【作者】 陈丽娟；

【导师】 朱定一；

【作者基本信息】 福州大学 ， 材料学， 2005， 硕士

【摘要】 在 Ni-石墨合金中加入组元铁,一方面可以对基体起到固溶强化作用,使合金保持良好的抗腐蚀性和抗氧化性,另一方面可以节约有色金属镍,降低材料成本。本文采用熔炼法制备 Ni-Fe-石墨系合金,并添加 1%Si以防止碳化物的生成。结果表明,熔炼法相对粉末冶金法组织致密、均匀,碳原子在合金中均以石墨的形态存在。稀土镁球化剂从熔体上部加入,对合金组织中的石墨没有起到球化作用,但对凝固中的石墨却起到了孕育处理的作用,消除了细片状共晶石墨,石墨均以初生相的形态出现。 研究了添加稀土镁球化剂后及不同的铁含量对 Ni-Fe-石墨系自润滑材料的力学性能的影响。添加球化剂后材料的冲击韧性、抗拉强度、抗弯强度和挠度均大大提高,热膨胀系数减小。用熔炼法制备的 Ni-Fe-石墨系合金具有良好的冲击韧性,未添加球化剂的 Ni-Fe-石墨系合金的平均冲击韧性值约为粉末冶金法制备的 Ni-Ag-C 系合金的平均冲击韧性值的 8 倍。添加稀土镁球化剂的 Ni-Fe-石墨合金的热膨胀材料的热膨胀系数为 6.13×10-6k-1-9.60×10-6k-1,比球墨铸铁的热膨胀系数 13.5×10-6k-1 小。随着铁含量的增大,合金材料中的石墨面密度增大,Ni-Fe-石墨系合金的密度、冲击韧性、抗拉强度、抗弯强度、挠度和热膨胀系数均降低,而硬度值先减小后增大。 摩擦磨损试验结果显示,随着铁含量的增加,合金中的石墨含量增多,材料的自润滑性能提高,干摩擦因数和油润滑摩擦因数均减小,磨损率随着硬度值的增大而减小。摩擦因数与合金中有无添加球化剂无关,只与合金中的石墨面密度相关,石墨面密度越大,摩擦因数越小。其中 Ni-60%Fe-3.5%C-1%Si 合金的摩擦因数最小,与 GCr15 轴承钢对磨时,干摩擦因数和油润滑摩擦因数分别保持在 0.18 和 0.04。在油润滑摩擦磨损条件下,Ni-Fe-石墨合金与 45#退火钢的摩擦因数比其与 GCr15 轴承钢的摩擦因数小。在干摩擦磨损条件下,提高滑动速度,Ni-40%Fe-3.5%C-1%Si合金和 Ni-60%Fe-3.5%C-1%Si 合金的摩擦因数均减小,只有 Ni-20%Fe-3.5%C-1%Si 合金的摩擦因数随着滑动速度的提高而增大。而磨损率随着滑动速度的提高而增大。添加稀土镁球化剂后,材料的磨损率降低了。固体润滑膜的形成遵循微凸体模型。更多还原

【Abstract】 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 GCr15<WP=4>bearing 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.更多还原