High Nb-TiAl-based porous composite with hierarchical micro-pore structure for high temperature applications

Porous TiAl alloys are anticipated to become next-generation high temperature structural filtration materials due to their promising applications in the field of high temperature gas/solid and liquid/solid two-phase separation. However, poor high temperature oxidation resistance at elevated temperatures greatly limits the use of the alloys for practical applications. Here, a novel TiAl/Ti3Al/Nb2Al/Ti5Si3/Al2O3 porous composite with hierarchical micro-pore structure has been developed by manipulating chemical reactions to improve the anti-oxidation properties of high Nb-TiAl-based alloys at elevated temperatures. Several characterization methods were used to investigate the phase transformation mechanism of the porous composites, including scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectrometry (EDS). The results show that the porous composites possess slow oxidation kinetics and the weight gain during oxidation declines as the Nano-SiO2 content increases after the 900 degrees C/100 h isothermal treatment. A minimum weight gain of 3.68 g/m(2) is achieved for the composite with 6 wt% Nano-SiO2 particles after the isothermal treatment. The porous composite's excellent anti-oxidation properties are mainly attributed to the synergistic effect of Al2O3 and Ti5Si3 generated by the Nano-SiO2 reaction of TiAl and Ti3Al, which suppresses the O inward diffusion and Ti outward diffusion. This study provides additional insights into high temperature applications of TiAl-based porous alloys. (C) 2018 Elsevier B.V. All rights reserved.