Microstructure evolution, growth kinetics and formation mechanisms of silicon-rich NbSi2 coatings on Nb substrate

A Si-rich NbSi2 coating was prepared on Nb substrate by hot dip silicon plating process, which mainly consists of Nb5Si3 interfacial layer, NbSi2 intermediate layer and silicon-rich NbSi2 outer layer. The Si-rich NbSi2 coating has flat surface and dense structure, and the surface roughness is only 0.218-0.548 mm. Raising the deposition temperature can also significantly increase the growth rate of the Si-rich NbSi2 coating. The hot-dip silicon plating process has an extremely low reaction activation energy (249.99 kJ mol-1), which indicates that there are a large number of activated molecules during hot dip silicon plating. The silicon atoms in the molten bath deposited on the Nb surface and maintained a high chemical potential gradient continuously. Therefore, the solid diffusion reaction of Nb-Si was continuous, and the Nb5Si3 phase was generated and consumed continuously, and transformed into NbSi2 phase, which led to a higher growth rate of coating (1.7 x 10-13 to 4.3 x 10-13 m2 s).& COPY; 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).