Ni含量对钒钛磁铁矿原位合成制备铁基摩擦材料的影响

Effect of Ni Content on Iron-based Friction Material Prepared by In-situ Synthesized from Vanadium-bearing Titanomagnetite Concentrates

以钒钛磁铁矿为主要原料,利用选择性碳热原位还原技术真空烧结制备铁基摩擦材料,研究添加合金元素Ni(1%~4%,质量分数,下同)对铁基摩擦材料的微观组织、力学性能及摩擦磨损行为的影响。结果表明:烧结试样由铁基体、润滑相石墨和硬质相(主要为TiC)3种组元构成,其基体组织主要是层片状的珠光体,具有较高强度和硬度。与未添加Ni的试样相比,添加Ni对铁基摩擦材料的组织和性能有不同程度的促进作用。添加少量的Ni(1%~2%)能有效促进材料烧结致密化,材料中的孔隙细小且数量较少,硬质相和石墨均匀分布,硬度和摩擦磨损性能均随着Ni含量的增加大幅度提高。但当Ni含量超过2%时,烧结试样中出现较大的孔洞并且石墨与硬质相均出现偏聚,材料硬度逐渐降低,磨损率和摩擦因数均随Ni含量的增加而有所增大。综合而言,当Ni含量为2%时材料的组织结构和性能均达到最佳。

A method for preparing iron-based friction material directly from the vanadium-bearing titanomagnetite concentrates by means of in-situ carbothermic reaction and sintering was presented.Effect of Ni content(1%-4%,mass fraction,the same below)on microstructure,mechanical properties and wear performance of iron-based friction material was investigated.The results show that the sintered sample consists of iron matrix,graphite lubricating phases and hard particles(mainly TiC).The matrix is predominantly composed of laminated pearlite with higher strength and hardness than those of ferrite.Compared with the sintered sample without Ni,the microstructure and properties of iron-based friction material are improved in varying degrees with different Ni contents.Low Ni content(1%-2%)promotes sintering process,which exhibits the decreasing amount of pores and uniform distribution of lubricating graphite phases and hard particles.Besides,the hardness and wear performance are improved significantly with the increase of Ni content.However,when Ni content exceeds 2%,not only the amount of pores increases,but also graphite phases and hard particles segregate in the microstructure,which result in decreasing hardness and poor wear performance of the material.To sum up,the microstructure and properties are the best when the Ni content is 2%.