Microstructure and mechanical and tribological properties of high carbon Fe₃Al and FeAl intermetallic alloys

Fe-15 mass%Al (Fe₃Al-based) and Fe-25 mass%Al (FeAl-based) alloys with various carbon contents (0, 0.5, 1 and 2 mass%) were produced to study the effect of carbon addition on microstructure, mechanical properties and tribological properties of Fe-Al intermetallics. Carbon addition to the Fe-15Al alloy led to the formation of perovskite-type Fe₃AlC_0.5 carbides in the matrix, while carbon present in the form of graphite in the Fe-25Al alloy. The formation of Fe₃AlC_0.5 carbides resulted in a significant strengthening effect on Fe-15Al alloy, but the strengthening was accompanied by a great loss in ductility. In the Fe-25Al alloy, the strength and ductility were slightly reduced by the formation of graphite. The tribological properties were determined using ball-on-disk sliding wear test in the range of room temperature to 773 K. It was demonstrated that the carbon addition significantly improved the room temperature friction coefficient and wear rate of both Fe-15Al and Fe-25Al alloys, but it tended to decrease the wear rate of these alloys at elevated temperatures. The tribological properties were discussed in terms of microstructural features and mechanical properties.