An Investigation of the Effects of Oxygen and Water Vapor on the Compressive Film Strength of Boundary Films on Iron Substrates

摘要

The objectives of this program are to determine the effects of water and oxygen on the compressive strength of boundary lubricant films and to correlate these effects with the fundamental physical and chemical phenomena responsible for the formation and stabilization of the films and the inverse phenomena of degradation and dissolution. Compressive film strengths were measured under controlled atmospheres by means of a unique film penetration apparatus developed at Battelle. All experiments were performed on films formed from the diester di-2-ethylhexyl sebacate containing various amounts of tricresyl phosphate. It was found that water is detrimental to the formation of good boundary films and that oxygen is necessary for the formation of good boundary films. Scanning electron microscopy showed that nonmetallic inclusions on ARMCO iron surfaces play an important role in initiating the formation of strong boundary films. Experiments with inclusion-free zone refined iron verified this result. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were also used to study the surface chemistry of the films. These techniques seem to indicate that the residual films are almost exclusively inorganic phosphates. (Author)