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Graphical abstract Highlights • Si-Al composite coating was prepared on γ-TiAl alloy by a two-step method. • SiO 2 coating was electrodeposited on pack aluminizing coating. • Porous SiO 2 coating turns to be compact after oxidation. • The Si- and Al-enriched oxide scale provides good oxidation resistance. Abstract A novel Si-Al composite coating was prepared on γ-TiAl alloy by a two-step method. Firstly, an aluminizing coating was fabricated on γ-TiAl alloy via pack cementation technique. Then a SiO 2 coating was prepared on this aluminizing coating via cathodic electrodeposition. The high temperature oxidation resistance of this composite coating was evaluated under 1000 °C. During the oxidation process, this Si-Al composite coating can react with TiAl and prevent the inward diffusion of oxygen from air to the film/alloy interface, resulting in the remarkable decreased oxidation rate of the alloy. [ABSTRACT FROM AUTHOR]

A kind of Y-bearing ferritic/martensitic fuel cladding tube with qualified dimensions, acceptable mechanical properties as well as good flattening and flaring performance was manufactured recently by our group. In this paper, to improve and further evaluate its oxidation resistance, the cladding tube was aluminized firstly and then subjected to high temperature steam oxidation at 1200 °C for 8 h. The results indicated that aluminizing coating with gradient content of Al was prepared on the tube successfully. And the matrix microstructure was transformed from tempered martensite into ferrite during aluminizing. Weight gains after high temperature steam oxidation were 72.7 and 1.48 mg cm ^−2 for the bare and aluminized tubes, respectively. The latter one exhibited better oxidation resistance due to the generated dense aluminum oxide film. Meanwhile, Kirkendall pores were formed near oxidation surface and should be eliminated for the real application of the aluminized tube in the future.

Low-temperature aluminizing coating was prepared onto the surface of oil casing steel N80 with a magnetron-sputtered Al film to improve its corrosion resistance. Results show that magnetron-sputtered Al film is able to form gradient aluminide coating, composed of iron aluminide FeAl3, Fe2Al5 and Fe3Al with different contents of aluminum. Both the density and continuity of iron aluminide layer for oil casing steel N80 with magnetron-sputtered Al film can be improved. Under the same corrosion condition, aluminized oil casing steel N80 with a magnetron-sputtered Al film shows an outstanding corrosion resistance than those of original and aluminized ones without magnetron-sputtered Al film. The positive effect of Al film is considered as the concentration change of active Al atom for diffusion to form the aluminizing coating during the pack processing. [ABSTRACT FROM AUTHOR]

Abstract: Using a halide-activated pack-cementation method but at a temperature (600°C) noticeably lower than normal, an η-Fe2Al5 coating and two δ-Ni2Al3 coatings with and without dispersions of CeO2 nanoparticles were developed respectively on a low-carbon steel and the steel pretreated with an electrodeposited film of Ni or Ni–CeO2. The erosion–corrosion (E–C) performance of the three aluminide coatings during 100h exposure at ~600°C in a coal-firing laboratory-scale fluidized-bed combustor (FBC) was investigated, by mounting the aluminized samples onto a rig which maintained rotation for accelerating the relative impacting speed of flying solid particles (mainly SiO2 bed materials). The η-Fe2Al5 and the CeO2-free δ-Ni2Al3 coatings experienced an unacceptable recession rate. Compared to the two CeO2-free aluminide coatings, the CeO2-dispersed δ-Ni2Al3 coating offered profoundly improved E–C resistance, because the latter coating was not only strengthened by the CeO2 dispersion and grain refinement, it also could grow a more adherent alumina scale. [Copyright &y& Elsevier]

A novel Al–Si composite coating was fabricated on γ-TiAl by the combination of magnetron sputtered Al coating and subsequently electrodeposited SiO 2 coating. The oxidation performance of the specimens was evaluated in static air at 900 °C. Results shown that the Al–Si composite coating can act as an efficient oxygen migration barrier and provide good oxidation resistance. During the oxidation process, an Al 2 O 3 enriched layer formed beneath the composite coating. The interfacial reaction between the composite coating and alloy resulted in the generation of Al 2 O 3 and Ti 5 Si 3. Image 1 • A novel Al–Si composite coating was fabricated on γ-TiAl by a two-step method. • This Al–Si composite coating can prevent the formation of Al-depletion layer. • The interfacial reaction between the composite coating and alloy resulted in the generation of Al 2 O 3 and Ti 5 Si 3. • This Al–Si composite coating can reduce the coating/alloy interface hardness and improve the oxidation resistance. [ABSTRACT FROM AUTHOR]