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Статті в журналах з теми "Oxidation resistance of Ti-Al intermetallic alloys"
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Lazurenko, Daria V., Mikhail G. Golkovsky, Andreas Stark, Florian Pyczak, Ivan A. Bataev, Alexey A. Ruktuev, Ivan Yu Petrov, and Ilia S. Laptev. "Structure and Properties of Ti-Al-Ta and Ti-Al-Cr Cladding Layers Fabricated on Titanium." Metals 11, no. 7 (July 19, 2021): 1139. http://dx.doi.org/10.3390/met11071139.
Повний текст джерелаАнотація:
Being one of the most high-demand structural materials, titanium has several disadvantages, including low resistance to high-temperature oxidation and wear. The properties of titanium and its alloys can be improved by applying protective intermetallic coatings. In this study, 2 mm thick Ti-Al-Ta and Ti-Al-Cr layers were obtained on titanium workpieces by a non-vacuum electron-beam cladding. The microstructure and phase compositions of the samples were different for various alloying elements. The Cr-containing layer consisted of α2, γ, and B2 phases, while the Ta-containing layer additionally consisted of ω′ phase (P3¯m1). At the same atomic concentrations of aluminum and an alloying element in both layers, the volume fraction of the B2/ω phase in the Ti-41Al-7Ta alloy was significantly lower than in the Ti-41Al-7Cr alloy, and the amount of γ phase was higher. The Ti-41Al-7Cr layer had the highest wear resistance (2.1 times higher than that of titanium). The maximum oxidation resistance (8 times higher compared to titanium) was observed for the Ti-41Al-7Ta layer.
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Savkovs, Konstantins, Margarita Urbaha, and Viktors Feofanovs. "Determining High-Temperature Oxidation Resistance of (TI-Al-X-N) Based Coatings for Titanium Alloys." Solid State Phenomena 320 (June 30, 2021): 66–71. http://dx.doi.org/10.4028/www.scientific.net/ssp.320.66.
Повний текст джерелаАнотація:
Basic titanium alloys are successfully used in modern aviation GTE (gas turbine engine). They are used for parts of a compressor and partly in low pressure part of turbine (intermetallic Ti-Al alloys) due to their high specific strength and at the same time low density, high corrosion resistance but can be used only up to 700 °C. The paper deals with the results of heat resistance testing at 750 °C of Ti-Al-(X)+N based thin ion-plasm multilayers coatings, with different priority of monolayers- intermetallic, conglomerate or nitride for gas turbine engine (GTE) blades from titanium alloys. All coatings showed high resistance during the test, with a maximum efficiency 42.8 of coating with a priority of conglomerate after 30 hours of testing.
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Vojtěch, Dalibor, and Tomáš Popela. "Structure and High-Temperature Oxidation of Ti-Al-Nb and Ti-Al-Ta Intermetallics." Key Engineering Materials 465 (January 2011): 227–30. http://dx.doi.org/10.4028/www.scientific.net/kem.465.227.
Повний текст джерелаАнотація:
Ti-Al based intermetallics are prospective high-temperature materials showing low weight combined with a relatively high strength, high creep resistance and good oxidation resistance at high temperatures. Beside Ti and Al, these materials commonly contain other additives modifying their properties. In the present work, structure and oxidation resistance of two Ti-Al-Nb and Ti-Al-Ta alloys are studied. The alloys are prepared by vacuum arc melting and oxidation is conducted in air at 800-1000°C. It is found that there are significant differences in the structure depending on the ternary additive. There are also differences in oxidation behavior and these differences are discussed in relation to oxidation mechanism.
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Schütze, Michael, and Simone Friedle. "Oxidation Behavior of Intermetallic Titanium Aluminide Alloys." MRS Proceedings 1516 (2012): 77–88. http://dx.doi.org/10.1557/opl.2012.1666.
Повний текст джерелаАнотація:
ABSTRACTAbove 750-800°C oxidation becomes a serious life time issue for the new group of intermetallic light-weight high temperature alloys based on titanium aluminides (TiAl). Fast growing titanium oxide competes with protective alumina as a surface scale in the oxidation reaction by which the formation of a slow-growing protective oxide scale is prevented. The key to the development of alloys with sufficient oxidation resistance is the understanding of the thermodynamic and kinetic situation during the oxidation process. The latter is influenced by the type of alloying elements, the Al- and Ti-activities in the alloy, the oxidation temperature and the environment (e.g. dry or humid air, etc.). This paper provides a comprehensive summary of the oxidation mechanisms and the parameters influencing oxide scale formation. Besides the role of metallic alloying elements, the halogen effect will also be discussed. The paper finishes with recent results concerning the prevention of oxidation-induced room temperature embrittlement of TiAl alloys.
