Preparation of novel polytetrafluoroethylene/copper-matrix self-lubricating composite materials

663-tin bronze, Ni, W, nano-Al2O3 and Ni-coated graphite mixed as the fundamental alloy powder was added in concentrations of 5 vol.%, 7 vol.%, 9 vol.%, 11 vol.% and 13 vol.% NH4HCO3 respectively to prepare composite powders. Powder metallurgy method was applied to prepare porous materials with these composite powders. Polytetrafluoroethylene was hot-dipped into the pores of the materials to prepare novel polytetrafluoroethylene/copper-matrix self-lubricating composite materials. It was observed that the mechanical properties of the porous materials first increase and then decline with the increase of the added volume fraction of the pore-forming material (NH4HCO3) from 5% to 13%. When the added volume fraction of NH4HCO3 was 9%, the mechanical properties of the sample reached the maximum: its density was -5.52 g/cm(3), hardness -35.5 HV and crushing strength -148 MPa. The samples containing 9% (volume fraction) NH4HCO3 were hot-dipped with polytetrafluoroethylene in the water bath at 50 degrees C, 60 degrees C, 70 degrees C, 80 degrees C and 90 degrees C respectively for 1.5 h, as a result of which the content of polytetrafluoroethylene in the samples first increased and then declined with the rise of temperature. When the temperature was 60 degrees C, the content of polytetrafluoroethylene in the sample reached the maximum, indicating that the frictional performance obviously improved by the polytetrafluoroethylene: the wear loss was 6 mg and friction coefficient was 0.08, which proved that the novel polytetrafluoroethylene/copper-matrix composite material had excellent self-lubricating properties.