High-temperature low-friction behaviors of γ-Fe₂O₃@SiO₂ nanocomposite coatings obtained through sol–gel method

In the present paper, the γ-Fe₂O₃@SiO₂ nanocomposite is prepared by sol–gel method and the γ-Fe₂O₃@SiO₂ nanocomposite coatings are deposited on the steel substrate. The microstructure, surface topography, and tribological properties of the γ-Fe₂O₃@SiO₂ nanocomposite were measured and investigated by X-ray diffraction (XRD), fourier transform infrared spectrometry (FTIR), transmission electron microcopy (TEM), and high-temperature tribometer, respectively. The tribotest were performed by high-temperature tribometer in the temperature ranges from 400 to 600 °C to investigate the tribological properties of the nanocomposites under high temperature. The experimental results show that there is the core-shell structure in the γ-Fe₂O₃@SiO₂ nanocomposite. It is also found that the γ-Fe₂O₃@SiO₂ nanocomposite coatings exhibit low friction (0.05) from 500 to 600 °C. XRD measurements show that low-friction behavior of the friction pair under high temperature is involved in the transformation between α-Fe₂O₃ and γ-Fe₂O₃ and the oxidations of the steel substrate during sliding. The core-shell structure of the nanocomposites inhibits γ-Fe₂O₃ of the soft phase changing into α-Fe₂O₃ phase and the thermal energy of the friction heat activates the oxidation of the steel substrate in ambient air, which are beneficial to form low shear interface and achieve high temperature low friction.