Effect of Cold Working Effect of Cold Working on the Corrosion - PowerPoint PPT Presentation

Effect of Cold Working Effect of Cold Working on the Corrosion Resistance of JPCA Steel on the Corrosion Resistance of JPCA Steel in Flowing Pb-Bi at 450ºC in Flowing Pb-Bi at 450ºC Abu Khalid Rivai , Shigeru Saito, Obayashi Hironari, Masao Tezuka, Chiaki Kato, Kenji Kikuchi JAEA - Japan Atomic Energy Agency 1 IWSMT10, Beijing-China, October 18-22, 2010

Outline � Motivation Concept � Purpose � Experiment and Procedure � Results & Discussion � Conclusions 2

Motivation Concept LBE (Pb-Bi eutectic) is the candidate for ADS (Accelerator Driven System) spallation target and core coolant (JAEA`s design). Materials Issues: Developing Solutions: 1.Corrosion attack 1. JPCA steel: the candidate material of Pb-Bi to metals. for the proton beam window. 2.Hydrostatic pressure of Pb-Bi. 2. Cold worked-JPCA steel: 3.Protons expected to be bombardment to stronger to endure beam window. protons bombardment and Pb-Bi`s pressure. Scale: mm LBE 3

Motivation Concept Cold working Strengthening of a metal by plastic deformation Cold work 20% Cold worked-JPCA JPCA (without cold working) Slip/deformation bands Cold working (austenitic steel) process induces: 1. Increasing the strength and hardness. 2. Dislocation movement within the crystal. 3. Transformation from fcc austinite ( γ ) to bcc martensite ( α `, magnetic ). 4

Purpose To investigate the effect of cold working on the corrosion resistance of JPCA steel in flowing Pb-Bi at 450ºC of temperature and 1 m/s of flow velocity. Weld part Weld part Proton Proton beam window LBE temp. and flow velocity: ~450ºC and 1 m/s LBE ADS 5

Experimental & Procedure Parameter Conditions Type of liquid LBE (Pb-Bi eutectic) Flow velocity (m/s) 1 Temp. of hot and cold part ( ⁰ C) 450 and 350 Oxygen concentration (wt.%) ~10 -8 - ~10 -9 Time immersion (hrs) 1000 20% Cold worked (CW)-JPCA Materials No CW-JPCA (as comparison) JPCA-Chemical Compositions (wt.%) Fe Ni Cr Mo Mn Si Ti C B P Co S N Balance 15.50 14.50 2.50 1.50 0.50 0.25 0.055 0.004 <0.035 <0.02 <0.01 <0.01 6

Experimental & Procedure -100 (1/3) Bi 2 O 3 10 -3 -150 10 -4 PbO 10 -5 NiO 10 -6 -200 H 2 O 10 -7 oxygen , Δ G o 10 -8 (1/4) Fe 3 O 4 Oxygen concentration: -250 10 -9 Δ G ~10 -8 - ~10 -9 wt.% -300 (1/3) Cr 2 O 3 -350 -400 450 ⁰ C 200 300 400 500 600 700 Temperature (ºC) Δ G oxygen , Oxygen potential in LBE Δ G o , Oxygen potential of oxides 7

Experimental Apparatus JLBL-1 ( J AEA L ead- B ismuth L oop for material corrosion) 450ºC, 1 m/s 20%CW-JPCA No CW-JPCA 420 mm 8 TIG welds

Results & Discussions 9

Results: SEM-EDS 20%CW-JPCA JPCA (no CW) 1 Adhered Pb-Bi Adhered Pb-Bi Adhered Pb-Bi Adhered Pb-Bi Adhered Pb-Bi 1 1 Oxide layer ? 2 3 2 2 4 3 4 3 4 5 A layer? A layer? 6 5 6 5 6 Pb-Bi A layer? Pitting 7 Pb-Bi Pb-Bi 7 7 penetration 8 penetration penetration 8 8 Bulk Bulk Bulk Bulk 10µm 1µm 9 1µm 10µm 1µm 9 9 10 100 100 Fe Cr Ni O Pb Bi Fe Cr Ni O Pb Bi 90 90 80 Ferrite layer LBE penetration 80 Fe-Cr oxide Weight ( %) 70 Weight ( %) 70 60 60 50 50 40 40 30 30 20 20 10 10 0 0 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 10 Analysis point Analysis point 10

