The effect of a ZnDTP Anti-Wear Additive on the Micropitting Resistance of Carburised Steel Rollers

Micropitting is a microscopic form of rolling contact fatigue and wear, which is most often found in ground, hard steel surfaces such as those in case-hardened gears. It is normally associated with concentrated rolling-sliding contacts under conditions where the lubricant film is rather thin compared to the height of the surface roughness.

Here, the results of a study of the effect of lubricant composition are reported. A PA0 base stock was tested on its own and with a ZnDTP anti-wear additive, which is a common constituent of engine and transmission oils. The experimental results showed that the anti-wear additive has an unfavourable effect on micropitting. A possible new mechanism that might account for the results is discussed.