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1.
C. Giolli A. Scrivani G. Rizzi F. Borgioli G. Bolelli L. Lusvarghi 《Journal of Thermal Spray Technology》2009,18(2):223-230
Thick thermal barrier coatings (TBCs), consisting of a CoNiCrAlY bond coat and yttria-partially stabilized zirconia top coat
with different porosity values, were produced by air plasma spray (APS). The thermal fatigue resistance limit of the TBCs
was tested by furnace cycling tests (FCT) according to the specifications of an original equipment manufacturer (OEM). The
morphology, residual stresses, and micromechanical properties (microhardness, indentation fracture toughness) of the TBC systems
before and after FCT were analyzed. The thermal fatigue resistance increases with the amount of porosity in the top coat.
The compressive in-plane stresses increase in the TBC systems after thermal cycling; nevertheless the increasing rate has
a trend contrary to the porosity level of top coat. The data suggest that the spallation happens at the TGO/top coat interface.
The failure mechanism of thick TBCs was found to be similar to that of conventional thin TBC systems made by APS. 相似文献
2.
The Sensitivity of Abradable Coating Residual Stresses to Varying Material Properties 总被引:2,自引:0,他引:2
R. E. Johnston 《Journal of Thermal Spray Technology》2009,18(5-6):1004-1013
This paper reports recent research on abradable materials employed for aero-engine applications. Such thermal spray coatings are used extensively within the gas turbine, applied to the inner surface of compressor and turbine shroud sections, coating the periphery of the blade rotation path. The function of an abradable seal is to wear preferentially when rotating blades come into contact with it, while minimizing over-tip clearance and improving the efficiency of the engine. Thermal spraying of an abradable coating onto a substrate imparts two components of residual stress; rapid quenching stresses as the spray material cools on impact and stresses arising from differential thermal contraction. In-service thermal stresses are superimposed by the differential expansion of these bonded layers. The combination of the production and operation history will lead to thermal-mechanical fatigue damage within the abradable coating. The present paper will describe the numerical modeling and sensitivity analysis of the thermal spray process. The sensitivity of residual stresses (with varying material properties, coating/substrate thickness, Poisson’s ratio, and substrate temperature) predicted by the Tsui and Clyne progressive deposition model enabled identification of performance drivers to coating integrity. Selecting material properties that minimize in-service stresses is a crucial stage in advancing future abradable performance. 相似文献
3.
A. Scrivani G. Rizzi U. Bardi C. Giolli M. Muniz Miranda S. Ciattini A. Fossati F. Borgioli 《Journal of Thermal Spray Technology》2007,16(5-6):816-821
High-temperature thermal fatigue causes the failure of thermal barrier coating (TBC) systems. This paper addresses the development
of thick TBCs, focusing on the microstructure and the porosity of the yttria partially stabilized zirconia (YPSZ) coating,
regarding its resistance to thermal fatigue. Thick TBCs, with different porosity levels, were produced by means of a CoNiCrAlY
bond coat and YPSZ top coat, both had been sprayed by air plasma spray. The thermal fatigue resistance of new TBC systems
and the evolution of the coatings before and after thermal cycling was then evaluated. The limit of thermal fatigue resistance
increases depending on the amount of porosity in the top coat. Raman analysis shows that the compressive in-plane stress increases
in the TBC systems after thermal cycling, nevertheless the increasing rate has a trend which is contrary to the porosity level
of top coat.
This article is an invited paper selected from presentations at the 2007 International Thermal Spray Conference and has been
expanded from the original presentation. It is simultaneously published in Global Coating Solutions, Proceedings of the 2007 International Thermal Spray Conference, Beijing, China, May 14-16, 2007, Basil R. Marple, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain
Montavon, Ed., ASM International, Materials Park, OH, 2007. 相似文献
4.
