Konys, J.

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KIT – University of the State of Baden-Wuerttemberg and  National Research Center of the Helmholtz Association INSTITUTE  FOR  APPLIED MATERIALS  RESEARCH –  MATERIAL PROCESS TECHNOLOGY  |   CORROSION  DEPARTEMENT www.kit.edu Advanced Processes for T-Permeation and Corrosion Barriers for the DCLLmod. concept J. Konys, W. Krauss, N. Holstein, S.-E. Wulf 2 Advanced processes for T-permeation and corrosion barriers Outline  T-permeation and/or anti-corrosion barriers for the DCLLmod. blanket  in ITER (and for DEMO?)   why Al-based barriers?  Overview of previous coating activities  New electrochemical Al coating processes  - ECA, Al deposition from organic aprotic electrolyte  - ECX (X = Al, W, Ta …), deposition from ionic liquid + metal salt  Conclusions 1st EU-US DCLL Workshop   |  April 23-24, 2013  |  KIT-CN, Karlsruhe, Germany                                                                                                        Jürgen Konys 3 OUT IN DEMO HCLL MAIN FEATURES 2m x 2m modules RAFM steel (EUROFER) He (8 MPa, 300-500°C) Liquid Pb-15.7Li (eutectic)  as breeder and multiplier PbLi slowly re-circulating (10/50 rec/day) 90% 6Li in PbLi  Pb-Li velocities  in breeding unit ~ 1 cm/s range TBR = ≤1.15 with 550mm Breeder radial depth Lifetime 7.5 MWy/m2  PbLi flow  velocity   ~ 1 mm/s  Corrosion of cooling and stiffening plates by PbLi and permeation of tritium from PbLi into He gas  The HCLL (He-PbLi) TBM (and DEMO) blanket Application of T-permeation and/or anti-corrosion barriers Pb-15.7Li   G. Rampal, HCLL TBM 2008 1st EU-US DCLL Workshop   |  April 23-24, 2013  |  KIT-CN, Karlsruhe, Germany                                                                                                        Jürgen Konys 4 Safety and cost  Its to reduce the tritium release from the PbLi into the coolant significantly (water for WCLL and helium for DCLLmod. blanket concept)   limit for ITER site 1gT/a            EU Fusion Technology program started to select FeAl-based coatings with alumina as a thin top layer in the mid 90’s. Later on, other type of coatings were also investigated, but with much less intensity and less claim for industrial relevance (ca. 2007+).    During the phases one and two of the European R&D process, the manufacturing technologies for the coatings and their technical characterization were summarized in reports between 1998 and 2003.  Why do we need TPB’s (Tritium Permeation Barriers) for Liquid Breeder Concepts?  1st EU-US DCLL Workshop   |  April 23-24, 2013  |  KIT-CN, Karlsruhe, Germany                                                                                                        Jürgen Konys 5 Requirements for a tritium permeation barrier Reduction of T-permeation by a factor  of <100 in Pb-15.7Li (1000 in gas phase) Self-healing of (mechanically) damaged layer must be thermodynamically possible in       Pb-15.7Li (re-oxidizing) Long-term corrosion resistant in Pb-15.7Li  up to ca. 550°C High content of low activation elements No negative influence on mechanical  properties of the steel due to the coating process The coating process must be of industrial relevance  Structure and technical requirements for an Al-based T-permeation barrier Al2O3 (ca. 0.5 - 2 µm) Fe(Cr, Al)-phase (10 – 100 µm) FM-steel e. g. EUROFER 1st EU-US DCLL Workshop   |  April 23-24, 2013  |  KIT-CN, Karlsruhe, Germany                                                                                                        Jürgen Konys 6 Thermodynamics of Al/Al2O3-based T-permeation barriers Stability of oxides 1st EU-US DCLL Workshop   |  April 23-24, 2013  |  KIT-CN, Karlsruhe, Germany                                                                                                        Jürgen Konys 7 Electro-chemistry for coating application EC measurements of protic and aprotic metal deposition systems 1st EU-US DCLL Workshop   |  April 23-24, 2013  |  KIT-CN, Karlsruhe, Germany                                                                                                        Jürgen Konys 8 Solvens Toluol, Xylol Diisopropylether Quarternay Amin salts e. g. Ethylmidazolium chloride Ionic solubility of solvens No Yes Al-carrier system KF⋅2Al(R)3  R = CnH2n+1 mit n= 2-6 AlCl3 Temperature 100°C RT … 200°C Reactivity Water extremly high modest Air extremly high low Temperature modest Stable up to 300°C Toxicology | biodegrability Aromates: ++/--- Amines: -/+ Max. conductivity [mS/cm] 19,5 22,0 ECA ECX Al-Alkyl- Acryl-Complex in Toluol resp. Alkylether Al3+ + 3 Cl- →  EMIM-AlCl4  AlAlKKF+N NRX-+Electrochemical aluminium deposition - properties of organic aprotic electrolyte systems - 1st EU-US DCLL Workshop   |  April 23-24, 2013  |  KIT-CN, Karlsruhe, Germany                                                                                                        Jürgen Konys 9 ca. 20 µm ca. 5 µm Eurofer97 + Al galv. Reduced Al thickness  + Rough surface from turning ca. 50 µm Eurofer 97 + 20 µm Al galv. Heat treatment : 960°C 0.5h; 760°C 1.5h Al-enriched zone Process specifics Organic electrolyte, Al-alkyle, under cover gas Deposition temperature ca. 100°C, rate ≈ 12 µ/h More complex geometries can be coated; even inside tubes   Result of ECA development   