Double Pressing/Double Sintering on Properties of Lead-Free FeS/Cu–Bi Self-Lubricating Composites

Lead-free FeS/Cu–Bi (FCB) composites consist of a CuSn10 matrix, FeS, and Bi lubricants. In this study, lead-free FCB self-lubricating composites were prepared using repeated pressing and sintering. Single-press sintered (SS) FCB composites were also prepared for comparison. The mechanical and tribological properties of FCB materials with different FeS contents under the double-pressing/double-sintering (DPDS) process and SS were studied. Results showed that the mechanical properties of the FCB composite with DPDS (DPDS-FCB) were significantly improved compared to those of the FCB composite prepared by SS (SS-FCB). DPDS did not change the decreasing trend of the mechanical properties of the FCB composites with an increase in the FeS content. Moreover, DPDS significantly improved the tribological properties of the FCB composites. The antifriction effect and wear resistance of the FCB composites with optimal FeS content (6%) were improved by 22.6% and 300%, respectively. The improvement in the antifriction effect and wear resistance of the FCB composites prepared by DPDS largely depended on the mechanical support provided by the matrix. When the strength of the DPDS-FCB material was sufficient to support the load, the lubricating phase played a decisive role in the friction and wear behavior, which manifested as an increase in the optimal lubricant content in the FCB material and the lubricant content in the sliding interface of the friction pair.