An oxidation resistant refractory high entropy alloy protected by CrTaO₄-based oxide

Area of Science:

• Materials Science
• High-Temperature Materials
• Oxidation Behavior

Background:

• Refractory high entropy alloys (RHEAs) show promise for high-temperature applications.
• Limited data exists on the long-term oxidation behavior and mechanisms of RHEAs.

Purpose of the Study:

• To investigate the isothermal oxidation behavior of a novel RHEA at 1000°C and 1100°C for an extended duration of 200 hours.
• To understand the oxidation mechanisms and oxide scale formation under prolonged high-temperature exposure.
• To evaluate the oxidation resistance of the RHEA compared to existing literature data.

Main Methods:

• Thermogravimetric analysis (TGA) was employed for isothermal oxidation testing.
• Oxidation was conducted at 1000°C and 1100°C for up to 200 hours.
• Analysis of the external oxide layer composition was performed.

Main Results:

• At 1000°C, exponential weight gain was observed due to the inability to form a dense CrTaO4-based oxide layer.
• At 1100°C, parabolic weight gain indicated the formation of a protective CrTaO4-based oxide scale with dispersed Al2O3 and Cr2O3.
• The RHEA exhibited a weight gain of 4.03 mg/cm² after 200 hours at 1100°C, demonstrating superior oxidation resistance.

Conclusions:

• The novel RHEA exhibits significant long-term oxidation resistance at 1100°C.
• The formation of a protective CrTaO4-based oxide layer is crucial for high-temperature oxidation resistance.
• Findings provide insights for developing RHEAs with enhanced durability for elevated temperature applications.