Improving Corrosion Resistance of Soft Magnetic Composites for Induction Heat Treating Applications

Soft magnetic composites (SMCs) are widely used in induction heat treating applications to increase system efficiency, improve heat pattern control, and prevent undesired heating of adjacent areas of the workpiece or machine components. In most induction heat treating applications, the expected lifetime of the inductor is limited by the fatigue life of the copper.

In some of the most severe cases, the lifetime of the inductor is limited by the lifetime of the magnetic flux controller. A typical failure mode of the magnetic flux controller in these applications is corrosion. Corrosion of the soft magnetic particles in the composite is caused by combination of elevated temperatures and exposure to oxidizing agents (quenchants, air, etc.). Coating SMCs can significantly enhance their corrosion resistance, improving durability of the SMCs.

In the present study, four commercially available SMCs, Ferrotron 559H, Fluxtrol 100, Fluxtrol 50, and Fluxtrol A, were coated with three different types of high performing ceramic polymer-based coating materials. ASTM D1735 humidity tests are performed for 48, 96, and 168 hours on all the samples. Results of the corrosion testing including a comparative analysis of three types of coatings will be presented and their potential impact on inductor lifetime will be discussed.