Ni含量对中硅钼球墨铸铁显微组织及性能影响

The Effect of Ni Content on the Microstructure and Mechanical Properties of Heat Resistant Ductile Iron with Heavy Section

中硅钼球墨铸铁具有良好的力学性能和耐热性能,可用于制备各类大型耐热铸件。使用光学显微镜、扫描电子显微镜、拉伸试验机及布氏硬度计等,研究了Ni含量对中硅钼球墨铸铁显微组织、力学性能及耐热性能的影响,结果表明:随着Ni含量增加,铸态球墨铸铁中石墨球尺寸有所减小,数量略微增加。Ni促进球墨铸铁基体组织中珠光体形成,Ni质量分数由0%增加至1.9%后,珠光体质量分数增加20%。力学性能测试表明:添加Ni能够显著提高中硅钼球墨铸铁合金的强度和硬度,但降低其塑性,Ni为1.9%时,球墨铸铁具有最高的强度和硬度,其抗拉强度、硬度和延伸率分别为618 MPa、218 HBW和12.0%。抗氧化测试表明:添加Ni不利于耐热性能的提高,随着Ni含量增加,氧化膜厚度逐渐增加,不含Ni的试样氧化膜厚度为55.66μm,含Ni量为1.9%时氧化膜厚度为341.41μm,与不加Ni时相比增加了285.75μm。

The medium-silicon molybdenum ductile iron exhibits good mechanical and heat-resistant properties,making it suitable for preparing various large-scale heat-resistant castings.This study investigated the influence of Ni content on the microstructure,mechanical properties and oxidation resistance of the medium-silicon molybdenum ductile iron using optical microscopy,scanning electron microscopy,tensile testing machine,and Brinell hardness tester.The results indicated that with the increase of Ni content,the size of graphite nodules in as-cast ductile iron decreased,while the number of graphite nodules increased slightly.Ni can promote the formation of pearlite in the matrix of ductile iron,resulting in a 20%increase in pearlite content when the Ni content increased from 0%to 1.9%.The mechanical tests showed that the addition of Ni can significantly improve the strength and hardness of the medium-silicon molybdenum ductile iron but reduced its plasticity.When the Ni content was 1.9%,the ductile iron had the highest strength and hardness,with a tensile strength,hardness,and elongation of 618 MPa,218 HBW,and 12.0%,respectively.However,the oxidation resistance test showed that adding Ni was detrimental to the heat resistance performance.As the Ni content increased,the thickness of the oxidation film gradually increased.The thickness of the oxidation film was 55.66μm for the sample without Ni and increased to 341.41μm when the Ni content was 1.9%,a difference of 285.75μm.