Figure 1
From ferrite content to morphology control: A 350°C-ready pathway for nuclear-grade ER308L weld.
Table 1
Chemical compositions of ER308L wire and base metal.
| Material | Elemental content (wt%) | ||||||
|---|---|---|---|---|---|---|---|
| C | Si | Mn | S | P | Cr | Ni | |
| 304L | 0.052 | 0.48 | 1.08 | <0.002 | 0.0390 | 18.23 | 8.39 |
| ER308L-1 | 0.016 | 0.36 | 1.50 | <0.002 | 0.0170 | 19.57 | 9.91 |
| ER308L-2 | 0.016 | 0.14 | 1.98 | 0.0007 | 0.0140 | 19.90 | 9.78 |
| ER308L-3 | 0.021 | 0.22 | 1.69 | 0.0120 | 0.0022 | 19.71 | 9.90 |
Table 2
Welding parameters.
| Test plate | Current (A) | Voltage (V) | Welding speed (cm/min) | Heat input (kJ/cm) | Shield gas | Gas flow rate (L/min) |
|---|---|---|---|---|---|---|
| No. 1 | 180–220 | 10–16 | 9 | 15 | 100% Ar | 10 |
| No. 2 | 180–220 | 10–16 | 17 | 11 | 100% Ar | 10 |
| No. 3 | 180–220 | 16–24 | 24 | 11 | 97% Ar + 3% N2 | 10 |
Figure 2
Schematic diagram of experimental material preparation: (a) Dimensions and specimen locations of the weldments. (b) Schematic representation of the deposition process. (c) Tensile specimen machining drawing. (d) Schematic diagram of the testing area of the FERITSCOPE FMP30 ferrite tester.
Table 3
Chemical composition of the molten metal (wt%), value of Creq, Nieq.
| Material | C | Si | Mn | S | P | Cr |
|---|---|---|---|---|---|---|
| No. 1 | 0.011 | 0.37 | 1.53 | 0.021 | 0.0090 | 19.54 |
| No. 2 | 0.012 | 0.16 | 1.92 | 0.014 | 0.0004 | 19.90 |
| No. 3 | 0.011 | 0.26 | 1.56 | 0.008 | 0.0020 | 19.57 |
| Material | Ni | Mo | N | Nieq | Creq | Creq/Nieq |
|---|---|---|---|---|---|---|
| No. 1 | 9.56 | 0.025 | 0.035 | 11.71 | 20.12 | 1.72 |
| No. 2 | 9.60 | 0.034 | 0.041 | 12.15 | 20.17 | 1.66 |
| No. 3 | 9.76 | 0.017 | 0.075 | 13.12 | 19.98 | 1.52 |
Table 4
Ferrite content of deposited metal.
| Deposited metal | Ferrite content (%) | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Based on the magnetic method | Based on the Delong plot | ||||||||
| Site | 1 | 2 | 3 | 4 | 5 | Average | Average | Calculated value | |
| No. 1 | 1 | 12.4 | 12.5 | 11.0 | 11.5 | 9.5 | 11.4 | 11.6 ± 1.0 | 10.2 |
| 2 | 10.2 | 11.8 | 11.5 | 11.8 | 10.7 | 11.2 | |||
| 3 | 11.2 | 12.1 | 11.4 | 11.6 | 11.0 | 11.5 | |||
| 4 | 11.9 | 11.7 | 11.6 | 11.5 | 10.6 | 11.5 | |||
| 5 | 11.9 | 11.7 | 11.5 | 11.5 | 11.1 | 11.5 | |||
| 6 | 11.5 | 13.5 | 13.7 | 13.8 | 10.5 | 12.6 | |||
| No. 2 | 1 | 10.5 | 10.1 | 10.4 | 10.7 | 11.0 | 10.5 | 9.8 ± 0.7 | 9.4 |
| 2 | 8.3 | 8.9 | 9.6 | 9.3 | 9.4 | 9.1 | |||
| 3 | 7.7 | 9.0 | 10.5 | 10.1 | 9.4 | 9.3 | |||
| 4 | 7.9 | 9.4 | 10.6 | 9.7 | 8.9 | 9.3 | |||
| 5 | 10.0 | 9.6 | 9.9 | 10.0 | 9.4 | 9.8 | |||
| 6 | 10.4 | 10.5 | 10.1 | 11.0 | 10.4 | 10.5 | |||
| No. 3 | 1 | 6.8 | 7.0 | 6.5 | 7.7 | 7.0 | 7.0 | 7.4 ± 0.6 | 6.2 |
| 2 | 7.1 | 6.7 | 7.0 | 6.7 | 7.0 | 6.9 | |||
| 3 | 6.9 | 7.3 | 7.0 | 7.4 | 7.5 | 7.2 | |||
| 4 | 6.7 | 7.4 | 7.2 | 8.2 | 8.8 | 7.7 | |||
| 5 | 7.6 | 8.1 | 7.9 | 7.8 | 8.4 | 8.0 | |||
| 6 | 7.5 | 7.3 | 7.3 | 7.9 | 8.3 | 7.7 | |||
Figure 3
Metallographic microstructures of the deposited metals: (a) No. 1, (b) No. 2, and (c) No. 3.
Figure 4
SEM morphology and EDS analysis of δ-ferrite in deposited metals: (a–c) No. 1, (d–f) No. 2, and (g–i) No. 3.
Table 5
Room temperature and high-temperature tensile properties of the deposited metal.
| Temperature (°C) | Specimen | YS (MPa) | UTS (MPa) | Elongation (%) |
|---|---|---|---|---|
| 23 | No. 1 | 427 | 570 | 40.5 |
| No. 2 | 421 | 557 | 44.5 | |
| No. 3 | 403 | 561 | 40.5 | |
| 350 | No. 1 | 339 | 379 | 26 |
| No. 2 | 322 | 359 | 29 | |
| No. 3 | 284 | 371 | 32 |
Figure 5
Stress–strain curves of deposited metals: (a) room temperature and (b) 350°C.
Figure 6
High-temperature tensile fracture morphology of the deposited metal: (a–c) No. 1, (d–f) No. 2, and (g–i) No. 3.
Figure 7
SEM results of high-temperature stretching fracture profile: (a–c) No. 1, (d–f) No. 2, and (g–i) No. 3.