatings (NiCr6AlY/ YSZ and NiCr10AlY/YSZ consist of laminar structure with substantial interconnected porosity transferred oxygen from Yittria stabilized Zirconia (YSZ layer toward the bond coat (NiCrAlY. Hence, a thermally grown oxide layer (TGO was formed on the metallic bond coat and internal oxidation of the bond coat occurred during oxidation. The TBC systems were oxidized in a normal electrically heated furnace at 1150 °C for 18, 22, 26, 32 and 40h.Microstructural characterization of coatings demonstrated that the growth of the TGO layer on the nickel alloy with 6wt. % Al is more rapid than TGO with 10wt. % Al. In addition, many micro-cracks were observed at the interface of NiCr6AlY/YSZ. X-ray diffraction analysis (XRD showed the existence of detrimental oxides such as NiCr2O4, NiCrO3 and NiCrO4 in the bond coat containing 6wt. % Al, accompanied by rapid volume expansion causing the destruction of TBC. In contrast, in the bond coat with 10wt. % Al, NiO, Al2O3and Cr2O3 oxides were formed while very low volume expansion occurred. The oxygen could not penetrate into the TGO layer of bond coat with 10 wt. % Al during high temperature oxidation and the detrimental oxides were not extensively formed within the bond coat as more oxygen was needed. The YSZ with higher Al content showed higher oxidation resistance.

  1. Influence of the Thermal Barrier Coatings Design on the Oxidation Behavior

    B.Saeedi; A.Sabour; A.Ebadi; A.M.Khoddami


    The properties of two different types of thermal barrier coatings (TBCs) were compared to improve the surface characteristics on high temperature components. These TBCs consisted of a duplex TBC and a five-layered functionally graded TBC. NiCrAlY bond coats were deposited on a number of Inconel-738LC specimens using high velocity oxy-fuel spraying (HVOF) technique. For duplex coating, a group of these specimens were coated with yttria stabilized zirconia (YSZ) using plasma spray technique. Functionally graded NiCrAlY/YSZ coatings were fabricated by plasma spray using co-injection of the two different powders in a single plasma torch. The amount of zirconia in functionally graded coatings were gradually increased from 30 to 100 vol. pct. Microstructural changes, thermally grown oxide (TGO) layer growth and damage initiation of the coatings were investigated as a function of isothermal oxidation test at 970℃. As a complementary test, the performance of the fabricated coatings by the optimum processing conditions was evaluated as a function of intense thermal cycling test at 1100℃. Also the strength of the adhesive coatings of the substrate was also measured. Microstructural characterization was analyzed by scanning electron microscopy (SEM) and optical microscopy whereas phase analysis and chemical composition changes of the coatings and oxides formed during the tests were studied by XRD (X-ray diffraction) and EDS (energy dispersive spectrometer). The results showed that microstructure and compositions gradually varied in the functionally graded coatings. By comparison of duplex and functionally graded TBCs oxidation behavior (duplex failure after 1700 h and funcitionally graded TECs failure after 2000 h), thermal shock test and adhesion strength of the coatings, the functionally graded TBC had better performance and more durability.

  2. Thermal barrier ZrO2 - Y2O3 obtained by plasma spraying method and laser melting

    K. Kobylańska–Szkaradek


    Full Text Available Purpose: Purpose: The aim of the paper is to determine the influence of laser melting upon the selected physical properties of ZrO2 - Y2O3 ceramic coatings deposited by APS (Air Plasma Spraying method on super-alloys which function as TBC (Thermal Barriers Coatings.Design/methodology/approach: Laser melting which helps eliminate pores and other structural defects of coatings should contribute to the improvement of their density and durability as thermal barriers. In order to prove the assumptions made in the paper, coatings featuring varied porosity and deposited upon the nickel base super-alloys surface with the initially sprayed NiCrAlY bond coat have been subjected to laser melting and then their structure, thermal conductivity and thermal life prediction in the conditions of cyclic temperature changes from 20 to 1200ºC have been examined.Findings: It has been revealed that the coatings featuring low porosity laser melted on part of their thickness and heated up to about 700ºC demonstrate the highest thermal life prediction under the conditions mentioned and at slightly lower thermal conductivity.Research limitations/implications: Low wettability of metal by ceramic which results from various surface tensions of these materials is the cause of their lower adhesion to the substrate during laser melting all through their thickness. It is so because delaminations occur between phases the boundary and cracks.Practical implications: The worked out conditions of laser melting might be used in the process of creation of TBC which feature high working durability upon super-alloy elements.Originality/value: It has been found that homogenization of chemical composition of coatings occurs during laser melting leading to the reduction of ZrO2 - Y2O3 phase with monoclinic lattice participation as well as to the reduction of structural stresses which accompany this phase transformation during heating and cooling process.

