The manuscript described the effect of Ni-based filler on microstructure and mechanical properties of the dissimilar welded ASTM A335 grade P22 and P91 alloy steel plate. The dissimilar welds joint (DWJ) was produced using the Gas Tungsten Arc Welding (GTAW) process. The DWJ was characterized for metallographic and mechanical testing for as-welded and post-weld heat treatment (PWHT) conditions. For mechanical properties, microhardness, tensile test and Charpy impact test were performed. The DWJ showed the heterogeneity in microstructure and mechanical properties (microhardness, impact toughness) along the welded joint. The weld metal showed the formation of the austenitic microstructure consisted of the equiaxed dendrite along with segregation of the alloying elements like Cr, Mo, and Ti at the inter-dendritic boundaries, while P91 and P22 HAZ showed the formation of coarse-grained, fine-grained, and inter-critical heat-affected region depends on the temperature experienced during the welding cycle. The region of P91 HAZ was characterized by untempered and tempered martensite, while P22 HAZ was characterized by coarse and fine bainitic microstructure. The PWHT showed a negligible effect on the microstructure of the weld metal, while a significant change in microstructure of P91 HAZ and P22 HAZ was observed. PWHT also led to the formation of the soft and hard zone along the interface of the P22 steel due to the carbon diffusion. At the interface of the weld metal and base material, a sharp gradient was observed for the elements Cr, Fe, Ni and Mo. The weld metal near the interface showed the columnar dendritic structure having segregation of the alloying elements Mo, Ti and Cr along the inter-dendrite boundaries. A variation in hardness was measured along the weldments for as-welded and PWHT conditions. The peak hardness was measured in P91 coarse-grained heat-affected zone (CGHAZ) for both as-welded and PWHT, while the poor hardness of 202 HV and 195 HV was measured for weld metal in as-welded and PWHT conditions. The strength of the welded joint was measured higher than the strength of P22 steel for both conditions; however, the fracture was observed in P22 base metal for the as-welded joint, while in PWHT, it was in P22 HAZ near the interface. A variation in Charpy impact toughness was observed along the weldment for both as-welded and PWHT conditions. In as-welded, the minimum Charpy impact toughness (CIT) of 95.8 J was measured in weld metal, while the maximum was 152 J in P91 HAZ. After the PWHT HAZ region of P22 and P91 steel showed a drastic increase in CIT, however reduction in CIT of the weld metal was measured.

手稿描述了镍基填料对异种焊接 ASTM A335 级 P22 和 P91 合金钢板的显微组织和机械性能的影响。异种焊接接头 (DWJ) 是使用气体钨极电弧焊 (GTAW) 工艺生产的。DWJ 的特点是用于焊后和焊后热处理 (PWHT) 条件的金相和机械测试。对于机械性能，进行了显微硬度、拉伸试验和夏比冲击试验。DWJ 显示沿焊接接头的显微组织和机械性能（显微硬度、冲击韧性）的不均匀性。焊缝金属显示出由等轴枝晶组成的奥氏体显微组织的形成以及枝晶间边界处的合金元素如 Cr、Mo 和 Ti 的偏析，而 P91 和 P22 HAZ 显示粗晶、细晶和临界间热影响区的形成取决于焊接周期中经历的温度。P91热影响区区域以未回火和回火马氏体为特征，而P22热影响区以粗、细贝氏体组织为特征。焊后热处理对焊缝金属的显微组织的影响可以忽略不计，而观察到 P91 HAZ 和 P22 HAZ 显微组织的显着变化。由于碳扩散，PWHT 还导致沿 P22 钢界面形成软硬区。在焊缝金属与母材的界面处，观察到元素Cr、Fe、Ni和Mo的急剧梯度。界面附近的焊缝金属呈柱状枝晶结构，合金元素Mo偏析，Ti 和 Cr 沿枝晶间边界。在焊态和 PWHT 条件下，沿焊件测量硬度的变化。在焊态和 PWHT 的 P91 粗晶热影响区 (CGHAZ) 中测量了峰值硬度，而在焊态和 PWHT 条件下测量的焊缝金属的硬度差为 202 HV 和 195 HV。在这两种情况下，焊接接头的强度均高于 P22 钢的强度；然而，在焊接接头的 P22 母材中观察到断裂，而在 PWHT 中，它发生在界面附近的 P22 HAZ。在焊态和 PWHT 条件下，沿焊件观察到夏比冲击韧性的变化。在焊态中，焊缝金属的夏比冲击韧性 (CIT) 最小值为 95.8 J，而 P91 HAZ 中的最大值为 152 J。