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Sienkiewicz, Judyta, Seiji Kuroda, Hideyuki Murakami, Hiroshi Araki, Maciej Giżyński, and Krzysztof J. Kurzydłowski. "Fabrication and Oxidation Resistance of TiAl Matrix Coatings Reinforced with Silicide Precipitates Produced by Heat Treatment of Warm Sprayed Coatings." Journal of Thermal Spray Technology 27, no. 7 (September 5, 2018): 1165–76. http://dx.doi.org/10.1007/s11666-018-0751-x.
Повний текст джерелаАнотація:
Abstract Ti-Al-based intermetallics are promising candidates as coating materials for thermal protection systems in aerospace vehicles; they can operate just below the temperatures where ceramics are commonly used, and their main advantage is the fact that they are lighter than most other alloys, such as MCrAlY. Therefore, Ti-Al-Si alloy coatings with five compositions were manufactured by spraying pure Ti and Al-12 wt.% Si powders using warm spray process. Two-stage hot pressing at 600 and 1000 °C was applied to the deposits in order to obtain titanium aluminide intermetallic phases. The microstructure, chemical composition, and phase composition of the as-deposited and hot-pressed coatings were investigated using SEM, EDS, and XRD. Applying of hot pressing enabled the formation of dense coatings with porosity around 0.5% and hard Ti5(Si,Al)3 silicide precipitates. It was found that the Ti5(Si,Al)3 silicides existed in two types of morphologies, i.e., as large particles connected together and as small isolated particles dispersed in the matrix. Furthermore, the produced coatings exhibited good isothermal and cyclic oxidation resistance at a temperature of 750 °C for 100 h.
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Batool, Syeda Ammara, Akhlaq Ahmad, Abdul Wadood, Abdul Mateen, and Syed Wilayat Hussain. "Development of Lightweight Aluminum-Titanium Alloys for Aerospace Applications." Key Engineering Materials 778 (September 2018): 22–27. http://dx.doi.org/10.4028/www.scientific.net/kem.778.22.
Повний текст джерелаАнотація:
Aluminum (Al) and Titanium (Ti) based lightweight alloys have been a topic of discussion and research for a few decades now. Resulting alloys with hard intermetallic phases in Al-Ti binary system have good microstructural and mechanical properties including low densities, high specific strength, better resistance against oxidation and corrosion which are highly desirable in aerospace industry. Such an alloy system was studied in our research. Powder metallurgy (PM) was used as processing route because of its economical and easy operation. Samples were prepared using metallic powders of Aluminum (Al) and Titanium (Ti) with varying compositions of 95 at.% Al-Ti, 90 at.% Al-Ti and 88 at.% Al-10 at.% Ti-2 at.% SiC. After compaction, pressureless sintering was carried out at 620°C for several hours in Argon atmosphere followed by annealing resulting in a reasonably dense Al-Ti alloy. Microstructure and phase composition of alloy was analyzed by Scanning electron microscopy (SEM) and Energy dispersive spectroscopy (EDS), respectively. Hardness was evaluated by Vickers micro indentation test. An increase in hardness was observed. Sample containing reinforcement particles (SiC) demonstrated highest value of hardness.
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Fröhlich, Maik, Reinhold Braun та Christoph Leyens. "Ti-Al-Cr Based Coatings for High Temperature Oxidation Protection of γ-TiAl". Materials Science Forum 638-642 (січень 2010): 1306–11. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.1306.
Повний текст джерелаАнотація:
In this study the oxidation resistance of Ti-45Al-8Nb (at.%) alloy coated with quaternary Ti-Al-Cr-X layers (X = Si, Hf, Y, Zr and W) was investigated. The Ti-Al-Cr-Si, Ti-Al-Cr-Hf and Ti-Al-Cr-Y coated specimens were exposed to air at 950°C under cyclic conditions, whereas the samples with Ti-Al-Cr-Zr and Ti-Al-Cr-W coatings were thermally cycled at 1000°C. After the maximum exposure time period of 1000 1h-cycles or failure cross-sections of the samples were examined by means of SEM and EDS to analyse the microstructural evolution. At initial stages of exposure, all intermetallic layers formed a thin alumina layer on top, providing a diffusion barrier to oxygen. But interdiffusion between coating and substrate caused depletion of the Ti(Cr,Al)2 Laves phase in the intermetallic layers, which promoted the formation of alumina, as well as transformation into Ti-rich B2-phase. Coarsening of the latter phase beneath the alumina scale resulted in a higher oxidation resistance compared to that of ternary Ti-Al-Cr coating.
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Donchev, Alexander, Michael Schütze, Andreas Kolitsch, and Rossen Yankov. "Economic Surface Treatment of Ti-Alloys to Improve their Resistance against Environmental High Temperature Attack." Key Engineering Materials 551 (May 2013): 109–13. http://dx.doi.org/10.4028/www.scientific.net/kem.551.109.
