Study Of Ni-Fe-graphite Self-lubricating Material

The adding of iron component into the Ni-graphite alloy has the effect of solidsolution strengthening on the matrix. And the alloy has the excellent anti-erosion andanti-oxidation. At the same time ,the using of ironwill save nonferrous metal nickeland the material cost will reduce. The Ni-Fe-graphite self-lubricating material wasproduced by melting method. The 1% silicon was added to prevent the generation ofcarbide. The results showed that the melting method had many merits vs powermetallurgy method, such as the dense and homogeneous structure. And the existentialstate of carbon atom is the graphite in the alloy. The RE-Mg nodularizer was addedfrom the above of melt. The graphite of alloy is not nodularized, but the RE-Mgnodularizer has the effect of inoculation on the solidifying graphite of the alloy andsmall eutectic graphite erases. And all the graphite exists with the primary phase. The effect of the adding of RE-Mg nodularizer and the effects of iron contentson the mechanical properties were investigated. After the adding of RE-Mgnodularizer, the impact toughness, the tensile strength, the bending strength anddeflection strength increase. And the coefficient of thermal expansion reduce. TheNi-Fe-graphite alloy has the excellent impact toughness. The average impacttoughness value is eight times of the average impact toughness value of Ni-Ag-graphite with the power metallurgy method. The values of the coefficient of thermalexpansion are from 6.13×10-6k-1 to 9.60×10-6k-1 which are smaller than thespheroidal graphite casting whose coefficient of thermal expansion is 13.5×10-6k-1.With the increasing of iron contents, the area density of graphite increases. And thedensity, the impact toughness, the tensile strength, the bending strength, deflectionstrength and the coefficient of thermal expansion of alloy reduce. The hardnessreduces at first and increases then. The results of friction and wear experiments showed that the contents of graphiteincreased with the increasing of iron contents and the self-lubricating propertiesincreased. Both the dry friction coefficient and oil lubrication coefficient reduce withthe increasing of iron contents and the wear rate reduces with the increasing ofhardness values. The friction coefficient is not related with the adding of RE-Mgnodularizer. It reduces with the increasing of the graphite contents. The dry frictioncoefficient ofNi-60%Fe-3.5%C-1%Si alloy is the smallest. Though friction and wearexperiment against GCr15 bearing steel, the dry friction coefficient and oil lubricationcoefficient of the alloy remained stably as 0.18 and 0.40 respectively. Through oillubricating friction and wear experiment against 45# annealed steel and GCr15bearing steel respectively, the former friction coefficient of Ni-Fe-graphite alloy issmaller than the latter. Under the condition of dry friction and wear experiment, withthe improvingof sliding speed, the friction coefficient of Ni-40%Fe-3.5%C-1%SiandNi-60%Fe-3.5%C-1%Si reduce. The friction coefficient of Ni-20%Fe-3.5%C-1%Siincreases with the improving of sliding speed. And the wear rate increases with theimproving of sliding speed. After the adding of RE-Mg nodularizer, the wear rate ofthe material reduced. And the forming of solid lubricating film follows the tinyprotruding object model.