Laser directed energy deposition of FeSi/SS 316L advanced bimetallic high-speed rotors: From material characterization to performance evaluation

Abstract

The demand for high-speed electric machinery has significantly increased, driving innovation in motor design. While permanent magnet rotors dominate due to their superior torque density and efficiency, their reliance on rare earth elements raises environmental and supply chain concerns. Synchronous Reluctance motors, which do not require permanent magnets, present a promising alternative, though their design limits rotor mechanical performance. Additive manufacturing, particularly Directed Energy Deposition (DED), addresses these challenges by enabling the production of multi-material structures.

This study investigates the potential of DED to fabricate high-speed rotors using FeSi_2.9, a soft magnetic alloy with high permeability, and the paramagnetic stainless steel AISI 316L. Single-material depositions were analyzed through microstructural and microhardness tests in both as-deposited and heat-treated conditions. Magnetic and mechanical characterization were performed on heat-treated samples. Annealing improved the magnetic properties of FeSi_2.9 without compromising the mechanical performance of AISI 316L. A bimetallic blank with alternating layers of the two materials was fabricated and characterized similarly. Subsequently, a rotor was extracted, machined, and tested.

Results demonstrated excellent printability, achieving crack-free deposits with >99 % relative densities. The fabricated SynRel rotor operated at speeds up to 100,000 rpm, underscoring the suitability of DED for producing advanced multi-material components for high-speed machinery.