Gas turbines provide one of the most severe environments challenging material systems nowadays. Only an appropriate coating system can supply protection particularly for turbine blades. This study was made by comparison of properties of two different types of thermal barrier coatings (TBCs) in order to improve the surface characteristics of high temperature components. These TBCs consisted of a duplex TBC and a five layered functionally graded TBC. In duplex TBCs, 0.35 mm thick yittria partially stabilized zirconia top coat (YSZ) was deposited by air plasma spraying and ~0.15 mm thick NiCrAlY bond coat was deposited by high velocity oxyfuel spraying. ~0.5 mm thick functionally graded TBC was sprayed by varying the feeding ratio of YSZ/NiCrAlY powders. Both coatings were deposited on IN 738LC alloy as a substrate. Microstructural characterization was performed by SEM and optical microscopy whereas phase analysis and chemical composition changes of the coatings and oxides formed during the tests were studied by XRD and EDX. The performance of the coatings fabricated with the optimum processing conditions was evaluated as a function of intense thermal cycling test at 1100 °C. During thermal shock test, FGM coating failed after 150 and duplex coating failed after 85 cycles. The adhesion strength of the coatings to the substrate was also measured. Finally, it is found that FGM coating has a larger lifetime than the duplex TBC, especially with regard to the adhesion strength of the coatings. 相似文献
5.
Ajdelsztajn L. Tang F. Schoenung J. M. Kim G. E. Provenzano V. 《Journal of Thermal Spray Technology》2005,14(1):23-30
Thermal barrier coating systems protect turbine blades against high-temperature corrosion and oxidation. They consist of a
metal bond coat (MCrAlY, M = Ni, Co) and a ceramic top layer (ZrO2/Y2O3). In this work, the oxidation behavior of conventional and nanostructured high-velocity oxyfuel (HVOF) NiCrAlY coatings has
been compared. Commercially available NiCrAlY powder was mechanically cryomilled and HVOF sprayed on a nickel alloy foil to
form a nanocrystalline coating. Freestanding bodies of conventional and nanostructured HVOF NiCrAlY coatings were oxidized
at 1000 °C for different time periods to form the thermally grown oxide layer. The experiments show an improvement in oxidation
resistance in the nanostructured coating when compared with that of the conventional one. The observed behavior is a result
of the formation of a continuous Al2O3 layer on the surface of the nanostructured HVOF NiCrAlY coating. This layer protects the coating from further oxidation and
avoids the formation of mixed oxide protrusions present in the conventional coating.
The original version of this article was published as part of the ASM Proceedings, Thermal Spray 2003: Advancing the Science and Applying the Technology, International Thermal Spray Conference (Orlando, FL), May 5–8 2003, Basil R. Marple and Christian Moreau, Ed., ASM International,
2003. 相似文献
6.
The effects of coating defects, such as pores and cracks, on the thermal fatigue behavior of zirconia based thermal barrier coatings (TBCs) have been investigated. Duplex TBCs, which are composed of an 8 wt.% Y2O3 stabilized ZrO2 (YSZ) layer on top of a NiCrAlY bond layer were produced by detonation gun spraying. Thermal fatigue tests were conducted on three different TBC specimens, the YSZ layers of which were varied in terms of porosity and crack morphology, and failure analyses were subsequently carried out on the tested specimens. From these results, the roles of the defects on the thermal and mechanical degradation behavior of the TBCs were investigated. 相似文献
7.
