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Maurice Gell - One of the best experts on this subject based on the ideXlab platform.

  • formation of vertical cracks in solution precursor plasma sprayed Thermal Barrier Coatings
    Surface & Coatings Technology, 2006
    Co-Authors: L Xie, A Oztürk, Eric H. Jordan, B. Cetegen, Dianying Chen, Maurice Gell
    Abstract:

    When tailored to make durable Thermal Barrier Coatings (TBCs), the Solution Precursor Plasma Spray (SPPS) process produces a microstructure containing uniformly vertical cracks. These cracks provide a high degree of strain tolerance to the ceramic top coat. In order to understand the formation of vertical crack in SPPS process, Coatings of various thicknesses were deposited on a variety of substrates with vastly different Thermal properties. These Coatings were characterized in the as-sprayed state and after heat treatment. It has been determined that the tensile stress derived from the pyrolysis of precursor occurring during coating deposition or post heat-treatment is the major driving force for the formation of vertical cracks in SPPS TBCs.

  • remaining life prediction of Thermal Barrier Coatings based on photoluminescence piezospectroscopy measurements
    Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2006
    Co-Authors: Eric H. Jordan, Maurice Gell
    Abstract:

    Remaining Life Prediction of Thermal Barrier Coatings Based on Photoluminescence Piezospectroscopy Measurements Nondestructive determination of the remaining life of Thermal Barrier Coatings (TBCs) is highly desirable for components removed from service engines. Remaining life predictions for EB-PVD/Pt-Al TBCs cycled at two temperatures (1151 °C and 1121 °C) were made based on the Thermally grown oxide stresses measured by the photoluminescence piezospectroscopy technique without knowing the test temperature. The predictions were compared using regression methods and neural network methods. It was found that both methods produce accurate life remaining predictions, but the neural network methods were superior. The lowest root-mean-square (rms) error and maximum absolute error for the prediction was 6.1% and 8.2%, respectively. For a data set with a 48.7% rms spallation life variation about the mean, the prediction results obtained are highly encouraging.

  • low Thermal conductivity plasma sprayed Thermal Barrier Coatings with engineered microstructures
    Acta Materialia, 2006
    Co-Authors: Amol D Jadhav, Eric H. Jordan, Maurice Gell, Nitin P Padture, P Miranzo, Edwin R Fuller
    Abstract:

    Abstract The solution precursor plasma spray (SPPS) process has been used to deposit ZrO 2 –7 wt.% Y 2 O 3 Thermal Barrier Coatings (TBCs) that contain alternate layers of low and high porosities (layered-SPPS). The Thermal conductivity of the layered-SPPS coating is found to be lower than those of both a SPPS coating with distributed porosity and an air-plasma-sprayed coating of the same composition, in the temperature range 100–1000 °C. Analytical and object-oriented finite element (OOF) models have been used to analyze the experimental Thermal conductivity data. The OOF model is better at describing the experimentally measured Thermal conductivities than the analytical model, and the OOF model captures accurately the effect of real microstructures on the Thermal conductivities of these plasma-sprayed TBCs.

  • Superior Thermal Barrier Coatings Using Solution Precursor Plasma Spray
    Journal of Thermal Spray Technology, 2004
    Co-Authors: Eric H. Jordan, T.d Xiao, A Oztürk, J. Roth, Maurice Gell, B. Cetegen, L Xie, Nitin P Padture, P.E.C. Bryant
    Abstract:

    A novel process, solution precursor plasma spray (SPPS), is presented for depositing Thermal Barrier Coatings (TBCs), in which aqueous chemical precursors are injected into a standard direct current plasma spray system. The resulting Coatings microstructure has three unique features: (1) ultra fine splats (1 mum), (2) nanometer and micron-sized interconnected porosity, and (3) closely spaced, through-thickness cracks. Coatings over 3 mm thick can be readily deposited using the SPPS process. Coating durability is excellent, with SPPS Coatings showing, in furnace cycling tests, 2.5 times the spallation life of air plasma Coatings (APS) and 1.5 times the life of electron beam physical vapor deposited (EB-PVD) Coatings. The conductivity of SPPS Coatings is lower than EB-PVD Coatings and higher than the best APS Coatings. Manufacturing cost is expected to be similar to APS Coatings and much lower than EB-PVD Coatings. The SPPS deposition process includes droplet break-up and material arriving at the deposition surface in various physical states ranging from aqueous solution, gel phase, to fully-molten ceramic. The relation between the arrival state of the material and the microstructure is described.

