Friction performance and mechanisms of calcined products of Mg/Al layered double hydroxides as lubricant additives

Abstract

Mg/Al layered double hydroxides (LDHs) and the calcined products were prepared and the powders were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray fluorescence (XRF) and Fourier transform infrared spectrometer (FT-IR). The friction properties of LDHs and the calcined products were tested and the rubbed areas were analyzed by scanning electron microscope, energy disperse spectroscopy (EDS) and auger electron spectrometer (AES). The results showed that the diameter of LDHs was about 100–175 nm and the formula was Mg0.69Al0.31(OH)2(CO3)0.15·0.16H2O. All the calcined products had the laminated structure. The anti-wear properties of 1000 °C calcined products were superior to the LDHs, which was attributed to the supporting and mechanical polishing effects of the hard spinels. The distribution laws of elements of worn area in the horizontal and vertical direction were concluded. The tribological performance of calcined products can be attributed to the “multi-layer self-lubrication mechanisms”. The tribofilms consisted of “carbon-enriched layer”, “oxygen- enriched layer” and “transition layer” and combined strongly with the metal substrate.