scholarly journals The Effect of Coating Composition and Geometry on TBC Lifetime

2017 ◽  
Author(s):  
Bruce A. Pint ◽  
Michael J. Lance ◽  
J. Allen Haynes
Keyword(s):  
Gas Turbines ◽  
Average Lifetime ◽  
Air Plasma ◽  
Bond Coatings ◽  
Bond Coating ◽  
Negative Effect ◽  
Plasma Sprayed ◽  
Oxygen Fuel ◽  
Thermally Sprayed ◽  
Tbc Lifetime

Several factors are being investigated that affect the performance of thermal barrier coatings (TBC) for use in land-based gas turbines where coatings are mainly thermally sprayed. This study examined high velocity oxygen fuel (HVOF), air plasma sprayed (APS) and vacuum plasma sprayed (VPS) MCrAlYHfSi bond coatings with APS YSZ top coatings at 900°–1100°C. For superalloy 247 substrates and VPS coatings tested in 1-h cycles at 1100°C, removing 0.6wt.%Si had no effect on average lifetime in 1-h cycles at 1100°C, but adding 0.3%Ti had a negative effect. Rod specimens were coated with APS, HVOF and HVOF with an outer APS layer bond coating and tested in 100-h cycles in air+10%H2O at 1100°C. With an HVOF bond coating, initial results indicate that 12.5 mm diameter rod specimens have much shorter 100-h cycle lifetimes than disk specimens. Longer lifetimes were obtained when the bond coating had an inner HVOF layer and outer APS layer.

scholarly journals The Effect of Coating Composition and Geometry on Thermal Barrier Coatings Lifetime

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Bruce A. Pint ◽  
Michael J. Lance ◽  
J. Allen Haynes
Keyword(s):  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Average Lifetime ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Bond Coatings ◽  
Bond Coating ◽  
Negative Effect ◽  
Plasma Sprayed

Several factors are being investigated that affect the performance of thermal barrier coatings (TBC) for use in land-based gas turbines where coatings are mainly thermally sprayed. This study examined high velocity oxygen fuel (HVOF), air plasma-sprayed (APS), and vacuum plasma-sprayed (VPS) MCrAlYHfSi bond coatings with APS YSZ top coatings at 900–1100 °C. For superalloy 247 substrates and VPS coatings tested in 1 h cycles at 1100 °C, removing 0.6 wt %Si had no effect on average lifetime in 1 h cycles at 1100 °C, but adding 0.3%Ti had a negative effect. Rod specimens were coated with APS, HVOF, and HVOF with an outer APS layer bond coating and tested in 100 h cycles in air + 10%H2O at 1100 °C. With an HVOF bond coating, initial results indicate that 12.5 mm diameter rod specimens have much shorter 100 h cycle lifetimes than disk specimens. Much longer lifetimes were obtained when the bond coating had an inner HVOF layer and outer APS layer.

scholarly journals Effect of APS Flash Bond Coatings on Furnace Cycle Lifetime of Disks and Rods

2019 ◽  
Author(s):  
Bruce A. Pint ◽  
Michael J. Lance ◽  
J. Allen Haynes ◽  
Edward J. Gildersleeve ◽  
Sanjay Sampath
Keyword(s):  
Crack Formation ◽  
Thermal Barrier ◽  
High Velocity Oxygen Fuel ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Bond Coatings ◽  
Bond Coating ◽  
Coating Roughness ◽  
Plasma Sprayed ◽  
Oxygen Fuel

Abstract Air plasma sprayed (APS) flash coatings on high velocity oxygen fuel (HVOF) bond coatings are well known to extend the lifetime of thermal barrier coatings. Recent work compared flash coatings of NiCoCrAlY and NiCoCrAlYHfSi applied to both rods and disk substrates of alloy 247. For rod specimens, 100-h cycles were used at 1100°C in wet air. Both flash coatings significantly improved the lifetime compared to HVOF-only and VPS-only MCrAlY bond coatings with no statistical difference between the two flash coatings. For disk specimens tested in 1-h cycles at 1100°C in wet air, the NiCoCrAlY flash coating significantly outperformed an HVOF-only NiCoCrAlYHfSi bond coating and a NiCoCrAlYHfSi flash coating. The flash coatings formed a mixed oxide-metal zone that appeared to inhibit crack formation and extend lifetime. In addition to the flash coating increasing the bond coating roughness, the underlying HVOF layer acted as a source of Al for this intermixed zone and prevented the oxide from penetrating deeper into the bond coating. The lower Y+Hf level in the Y-only flash coating appeared to minimize oxidation in the flash layer, thereby increasing the benefit compared to a NiCoCrAlYHfSi flash coating.