Electrochemical coating applicable to functional scales in TBM’s   Barrier function tested in corrosion, successfully   Salt-based processes have to be developed for higher compositional flexibility   Reason: Electro-negativity of refractory metals and unique behavior Development of electrochemical Al coating  process (ECA) 1st EU-US DCLL Workshop   |  April 23-24, 2013  |  KIT-CN, Karlsruhe, Germany                                                                                                        Jürgen Konys 10 Ionic liquids as electrolytes Structure like ionic salts (similar to solid ionic crystals: e. g. NaCl), 100% ionic No additional solvent is necessary Mostly liquid at “room temperature” (≤ 100°C)  Major properties  Thermally very stable (> 300°C)  low vapor pressure  Not flammable  High variability of chemical structure  Good miscibility with inorganic metal salts as “carriers” for metal deposition, e.g. AlCl3  High electrical conductivity  Electrochemically very stable against oxidation and/or reduction  High bio-compatibility  IL‘s are superior for use for electrochemical Al deposition  Development of electrochemical  Al coating process (ECX, X=Al, W, Ta…) - Ionic liquids (IL’s) + metal salts as new advanced electrolytes -    1st EU-US DCLL Workshop   |  April 23-24, 2013  |  KIT-CN, Karlsruhe, Germany                                                                                                        Jürgen Konys 11  The use of AlCl3:[Emim]Cl (1,5:1, Lewis acidic ) ionic liquids (ILs) as electrolyte for Al-electrodeposition provides advantages in comparison to Lewis basic or neutral electrolytes Increased electrochemical stability during electrodeposition Commercially available: constant composition and quality, available in great quantities  Industrial relevance is given ECX process provides better flexibility than ECA process Adjustable deposition parameters: current density, temperature, pulse plating        possible, … Adjustable Al coating properties (morphology, deposition rate, …) Constant current jmean = 20 mA/cm², 30min Pulse current  jmean = 20 mA/cm², 30min Development of coatings for corrosion / T-permeation barriers  Development of electrochemical Al coating process based on ionic liquids  (ECX process)  1st EU-US DCLL Workshop   |  April 23-24, 2013  |  KIT-CN, Karlsruhe, Germany                                                                                                        Jürgen Konys 12 Development of electrochemical aluminium coating process (ECX) SEM image – surface structure   Good adhesion of the coating to Eurofer substrate: depends on pre-treatment of the sample No delamination of layers during cutting process Eurofer   Al layer SEM image – cross section – center  Al layer Eurofer   SEM image – cross section – left edge   Deposition rates up to 25 µm/h, depending on current density Smooth surface in the center of the sample, at the edges even higher layer thicknesses, due to current density focusing 1st EU-US DCLL Workshop   |  April 23-24, 2013  |  KIT-CN, Karlsruhe, Germany                                                                                                        Jürgen Konys 13 Heat treatment of Al layers for corrosion / T-permeation barriers Treatment of Al coatings produced by EDX process (Lewis acidic IL) Actual work: Ongoing examination of deposition parameters: Adhesion to the substrate, reproducibility, influence on coating properties Influence of sample geometry Optimization of heat treatment parameters (depending on parameters during ECX process) before heat treatment:  approx. 8µm Al Heat treatment under Ar atmosphere (preventing of strong surface oxidation) + additional annealing step at 640°C (4h) Relatively smooth surface after heat treatment  Layer thickness after heat treatment: approx. 50µm (center)  Eurofer α-Fe after heat treatment: 4h 640°C, 0.5 h 980°C, 1.5h 760°C α-Fe (0-12 at.% Al) Eurofer  1st EU-US DCLL Workshop   |  April 23-24, 2013  |  KIT-CN, Karlsruhe, Germany                                                                                                        Jürgen Konys 14 Conclusion and outlook    Barriers on Eurofer steel structures, based on Fe-Al/Al2O3, are appropriate to fulfill the requirements for T-permeation reduction and corrosion protection in PbLi operated systems, including DCLLmod. blankets.  Electrochemical deposition process ECX has shown its appropriate-ness for manufacturing of thin Al-based coatings with high repro-ducibility. The development of suitable heat treatment sequences to form the outermost alumina layer has been successful, too.  Qualification outstanding concerning corrosion stability, T-permeation, thermal cycling and irradiation  Development towards real application necessary under ITER TBM  Transfer to DCLLmod.?  1st EU-US DCLL Workshop   |  April 23-24, 2013  |  KIT-CN, Karlsruhe, Germany                                                                                                        Jürgen Konys 

Advanced processes for T-permeation and corrosion barriers for the DCLLsub(m)ₒsub(d)̣ concept

https://publikationen.bibliothek.kit.edu/230091244/3816277

Advanced processes for T-permeation and corrosion barriers for the DCLLsub(m)ₒsub(d)̣ concept

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