Failure analysis of double-row tapered roller bearing outer ring used in Coal Wagon Wheelset.

• The premature failure of an outer ring of double row tapered roller bearing for railroad car carrying coal is studied. • The studies of the outer ring fracture for the bearing type are considered rare. • The fatigue while the bearing is employed in a railroad car carrying coal is the root cause. • The high temperature at one of the raceways is also one the trigger causing crack. Fatigue fracture took place on a double-row tapered roller bearing outer rings applied in coal loaded train. The fracture is started from one side of the outer ring representing the possible overload condition of the axial or thrust force. The metallurgical investigation includes the hardness test, visual observation, microstructure investigation, and composition. Detailed metallurgical analysis discovered that the defects mainly occurred on the outer ring: (1) the color-changing phenomena might be occurred because of the temperature increase caused by the continuous friction load on the one side of the outer ring raceway, (2) The thermal softening resulting from the continuous load causing decrease in hardness as well as the decrease of the tensile stress. The crack origin is from one side of the bearing and propagate to another side. The thermal softening resulting from possibly continuous applied fatigue and a sudden impact is probably the leading responsible cause of the initial crack. The thermal softening occurrence consequently leads to a decrease in the surface hardness producing low tensile strength. Then, the sudden impact with considerable high force or acceleration caused by the track topology or other factors can cause the initial crack followed by the fracture of the outer ring. In sum, the failure of the bearing is investigated, and the original crack probably occurs because of the high temperature and the axial force overload. [ABSTRACT FROM AUTHOR]