TBC system

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High-temperature cyclic oxidation of Pt-rich γ-γ’ bond-coatings. Part II: Effect of Pt and Al on TBC system lifetime

High-temperature cyclic oxidation of Pt-rich γ-γ’ bond-coatings. Part II: Effect of Pt and Al on TBC system lifetime

at 1100 °C. Contrary to the results obtained for the same systems without top coat, aluminium addition during the bond-coating fabri- cation did not improve the durability of the TBCs with a Pt-rich γ-γ’ coating. This was explained by the fact that TBC systems failed much earlier than the breakaway observed on coated superalloy without top coat. The Al addition during manufacturing is beneficial for a very long life (more than 5 or 10 thousands hours at 1100 °C), because of the consumption of Al by oxidation, but the Al addition is not necessary and apparently even detrimental for a TBC life of 2000 h. TBC systems fail earlier than breakaway of the bond-coating (i.e. chemical failure) be- cause of the effect of mechanical stresses during thermal cycling. The level of Al in the bond-coating at failure of the TBC does not seem to be critical, but the Pt concentration could be critical. Pt level in the coating and just below the TGO plays a role on the adhesion of the TGO and certainly a role on the mechanical properties of the bond-coating. Further work is needed to confirm this assumption.
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High-temperature cyclic oxidation of Pt-rich γ-γ’ bond-coatings. Part II: Effect of Pt and Al on TBC system lifetime

High-temperature cyclic oxidation of Pt-rich γ-γ’ bond-coatings. Part II: Effect of Pt and Al on TBC system lifetime

After fabrication, the EBPVD top coat had a good adhesion to the bond-coating due to the formation of a thin layer of Al 2 O 3 during TBC processing. Additional systems were fabricated in a second processing run in order to obtain coatings with larger platinum and aluminium con- centrations for Pt + Al γ-γ’ systems. These systems were referenced with the “run 2″ tag. These corresponded to the Pt-only γ-γ’ coatings (TBC-P1 to P4), some 5/5 Pt + Al coatings (TBC-PA7 to PA10) and some β-(Ni,Pt)Al coatings (TBC-B3 to B5), the latter being considered as the industrial reference system. The microstructure of these three sys- tems after fabrication was similar to the ones of systems without top coat ( Fig. 2 ) [ 14 ]. The average chemical compositions of the γ-γ’ zones for the Pt-only (TBC-P1), Pt + Al γ-γ’ (TBC-PA7) coatings and of the β layer for the β-(Ni,Pt)Al coating (TBC-B3) are reported in the Table 2 . Fig. 1. Backscattered electron images of metallographic cross-sections of the Pt + Al γ-γ’ bond-coatings from the run 1: (a, b) TBC-PA1 and TBC-PA4 in the as- annealed condition, (c, d) TBC-PA11 and TBC-PA15 after 300 cycles at 1100 °C.
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Step-by-step investigation of degradation mechanisms induced by CMAS attack on YSZ materials for TBC applications

Step-by-step investigation of degradation mechanisms induced by CMAS attack on YSZ materials for TBC applications

Our aim in this study is to describe the effects of CMAS on sol –gel YSZ materials exhibiting speci fic morphology compared to an industrial EBPVD TBC system. A “reference” YSZ material prepared by sol–gel route has been chosen for this investigation. This soft chemical process has already shown a real potential to make high purity nanocrystalline materials with a controlled morphology. Associated with dip-coating or any appropriate coating technique, this process allows producing ei- ther thin or thick ceramic coatings with a non-oriented microstructure

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Pt-modified Ni aluminides, MCrAlY-base multilayer coatings and TBC systems fabricated by Spark Plasma Sintering for the protection of Ni-base superalloys

