Effect of molecular structure of synthetic oils on decomposition and hydrogen generation in rolling contact

Hiroyoshi Tanaka ^1,2, Syun Honda ³, Joichi Sugimura ^1,2

¹ International Institute for Carbon-Neutral Energy Research, ² Research Center for Hydrogen Industrial Use and Storage,

 ³ Department of Mechanical Engineering,

Kyushu University, Fukuoka, Japan

ABSTRACT: Hydrogen embrittlement of steel reduces the service life of rolling bearings. Source of hydrogen is often decomposed oil or dissolved water in oil. In this study, several different types of synthetic oils are selected to see the effects of molecular structure of oils on hydrogen permeation.  Decomposition of oil is evaluated by hydrogen generation rate in a specially designed chamber. Hydrogen permeation rate in rolling contact is also measured by thermal desorption spectrometry. Hydrogen generation depends strongly on molecular structure of the oils. However, it is difficult to find a simple relationship between the hydrogen generation and the hydrogen permeation. Oil decomposes to hydrogen and carbon compounds which deposits on the contact surface. The deposited film may influence the permeability of hydrogen on the contact surface. The entire processes from generation to permeation of hydrogen is discussed.