Microstructural evolution and surface integrity Enhancement of SLM fabricated FeCoCrNiMn High-Entropy alloys by Single-Point diamond turning technology

Selective laser melted (SLM) FeCoCrNiMn high-entropy alloys exhibit inadequate surface quality and microstructural features unfavorable for machining, which limit their functional performance. This study comprehensively investigates the surface integrity, microstructural change and mechanical properties of FeCoCrNiMn high-entropy alloy fabricated by selective laser melting (SLM) with machined by single point diamond turning (SPDT). Results show that shallower cutting depths and higher cutting speeds significantly improve surface uniformity and finish, while promoting the formation of nano-laminated, grain-refined layers. SPDT transforms coarse columnar grains into nanocrystalline structures with an increased density of twins, stacking faults, and dislocations, resulting in up to a 16.9% increase in surface nano-hardness and wear resistance, and a reduction in friction coefficient to 0.226. Furthermore, adhesive wear is identified as the primary diamond tool wear mechanism in SPDT of high entropy alloys, which can be effectively mitigated by optimizing key machining parameters. These findings demonstrate that SPDT is an effective approach for enhancing both surface quality and mechanical performance of SLM-fabricated high-entropy alloys, and provide insights into the interplay between machining conditions, microstructural changes, and functional performance.