Influence of lubricating oil additives on the pitting fatigue life of radial needle bearing

Toshihiko Ichihashi*, Masato Yokomizo, Susumu Matsumoto

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


Gear oils and automatic transmission fluids (ATFs) for passenger cars are required to have lower viscosity in order to achieve better fuel economy. In general, when the viscosity of lubricant is reduced, the pitting life of the bearing shows the tendency to decrease. In this study, to examine the influence of lubricating oil additives on the pitting life, the radial needle bearing pitting test machine that assumed the needle bearing in the planetary sun gear was produced. Three kinds of anti-wear additive were selected, and the individual effect of each additive and the combined effect of two kinds of additives were evaluated by the pitting test machine. The chemical composition of the additive film formed on the rolling contact surface was analyzed by X-ray photoelectron spectroscopy (XPS), and the hardness of the film was measured by using nano-indenter. It was understood that the combination of phosphorus and sulfur additive gives the longest pitting life of all tested samples, and that the additive which forms a softer film on the rolling surface tends to extend the pitting life.

Original languageEnglish
Pages (from-to)412-418
Number of pages7
JournalToraibarojisuto/Journal of Japanese Society of Tribologists
Issue number6
Publication statusPublished - 2009


  • Additives
  • Automatic transmission fluid
  • Gear lubricants
  • Nanoindenter
  • Pitting test
  • Radial needle bearing
  • Tribofilm

ASJC Scopus subject areas

  • Mechanical Engineering
  • Mechanics of Materials
  • Materials Chemistry
  • Surfaces, Coatings and Films
  • Surfaces and Interfaces


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