The Effect of Environment on TBC Lifetime

2015 ◽  
Author(s):  
Bruce A. Pint ◽  
Kinga A. Unocic ◽  
J. Allen Haynes
Keyword(s):  
Water Vapor ◽  
Carbon Capture ◽  
Air Plasma ◽  
Combustion Gas ◽  
Bond Coatings ◽  
Barrier Coating ◽  
Coating Failure ◽  
Negative Effect ◽  
Plasma Sprayed ◽  
Tbc Lifetime

While the water vapor content of the combustion gas in natural gas-fired land based turbines is ∼10%, it can be 20–85% with coal-derived (syngas or H2) fuels or innovative turbine concepts for more efficient carbon capture. Additional concepts envisage working fluids with high CO2 contents to facilitate carbon capture and sequestration. To investigate the effects of changes in the gas composition on thermal barrier coating (TBC) lifetime, furnace cycling tests (1 and 100h cycles) were performed in air with 10, 50 and 90 vol.% water vapor and CO2-10%H2O and compared to prior results in dry air or O2. Two types of TBC’s were investigated: (1) diffusion bond coatings (Pt diffusion or Pt-modified aluminide) with commercial electron-beam physical vapor-deposited yttria-stabilized zirconia (YSZ) top coatings on second-generation superalloy N5 and N515 substrates and (2) high velocity oxygen fuel (HVOF) sprayed MCrAlYHfSi bond coatings with air-plasma sprayed YSZ top coatings on superalloys X4, 1483 or 247 substrates. For both types of coatings exposed in 1h cycles, the addition of water vapor resulted in a decrease in coating lifetime, except for Pt diffusion coatings which were unaffected by the environment. In 100h cycles, environment was less critical, perhaps because coating failure was chemical (i.e. due to interdiffusion) rather than mechanical. In both 1h and 100h cycles, CO2 did not appear to have any negative effect on coating lifetime.

scholarly journals Effect of Air Plasma Sprayed Flash Bond Coatings on Furnace Cycle Lifetime of Disks and Rods

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Bruce A. Pint ◽  
Michael J. Lance ◽  
J. Allen Haynes ◽  
Edward J. Gildersleeve ◽  
Sanjay Sampath
Keyword(s):  
Crack Formation ◽  
Thermal Barrier ◽  
Vacuum Plasma Spray ◽  
Air Plasma ◽  
Bond Coatings ◽  
Bond Coating ◽  
Vacuum Plasma ◽  
Coating Roughness ◽  
Plasma Sprayed ◽  
Oxygen Fuel

Abstract Air plasma sprayed (APS) flash coatings on high velocity oxygen fuel (HVOF) bond coatings are well known to extend the lifetime of thermal barrier coatings (TBCs). Recent work compared flash coatings of NiCoCrAlY and NiCoCrAlYHfSi applied to both rods and disk substrates of alloy 247. For rod specimens, 100 h cycles were used at 1100 °C in wet air. Both flash coatings significantly improved the lifetime compared to HVOF-only and vacuum plasma spray (VPS)-only MCrAlY bond coatings with no statistical difference between the two flash coatings. For disk specimens tested in 1 h cycles at 1100 °C in wet air, the NiCoCrAlY flash coating significantly outperformed an HVOF-only NiCoCrAlYHfSi bond coating and a NiCoCrAlYHfSi flash coating. The flash coatings formed a mixed oxide-metal zone that appeared to inhibit crack formation and therefore extend lifetime. In addition to the flash coating increasing the bond coating roughness, the underlying HVOF layer acted as a source of Al for this intermixed zone and prevented the oxide from penetrating deeper into the bond coating. The lower Y+Hf content in the Y-only flash coating appeared to minimize oxidation in the flash layer, thereby increasing the benefit compared to a NiCoCrAlYHfSi flash coating.

scholarly journals The Effect of Environment on Thermal Barrier Coating Lifetime

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Bruce A. Pint ◽  
Kinga A. Unocic ◽  
J. Allen Haynes
Keyword(s):  
Water Vapor ◽  
Thermal Barrier Coating ◽  
Carbon Capture ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Combustion Gas ◽  
Bond Coatings ◽  
Barrier Coating ◽  
Negative Effect ◽  
Plasma Sprayed