Pt-modified Ni aluminides, MCrAlY-base multilayer coatings and TBC systems fabricated by Spark Plasma Sintering for the protection of Ni-base superalloys

cycles consist in fast heating by moving samples into the hot furnace, 1 h at high temperature (including heating), and fast cooling during 15 min under a high flow of clean air. Fig. 12 shows an example of a SPS processed TBC system after thermal cycling. This γ/γ′ based system is doped with Hf and Si. The TGO is composed of alumina with white precipitates of Hf-rich oxides. No internal oxidation is observed in this case, as has been observed for samples with higher dopant concentrations. First tests were performed at 1100 °C up to 300 cycles only. For some of the tested compositions, the SPS TBC system is still fully adherent, except at sample edges, as can be seen on Fig. 13 . Oxidation kinetics were evaluated from TGO thickness measurements on SEM cross sections. For example, a low mass γ/γ′ bondcoat fabricated with a single 2 μm thick Pt foil and a 60 nm Hf deposit shows a k p = 3E−7 mg²/cm 4 /s after 300 h. This value is closed to the
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Thermal cycling behavior of EBPVD TBC systems deposited on doped Pt-rich γ–γ′ bond coatings made by Spark Plasma Sintering (SPS)

Thermal cycling behavior of EBPVD TBC systems deposited on doped Pt-rich γ–γ′ bond coatings made by Spark Plasma Sintering (SPS)

4. Conclusion In conclusion, this study reports the ability of SPS to fabricate bond coatings on Ni-based superalloy for being used in a TBC system with an industrial standard YPSZ top coat coated by EBPVD. Even if the pollution analysis by GDMS technique shows quite high maximum contents in C, O and N, the good performances of these coatings under a cycling oxidation test of 1000×1h at 1100 °C under air reveal a good quality of the fabricated coatings. Indeed, the adherence of the ceramic top coat, highly sensitive to impurities segregation, is better for the γ–γ′ coatings made by SPS than for the conventional β-(Ni,Pt) Al made by the industrial vapour phase aluminization. This better adherence can be explained from a mechanical point of view as the Pt rich γ–γ′ coatings have a lower roughness after cyling. Moreover these samples are excellent alumina formers for up to 1000 cycles at 1100 °C but at that point some of the coatings present an Al content lower than the superalloy they protect. The life span of such coatings, on the superalloy AM1 ®, may not exceed largely 1000 cycles. However two samples fabricated from 10 μm of Pt and 2 or 4 μm of Al showed a high level of Al after 1000 h. Excellent behavior of sample A-2 can be related to Pt and Al addition, but also to a combination of RE including Hf, Y and possibly to a positive effect of Ag and Si. These coatings could be possibly improved by a higher level of RE doping in order to reduce their oxidation kinetics.
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The oxidation behavior of TBC with cold spray CoNiCrAlY bond coat

The oxidation behavior of TBC with cold spray CoNiCrAlY bond coat

Keywords cold spray, CoNiCrAlY, cracking, oxidation, TBC, TGO growth, thermal spray 1. Introduction In a thermal barrier coating (TBC) system, the metallic bond coat (BC) plays the role of enhancing the adhesion of the ceramic topcoat (TC) to the substrate and pro- tecting the substrate metal from oxidation and corrosion. When exposed at high temperatures, oxidation of the bond coat results in the formation of a thermally grown oxide (TGO) layer at the ceramic/bond coat interface. This layer acts as a diffusion barrier during the extended thermal exposure in service, thus protecting the substrate from further oxidation. However, growth of the TGO tends to increase the internal stress within the TBC system and causes cracking in the TC/BC interfacial region, which eventually leads to spallation of the topcoat (Ref 1 - 5 ).
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Characterization of TBC systems with NiPtAl or NiCoCrAlYTa bond coatings after thermal cycling at 1100°C: a comparative study of failure mechanisms

Characterization of TBC systems with NiPtAl or NiCoCrAlYTa bond coatings after thermal cycling at 1100°C: a comparative study of failure mechanisms

bond coating surface undulations and imperfections due to a convoluted TGO are then created [14]. Out of plane stresses develop and cracks nucleate around concave and convex areas, Fig.5b. The large fraction of BC surface observed suggests that these cracks go through the TGO in order to reach and propagate at the TGO/BC interface where the release of stored energy is more important [8]. Rumpling is then responsible for the failure of TBC systems with a NiPtAl BC even though this allows a decrease in the TGO elastic strain, as assumed by Tolpygo et al. [12]. Such failure path (cracks initiated at TGO/TC interface which propagate at TGO/BC interface) has already been observed by Tolpygo and Clarke on a TBC system composed of a René N5 superalloy and a Pt- modified nickel aluminide BC after thermal cycling [13].
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Step-by-step investigation of degradation mechanisms induced by CMAS attack on YSZ materials for TBC applications