Повний текст джерелаАнотація:
High temperature Ti-alloys are usually sophisticated and hence expensive. To allow the use of cheaper alloys at elevated temperatures an economic and easy to apply procedure was developed to improve their high temperature capability. The treatment consists of a combination of Al-enrichment in a shallow surface region plus additional fluorination. The Al-enrichment at elevated temperatures leads to the formation of intermetallic TiAl-phases. These phases improve the oxidation resistance of Ti-alloys but not to a sufficient extent. An additional fluorine treatment of the Al-enriched surface leads to the formation of a protective alumina scale due to the fluorine effect. In this paper results from high temperature exposure tests performed on different Ti-alloys without any treatment and with a combination of Al-treatment plus fluorination are presented. The results are discussed in the view of the use of the optimized Ti-components for several high temperature applications.
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Braun, Reinhold, Klemens Kelm, Arutiun P. Ehiasarian та Papken Eh Hovsepian. "Oxidation Protection of γ-TiAl Alloys by Intermetallic Ti-Al-Cr-Zr Coatings". MRS Proceedings 1516 (2012): 89–94. http://dx.doi.org/10.1557/opl.2012.1562.
Повний текст джерелаАнотація:
ABSTRACTThe oxidation behavior of γ-TiAl specimens coated with an intermetallic Ti-49Al-34Cr-4Zr layer was investigated at 1000°C under cyclic conditions in laboratory air. The 11 μm thick coating was produced using a combined technique of high power impulse magnetron sputtering and unbalanced magnetron sputtering. The as-deposited coating exhibited a dense layered structure and excellent adhesion to the substrate. The Ti-Al-Cr-Zr coating possessed high oxidation resistance associated with the formation of a thin continuous alumina scale for exposure time periods exceeding 1000 cycles of 1 h dwell time at 1000°C. During the high temperature exposure, the coating being amorphous in the as-deposited condition became crystalline exhibiting different polytypes of Ti(Cr,Al)2Laves phases with Ti probably partially substituted by Zr and Nb. Due to alumina formation and interdiffusion the coating was depleted in aluminum and chromium as well as enriched in titanium. After 1000 cycles at 1000°C, the coating consisted of an outer layer of the hexagonal C14 Laves phase and an inner layer of a probably orthorhombic phase whose structure was not yet determined. In both layers, pores and fine precipitates rich in Zr and Y were found.
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Sasaki, Tomohiro, Takahiro Yagi, and Takehiko Watanabe. "Aluminizing of TiAl-Based Alloy Using Thermal Spray Coating." Materials Science Forum 654-656 (June 2010): 1884–87. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.1884.
Повний текст джерелаАнотація:
Aluminizing the surface of a TiAl-based alloy (49.1 at% Al) was carried out by thermally spraying a pure aluminum coating and subsequent diffusion treatment at 1100°C. The influence of the diffusion time for the formation of Ti-Al intermetallic phases in the coating layers and the oxidation resistance of the aluminized TiAl-based alloys were investigated. The layer formed on the outermost surface was comprised of the Al-rich intermetallic T2iAl5 and contained pores. On the other hand, an intermediate layer consisting of TiAl2 and TiAl was formed between the outermost layer and the substrate. The thickness of the outermost layer decreased as the diffusion time increased, while the thickness of the intermediate layer increased. In addition, the coating/substrate interface changed from a wavy to a linear form with the growth of the intermediate layer. The aluminized coating showed good oxidation resistance at 900°C for all diffusion times.
Дисертації з теми "Oxidation resistance of Ti-Al intermetallic alloys"
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OSTROVSKAYA, OXANA. "Oxidation resistance of Ti-Al intermetallic alloys and protection by ceramic coating." Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2705474.
Повний текст джерелаАнотація:
In recent years, TiAl intermetallic alloys been widely used in aircraft and automotive industry. With the aim of improving the mechanical behavior and the oxidation resistance at high temperature of the TiAl alloys firstly designed, new intermetallic alloys of second and third generation have been successively developed.
In this work, the oxidation resistance in air of four intermetallic alloys of second generation (Ti-48Al-2Cr-2Nb) and third generation ( Ti-48Al-2Nb-0.7Cr-0.3Si, Ti43.5Al-4Nb-1Mo and Ti-47Al-2Cr-8Nb) was investigated by TGA equipment under isothermal conditions in the range of 800-1000 °C. These alloys were cut from the core of bars, previously processed by Electron Beam Melting and successively heat-treated. The composition of the oxide layers was investigated by XRD, SEM-EDS and XPS. Each alloy showed different oxidation behavior at high temperatures. Layer exfoliation or spallation was observed for many samples, but at very different temperatures for the different alloys. When spallation did not happen in a significant extent the oxide layers grew according to a parabolic law. The kinetic rate constants and the activation energies were calculated. These kinetic parameters allowed to assess a rank of oxidation resistance, which can be correlated with the composition of the alloys.
