High performance Si-SiC composite coating for C/C composites prepared by a two-step pack cementation process

The synthesis of high performance Si-SiC composite coatings using two-step pack cementation process, was investigated. Bulk 2D-C/C composites specimens were hand-polished using 500 grit SiC paper, then distilled with water and dried at 353 K. Pack composition comprising of 65-75 wt% Si, 10-20 wt% graphite, 5-9 wt% MgO, and 5-9 wt% Al₂ were used for first step of pack cementation. The pack mixture was mixed in a ball mill and crucible was placed into an electronic furnace to heat at 1873K in an argon atmosphere. Coated C/C composites were heated at 1773K in air in an electrical furnace to analyze the isothermal thermal cycling oxidation behavior. It was observed that β-SiC and Si phase was generated after the first pack cementation process and microcracks were generated during quick cooling in the isothermal oxidation test. Result shows that dense Si-SiC composite coating with a thickness of around 300 μm can be prepared by the two-step pack cementation process.