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拉弗斯相(Laves相)是超超临界机组用新型耐热钢——P92钢的重要析出相之一,对其在扫描电镜下的尺寸测量方法进行介绍,并采用热力学软件计算分析其长大规律。在扫描电镜下形成的背散射图像的原子序数差及二次电子像能够清晰地辨别出Laves相和碳化物(M23C6),这是Laves相测量方法的基础。通过与透射电镜对比,表明扫描电镜是分析Laves相的优先使用的方法。测量了3种P92钢中Laves相颗粒尺寸,研究表明Laves相颗粒尺寸越小,数量越多,材料的抗蠕变性能越好,相同条件下蠕变断裂时间越长。采用热力学计算程序DICTRA进行数值模拟,结果表明,所采用的Laves相长大模型能够很好地模拟Laves相的长大规律,但长时间(650℃、20000h和600℃、50000h)后应采用奥斯特瓦尔德长大规律(Ostwald ripening)来分析Laves相。
Laves phase is one of the important precipitated phases of the new type of heat-resisting steel-P92 steel used in ultra-supercritical units. The method of dimension measurement under scanning electron microscope (SEM) is introduced and its length is calculated and calculated by using thermodynamic software Big law. The difference of atomic number and secondary electron image of the backscattered image formed by scanning electron microscopy can clearly distinguish the Laves phase and the carbide (M23C6), which is the basis of Laves phase measurement. By contrast with transmission electron microscopy, SEM showed that Laves phase was the preferred method of analysis. The particle size of Laves phase in three P92 steels was measured. The results showed that the smaller the Laves phase particle size is, the better the creep resistance of the material is and the longer the creep rupture time under the same conditions. The thermodynamic calculation program DICTRA is used for numerical simulation. The results show that the Laves phase growth model can simulate the growth law of Laves phase well. However, after long time (650 ℃, 20000h and 600 ℃, 50000h) Ostwald ripening to analyze the Laves phase.