Surface-treated rolling bearing and manufacturing method thereof

Abstract

In a rolling bearing put under a working circumstance in which water tends to intrude into lubricants, it has been known such a phenomenon that hydrogen ions formed by decomposition of the lubricants are adsorbed to raceway surfaces and accumulated as hydrogen atoms in highly strained sites (in the vicinity of the position for maximum shearing stress), to cause stress corrosion cracking type peeling. The present invention provides a rolling bearing in which an oxide layer of an iron/chromium oxide series is formed at a thickness of from 1 to 1000 nm to at least one of raceway surfaces of bearing rings or rolling contact surfaces of rolling elements and a manufacturing method thereof. The oxide layer can inhibit hydrogen formed by decomposition of water incorporated in the lubricants from intruding into the matrix of the bearing members, thereby preventing early peeling for the raceway surfaces of the bearing rings or the rolling contact surfaces of the rolling elements and, thus, greatly improving the rolling life. The oxide layer can be formed simply by merely tempering the bearing member and then applying a re-heating treatment in air at a temperature lower than the tempering temperature.