Hydrogen embrittlement of a tapered roller bearing due to lubricant breakdown

This paper presents the results of an examination of a single row tapered roller bearing from a 650 t Face shovel swing transmission gearbox that exhibited an unusual pattern of axial fracture. The bearing sustained multiple axial fractures around the inner ring (cone) many of which exhibited a fracture face with a two tone pattern, suggesting a two stage fracture, comprising a dark internal region of lubricant discolouration and a bright fresh fracture border. SEM examination indicated the discoloured region to have fractured following an intergranular path consistent with hydrogen embrittlement arising from lubricant breakdown, while the border region exhibited a cleavage fracture.