While the water vapor content of the combustion gas in natural gas-fired land-based turbines is ∼10%, it can be 20–85% with coal-derived (syngas or H2) fuels or innovative turbine concepts for more efficient carbon capture. Additional concepts envisage working fluids with high CO2 contents to facilitate carbon capture and sequestration. To investigate the effects of changes in the gas composition on thermal barrier coating (TBC) lifetime, furnace cycling tests (1-h and 100-h cycles) were performed in air with 10, 50, and 90 vol. % water vapor and CO2-10% H2O and compared to prior results in dry air or O2. Two types of TBCs were investigated: (1) diffusion bond coatings (Pt-diffusion or Pt-modified aluminide) with commercial electron-beam physical vapor-deposited yttria-stabilized zirconia (YSZ) top coatings on second-generation superalloy N5 and N515 substrates and (2) high-velocity oxygen fuel (HVOF) sprayed MCrAlYHfSi bond coatings with air plasma-sprayed YSZ top coatings on superalloys X4, 1483, or 247 substrates. For both types of coatings exposed in 1-h cycles, the addition of water vapor resulted in a decrease in coating lifetime, except for Pt-diffusion coatings which were unaffected by the environment. In 100-h cycles, environment was less critical, perhaps because coating failure was chemical (i.e., due to interdiffusion) rather than mechanical. In both 1-h and 100-h cycles, CO2 did not appear to have any negative effect on coating lifetime.

Study of Damage Processes in Plasma Sprayed Bond Coat Under Thermal Cycling

1998 ◽  
Author(s):  
P. Bonnet ◽  
S. Abboudl ◽  
B. Normand
Keyword(s):  
High Temperature ◽  
Thermal Cycling ◽  
Bond Coat ◽  
Gas Turbines ◽  
Temperature Oxidation ◽  
Bond Coating ◽  
Engine Efficiency ◽  
Thermal Barriers ◽  
Plasma Sprayed ◽  
Damage Processes

Abstract Plasma sprayed thermal barriers are used as insulating materials in the hot sections of gas turbines to decrease the metal temperatures during service and men allow a higher combustion temperature for better engine efficiency. They usually contain a bond coating to protect the substrate from high temperature oxidation and a top coat with a low thermal conductivity. This study evaluate and identify the mechanisms of degradation of a vacuum plasma sprayed NiCoCrAlYTa bond coat subjected to thermal cycling at high temperature. The microstructure and micro-composition of the coating layer were analyzed by scanning electron microscopy and energy dispersive X-ray analysis to elucidate the improvement and degradation mechanisms of the material. The thermal cycling provokes some morphological and chemical modifications changes within this material. These modifications provoke a perturbation of the heat transfer within the material.

Microstructure and Oxidation Behavior of Molybdenum Disilicide Coating Prepared by Air Plasma Sprayed

2011 ◽  
Vol 686 ◽  
pp. 583-588 ◽  
Author(s):  
Jian Hui Yan ◽  
Si Wen Tang ◽  
Jian Guang Xu
Keyword(s):  
Plasma Spraying ◽  
Gas Turbines ◽  
Hexagonal Lattice ◽  
Molybdenum Disilicide ◽  
Temperature Structure ◽  
Air Plasma ◽  
Air Plasma Spraying ◽  
Plasma Sprayed ◽  
Molybdenum Disilicide Coating ◽  
Oxidation Behaviors

Intermetallics molybdenum dislicied has a great potential as a protective coating in aircraft engines and gas turbines in the elevated temperature. The suit for plasma spraying MoSi2powders were prepared by spray drying process and vacuum sintered. The oxidation behaviors of the coating were determined at 1200 °C. The coatings as sprayed and oxidized were characterized by XRD, SEM and EDS. Results show that the flow ability and loose density of MoSi2powder by sintered treatment, were 17.1 s/50g and 2.1g/cm3, respectively, ideal for air plasma spraying. During the course of spraying, some of molybdenum disilicide with a tetragonal lattice was converted into molybdenum disilicide with a hexagonal lattice. Also, part of MoSi2 phase oxidized and transformed to Mo5Si3phase. A relative dense molybdenum disilicide coating was prepared by air plasma spraying. A protective SiO2layer, seems to be glassy, with a thickness about 10 μm was formed on the surface of MoSi2coating during MoSi2coating oxidized at 1200°C for 200 h. The results of the oxidation tests show that MoSi2coating prepared by air plasma spraying may be provide a protect layer for high temperature structure material.

