## 3 Results
### Microstructures
#### 3.4.3 Microstructure after Creep Rupture  
FZ of Inconel 625 and Haynes 230 Filler Specimens (Region 1 in Figure 6)  
After the creep deformation and high-temperature exposure, a significant amount of rod-shaped precipitations appeared in the FZ of the Inconel 625 filler weldment specimen, as shown in Figure 13a. The NBED pattern in Figure 13b indicated that it was the orthorhombic delta (\(\delta\)) phase. The \(\delta\) phase was enriched in Ni and Nb. Ni-, Nb-, and Ti-rich Laves particles, Si- and Mo-rich M\({}_{6}\)C, Cr- and Mn-rich M\({}_{23}\)C\({}_{6}\), and Ti-rich MC carbides were also observed. Figure 13c-e provides the NBED patterns of the observed Laves, M\({}_{23}\)Cr\({}_{6}\), and M\({}_{6}\)C phases; their sizes varied, reaching a maximum of 2 \(\upmu\)m. In contrast, the MC was smaller at less than 0.2 \(\upmu\)m (Figure 13j). Figure 11: As-welded FZ using Haynes 230 filler material showing the different carbides. (**a**,**e**) HAADF images. (**b–d**) ChemiSTEM EDX maps of Cr, Ti, and N indicating MC (Ti-rich) and M\({}_{23}\)C\({}_{6}\) (Cr-rich) carbides. (**f**–h**) ChemiSTEM EDX maps showing nano-sized W-, Mn-, and Cr-rich carbides. Note that their type was not identified because of the nano size. Figure 12: As-welded HAZ. (**a**) HAADF image. (**b–f**) ChemiSTEM EDX maps of Fe (**b**), Cr (**c**), N (**d**), Ti (**e**), and C (**f**). In the FZ of the Haynes 230 filler material WM specimen, significant amounts of SSPs were also observed in the microstructure but no \(\delta\) or Laves phase was observed. The principal precipitations are carbide phases. Figure 14 shows an HAADF image (a), NBED patterns (b,c), and ChemiSTEM element EDX maps (d-l). Figure 14d-l show Cr-rich M\({}_{23}\)C\({}_{6}\) carbides (d), Ti(C, N) (e), and W-, Mo-, Nb-, Si-, Ti-, and Al-rich M\({}_{6}\)C carbide (f-j). Figure 14: _Cont._  
Figure 13: FZ of Inconel 625 filler specimen after creep rupture (1091 h) at 760 \({}^{\circ}\)C and 80 MPa. (**a**) HAADF image showing the identified SSPs. (**b–e**) NBED patterns taken from the SSPs and matrix in (**a**): rod-shaped \(\delta\) phase at the zone axis of [100] and the parallel [110] zone axis of the matrix (**b**), HCP Laves phase at [1120] (**c**), M\({}_{23}\)C\({}_{6}\) carbide at [120] (**d**), M\({}_{6}\)C at [110] (**e**), and ChemiSTEM element EDX maps showing chemical compositions of the SSPs (**f–m**). HAZ Adjacent to Fusion Boundary (Region 2 in Figure 6)  
In the HAZ, the Ti(C, N) and Cr- and Mn-rich M\({}_{23}\)C\({}_{6}\) particles continued to precipitate during the creep test. Figure 15 provides the TEM bright field (a) and dark field (b,c) images and the electron diffraction patterns (d) showing the Ti(C, N) and M\({}_{23}\)C\({}_{6}\) carbides. Figure 15 shows the electron diffraction pattern taken close to [112] zone axis of the matrix and the reflections from Ti(C, N) and M\({}_{23}\)C\({}_{6}\). Note that the white arrowed diffraction spots are used to take the dark field images to show the FCC Ti(C, N) and FCC M\({}_{23}\)C\({}_{6}\) in Figure 15b,c. It can be seen that grain boundaries are the preferred locations for both Ti(C, N) and M\({}_{23}\)C\({}_{6}\) carbides. The Ti(C, N) carbides are smaller than the one of M\({}_{23}\)C\({}_{6}\), and they are distributed throughout the grain interiors (Figure 15b). The precipitated M\({}_{23}\)C\({}_{6}\) tend to be distributed adjacent to grain boundary and their amount gradually decreases towards the grain interiors (Figure 15c). Figure 14: FZ of Haynes 230 filler weldment after creep rupture for 1643 h at 760 \({}^{\circ}\)C and 80 MPa. (**a**) HAADF image. (**b,c**) NBED patterns taken at [110] zone axis from the M\({}_{6}\)C SSP (OI) and matrix (O2). (**d–l**) ChemiSTEM element EDX maps. Figure 15: TEM images showing the Ti(C, N) and M\({}_{23}\)C\({}_{6}\) carbides in the HAZ adjacent to the fusion boundary. (**a**) Bright field (BF) image. (**b**) Dark field (DF) image showing Ti(C, N) precipitates only. (**c**) DF image showing M\({}_{23}\)C\({}_{6}\) only in the microstructure.