Improved microstructure and bonding strength via MIG arc brazing in Sn-based Babbitt layer for bearing fabrication

A SnSb12Cu6 Babbitt layer was prepared for bearing applications by both metal inert-gas (MIG) arc brazing and centrifugal casting methods. The microstructure and interface bonding strength were investigated systematically. The results showed that fine microstructure without segregation was observed for the MIG method where a large number of diamond-shaped SnSb phases and dendrite Cu6Sn5 phases embedded in α-Sn matrix. In contrast, severe microstructure segregations with three distinct regions were observed in the Babbitt layer prepared by centrifugal casting method. The average interface bonding strength between the Babbitt layer and carbon steel of the MIG arc brazed samples was about 79 MPa, being two times larger than that of the centrifugal casting samples. The fracture mechanisms were discussed in terms of the fractural mechanics theory, and the refining microstructure was found to be primarily responsible for enhanced bonding strength. These findings provided a novel strategy for developing high quality Babbitt bearings with homogeneous microstructure and with high bonding strength.