Soft magnetic composites produced by additive manufacturing

Abstract

The development of better performing electrical machines implies in the improvement of soft magnetic materials with lower losses due to hysteresis and eddy currents. Electric steels (Fe-Si) have long been used as ferromagnetic material in electrical machine cores. Despite being of low cost, Fe-Si steels with Si content up to 3.2% in weight have low electrical resistivity, which generates large losses due to eddy currents. With an increase in the Si content, the electrical resistivity and magnetic properties are improved, but on the other hand, the material becomes brittle, which in turn makes the manufacturing process more complex. To increase resistance to eddy currents, the core is formed by thin sheets of Fe-Si steel and with an insulating layer between successive laminations. This geometric configuration is reproducible by additive manufacturing, which creates almost totally dense metallic components, layer by layer, directly from computer-aided design data. This project aims to manufacture and study the metallurgical, mechanical, and magnetic characteristics of soft magnetic composites with alternating layers of Fe-Si steel (Fe-6.9Si) and a material with higher electrical resistivity (intermetallics, ceramic metals, or silica glass) by additive manufacturing. The composites are expected to have a low eddy current loss due to layers of soft magnetic material developed based on Fe-Si steel and layers of a material with higher resistivity such as an intermetallic material. The objective is to explore combinations producing composites with better magnetic performance in terms of eddy current losses and, therefore, lower energy consumption in electrical machines. The metallic powders, produced by gas atomization, will be characterized and used in the selective laser melting process. After producing distinct composites, these will be characterized by different techniques. The magnetic and mechanical properties will be evaluated as a function of chemical composition, microstructure, and additive manufacturing process parameters. (AU)