William P. Ogden

Rolling Contact Fatigue Life and Spall Propagation Characteristics of AISI M50, M50 NiL, and AISI 52100, Part III: Metallurgical Examination

This is the third part of a three-part series that investigates the rolling contact fatigue initiation and spall propagation characteristics of three bearing materials, namely, AISI 52100, VIM-VAR M50, and VIM-VAR M50 NiL steels. Though there is substantial prior work published on the rolling contact fatigue initiation of these materials, little is known about their spall propagation characteristics after spall initiation. In Part III, 208-size, 40-mm-bore bearings are examined for changes in appearance of the microstructure as well as residual stress as a function of depth in the circumferential direction. The correlations between the experimental results from Part I and computer modeling in Part II are made.

Corrosion Assessment and Characterization of Aerospace-Bearing Steels in Seawater and Ester-Based Lubricants

The corrosion behavior of bearing steels was screened using potentiodynamic scans in seawater. The results of electrochemical testing provided a relative ranking of the bearing steels when tested in aqueous chloride-containing solution. The corrosion behavior of bearing steels in the lubricant environment has been observed to be quite different than in aqueous solution. Both the amount of water contamination in oil and chloride content of the water impact the observed corrosion rates in oil-water mixtures. All steel compositions tested demonstrated localized corrosion damage when exposed to oil with water added; however, inherently less corrosion-resistant alloys had more widespread shallow attack, whereas higher Cr-containing alloys displayed more localized severe attack. The mechanism of corrosion in the two-phase, oil plus aqueous phase system appears to be controlled by an aqueous corrosion process dependent on steel microstructure and emulsified or free water and likely limited by oxygen availability...