Development of high carbon Fe-Al alloys for tribological applications

Vacuum arc melting and vacuum induction melting techniques were used to produce alloys of Fe-15 wt. % Al (Fe3Al-based) and Fe-25 wt. % Al (FeAl-based) with various carbon contents (0, 0.5, 1 and 2 wt. %). Hot working of the alloys was achieved via isothermal forging or hot extrusion. Carbon addition into Fe-15Al alloy led to a duplex microstructure containing Fe3AlC0.5 and Fe3Al, while formation of graphite was observed in the carbon-added Fe-25Al alloys. With increasing carbon content, the hardness increased significantly in Fe-15Al alloys but exhibited a slight decrease in Fe-25Al alloys. The ductility was evaluated using bending tests and was correlated with the fracture mode. Ball-on-disk sliding wear tests revealed that the coefficient of friction and wear rate were greatly reduced with carbon addition for both the Fe-15Al and the Fe-25Al alloys. The braking wear performance of carbon-added alloys was evaluated with an industry-approved dynamometer by using commercial brake pads, and was compared with that of cast iron, a currently used material for automobile brake rotors.