The tribological properties of solid lubrication graphite coatings prepared by a sol-gel method

摘要

Graphite is an excellent solid lubricant 1 and has been extensively used as a coating 2-5, The usual methods to prepare the coating are bonding 6, magnetic control sputtering 7, and pulse laser deposition 8, whereas the sol-gel method has been hardly used. Our results show that a sol-gel graphite coating produces remarkable tribological properties. The substrate material was AISI 1045 steel, with hardness HRC52. The granularity of the graphite powder was 5 mu m. The colloidal solution (solvent) was a patented inorganic silicon water-based paint (ZM-1). The filler materials (solute) were a mixture of graphite and zinc powders with diameters of 5 mu m. When making up the colloidal sol, 500 ml solvent and 100 g solute were measured and mixed. The solute, which was composed of the graphite and zinc powders, contained 25 g graphite and 75 g zinc. 15 minutes stirring was needed to form a homogeneous sol, in which graphite powder was used as the solid lubricant and Zn was employed to provide a platform for the graphite powder. As a soft metal, the zinc powder is theoretically also a lubricant. The sol-gel graphite coating was about 350 mu m thick.