Effect of Boron and Vanadium Co-Diffusion Temperature on the Friction and Wear Properties of Feconicrmn High-Entropy Alloys

Abstract

High-entropy alloys (HEAs), distinguished by their unique multicomponent equiatomic compositions and the high-entropy effect, demonstrate outstanding mechanical strength, thermal stability, and corrosion resistance. Among them, FeCoNiCrMn HEAs are particularly promising for use in extreme environments owing to their stable face-centered cubic (FCC) structure and excellent ductility. However, their relatively low surface hardness and limited wear resistance hinder their broader engineering applications. While single-element chemical heat treatments can improve surface properties, they often suffer from drawbacks such as phase inhomogeneity, poor adhesion, and increased brittleness. In this study, a boron–vanadium co-diffusion approach was employed to modify the surface of FeCoNiCrMn HEAs. The influence of co-diffusion parameters on the alloy’s friction and wear behavior was systematically investigated. The co-diffusion process resulted in the formation of a graded diffusion layer primarily composed of (Fe, Cr, Ni, Co, V)B. Vanadium facilitated the formation of VB, VB2, and VC phases at grain boundaries, while boron formed multicomponent borides with the matrix, effectively addressing the limitations associated with single-element boron diffusion. Under the optimized condition of 950 °C for 8 hours, the surface hardness reached 2518 ± 116 HV—approximately 603% higher than the substrate—with a diffusion layer thickness of 254.7 μm and a continuous hardness gradient. The wear mechanism shifted from mixed adhesive–abrasive wear to mild abrasive–oxidative wear, accompanied by a 63% reduction in the friction coefficient (down to 0.31), stabilizing within 5 minutes. This work offers a theoretical foundation for the development of multi-element co-diffusion surface treatments for HEAs and expands their application potential in wear-resistant environments.

Keywords: High-entropy alloys, Boron and vanadium co-diffusion, Friction and Wear, Graded diffusion layer