Abrasion Behaviour of Natural and Composite Polytetrafluoroethylene Seal Materials Against Stainless Steel in Lunar Regolith Conditions

In this paper, the abrasive effects of lunar simulant regoliths (LHS-1, LMS-1) have been investigated. Sealing performance of different sealant pin materials on stainless steel has been tested by the pin-on-disc method. Pin materials included block types such as pure polytetrafluoroethylene (PTFE), composite PTFE, as well as braided PTFE and hybrid-composite braided PTFE. Tribological properties were evaluated based on measured friction, wear, surface roughness and scanning electron micrographs. Most significant differences were observed in the sealing effect of the pins between the braided and the block-type pin materials. The stainless steel/pin pairs showed significantly higher (0.4–0.5) friction coefficients for the braided pins than the block ones (0.2–0.3), while there was not a significant difference in the abrasive effect of the different lunar regoliths. Although significant wear of the steel part occurred only with the block-type pins, this disadvantage was apparent in comparison with the braided pins. The abrasive particles caused deformation and eventually complete disintegration of the braided pins. Both the coefficient of friction and the wear could be estimated by a multiple linear regression model, in which different regolith size was the dominant independent parameter for the various pins.