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

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 Mo 5 SiB 2 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 X 5 SiB 2 (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. [ABSTRACT FROM AUTHOR]