Stability of reinforcements (CrB2/TiB2) and lubricants (C/MoS2) in Cu matrix during the sintering process

To select suitable reinforcement and lubricant for Cu matrix and thus improve the tribological performance, the stability of widely used reinforcements and lubricants, such as CrB 2 , TiB 2 , graphite (C) and MoS 2 , in the copper matrix during sintering process was studied. The content of each reinforcement or lubricant was fixed at 10 wt%, and the powder mixture was sintered by a fast hot-pressed sintering machine at 950 °C under 40 MPa for 1 h under a vacuum atmosphere (<10 Pa). Then, microstructure and phase composition of the composites resulted from 10%CrB 2 –Cu, 10%TiB 2 –Cu, 10%MoS 2 –Cu, 10%C–Cu, 10%CrB 2 –10%C–Cu, 10%TiB 2 –10%C–Cu, 10%CrB 2 –10%MoS 2 –Cu and 10%TiB 2 –10%MoS 2 –Cu powder systems were investigated systematically, Subsequently, the potential decomposition and reaction behavior was discussed based thermodynamic analysis. Results show that single CrB 2 , TiB 2 or C phase can exist stably in copper matrix, but MoS 2 is prone to react with Cu to form Cu 2 S and Mo 2 S 3 . Both CrB 2 and TiB 2 can co-exist with C in the Cu matrix, but react with MoS 2 to form Cu 2 S, Mo 2 S 3 as well as ternary CuCrS 2 and CuTi 2 S 4 phase, since the negative Gibbs free energy change of the corresponding reaction equations. Finally, the strengthening effect of CrB 2 and TiB 2 along with the lubricating effect of graphite (C) are promise to work in Cu matrix from the viewpoint of crystal structure integrity.