Hydrogen Generation from Lubricant under Rolling-Sliding Contact

Rolling element bearings in a particular application experience premature failure accompanied with white structure in steel. A possible cause of the failure is diffused hydrogen in steel which is generated by the decomposition of lubricant. This paper studied hydrogen generation from lubricant under rolling-sliding contact. A two-roller test was conducted in a sealed chamber, where the sliding speed and the lubricant temperature were controlled. The material of the roller was bearing steel and ceramic. Hydrogen gas concentration in the chamber was measured with a gas chromatograph. It was found that the hydrogen generation due to rolling-sliding contact depended on the lubricating conditions when the bearing steel specimens were used. The hydrogen generation increased by increasing the sliding speed and the oil temperature and decreasing the oil film parameter. Moreover, hydrogen generation was hardly observed under pure rolling condition. Another finding was that when ceramic specimens were used, the hydrogen generation was much smaller than when bearing steel specimens were used. These results suggest that nascent steel surface caused by the combination of metal-tometal contact and slip accelerates the lubricant decomposition to generate hydrogen.