Diffusion barrier effect of Al2O3 2 O 3 layer at the interface between Mo-Si-B coating and Nb-Si based alloy

An oxidation-resistant composite coating, including Mo-Si-B layer and Al2O3 2 O 3 diffusion barrier, was prepared on Nb-Si-based alloy by a two-step method. The Al2O3 2 O 3 film was fabricated by firstly deposition of Al on the alloy through pack cementation, and then by in situ oxidation of the aluminide coating. Mo-Si-B coating was then prepared on the Al2O3 2 O 3 film by spark plasma sintering. The Mo-Si-B coating is mainly composed of MoSi2 2 and a small amount of MoB and SiO2 2 particles. After long-term exposure at 1250 degrees C, the growth of the interdiffusion zone (IDZ) was suppressed effectively at the interface with the Al2O3 2 O 3 diffusion barrier. The results indicate that the diffusion barrier can significantly inhibit the outward diffusion of Nb, Ti and Cr alloying elements as well as the sluggish inward consumption of Si element. The Mo-Si-B coating with Al2O3 2 O 3 diffusion barrier exhibited a good oxidation resistance with a mass gain of about 0.97 mg/cm2 2 after 500 h of oxidation. (c) 2022 The Author(s). Published by Elsevier B.V. on behalf of Institute of Metal Research, Chinese Academy of Sciences. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )