Search

In this study, SiO2 coating was electrodeposited on Ti45Al8.5Nb alloy to enhance its oxidation resistance at 900 °C. The focus was on the interaction between SiO2 coating and the alloy substrate, and specifically, the role of the Nb element in this context. The formation of a SiO2/(Ti, Nb)O2/Ti5Si3 + Al2O3 three-layer oxide scale significantly inhibits the inward diffusion of oxygen. Beyond the characteristic Ti5Si3 + Al2O3 layer at the interface, the Nb2Al phase embedded within Ti5Si3 was observed. Concurrently, the presence of a (Ti, Nb)O2 layer was confirmed. The relationship between the coating thickness and oxidation resistance was also investigated. It was found that the thickness of the SiO2 coating affects the density of the oxide scale and the inward diffusion rate of oxygen. Moreover, due to the good adhesion to the substrate, the derived oxide scale exhibited good anti-peeling performance when subjected to a cyclic oxidation test. [ABSTRACT FROM AUTHOR]

Localized corrosion triggered by inclusions is prone to metallic material failure. Except for chemical dissolution of some special inclusions, the principle of galvanic coupling is the most acceptable theory to explain the above corrosion damage mechanism over the past decades. Still, controversies continue to present, in particular, mounting recent evidence obtained by advanced technologies emphasizes the limitations of previous entrenched idea and discloses unexpected results. Here, we review relevant recent studies and carefully summarize their similarities and differences to reduce the knowledge gap between inclusion-triggered localized corrosion and material design, whilst the source of typical inclusions is treated and discussed. [ABSTRACT FROM AUTHOR]

The low density, high specific strength, and good creep properties make TiAl alloys being promising high-temperature structural materials in aerospace and automotive industries. However, the insufficient oxidation resistance limits their extensive practical applications. It is the intention of this review to illustrate the mechanism and development of sol–gel-based coatings, a surface modification approach for oxidation protection of TiAl alloys, but not to present a general review on the oxidation protection of TiAl alloys. The oxidation behavior and mechanism of TiAl alloys were addressed briefly. The discussion focused mainly on the sol–gel coatings preparation method and generation mechanism. Finally, the development trend of sol–gel-based coatings for high-temperature oxidation of TiAl alloys was prospected. [ABSTRACT FROM AUTHOR]