Sealing role of B2O3 in MoSi2–CrSi2–Si/B-modified SiC coating for C/C composites

A MoSi2–CrSi2–Si/B-modified SiC coating was prepared by two-step pack cementation. The coating could protect C/C composites from oxidation at 1173 K for 600 min and at 1873 K for 300 h and from erosion at 1873 K for 50 h, respectively. B2O3 oxidised from B-modified SiC layer could seal cracks at intermediate temperatures, resulting in improving the oxidation resistance of the coating. Large cracks caused by the bending of the coated specimens and excessive local stress resulted in the fracture of the tested specimens.

► MoSi2–CrSi2–Si/B-modified SiC coating was prepared on the surface of C/C composites.
► The coating can protect C/C composites from oxidation for 600 min at 1173 K and 300 h at 1873 K.
► The coating can protect C/C composites from erosion at 1873 K for 50 h.