Effect of Chemical Compositions and Surface Morphologies of MCrAlY Coating on Its Isothermal Oxidation Behavior 总被引:1,自引:0,他引:1
Yong Li Chang-Jiu Li Qiang Zhang Lu-Kuo Xing Guan-Jun Yang 《Journal of Thermal Spray Technology》2011,20(1-2):121-131
Chemical composition and surface morphology of MCrAlY coatings are factors which influence the oxidation behavior and the thermal durability of thermal barrier coatings. In this study, Cold-sprayed Ni20Cr10AlY and Ni23Co20Cr8.5Al4.0Ta0.6Y coatings with polished surfaces were employed to study the effect of composition on the oxidation behavior. The cold-sprayed MCrAlY coatings at the as-sprayed and shot-peened surface conditions, along with the low pressure plasma-sprayed MCrAlY coating with sputters adhered weakly on the surface, were employed to investigate the effects of surface morphologies of MCrAlY coatings on their oxidation behavior. Cold-sprayed Ni20Cr10AlY coating exhibited a two-stage oxidation behavior and a higher TGO growth rate than that of the cold-sprayed Ni23Co20Cr8.5Al4.0Ta0.6Y coating at the rapid growth stage. After 10-h oxidation, the TGO on the as-cold-sprayed coating surface was mainly constituted by Al2O3, while the TGO on the coating surface attached with sputters was composed of Al2O3 and Cr/Ni-oxides. After 500-h oxidation, Cr2O3 and porous spinel appeared in the TGO on the surface of the as-cold-sprayed coatings with different compositions. The growth of Cr/Ni-oxides was attributed to the Al depletion. The content of spinel decreased on the cold-sprayed NiCrAlY with a shot-peened surface compared with the as-sprayed coating. 相似文献
8.
V. Teixeira M. Andritschky H. Gruhn W. Malléner H. P. Buchkremer D. Stöver 《Journal of Thermal Spray Technology》2000,9(2):191-197
ZrO2-7 wt.% Y2O3 plasma-sprayed (PS) coatings were applied on high-temperature Ni-based alloys precoated by physical vapor deposition with
a thin, dense, stabilized zirconia coating (PVD bond coat). The PS coatings were applied by atmospheric plasma spraying (APS)
and inert gas plasma spraying (IPS) at 2 bar for different substrate temperatures. The thermal barrier coatings (TBCs) were
tested by furnace isothermal cycling and flame thermal cycling at maximum temperatures between 1000 and 1150 °C. The temperature
gradients within the duplex PVD/PS thermal barrier coatings during the thermal cycling process were modeled using an unsteady
heat transfer program. This modeling enables calculation of the transient thermal strains and stresses, which contributes
to a better understanding of the failure mechanisms of the TBC during thermal cycling. The adherence and failure modes of
these coating systems were experimentally studied during the high-temperature testing. The TBC failure mechanism during thermal
cycling is discussed in light of coating transient stresses and substrate oxidation. 相似文献
9.
Kai Yang Xiaming Zhou Chenguang Liu Shunyan Tao Chuanxian Ding 《Journal of Thermal Spray Technology》2013,22(7):1154-1162
Al2O3, Cr2O3, and Al2O3-Cr2O3 composite coatings were produced by plasma spraying. Their tribological properties were evaluated at high load conditions. The average friction coefficients, wear rates, and worn surface temperatures of the coating/graphite pairs were measured. Compared with the single coating/graphite pairs, the friction coefficients of composite coating/graphite pairs are more stable. The corresponding wear rates and worn surface temperatures are lower, which may be conducive to the formation of more effective and stable graphite transfer film on the surface of the coating subjected to abrasion. Especially, 10wt.%Al2O3-90wt.%Cr2O3 (AC90) composite coating shows better anti-wear performance, which may be attributed to its higher thermal conduction. 相似文献
10.
Al2O3 diffusion barriers of various thicknesses have been fabricated by filtered arc ion plating between the NiCrAlY coating and the O-Ti2AlNb alloy. Isothermal oxidation tests and three-point bend tests have been conducted to investigate the influence of the Al2O3 diffusion barriers on the oxidation and interfacial fracture behaviour of the coatings. The results indicate that the Al2O3 diffusion barrier defers interdiffusion and gives oxidation resistance of the NiCrAlY coatings. The thickness of the Al2O3 interlayer not only influences the oxidation behaviour but also affects the interfacial fracture properties. Additionally, thermal exposure affects the critical load in three-point bend tests. 相似文献
11.
