Development of wear and pitting curves with vibration analysis for lubricating grease under contamination conditions

The application of grease under contaminated environmental conditions typically leads to its degradation and subsequent damage to lubricated surfaces. This study examines the effects of various concentrations of environmental particles and water content, both separately and in combination, on the variation of tribological characteristics of lithium-based grease during wear. Wear and pitting curves are established for grease contaminated with varying weight percentages of water and particles. The introduction of water into grease reduces wear by absorbing friction heat but increases pitting, while particles extend the running-in period and destabilize surface roughness. In mixed conditions, particles exert a greater influence on the tribological behavior than water. To improve pitting monitoring, vibration indicators FM4 and NA4 are modified by incorporating the cumulative effect of the friction coefficient over time, accounting for the progressive accumulation of wear and vibration energy. The modified FM4 indicator proves more effective in detecting pitting variations under contaminated conditions.