Kumar Amit, Pandey Shailesh M, Sirohi Sachin, Fydrych Dariusz, Pandey Chandan
Department of Mechanical Engineering, IIT Jodhpur, Jodhpur, 342037, India.
Department of Mechanical Engineering, NIT Patna, Patna, 201204, India.
Heliyon. 2023 Aug 7;9(8):e18959. doi: 10.1016/j.heliyon.2023.e18959. eCollection 2023 Aug.
The objective of the current study was to analyse the microstructure, mechanical characteristics, and residual stresses of a dissimilar welded joint (DWJ) made of P92 steel and the Inconel alloy 617 (IN617) using the gas tungsten arc welding (GTAW) method. The ERNiCr-3 filler was selected to produce the conventional V groove (VG) and narrow V groove (NVG) butt joint. The filler deficient zones in the weldments, such as the filler deficient beach, i.e. unmixed zone (UZ), peninsula, and island, as well as the distinct heat-affected zone (HAZ), were visible near the interface of ERNiCr-3 filler weld and P92 steel due to the distinct differences in the chemical composition, microstructure, and mechanical properties between the filler and P92 base metal (BM). A very narrow partial melted zone (PMZ) and almost negligible UZ and HAZ were noticed at the interface of IN617 and ERNiCr-3 weld metal and it occurred mainly due to the similarity in microstructure and melting point. The austenitic microstructure of ERNiCr-3 filler weld was accompanied by precipitates enriched with Ti and Nb along with the inter-dendritic space. At room temperature, the mechanical properties of both the groove joints were evaluated, and the test results indicated that the welded joint satisfied the standard requirements for AUSC power plants' boiler applications. The tensile test results showed the failure from ERNiCr-3 filler weld with a tensile strength of 627 ± 2 MPa and 636 ± 3 MPa for VG and NVG welded joints, respectively. A poor weld metal impact toughness in comparison to the BMs was attributed to the presence of the brittle Ti(C, N) and Nb(C) particles in the interdendritic space. The impact toughness for the NVG weld joint was measured higher than for the VG weld joint. A significant hardness deviation was measured along the weldments that might be due to heterogeneous microstructure, i.e. UZ, HAZ, delta ferrite, and weld metal. To impart the ductility and temper the martensite in P92 HAZ, post-weld heat treatment (PWHT) was also performed, and a studied their effect on microstructure evolution across the weldments and mechanical properties. Groove design also showed a significant effect on residual stress variation. The work highlights the groove geometry, welding procedure, evolution of the microstructure along the weldments, mechanical characteristics, and residual stress variation of DWJ of P92 steel and IN617 alloy. In comparison to conventional VG joints, the NVG joints exhibited superior mechanical properties and lower residual stress values.
本研究的目的是采用钨极气体保护电弧焊（GTAW）方法，分析由P92钢和因科镍合金617（IN617）制成的异种焊接接头（DWJ）的微观结构、力学性能和残余应力。选用ERNiCr-3填充材料来制作传统V型坡口（VG）和窄V型坡口（NVG）对接接头。由于填充材料与P92母材（BM）在化学成分、微观结构和力学性能上存在明显差异，在ERNiCr-3填充焊缝与P92钢的界面附近，焊件中的填充材料不足区域，如填充材料不足的熔合线，即未混合区（UZ）、半岛状区域和岛状区域，以及明显的热影响区（HAZ）清晰可见。在IN617与ERNiCr-3焊缝金属的界面处，发现了一个非常狭窄的部分熔化区（PMZ），UZ和HAZ几乎可以忽略不计，这主要是由于微观结构和熔点相似所致。ERNiCr-3填充焊缝的奥氏体微观结构伴随着沿枝晶间空间富集Ti和Nb的析出物。在室温下，对两种坡口接头的力学性能进行了评估，测试结果表明，焊接接头满足AUSC发电厂锅炉应用的标准要求。拉伸试验结果显示，断裂发生在ERNiCr-3填充焊缝处，VG和NVG焊接接头的抗拉强度分别为627±2MPa和636±3MPa。与母材相比，焊缝金属的冲击韧性较差，这归因于枝晶间空间中存在脆性的Ti（C，N）和Nb（C）颗粒。NVG焊接接头的冲击韧性高于VG焊接接头。沿焊件测量到显著的硬度偏差，这可能是由于微观结构不均匀，即UZ、HAZ、δ铁素体和焊缝金属所致。为了赋予P92热影响区韧性并回火马氏体，还进行了焊后热处理（PWHT），并研究了其对整个焊件微观结构演变和力学性能的影响。坡口设计对残余应力变化也有显著影响。这项工作突出了P92钢和IN617合金DWJ的坡口几何形状、焊接工艺、沿焊件的微观结构演变、力学性能和残余应力变化。与传统的VG接头相比，NVG接头具有更好的力学性能和更低的残余应力值。
