Tribology of Self-Lubricating Metal Matrix Composites

Abstract

Self-lubricating metal matrix composites (SLMMCs) are a class of materials that have potential to help engineers meet the demands of global initiatives for green manufacturing and sustainability. While SLMMCs have existed for many decades with traditional lubricant materials like graphite and other lamellar solids, such as MoS2, WS2, h-BN and CaF2, BaF2, scientists have recently incorporated nanostructured versions of the materials (e.g., carbon nanotubes and graphene). At the same time, new manufacturing and processing techniques have come online, such as additive manufacturing techniques that may provide significant innovation for SLMMCs. In this chapter, the current state of SLMMC research is reviewed, including materials, processing methods, and tribological performance. Processing and property relationships are described, such as influence of testing parameters and content of solid lubricants on friction and wear. Improvements in tribological behavior, as much as possible, are interpreted through third-body approach, which emphasizes materials phenomena at the sliding interface – including mechanical, structural, and chemical changes to the parent materials. Based on the review of SLMMCs and their tribology, recommendations for future research are made that emphasize the use of new materials, new processing routes, and research approaches that seek to reveal more completely the mechanisms by which these materials form tribofilms that are effective at lowering friction and reducing wear.