Water-oxygen corrosion behavior of SiC ceramic matrix with controlled Y distribution

Reactive melt infiltration enables the incorporation of rare-earth elements into SiC/SiC composites to form protective silicate layers under water–oxygen environments, but thermal expansion mismatch may degrade mechanical properties. To address this issue, a gradient design is proposed, enriching Y near the surface while maintaining a SiC-dominated interior. By exploiting the structural tunability of polymer precursors, Y is introduced prior to Si infiltration, ensuring controllable content and spatial distribution. Porous Y-C with either uniform or gradient Y distributions are fabricated via a soft-template method combined with hierarchical impregnation. After corrosion at 1300–1400 °C, SiC ceramics with uniformly distributed Y (1.26 wt%) forms dendritic Y₂Si₂O₇, providing moderate protection, whereas gradient Y (2.21 wt%) rapidly develops a dense and continuous surface silicate layer. This layer effectively suppresses SiO₂ volatilization and enhances corrosion resistance up to 1400 °C. The improved corrosion resistance arises from spatial Y regulation, enabling synergistic “rapid reaction–layer formation–long-term protection.”