Mechanism of failure of working faces of big bearings in the process of operation

The article presents the results of analyzing the mechanism of failure of working faces of big  roller bearings made of 0,2C2Cr4Ni (E3316 AISI) structural steel. The microstructure was investigated with the help of a METAM LV-31 metallographic microscope. The surface of the bearing rings and rollers was tested for various kinds of defects using a TESCAN Vega SB scanning microscope. The PMT-3 micro-hardness tester was used to measure micro-hardness. Studies show that the microstructure of steel is a fine-needled tempered martensite with chromium carbide inclusions observed near the surface. The depth of the cementation zone was determined on the basis of the measurement results. The value of the depth exceeds the standard established by the manufacturer. The destruction of the bearing roller assembly is characterized by spalling, stratification and cratering. The destruction of the bearing ring is characterized by scouring and indentation caused by metal particles caught up in the ring-roller contact in the process of operation. These defects result in the formation of micro-cracks and, as a result, further spalling and peeling. It is possible to prevent the defects by reducing the depth of the carbonization zone, as well as reducing the surface maximum hardness by changing the mode of final heat treatment.