Coatings for SiC-SiC Compiste Hydrothermal Corrosion Protection

Structure of SiC/SiC composite (ORNL 2017)

Environmental barrier coatings for the next generation of accident tolerant fuel cladding

Silicon carbide/silicon carbide composites are a candidate for the next generation of accident-tolerant LWR fuel cladding. SiC has excellent stability at accident conditions compared to zirconium, making it an attractive option for safety enhancement. These materials combine SiC fibers in a SiC matrix with a pyrolytic carbon interlayer, providing improved mechanical properties to accommodate radiation-induced swelling.

However, SiC poses a few challenges before it can be implemented. One concern is the hydrothermal corrosion of SiC at normal LWR operating conditions. The corrosion of SiC in water can lead to gradual recession of the cladding tube and SiO2 build up in cool parts of the reactor. Water chemistry affects the corrosion rates of SiC depending on amounts of dissolved hydrogen and oxygen, which vary depending on the type of reactor. The weight loss of SiC in different water chemistries is shown below.

a) Corrosion equation of SiC in high temperature water b) Weight loss of monolithic SiC in various water chemistries (Terrani, JNM 2015)
Metallic PVD coating cross section on SiC for corrosion protection









In this project, we are studying various environmental barrier coatings and coating technologies to mitigate the corrosion of SiC in water. Candidates include both metallic and ceramic coatings produced with process such as PVD, cold spray, and thermal conversion. An initial study of different coating materials and technologies is underway.

Future Work

  • Further trials of various coating technologies
  • Advanced characterization of coating materials
  • PVD coating microstructure optimization
  • Preliminary static water autoclave tests
  • Water radiolysis-assisted hydrothermal corrosion tests
  • Mechanical testing of coatings on SiC tubes
  • Long-term coating corrosion tests in typical LWR water chemistries

Our collaborators on this project are Westinghouse Electric Company, General Atomics, and Argonne National Lab.