Results: EDS (mapping) 20%CW-JPCA JPCA (no CW) Pb Bi Fe Cr 3.0 3. 0 µm Pb Pb M M 3.0 3. 0 µm Bi M Bi M 3.0 3. 0 µm Fe Fe K K 3.0 3. 0 µm Cr K Cr K Fe Fe-Pb-Bi Adhered LBE Pb Bi Pb-Bi Fe LBE Fe 3. 3.0 0 µm Fe Fe K K 3. 3.0 µ 0 µm 3.0 3. 0 µm Pb M Pb M 3.0 3. 0 µm Bi Bi M M Cr Cr-Pb-Bi Adhered LBE Cr Pb-Bi O LBE Cr 3.0 µ 3. 0 µm Cr K Cr K 3. 3.0 µ 0 µm Ni-Pb-Bi Ni Adhered LBE Ni 3. 3.0 0 µm O K O K Pb-Bi 5. 5.0 µ µm Fe-Cr-O LBE Ni 3. 3.0 0 µm Ni Ni K K 3. 3.0 µ 0 µm 11

Results: XRD JPCA (no CW) 20%CW-JPCA 1400 1200 α : Austenite α : Austenite α 1200 β : Fe-Cr b: Pb-Bi oxide 1000 γ : (Fe-Cr) oxide α 1000 800 δ : Pb-Bi oxide Intensity Intensity α 800 α 600 α 600 400 β 400 α γ γ α δ γ α γ γ g γ γ α α 200 δ γ γ δ α δ α ββ ββ γ δ γ 200 γ δ α α γ β β δ δ γγ δ γ β β β β δ β α γ γ β β δ β 0 0 20 30 40 50 60 70 80 90 100 110 120 20 30 40 50 60 70 80 90 100 110 120 Diffraction angle (2 θ ) Diffraction angle (2 θ ) 12

Results: AFM - KFM* 20%CW-JPCA JPCA (no CW) F e r r i t e l a y e r Adhered Pb-Bi Adhered Pb-Bi Pitting area Pb-Bi penetration Bulk Bulk μ μ m m *Alternating voltage is applied to a conductive cantilever. The electromagnetic forces acting between the sample surface and the cantilever are detected to measure the potential across the sample surface. 13

Results: AFM - KFM JPCA (no CW) 20%CW-JPCA Adhered Adhered Pb-Bi Pb-Bi Bulk Bulk 14

Results: AFM – MFM* 20%CW-JPCA JPCA (no CW) 100x100 µm 100x100 µm 100x100 µm Magnetic bands 50x50 µm 50x50 µm 50x50 µm Magnetic bands *A magnetized probe is scanned at a constant distance from the sample surface. Magnetic forces due to the leakage field are detected and magnetic information about the sample surface is displayed visually. 15

Discussion: Effect of Cold Working 20% Cold worked-JPCA JPCA (without cold working) Slip/deformation bands * 16 *Porter DA, Easterling KE, “Phase transformations in metals and alloys” , 2nd edition: Chapman & Hall, London, 1993.

Summary Corrosion behavior of 20%CW- JPCA and SA-JPCA in flowing Pb-Bi at 450ºC for 1000 hours Parameter 20% CW–JPCA No CW–JPCA Ferritization - � . Oxide layer � . - � . Pitting - (localized) � . Penetration of Pb-Bi � . (localized) 17

Conclusion � In the present study, superficial ferritization accompanied with penetration of Pb-Bi through the ferrite layer occurred for JPCA without cold working. � On the other hand, dissolution attack occurred only partially (localized superficial pitting) for the 20% cold worked-JPCA steel with no ferritization observed. Therefore, cold working limited a dissolution attack from flowing Pb-Bi. However, for the beam window material application the pitting corrosion problem has to be solved. 18

9