In order to improve the oxidation resistance of Ti-48Al-2Cr-2Nb, ceramic nitride coatings were deposited by a High Power Impulse Magnetron Sputtering (HiPIMS) method. Differently engineered TiAlN and TaAlN protective films were processed and their performances compared. Samples were submitted to thermal cycling under oxidizing atmosphere up to 850° C (40 cycles) and 950°C (100 and 200 cycles), at high heating and cooling rates. For this purpose, a burner rig able to simulate the operating conditions of the different stages of turbine engines was used.
The microstructure and composition of samples before and after oxidation were investigated by several techniques: microscopy (optical and SEM-EDS), X-ray photoelectron spectrometry (XPS) and X-ray diffraction (XRD).
All the TiAlN coatings differently processed provided a remarkable improvement of oxidation resistance. Good adhesion properties were observed even after repeated thermal shocks. HiPIMS pretreatments of the substrate surfaces, performed before the coating deposition, significantly affected the oxidation rate, the oxide layer composition and the coating/substrate adhesion.
The oxide layers formed on the sample surface showed different thickness, depending on the presence of the protective coating and the processing path adopted for its deposition. The nitride coatings appreciably enhanced the oxidation resistance and sustained repeated thermal shocks without showing damage or spallation. Differently TaAlN coating did not improve the oxidation resistance of TiAl substrate.
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Wang, Zhiqi. "Study of Ti-Al-Cr oxidation resistant coatings for γ-TiAl based intermetallic alloys". Thesis, University of Surrey, 2002. http://epubs.surrey.ac.uk/844155/.
Повний текст джерелаАнотація:
Magnetron sputter deposition with single target materials was used to produce amorphous and crystalline Ti-A1-(Cr) alloy coatings on a Ti-50Al substrate. The following coatings were studied: Ti-50Al-10Cr, Ti-53Al-15Cr, Ti-50Al-20Cr and Ti-48Al. The microstructures of the coatings were studied in the as deposited condition and after devitrification and heat treatment. A random distribution of nano-precipitates was formed in amorphous as-deposited coatings. Columnar features were present when the as-received deposit had crystallised during sputter deposition. If crystallization occurred during deposition, a columnar microstructure formed with the columnar fibres being parallel to the deposition direction. For the Ti-50Al-10Cr and Ti-53Al-15Cr deposits, the crystalline domains consisted of lamellar gamma // alpha, i.e. the crystalline deposits had a gamma // alpha texture. The alpha → alpha transformation occurred during deposition. Phase competition in the alloys was studied by combining thermodynamic modelling and transformation kinetics. At 1173K, the Ti-50Al-10Cr alloy transformed to a two-phase microstructure, consisting of the gamma and C14 Ti(Al, Cr)2 phases. The Ti-53Al-15Cr alloy transformed to a three-phase microstructure, consisting of the gamma, tau and the C14 Laves phase. The gamma and tau phases were mixed finely, with gamma // tau. The Ti-50Al-20Cr alloy transformed to a two-phase microstructure, consisting of the gamma and the Cl4 Laves phase. No orientation relationship between the gamma and the C14 Laves phase was observed. Phase evolution studies at lower temperatures in the range 773K to 973K indicated that for the amorphous Ti-48Al alloy, the phase transformation path is: the amorphous phase → alpha → gamma + alpha/alpha2. A fine lamellar structure was formed, with gamma being the dominant phase. For the Ti-50Al-20Cr alloy, the phase transformation path was: the amorphous phase → gamma → gamma + Ti(Al, Cr)2. The experimental observations and the modelling results have clearly suggested a tendency of amorphous phase stabilisation via Cr addition. Thermodynamic modelling also indicated that the driving force for amorphous alloy formation is not much less than that for the precipitation of disordered solution phases. Kinetically, the amorphous phase formation during sputter deposition is related to the suppression of surface diffusion at low substrate temperatures. The temperature processing window for ordered phase formation in the Ti-Al(-Cr) alloys during magnetron sputter deposition was evaluated by the effective diffusion distance. Time dependent nucleation calculations showed that in the Ti-48Al amorphous alloy, it would be kinetically easier to precipitate the alpha phase than the gamma phase. In the case of the Ti-50Al-20Cr alloy, the gamma phase forms in preference of alpha, which is consistent with experimental observations. Diffusion phenomena at the coating/substrate interface and the oxidisation of the coatings were also studied. The experimental Cr diffusion profiles and the simulations for the Ti-Al-Cr coatings and the Ti-50Al substrate indicated that diffusion at 1173K is reasonably slow. The Ti-50Al-10Cr, Ti-53Al-15Cr and the Ti-50Al-20Cr coatings could form protective oxide scales at 1173K. When a columnar structure was present in the crystalline deposit, cracking of the coating was observed when the coating was subject to thermal cycling from elevated temperatures. It is concluded that if cracking of the coatings was to be avoided, amorphous deposits should be preferred.
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Lin, Song-En, and 林頌恩. "Effects of the Additions of Si and Al on Enhancing High-Temperature Oxidation Resistance of Ti-, Nb-, and Mo-based Alloys." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/59075691379715584846.
