scholarly journals Capturing the Competing Influence of Thermal and Mechanical Loads on the Strain of Turbine Blade Coatings via High Energy X-rays

Coatings ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 320 ◽  
Author(s):  
Albert Manero ◽  
Kevin Knipe ◽  
Janine Wischek ◽  
Carla Meid ◽  
John Okasinski ◽  
...  
Keyword(s):  
High Temperature ◽  
Physical Vapor Deposition ◽  
Mechanical Load ◽  
High Energy ◽  
Thermally Grown Oxide ◽  
Air Cooling ◽  
Internal Cooling ◽  
X Rays ◽  
Design Strategies ◽  
Barrier Coating

This paper presents findings of synchrotron diffraction measurements on tubular specimens with a thermal barrier coating (TBC) system applied by electron beam physical vapor deposition (EB-PVD), having a thermally grown oxide (TGO) layer due to aging in hot air. The diffraction measurements were in situ while applying a thermal cycle with high temperature holds at 1000 °C and varying internal air cooling mass flow and mechanical load. It was observed that, during high temperature holds at 1000 °C, the TGO strain approached zero if no mechanical load or internal cooling was applied. When applying a mechanical load, the TGO in-plane strain (e22) changed to tensile and the out of plane TGO strain (e11) became compressive. The addition of internal cooling induced a thermal gradient, yielding a competing effect, driving the e22 strain to compressive and e11 strain to tensile. Quantifying TGO strain variations in response to competing factors will provide a path to controlling the TGO strain, and further improving the lifetime assessment and durability design strategies for TBC systems.

Delamination toughness of electron beam physical vapor deposition (EB-PVD) Y2O3–ZrO2 thermal barrier coatings by the pushout method: Effect of thermal cycling temperature

2008 ◽  
Vol 23 (9) ◽  
pp. 2382-2392 ◽  
Author(s):  
M. Tanaka ◽  
Y.F. Liu ◽  
S.S. Kim ◽  
Y. Kagawa
Keyword(s):  
Electron Beam ◽  
Thermal Cycling ◽  
Bond Coat ◽  
Physical Vapor Deposition ◽  
Thermally Grown Oxide ◽  
Test Method ◽  
Thermal Barrier ◽  
Barrier Coating ◽  
Delamination Toughness ◽  
Cycling Temperature

A pushout test method was used to quantify effect of thermal cycling temperatures on the delamination toughness of an electron beam physical vapor deposited thermal barrier coating (EB-PVD TBC). The delamination toughness, Γi, was related to the maximum thermal cycling temperature, Th, equal to 1000, 1025, 1050, and 1100 °C. The measured delamination toughness varied from 9 to 95 J/m2. At Th = 1000 °C, Γi attained a maximum value, larger than that of the as-deposited sample and decreasing with increased Th. During the thermal cycling tests, the thermally grown oxide (TGO) was formed between the TBC and the bond coat deposited onto the superalloy substrate. Inside the TGO layer, mixture of Al2O3 and ZrO2 oxides was observed close to the TBC side with nearly pure Al2O3 phases close to the bond-coat side. During the pushout test, delamination occurred at the interface of the mixture and pure Al2O3 layer with an exception for Th = 1100 °C specimens where delamination also occurred at the interface between the TGO and bond-coat layers. The effect of thermal cycling temperatures on the delamination toughness is discussed in terms of the microstructural change and delamination behavior.

scholarly journals Estimation of Spalling Stress in Thermal Barrier Coating Using High Energy X-Rays from Synchrotron

2004 ◽  
Vol 70 (693) ◽  
pp. 724-730 ◽  
Author(s):  
Kenji SUZUKI ◽  
Keisuke TANAKA ◽  
Yoshiaki AKINIWA ◽  
Masashi KAWAMURA ◽  
Koji NISHIO ◽  
...  
Keyword(s):  
Thermal Barrier Coating ◽  
High Energy ◽  
Thermal Barrier ◽  
X Rays ◽  
Barrier Coating