Feng Zhang Cunguan Xu Hao Lan Chuanbing Huang Yang Zhou Lingzhong Du Weigang Zhang 《Journal of Thermal Spray Technology》2014,23(6):1019-1028
A novel NiTi/BN composite abradable coating and two traditional Ni/C and Ni/BN coatings were manufactured with NiAl as the bond layer using thermal spray technology and their corrosion behaviors were investigated. In salt spray corrosion testing of the Ni/BN coating, defective sites of the metal matrix were corroded preferentially. Simulated occlusion experiments and electrochemical tests indicated that migration of ions resulted in pH decrease and Cl? enrichment in defects, and a more aggressive electrolyte led to a decrease of the corrosion potential of the metal inside defects but an increase of the corrosion current density, representing an autocatalytic corrosion process. Moreover, galvanic corrosion between the top and bond coatings of the abradable system was studied via the electrochemical technique. The results showed that, for the NiTi/BN, Ni/BN, and Ni/graphite coatings with a NiAl bond coating, current flow was generated between the anode and cathode. The NiTi/BN coating acted as the cathode due to its passivation, while the Ni/BN and Ni/graphite coatings acted as the anode because of their lower corrosion potential compared with the NiAl coating. The anode suffered serious corrosion damage due to galvanic corrosion, while the cathode corroded only slightly. 相似文献
12.
A Ni–24Cr–6Al–0.7Y (NiCrAlY) coating was deposited on a nickel-base superalloy by low-pressure plasma spraying, and the top
coating, ZrO2 partially stabilized with Y2O3 (7.5 wt%), was deposited on the NiCrAlY coating by air-plasma spraying. The cyclic-oxidation behavior of the NiCrAlY + YSZ
coating exposed to NaCl vapor was investigated under atmospheric pressure at 1,050 °C, 1,100 °C and 1,150 °C. The cyclic-oxidation
life of the NiCrAlY + YSZ coating in the presence of NaCl vapor was shortened compared with that in air. The higher the temperature
is, the shorter the cyclic oxidation life. The oxide scale formed at the interface between the bond coat and the ceramic layer
after exposure to NaCl vapor consisted of voluminous and non-protective NiO, Al2O3 and NiCr2O4 spinel. The failure of the TBC exposed to NaCl vapor occurs within the top coat and close to the YSZ/thermal growth oxide
interface. The failure mechanism has been discussed based on the experimental results and thermodynamics. 相似文献
13.
Mohammadreza DAROONPARVAR Muhamad Azizi Mat YAJID Noordin Mohd YUSOF Saeed FARAHANY Mohammad Sakhawat HUSSAIN Hamid Reza BAKHSHESHI-RAD Z. VALEFI Ahmad ABDOLAHI 《中国有色金属学会会刊》2013,23(5):1322-1333
A thermally grown oxide (TGO) layer is formed at the interface of bond coat/top coat. The TGO growth during thermal exposure in air plays an important role in the spallation of the ceramic layer from the bond coat. High temperature oxidation resistance of four types of atmospheric plasma sprayed TBCs was investigated. These coatings were oxidized at 1000 °C for 24, 48 and 120 h in a normal electric furnace under air atmosphere. Microstructural characterization showed that the growth of the TGO layer in nano NiCrAlY/YSZ/nano Al2O3 coating is much lower than in other coatings. Moreover, EDS and XRD analyses revealed the formation of Ni(Cr,Al)2O4 mixed oxides (as spinel) and NiO onto the Al2O3 (TGO) layer. The formation of detrimental mixed oxides (spinels) on the Al2O3(TGO) layer of nano NiCrAlY/YSZ/nano Al2O3 coating is much lower compared to that of other coatings after 120 h of high temperature oxidation at 1000 °C. 相似文献
14.