Повний текст джерелаАнотація:
碩士國立臺灣海洋大學
材料工程研究所
99
The oxidation behabior of binary Ti-Si, Nb-Si, and Mo-Si alloys was studied over the temperature range of 700~ 1000℃ in dry air. In addition, the effect of Al addition on high temperature oxidation resistance of those alloys was also studied for comparative purpose. The results showed that the oxidation kinetics of three Ti-Si alloys at 800~1000℃ followed the parabolic-rate law, with their oxidation rates gradually increasing with temperature. This further indicates that diffusion is the rate-determining step during oxidation. It was also found that the higher the Si content the better the oxidation resistance. In addition, the scales formed on the (TiSi2)91Al9 consisted mostly of α-Al2O3, whose formation is responsible for the further improvement of oxidation resistance. The oxidation kinetics of the Nb-20Si alloy followed a multiple-stage parabolic-rate law at 700~800℃, while no-mass-gain kinetics were observed at 900-1000℃. In addition, the oxidation kinetics of the (Nb-20Si)90Al10 alloy also followed parabolic-rate law at 700~1000℃. The scales formed on the two alloys consisted of fragile, powder-like Nb2O5 structures, implying that the addition of Al can not effectively prevent the pesting phenomenon for the ternary alloy. The scales forms on MoSi2 were composed of volatile spieces of MoO3 during oxidation indicating that the pesting behavior was evident for the MoSi2 alloy. On the other hands, the oxidation kinetics of the (MoSi2)95Al5 ternary alloy followed the parabolic-rate law, indicating that the volatilization of MoO3 was significantly retarded. Based on microstructural analyses, the scales formed on the (MoSi2)95Al5 surface consisted mostly of α-Al2O3, whose formation is also responsible for the improvement of the oxidation resistance for the ternary alloy.
Книги з теми "Oxidation resistance of Ti-Al intermetallic alloys"
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Brady, Michael P. Microstructure/oxidation/microhardness correlations in Þ-based and [tau]-based Al-Ti-Cr alloys. [Washington, D.C: National Aeronautics and Space Administration, 1994.
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Brady, Michael P. Microstructure/oxidation/microhardness correlations in Þ-based and [tau]-based Al-Ti-Cr alloys. [Washington, D.C: National Aeronautics and Space Administration, 1994.
Знайти повний текст джерелаЧастини книг з теми "Oxidation resistance of Ti-Al intermetallic alloys"
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Bahadur, Aruna. "Steel: Aluminum Coatings." In Encyclopedia of Aluminum and Its Alloys. Boca Raton: CRC Press, 2019. http://dx.doi.org/10.1201/9781351045636-140000391.
Повний текст джерелаАнотація:
Aluminum coated steel possesses excellent oxidation and corrosion resistance in sulfur and marine: environments and can substitute for expensive alloy of steels. Hot dip aluminizing (HDA) and pack cementation calorizing (CAL) are dealt with in detail. IN HDA coats, some alloying action takes place, when the substrate is dipped in molten Al at 973 K for 1–2 minutes. The coat consists of an outer pure Al layer, followed by a hard intermetallic layer consisting of FeAl3 and Fe2Al5, forming a serrated interface with the base. Isothermal holding of such samples at 773–933 K for 10 minutes leads to further diffusion and phase changes. This improves resistance to thermal shock and bending. In CAL coats, the process parameters (1173–1223 K/2–4 h and pack composition), were optimized, resulting in appreciable alloying. The surface layer consists of Fe3Al and FeAl, which is comparable to the inner alloy layer of HDA coats. The structure/ property correlation is carried out for both coatings and the results compared.
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Chen, Guoliang, Zuqing Sun, and Xing Zhou. "Oxidation and mechanical behavior of intermetallic alloys in the Ti–Nb–Al ternary system." In High Temperature Aluminides and Intermetallics, 597–601. Elsevier, 1992. http://dx.doi.org/10.1016/b978-1-85166-822-9.50094-7.
Повний текст джерелаТези доповідей конференцій з теми "Oxidation resistance of Ti-Al intermetallic alloys"
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Tian, Zongjun, Lida Shen, Zhidong Liu, and Yinhui Huang. "Microstructure Characteristics and High-Temperature Oxidation Behavior of Plasma-Sprayed and Laser-Remelted MCrAlY Coatings on TiAl Intermetallics." In ASME 2011 International Manufacturing Science and Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/msec2011-50145.
