Improvement of cyclic oxidation resistance of Y-containing TiAl-based alloys with equiaxial gamma microstructures

Wu, Ying; Hagihara, Koji; Umakoshi, Yukichi

doi:10.1016/j.intermet.2005.01.014

Cited by 32 publications

(11 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…5, the surface morphology of the 0.3 and 0.6 at.%Y alloys was finer and denser while the surface oxides on the Y-free alloy exhibited coarse grains with severe spallation, which is quite similar to Ti-50Al-xY alloys under cyclic-oxidation conditions. 29,30 . In accordance with the surface morphologies, the crosssectional morphology of the 0.3 at.%Y alloy showed the thinnest scale as shown in Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Under the present circumstances the diffusion of oxygen to the substrate became very slow, leading to a decrease in the overall oxidation rate because the relative area occupied by TiO 2 grains was particularly small. 29,30 This induced a significant decrease in the paths for oxygen diffusion and suppression of the growth of TiO 2 . Therefore, the outer protective Al 2 O 3 seems to act as a diffusion barrier to inhibit the overall development of the oxide scale.…”

Section: Discussionmentioning

confidence: 99%

“…Oxides Detected [27][28][29][30] Only the oxides of TiO 2 and a-Al 2 O 3 were present in the oxide scale except for the substrate TiAl in the Y-free alloy ( Fig. 4(a)).…”

Section: Scale Structures After Isothermal Oxidation At 800°cmentioning

confidence: 99%

“…In Al-rich TiAl-base alloys, the beneficial effect of Y with the proper amount at the initial stage of isothermal exposure, especially under cyclic exposure, has been studied in detail. 29,30 In the present work, the isothermal-oxidation behavior of Ti-50Al alloys containing various amounts of Y was studied after long-time exposure at 800 and 900°C. The main purpose was to evaluate whether Y additions have an identical beneficial effect on oxidation resistance of Al-rich TiAl-base alloys under long isothermal exposure on the basis of study of the effect of Y on the microstructure of the oxide scale.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Isothermal Oxidation Behavior of Ti-50Al Alloy with Y Additions at 800 and 900°C

Umakoshi

et al. 2006

Oxid Met

Self Cite

View full text Add to dashboard Cite

The isothermal-oxidation behavior of Al-rich TiAl alloys containing Y up to 1.0 at.% was studied in synthetic air with a flow of 200-250 mL/min at 800 and 900°C. Oxidation kinetics and scale adherence were studied in terms of the morphological features and microstructural evolution of the oxide scale. In the specimens oxidized at 800°C, all alloys containing 0.3-1.0 at.%Y showed reduced mass gain compared to the Y-free alloy, especially for the 0.3 at.%Y alloy. Under isothermal exposure at 900°C, the addition of small amounts of Y (0.1 and 0.3 at.%) was effective in enhancing the oxidation resistance. The alloys with higher Y contents (0.6 and 1.0 at.%), on the contrary, had a reverse effect on the oxidation resistance by providing rapid diffusion paths in the form of coarse Y 2 O 3 particles close to the substrate. The improvement of oxidation resistance of the alloy with Y additions was due partly to the improved adhesion of the scale and due partly to the formation of a continuous a-Al 2 O 3 layer in the outer scale. Y segregation and/or Y 2 O 3 precipitation at the oxide grain boundaries was effective in decreasing the oxidation rate and refining the oxide grains. The thinner scale was responsible for relaxing the thermal stress and, thus the cohesion between the scale and substrate was greatly improved in Y-containing alloys.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…Oxides Detected [27][28][29][30] Only the oxides of TiO 2 and a-Al 2 O 3 were present in the oxide scale except for the substrate TiAl in the Y-free alloy ( Fig. 4(a)).…”

Section: Scale Structures After Isothermal Oxidation At 800°cmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Isothermal Oxidation Behavior of Ti-50Al Alloy with Y Additions at 800 and 900°C

Umakoshi

et al. 2006

Oxid Met

Self Cite

View full text Add to dashboard Cite

show abstract

“…15a). The improvement of the oxidation resistance of TiAlbased alloys by small yttrium additions was attributed to the formation of a continuous alumina layer in the outer scale [55]. Precipitates of Y 2 O 3 at the oxide grain boundaries impeded oxygen diffusion and refined the oxide grains.…”

Section: Discussionmentioning

confidence: 99%

Oxidation behaviour of TiAl-based intermetallic coatings on γ-TiAl alloys

Braun

Fröhlich

Leyens

2010

International Journal of Materials Research

View full text Add to dashboard Cite

TiAl-based intermetallic layers with additions of Ag, Cr, Y and Hf were deposited on c-TiAl specimens using magnetron sputtering. The oxidation behaviour of the coated Ti-45Al-8Nb (at.%) alloy was investigated at 850 8C and 900 8C under cyclic oxidation conditions in air. The ternary Ti-50Al-2Ag (at.%) coating did not provide oxidation protection to the substrate material at 850 8C. Two-phase c-TiAl + Ti(Cr, Al) 2 Laves coatings exhibited high oxidation resistance at 900 8C for up to 1000 cycles of 1 h dwell time at high temperature. During thermal exposure phase dissolution and transformation occurred. The slow oxide growth rates observed for the Ti -Al -Cr intermetallic layers were associated with the formation of a thin continuous alumina top scale established by the Laves, B2 and Z-phases. Small additions of hafnium and yttrium improved the oxidation resistance. In contrast, Ti -Al -Cr -Ag coatings exhibited poor oxidation behaviour at 900 8C. R. Braun et al.: Oxidation behaviour of TiAl-based intermetallic coatings on c-TiAl alloys Int.

show abstract