Effect of Atmosphere Composition on Lifetime and Oxidation Behavior of EB-PVD TBC with NiPtAl Bondcoats

2013 ◽  
Vol 652-654 ◽  
pp. 1822-1825
Author(s):  
Peng Song ◽  
Jian Sheng Lu
Keyword(s):  
Oxide Layer ◽  
Base Alloy ◽  
Layer Growth ◽  
Low Oxygen ◽  
Aluminide Coatings ◽  
Barrier Coating ◽  
Temperature Exposure ◽  
Short Time ◽  
Surface Morphologies ◽  
Tbc Systems

NiPtAl coatings are widely used as bondcoats for thermal barrier coating (TBC) systems during high temperature exposure. Pt modified aluminide coatings on the CMSX-4 Ni-base alloy were oxidized at 1150°C in different atmospheres. Cross-section oxide layer morphologies on the NiPtAl coatings after TBC failure were similar in air with that in air+15%H2O. The surface morphologies of as-received low and high-Pt bondcoats showed great effect on the oxide layer growth and morphologies due to the different compositions within the two bondcoats. The irregular alumina surface on the low-Pt bondcoat was showed due to the slipping of the NiPtAl grains. Raman spectroscopy illustrated that the alumina mainly consisted θ and α-Al2O3during the Ar+20%O2exposure, however, only α-Al2O3could be found in Ar+4%H2+2%H2O during short time exposure. Low oxygen partial pressure of Ar+4%H2+2%H2O perhaps is the reason that spinel and θ-Al2O3can not formed, and directly promotes the α-Al2O3formation.

Microstructural Features Resulting From Isothermal and Thermocyclic Exposure of a Thermal Barrier Coating

2000 ◽  
Vol 122 (3) ◽  
pp. 333-337 ◽  
Author(s):  
Mark E. Walter ◽  
Bolarinwa Onipede ◽  
Wole Soboyejo ◽  
Chris Mercer
Keyword(s):  
Gas Turbine ◽  
Oxide Layer ◽  
Thermal Barrier Coating ◽  
Growth Model ◽  
Thermal Barrier ◽  
Oxide Growth ◽  
Isothermal Exposure ◽  
Barrier Coating ◽  
Initiation And Propagation ◽  
Tbc Systems

Thermal barrier coating (TBC) systems are receiving a great deal of attention as a result of their ability to enable higher operating temperatures without sacrificing component durability in gas turbine systems. Nonetheless, there are a number of unknowns associated with the failure of TBC systems. In particular, the initiation and propagation of damage has not been observed. In this paper, the microstructural changes in and along the thermally growth oxide layer of a TBC are presented. Specimens were studied primarily after isothermal exposure for 48, 96, 200, and 300 hours at 1100°C and also after thermocyclic exposure. Failure features are discussed and the growth of oxide is quantified. The oxide growth is placed within the context of a parabolic growth model. [S0094-4289(00)01503-6]

Effect of Polishing Treatment on Rumpling of Oxide Scales on NiPtAl Coatings with Different Pt-Content

2013 ◽  
Vol 662 ◽  
pp. 383-386
Author(s):  
Peng Song ◽  
Jian Sheng Lu
Keyword(s):  
High Temperature ◽  
Nickel Aluminide ◽  
Aluminide Coating ◽  
Temperature Cycling ◽  
Oxide Surface ◽  
Temperature Oxidation ◽  
Aluminide Coatings ◽  
Temperature Exposure ◽  
Engine Components ◽  
Surface Morphologies

Pt-modified nickel aluminide coatings have been more widely used for protection of jet-engine components against high-temperature oxidation. The coating rumpling of two Pt-content NiPtAl coatings was studied in this paper during high temperature exposure. The results indicated that the NiPtAl coating grains size made a great contribution to the oxide surface morphologies, especially rumpling. Smaller grain size within high-Pt coating indicated a denser rumpling compared to low-Pt coating due to PtAl2 formation in the earlier coating. The failed local alumina at the ridges was also found on the low-Pt coating after cyclic oxidatioin. It was found that polished treatment resulted a comparatively flat and homogeneous oxide layer compared to as-received coatings. The temperature cycling could promote the aluminide coating rumpling, however, the polished treatment could not completely eliminate the roughening.