Повний текст джерелаАнотація:
In order to further improve the high-temperature oxidation resistance of TiAl intermetallic alloys, MCrAlY coatings were fabricated by plasma spraying and plasma spraying-laser remelting technologies. The microstructures of the as-sprayed and laser-remelted MCrAlY coatings were studied. In addition, the oxidation behaviors at 850 °C for three samples were investigated. One sample is the matrix of TiA1 intermetallic alloys, the other one is processed by plasma-spraying MCrAlY coatings, and the third one is processed by plasma-spraying and laser-remelting MCrAlY coatings. It was revealed that the oxidation resistance of TiAl intermetallics is weak due to lack of protection of Al2O3 film formed on the surface. The plasma-sprayed MCrAlY coatings have better oxidation resistance than the TiAl intermetallics although the plasma-sprayed MCrAlY coatings have high density of porosity and a typical layered structure. It is demonstrated that most of the holes can be eliminated by laser remelting, leading to the best oxidation resistance of the third sample with the laser-remelted coatings. The high oxidation resistance of the laser-remelted coatings is mainly attributed to three aspects: firstly, an Al enriched zone on the coating surface is formed during laser remelting, which is transformed into a protective Al2O3 film during oxidation process. Secondly, laser remelting eliminates most of the defects in plasma-sprayed coatings and enhances its density, thus decreases the channel of oxidation diffusion in high temperature oxidation process. Thirdly, rapid cooling of laser remelting results in a grain refinement and a preferred oxidation of Al at the initial stage, leading to a reduction of oxidation rate.
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Zhang, Xiaowei, Hongxi Liu, Chuanqi Wang, Weihua Zeng, and Yehua Jiang. "Microstructure and high-temperature oxidation resistance of TiN/Ti 3 Al intermetallic matrix composite coatings on Ti6Al4V alloy surface by laser cladding." In Photonics Asia 2010, edited by Upendra N. Singh, Dianyuan Fan, Jianquan Yao, and Robert F. Walter. SPIE, 2010. http://dx.doi.org/10.1117/12.870732.
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Huang, Xiao. "Microstructure and Oxidation Behaviour of NGB and WGB Joints With Boron/Silicon Free Nickel Base Braze Alloys." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14017.
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Abstract In this study, the microstructure and solidus and liquidus of several Ni-Co-Hf-Zr-Ti-Al braze alloys were first examined with the objective to develop a B and Si free low melting braze alloy for narrow gap (NGB) and wide gap brazing (WGB) and turbine component repair applications. Among various alloys examined, DSC was used to measure the solidus and liquidus during heating and cooling cycles. Following the measurements of liquidus and solidus, the microstructure was evaluated using SEM. Equations for calculating solidus and liquidus based on alloy’s compositions were established and the functions of each elements on these two characteristic temperatures were discussed. One selected alloy with a liquidus of 1201 °C was further employed for NGB and WGB experiments. The results showed that it was able join CMSX-4 at 1240°C without interfacial voids; and with the use of externally applied pressure and extended homogenization treatment the interfacial intermetallic compounds were substantially removed. Furthermore, the same braze alloy was used to fill a large artificial cavity in a WGB scheme at a reduced temperature of 1200°C. The braze alloy was able to fully bond the filler powder alloy in addition to join the two alloys to a IN 738 substrate. Finally, oxidation test was conducted at 1050°C (isothermal in static air) for 100 hours after NGB of CMSX-4 and WGB of IN 738. The results showed that the oxide formed on the standalone braze alloy is very dense and there is no sign of spallation. It contained primarily NiO (+CoO) with no other elements measured. For the NGB joints, large amount of scale spallation was observed on base alloy CMSX-4 while the NGB joint remained spallation free. The oxide formed on the NGB was NiO with partitions of Co, Al, Ti, Cr, and W. The WGB joint region in IN 738 showed oxide scale spallation on the IN 738 substrate side, leaving behind steps and depression on the sample surface. In the WGB joint itself, there were three notable phases after oxidation test, however, no scale spallation could be found. For the majority part of the surface, a Ni-rich oxide covered the surface. There were areas of smaller oxide particles with higher Cr content. Overall, the new boron/silicon free braze alloy was found to be able to join several superalloys in both WGB and NGB schemes without occurrence of defects and the oxidation resistance was superior to both substrate alloys examined in this study.
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Capata, Roberto, Enrico Sciubba, Luigi Menna, Andrea Brotzu, Ferdinando Felli, and Daniela Pilone. "Design, Prototyping and Preliminary Testing of a Ti-Al Gas Turbine Blade." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-50058.
