The Effect of Stress and TiC Coated Balls on Lifetime of a Perfluoropolyalkylether Using a Vacuum Rolling Contact Tribometer

Abstract

A vacuum spiral orbit tribometer (SOT) was used to determine the relative lifetimes of a branched perfluoropolyalkylether (PFPAE) on 440C stainless steel. The effect of varying the mean Hertzian stress (0.75, 1.0, 1.5 and 2.0 GPa) and the use of TiC coated balls on lubricant lifetime was studied. Other conditions included: ∼100 rpm, ∼50 μg of lubricant, an initial vacuum level of < 1.3 × 10⁻⁶ Pa (< 1.0 × 10⁻⁸ Torr), and room temperature (∼23 °C). Increasing the mean Hertzian stress from 0.75 to 2.0 GPa results in an exponential decrease in lubricant lifetime for both material combinations. However, substituting a TiC ball for the 440C ball quadrupled lifetime at low stress levels (0.75 and 1.0 GPa) and doubled life at higher stresses (1.5 and 2.0 GPa). The reduced reactivity of the TiC surface with the PFPAE lubricant is considered to be the reason for this enhancement. Decreasing lifetime with increasing stress levels correlated well with energy dissipation calculations.

Presented as a Society of Tribologists and Lubrication Engineers Paper at the ASME/STLE Tribology Conference in Seattle, Washington, October 1–4, 2000

KEY WORDS:

• Aerospace Tribology
• Ball Bearings
• Perfluoropolyalkylether

Notes

Presented as a Society of Tribologists and Lubrication Engineers Paper at the ASME/STLE Tribology Conference in Seattle, Washington, October 1–4, 2000