Tribological behaviors of polyimide composite coatings containing carbon nanotubes and fluorinated graphene with hybrid phase or blend phase

•Modified fluorinated graphene (FG) and carbon nanotubes (CNT) were added into polyimide to construct hybrid phase and blend phase.•The Chemical structure and composition of FG and CNT were investigated systematically.•Moreover, we revealed the influence of mechanical properties and lubrication properties on the tribological properties of PI composite coatings.•The better lubricating performance of the hybrid phase led to improved anti-friction performance.•And the better mechanical properties of the blended phase led to excellent anti-wear performance. In this work, hybrid phase and blend phase composed of carbon nanotube (CNT) and fluorinated graphene (FG) were doped into pure polyimide via a solution doping method to improve the tribological properties of polyimide. The effect of the hybrid phase and blend phase on mechanical and tribological properties of polyimide (PI) composite coatings were systematically investigated. The results showed that there was a much stronger interfacial interaction to enhance the mechanical properties of PI composite coating modified by the blend phase. The tensile strength increased by 46 %, hardness increased by 43 %, and storage modulus increased by 96 % at room temperature. The significantly enhanced mechanical properties can provide plenty of energy to resist wear for PI composite coating, and thus resulting in a 61 % reduction in wear rate. In addition, due to the lubricating properties imparted by the hybrid phase, the coefficient of friction (COF) of PI composite coating modified by hybrid phase was reduced by 13 %, showing the best anti-friction performance.