Microstructure, Mechanical, and Tribological Properties of SiC-AlN-TiB2 Multiphase Ceramics

SiC multiphase ceramics were prepared via spark plasma sintering using AlN and TiB2 as the second phase and Y2O3 as a sintering additive. The effects of TiB2 content (10 vol.% and 20 vol.%) and sintering temperature (1900 degrees C to 2100 degrees C) on the phase composition, microstructure, and mechanical and tribological properties of SiC multiphase ceramics were investigated. The results showed that Y2O3 reacts with Al2O3 on the surface of AlN to form the intercrystalline phase Y4Al2O9 (YAM), which promotes the densification of the multiphase ceramics. The highest density of SiC multiphase ceramics was achieved at 10 vol.% TiB2 content. Moreover, TiB2 and SiC exhibited good interfacial compatibility. In turn, a thin solid-solution layer (similar to 50 nm) was formed by SiC and AlN at the interface. The periodic structure of SiC prevented the dislocation movement and inhibited the base plane slip. The most optimal mechanic characteristics (a density of 98.3%, hardness of 28 GPa, fracture toughness of 5.7 MPa.m(1/2), and bending strength of 553 MPa) were attained at the TiB2 content of 10 vol.%. The specific wear rates of SiC multiphase ceramics were (4-8) x 10(-5) mm(3)/N.m at 25 degrees C and 2.5 x 10(-5) mm(3)/N.m at 600 degrees C. The wear mechanism changed from abrasion at 25 degrees C to a tribo-chemical reaction at 600 degrees C. Therefore, adding lubricious oxides of TiB2 is beneficial for the improvement in wear resistance of SiC ceramics at 600 degrees C.