汽车排气歧管用球墨铸铁的显微组织和抗腐蚀性研究

Study on the Microstructures and Corrosion Resistance of Ductile Iron for Exhaust Manifold

通过LOM、XRD、SEM和EDS等手段对所开发的汽车排气歧管材料进行组织分析,说明了高硅钼球墨铸铁的组织是由铁素体、球状石墨和钼的碳化物构成;而高镍球墨铸铁的组织主要由奥氏体、金属间化合物FeNi3和富锰、铬的碳化物构成。并利用电化学综合测试系统进行腐蚀电位和腐蚀电流测试。结果表明:高硅钼球墨铸铁的极化曲线中存在明显的钝化区,但高镍球墨铸铁的腐蚀电位更倾向于正电位,其耐蚀性优于高硅钼球墨铸铁。

The exhaust manifold materials were investigated by LOM and XRD and SEM and EDS.The studies show the microstructure of high Si-Mo ductile iron is composed of ferrite and spheroidal graphite and some bone shaped carbides,and the microstructure of high Ni ductile iron is mainly composed of austenite,intermetallic compound FeNi3 and carbide of Mn and Cr.The corrosion potential and corrosion current of high Si-Mo ductile iron and high-Ni ductile iron were achieved by galvano-chemistry test macro.The result show that there is a transpassive region at anodic polarization curve of high Si-Mo ductile iron,while the corrosion potential of high-Ni ductile iron is inclined to positive potential,the corrosion resistance ofhigh-Ni ductile iron is better than high Si-Mo ductile iron.