Microstructures analysis and performance research of graphite/nickel-based brazing coating

Graphite is playing an important role in motor industry. A moderate amount of active metals were added into nickel-based solder, an innovative coating method was used to prepare the brazing layer on the surface of graphite, which realized the firmer connection between graphite and copper rotor in the motor commutators, and reduced the abrasion loss of the graphite brush which directly contact with copper originally. By using the DSC, XRF, SEM, EDS, XRD, ultrasonic C-inspection and resistance test,the performances of the brazing layer were analyzed. It is shown that not only the solder itself generated the intermetallic compounds, but also Si and Cr in the solder reacted with graphite turned into carbide, which made a strong metallurgical bond between graphite and solder, which does not affect its electrical conductivity as the brush after brazing.