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Optimizing δ-ferrite structure to enhance high-temperature elongation in ER308L stainless steel deposited metal

Cong Jiang

Cong Jiang

CISRI Welding Institute, Central Iron and Steel Research InstituteBeijing 10081, China
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Jiang, Cong
, 
Yanchang Qi

Yanchang Qi

CISRI Welding Institute, Central Iron and Steel Research InstituteBeijing 10081, China
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Qi, Yanchang
, 
ZiXin Xu

ZiXin Xu

CISRI Welding Institute, Central Iron and Steel Research InstituteBeijing 10081, China
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Xu, ZiXin
, 
Guangchang Yang

Guangchang Yang

CISRI Welding Institute, Central Iron and Steel Research InstituteBeijing 10081, China
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Yang, Guangchang
 and 
Chengyong Ma

Chengyong Ma

CISRI Welding Institute, Central Iron and Steel Research InstituteBeijing 10081, China
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Ma, Chengyong
  
Jun 30, 2025
Optimizing δ-ferrite structure to enhance high-temperature elongation in ER308L stainless steel deposited metal's Cover Image
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Article Category: Research Article
Published Online: Jun 30, 2025
Page range: 52 - 62
Received: Jan 13, 2025
Accepted: Apr 11, 2025
DOI: https://doi.org/10.2478/msp-2025-0018
Keywords
© 2025 Cong Jiang, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Figure 1

From ferrite content to morphology control: A 350°C-ready pathway for nuclear-grade ER308L weld.
From ferrite content to morphology control: A 350°C-ready pathway for nuclear-grade ER308L weld.

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.
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.

Figure 3

Metallographic microstructures of the deposited metals: (a) No. 1, (b) No. 2, and (c) No. 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.
SEM morphology and EDS analysis of δ-ferrite in deposited metals: (a–c) No. 1, (d–f) No. 2, and (g–i) No. 3.

Figure 5

Stress–strain curves of deposited metals: (a) room temperature and (b) 350°C.
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.
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.
SEM results of high-temperature stretching fracture profile: (a–c) No. 1, (d–f) No. 2, and (g–i) No. 3.

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

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

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

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

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
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