Formation mechanism of molten salt-assisted HfC interlayer in C/SiC-HfC and its anti-corrosion behavior against HfSi₂

Reactive Melt Infiltration (RMI) is a promising technique for fabricating C/SiC-HfC composites. However, the molten HfSi₂ alloy reacts with the SiC matrix, pyrolytic carbon (PyC) interface and carbon fibers during the preparation process, causing fiber damage and finally decreasing the mechanical properties of the composites. In this work, with the aim of resisting HfSi₂ alloy corrosion, a dense HfC interlayer was successfully introduced into semi-dense C/SiC composite via the molten salt-assisted method. The influence of reaction temperature and time on the thickness and microstructure of the HfC interlayer was systematically investigated, and its formation mechanism was revealed. The HfC layer maintains structural stability after heat treatment at 1600 ℃, demonstrating outstanding thermal stability. The presence of the HfC interlayer effectively enhanced the average flexural strength to 201.41 MPa, representing a 103% improvement as compared to the C/SiC-HfC composite without the HfC interlayer, revealing that the HfC interlayer effectively resists HfSi₂ corrosion, serving as a barrier to protect the SiC matrix, PyC interface and carbon fibers.