Improving the Oxidation Behavior of CoCrFe₂Ni_0.5 High Entropy Alloy Through Powder-Pack Boriding

The oxidation performance of CoCrFe₂Ni_0.5 HEA borided through a powder-pack boriding process was investigated at 900 °C for 120 h. The boriding process at 900 °C for 6 h resulted in the formation of a two-zone structure: the outmost part contained a Ni₂Si layer and the inner part consisted of a MB/M₂B layer. The borided alloy displayed better oxidation resistance with the least oxidation rate constant value of 0.0383 (mgⁿ cm⁻²ⁿ h⁻¹). Moreover, this alloy rendered a continuous oxide layer that was denser, more compact, and contained fewer defects, which confirmed the improvement in oxidation resistance. The Ni₂Si layer plus the boride layer was responsible for the enhanced oxidation performance of borided alloy.