Session: 18-07: Failure Prediction and Life Asssessment II

Submission Number: 178053

Tribological and Coating Degradation of Soft Magnetic Composites for High Temperature Applications 

Soft Magnetic Composites (SMCs) are essential materials for compact and high-power electromechanical systems, sine they enable the integration of high magnetic permeability with significantly higher electrical resistivity compared to conventional laminated steels. SMCs are typically Fe-based powder metallurgy materials embedded in an electrically insulating matrix, which drastically reduces their electrical conductivity. This feature minimises eddy current losses and enables efficient magnetic flux conduction in complex three-dimensional geometries. In the context of gas turbine applications, SMCs were initially developed for use in bearing assemblies. However, with the advent of gas turbine electrification, the demand for enhanced mechanical performance of these materials has grown considerably. At the same time, ensuring the structural reliability of soft magnetic materials has become crucial to prevent in-service failures and reduce the frequency of maintenance.

This study examines the wear resistance mechanisms of two SMC grades under lubricated sliding conditions, with a focus on high-temperature applications up to 100 °C. Tribological tests were performed using a ball-on-disc configuration, allowing for the acquisition of macro-scale data, including the coefficient of friction (CoF) and specific wear rate (SWR). These parameters were correlated with advanced post-mortem analyses of the wear tracks. X-ray diffraction (XRD) was employed to characterize the surface modifications induced by thermal and mechanical loading, while scanning electron microscopy (SEM) provided insight into the underlying wear mechanisms. XRD results revealed the occurrence of temperature-induced phase transformations and the crystallisation of specific iron oxide species on the surface exposed to high thermal stress. This indicates that elevated temperatures, combined with frictional effects, alter the surface microstructural stability of SMCs, although the bulk structure remains largely unaffected. The findings provide critical insights into the thermo-tribological behavior of SMCs, which are crucial for predicting service life and establishing operational safety thresholds in high-power electromechanical systems.

Presenting Author: Annalisa Fortini Department of Engineering – University of Ferrara

Presenting Author Biography: She is an Associate Professor in Metallurgy at the University of Ferrara.
Her research activity is focused on the microstructural and mechanical characterization of metallic alloys, with a particular emphasis on Shape Memory Alloys (SMAs), aluminium alloys and ferrous alloys. Other topics of interest include the analysis and prediction of tribological degradation phenomena in mechanical components.
Her research is published in numerous scientific articles, mainly in international peer-reviewed journals, as well as in national and international conference proceedings.

Authors:

Alessio Suman Department of Engineering – University of Ferrara
Annalisa Fortini Department of Engineering – University of Ferrara
Michele Gragnanini Department of Engineering – University of Ferrara