Structural design and wear properties of TIG arc brazing tin-based babbit to mild steel

The tin-based babbit with different layer thickness was bonded to mild steel via TIG arc brazing. The microstructure, microhardness, wear properties and phase formation mechanism near the interface of the arc brazed layer were investigated by the optical microscope (OM), X-ray diffraction (XRD), high temperature friction and wear testing machine (HTFWT), laser scanning confocal microscope (LSCM), electron microscope (SEM) and energy dispersion spectrum (EDS). It can be found that in the arc brazing seam region, the thinner layer made it possible to form larger size SbSn monotectic phase that connected together and some Fe-Sn IMCs were formed near the interface. So that when the layer thickness was 0.5 mm, the microhardness of arc brazing tin-based babbit layer was the largest and the antifriction property was the best. Moreover, on the brazing tin-based babbit interface, Fe elements were transited and diffused from mild steel into the brazing seam region. Element concentration of Fe was high near the steel interface and formed concentration gradient in the liquid metal layer, which was helpful to promote the metallurgical reaction. Phase constituents of the brazed joint interface were Fe, Fe Sn, FeSn and FeSn , formed in the metallurgy of Fe from mild steel and the Sn from tin-based babbit.