Enhanced oxidation resistance of (Mo95W5)85Ta10 (TiZr)5 refractory multi-principal element alloy up to 1300°C

Refractory-metal-based alloys are a potential replacement of current nickel-based superalloys due to their excellent mechanical strength at extremely high temperatures. However, severe oxidation in a high-temperature working environment limits their application. To address this challenge, a two-step coating process (including a Mo precoat and a Si-B pack cementation) was applied to an innovative refractory multi-principal element alloy (RMPEA) (Mo95W5)(85)Ta-10 (TiZr)(5). The coating is composed of an aluminoborosilica glass layer on top of a RMPEA-Si-B multilayered structure. The coating effectively protects the RMPEA from oxidation in high-temperature environments, as demonstrated by phase-stable operation at 10-20% higher temperatures over state-of-the-art systems without any forced-cooling system. Following an isothermal exposure at 1300 degrees C, the weight change of the coated sample follows a paralinear kinetics with a minor weight loss of 4.2 mg/cm(2) after 50 h. Thermal cycling tests between 1300 degrees C and room temperature in air resulted in the total weight gain of only 2.6 mg/cm(2) after 450 cycles. The coating shows an excellent adherence to the substrate with a boride layer acting as a barrier that maintains the coating integrity. This two-step Mo-Si-B coating method can be adapted to provide environmental resistance to a wide range of RMPEA. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study explores a two-step coating process for an innovative refractory multi-principal element alloy, demonstrating enhanced oxidation resistance at high temperatures and stable operation at 10-20% higher temperatures without forced cooling. The coating, consisting of an aluminoborosilica glass layer and RMPEA-Si-B multilayered structure, effectively protects the substrate and maintains coating integrity through borides acting as a barrier layer.