Boron capture stabilizing the diffusion barriers in a two-step Mo-Si-B coated refractory multi-principal element alloy

• Published in: Corrosion science 2023-08, Vol.221 (C), p.111365, Article 111365
• Main Authors: Su, Ranran, Zhang, Hongliang, Liu, Longfei, Perepezko, John H.
• Format: Article
• Language: English
• Subjects: Coating; Diffusion barrier; High-temperature oxidation; Refractory alloys; RMPEA
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2023.111365

A Mo-Si-B based coating has been applied on a refractory multi-principal element alloy (RMPEA) using a two-step coating strategy and has endured more than 750 h of thermal cycling oxidation exposure between room temperature to 1300 °C with a minimal weight change. The formation of the Mo5SiB2 diffusion barrier in the coating prevents the inward diffusion of the coating components. Then, boron is captured by the RMPEA, resulting in the formation of a solid solution X5SiB2 (X = W, Mo, Ta, Nb, V) layer and an RMPEA-B boride layer underneath it that acts as the second diffusion barrier. •A Mo-Si-B based coating was deverloped for a WMoTaNbV alloy by using a two-step coating strategy.•The diffusion pathway was modified by Mo and Si-B surface enrichment, resulting in a sequenced multilayered structure.•Boron is captured by the RMPEA substrate at the interface, enabling the formation of the second diffusion barrier.•The coating protects the WMoTaNbV from thermal cyclic oxidation for 750 × 1 h exposures at a 1300 °C.