Development of ODS Coating for High Temperature Turbine Components Using DED Additive Manufacturing

2018 ◽  
Author(s):  
Eric Chia ◽  
Bruce S. Kang ◽  
Min Zheng ◽  
Yang Li ◽  
Minking Chyu
Keyword(s):  
High Temperature ◽  
Additive Manufacturing ◽  
Gas Turbine ◽  
Thermally Grown Oxide ◽  
Combined Cycle ◽  
Inlet Temperature ◽  
Internal Cooling ◽  
Test Results ◽  
Dispersion Strengthening ◽  
Thermal Cycles

Current and future designs for advanced turbine systems, such as Integrated Gasification Combined Cycle (IGCC), advanced Natural Gas Combined Cycle (NGCC), and the emerging supercritical CO2 (SCO2) systems require increasing turbine inlet temperature (TIT), which is well beyond the substrate melting temperature. The well-known approach is coating the turbine blade with thermal barrier coatings (TBC) combined with internal cooling channel in the substrate. However, due to thermally grown oxide (TGO) and thermal expansion mismatch stresses, TBC spallation failure is a major concern. Furthermore, neither the ceramic coating layer nor the metallic bond coat in current TBC system can provide structural support to house the internal cooling channels. In this research, a method to fabricate high temperature protective structural coating on top of critical gas turbine components by additive manufacturing (AM) technique using oxide dispersion strengthening (ODS) metal powder is presented. A novel combined mechanochemical bonding (MCB) plus ball milling process is utilized to produce near spherical and uniformly alloyed ODS powders. AM-processed ODS coating by direct energy deposition (DED) method on MAR-247 substrate, with laser powers from 100W to 200W were carried out. The ODS coated samples were then subjected to thermal cyclic loadings for over 2200 cycles. For comparison, in our earlier studies, under the same cyclic testing condition, typical tested TBC coupons showed spallation failure after ∼400 cycles. Correlation of the measured ODS coating Young’s modulus using a unique non-destructive micro-indentation testing method with evolution of the ODS microstructures are studied to identify optimum AM processing parameters for best performance of the ODS samples. In particular, stability of secondary γ′ phase in the ODS coating after thermal cycles is analyzed. Test results revealed a thin steady durable alpha alumina oxide layer on the best performance ODS samples. After 2,200 thermal cycles, strong bonding at ODS/substrate interface is also maintained for most of the ODS coated samples. Test results also showed stable substrate microstructure due to the protective ODS coating even after 2,200 thermal cycles. These preliminary test results showed strong potential for applications of AM-assisted ODS coating on advanced gas turbine components.

Environmental Barrier Coating Oxidation and Adhesion Strength

2020 ◽  
Author(s):  
Bryan J. Harder ◽  
Michael J. Presby ◽  
Jon A. Salem ◽  
Steven M. Arnold ◽  
Subodh K. Mital
Keyword(s):  
Adhesion Strength ◽  
Physical Vapor Deposition ◽  
Ceramic Matrix Composites ◽  
Thermally Grown Oxide ◽  
Matrix Composites ◽  
X Ray Diffraction ◽  
Environmental Barrier Coatings ◽  
Environmental Barrier ◽  
Barrier Coating ◽  
Coating Durability

Abstract Plasma Spray-Physical Vapor Deposition (PS-PVD) environmental barrier coatings (EBCs) of Yb2Si2O7 were deposited on SiC and exposed in a steam environment (90% H2O/O2) at 1426°C to form a thermally grown oxide (TGO) layer between the substrate and EBC. In advanced ceramic material systems such as coated ceramic matrix composites (CMCs), the TGO layer is the weak interface in coated CMC systems and directly influences component lifetimes. The effect of surface roughness and TGO thickness on the adhesion strength were evaluated by mechanical testing of the coatings after exposure. Morphology and oxide layer thickness were analyzed with electron microscopy while the composition and crystal structure were tracked with X-ray diffraction. The strength of the system is evaluated with respect to oxidation rate to give a qualitative understanding of coating durability.

