Effects of PTFE activation and carbon sources on combustion synthesis of Cr2AlC/Al2O3 composites

Abstract Formation of Cr 2 AlC/Al 2 O 3 in situ composites was investigated by self-propagating high-temperature synthesis (SHS) involving both PTFE activation and aluminothermic reduction. In addition to Al and Cr 2 O 3 as the starting materials, carbon black, graphite, and Al 4 C 3 were used as the carbon sources. PTFE was employed not only as a reaction promoter, but also as a carburizing agent. Depending on different sources of carbon, the threshold amounts of PTFE for inducing self-sustaining combustion were 1.5, 4.0, and 3.0 wt% for the samples adopting carbon black, graphite, and Al 4 C 3 , respectively. The combustion front velocity and temperature increased with increasing PTFE content. Moreover, the sample using carbon black was the most exothermic, while the Al 4 C 3 -based sample was the least. For the powder compacts adopting carbon black or graphite, Cr 2 AlC/Al 2 O 3 composites were produced with no impurities. Due to relatively weak reaction exothermicity, however, the synthesized composites containing small amounts of Cr 7 C 3 and Al 4 C 3 were obtained from the Al 4 C 3 -based reaction scheme.