1. Peng DeQuan*, Wang Hui, Hu Yong, Zhang BaoLiang
The effect of oxygen and hydrogen on stress corrosion cracking of 304NG stainless steel in high temperature water with trace chloride ion for PWR primary loop
Peng DeQuan*, Wang Hui, Hu Yong, Zhang BaoLiang
(China Institute of atomic energy, P.O. Box , Beijing , China)
Phone: ,
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2. Outline
Background
Experimental
Results and discusion
Conclusion

3. Background
Stress corrosion cracking (SCC) susceptibility of stainless steel Chinese 304NG in deoxygenized, air-saturated, oxygenated and reductive hydrogen atmosphere with trace chloride ion was studied using slow strain rate testing (SSRT), the basic water chemistry is simulated the primary loop of pressurized water reactor (PWR) where high temperature and high pressure water contains boric and lithium ions.

4. Chemical composition of materials 304NG
Element C Si S Mn P Ni Cr N Cu Co Fe
concentration（wt%）
0.024
0.44
0.0016
1.48
0.021
9.68
19.43
0.11
0.081
0.054
Bal.
Fig 1 Sketch of 304NG specimen for slow strain rate testing

5. Experimtal conditions
Specimen
T/℃
O2(mg/L)
Cl-(mg/L)
H2(MPa)
Solution
BLi
300
0.02 -
1000mg/L B+2.2mg/L Li
Cl1 1
Cl2 2
O2BaoBLi 8
O2baoCl1
O2baoCl2
O2BLi
＞40
O2Cl1 --
O2Cl2
H2BLi
0.16
H2Cl1
H2Cl2
H2Cl5 5

6. Fig 2. Stress-strain curves of 304NG at different conditions in high pressure and high temperature water containing boric acid and lithium ions.

7. Table 3. Slow strain rate testing results of 304NG at 300℃ with different conditions
Specimen
Broken stress (f(kg/mm2)
Elongation E(%)
Broken time Tf(hour)
Yield stress (s(kg/mm2)
Max broken power (kg/mm)
Fracture type
IsccX
BLi
48.08
55.17
36.78
16.512
396.26 MF -
Cl1
47.925
54.84
36.56
15.172
401.75
0.6
Cl2
49.061
55.6
37.067
16.93
419.95
-0.78
O2BaoBLi
47.433
50.405
33.603
18.539
375.64
O2baoCl1
47.052
55.825
37.217
12.386
399.39
-10.8
O2baoCl2
49.594
54.925
36.617
15.92
418.41
-9.0
O2BLi
50.756
57.305
38.203
16.038
442.53
O2Cl1
49.725
52.575
35.05
16.323
389.84
8.3
O2Cl2
47.812
46.7
31.14
17.163
340.49
MF+TG
18.5
H2BLi
47.347
55.035
36.69
13.802
393.35
H2Cl1
44.528
51.99
34.66
12.15
338.07
5.5
H2Cl2
46.089
55.135
36.757
13.737
380.38
-0.18
H2Cl5
46.114
52.185
34.79
14.748
357.17
5.2
IsccX=(Tfi-Tfx)/Tfi*100%, Tfi-broken time of as-received samples, Tfx-broken time of samples at different chloride concentration. MF-Mechanical Fracture, TG-Transgranular Fracture.

8. Fig 3，Morphology of fractured specimens of 304NG after SSRT at oxygen or hydrogen chloride solution

9. Fig 4. Fractography and EDX spectrum of fractured O2BaoBLi specimen
Table 4. The chemical composition of air-saturated oxygen sample at edge zone and center area (atomic percentage, at%)
Position
At%O
At%Si
At%Cr
At%Mn
At%Fe
At%Ni B
5.75
1.19
20.06
1.75
63.02
8.22 D
11.73
1.0
20.37
1.82
58.35
6.72

10. Fig 5. Fractography and EDX spectrum of fractured O2BLi specimen
Position
O(at%) C
3.22 E
4.05

11. Position O Si Cr Mn Fe Ni C 3.22 0.82 21.33 2.01 63.94 8.68 E 4.05
Table 5. The chemical composition of oxygenated sample at edge zone and center area as for (atomic percentage, at%)
Position O Si Cr Mn Fe Ni C
3.22
0.82
21.33
2.01
63.94
8.68 E
4.05
0.71
20.72
62.99
9.51

12. Conclusion
Results showed the SCC susceptibility of 304NG increased with the order of air-saturated, deoxygenized, hydrogen charging and oxygenated. The tensile property of specimen with oxygenated was much better than that of air-saturated without chloride ion. The chemical analysis on fractography of tested samples showed that the oxygen content of oxygenated specimen was much lower than that of air-saturated specimen. The compact oxide film was formed on the surface of oxygenated sample, which prevent the dissolution of substrate metal. The compact oxide film could not form on the surface of air-saturated sample. If the trace chloride ion was doped in solution, the compact oxide film was destroyed, the synergy effect of chloride and oxygen was much more evident than the protective effect of oxide film, the SCC susceptibility of oxygenated sample was much higher than that of air-saturated sample.

13. Acknowledgement
Chinese national major projects funded project 2011ZX , 2011ZX and nuclear energy development projects funded HK • DG

14. Thank you !