Step-by-step investigation of degradation mechanisms induced by CMAS attack on YSZ materials for TBC applications

Our aim in this study is to describe the effects of CMAS on sol –gel YSZ materials exhibiting speci fic morphology compared to an industrial EBPVD TBC system. A “reference” YSZ material prepared by sol–gel route has been chosen for this investigation. This soft chemical process has already shown a real potential to make high purity nanocrystalline materials with a controlled morphology. Associated with dip-coating or any appropriate coating technique, this process allows producing ei- ther thin or thick ceramic coatings with a non-oriented microstructure

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Erosion and high temperature oxidation resistance of new coatings fabricated by a sol-gel route for a TBC application

Erosion and high temperature oxidation resistance of new coatings fabricated by a sol-gel route for a TBC application

Comparing the behaviour of the reference TBCs, it can be seen that the plasma sprayed TBC system erodes at a faster rate than its EB PVD counter part. In this study the steady state erosion rate of the plasma sprayed TBC is twice that of the EB PVD when impacted at 30° impact angle. The transient erosion behaviour is much greater with the erosion rate for the rougher plasma spray TBC 8 times that of the EB PVD system. This increased transient behaviour is thought to be due to the difference in the initial surface roughness of the two systems. Once a steady state erosion condition is established, the erosion performance of the two systems, at 30° impact, is much closer. Previous studies using this erosion rig at 90° impact angle [3] has shown that the erosion rate of a plasma sprayed and EB PVD TBC differ by a factor of 7 at room temperature with the EB PVD TBC having the lower erosion rate. For glancing angle impact, the erosion rate of EB PVD TBCs is known to depend on the difference in orientation of the impacting particle on the column growth, with a significant increase in the erosion rate for open EB PVD structures when this difference in orientation exceeds 58° [4].
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Cyclic thermogravimetry of TBC systems

Cyclic thermogravimetry of TBC systems

At 1100 °C, the oxidation kinetics of BCs are low enough so that very long experiments or very precise measurements are necessary. For a pure nickel-base alumina former, k p at 1100 °C is below 10 − 6 mg 2 /cm 4 /s. Then, the expected mass gain of a non-preoxidized sample is about 60 μg/cm2 during the first cycle, 3 μg/cm 2 during the 100th cycle and less than 1 μg/cm 2 during the 1000th cycle. During this study, it was shown that the Pt wire which is used to hang the specimen is losing weight because of evaporation. With the massive zirconia reference sample, the rate of mass loss due to evaporation was measured over 300 cycles and corresponds to a constant mass loss rate of 3.3 μg/cm 2 /cycle for a TBC sample. It appears that this value cannot be neglected in front of the mass gain due to oxidation so the NMC signal was corrected to take into account this phenomenon. For the SETARAM TAG24S thermobalance, Pt evaporation is not a problem because of the symmetrical arrangement. Fig. 3 is an enlargement of Fig. 2 during cycles 3 and 4 of TBC29. The mass gains due to oxidation during the high temperature dwells can be seen. Between these dwells, the mass varies due to buoyancy and convection. As explained in [1], it is possible to analyze only the mass recorded during high temperature dwells with no effect of buoyancy or convection. Indeed, it can be seen on Fig. 3 that the mass at the end of a high temperature dwell (point A) is equal to the mass at the beginning of the next high temperature dwell (point B). The overall NMC data of Fig. 2 are obtained by selecting the last point of each high temperature dwell. From these data, in cycle ranges without spalling event, k p can be calculated using the complete parabolic fitting procedure [13]. Results are given in Table 3.
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THI safety system

THI safety system

CONTROL Software is used to control and tune the beam. SAFETY SYSTEM Interceptive beam diagnostics are connected to test boards. Each board is able to inject a test signal (10µA) to the diagnostics and filter the signal from the device. Test signals can be sent by software. Each VME board (PFAIS) measures 4 diagnostic currents with logarithmic I/V converters, which generate a voltage proportional to the logarithm of the current. This voltage is digitised, compared to a threshold and numerically

