On the Mechanism of Lubricant Film Failure in Sliding Concentrated Steel Contacts

Abstract

The lubrication mechanism of fully submerged sliding point contacts of AISI 52100 steel has been studied as a function of surface roughness and oxygen content of the lubricant. Strong indications are found that, at relatively low values of normal load and sliding speed, a partial elastohydrodynamic lubricant film (incompletely) separates the surfaces. This film survives asperity contacts because newly formed contacts oxidize rapidly. Collapse of the lubricant film occurs if oxidation can no longer keep ahead of the formation of new asperity contacts. Increasing surface roughness and decreasing oxygen content of the lubricant both cause a reduction in load carrying capacity. Depending upon the value of the speed of sliding, collapse of the EHD film either leads to “incipient scuffing” or to severe wear (scoring). This effect is probably associated with a metallurgical transformation in the steel at a particular value of the conjunction temperature.