| Copper powder metallurgy friction materials have been widely used in manufacturingbrake components of high-speed train and military machinery because of high coefficientand wear resistance.Fe is often used as a friction element in copper powder metallurgyfriction materials in order to improve the friction coefficient.Powder injection moldingtechnology can eliminate the problem such as density gradient and so on generated in theprocess of traditional powder metallurgy; it can form large qualities of complex shape metalparts which have uniform components and excellent performance.In this paper, Cu-Fe-C friction materials were prepared by mental injection moldingtechnology and excellent performance test samples were obtained by optimizing the processparameters. Electron microscopy, ultra depth for field optical microscope, friction and wearmachine and other equipments were used. Microstructure, mechanical properties andfriction and wear performance of Cu-Fe-C friction materials were analyzed. Also effect ofthe content of Fe on the mechanical properties,friction and wear performance of Cu-Fe-Cfriction materials.The results show that high powder loading and thermoplastic olefin-based bindersystem can ensure that the feed has good liquidity and conductive to subsequent degreasingprocess. The best process parameters for feed preparation were obtained. The powderloading was58%, binder was65%PW+30%LDPE+5%SA.Mixing temperature was130~145℃, mixing time was2hours.The orthogonal experiment was used to design multiple parameter combinations andeffect of parameters such as injection temperature, time, pressure on the quality of billet wasresearched. The best injection parameters were received through optimizing the injectionprocess parameters. Injection temperature was155℃, injection pressure was115MPa,injection speed was45m s-1.The solvent-hot two-step degreasing process was used fordegreasing. The results show that the solvent degreasing process was40℃×6h and the rateof binder removal can reach76%and the connected porosity networks are formed. Bythermal degreasing at300℃under low elevation rate, the degreasing blank without defectscan be obtained. The ideal thermal degreasing process was2℃/min heating to160℃(holding60min)â†'1℃/min heating to300℃(holding90min)â†'3℃/min heating500℃(holding60min)â†'5℃/min heating600℃(holding60min)â†'furnace cooling to room temperature.Effects of the sintering temperature, time and atmosphere on properties of sinteredparts were studied. The results show that H sintering atmosphere and proper insulationlower than900℃,can restore the residual oxide fully. The ideal sintering process was5℃/min heating to700℃(holding120min)â†'5℃/min heating to800℃(holding120min)â†'5℃/min heating900℃(holding120min)â†'5℃/min heating1050℃(holding180min)â†'furnace cooling to room temperature.As the content of Fe increased, the density of Cu-Fe-C friction materials reducedslightly. High hardness, wear resistance Fe particles which distributed in copper matrix,improved the hardness and strength of materials. When the content of Fe was8%,thehardness of materials was58HV,the tensile strength was148Mpa.Pore and graphite betweencopper particles was the main source of crack and expansion and it can make materialsbrittle fracture. When the friction velocity was100~400r/min, with the increased of thecontent of Fe, Fe turned to rigid particles and generated strong plow to the dual parts whichincreased the friction coefficient. Also, the wear rate increased and the friction and wearproperties of materials reduced because Fe enhanced the role of partitioning on the matrix. |
PDF Full Text Request