Tribological performance of mechanical face seals for Martian applications

This study examines the tribological performance of dry-running mechanical face seals composed of a graphite rotating ring and a silicon carbide stationary ring under varying spring preload conditions, both in clean operation and in the presence of a Martian regolith simulant (MGS-1, PR < 80 µm). Three preload levels were applied: zero preload (SP0, 0 MPa), nominal preload (SP1, 0.197 MPa), and double preload (SP2, 0.394 MPa), based on a calibrated spring characteristic and contact area analysis. Under clean conditions, increasing preload elevated frictional torque from ~ 0.017 Nm (SP0) to ~ 0.030 Nm (SP1) and ~ 0.070 Nm (SP2), indicating a direct correlation between contact pressure and interfacial shear. When MGS-1 regolith simulant was introduced, torque increased significantly in all configurations, reaching ~ 0.064 Nm (SP0MGS), ~ 0.082 Nm (SP1MGS), and ~ 0.095 Nm (SP2MGS). Real-time monitoring of torque and axial force enabled the calculation of dynamic friction forces and coefficients of friction, which revealed that preload strongly influenced wear mechanisms: higher preload enhanced interface conformity but accelerated abrasive degradation, while lower preload reduced wear at the expense of sealing pressure. Scanning electron microscopy (SEM) confirmed the presence of abrasive grooves and embedded particles exclusively on the graphite ring, with no perceivable damage on the SiC counterface. The results demonstrate that nominal preload (SP1) provides the most favorable balance between friction stability, wear resistance, and sealing reliability, offering valuable insights for the design of mechanical seals in particulate-laden environments such as Martian surface operations.