Abstract: Friction and wear characteristics of 150SN base oil and oils containing ammonium thiophosphate (T307) were evaluated by an improved four-ball tester with or without magnetic fields. The morphologies of worn surfaces lubricated with tested oils were observed by scanning electron microscope (SEM), and the effect of the magnetic field, loading and T307 dosage on tribological properties of the oils was analyzed. The results indicate that the wear scar diameters in the magnetic field lubricated with the blank oil are smaller than those in non-magnetic field, the friction coefficients in magnetic field are larger than those without magnetic impact. Furthermore, the wear scar diameters and friction coefficients lubricated with T307-doped oils under the magnetic conditions are larger, indicating the negative effect of magnetic field on tribological performance of formulated oils. The magnetic field has an unfavorable effect for the formation of lubrication film on the metal surface through tribochemical reactions between T307 and metal surface.

Key words: magnetic filed, ammonium thiophosphate, lubricants, friction, wear