Assessment of the Potential Diffusion Barriers between Tungsten and Silicon Carbide for Nuclear Fusion Application

Abstract

A tungsten (W) material is a candidate for the first wall and silicon carbide (SiC) composites are candidates for the structural materials applied in nuclear fusion. SiC fiber-reinforced W composites are also developed for nuclear fusion applications. An effective diffusion barrier is required to prevent reaction between W and SiC. Therefore, in this work, advanced ceramics coatings, such as oxides (ZrO2, TiO2 and Er2O3), nitrides (ZrN and TiN), carbides (TiC and ZrC) were chosen to assess abilities to suppress the reactions. Various films were coated on a CVD (chemical vapor deposition)-SiC plate using the dipping method. Additionally, nitrides coatings prepared by the sputtering method were also investigated in this work. Then evaluations were carried out by joining the coated CVD-SiC plates with W foils. Only the multi-dipped Er2O3 coating and the sputtered nitrides worked well compared with the other coatings. For the other oxide coatings, reactions were identified between oxides and SiC, and for the dipped nitrides and carbides films, cracks were observed on the coating, generated from the coefficient of thermal expansion (CTE) mismatch with the SiC substrate and volume change for the oxides changing to nitrides and carbides. This work provides suggestions about choosing an appropriate interface material between SiC and W.