Wetting and spreading of Ni-56Si alloy on SiC ceramic

The wetting and spreading of Ni-56Si alloy on SiC ceramic were performed under different temperatures and atmospheres by the sessile drop technique. The microstructure and phase compositions of solidified sessile drop/SiC substrate interface and drop surface were analyzed by scanning electron microscopy and energy dispersive spectroscopy. The results show that good wettability can be obtained in the Ni-56Si/SiC system at 1350°C under a high vacuum, static or flowing atmosphere of Ar + 5% in volume H2 atmospheres, respectively, and the fastest spreading equilibrium can be achieved under vacuum. The wettability at 1350°C is clearly better than those at 1100 and 1200°C in vacuum. The spreading process at 1100°C is different from those at 1200 and 1350°C in vacuum, and two different spreading mechanisms are present at the three different temperatures, which can be attributed to the kinetics of removing the wetting barriers (SiO2 layer) on SiC surface. The non-reactive wetting characteristics are further confirmed by the interface microstructure in this Ni-Si/SiC system.