Effect of Silicon-Vanadium co-Doping on Corrosion Resistance and Tribological Behaviour of Spark Plasma Sintered CoCrMn Medium-Entropy Alloys

<title>Abstract</title> <p> The aerospace industry continuously experiences turbine blade failures due to the harsh operational conditions they are subjected to. It is thus paramount that more research be conducted to develop novel materials with stronger tribological performance. This study investigates the microstructural evolution and tribological behaviour of spark plasma sintered (SPS) CoCrMn medium-entropy alloys (MEAs). The fabricated CoCrMn (MEA) was co-doped synergistically with silicon (Si) and Vanadium (V). The three compositions were measured to be as follows: MEA-1.5Si-3.75V, 2.5Si-2.5V, and 3.75Si-1.25V (at%). The study of the microstructure of the fabricated MEA using Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDX) shows that there is a dendritic solidification structure. The Si is shown to segregate to the interdendritic areas, while V remains in the solid solution, thus acting as a stabilizer. Furthermore, the MEA-2.5Si-2.5V exhibited a higher microhardness of 510.84 HV compared with 389.7 HV for the base alloy, representing an increase in hardness of approximately 31%. These MEAs also exhibit the highest densification (about 99.68%) and the lowest wear volume (about 58.44%), indicating reduced wear loss compared to the baseline MEA. The electrochemical analysis of the 0.5M H ₂ SO ₄ and 0.5M HCl showed that MEA 2.5Si-2.5V achieved the better corrosion potential of Ecorr = -0.34V in H ₂ SO ₄ and − 0.38V in HCl. The corrosion current density was also the lowest at jcorr = 2.0 µA/cm² in H₂SO₄ and 2.8 µA/cm ² in HCl. Furthermore, the highest polarization resistance was found to be 13 kΩ·cm ² in H ₂ SO ₄ and 9.29 kΩ·cm² in HCl. The synergistic effect of the co-dopants Si and V was found to promote the formation of a passive film (Cr ₂ O ₃ -SiO ₂ -V ₂ O ₅ ) and an oxidative layer, thereby enhancing both the corrosion and wear resistance of the alloy. This study affirms that co-doping of base alloys with Si and V significantly improves the mechanical and chemical performance of MEA-CoCrMn. </p>