Soft Magnetic Alloys for High Temperature Radial Magnetic Bearings

Magnetic bearings are a prime technology that will lead the next generation of gas turbines into the 21st century. Before magnetic bearings can be utilized, fundamental properties of the soft magnetic materials used to fabricate these components must be known at the intended operating temperatures and stress levels found in gas turbine applications. This paper present result of recent work carried out on the development of a radial magnetic bearing for a high speed, high temperature gas turbine application. Mechanical and magnetic data on candidate soft magnetic materials intended for use in a radial magnetic bearing were characterized at both room and operating temperature (550C). The effect which long- term exposure to high temperature has on these properties was also tested. The effect of heat treatment schedule and atmosphere were examined as to their effect on both the magnetic and mechanical properties of the materials for the short and long term exposure to this extreme environment. The use of the material data accumulated was utilized for the development of the radial bearing is explained along with a proposed design of a radial magnetic bearing.