Sliding Friction and Wear Characteristics of Novel Graphitic Foam Materials

While the use of ORNL developed high-thermal-conductivity graphitic foam materials has been focused on thermal management applications, recent experiments have revealed their potential as bearing surfaces as well. The three primary tribological advantages are: (1) they can efficiently remove frictional heat, (2) their natural porosity can trap wear debris, and (3) their porosity can serve as a lubricant reservoir for the contact surface. A series of pin-on-disk experiments were conducted at both room temperature and 400 °C to compare the sliding friction and wear characteristics of the densified graphitic foam (mated against M-50 tool steel or against alumina) to those of conventional bearing materials like graphite, bearing bronze, poly- tetrafluoroethylene, bearing steel, and a Co-based superalloy. At room temperature and under low contact pressure, the tribological behavior of the densified graphitic foam material was comparable to that of graphite and better than that of other bearing materials. At 400 °C, traditional graphite exhibited a dusting wear regime accompanied by a high friction coefficient. In contrast, the graphitic foam demonstrated an ability to maintain low friction and wear at that temperature.