Interaction between liquid aluminium and non-oxide ceramics (AlN, Si3N4, SiC)

The sessile drop method (wettability) and the dipped finger method (corrosion) were used to determine the behaviour of three kinds of non-oxide ceramics (AlN, Si3N4, SiC) pure or not, in contact with liquid aluminium. During the wettability test, the evolution of the contact angle vs. time or temperature was similar for all the substrates, only the characterisation of the metal / ceramic interface, coupled with thermodynamic calculations, revealed that SIC is more reactive than AlN (intrinsic inertness) and Si3N4 (formation of a reactional protective superficial AlN layer). The differences were assessed by dipped finger corrosion tests. The nitrides were almost uncorroded while the silicon carbide substrates, the regions rich in free silicon behaved as preferential diffusion paths with the formation of solid solution (Al-Si) being observed. For contact time greater than or equal to 100 hours, the SiC matrix was also corroded.