Effect of TiO2 addition on the densification behavior, microstructure and mechanical properties of Al2O3-Cr cermets prepared via vacuum sintering

Five cermets with composition of Cr-(45-x)Al2O3-xTiO2 (x = 0, 2, 4, 8 and 16 wt%) were prepared by vacuum sintering. The effects of TiO2 addition on the densification behavior, phase composition, microstructure and transverse rupture strength (TRS) of the prepared cermets were studied. The addition of TiO2 decreased effectively the full densification temperature of Al2O3-Cr cermets from 1700 °C to 1500 °C. A new Cr2Ti6O15 phase formed in the Al2O3-Cr cermets with 2-16 wt% TiO2 additions sintered at 1500 °C, and its volume fraction increased gradually with increasing TiO2 additions. The Cr2Ti6O15 phase improved the microstructure and decreased the porosity for cermets with 2 wt% TiO2 additions, accordingly resulting in the highest TRS of 447 MPa. However, when the addition of TiO2 exceeded 8.0 wt%, lots of residual pores exhibited in the Cr2Ti6O15 phase of those cermets, obviously reducing the TRS.