The effect of Y-ion implantation on the oxidation of ?-NiAl

Schumann, E.

doi:10.1007/bf01046752

Cited by 90 publications

(22 citation statements)

References 29 publications

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“…The growth rate of the oxide scale was significantly decreased and the diffusion of oxygen along the grain boundaries strongly controls the overall oxidation rate. 40 Similar work has been done by Okabe 20 and Taniguchi and Shibata 25 in Fe-Cr-Al alloys with minor additions of Hf and Zr. They reported that the resistance to cyclic oxidation of the alloys was also improved by the formation of HfO 2 protrusions which enhanced adherence of the scale and substrate.…”

Section: Discussionsupporting

confidence: 59%

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

Umakoshi

et al. 2006

Oxid Met

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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.

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Section: Discussionsupporting

confidence: 59%

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

Umakoshi

et al. 2006

Oxid Met

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“…Metal protrusions have been observed in other alumina-forming systems [33,34]. With the overlying oxide being approximately the thickness of the transformed (voidcontaining) oxide, the misoriented grain may remain from initial, random nucleation of α-Al 2 O 3 grains at the metal-scale interface [35,36].…”

Section: Nial+hfmentioning

confidence: 97%

Characterization of thermally cycled alumina scales

Pint

Wright

et al. 2000

Materials at High Temperatures

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Cross-sectional transmission electron microscopy was used to characterize the alumina scales formed on several Ni-base alumina-formers. The alumina scale microstructure of Ni20at%Cr-19Al-0.05Y after 100, 1h cycles at 1100°C was compared to an isothermally-grown scale. Despite being near the onset of mass loss in cyclic testing, very few defects were noted in either scale microstructure. The more adherent scales that form on Hf-doped NiAl and Ni49at%Al-2Cr were also characterized. With the addition of Cr, the formation of α-Cr precipitates at the metal-oxide interface coincided with increased long-term scale spallation. No similar precipitation mechanism was observed to be associated with scale spallation on NiCrAlY.

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“…Although the scale consisted only of Al 2 O 3 layer for the Al 2 O 3 -forming alloys in contrast to the present Al-rich TiAl alloys, various oxide layers containing Al 2 O 3 and TiO 2 with different morphologies were formed. The segregation of Y or Y 2 O 3 may not only limit the growth of grains, but also act to block the diffusion paths [30]. Therefore, the outer protective Al 2 O 3 seems to act as a diffusion barrier to inhibit the entry of oxygen, and reduction of the diffusion rate of oxygen seems to be responsible for the thinning of the scale.…”

Section: Discussionmentioning

confidence: 99%