In-Hwan Shin Jae-Mean Koo Chang-Sung Seok Sung-Ho Yang Tack-Woon Lee Bum-Soo Kim 《Surface & coatings technology》2011
Plasma-sprayed thermal barrier coatings (TBCs) are applied to protect the blades of a gas turbine system from high-temperature gas and to lower the surface temperature of the blades. The failure of TBC is directly connected to the failure of the blades because the spallation of a ceramic layer leads to the acceleration of local corrosion and oxidation at the location of failure. Therefore, the spallation life of TBC is very important in the evaluation of the reliability of a gas-turbine blade.In this study, thermal fatigue tests were performed at 1100 °C and 1151 °C. Then, c-scanning and bond strength tests were performed for TBC specimens that were thermally aged by thermal fatigue tests. From the results, an empirical equation based on the ratio of the delamination area and the thermal cycle number was presented and the spallation life of a TBC specimen could be roughly estimated using the relationship between the delaminated area and the number of cycles. 相似文献
15.
Mechanical characterisation of AlSi-hBN, NiCrAl-Bentonite, and NiCrAl-Bentonite-hBN freestanding abradable coatings 总被引:1,自引:0,他引:1
R.E. Johnston 《Surface & coatings technology》2011,205(10):3268-3273
This paper reports recent research on abradable materials employed for aero-engine applications. Such thermal spray coatings are used extensively within the gas turbine, applied to the inner surface of compressor and turbine shroud sections, coating the periphery of the blade rotation path. The function of an abradable seal is to wear preferentially when rotating blades come into contact with it, while minimising over-tip clearance and improving the efficiency of the engine.Historically, our understanding of abradables has been limited, with their design and service operation often described as a “black art.” For instance, there is a distinct lack of materials property data for all abradable systems, mainly due to the difficulty of testing this unique class of material under bulk loading conditions (tension or compression).The present paper will describe the mechanical assessment of two families of abradables with either aluminium or nickel as the matrix phase. A novel method was developed to produce the free-standing abradable test specimens, employing thermal spraying and dissolvable moulds. These specimens were suitable for evaluation under static and cyclic tensile stress conditions. The absence of any substrate and associated mechanical interactions has meant that unique measurements of Young's modulus, tensile strength, and strain to failure were obtained for these complex composite materials in their own right.This work forms part of a wider programme to gain a greater understanding of abradable materials, how they perform, and ultimately how to improve their performance in-service. 相似文献
16.
H. M. Tawancy 《Oxidation of Metals》2018,90(3-4):383-399
It is demonstrated that the addition of Pt to CoNiCrAlY overlay coating can significantly improve its oxidation resistance and thermal stability as well as its performance in thermal barrier coatings. The addition of Pt is found to stabilize a surface layer with composition based upon NiAlPt2 with L1o superlattice in addition to enhancing a more favorable distribution of Y and restricting the outward diffusion of detrimental substrate elements particularly Ta and Ti. Due to these beneficial effects, utilizing the Pt-modified bond coating in a TBC system with top coating of zirconia stabilized by yttria is found to extend its lifetime from 410 ± 42 h to 956 ± 48 h as determined from cycling oxidation tests at 1150 °C. However, spallation of the top coatings in the two systems has been correlated with loss of oxide adherence to the bond coatings. 相似文献
17.
Masayuki Arai 《Journal of Thermal Spray Technology》2017,26(6):1207-1221
Thermal stress generated on thermal barrier coatings (TBCs) by volcanic ash (VA) deposition was assessed measuring the tip deflection of a multilayered beam structure as a function of temperature. The TBC in this study was deposited onto the surface of a blade utilized in a land-based gas turbine which is composed of 8 wt.%Y2O3-ZrO2/CoNiCrAlY on a Ni-based superalloy. The VA-deposited TBC sample was heated at 1453 K, and the effect of VA deposition on TBC delamination was examined in comparison with a TBC sample without VA deposition as a reference. On the basis of the VA attack damage mechanism which was investigated via the tip deflection measurement and a comprehensive microstructure examination, a damage-coupled constitutive model was proposed. The proposed model was based on the infiltration of the molten VA inside pores and phase transformations of yttria -tabilized zirconia in the TBC system. The numerical analysis results, which were simulated utilizing the finite element code installing the developed constitutive model, showed us that VA attack on the TBC sample induced near-interfacial cracks because of a significant increasing in the coating stress. 相似文献
18.