  • ceramic materials for Thermal Barrier Coatings
    Journal of The European Ceramic Society, 2004
    Co-Authors: Nitin P Padture, Maurice Gell, Paul G. Klemens
    Abstract:

    A method for identifying ceramics suitable for use as Thermal Barrier Coatings is presented, based on parameters associated with Thermal conductivity, oxygen diffusivity, Thermal expansion coefficient, maximum temperature capability, hardness, elastic modulus, density, and chemical reactivity. A ceramic Thermal Barrier coating and method of manufacture is further presented, the ceramic comprising yttrium aluminum garnet (Y3 Al5 O12, or YAG)-based ceramics. Such ceramics are based on yttrium aluminum garnet or other ceramics with the garnet structure and alloys thereof. The ceramics in accordance with the present invention have low Thermal conductivity, and are more potentially durable than prior art zirconia based ceramics.

Per Nylen - One of the best experts on this subject based on the ideXlab platform.

Nitin P Padture - One of the best experts on this subject based on the ideXlab platform.

  • Thermal-Barrier Coatings for more efficient gas-turbine engines
    MRS Bulletin, 2012
    Co-Authors: D.r. Clarke, Matthias Oechsner, Nitin P Padture
    Abstract:

    Gas-turbine engines used in transportation, energy, and defense sectors rely on high-temperature Thermal-Barrier Coatings (TBCs) for improved effi ciencies and power. The promise of still higher effi ciencies and other benefi ts is driving TBCs research and development worldwide. An introduction to TBCs—complex, multi-layer evolving systems—is presented, where these fascinating systems touch on several known phenomena in materials science and engineering. Critical elements identifi ed as being important to the development of future TBCs form the basis for the fi ve articles in this issue of MRS Bulletin . These articles are introduced, together with a discussion of the major challenges to improved coating development and the rich opportunities for materials research they provide.

  • low Thermal conductivity plasma sprayed Thermal Barrier Coatings with engineered microstructures
    Acta Materialia, 2006
    Co-Authors: Amol D Jadhav, Eric H. Jordan, Maurice Gell, Nitin P Padture, P Miranzo, Edwin R Fuller
    Abstract:

    Abstract The solution precursor plasma spray (SPPS) process has been used to deposit ZrO 2 –7 wt.% Y 2 O 3 Thermal Barrier Coatings (TBCs) that contain alternate layers of low and high porosities (layered-SPPS). The Thermal conductivity of the layered-SPPS coating is found to be lower than those of both a SPPS coating with distributed porosity and an air-plasma-sprayed coating of the same composition, in the temperature range 100–1000 °C. Analytical and object-oriented finite element (OOF) models have been used to analyze the experimental Thermal conductivity data. The OOF model is better at describing the experimentally measured Thermal conductivities than the analytical model, and the OOF model captures accurately the effect of real microstructures on the Thermal conductivities of these plasma-sprayed TBCs.

  • Superior Thermal Barrier Coatings Using Solution Precursor Plasma Spray
    Journal of Thermal Spray Technology, 2004
    Co-Authors: Eric H. Jordan, T.d Xiao, A Oztürk, J. Roth, Maurice Gell, B. Cetegen, L Xie, Nitin P Padture, P.E.C. Bryant
    Abstract:

    A novel process, solution precursor plasma spray (SPPS), is presented for depositing Thermal Barrier Coatings (TBCs), in which aqueous chemical precursors are injected into a standard direct current plasma spray system. The resulting Coatings microstructure has three unique features: (1) ultra fine splats (1 mum), (2) nanometer and micron-sized interconnected porosity, and (3) closely spaced, through-thickness cracks. Coatings over 3 mm thick can be readily deposited using the SPPS process. Coating durability is excellent, with SPPS Coatings showing, in furnace cycling tests, 2.5 times the spallation life of air plasma Coatings (APS) and 1.5 times the life of electron beam physical vapor deposited (EB-PVD) Coatings. The conductivity of SPPS Coatings is lower than EB-PVD Coatings and higher than the best APS Coatings. Manufacturing cost is expected to be similar to APS Coatings and much lower than EB-PVD Coatings. The SPPS deposition process includes droplet break-up and material arriving at the deposition surface in various physical states ranging from aqueous solution, gel phase, to fully-molten ceramic. The relation between the arrival state of the material and the microstructure is described.

