In Situ Temperature Measurements of Sliding Surface by Raman Spectroscopy

Abstract

In the current study, surface temperature in sliding contacts was in situ measured by Raman spectroscopy. The contact area comprised a stationary sapphire hemisphere and a rotating carbon steel disk. The surface temperature was estimated from the Raman spectrum of sapphire. Three estimation methods of temperature were compared, which were obtained from the peak shift, full width at half maximum (FWHM), and intensity ratio of Stokes/anti-Stokes scattering. The estimated temperature from the peak shift exhibited the least fluctuations among the three methods. However, the peak shift varied with stress and temperature. The estimated temperature from the FWHM was highly accurate, although the fluctuation was greater than that from the peak shift. The estimated temperature from the intensity ratio of Stokes/anti-Stokes scattering was unaffected by pressure and crystallinity, although this estimated temperature exhibited a significant fluctuation because the signal-to-noise ratio of the anti-Stokes scattering was small. This in situ measurement technique using Raman spectroscopy can simultaneously acquire the temperature and chemical state of the sliding surface. Namely, the temperature of a tribofilm and the temperature during scuffing can be measured directly and the mechanism can be analyzed effectively.