Positive effects of pre-oxidation on high temperature oxidation behavior of TiAl composites with multilayered structure

Abstract

In order to study the pre-oxidation on high temperature oxidation behavior of TiAl composites with high-efficiency, the TiAl composites with multilayered structure were successfully prepared via spark plasma sintering (SPS) by introducing 0.5 wt% BN, 0.5 wt% GO, and 0.3 wt% SiC, respectively. The TiAl alloy was dual-phase microstructure due to sintering temperature of 1250 °C. TiAl composites also exhibited dual-phase microstructure, in which the second particles distributed at the lamellar grain boundaries or precipitated at the interface of α2 and γ lamellae were depended on the reinforcements. The effects of pre-oxidation (850 °C for 2 h in high purity oxygen) on the isothermal oxidation behaviors (850 °C for 100 h in air) of TiAl composites were investigated. The present results demonstrated that the TiAl alloy, TiAl-GO composite, and TiAl–SiC composite exhibited excellent oxidation resistance after pre-oxidation. While the TiAl-BN composite displayed poor oxidation after pre-oxidation. The micron-sized TiO2 was formed in TiAl-BN composite after pre-oxidation, which can not inhibit atom diffusion during isothermal oxidation, resulting in fast growth of oxidation layer. However, the nano-sized Al2O3 particles on the surfaces of TiAl alloy, TiAl-GO composite, and TiAl–SiC composite after pre-oxidation can effective hinder atom diffusion during isothermal oxidation, resulting in a slow growth of oxidation layer.

Keywords

• TiAl alloy
• Composites
• SPS
• Pre-oxidation
• Oxidation behavior