Chemical corrosion of liquid-phase sintered SiC in NaOH aqueous solution

Corrosion behaviour of the liquid-phase sintered SiC ceramics (LPS-SiC) was studied through exploration of weight loss, strength reduction and morphology evolution of the SiC specimens etched in the room-temperature/70°C 6.12 mol/L (20 wt-%) NaOH aqueous solutions. As a comparison, corrosion of the reaction-bonded SiC ceramics (RB-SiC) was also investigated. The results show that corrosions of the SiC specimens mainly contain homogeneous dissolution of the secondary-phase oxides in the LPS-SiC and that of Si in the RB-SiC, and peel-off of the SiC particles, resulting in increase of the surface roughness, weight loss and strength reduction of the SiC ceramics. As dipped in the 70°C NaOH solution, corrosion pores and channels form in the sublayer, leading to rapid increase of weight loss and strength reduction of the LPS-SiC. No matter in the room-temperature or 70°C NaOH solution, the LPS-SiC always has a higher corrosion resistance than the RB-SiC.