Повний текст джерелаАнотація:
This work investigates the feasibility of manufacturing a turbine blade made of a Ti-Al intermetallic alloy by means of investment casting. The work is based on a multidisciplinary approach that combines a conventional CFD analysis of the flow field around the statoric and rotoric blades with the results of several metallurgical studies aimed at the optimization of the alloy composition by finding the best compromise among fracture toughness, oxidation resistance at high temperatures and mechanical properties. The combination of the two techniques lead to an iterative procedure (of which only the first two steps are reported in this paper): a conventional blade is first modeled and the corresponding investment cast is produced via a 3D printing technique; a first version of the blade is built; a modified blade shape is then obtained by a refined CFD study; as a last step the final version of the blade is cast. On the basis of standard operational specifications representative of modern gas turbines, a turbine blade was therefore designed, tested by CFD (ANSYS-FLUENT) to ensure proper fluid dynamic performance, and its levels of thermo-mechanical stress under working conditions were calculated via a commercial CAD software (ANSYS). The fully 3D version of the component was subsequently prototyped by means of fused deposition modeling. A full-scale set of blades (blade height approximately 7 cm, blade chord approximately 5 cm) was produced by means of investment casting in an induction furnace. The produced items showed acceptable characteristics in terms of shape and soundness. The blade alloy was analyzed by performing metallographic investigations and some preliminary mechanical tests. At the same time, the geometry was refined by a complete and more complex CFD study, and a slightly modified shape was obtained. Its final testing under operative conditions is left for a later study. The paper describes the spec-to-final product procedure and discusses some critical aspects of this manufacturing process such as the considerable reactivity between the molten metal and the mold material, the resistance of the ceramic shell to the molten metal impact at temperatures as high as 2073 K and the limit mold porosity that may compromise the component surface finish. Furthermore, a detailed account is provided for the CFD results that led to the modification of the original commercial shape: pressure, velocity and temperature fields in the statoric and rotoric channels are described in some detail, and a preliminary performance assessment of the turbine stage is presented and discussed.
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Wang, H. T., C. J. Li, G. J. Yang, and C. X. Li. "Formation of Fe-Al Intermetallic Compound Coating Through Cold Spraying." In ITSC2006, edited by B. R. Marple, M. M. Hyland, Y. C. Lau, R. S. Lima, and J. Voyer. ASM International, 2006. http://dx.doi.org/10.31399/asm.cp.itsc2006p0157.
Повний текст джерелаАнотація:
Abstract Intermetallic materials have excellent high temperature oxidation resistance and erosion, cavitation resistances and are promising coating materials with many potential industrial applications. In this study, the formation of Fe-Al intermetallic compound-based coating was performed by cold spraying assisted by a post-annealing treatment. Fe-Al alloy composite powder containing 20wt% WC-Co was produced by ball milling process. Nano-structured Fe-Al alloy coating was deposited through cold spraying. The coating was annealed at different temperatures. The microstructure of the coating was characterized by scanning electron microscopy, optical microscopy and x-ray diffraction analysis. It was found that the microstructure of the as-sprayed coating depended significantly on the microstructure of the powder. A Fe-Al intermetallic phase was formed during the annealing at a temperature higher than 500°C. Moreover, grain growth occurred with the increase of the annealing temperature. The results showed that the microhardness of the as-sprayed coating reached 600HV and more. The effect of the annealing treatment on the coating microstructure and hardness was examined.
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Wilden, J., and H. Frank. "Formation of Intermetallic Phases by Laser Alloying of Thermally Sprayed Ti and Al Coatings for Enhanced Wear Resistance of Lightweight Materials." In ITSC2003, edited by Basil R. Marple and Christian Moreau. ASM International, 2003. http://dx.doi.org/10.31399/asm.cp.itsc2003p0475.
Повний текст джерелаАнотація:
Abstract Lightweight materials such as Al and Ti alloys tend to show poor wear resistance. However, laser alloying of thermally sprayed coatings can be used to form intermetallic phases within the surface area to overcome this disadvantage and to build a metallurgical bond between substrate and coating. Such phases formed in an exothermic reaction may show excellent corrosion behaviour and wear resistance. These reactions can be used to influence the surface properties by remelting metallic coatings on Al or Ti substrates. With respect to the wear behaviour, Ti and Al intermetallics are of great interest. Ti and Al alloys were coated by Al, Ti, and Ni respectively. The different structures on the surface of the alloys depend first on the laser processing parameters resulting in the overheated melt and as well as the latent heat of the formed intermetallic phases. The experimental results clearly show that for short dwell times the latent heat dominates the solidification process and that at high solidification rates the microstructure formation becomes nearly independent from the process parameters. This effect is of special interest for industrial applications as quality requirements ask for robust processes. The paper discusses the metallurgical fundamentals of intermetallic phases and the energy balance of the solidification while giving a deep insight into the influence of different process parameters. Lastly, the properties of alloyed surfaces are discussed.
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Sundararajan, T., S. Kuroda, T. Itagaki, and F. Abe. "Effect of Thermal Sprayed Al on the Steam Oxidation Resistance of 9Cr-1Mo Steel." In ITSC2003, edited by Basil R. Marple and Christian Moreau. ASM International, 2003. http://dx.doi.org/10.31399/asm.cp.itsc2003p0503.
Повний текст джерелаАнотація:
Abstract Thermal spray of Al was carried out on the modified 9Cr-1Mo steel to evaluate the steam oxidation resistance of the sprayed Al coating. Atmospheric plasma spray process (APS) was used to coat aluminum on sandblasted 9Cr-1Mo steel substrate. The coating thickness was around 40 µm. The coated specimens were steam oxidized in four different temperatures, ranging from 600 to 750°C. The results show that the scale growth occurred in the interface between coating and substrate subsequently it penetrated into the coating structure. Al diffused into the alloy substrate with high solubility. The diffusion increased with increase in the steam temperature and test duration. Diffused aluminum formed the high hardness intermetallic compound in the substrate near the coating/substrate interface. With increase in the test duration, the intermetallic compound moved towards the bulk and at prolonged aging, it became dissolved. This was identified from the decrease in the micro hardness values at coating/substrate interface at prolonged duration. The scale growth at the substrate surface of Al sprayed steel was much controlled compared to the uncoated specimens.
