Investigation of microstructural evolution and creep rupture behaviour of 9% Cr MarBN steel welds
Investigation of microstructural evolution and creep rupture behaviour of 9% Cr MarBN steel welds
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DOI：
10.1016/j.msea.2020.139546
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发表时间：
2020-05
期刊：
影响因子：
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通讯作者：
Xu Xu-Xu;A. Benaarbia;D. Allen;M. Jepson;Wei Sun
中科院分区：
文献类型：
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作者：
Xu Xu-Xu;A. Benaarbia;D. Allen;M. Jepson;Wei Sun
由9-12%铬回火马氏体钢制成的焊接件具有复杂的显微组织，这是由于熔合区和热影响区的复杂热历史引起的。这些临界区复杂的微观结构和细观力学状态为确定蠕变破坏机制提供了挑战。通过详细的金相分析，确定了新近研制的9%CrMarBN-1钢焊接接头热影响区的组织分布，并将其分为等轴区(EZ)、双相区(DZ)和过回火区(OZ)。在650℃下进行的交叉焊接试验表明，与块状材料相比，蠕变寿命显著降低。蠕变断裂在高应力下以延性方式发生在母金属区域，而在低应力下蠕变断裂以沿晶方式发生在DZ区。详细的金相研究进一步揭示了沿先前存在的奥氏体晶界(PAGB)的区域具有较高的损伤敏感性。与置换再奥氏体化后形成的周围组织相比，沿PAGBs的局部组织的扩散再奥氏体化导致基体强度较低，同时缺少晶间析出物。
The weldments made from the 9–12% Cr tempered martensitic steel are associated with a complex microstructure arising from complicated thermal histories of the fusion and heat affected zones. The complicated microstructural and micro-mechanical states in these critical regions provide a challenge for the determination of creep failure mechanisms. Based on detailed metallographic examination, the microstructural distribution in the heat affected zone of the welds constructed using a recently developed 9% Cr MarBN steel, IBN-1, has been identified and classified into Equiaxed Zone (EZ), Duplex Zone (DZ) and Over-tempered Zone (OZ). Cross-weld testing performed at 650 °C has revealed a significant reduction in creep life as compared to bulk material. Creep rupture has been shown to occur in the parent metal region with a ductile manner at a high stress, whereas creep rupture initiates in the DZ region in an intergranular manner at a low stress. Detailed metallographic investigation has further revealed a higher damage susceptibility in the regions along the pre-existing Prior Austenite Grain Boundaries (PAGBs). The diffusional reaustenitisation of local microstructure along the PAGBs leads to a lower strength of matrix in combination with a lack of intergranular precipitates as compared to the surrounding microstructure formed after displacive reaustenitisation.