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The Solar System

The Solar System

THE SOLAR SYSTEM Ken Tapping, 7 th November, 2017 The Solar System contains one star – the Sun, eight planets – Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune, and their satellites. There are very many asteroids, mostly orbiting the Sun between Mars and Jupiter. Beyond Neptune is a doughnut-shaped belt of icy objects ranging from too small to see to bodies like Pluto and Eris. This is known as the Kuiper Belt, and its members as “Kuiper Belt Objects”. Then, even further away, where the Sun just looks like a bright star, and it is very cold, lies the Solar System’s “deep freeze”. It contains millions of frozen fragments of construction material left over after the Sun, planets and other bodies formed. On occasion, a collision sends one of these fragments onto a new course, taking it into the inner parts of the Solar System, where the Sun evaporates its material, forming a comet.
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Building as a system.

Building as a system.

Its sizes and characteristics are defined by its location within the building. Following this thought, the cores were designed as a system of growth with interchangeable elem[r]

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GANIL RF system

GANIL RF system

The same studies have been made on the 1 : 4 model as for the SSC resonators, Compared with the calcu- lations, minor modifications have been included in the stem length an[r]

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Designing resource-aware distriubted system based on system level containers

Designing resource-aware distriubted system based on system level containers

4 Goal and Objectives The goal of this tutorial is to provide the fundamentals of our Squirel framework which mainly provide a way to perform resource reservation on a modern com- ponent based framework named Kevoree [1][3]. Kevoree is a framework language for designing heterogeneous and distributed adaptive applications. Squirel [2] also relies on system level container such as LXC to ensure the resource reser- vation during the system runtime. The goal of this tutorial is to present Squirel through a practical session to a wide number of Software Engineering practi- tioners. This event would be a great venue for people to learn-by-example about resource aware development and deployement, in a modern component based framework. This tutorial is also intended to be a privileged moment to collect comments and feedback on our approach and realizations. This overall goal can be broken down into several concrete sub-objectives:
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Information System Techniques

Information System Techniques

Mastère IST (Information System Techniques ) Le Mastère IST est un mastère de l’ENIT qui fait l’objet de coopération entre l’Université Tunis Al Manar avec l’Université Technique de Braunschweig en Allemagne. Le mastère IST est ouvert pour les candidats ayant au moins le niveau M1 (2ème Année Ingénieur ou plus, réussite en M1 ou équivalent) dans les spécialités GE, INFO et TELECOM.

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Cardiovascular System Studies

Cardiovascular System Studies

Our research is concerned mainly with the quantitative description and mathematical simulation of the biological control system involved with the regulation of blood [r]

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National innovation system: the system approach in historical perspective

National innovation system: the system approach in historical perspective

Over the period 1960-1992, one of the OECD study that most explicitly carried a system approach was The Research System, published in three volumes between 1972 and 1974 under the direction of Jean-Jacques Salomon. The study looked at the research system in ten countries, large and small: organization, financing, application of science (or innovation), government research, university-industry relations, international dimensions, foundations. 54 Because research is not an autonomous system, so said the authors, the document “put emphasis on the institutional context in which research is conducted. One of the most delicate problem of science policy is how to influence the process by which scientific discoveries are transformed into useful applications and how to contribute, in some way or another, towards bringing the supply of science into closer harmony with the demand of society. 55 “The whole problem of university research consists in the break-up of its institutional framework (…). 56
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Marine icing system modifications to system 2

Marine icing system modifications to system 2

components remain live even though the system is not running. The switch was rewired into the hot line to address this issue. The next problem that arose was that all the overcurrent protection circuitry was located on the secondary side of the power supply. There was no such protection on the primary side of the power enclosure, and a fault in the primary could cause a fire within the enclosure. Fusing the hot and neutral input lines of the power enclosure solved this problem.

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Building as a system.

Building as a system.

THE SLAB STRUCTURE WAS COMPOSED OF THE PRECAST VERTICAL MEMBERS CONSISTING OF FOUR DIFFERENT. SIZES AND SHAPES, THE PRECAST SLAB PANELS AND THE TOPPING SLAB[r]

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