Review on the impact of processing routes and external factors on phase formation and tribological properties of CoCrFeMnNi HEAs

High-entropy alloys (HEAs) based on CoCrFeMnNi continue to attract attention to their balanced mechanical properties and corrosion resistance; however, their tribological response remains strongly path-dependent. This review combines processing routes such as casting, powder metallurgy/spark plasma sintering (SPS), additive manufacturing (SLM/LPBF), and coating methods such as PVD/thermal spray with the resultant phase constitution (FCC, BCC, σ, and Laves) and defect structures to describe their trends in hardness, friction, and wear at room temperature up to approximately 800 o C. To balance different literature reports, we standardize the units of wear and cluster complete test data (counterface, load, kinematics, atmosphere, and temperature) so that quantitative comparison between studies is possible. Determining (i) systematic decreases when the FCC changes to BCC or intermetallic-reinforced state and (ii) a crossover in temperature at which many coating types can minimize wear at approximately 400 o C before increasing in temperature, a causal map was constructed linking route-controlled phase selection and secondary reinforcers (e.g., carbides/solid lubricants) to effect sizes in selective wear and friction. A route-selection guide, important information gaps in tribocorrosion (sliding-electrochemistry coupling), and template reporting tools that improve design and reproducibility are included at the conclusion of the review. All these factors lead to a consistent foundation on which to build the engineering of Cantor based HEAs and coating to meet desired wear windows in commercial environments.