Damage evolution in an electron beam physical vapor deposited thermal barrier coating as a function of cycle temperature and time

Sridharan, Swetha; Xie, Liangde; Jordan, Eric H.; Gell, Maurice; Murphy, K. S.

doi:10.1016/j.msea.2004.09.037

Cited by 48 publications

(17 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The final thickness of the TGO at this stage was some 7 lm on an IN100 substrate with a NiCoCrAlY bondcoat, and slightly less on equivalent CMSX-4 substrates. A similar critical TGO thickness has been frequently reported [48]. Hence it is assumed that spallation failure in these cases is initiated by stresses on outgrowing a "critical" thickness of the respective TGO in the course of bondcoat oxidation, supporting a mechanistic view of adhesion.…”

Section: Tbc Lifetime and "Matching" Activation Energies Of Related Msupporting

confidence: 79%

Lifetime‐determining spalling mechanisms of NiCoCrAlRE / EB‐PVD zirconia TBC systems

Fritscher

Schulz

Leyens

2007

Materialwissenschaft Werkst

View full text Add to dashboard Cite

The mechanisms that control the lifetime of thermal barrier coating (TBC) systems have been traced by two particular overlay bondcoats serving as model systems: superalloy pins (IN100, CMSX-4) with two alternative NiCoCrAlRE (RE: Hf, Y) bond coat compositions (i) NiCoCrAlY without and (ii) with co-dopants of silicon and hafnium. On top an electron-beam physical-vapor deposited (EB-PVD) yttria partially stabilized zirconia (YPSZ) TBC commonly mixed with 2 wt.% hafnia, or, rarely with 10 wt.%, was applied. The test pins were thermo-cycled at 1100 and 1150 C until failure. Identical lifetimes in cyclic tests on YPSZ TBCs with 2 (relatively high sintering rate) and 10 wt.% hafnia (relatively low sintering rate) preclude an effect of diffusion mechanisms of the YPSZ TBC on lifetime. The fit of lifetimes and test temperatures to Arrhenius-type relationships gives activation energies for failure. These energies agree with the activation energies for anion and cation diffusion in alumina for the respective bondcoat variant:(i) for the NiCoCrAlY/TBC system for O 2-diffusion in alumina, (ii) for the NiCoCrAlYSiHf/TBC system for Al 3+ diffusion in alumina.SEM and EDS investigations of the thermally grown oxides (TGOs) confirm the mechanisms responsible for TBC failure as indicated by activation energies. Two categories of failure can be distinguished: (i) NiCoCrAlY coatings fail by an "adhesive mode of failure" along smooth bond coat/TGO interfaces driven by a critical TGO thickness. (ii) NiCoCrAlYSiHf coatings fail later and more reluctantly by a "cohesive" crack mode via de-cohesion at the TGO/TBC interface. In the latter case a quasi-integrity of the crack-affected TGO is lengthily maintained up to failure by a crack-pinning mechanism which runs via Al 3+ supply from the bondcoat.Keywords

show abstract

Section: Tbc Lifetime and "Matching" Activation Energies Of Related Msupporting

confidence: 79%

Lifetime‐determining spalling mechanisms of NiCoCrAlRE / EB‐PVD zirconia TBC systems

Fritscher

Schulz

Leyens

2007

Materialwissenschaft Werkst

View full text Add to dashboard Cite

show abstract

“…[5][6][7][8][9] A TBC failure mechanism that is common to EBPVD TBCs on heavy grit-blasted platinum-modified aluminides involves rumpling or ratcheting of the coating and the TGO. As discussed by Spitzberg et al [7] during thermal cycling, the TGO undergoes displacement instability with periodic penetrations of the TGO into the bond coat.…”

Section: Introductionmentioning

confidence: 99%

Comparison of the Failures during Cyclic Oxidation of Yttria-Stabilized (7 to 8 Weight Percent) Zirconia Thermal Barrier Coatings Fabricated via Electron Beam Physical Vapor Deposition and Air Plasma Spray

Yanar

Helminiak

Meier

et al. 2010

Metall Mater Trans A

View full text Add to dashboard Cite

The failures during oxidation of electron beam physical vapor deposition (EBPVD) and air plasma spray (APS) yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) on different bond coats, namely, platinum-modified aluminide and NiCoCrAlY, are described. It is shown that oxidation of the bond coats, along with defects existing near the TBC/bond coat interface, plays a very important role in TBC failures. Procedures to improve TBC performance via modifying the oxidation characteristics of the bond coats and removing the as-processed defects are discussed. The influence of exposure conditions on TBC lives is described and factors such as cycle frequency and thermal gradients are discussed.

show abstract

“…For the oxide scales developing on the Pt-modified Ni-aluminide bond coatings, parabolic growth kinetics usually apply [8,11]. However, for the oxide scales developing on a MCrAlY bond coating, the growth kinetics cannot be described with a single parabolic rate constant, in particular when long oxidation periods are considered [12].…”

Section: Introductionmentioning

confidence: 99%

Effect of Y Distribution on the Oxidation Kinetics of NiCoCrAlY Bond Coat Alloys

Nijdam

Sloof

2007

Oxid Met

View full text Add to dashboard Cite

The relation between the Y distribution in the alloy and the growth kinetics of the developing oxide scale was studied for the thermal oxidation of two .2Y (at.%) alloys at 1,373 K: (i) a coarse-grain cast alloy with large Ni 5 Y intermetallic precipitates, and (ii) a fine-grain freestanding coating with small Ni 5 Y precipitates. Using a combination of experiments and model calculations, it is shown that the average growth kinetics of a NiCoCrAlY alloy are dependent on the size and distribution of Y-rich oxide inclusions (pegs) in the a-Al 2 O 3 oxide layer. Alumina scales containing a high density of small Y-oxide inclusions grow faster than a-Al 2 O 3 scales containing only a few, large Y-oxide inclusions. Upon oxidation of the freestanding coating, the Y-oxide inclusions in the scale attain their maximum size after the Y in the coating is completely consumed. After this point, a decrease in the average oxidation kinetics occurs.

show abstract

Damage evolution in an electron beam physical vapor deposited thermal barrier coating as a function of cycle temperature and time

Cited by 48 publications

References 35 publications

Lifetime‐determining spalling mechanisms of NiCoCrAlRE / EB‐PVD zirconia TBC systems

Lifetime‐determining spalling mechanisms of NiCoCrAlRE / EB‐PVD zirconia TBC systems

Comparison of the Failures during Cyclic Oxidation of Yttria-Stabilized (7 to 8 Weight Percent) Zirconia Thermal Barrier Coatings Fabricated via Electron Beam Physical Vapor Deposition and Air Plasma Spray

Effect of Y Distribution on the Oxidation Kinetics of NiCoCrAlY Bond Coat Alloys

Contact Info

Product

Resources

About