Layered structure of friction films revealed by the comparison between multi-energy X-ray microanalysis and Monte Carlo simulations

Multi-energy X-ray spectra were acquired on friction films formed on semi-metallic brake pads rubbed against grey cast iron discs in friction tests at low and high speed, performed in a full scale bench dynamometer. The amount of X-rays generated with electrons in the same energy range as in the experimental measurements was calculated with Monte Carlo simulations performed with CASINO software, on structures of multi-layered and mixed phase films. The comparison of the qualitative behavior of the experimental peaks with results from the simulations enabled conclusions on layering, mixing, and thickness of the measured structure and revealed a layered structure on some friction films.