Mechanisms of Acute Angle Laser Drilling Induced Thermal Barrier Coating Delamination

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
H. K. Sezer ◽  
L. Li
Keyword(s):  
Leading Edge ◽  
Laser Drilling ◽  
Acute Angle ◽  
Thermal Barrier ◽  
Bond Coating ◽  
Barrier Coating ◽  
Coating Delamination ◽  
Plasma Sprayed ◽  
Delamination Cracks ◽  
Melt Ejection

Laser fabrication of cooling holes in certain parts of the aero-engine components involves percussion or trepan drilling at acute angles (e.g., 16–30 deg) to the surface. These parts are often covered with plasma sprayed ceramic thermal barrier coatings (TBCs) to protect them from reaching excessive temperatures in hot engine environments. Delamination of the TBC is the main problem of laser drilling acute angled holes in the coated components. The present study investigates the mechanisms involved in the development of the delamination cracks. A significant role of melt ejection in the formation of cracks and the delamination at the coating/coating interface of the leading edge of a laser-drilled inclined hole was identified. It is shown that the delamination mechanisms at the TBC coating/bond coating and the bond coating/substrate interfaces are different. Melt ejection induced stresses were identified as the key mechanisms for the former type, while the thermal effects dominates the latter type.

HOT CORROSION OF CERIA-YTTRIA STABILIZED ZIRCONIA PLASMA SPRAYED THERMAL BARRIER COATING BY EUTECTIC VANDIUM PENTAOXIDE-SODIUM SULFATE

2018 ◽  
Vol 18 (1) ◽  
pp. 182-192 ◽  
Author(s):  
Mohammed J Kadhim ◽  
Mohammed H Hafiz ◽  
Maryam A Ali Bash
Keyword(s):  
Thermal Barrier Coating ◽  
Hot Corrosion ◽  
Monoclinic Phase ◽  
Volume Fraction ◽  
High Volume ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Plan View ◽  
Barrier Coating ◽  
Plasma Sprayed

The high temperature corrosion behavior of thermal barrier coating (TBC) systemconsisting of IN-738 LC superalloy substrate, air plasma sprayed Ni24.5Cr6Al0.4Y (wt%)bond coat and air plasma sprayed ZrO2-20 wt% ceria-3.6 wt% yttria (CYSZ) ceramic coatwere characterized. The upper surfaces of CYSZ covered with 30 mg/cm2 , mixed 45 wt%Na2SO4-55 wt% V2O5 salt were exposed at different temperatures from 800 to 1000 oC andinteraction times from 1 up to 8 h. The upper surface plan view of the coatings wereidentified for topography, roughness, chemical composition, phases and reaction productsusing scanning electron microscopy, energy dispersive spectroscopy, talysurf, and X-raydiffraction. XRD analyses of the plasma sprayed coatings after hot corrosion confirmed thephase transformation of nontransformable tetragonal (t') into monoclinic phase, presence ofYVO4 and CeVO4 products. Analysis of the hot corrosion CYSZ coating confirmed theformation of high volume fraction of YVO4, with low volume fractions of CeOV4 and CeO2.The formation of these compounds were combined with formation of monoclinic phase (m)from transformation of nontransformable tetragonal phase (t').

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.

scholarly journals Evaluation of High Pressure Turbine Blade Coatings on an LM2500 Rainbow Rotor

1995 ◽  
Author(s):  
B. Nagaraj ◽  
G. Katz ◽  
A. F. Maricocchi ◽  
M. Rosenzweig
Keyword(s):  
High Pressure ◽  
Turbine Blades ◽  
Leading Edge ◽  
Service Evaluation ◽  
High Pressure Turbine ◽  
Barrier Coating ◽  
Marine Propulsion ◽  
Corrosion Resistant Coatings ◽  
Stage 1 ◽  
Plasma Sprayed

Two LM2500 rainbow rotors with repaired stage 1 and stage 2 high pressure turbine blades are being assembled for marine propulsion service evaluation by the US Navy. The blades have seen between 5,000 and 15,000 hours of service in the Navy’s Fleets. A number of corrosion resistant coatings including plasma sprayed CoCrAlHf (bill of material), composite plated CoCrAlHf, platinum aluminide, aluminum silicide, and physical vapor deposited yttria stabilized zirconia thermal barrier coating (PVD TBC) will be evaluated in the rainbow rotor. This paper will discuss the advantages and microstructures of the various coatings. Composite plated CoCrAlHf, and PVD TBCs were recently service evaluated in an industrial LM2500 rainbow rotor for 10,500 hours. Both these coatings performed well, although the PVD TBC had local spallation at the leading edge. This paper will review the details of performance of these two coatings in the industrial LM2500 application.

Mechanical Properties of Thermal Barrier Coatings at Room Temperature

2005 ◽  
Vol 290 ◽  
pp. 336-339 ◽  
Author(s):  
G. Guidoni ◽  
Y. Torres Hernández ◽  
Marc Anglada
Keyword(s):  
Mechanical Properties ◽  
Thermal Barrier Coatings ◽  
Room Temperature ◽  
Inconel 625 ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Bending Tests ◽  
Four Point Bending ◽  
Barrier Coating ◽  
Plasma Sprayed

Four point bending tests have been carried out on a thermal barrier coating (TBC) system, at room temperature. The TBC system consisted of a plasma sprayed Y-TZP top coat with 8 % in weight of Yttria, a bond coat of NiCrAlY and a Ni-based superalloy Inconel 625 as substrate. The TBC coating was deposited on both sides of the prismatic specimens. Efforts have been done in detecting the damage of the coating by means of Maltzbender et al [1] model.

Oxygen Transport Through the Zirconia Top Coat in Thermal Barrier Coating Systems

1998 ◽  
Author(s):  
A.C. Fox ◽  
T.W. Clyne
Keyword(s):  
Thermal Barrier Coating ◽  
Bond Coat ◽  
Ionic Conduction ◽  
Gas Permeability ◽  
Gas Permeation ◽  
Thermal Barrier ◽  
Barrier Coating ◽  
Oxygen Gas ◽  
Plasma Sprayed ◽  
Tbc Systems

Abstract The gas permeability of plasma sprayed yttria-stabilised zirconia coatings has been measured over a range of temperature, using hydrogen and oxygen gas. The permeability was found to be greater for coatings produced with longer stand-off distances, higher chamber pressures and lower torch powers. Porosity levels have been measured using densitometry and microstructural features have been examined using SEM. A model has been developed for prediction of the permeability from such microstructural features, based on percolation theory. Agreement between predicted and measured permeabilities is good. Ionic conduction through the coatings has also been briefly explored. It is concluded that transport of oxygen through the top coat in thermal barrier coating (TBC) systems, causing oxidation of the bond coat, occurs primarily by gas permeation rather than ionic conduction, at least up to temperatures of about 1000°C and probably up to higher temperatures. Top coat permeabilities appreciably below those measured will be required if the rate of bond coat oxidation is to be reduced by cutting the supply of oxygen to the interface.

Sign in / Sign up

Export Citation Format

Share Document