Tribological behavior of aeronautical steel under oil-air lubrication containing extreme-pressure and anti-wear additives

If the lubrication system of a helicopter reducer is compromised, its gears and bearings will be in a working state without lubricating oil, which causes the reducer to be damaged in a very short time. Various 2% additives of T307, T321, T202, and T391 were injected and mixed with DOD-L-85734 aeronautical oil to produce 45-min oil-air lubrication experiments performed upon 12Cr2Ni4A aeronautical steel tribo-pairs. The results show that the best anti-wear effect is produced by oil-air lubrication containing T391: its wear width under jetting oil-air just three times and quantity of oil used only 0.015 mL in 45 min was only 421.32 μm but that of dry friction for 48 s was 629.20 μm. The technology of oil-air lubrication that contains an extreme-pressure and anti-wear additive is thus a feasible way to improve the operational ability of a helicopter transmission system that is out of oil.