The Effects of Yttrium on the Tensile and Creep Behavior of Thermally Grown Oxide at High Temperature

2006 ◽  
Author(s):  
G. D. Ko ◽  
S. K. Sun ◽  
K. J. Kang
Keyword(s):  
High Temperature ◽  
Mechanical Behavior ◽  
Thermal Barrier Coating ◽  
Creep Behavior ◽  
Thermally Grown Oxide ◽  
Thermal Barrier ◽  
Barrier Coating ◽  
Different Levels ◽  
Thermally Grown

Recently, It has been revealed that TGO(thermally grown oxide) plays important roles on durability of TBC(thermal barrier coating) systems. In this work, Fecralloy foils were chosen as the substrates which form TGO on the surface at high temperature and the tensile and creep experiments were performed with the thick foils 100 μm at 1200°C. During the experiments the load, displacement and the TGO thickness were monitored in-situ. The effect of Yttrium on the mechanical behavior was investigated using the specimens with two different levels of the concentration. As the results, it was found that Yttrium enhances the strength of TGO as well as that of the substrate at the high temperature.

Spalling Stress in Oxidized Thermal Barrier Coatings Evaluated by X-Ray Diffraction Method

2005 ◽  
Vol 490-491 ◽  
pp. 631-636 ◽  
Author(s):  
Kenji Suzuki ◽  
Keisuke Tanaka
Keyword(s):  
Thermal Barrier Coatings ◽  
Plane Stress ◽  
Stress Measurement ◽  
Diffraction Method ◽  
High Energy ◽  
Thermally Grown Oxide ◽  
Thermal Barrier ◽  
X Rays ◽  
Barrier Coatings ◽  
X Ray

The spallation of thermal barrier coatings (TBCs) is promoted by thermally grown oxide (TGO). To improve TBCs, it is very important to understand the influence of TGO on the spalling stress. In this study ,the TBCs were oxidized at 1373 K for four diferent periods: 0, 500,1000 and 2000 h. The distribution of the in-plane stress in oxidized TBCs, s1, was obtained by repeating the X-ray stress measurement with low energy X-rays after successive removal of the surface layer. The distribution of the out-of-plane stress, s1− s3, was measured with hard synchrotron X-rays, because high energry X-rays have a large penetration depth. From the results by the low and high energy Xrays, the spalling stress in the oxidized TBCs, s3, was evaluated. The evaluated value of the spalling stress for the oxidized TBC was a small tension beneath the surface, but steeply increased near the interface between the top and bond coating. This large tensile stress near the interface is responsible for the spalling of the top coating.

scholarly journals In situ temperature profile measurements with high-energy X-rays as a probe of optical floating zone crystal growth environment

2020 ◽  
Vol 53 (4) ◽  
pp. 982-990
Author(s):  
Jonathan J. Denney ◽  
Yusu Wang ◽  
Adam A. Corrao ◽  
Guanglong Huang ◽  
David Montiel ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Growth Process ◽  
High Energy ◽  
Air Cooling ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
X Rays ◽  
Floating Zone ◽  
Growth Environment ◽  
Crystal Growth Process

The ability of optical floating zone (OFZ) furnaces to rapidly produce large single crystals of complex emerging materials has had a transformative effect on many scientific fields that require samples of this type. However, the crystal growth process within the OFZ furnace is not well understood owing to the challenges involved in monitoring the high-temperature crystal growth process. Novel beamline-compatible optical furnaces that approximate the inhomogeneous growth environment within an OFZ furnace have been fabricated and tested in high-energy synchrotron beamlines. It is demonstrated that temperature profiles can be effectively extracted from powder diffraction data collected on polycrystalline ceramic rods heated at their tip. Furthermore, these measured temperature profiles can be accurately reproduced using a heat-transfer model that accounts for solid-state thermal conduction, partial sample lamp power absorption, convective air cooling and radiative cooling, allowing key thermal parameters such as thermal conductivity to be extracted from experimental data.

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