Study on SiC Coating on Waterside of Zirconium Alloy Cladding

The pyrolysis characteristics of polycarbosilane (PCS) powder at high temperature and the chemical reaction mechanism between PCS powder and zirconium powder were studied, and SiC coating was prepared at 900 ℃. It is found that the pyrolysis products of PCS change from amorphous SiC to crystalline state at the beginning of 900 ℃. At different temperatures, a series of chemical reactions take place between the mixture of PCS powder and zirconium powder. The products are ZrC, Zr₂Si and Si₃Zr₅. By adjusting the reaction temperature, the extent of chemical reaction can be controlled and the composition of the coating can be adjusted. SiC coating was prepared on zirconium cladding surface by precursor infiltration pyrolysis (PIP). The SiC ceramic layer is obtained by dipping in PCS solution and pyrolytic cracking at 900 ℃ for three cycles and its thickness is 4 μm. The composition of the coating is SiC and ZrC is the transition layer. Scratch method was used to test the adhesion of the coatings, and the adhesion grade is 1-2.