Reversal of Water Corrosion Behavior of Crystalline and Amorphous SiC with Increasing Temperature.

Abstract

The application of silicon carbide ceramic matrix composite (CMC-SiC) as hot-end components in next-generation advanced gas turbine is susceptible to corrosion by high-temperature, high-velocity water vapor present in combustion environments. Furthermore, its amorphous-crystalline composite structure results in a more complex corrosion response under water vapor exposure. Reactive molecular dynamics simulations were employed to investigate the differences in water corrosion behavior between crystalline and amorphous SiC over a temperature range of 1000-2000 K. At 1000 K, the amorphous SiC surface exhibits greater susceptibility due to its disordered atomic structure. In contrast, at 2000 K, the Si surface of 4H-SiC undergoes more severe corrosion. This reversal in corrosion behavior can be attributed to the formation and subsequent volatilization of the Si-O-Si network from the SiC slab. Specifically, the Si-O-Si network exhibits stronger bonding with the amorphous SiC surface, making it more resistant to corrosion by high-temperature water molecules. These findings offer valuable insights into the optimization of CMC-SiC hot-end components.