Investigation on the effect of coal dust on friction performance of heavy duty gear oil

Purpose In response to the issue of abnormal reducer operation caused by unreasonable maintenance of coal mine equipment lubrication systems contaminated by coal dust, this study aims to investigate the impact of coal dust on the friction performance of lubricating oil. Design/methodology/approach 200-mesh anthracite particles were selected as contaminants. The effects of particle concentration and load on lubricant friction properties were investigated through four-ball friction tests, scanning electron microscopy, energy-dispersive spectroscopy and X-ray photoelectron spectroscopy analysis. Validation was conducted on a gear test bench, with gear wear observed using an iron content analyzer and a 3D profilometer. Findings The PB value of lubricating oil decreases as the mass fraction of coal particles increases. As the mass fraction of coal particles increases, the lubricating oil’s coefficient of friction and wear scar size first increase then decrease under high-speed light-load conditions; under low-speed heavy-load conditions, they first decrease then increase. At low loads (≤80 kgf), coal particles exacerbate friction; under high loads (>80 kfg), the mending effect of coal particles becomes dominant, thereby reducing wear. Originality/value The study revealed the mechanism by which load affects the contamination of lubricating oil by coal particles. Coal particle contamination is not solely detrimental. Under high loads, its lubricating effect becomes dominant, providing a theoretical basis for optimizing oil change cycles and maintenance schedules in lubrication systems. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2025-0376/