FeSiCr–RIP/CIP Soft-Magnetic Composites: Microstructure (EBSD-KAM), Core Loss, and DC-Bias for Molded Inductors

Soft magnetic composites (SMCs) based on Fe–Si–Cr (FeSiCr) are attractive for molded power inductors but can suffer from elevated core loss at high frequency. This work systematically benchmarks FeSiCr blended with three insulated, fine iron powders—silica-coated reduced iron powder (RIP), silica-coated carbonyl iron powder (CIP), and phosphate-treated CIP (CIP-P)—across 10–50 wt% and against single-powder baselines. Toroids pressed at 200 MPa and cured at 150°C were characterized for permeability µ(f) (100 kHz–1 MHz), B–H loss at 50 mT, DC-bias retention (15 A on T-cores), corrosion (salt spray), and microstructure via EBSD kernel average misorientation (KAM). A clear structure–property linkage emerges: higher KAM and low-angle boundary (LAGB) fractions correlate with higher coercivity and hysteresis loss, providing a quantitative microstrain–core loss descriptor. Blending exhibits a pore-filling optimum. For CIP/CIP-P, this occurs at ~ 20–30 wt%, maximizing permeability and minimizing hysteresis. For RIP, the permeability optimum is at ~ 10 wt%, while the minimum for hysteresis loss and coercivity occurs at ~ 30 wt%. Eddy-current loss reductions are strongest with silica-coated CIP/RIP; the phosphate interface (CIP-P) gives less high-frequency benefit. Under 15 A DC bias, all additives improved inductance retention compared to the FeSiCr baseline. The blends ranked in the order of RIP ≈ CIP ≫ CIP-P > FeSiCr, with RIP and CIP performing similarly at low-to-moderate loadings. This improvement reflects the higher M _s of iron powders and the favorable EBSD metrics of RIP at low loading. Corrosion tolerance follows RIP ≈ CIP ≫ CIP-P, with mold-edge abrasion acting as the primary initiation site. Incorporating recycled RIP advances circular-economy goals while delivering best-in-class bias stability with competitive core loss when used near its pore-filling window.