  3. Problems for determining the thermal conductivity of TBCs by laser-flash method

    O. Altun


    Full Text Available Purpose: The purpose of this paper was to investigate the parameters which effect the results of determining the thermal conductivity of thermal barrier coatings (TBCs by laser-flash method.Design/methodology/approach: The air plasma-spray (APS technique was used to deposition of two- and three-layered samples. Two-layered samples were composed of metal substrate (321 stainless steel, and ceramic top coat (8YSZ. Three-layered samples were composed of metal substrate (321 stainless steel, bond coat (NiCrAlY and top coat (8YSZ. Thermal diffusivity of each layer have been measured in the temperature range from room temperature (RT to 900ºC by laser-flash method. The thermal conductivity was calculated with respect to density, specific heat and diffusivity of the materials.Findings: Obtained results show that the specific heat, density and thicknesses of metal substrate, bond coat and top coat play important role in the thermal conductivity measurement.Research limitations/implications: To obtain the correct results in laser-flash technique thickness, density, and cp of the materials are needed to be measured accurately and surface smoothness of samples should be provided sensitively. Errors in these parameters cause high deviations in measurements.Practical implications: It has been aimed offer an insight into the experimental determination of thermal conductivity of layered TBC system which are used in high technologic applications.Originality/value: Laser-flash method is the most widely used experimental technique to determine the thermal conductivity of APS TBCs at high temperatures. The research contributes to better understanding and recognition the importance of sample preparation in laser-flash method.

  4. An Alternative Low-Cost Process for Deposition of MCrAlY Bond Coats for Advanced Syngas/Hydrogen Turbine Applications

    Zhang, Ying [Tennessee Technological Univ., Cookeville, TN (United States)


    The objective of this project was to develop and optimize MCrAlY bond coats for syngas/hydrogen turbine applications using a low-cost electrolytic codeposition process. Prealloyed CrAlY-based powders were codeposited into a metal matrix of Ni, Co or Ni-Co during the electroplating process, and a subsequent post-deposition heat treatment converted it to the MCrAlY coating. Our research efforts focused on: (1) investigation of the effects of electro-codeposition configuration and parameters on the CrAlY particle incorporation in the NiCo-CrAlY composite coatings; (2) development of the post-deposition heat treating procedure; (3) characterization of coating properties and evaluation of coating oxidation performance; (4) exploration of a sulfurfree electroplating solution; (5) cost analysis of the present electrolytic codeposition process. Different electro-codeposition configurations were investigated, and the rotating barrel system demonstrated the capability of depositing NiCo-CrAlY composite coatings uniformly on the entire specimen surface, with the CrAlY particle incorporation in the range 37-42 vol.%. Post-deposition heat treatment at 1000-1200 °C promoted interdiffusion between the CrAlY particles and the Ni-Co metal matrix, resulting in β/γ’/γ or β/γ’ phases in the heat-treated coatings. The results also indicate that the post-deposition heat treatment should be conducted at temperatures ≤1100 °C to minimize Cr evaporation and outward diffusion of Ti. The electro-codeposited NiCrAlY coatings in general showed lower hardness and surface roughness than thermal spray MCrAlY coatings. Coating oxidation performance was evaluated at 1000-1100 °C in dry and wet air environments. The initial electro-codeposited NiCoCrAlY coatings containing relatively high sulfur did not show good oxidation resistance. After modifications of the coating process, the cleaner NiCoCrAlY coating exhibited good oxidation performance at 1000 °C during the 2,000 1-h cyclic

  5. Effect of double glow plasma surface chromizing on high-temperature oxidation resistance of TC4 titanium alloy%TC4合金双辉等离子渗Cr高温氧化行为

