Effect of low-temperature gaseous carburization on mechanical and tribological properties of CoCrFeMnNi high-entropy alloy

This study investigated the effect of low-temperature gas carburization (LTGC) on CoCrFeMnNi high-entropy alloy (HEA), focusing on the associated microstructural evolution, as well as the resulting changes in mechanical and tribological properties. The findings demonstrate that LTGC is an effective surface strengthening treatment for CoCrFeMnNi HEA. After LTGC, a ∼32 μm thick carburized case forms on the alloy surface, characterized by high hardness (∼12.8 GPa) and high compressive residual stress (∼2.5 GPa). This case consists of an expanded FCC phase, which is a carbide-free, supersaturated interstitial solid solution of carbon atoms in the FCC lattice. LTGC exerts limited influence on the macroscopic tensile properties of CoCrFeMnNi HEA, it leads to a modest increase in ultimate tensile strength, with slight reductions in yield strength and elongation. While, LTGC can significantly improves the tribological performance, reducing the volumetric wear rate from 11.4 × 10 −4 to 0.45 × 10 −4 mm 3 /Nm and decreasing the coefficient of friction from 0.51 to 0.49. Additionally, the wear mechanism transitions from a combination of abrasive, adhesive, oxidative, and fatigue wear to a mixed wear mechanism primarily governed by abrasion and oxidation after LTGC. • LTGC is an effective surface strengthening treatment for CoCrFeMnNi HEA. • LTGC generates a hard, carbide-free surface case with high compressive residual stress on HEA. • LTGC markedly enhances the tribological performance of HEA by altering its dominant wear mechanism.