Sirohi Sachin, Kumar Amit, Pandey Shailesh M, Purohit Priyambada, Fydrych Dariusz, Kumar Sanjeev, Pandey Chandan
Department of Mechanical Engineering, SRM Institute of Science and Technology, Delhi NCR Campus, Modinagar, 201204, Uttar Pradesh, India.
Department of Mechanical Engineering, Indian Institute of Technology Jodhpur, Jodhpur, 342037, Rajasthan, India.
Heliyon. 2023 Sep 7;9(9):e19945. doi: 10.1016/j.heliyon.2023.e19945. eCollection 2023 Sep.
To reduce costs and improve high-temperature performance in Advanced Ultra Super Critical (AUSC) boilers, it is necessary to weld austenitic steel to Inconel alloy. In this study, the autogenous tungsten inert gas (TIG) welding process was used to join Alloy 617 and an austenitic AISI 304H steel plate of thickness 5 mm. Microstructural analysis showed that the microstructure formation was uneven along the weldments, with columnar and cellular dendrites near the interface while the central area of the weld exhibited a combination of columnar, cellular, and equiaxed dendrites. The use of energy dispersive spectroscopy and electron probe micro-analysis unveiled the presence of an unmixed layer at the interface between the weld and AISI 304H steel. Furthermore, a notable variation in the concentration of alloying elements such as Fe, Cr, Ni, Co, and Mo was observed. Within the weld metal, inter-dendritic areas showed the presence of precipitates rich in Cr, Ti, and Mo. Meanwhile, the heat-affected zone (HAZ) of Alloy 617 exhibited the presence of phases like Cr and Mo-rich MC as well as Mo-rich MC. Hardness tests showed non-uniform hardness along the weldments, with a hardness of 199 ± 6 HV in the weld metal and 225 ± 4 HV in Alloy 617 HAZ, and 207 ± 7 HV in AISI 304H HAZ. The Mo and Cr segregation in the inter-dendritic spaces led to a decline in the tensile properties of the welded parts and resulted in failure from the region of the weld metal.
为降低先进超超临界（AUSC）锅炉的成本并提高其高温性能，有必要将奥氏体钢与因科镍合金焊接在一起。在本研究中，采用自熔性钨极惰性气体（TIG）焊接工艺将617合金与一块厚度为5毫米的奥氏体AISI 304H钢板连接起来。微观结构分析表明，沿焊件的微观结构形成不均匀，界面附近有柱状和胞状枝晶，而焊缝中心区域则呈现柱状、胞状和等轴枝晶的组合。利用能量色散光谱和电子探针微分析揭示了焊缝与AISI 304H钢界面处存在未混合层。此外，还观察到Fe、Cr、Ni、Co和Mo等合金元素浓度的显著变化。在焊缝金属中，枝晶间区域存在富含Cr、Ti和Mo的析出物。同时，617合金的热影响区（HAZ）出现了富Cr和Mo的MC相以及富Mo的MC相。硬度测试表明，沿焊件硬度不均匀，焊缝金属硬度为199±6 HV，617合金热影响区硬度为225±4 HV，AISI 304H钢热影响区硬度为207±7 HV。枝晶间空间中的Mo和Cr偏析导致焊接部件的拉伸性能下降，并导致焊缝金属区域发生失效。