    魏东博; 张平则; 姚正军; 梁文萍; 缪强; 徐重


    Isothermal oxidation behavior of TC4 titanium alloy,which was chromized by the double glow plasma surface alloying technology(DGP),were investigated at 650 ℃,750 ℃ and 850 ℃.The results show that the chromizing layer consists of surface loose layer,compact deposited layer and Ti-Cr mutual diffusion layer.The diffusion layer has better oxidation resistance compared with NiCrAlY thermal barrier coating.The ratio of Cr to Ti content in the diffusion layer exhibits gradient distribution by Cr,Cr1.97Ti1.07 and CrTi4.Under oxidation circumstance,Cr,Ti and Al diffuse outward to form multilayer oxide films,which prevent inward diffusion of oxygen.At 650 ℃,the oxidation films consist of two layers: the external Cr2O3 layer and the internal TiO2 layer.At 750 ℃,a mixed oxide layer containing Cr2O3 and TiO2 is formed beneath the Cr2O3 layer and TiO2 layer,whereby Ti(Cr,Al)2 Laves phase is observed in the Ti-depleted layer.At 850 ℃,a mixed oxide layer containing TiO2,Ti2O3 and Ti3O5 is formed beneath the Cr2O3 layer and Al2O3 layer,whereby Ti(Cr,Al)2 Laves phase and Kirkendall voids are formed in the depletion layer.%研究了双层辉光等离子渗Cr对TC4合金650、750、850℃恒温氧化性能的影响。结果表明:渗Cr后,表面梯度合金层显著提高了TC4合金的高温氧化性能,Ti-Cr互扩散层可有效阻止氧向基体扩散。氧化过程中,Ti、Cr向外扩散形成TiO2/Cr2O3氧化膜,其形态与氧化温度有关。850℃氧化100 h后,渗Cr试样表面形成致密Cr2O3膜,恒温氧化性能优于NiCrAlY热障涂层。

  6. Damage tolerant functionally graded materials for advanced wear and friction applications

    Prchlik, Lubos

    The research work presented in this dissertation focused on processing effects, microstructure development, characterization and performance evaluation of composite and graded coatings used for friction and wear control. The following issues were addressed. (1) Definition of prerequisites for a successful composite and graded coating formation by means of thermal spraying. (2) Improvement of characterization methods available for homogenous thermally sprayed coating and their extension to composite and graded materials. (3) Development of novel characterization methods specifically for FGMs, with a focus on through thickness property measurement by indentation and in-situ curvature techniques. (4) Design of composite materials with improved properties compared to homogenous coatings. (5) Fabrication and performance assessment of FGM with improved wear and impact damage properties. Materials. The materials studied included several material systems relevant to low friction and contact damage tolerant applications: MO-Mo2C, WC-Co cermets as materials commonly used sliding components of industrial machinery and NiCrAlY/8%-Yttria Partially Stabilized Zirconia composites as a potential solution for abradable sections of gas turbines and aircraft engines. In addition, uniform coatings such as molybdenum and Ni5%Al alloy were evaluated as model system to assess the influence of microstructure variation onto the mechanical property and wear response. Methods. The contact response of the materials was investigated through several techniques. These included methods evaluating the relevant intrinsic coating properties such as elastic modulus, residual stress, fracture toughness, scratch resistance and tests measuring the abrasion and friction-sliding behavior. Dry-sand and wet two-body abrasion testing was performed in addition to traditional ball on disc sliding tests. Among all characterization techniques the spherical indentation deserved most attention and enabled to

  7. Degradación de barreras térmicas por sales fundidas

    Utrilla, M. V.


    Full Text Available Thermal barrier coatings (TBC are frequently used to provide thermal insulation to metallic components. The material used in this investigation comprises a ceramic top layer, ZrO2 8Y2O3 (Y-PSZ, and an overlay coating, Ni22Cr10Al1Y, air plasma sprayed on to a nickel base alloy Inconel 600 substrate. Yttria stabilizes the cubic phase zirconia, but it can react with S, V and Na contaminants contained in many low-quality industrial fuels. A decrease in the yttria content promotes the transformation to monoclinic ZrO2. The materials were subjected to an isothermal air furnace test under 40% Na2SO4 - 60% V2O5 mixtures at 800 ºC for 48 and 144h. The degradation of the coating was analyzed by electrochemical impedance spectroscopy (EIS. The microstructure was characterized by enviromental scanning electron microscopy (ESEM, X-ray microanalysis (EDX and x ray diffracction (XRD.

    Las barreras térmicas son sistemas multicapa que se aplican a sustratos metálicos para mejorar su resistencia a la temperatura. El material utilizado en el trabajo es un sustrato base níquel (Inconel 600 con recubrimiento multicapa de NiCrAlY y ZrO2 parcialmente estabilizada con Y2O3 (Y-PSZ depositado por plasma atmosférico. La presencia de contaminantes, como S, V o Na presentes en combustibles de baja calidad, puede dar lugar a reacciones con este óxido estabilizador de la circona (Y2O3, originando una desestabilización estructural de la circona por disminución del contenido en itria. En esta comunicación se ha realizado un estudio sistemático de la degradación del material frente a determinados agentes corrosivos a elevada temperatura. Sobre la superficie de las muestras se añadieron mezclas de 40% Na2SO4-60% V2O5 y se trataron isotérmicamente a 800 ºC durante 48 y 144 horas. Finalmente, se evaluó la modificación de las propiedades por efecto de los agentes agresivos. Mediante la técnica de espectroscopía de impedancia electroquímica (EIS se estimó la

  8. Residual Stresses Modeled in Thermal Barrier Coatings

    Freborg, A. M.; Ferguson, B. L.; Petrus, G. J.; Brindley, W. J.


