Measurement of the stress in oxide scales formed by oxidation of alumina-forming alloys

The micro damage evolution behavior in air plasma-sprayed 8 mass% Y 2 O 3 stabilized ZrO 2 thermal barrier coating (APS-TBC) after isothermal heat exposure at 1150 C up to 200 h was observed. Residual stress of thermally-grown-oxide (TGO) layer was measured through the TBC layer using Cr 3þ luminescence spectroscopy and the measured stress levels were compared with micro damage evolution behavior stored in the TBC system. With heat exposure time of longer than 10 h, microfracture behaviors were noted in the TBC layer. In-plane residual stress of the TGO layer increased for up to 50 h of heat exposure time, and thereafter, diminished with further increase. These behaviors are strongly correlated with the thickness and the residual stress of the TGO layer. This decrease in the TGO stress well contrasts with the evolution of the micro fracture behavior, which is also related to the thickness and undulation of the formed TGO layer. The change of TGO stress, tgo , depending on the average thickness of the TGO layer, " h h tgo , i.e., d tgo =d " h h tgo is a useful indicator of the damage evolution in TGO:h h tgo > 0: slight damage stage, d tgo =d " h h tgo < 0: micro fracture evolution stage. The result suggests that Cr 3þ luminescence spectroscopy is a good indicator for micro damage evolution in the TBC layer and is a useful tool for nondestructive evaluation (NDE) of APS-TBC systems.

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“…14,20) The formed TGO layer is assumed to be a polycrystalline Al 2 O 3 and isotropic with quite a low Cr content (<0:5 mass%).…”

Section: Stress Measurement In Tgo Layermentioning

confidence: 99%

Detection of Micro-Damage Evolution of Air Plasma-Sprayed Y2O3-ZrO2 Thermal Barrier Coating through TGO Stress Measurement

2006

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“…The specimen was oxidized in air at 11218C for successively longer periods of time (1,2,4,8,16, 32 h). After each oxidation the sample was cooled to room temperature and the photostimulated Cr 3+ uorescence (luminescence) spectrum recorded.…”

Section: Residual Stress Evolution On Oxidationmentioning

confidence: 99%

Spalling failure of a thermal barrier coating associated with aluminum depletion in the bond-coat

1999

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“…All studies on NiAl showed initial tensile stresses related to the phase transformation from transition alumina to alpha. After this transformation is complete, the stress is near zero [10,15] or slightly compressive (-80 MPa) [11], except a recent in-situ XRD study done at 950 o C, which found 500 MPa tensile stress [8]. The effect of a reactive element, Hf, was to reduce the small compressive growth stress to zero [11], or raise the tensile stress from 500 to 600 MPa [8].…”

mentioning

confidence: 99%

“…All deflection results showed initially high compressive growth stresses (from -250 to -900 MPa) [5][6][7], and levels deduced from room temperature residual stress measurements ranged from (-0.3 to -1.8 GPa) [9,15,16]. A study of room temperature stress levels coupled with specimen length change found high tensile (1.2 GPa) or low compressive (-0.1 GPa) growth stresses during the initial stage of oxidation (0.1 hr) at 1000 o C, but the stresses were all compressive (up to -1.2 GPa) after longer times at 1000 o C and at all times at higher temperatures.…”

mentioning

confidence: 99%

Growth Strains and Stress Relaxation in Alumina Scales during High Temperature Oxidation

Hou

Paulikas

Veal

2004

MSF

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Abstract.A novel X-ray technique was used, exploiting synchrotron radiation at the Advanced Photon Source at Argonne National Laboratory, to investigate the growth stresses in α-Al 2 O 3 . In-situ measurements of Debye-Scherrer diffraction patterns from the scale were recorded during oxidation and cooling, and the elliptical distortion of the diffraction rings was analyzed to yield the in-plane strain. Fe28Al, and Ni-50Al (at. %) were studied. Data were acquired in air at temperatures between 950-1100 o C and during cool down. In all cases, the steady stage growth strain was relatively low (<0.1%) and was either tensile or compressive depending on the alloy. A higher tensile strain often existed during the initial oxidation period when transition alumina was present. Thermal stresses imposed on NiAl by reducing the sample temperature to 950 o C for a period of time showed noticeable stress relaxation by creep. Different degrees of relaxation were also found during cooling depending on alloy composition and scale microstructure. On all Fe-based alloys, the first formed α-Al 2 O 3 was highly textured with the degree of texture decreasing with further oxidation. The relationships between stress development, scale wrinkling, oxide phase changes, and the effect of reactive element addition on growth stresses are discussed. Results are compared with other reports of growth stresses in Al 2 O 3 scales.

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Measurement of the stress in oxide scales formed by oxidation of alumina-forming alloys

Cited by 286 publications

References 11 publications

Detection of Micro-Damage Evolution of Air Plasma-Sprayed Y<SUB>2</SUB>O<SUB>3</SUB>-ZrO<SUB>2</SUB> Thermal Barrier Coating through TGO Stress Measurement

Detection of Micro-Damage Evolution of Air Plasma-Sprayed Y<SUB>2</SUB>O<SUB>3</SUB>-ZrO<SUB>2</SUB> Thermal Barrier Coating through TGO Stress Measurement

Spalling failure of a thermal barrier coating associated with aluminum depletion in the bond-coat

Growth Strains and Stress Relaxation in Alumina Scales during High Temperature Oxidation

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