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Liang, J., W. Gao, and D. Zhang. "HVOF Sprayed Ti(Al,O)/Al2O3 Based Composite Coatings for High Temperature Applications." In ITSC2005, edited by E. Lugscheider. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2005. http://dx.doi.org/10.31399/asm.cp.itsc2005p0690.
Повний текст джерелаАнотація:
Abstract Ti(Al,O)/Al2O3 based composite powders with three different compositions were produced by high energy milling, sintering and grounding. High velocity oxy-fuel (HVOF) spraying was used to coat these powders onto Ti-6Al-4V alloy samples. High temperature oxidation and hot corrosion behaviour of the coatings was studied in dry air and Na2SO4 + NaCl vapour, respectively. The results showed that Ti(Al,O)/Al2O3 coatings have a much improved oxidation and hot corrosion resistance compared to the substrate Ti-6Al-4V alloy. The oxide formed on the surface of the coatings after high temperature exposure is composed of a mixture of Al2O3 and TiO2. The oxide scales have excellent adhesion to the coatings, showing superior scale spallation resistance. Microstructural analysis suggested that the Al2O3 particles could act as a diffusion barrier to O and Ti therefore reducing the oxidation rate. The Al2O3 phase also forms an interlocking network penetrating throughout the oxide scale, reinforcing the fragile TiO2 containing scale. It is believed this composite system can provide a new generation of coatings to Ti based alloys, raising the application temperature of Ti alloys from ~650ºC to 800-900ºC without excessive scale spallation.
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Zhang, Li, Di Wang, Xian-Jin Liao, Xiao-Tao Luo, and Chang-Jiu Li. "The Influence of Diamond Addition to Ni-Al Powder on Oxidation Behavior of Ni-Al During Plasma Spraying for High Performance Oxide-Free Ni-Al Intermetallic Coating." In ITSC2021, edited by F. Azarmi, X. Chen, J. Cizek, C. Cojocaru, B. Jodoin, H. Koivuluoto, Y. C. Lau, et al. ASM International, 2021. http://dx.doi.org/10.31399/asm.cp.itsc2021p0447.
Повний текст джерелаАнотація:
Abstract Ni-Al intermetallics have excellent corrosion and oxidation resistance, but their use in thermal spraying has been limited due to issues with in-flight oxidation. In this study, a novel approach is proposed to remove oxide from Ni-Al droplets in-flight by adding a deoxidizer (diamond) to the feedstock powder. A mixture of nickel, aluminum, and diamond powders was mechanically alloyed using a combination of cryogenic and planetary ball milling. The resulting Ni/Al/diamond composite powder was then plasma sprayed via the APS process, forming Ni-Al coatings on Inconel 738 substrates. Phase composition, microstructure, porosity, and microhardness of the coatings were characterized by X-ray diffraction, scanning electron microscopy, image analysis, and hardness testing, respectively. Oxygen content measurements showed that the coatings contained significantly less oxygen than coatings made from ordinary Ni/Al powders. In-flight particle temperatures were also measured and found to be higher than 2300 °C. The low oxygen content in the coatings is attributed to the in-situ deoxidizing effect of ultrahigh temperature droplets which are also oxide-free.
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Brizuela-Colmenares, Natalia, and Juan Muñoz-Saldaña. "Ni-5wt% Al Coatings Deposited by Twin Wire Arc Spraying for Molten Aluminum Attack Protection." In ITSC2021, edited by F. Azarmi, X. Chen, J. Cizek, C. Cojocaru, B. Jodoin, H. Koivuluoto, Y. C. Lau, et al. ASM International, 2021. http://dx.doi.org/10.31399/asm.cp.itsc2021p0700.
Повний текст джерелаАнотація:
Abstract Nickel-aluminum alloys are widely used in harsh environments due to their corrosion resistance, high melting temperature, and thermal conductivity. In this work, Ni-5wt%Al coatings were deposited by twin-wire arc spraying (TWAS) on tool steel using a design of experiments approach to study the effect of process parameters on coating microstructure and performance. Test results presented in the form of process maps show how N2 pressure, stand-off distance, and current affect in-flight particle velocity and temperature as well as coating thickness and oxide content. Using this information, optimized coatings were then deposited on test substrates and subjected, along with uncoated tool steel, to several hours of molten aluminum attack. The coated samples showed no signs of physical or chemical damage, whereas the uncoated substrates experienced oxidation, aluminum infiltration, and formation of Fe-Al intermetallics.