Effect of Addition on Oxidation Resistance of Ti3SiC2 Matrix Composites

Ti₃SiC₂ and three different kinds of Ti₃SiC₂ matrix composites (Ti₃SiC₂/SiC, Ti₃SiC₂/Al₂O₃ and Ti₃SiC₂/MgAl₂O₄) were fabricated by reactive hot pressing method. The oxidation resistance of four kinds of materials at 1373 K-1773 K was investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results showed that the main oxidation products of Ti₃SiC₂ were rutile and cristobalite. The oxidation layers were composed of two layers, the outer was consisted of TiO₂, and the inner was a two-phase mixture of TiO₂ and SiO₂. A large number of pores existed in oxide layers which leading to a poor oxidation resistance. For Ti₃SiC₂ matrix composites, rutile grains in oxidation layers were refined due to the introduction of the second phase. The volume expansion caused by reactions between Al₂O₃ (or MgAl₂O₄) and TiO₂ could close pores and improve the densification of oxide layers, which further improve the oxidation resistance of Ti₃SiC₂/Al₂O₃ and Ti₃SiC₂/MgAl₂O₄. As for the oxidation of Ti₃SiC₂/SiC, the SiO₂ content in oxidation layers was increased from the oxidation of SiC. The dense SiO₂ layer acted as a protective film which could prevent the inward diffusion of oxygen. Moreover, liquid phase under high temperature could also fill the pores in oxidation layers. Thus, Ti₃SiC₂/SiC composite had the best oxidation resistance among three Ti₃SiC₂ matrix composites.