MODELING THE NORMAL SPECTRAL EMISSIVITY OF BRASS H62 AT 800–1100 K DURING OXIDE LAYER GROWTH

2018 ◽  
Vol 49 (15) ◽  
pp. 1445-1458
Author(s):  
Deheng Shi ◽  
Fenghui Zou ◽  
Zunlue Zhu ◽  
Jinfeng Sun
Keyword(s):  
Oxide Layer ◽  
Spectral Emissivity ◽  
Layer Growth ◽  
Normal Spectral Emissivity

scholarly journals The Atmosphere’s Effect on Stainless Steel Slabs’ Oxide Formation in a CH4-Fuelled Reheating Furnace

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 621
Author(s):  
Aleksi Laukka ◽  
Eetu-Pekka Heikkinen ◽  
Timo Fabritius
Keyword(s):  
Stainless Steel ◽  
Oxide Layer ◽  
Depth Profiling ◽  
Layer Growth ◽  
304 Stainless Steel ◽  
Oxide Growth ◽  
Breakaway Oxidation ◽  
Positive Effects ◽  
Steel Slab ◽  
Single Temperature

Utilising the oxyfuel practice for CH4-fuelled combustion has positive effects on the emissions, efficiency and cost of high temperature furnace practices. However, especially in older installations, oxyfuel usage requires retrofitting and alters the atmosphere in which the oxidation of the steel occurs, when compared to using air as the oxidiser. Stainless steel slab oxide growth during reheating was studied in different atmospheres. The simulated post-burn atmospheres from oxyfuel, lean oxyfuel and air-fuel practices were used to compare oxide-scale layer growth and morphology during simulated typical AISI 304 stainless steel slab reheating prior to hot rolling. Thermogravimetric measurements, glow discharge optical emission spectrometer (GDOES) and field-emission scanning electron microscope energy dispersive X-ray (FESEM-EDS) methodology were applied to discern differences between oxide growth and inner oxide layer morphology between the three practices. Switching from air to oxyfuel practice at a single temperature had the same increasing effect on the scale formation amount as a 25 °C temperature increase in air atmosphere. Inner oxide layer depth profiling revealed C, Si and Ni to be the main elements that differed between temperatures and atmospheres. A morphology study showed Si and Ni behaviour to be linked to breakaway oxidation.

Combined Effects of Overheating and Soot-Blower Erosion on Reheater Tubing in a Gas-Fired Large Capacity Boiler

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Nasr M. Hosny
Keyword(s):  
Data Analysis ◽  
Oxide Layer ◽  
Test Data ◽  
Gas Flow ◽  
Combined Effects ◽  
Unit Operation ◽  
Metal Oxidation ◽  
Flow Temperature ◽  
Large Capacity ◽  
Short Time

In a large capacity tangentially fired boiler, the final reheater tubing sustained abnormal oxidation and localized excessive metal wastage in a short time of the unit operation. The root causes of the problem are identified by test data analysis. The test data indicated that the reheater tubing metal temperatures in the affected areas exceeded the recommended limit of the metal oxidation temperature due to higher than expected local gas temperatures and velocities. A soot-blower facing the overheated portion of the reheater leading tubes accelerated the process of metal wastage by periodically removing the oxide layer. The configuration of the boiler internals upstream of the reheater section is found to be the main cause of the localized overheating. Side-to-side gas flow/temperature stratification due to tangential firing contributed to a lesser degree to the problem. The results and conclusions presented in this paper should be a beneficial guide to the designer of large capacity boilers.

Oxidation Behavior of Cu60Zr30Ti10 Bulk Metallic Glass

2005 ◽  
Vol 20 (6) ◽  
pp. 1396-1403 ◽  
Author(s):  
C.Y. Tam ◽  
C.H. Shek
Keyword(s):  
Metallic Glass ◽  
Oxide Layer ◽  
Bulk Metallic Glass ◽  
Photoelectron Spectroscopy ◽  
Oxidation Kinetics ◽  
Oxide Surface ◽  
X Ray ◽  
Rate Law ◽  
Cu Content ◽  
Surface Morphologies

The oxidation kinetics of Cu60Zr30Ti10 bulk metallic glass and its crystalline counterpart were studied in oxygen environment over the temperature range of 573–773 K. The oxidation kinetics, measured with thermogravimetric analysis, of the metallic glass follows a linear rate law between 573 and 653 K and a parabolic rate law between 673 and 733 K. It was also found that the oxidation activation energy of metallic glass is lower than that of its crystalline counterpart. The x-ray diffraction pattern showed that the oxide layer is composed of Cu2O, CuO, ZrO2, and metallic Cu. Cu enrichment on the topmost oxide layer of the metallic glass oxidized at 573 K was revealed by x-ray photoelectron spectroscopy while there was a decrease in Cu content in the innermost oxide layer. The oxide surface morphologies observed from scanning electron microscopy showed that ZrO2 granules formed at low temperatures while whiskerlike copper oxides formed at higher temperatures.

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.

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