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

Abstract

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/cm3, 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℃, 60℃, 70℃, 80℃ and 90℃ 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℃, 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.