Sanicro 25 is a candidate material for reheaters and superheaters used in 650–700 °C advanced ultra-supercritical power plants. A composition-matched weld filler metal has been developed to join Sanicro 25 tubes through tungsten inert gas welding. Creep tests of the Sanicro 25 welded joint were conducted at 973 K under a stress of 180–240 MPa. The creep lifetime decreased with an increase in applied stress. The welded joint crept at 180 MPa fracture at the base metal (BM) in a mixed fracture type, and voids were the main damage form in the BM, which had low ductility in the welded joint. Creep fractures occurred in the weld metal (WM) in an intergranular manner at 200–240 MPa, with wedge cracks representing the main damage form and a lower creep ductility in WM. The distribution and strengthening mechanism of the nano-MX and nano-Cu phases in the WM of joint were close to those of pure BM after creep. The growth of carbides in the WM was restrained by element B during the 180 MPa creep test, which caused increasingly serious carbide coarsening in the BM. The amount of low misorientation angle boundaries in the WM following the creep substantially increased. Besides, the creep deformation of the welded joint at 180 MPa is dominated by BM, and the change in the weld grain shape is small. For tests under 200–240 MPa, the creep deformation of the welded joint was dominated by the weld, and the shape of the weld grain changed significantly.

中文翻译：

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外加应力对由成分匹配的焊接填充金属制成的 Sanicro 25 焊接接头蠕变性能的影响

Sanicro 25 是用于 650–700 °C 先进超超临界电厂的再热器和过热器的候选材料。已开发出一种成分匹配的焊接填充金属，通过钨极惰性气体保护焊将 Sanicro 25 管连接起来。Sanicro 25 焊接接头的蠕变试验在 973 K 和 180-240 MPa 的应力下进行。蠕变寿命随着外加应力的增加而降低。焊接接头在母材（BM）处以 180 MPa 蠕变断裂为混合断裂类型，空洞是 BM 的主要损伤形式，焊接接头的延展性较低。在 200-240 MPa 下，焊缝金属 (WM) 以晶间方式发生蠕变断裂，楔形裂纹代表主要损伤形式，WM 中的蠕变延展性较低。蠕变后纳米MX和纳米Cu相在接头WM中的分布和强化机制与纯BM相接近。在 180 MPa 蠕变试验期间，WM 中碳化物的生长受到元素 B 的抑制，导致 BM 中碳化物粗化日益严重。蠕变后 WM 中低取向角边界的数量显着增加。此外，焊接接头在180 MPa下的蠕变变形以BM为主，焊缝晶粒形状变化较小。200～240 MPa试验中，焊接接头蠕变变形以焊缝为主，焊缝晶粒形状发生明显变化。导致BM中碳化物粗化日益严重。蠕变后 WM 中低取向角边界的数量显着增加。此外，焊接接头在180 MPa下的蠕变变形以BM为主，焊缝晶粒形状变化较小。200～240 MPa试验中，焊接接头蠕变变形以焊缝为主，焊缝晶粒形状发生明显变化。导致BM中碳化物粗化日益严重。蠕变后 WM 中低取向角边界的数量显着增加。此外，焊接接头在180 MPa下的蠕变变形以BM为主，焊缝晶粒形状变化较小。200～240 MPa试验中，焊接接头蠕变变形以焊缝为主，焊缝晶粒形状发生明显变化。