Cyclic Oxidation Behavior of Thermal Barrier Coatings in Environments Containing Water Vapor

2007 ◽  
Vol 336-338 ◽  
pp. 1750-1752 ◽  
Author(s):  
Chang Liang Wang ◽  
Chun Gen Zhou ◽  
Sheng Kai Gong ◽  
Hui Bin Xu
Keyword(s):  
Cyclic Oxidation ◽  
Nickel Base Superalloy ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Test Environment ◽  
Bond Coatings ◽  
Barrier Coating ◽  
Initial Stage ◽  
Nickel Base ◽  
Plasma Sprayed

The cyclic oxidation of thermal barrier coating (TBC) specimens consisting of nickel-base superalloy, low pressure plasma sprayed Ni-24Cr-6Al-0.7Y (wt.%) bond coatings and air plasma sprayed 7.5 wt.% yttria stabilized zirconia top coatings was studied at 1050°C in air, (air + 5%H2O), O2 and (O2 + 5%H2O) respectively. The oxidation kinetics of the TBC in each test environment accords with parabolic law at the initial stage and obeys almost liner law at the final stage. The cyclic oxidation life of the TBC is 500h (1h/cyc) in O2 and (O2 + 5%H2O) and 900 h in air and (air + 5%H2O). The SEM observations indicated the oxide formed along the bond coat and top coat interface after failure at 1050°C in different environments are all consisted of Al2O3, Ni(Al,Cr)2O4, NiO and Cr2O3.

Influence of Powder Manufacturing Process on TBC Lifetime

1995 ◽  
Author(s):  
Marc J. Froning ◽  
Purush Sahoo
Keyword(s):  
Manufacturing Process ◽  
Gas Turbines ◽  
Thermal Cycle ◽  
Thermodynamic Efficiency ◽  
Air Plasma ◽  
Before And After ◽  
Coating Characteristics ◽  
Lifetime Studies ◽  
Plasma Sprayed ◽  
Powder Manufacturing

Thermal barrier coatings (TBC) have been used extensively in aircraft engines to protect the gas turbines’ hot section from mechanical and enviromental degradation as well as to improve thermodynamic efficiency. Because TBC’s enhance operating temperature and service life, they are expected to play and increasingly important role in protecting both flight and land based industrial turbine engines. This investigation examines the functionality of air plasma sprayed two-layer TBC systems with a MCrAlY bond coat and a yttria partially stabilized zirconia (YSZ) top coat. Qualitative X-ray diffraction (XRD) analyses were conducted on several commercially produced YSZ powders and the coatings produced from the powders. Thermal cycle lifetime studies were carried out at 2040°F. Phase structures of the coatings were evaluated before and after testing. An attempt was then made to correlate those results to thermal cycle life. It was found that the powder manufacturing process appears to have an influence on coating characteristics and on thermal shock lifetime.

Characterization of Plasma Sprayed Yittria Stabilized Zirconia (8 wt %) Hydroxyapatite Coatings

2011 ◽  
Vol 493-494 ◽  
pp. 535-538
Author(s):  
O. Anzabi ◽  
M.M. Aydin ◽  
L.S. Ozyegin ◽  
F.N. Oktar ◽  
Kārlis A. Gross ◽  
...  
Keyword(s):  
Titanium Oxide ◽  
Pure Titanium ◽  
X Ray Diffraction ◽  
Stabilized Zirconia ◽  
X Ray ◽  
Bond Coatings ◽  
Bond Coating ◽  
Bond Layer ◽  
Diffraction Patterns ◽  
Plasma Sprayed

Splitting problems at HA-coated implants are generally due to biological reasons. Bond-coatings were used to prevent the splitting problem of zirconia ceramics; this method can be widely seen in industrial applications. Two main groups were used; the first group consisted of spraying a bond layer of titania onto commercially pure titanium. This followed by a spray of HA with 5, 10 and 15 % zirconia (8 % yttria doped) as main layer onto the first bond-coating. For the second group, the samples were coated without bond-coating. Firstly, X-ray diffraction patterns of the starting powders were taken. Then x-ray diffraction patterns of the plasma sprayed samples were taken. In literature, it was seen that 20 % zirconia was sufficient for the transformation into a monoclinic structure for the bond-coated samples. For this study it was found that 10 % zirconia was sufficient to transform to the same structure of the desired crystalline phase transformation. The coating kept its crystal structure and relatively small amount of amorphous transformation was detected. A similar structure was produced using less zirconia. It was thought that the use of titanium-oxide bond-coating layer would play an important role as a third variable in the results. To further investigate these phenomena, more detailed researches must be conducted with using titanium-oxide yittria stabilized zirconia (8 wt %) hydroxyapatite bond-coatings with HA main coatings.

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