  • ceramic materials for Thermal Barrier Coatings
    Journal of The European Ceramic Society, 2004
    Co-Authors: Nitin P Padture, Maurice Gell, Paul G. Klemens
    Abstract:

    A method for identifying ceramics suitable for use as Thermal Barrier Coatings is presented, based on parameters associated with Thermal conductivity, oxygen diffusivity, Thermal expansion coefficient, maximum temperature capability, hardness, elastic modulus, density, and chemical reactivity. A ceramic Thermal Barrier coating and method of manufacture is further presented, the ceramic comprising yttrium aluminum garnet (Y3 Al5 O12, or YAG)-based ceramics. Such ceramics are based on yttrium aluminum garnet or other ceramics with the garnet structure and alloys thereof. The ceramics in accordance with the present invention have low Thermal conductivity, and are more potentially durable than prior art zirconia based ceramics.

  • failure modes in plasma sprayed Thermal Barrier Coatings
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2003
    Co-Authors: Kevin W Schlichting, Eric H. Jordan, Nitin P Padture, Maurice Gell
    Abstract:

    Commercial plasma-sprayed Thermal Barrier Coatings (TBCs) were investigated in an effort to elucidate the failure modes during Thermal-cycling. Residual stresses in the Thermally grown oxide (TGO) was measured using the Cr3+ photoluminescence piezo-spectroscopy (PLPS) method and the microstructures of the TBCs were characterized as a function of Thermal cycles. The average residual stress in the TGO was found to be of the order of 1 GPa. The average Thermal-cyclic life of the TBCs was found to be ∼350 cycles. Microstructural observations revealed that as the TGO thickened, cracking occurred at the bond-coat/TGO interface, and in some instances cracking also occurred at the TGO/top-coat interface, but primarily at crests of bond-coat undulations. The bond-coat-TGO separation resulted in ‘layering’ of the TGO at crests due to enhanced TGO thickening in those regions. In the troughs of bond-coat undulations, cracking occurred within the top-coat when the TGO was thick. Thus, the primary failure modes in these TBCs were: (i) cracking of the bond-coat/TGO interface; (ii) cracking within the top-coat; and (iii) linking of these microcracks by fracture of the TGO. A semi-quantitative failure model has been used to rationalize some of the observed cracking modes. Based on this analysis some suggestions are made for improving TBC durability.

Nicolaie Markocsan - One of the best experts on this subject based on the ideXlab platform.

Eric H. Jordan - One of the best experts on this subject based on the ideXlab platform.

  • formation of vertical cracks in solution precursor plasma sprayed Thermal Barrier Coatings
    Surface & Coatings Technology, 2006
    Co-Authors: L Xie, A Oztürk, Eric H. Jordan, B. Cetegen, Dianying Chen, Maurice Gell
    Abstract:

    When tailored to make durable Thermal Barrier Coatings (TBCs), the Solution Precursor Plasma Spray (SPPS) process produces a microstructure containing uniformly vertical cracks. These cracks provide a high degree of strain tolerance to the ceramic top coat. In order to understand the formation of vertical crack in SPPS process, Coatings of various thicknesses were deposited on a variety of substrates with vastly different Thermal properties. These Coatings were characterized in the as-sprayed state and after heat treatment. It has been determined that the tensile stress derived from the pyrolysis of precursor occurring during coating deposition or post heat-treatment is the major driving force for the formation of vertical cracks in SPPS TBCs.

  • remaining life prediction of Thermal Barrier Coatings based on photoluminescence piezospectroscopy measurements
    Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2006
    Co-Authors: Eric H. Jordan, Maurice Gell
    Abstract:

    Remaining Life Prediction of Thermal Barrier Coatings Based on Photoluminescence Piezospectroscopy Measurements Nondestructive determination of the remaining life of Thermal Barrier Coatings (TBCs) is highly desirable for components removed from service engines. Remaining life predictions for EB-PVD/Pt-Al TBCs cycled at two temperatures (1151 °C and 1121 °C) were made based on the Thermally grown oxide stresses measured by the photoluminescence piezospectroscopy technique without knowing the test temperature. The predictions were compared using regression methods and neural network methods. It was found that both methods produce accurate life remaining predictions, but the neural network methods were superior. The lowest root-mean-square (rms) error and maximum absolute error for the prediction was 6.1% and 8.2%, respectively. For a data set with a 48.7% rms spallation life variation about the mean, the prediction results obtained are highly encouraging.

