Auger Compositional Analysis of Ball Bearing Steels Reacted with Tricresyl Phosphate

Abstract

The low-speed lifetime of steel ball bearings under boundary lubrication can be significantly extended by prior soaking in hot tricresyl phosphate (TCP). Auger electron spectroscopy (AES) and depth-profiling techniques were combined to monitor changes in the chemistry of 52100 bearing steel surfaces as a function of cleaning history and conditions of TCP exposure. Phosphorus was detected in the outer layer of all samples exposed to TCP; the length of TCP exposure beyond three days had minimal effect on the surface concentration of phosphorus but did increase its depth of penetration and alter its local chemical environment. When presoaked with conditions (15 days in TCP at 110°C) which lead to optimum bearing lifetimes (I), the steel developed a surface film comprising three distinct regions of different composition. The outermost region had 4–6 percent phosphorus where the phosphorus Auger signal shapes were consistent with those of a phosphorus-oxygen moiety. The innermost region resembled the oxide/metal interface of nonexposed 52100; between the two was a region in which the phosphorus concentration diminished to zero.