## 4 Comparative Evaluation of Magnetic Gear Core Materials
### Powder Metallurgy  
Somaloy 700 HR 5P is specifically engineered for powder metallurgical production and provides significant advantages for mass manufacturing. It supports single-step pressing of net or near-net shapes with minimal material waste. Additionally, its isotropic magnetic behavior and high resistivity allow for 3D magnetic flux conduction without lamination, which is especially advantageous in complex coaxial or transverse magnetic topologies [88]. However, the initial investment in high-tonnage presses and precision holds is substantial, making this technique economically infeasible for prototyping or very low-volume production. In such cases, pre-machinable SMC blanks may be used with caveats on performance fidelity. M400-50A and Vacodur 50A are not commonly processed via powder metallurgy, primarily due to poor compactibility and the need for high-temperature sintering atmospheres. While Fe-Co alloy powders can be produced, their cost and sintering complexity limit their use to niche experimental setups [89]. Therefore, powder metallurgy is not considered viable for either prototyping or mass production with these two materials under standard industrial conditions. Following the detailed evaluations presented above, Table 4 provides a normalized manufacturability scoring of each core material across four major production methods and two production volume scenarios. M400-50A achieves the highest overall feasibility score (59/100) due to its balanced compatibility with machining, wire EDM, powder metallurgy, and casting. Somaloy 700 HR 5P performs exceptionally well in mass production powder metallurgy (90/100), but its poor suitability for prototyping lowers its average score to 22/100. Vacodur 50A, while feasible for prototyping via EDM or precision machining, demonstrates limited scalability and high processing difficulty, resulting in a moderate manufacturability score of 36/100. These findings clearly highlight the importance of aligning material selection not only with physical properties but also with the chosen manufacturing method and expected production volume in magnetic gear system design. The manufacturability of magnetic gear components is critically influenced by the selection of core materials, production methods, and intended production volumes. This review highlights that while traditional electrical steels like M400-50A offer balanced compatibility across multiple fabrication techniques, advanced materials such as Somaloy 700 HR 5P and Vacodur 50A present trade-offs between performance and manufacturability. Somaloy 700 HR 5P demonstrates excellent manufacturability in high-volume powder metallurgy applications, although its applicability in prototyping remains limited due to process-specific constraints. Vacodur 50A offers superior magnetic performance, but this comes at the expense of complex manufacturing requirements and high processing costs. These insights emphasize the need for early-stage manufacturability assessments in magnetic gear design, where material-process-volume alignment can significantly impact both the technical feasibility and the economic viability. Future advancements in additive manufacturing and hybrid processing may help mitigate current limitations, especially for materials with otherwise restricted formability. Figure 13 illustrates the comparative radar chart representations for each core material, where subfigures (a), (b), and (c), respectively, highlight the normalized performance profiles of M400-50A, Somaloy 700 HR 5P, and Vacodur 50A. The normalized data were compared using a radar chart to enable multidimensional performance evaluation of different materials. As illustrated in the radar chart, Vacodur 50A demonstrates high performance, particularly in saturation flux density (2.35 T), relative permeability (10,000), and electrical conductivity (2.38 \(\times\) 10\({}^{7}\) S/m). These parameters make Vacodur 50A especially suitable for applications requiring high magnetic density and rapid magnetic flux response.