    Thermal barrier coating (TBC) applications continue to increase as the need for greater engine efficiency in aircraft and land-based gas turbines increases. However, durability and reliability issues limit the benefits that can be derived from TBC's. A thorough understanding of the mechanisms that cause TBC failure is a key to increasing, as well as predicting, TBC durability. Oxidation of the bond coat has been repeatedly identified as one of the major factors affecting the durability of the ceramic top coat during service. However, the mechanisms by which oxidation facilitates TBC failure are poorly understood and require further characterization. In addition, researchers have suspected that other bond coat and top coat factors might influence TBC thermal fatigue life, both separately and through interactions with the mechanism of oxidation. These other factors include the bond coat coefficient of thermal expansion, the bond coat roughness, and the creep behavior of both the ceramic and bond coat layers. Although it is difficult to design an experiment to examine these factors unambiguously, it is possible to design a computer modeling "experiment" to examine the action and interaction of these factors, as well as to determine failure drivers for TBC's. Previous computer models have examined some of these factors separately to determine their effect on coating residual stresses, but none have examined all the factors concurrently. The purpose of this research, which was performed at DCT, Inc., in contract with the NASA Lewis Research Center, was to develop an inclusive finite element model to characterize the effects of oxidation on the residual stresses within the TBC system during thermal cycling as well as to examine the interaction of oxidation with the other factors affecting TBC life. The plasma sprayed, two-layer thermal barrier coating that was modeled incorporated a superalloy substrate, a NiCrAlY bond coat, and a ZrO2-8 wt % Y2O3 ceramic top coat. We

  9. Karakterizacija vakuum plazma naprskane kobalt-nikal-hrom-aluminijum-itrijum prevlake

    Mihailo R. Mrdak


    Full Text Available U ovome radu je analiziran uticaj plazma sprej odstojanja na mikrostrukturu i mehaničke karakteristike Co32Ni21Cr8Al0.5Y prevlaka deponovanih vacuum plazma sprej postupkom (VPS. Mikrostruktura i mehaničke osobine plazma sprej prevlaka su određene interakcijom jona plazme Ar/H2 sa česticama praha pri čemu nastaje prenos brzine i temperature jona na čestice praha. Efekat interakcije je u direktnoj zavisnosti od vremena interakcije jona i čestica praha koji je definisan plazma sprej odstojanjem. Prah je deponovan sa plazma pištoljem F4 sa tri odstojanja substrata 270, 295 i 320 mm. Prevlaka najboljih strukturnih i mahaničkih karakteristika je testirana na oksidaciju u peći za termičku obradu bez zaštitne atmosfere na 11000C u trajanju od 240 sati. Morfologija čestica praha je ispitana na SEM-u. Mikrostruktura slojeva u deponovanom stanju je ispitana tehnikom svetlosne mikroskopije. Prevlaka najboljih mehaničkih karakteristikama je nagrizena  elektrolitički sa 10% oksalne kiseline H2C2O4x2H2O. Analiza mikrostrukture nagrizene prevlake je izvršena na svetlosnom mikroskopu i na SEM-u pre i posle testiranja prevlake na oksidaciju. Mikrostrukturna analiza deponovanih slojevima je urađena u skladu sa standardom Pratt-Whitney. Procena mehaničkih karakteristika slojeva je urađena ispitivanjem mikrotvrdoće metodom HV0.3 i čvrstoće spoja ispitivanjem na zatezanje. Uvod Sistemi prevlaka CoNiCrAlY su razvijeni na osnovu sistema prevlaka NiCrAl, FeCrAlY , NiCrAlY i CoCrAlY (Mrdak, 2010, pp.5-16, (Mrdak, 2012, pp.182-201, ( Driver, 2004, ( Feuerstein, et al., 2008, pp.199-213. CoNiCrAlY su prevlake tipa koje se koriste u različitim aplikacijama gasnih turbina za zaštiti od visoko temperaturne oksidacije i tople korozije. Budući da su osobine i ponašanje prevlaka usko povezane sa mikrostrukturom, neophodno je da se ispitaju strukture prevlaka posle depozicije i oksidacije na povišenim temperaturama (Gudmundsson, Jacobson, 1988, pp.207