Diffusion barrier effect of Ta or TaSi2 layer at the MoSi2/Nb-based alloy interface

MoSi2 coatings with a Ta or TaSi2 diffusion barrier were prepared on C103 by HPS or HPS/HAPC/HPS. After oxidation at 1250 ℃ for 150 h, the growth rate of the diffusion layer in the MoSi2, MoSi2/Ta, and MoSi2/TaSi2 coating samples was 4.68, 1.93, and 7.36 µm2/h, respectively. Combination with oxidation test at 1550 °C showed Ta layer had the best diffusion resistance effect. The main reasons were that the diffusion energy barrier of Si in Ta was 0.257 eV, higher than that in Nb (0.023 eV) by First-principles calculation, and the multilayer structure after diffusion reduced the driving force of Si diffusion.