  • low Thermal conductivity plasma sprayed Thermal Barrier Coatings with engineered microstructures
    Acta Materialia, 2006
    Co-Authors: Amol D Jadhav, Eric H. Jordan, Maurice Gell, Nitin P Padture, P Miranzo, Edwin R Fuller
    Abstract:

    Abstract The solution precursor plasma spray (SPPS) process has been used to deposit ZrO 2 –7 wt.% Y 2 O 3 Thermal Barrier Coatings (TBCs) that contain alternate layers of low and high porosities (layered-SPPS). The Thermal conductivity of the layered-SPPS coating is found to be lower than those of both a SPPS coating with distributed porosity and an air-plasma-sprayed coating of the same composition, in the temperature range 100–1000 °C. Analytical and object-oriented finite element (OOF) models have been used to analyze the experimental Thermal conductivity data. The OOF model is better at describing the experimentally measured Thermal conductivities than the analytical model, and the OOF model captures accurately the effect of real microstructures on the Thermal conductivities of these plasma-sprayed TBCs.

  • Superior Thermal Barrier Coatings Using Solution Precursor Plasma Spray
    Journal of Thermal Spray Technology, 2004
    Co-Authors: Eric H. Jordan, T.d Xiao, A Oztürk, J. Roth, Maurice Gell, B. Cetegen, L Xie, Nitin P Padture, P.E.C. Bryant
    Abstract:

    A novel process, solution precursor plasma spray (SPPS), is presented for depositing Thermal Barrier Coatings (TBCs), in which aqueous chemical precursors are injected into a standard direct current plasma spray system. The resulting Coatings microstructure has three unique features: (1) ultra fine splats (1 mum), (2) nanometer and micron-sized interconnected porosity, and (3) closely spaced, through-thickness cracks. Coatings over 3 mm thick can be readily deposited using the SPPS process. Coating durability is excellent, with SPPS Coatings showing, in furnace cycling tests, 2.5 times the spallation life of air plasma Coatings (APS) and 1.5 times the life of electron beam physical vapor deposited (EB-PVD) Coatings. The conductivity of SPPS Coatings is lower than EB-PVD Coatings and higher than the best APS Coatings. Manufacturing cost is expected to be similar to APS Coatings and much lower than EB-PVD Coatings. The SPPS deposition process includes droplet break-up and material arriving at the deposition surface in various physical states ranging from aqueous solution, gel phase, to fully-molten ceramic. The relation between the arrival state of the material and the microstructure is described.

  • failure modes in plasma sprayed Thermal Barrier Coatings
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2003
    Co-Authors: Kevin W Schlichting, Eric H. Jordan, Nitin P Padture, Maurice Gell
    Abstract:

    Commercial plasma-sprayed Thermal Barrier Coatings (TBCs) were investigated in an effort to elucidate the failure modes during Thermal-cycling. Residual stresses in the Thermally grown oxide (TGO) was measured using the Cr3+ photoluminescence piezo-spectroscopy (PLPS) method and the microstructures of the TBCs were characterized as a function of Thermal cycles. The average residual stress in the TGO was found to be of the order of 1 GPa. The average Thermal-cyclic life of the TBCs was found to be ∼350 cycles. Microstructural observations revealed that as the TGO thickened, cracking occurred at the bond-coat/TGO interface, and in some instances cracking also occurred at the TGO/top-coat interface, but primarily at crests of bond-coat undulations. The bond-coat-TGO separation resulted in ‘layering’ of the TGO at crests due to enhanced TGO thickening in those regions. In the troughs of bond-coat undulations, cracking occurred within the top-coat when the TGO was thick. Thus, the primary failure modes in these TBCs were: (i) cracking of the bond-coat/TGO interface; (ii) cracking within the top-coat; and (iii) linking of these microcracks by fracture of the TGO. A semi-quantitative failure model has been used to rationalize some of the observed cracking modes. Based on this analysis some suggestions are made for improving TBC durability.