1. 1 Journées d ’Automne 2001 Structural Materials for Hybrid System Paris, 29-31 octobre 2001 O. Danylova 1, Y. de Carlan 2, D. Hamon 2, J-C. Brachet 2, J. Henry 2, A. Alamo 2 1 Centre de recherche d’Imphy 2 CEA Saclay, Service de Recherches Métallurgiques Appliquées, 91 191 Gif-Sur- Yvette CEDEX. Effects of spallation products Ti, P and S on the physical metallurgy of 9Cr martensitic steels

2. 2 Preliminary calculations of quantities of spallation products created in the window (J. Henry, C. Volant, R. Legrain) Embrittlement of the material ? - Segregation at interfaces ? - Formation of sulphides and phosphides ? Formation of hydrides, sulphides...?

3. 3 Experimental heats to study the effects of Ti, P, S on the metallurgical and mechanical properties Aim of the study : To obtain 9Cr martensitic steels by conventional elaboration with (Ti, S, P) in solid solution to determine mechanical and cleavage properties

4. 4 Phase stability fields in Fe 9Cr 1Mo 0.1C martensitic steels Calculations at the thermodynamic equilibrium Software MTdata with data bases : Plus and Sub_sgte

5. 5 EM10Ti (9Cr 1Mo 0.1C 0.17Ti)

6. 6

7. 7 Tn =1250 °C/20min TiN

8. 8 Ti(N,C) Ti(Mo)C TiN TiC ferrite a) b) Globular particles Ti(Mo)C EM10Ti (9Cr 1Mo 0.1C 0.17Ti) Steel normalised at 1200 °C/30min and quenched

9. 9 EM10Ti (9Cr 1Mo 0.1C 0.17Ti) Concentration profiles (obtained with a micro probe analyser) of Cr, Mo, Si and Ti within the matrix of the steel normalised at 1150°C/ 30 min. Ti is in solid solution.

10. 10 EM10 LMnS (9Cr 1Mo 0.1C LMn 0.04S)

11. 11 EM10 LMnS (9Cr 1Mo 0.1C LMn 0.04S)

12. 12 EM10 LMnS (9Cr 1Mo 0.1C LMn 0.04S) T n = 1350°C / 20min The proportions of austenite and ferrite as a function of temperature are close to those observed in the EM10 standard steel. A strong modification of the repartition of chromium sulphides is observed as a function of heat treatment (at 1350°C, probably dissolution and reprecipitation of chromium sulphides).

13. 13 Concentration profiles (micro probe analyser) of S and Mo within the matrix of the steel (normalised at 1300°C and quench at 100 °C/s). EM10 LMnS (9Cr 1Mo 0.1C LMn 0.04S)

14. 14 EM10 LMnS (9Cr 1Mo 0.1C LMn 0.04S) 100 nm TEM examinations show small chromium sulphides (chemical composition close to 50% Cr and 50% S with a small amount of Fe) => solubility of S is very low (close to 10 ppm at 1100 °C, according literature)

15. 15 EM10TiPS (9Cr 1Mo 0.1C 0.2Ti 0.03P 0.04S)

16. 16 EM10TiPS (9Cr 1Mo 0.1C 0.2Ti 0.03P 0.04S) Calculations with the software Thermocalc predict also the formation of Ti 4 C 2 S 2

17. 17 EM10TiPS (9Cr 1Mo 0.1C 0.2Ti 0.03P 0.04S) Ferritic Zones Alignments of Ti x S y Ti(N,C) Steel normalised at 1150°C/30min and quenched

18. 18 Ti(NC) Ti, Al, S Ti x S y Ti(NC) Ti, Al, S Ti x S y Ti, Al, S EM10TiPS (9Cr 1Mo 0.1C 0.2Ti 0.03P 0.04S) Steel normalised at 1150°C/30min and quenched

19. 19 EM10TiPS (9Cr 1Mo 0.1C 0.2Ti 0.03P 0.04S) Steel normalised at 1150°C/30min and quenched Phosphorus is probably in solid solution

20. 20 Conclusions 1) Better knowledge of the effects of Ti, S and P on the physical metallurgy of Fe 9Cr martensitic steels. 2) Assessment of heat treatments to obtain doping elements in solid solution in the different steels : - alloys doped with only Ti : after heat treatment, 1000 ppm can be retained in solid solution alloys doped with sulphur - alloys doped with sulphur : sulphides are very stable MnS, CrS, Ti(C,S) and it appears difficult to put it in solid solution even in a low manganese heat => very strong tendency of sulphur to precipitate. - alloy doped with phosphorus : possibility to have P in solid solution

21. 21 Alloys doped with titanium in solid solution : - possibility to perform mechanical tests and hydrogen loading to study the interactions between Ti and H. Alloy doped with phosphorus in solid solution (EM10 TiPS) : - possibility to study the evolution of microstructure after thermal ageing or step cooling - the steel contains many inclusions that limit the possibility to assess the influence of P on mechanical properties Alloys with sulphur : - check if sulphur segregation is detectable in the EM10LMnS steel after homogenisation at high temperature and step cooling. -Other specific experiments, like diffusion couple at 500 or 600°C, between FeS and a matrix Fe-9Cr (Ti, P) may be proposed. For all the alloys : study of the stability under irradiation of phases with doping elements. Perspectives

22. 22 Impact properties (Sub-size specimens 3x4x27 mm)

23. 23 EM10MnS (9Cr 1Mo 0.1C 0.5Mn 0.04S)

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25. 25

26. 26 EM10Ti (9Cr 1Mo 0.1C 0.17Ti) 10  m C K  10  m N K  10  m SE Ti K  10  m Courtesy of CAMECA