Tribological Performance of Soft Magnetic Composite Materials for Gas Turbine Applications

Soft magnetic composites (SMCs) have gained attention in the last years of their usage in more compact and powerful electromechanical systems. These materials are used to combine the application of metallic material to the capability of generating (without external supply) a magnetic field. Automotive and aerospace technologies push the applications of these original materials to even higher power and mechanical stress to reduce the number of components, the size, and, in turn, the weight of complex systems. Considering gas turbine application, SMCs were formerly developed for bearings, but in the last decades, the new era of gas turbine electrification (e.g., hybrid-electric fly) has determined the need for mechanical improvement of such materials. At the same time, the reliability of soft magnetic material has to be discovered to avoid failure and reduce the maintenance schedule. In this work, tribological behaviors of SMCs were investigated by standard wear tests. In particular, two different types of SMCs were prepared through the powder metallurgy technique. Tests were conducted by a tribometer using a ball-on-disk configuration in lubricated condition. The effect of oil temperature and applied load were investigated. In addition to the tribological tests, an extensive postmortem analysis was conducted on the worn surface to recognize the mechanisms responsible for the deterioration of the materials. The results showed the effects of the oil viscosity on the useful operating life of the SMCs. Removal mechanisms depend on the load conditions, and the proper selection of the oil characteristics and load was assessed.