Corrosion Kinetics and Strength Degradation of Sintered δ‐Silicon Carbide in Potassium Sulfate Melts

Pressureless sintered α‐SiC ceramics containing carbon and boron as sintering aids and hot‐pressed SiC containing aluminum nitride as a sintering aid were corroded in K₂SO₄ melts at 1080° to 1150°C. SiC ceramics were oxidized and dissolved into K₂SO₄ melts. Since the corrosion of SiC ceramics in K₂SO₄ melts proceeded autocatalytically, a reaction product such as K₂S_1.44 was suspected to promote the corrosion reaction. The corrosion resistance of SiC containing AlN in K₂SO₄ melt was superior to that of SiC containing boron and carbon. Apparent activation energies for the corrosion of SiC ceramics were 309 to 331 kJ mol^‐1. The fracture strength of the specimens corroded by K₂SO₄ melt degraded to 40% to 70% of the original values up to a 20% weight loss and then was almost constant up to 45% weight loss.