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通过蠕变曲线测定及组织形貌观察,研究了403Nb钢的蠕变性能特点、变形特征、组织及其变化规律。结果表明:403Nb钢具有明显的温度敏感性,在试验条件下,403Nb钢蠕变激活能为463 kJ/mol,组织为回火板条马氏体,相邻马氏体板条组间取向几乎垂直。在马氏体中存在高密度的位错和尺寸约0.2μm的残留NbC,在马氏体板条界,特别是晶界处沉淀大量更为细小的纳米Cr23C6。蠕变期间,NbC十分稳定,但晶界处(Cr,Fe)23C6部分向(Cr,Fe)7C3转变。403Nb钢的蠕变变形机制是晶界滑移、位错滑移及由位错增值束集引起的动态再结晶,对上述过程碳化物起到阻碍作用,提高了钢的蠕变抗力。
The creep property, deformation characteristics, microstructure and variation of 403Nb steel were studied by creep curve and microstructure observation. The results show that: 403Nb steel has obvious temperature sensitivity. Under the test conditions, the creep activation energy of 403Nb steel is 463 kJ / mol, the microstructure is tempered lath martensite, the orientation between adjacent martensite lath groups is almost vertical. In martensite, there are high-density dislocations and residual NbC of about 0.2 μm in size, precipitating a large amount of much smaller nanocrystalline Cr23C6 in martensite slab boundaries, especially in grain boundaries. During creep, NbC is very stable, but the (Cr, Fe) 23C6 part of the grain boundary changes to (Cr, Fe) 7C3. The creep deformation mechanism of 403Nb steel is the grain boundary slip, dislocation slip and dynamic recrystallization caused by the set of dislocation value added beam, which hinders the above carbides and improves the creep resistance of steel.