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Abstract Ni-xAl-Y 2 O 3 (x = 14.5 or 17.6 wt%) coatings were developed by vacuum annealing the electrodeposited Ni-Al-Y 2 O 3 composite coatings with dispersed Al and Y 2 O 3 microparticles in Ni matrix at 800 °C for 3 h. For comparison, pure Ni-xAl (x = 15 or 18 wt %) coatings were also produced in the same condition. The results indicated that all coatings consisted of γ′-Ni 3 Al+β-NiAl and the addition of Y 2 O 3 refined the grain of alloy coatings. Cyclic-oxidation at 900 °C showed that the alumina scale adhesion increased with the increase of Al content and Y 2 O 3 further improved the adhesion of alumina scale due to the beneficial effects of Y 2 O 3 reducing void formation at the scale/coating interface. Together with this, the produced Ni-Al coatings exhibited better cyclic oxidation than cast Ni 3 Al alloy and Ni-17.6Al-Y 2 O 3 coating even exhibited a comparable cyclic oxidation as cast β-NiAl alloy. Highlights • All Ni-Al coatings produced consisted of γ′-Ni 3 Al and β-NiAl and the codeposited Y 2 O 3 particles refined the grain of alloy coatings. • The alumina scale adhesion formed on Ni-Al coatings with and without Y 2 O 3 increased with the increase of Al content. • Ni-15Al and Ni-18Al coatings exhibited better cyclic oxidation than cast γ′-Ni 3 Al alloy. • The addition of Y 2 O 3 further improved the alumina scale adhesion formed on Ni-14.5Al and Ni-17.6Al coatings. • Ni-17.6Al-Y 2 O 3 coating exhibited a comparable cyclic oxidation resistance as cast β-NiAl alloy. [ABSTRACT FROM AUTHOR]

Abstract: An Al2O3-modified aluminide coating was produced by aluminizing an as-electrodeposited Ni–Al2O3 nanocomposite film using pack cementation method at 1100  C for 4 h. For comparison, aluminizing was also performed in the same condition on an as-deposited Ni film without Al2O3 nanoparticles. SEM/EDAX and TEM results indicated that the co-deposited Al2O3 nanoparticles were homogeneously dispersed in the finer-grain nanocrystalline Ni grains. The isothermal and cyclic oxidation in air at 900 °C indicated that the Al2O3-modified aluminide coatings were profoundly oxidation resistant as compared to the Al2O3-free aluminide coatings due to the faster formation of a continuous adherent α-Al2O3 scale. The effect of Al2O3 on the microstructure and the oxidation of the aluminide coating are discussed in the detail. [Copyright &y& Elsevier]

Abstract: A CeO2-dispersed aluminide coating was fabricated through aluminizing the electrodeposited Ni–CeO2 nanocomposite film on carbon steel using pack cementation method at 700 °C for 4 h. The isothermal and cyclic oxidation behavior of the CeO2-dispersed aluminide coating at 900 °C, including the growth of oxide scale and the microstructure of the coatings, have been investigated comparing with the aluminide coating on carbon steel. The results show enhanced oxidation performance of the CeO2-dispersed aluminide coating, which is concerned with not only CeO2 effect on the microstructure and oxidation, but also decreased interdiffusion between the aluminide and the Ni film. The CeO2 benefit effects and interdiffusion are discussed in detail. [Copyright &y& Elsevier]

Abstract: The electrodeposited two-phase γ-Ni+γ′-Ni3Al and single-phase γ′-Ni3Al coatings with and without CeO2 particles were developed by the conversion of electrodeposited Ni–Al or Ni–Al–CeO2 films with dispersed Al microparticles in Ni matrix into γ′-Ni3Al by vacuum annealing at 800°C for 3h. SEM/EDAX and TEM characterizations showed that the CeO2-dispersed γ-Ni+γ′-Ni3Al or γ′-Ni3Al coatings exhibited finer grains compared to the CeO2-free Ni–Al alloy coatings. The oxidation at 1000°C for 20h showed that for a given Al content the addition of CeO2 significantly improved the oxidation resistance of the electrodeposited Ni–Al alloy coatings. The effect of CeO2 particles on the microstructure and oxidation behavior of the electrodeposited Ni–Al alloy coating is discussed in detail. [Copyright &y& Elsevier]