1 Journées d ’Automne 2001 Structural Materials for Hybrid System Paris, 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, Gif-Sur- Yvette CEDEX. Effects of spallation products Ti, P and S on the physical metallurgy of 9Cr martensitic steels

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 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 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 EM10Ti (9Cr 1Mo 0.1C 0.17Ti)

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7 Tn =1250 °C/20min TiN

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

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

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

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 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 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 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 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 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 Impact properties (Sub-size specimens 3x4x27 mm)

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

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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