In the present investigation, a detailed microstructure and mechanical behaviour study for P91 welded joint were investigated. The welded joint was produced using the Gas Tungsten Arc welding (GTAW) process with dissimilar Ni-based filler IN625 (ERNiCrMo-3). For microstructure characterization of the weld joint, optical microscopy and scanning electron microscopy were utilized. The effort was made to get a relationship between microstructure and mechanical properties variation. The residual stress measurement was also carried out for both the condition by using the hole-drilling method. To evaluate the mechanical properties, tensile testing and Charpy testing was done at room temperature. The weld joint developed with dissimilar Ni-based filler processes the austenitic microstructure having equiaxed dendrites in bulk weld metal and columnar and cellular dendritic structure near the interface. The segregation of the alloying elements like Mo and Nb was also confirmed along the inter-dendritic areas. The welded joint qualified the tensile test and Charpy test with average value of 580 ± 12 MPa and 65 ± 5 J, respectively in as-welded. However, a reduction was observed in tensile strength and Charpy toughness after the PWHT. A significant variation in microhardness was measured across the welds joint, and peak hardness was measured about 344 HV in the coarse-grained heat affected region while in weld metal it was 263 HV. The peak hardness value in HAZ and variation in hardness also get reduced after the PWHT. In the weld metal, a significant variation in the residual stresses was measured along the thickness with peak magnitude 250 MPa and 172 MPa for longitudinal and transverse stress, respectively in the as-welded condition. A significant reduction in peak residual stresses (longitudinal stress and transverse stress) was obtained after the PWHT.

在本研究中，对 P91 焊接接头进行了详细的微观结构和力学行为研究。焊接接头采用钨极气体保护焊 (GTAW) 工艺和不同的镍基填料 IN625 (ERNiCrMo-3) 制成。对于焊接接头的微观结构表征，使用了光学显微镜和扫描电子显微镜。努力获得微观结构和机械性能变化之间的关系。残余应力测量也是通过使用钻孔方法对这两种情况进行的。为了评估机械性能，在室温下进行拉伸试验和夏比试验。用异种镍基填料开发的焊接接头加工了块状焊缝金属中具有等轴枝晶的奥氏体组织和界面附近的柱状和蜂窝状枝晶结构。在枝晶间区域也证实了合金元素如 Mo 和 Nb 的偏析。焊接接头在焊接状态下通过拉伸试验和夏比试验合格，平均值分别为 580 ± 12 MPa 和 65 ± 5 J。然而，在 PWHT 后观察到拉伸强度和夏比韧性降低。在整个焊接接头处测得显微硬度的显着变化，在粗晶热影响区测得的峰值硬度约为 344 HV，而在焊缝金属中为 263 HV。在 PWHT 之后，HAZ 中的峰值硬度值和硬度的变化也减少了。在焊缝金属中，在焊接状态下，纵向和横向应力的峰值分别为 250 MPa 和 172 MPa，沿厚度方向测量到的残余应力有显着变化。焊后热处理后峰值残余应力（纵向应力和横向应力）显着降低。