石墨和碳化物形态对高镍奥氏体球铁抗热冲击性能的影响

The Effect of Morphology of Graphite and Carbide in High-Nickel Austenitic Ductile Iron on Its Resistance to Thermal Shock

本文论述了合金元素Si,Cr,Mo对含Ni20％的高镍奥氏体球墨铸铁抗热冲击性能的影响,揭示了石墨和碳化物形态与热冲击疲劳裂纹扩展方式和扩展速率之间的关系。发现石墨呈球状时热冲击疲劳裂纹为晶界型裂纹,抗热冲击性能最好;呈片状时为穿晶型裂纹,抗热冲击性能最差,呈枝晶状时为(晶界加穿晶)混合型裂纹,抗热冲击性能介于前二者之间.加入适量的Cr,Mo,Si可显著地提高抗热冲击性能。

The effects of alloying elements Cr, Mo and Si in austenitic cast iron with a 20%nickel content on its resistance to thermal shock and the relationship between the morphology of graphite and carbide and the crack extension type and its speed due to thermal shock are discussed. For spheroidal graphite iron, it has been found that the crack due to thermal shock is a grain boundary one and its resistance to thermal shock is the highest. For lamellar graphite iron, the crack is a transgranular one and the resistance to thermal shock is the lowest. For dendritic graphite iron, the crack is a hybrid one and the resistance is between those of spheroidal and lamellar graphite irons. The resistance can be significantly improved with suitable contents of Cr, Mo and Si in the spheroidal austenitic cast irons.