Dissimilar 9% Cr heat-resistant steels (G115 and CB2) with good creep properties for ultra-supercritical steam turbines were butt-joined by tungsten inert gas welding. The microstructure of welded metal (WM) was quenched martensite without carbide precipitates and lath packets existed inside prior austenite grains (PAGs), which leaded to higher hardness of WM. Partially melted zone at G115 side was composed of untempered martensite within equiaxed PAGs. The lowest hardness occurred in both G115 and CB2 steels which was attributed to tempered martensite with many M₂₃C₆ precipitates. The heat-affected zone consisted of three sub-grains and their microstructure was detailly analyzed in current work. As current increased from 130 to 150 A, both the tensile strength at room temperature and 650 ℃ increased while strength had no obvious change with further increasing current. The values of 673 MPa and 309 MPa corresponded to the tensile stress with 150 A at room temperature and 650 ℃, respectively. The fracture mode of joints at room temperature was cleavage and ductile failure at 130 and 150 A, respectively. The high-temperature fracture surface at 150 A was composed of deep and fine dimples.

用于超超临界蒸汽轮机的具有良好蠕变性能的不同9％Cr耐热钢（G115和CB2）通过钨极惰性气体保护焊对接。焊接金属（WM）的显微组织是淬火的马氏体，没有碳化物沉淀，板条包存在于先前的奥氏体晶粒（PAG）中，从而导致WM的硬度更高。G115侧的部分熔化区由等轴PAG内的未回火马氏体组成。最低的硬度出现在G115和CB2钢中，这归因于回火马氏体和许多M ₂₃ C ₆沉淀。热影响区由三个亚晶粒组成，并在当前工作中详细分析了它们的微观结构。当电流从130 A增加到150 A时，室温和650℃时的抗拉强度均增加，而强度随着电流的增加而无明显变化。673 MPa和309 MPa分别对应于室温和650℃下150 A的拉伸应力。在室温下，接头的断裂模式分别是在130和150 A下发生劈裂和延性破坏。150 A时的高温断口表面由深而细的凹坑组成。