This paper investigates the metallurgical behavior and mechanical properties of the P91 steel welds joint. The joint of heat-resistant P91 steel has been welded by the gas tungsten arc welding (GTAW) process using the dissimilar Inconel grade 617 filler. The P91 welds joints have been subjected to varying heat treatment regimes in the temperature range of 650–810 °C for 2 h. The normalizing-based tempering was also performed for the welded joint. The weld fusion zone (WFZ) with austenitic structure and heat-affected zones (HAZs) with martensitic structure was characterized using the optical microscope and scanning electron microscope (SEM). The detailed characterization of the weld metal and HAZ interface has also been performed for as-welded and post-weld heat treatment (PWHT) conditions. For mechanical properties of the welds joint, tensile testing and hardness testing were performed. The relationship between mechanical behavior and microstructure of the welded joint has been evaluated for as-welded and heat treatment conditions. The microstructure studies revealed the formation of an unmixed zone (UZ) close to the fusion line, and it was characterized as peninsula and island. The WFZ showed the complete austenitic mode of the solidification and revealed the austenitic structure with cellular and equiaxed grains in the center of the weld metal. The columnar and cellular dendrites were seen near the boat fusion line, i.e., interface of the weld metal and HAZ. The soft δ ferrite patches were observed near the fusion line in the area of HAZ and remain undissolved up to tempering temperature of 810 °C (PW 3). The dissolution of the ferrite patches was noticed for PW 4. The maximum and minimum tensile strength of the welds joint was measured 731 MPa and 502 MPa for PW 3 and PW 2, respectively. A uniform hardness variation in the transverse direction of the welded joint was observed for PW 3 and PW 4 conditions. The optimum combination of strength and ductility was obtained for the PW 3 condition.

中文翻译：

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异种IN617镍合金在P91焊接接头的组织和力学行为中的作用

本文研究了P91钢焊缝的冶金行为和力学性能。耐热P91钢的接头采用不同的Inconel等级617填料通过钨极氩弧焊（GTAW）工艺进行焊接。P91焊接接头在650–810°C的温度范围内经受了2 h的不同热处理方式。还对焊接接头进行了基于正火的回火。利用光学显微镜和扫描电子显微镜（SEM）对具有奥氏体结构的焊缝熔合区（WFZ）和具有马氏体结构的热影响区（HAZs）进行了表征。还针对焊后和焊后热处理（PWHT）条件对焊接金属和HAZ界面进行了详细的表征。对于焊缝的机械性能，进行拉伸测试和硬度测试。对于焊接条件和热处理条件，已评估了机械性能与焊接接头微观结构之间的关系。微观结构研究表明，在熔合线附近形成了一个非混合区（UZ），其特征是半岛和岛屿。WFZ显示出完全的奥氏体凝固模式，并揭示了在焊缝金属中心具有蜂窝状和等轴晶粒的奥氏体结构。在船形熔合线附近即焊缝金属和HAZ的界面附近可以看到柱状和蜂窝状的树枝状晶体。在热影响区附近的熔合线附近观察到了软δ铁素体斑块，直至回火温度为810°C（PW 3）时仍未溶解。在PW 4中注意到铁素体块的溶解。对于PW 3和PW 2，测得的焊接接头的最大和最小拉伸强度分别为731 MPa和502 MPa。对于PW 3和PW 4条件，在焊接接头的横向上观察到均匀的硬度变化。对于PW 3条件，获得了强度和延展性的最佳组合。