Manufacturing Induced Hydrogen Embrittlement of 52100 Bearing Steel Outer Ring

Abstract

An axle roller bearing failed due to full width axial cracking of the outer ring, an uncommon occurrence in roller bearings. Typically, this mechanism of failure is more consistent with inner rings that have been installed with excessive hoop stress from an incorrect interference fit on a rotating shaft. Fractography of the axial fracture revealed a shallow intergranular crack initiating from the surface of an external corner. The remainder of fracture propagation was high-cycle fatigue. Detailed metallographic analysis revealed hydrogen embrittlement on all four corners of the ring. Final machining processes, such as grinding and polishing performed on the side faces, raceway and outer surface had removed the embrittled material in these areas. This indicated the embrittlement process was not service related, but rather a result of the manufacturing heat treatment, most likely performed following the first rough cut of the ring prior to finishing.