Air plasma sprayed TBCs usually include lamellar structure with high interconnected porosities which transfer oxygen from YSZ layer towards bond coat and cause TGO growth and internal oxidation of bond coat.The growth of thermally grown oxide (TGO) at the interface of bond coat and ceramic layer and internal oxidation of bond coat are considered as the main destructive factors in thermal barrier coatings.Oxidation phenomena of two types of plasma sprayed TBC were evaluated: (a) usual YSZ (yttria stabilized zirconia), (b) layer composite of (YSZ/Al2O3) which Al2O3 is as a top coat over YSZ coating. Oxidation tests were carried out on these coatings at 1100°C for 22, 42 and 100h. Microstructure studies by SEM demonstrated the growth of TGO underneath usual YSZ coating is higher than for YSZ/Al2O3 coating. Also cracking was observed in usual YSZ coating at the YSZ/bond coat interface. In addition severe internal oxidation of the bond coat occurred for usual YSZ coating and micro-XRD analysis revealed the formation of the oxides such as NiCr2O4, NiCrO3 and NiCrO4 which are accompanied with rapid volume increase, but internal oxidation of the bond coat for YSZ/Al2O3 coating was lower and the mentioned oxides were not detected. 相似文献
19.
In the present study Ni−18Cr−6Al, Ni−22Cr−10Al−1Y and TiAlO composite powders were coated on Ti−6Al−4V substrates by atmospheric
plasma spraying, and the coated specimens were evaluated by isothermal and cyclic oxidation resistance tests at 800°C. The
oxidation kinetics of the plasma sprayed NiCrAl, NiCrAlY, and TiAlO composite coated specimens obey a parabolic rate law.
The oxidation resistance of the plasma sprayed NiCrAl and NiCrAlY coatings is superior to that of plasma sprayed TiAlO composite
coating. The best oxidation resistance was observed in the plasma sprayed NiCrAlY coatings. This is mainly attributed to the
formation of Y−Al−O complex oxides and Ni3Al with higher thermal stability on the coatings. 相似文献
20.
The hot-corrosion behavior of thermal barrier coatings (TBCs) has been studied by comparing double-layer coatings and graded
coatings. Two types of oxide ceramics, 2CaO·SiO2-15mass%CaO·ZrO2 (C2S-15CZ) and 8 mass% Y2O3·ZrO2 (8YSZ), with a bond coating of NiCrAlY, were applied to metallic substrates in this study. After hot-corrosion testing with
V2O5-Na2SO4 corrosive ash for 3 h at 1273 K, the TBCs were investigated by visual inspection, a scanning electron microscope, x-ray diffraction,
and electron probe microanalysis. The findings for the resulting coating of C2S-15CZ reacted with V2O5 only where it was in direct contact with the corrosive ash. The affected area from the reaction was limited to the coating
surface where V2O5 was present. The coating showed adequate hot-corrosion resistance against V2O5-Na2SO4 corrosive ash for 3 h at 1273 K. The findings for the 8YSZ coating were that Y2O3, the stabilizing component, particularly reacted with V2O5 and lost its function, which led to partial spalling of the coating. It was observed that the hot-corrosion resistance of
the double-layer TBC was largely influenced by the performance of a corrosion-resistant NiCrAlY bond coat, which provided
protection against corrosive components penetrating through the ceramic topcoat. Last, the graded coating degraded due to
the oxidation of NiCrAlY particles that existed near the topcoat surface and affected the durability of the TBC. 相似文献