Torsional Fretting Wear Behavior of Bonded MoS₂ Solid Lubricant Coatings

Abstract

The effects of applying a bonded MoS₂ solid lubricant to a 1050 steel substrate were investigated using a torsional fretting wear apparatus. Tests were conducted under a normal load of 50 N with angular displacement amplitudes ranging from 0.1 to 5°. Wear scars were examined using scanning electron microscopy, energy-dispersive X-ray spectrometry, optical microscopy, and surface profilometry. The MoS₂ coating exhibited different torsional fretting regimes than those of the substrate. Fretting regimes of the coating were primarily in the partial slip regime (PSR) and the slip regime (SR) with no mixed fretting regime. The width of the PSR narrowed. Due to the lubricating effects of the coating, the friction torque was consistently lower than that of the substrate. The damage to the coating in the PSR was very slight, and its granular structure remained even after 1,000 cycles. The damage mechanism to the SR coating was a combination of abrasive wear, oxidative wear, and delamination. The MoS₂ coating had potential to alleviate torsional fretting wear.

KEY WORDS:

• Fretting Wear
• Torsional Fretting
• Bonded MoS₂ Solid Lubricant Coating
• 1050 Steel
• Damage Mechanism

FUNDING

This work was supported by the Yangtze River Scholars and Innovation Team Development Plan (No. IRT1178), Joint Foundation of Guizhou (No. LKG[2013]09), and the University of Guizhou Province Engineering Research Center Project (No. [2012]023).