Non-monotonic strength evolution of porous recrystallized SiC after high-temperature steam oxidation: Competition between neck strengthening and crack-damage accumulation

Porous recrystallized silicon carbide (RSiC) is a promising structural ceramic for heat exchange and hydrogen metallurgy, but long-term steam exposure impairs its oxidation behavior and mechanical reliability. In this work, porous RSiC fabricated from α-SiC powders was oxidized in steam at 1100–1300 °C. The oxide-scale thickness followed a parabolic law with an apparent activation energy of 151 kJ/mol. Steam oxidation reduced porosity and skeleton thickness, while normalized neck size and crack density increased with time. Flexural strength showed non-monotonic evolution. A S - N - D model integrating skeleton support, neck strengthening and crack damage was developed, which can reproduce the strength evolution with high R ². Fitted parameters showed neck strengthening efficiency drops with temperature, while crack damage shifts from abrupt to gradual accumulation. Overall, RSiC strength evolution in steam is governed by competition between early neck strengthening and long-term skeleton degradation and crack damage.