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Manufacturing and Tribological Behavior of Self-Lubricating Duplex Composites: Graphite-Reinforced Polymer Composites and Polymer-Infiltrated Metal Networks Yinyin Zhang, David Chern, Robert Schulz, Janine Mauzeroll, and Richard R. Chromik Submitted: 6 August 2020 / Revised: 4 October 2020 / Accepted: 1 November 2020 Self-lubricating duplex composites comprising a top layer of polymer-based composites, i.e. bismaleimide (BMI) filled with a wide range of graphite (Gr) content (0–55 wt.%), and a bottom layer of infiltrated metal networks were manufactured by a hot compression-molded method. Melting points and polymerization temperatures of as-received BMI powder and BMI + Gr blends were investigated to determine infiltration process. The polymerization peaks move to higher temperatures with increase in graphite content. For cured polymer composites, the hardness measured by nanoindentation keeps increasing with graphite content without degradation up to 55 wt.%. Tribological performance of the top and bottom composites was examined individually, with focus placed on the development and stability of lubricating transfer film and tribofilm. For the top polymer composites, 25 wt.% Gr (or equivalently 17 vol.%) is sufficient to form lubricating transfer film and reduces the friction to the lowest  0.15. For the bottom infiltrated metal networks, the BMI + 55% Gr-infiltrated network is adequate to develop fully covered transfer films and achieve low friction throughout the test. Those results shed lights on design and manufacturing of selflubricating polymer matrix composites on metallic components that undergo severe running conditions. Keywords

friction, polymer-based composites, self-lubricating duplex composites, transfer film

1. Introduction Rapidly growing concerns for environmental sustainability and energy consumption have driven demands for longer lifetime and higher efficiency of transportation and industrial infrastructure (Ref 1, 2). A recent study by Holmberg et al. Ref 2 demonstrated that a substantial amount of energy, i.e.  20% of total energy globally, is lost due to friction and wear; 18– 40% of the energy loss can be eliminated by advanced developments in tribology such as lubricants, new materials and designs. Among those advanced design strategies are selflubricating composites, which are an important class of materials that incorporate solid lubricants into a matrix to provide continuous replenishment of lubricant throughout service (Ref 3, 4). This design often meets requirements when materials are subjected to extreme conditions, such as high Yinyin Zhang, Department of Materials Engineering, McGill University, 3610 University Street, Montreal, QC H3A 0C5, Canada; and Ecole des Mines de Saint-Etienne, SMS Division, 42023 SaintEtienne, France; David Chern and Richard R. Chromik, Department of Materials Engineering, McGill University, 3610 University Street, Montreal, QC H3A 0C5, Canada; Robert Schulz, Hydro-Que´bec Research Institute (IREQ), Varennes, QC J3X 1S1, Canada;