Abstract: The sintering materials prepared by hot pressing were irradiated by Gamma ray at different dose rates. These materials were composite ceramics commonly used in mechanical seals equipped in the rotating machineries of nuclear power plant. The thermal and mechanical properties were measured. The friction experiments were also carried out under water lubrication at room temperature by a Plint TE-92 tribo-machine. The morphology of the worn surfaces was observed using scanning electron microscopy and ZYGO. The results show that γ irradiation had little effect on the thermal and mechanical properties of the sintering materials. Mild wear occurred during the friction experiments with friction coefficients of 0.04~0.06 under water lubrication. Irradiation had little effect on the friction property of the sintering materials.