Abstract
Alloying with V and Ti elements effectively improves the strength of WMoTaNb refractory high entropy alloys (RHEAs) at elevated temperatures. However, their effects on the oxidation resistance of WMoTaNb RHEAs are unknown, which is vitally important to their application at high temperatures. In this work, the effect of V and Ti on the oxidation behavior of WMoTaNb RHEA at 1000 °C was investigated using a thermogravimetric system, X-ray diffraction and scanning electron microscopy. The oxidation of all alloys was found to obey a power law passivating oxidation at the early stage. The addition of V aggravates the volatility of V2O5, MoO3 and WO3, and leads to disastrous internal oxidation. The addition of Ti reduces the mass gain in forming the full coverage of passivating scale and prolongs the passivation duration of alloys.
Highlights
Refractory high entropy alloys (RHEAs) were reported to possess excellent mechanical properties at elevated temperatures and high thermal stability, making them extremely promising high-temperature structural materials [1,2,3]
It is known that RHEAs, especially WMoTaNb alloys, suffer from poor oxidation resistance at elevated temperatures, which may be attributable to the evaporation of volatile oxides (MoO3, WO3 and V2 O5 )
The SEM/EDS results and oxidation kinetic indicate that WMoTaNb RHEA had the best oxidation resistance
Summary
Refractory high entropy alloys (RHEAs) were reported to possess excellent mechanical properties at elevated temperatures and high thermal stability, making them extremely promising high-temperature structural materials [1,2,3]. In reported RHEAs, WMoTaNb is famous for retaining high strength above 400 MPa at temperatures up to 1600 ◦ C and has a great potential for high temperature applications; its compressive plastic strain at room temperature (RT) is inferior at 3%, severely limiting its processing formation performance [4]. It is reported that alloying with V effectively improves the strength of WMoTaNb alloys to approximately 200 MPa at elevated temperatures of 600 ◦ C–1200 ◦ C [4]. The investigation of WMoTaNb alloys has been focused on their structure and mechanical properties; the oxidation behaviors of these alloys at elevated temperatures determine the application and have rarely been studied [9,10]. It is known that RHEAs, especially WMoTaNb alloys, suffer from poor oxidation resistance at elevated temperatures, which may be attributable to the evaporation of volatile oxides (MoO3 , WO3 and V2 O5 )
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