The L415/N08825 bimetallic composite pipe welded joint was produced by gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW) using nickel superalloy Inconel 6625 filler. The dendritic austenite grows in the direction perpendicular to the fusion line in the weld metal. The main elements, such as Cr, Ni, Mo and Fe show a large concentration gradient in the interface of the HAZ and weld metal. The unmixed zone in the three-phase zone is because of the differences in thermo-physics properties. The yield strength and tensile strength are 432 and 582 MPa, respectively. The interface between the cladding layer and the base layer fracture first, then the cladding layer, and the base layer finally. Compared with the impact toughness of the weld metal, the HAZ has a better impact toughness. Moreover, the average hardness of the weld is higher than that of the base metal and the HAZ. After welding, the HAZ is softened, and the hardness of the fusion line is higher than that of the base metal. The mechanical properties of the welded joint meet the standard requirements and it is advisable to use the GTAW + SMAW process for the welding of L415/N08825 bimetallic composite pipe.

L415/N08825双金属复合管焊接接头采用镍超合金Inconel 6625填料通过钨极气体保护焊（GTAW）和保护金属电弧焊（SMAW）生产。枝晶奥氏体在焊缝金属中沿垂直于熔合线的方向生长。主要元素，如 Cr、Ni、Mo 和 Fe 在 HAZ 和焊缝金属的界面表现出很大的浓度梯度。三相区中的未混合区是由于热物理性质的差异。屈服强度和抗拉强度分别为 432 和 582 MPa。包层和基层的界面首先断裂，然后是包层，最后是基层。与焊缝金属的冲击韧性相比，HAZ具有更好的冲击韧性。而且，焊缝的平均硬度高于母材和热影响区。焊后HAZ软化，熔合线硬度高于母材。焊接接头的力学性能符合标准要求，L415/N08825双金属复合管的焊接宜采用GTAW+SMAW工艺。