Konys, J.

Schroer, C.

Skrypnik, A.

Tsisar, V.

Wedemeyer, O.

English

KITopen

12th International Workshop on Spallation Materials Technology19-23 October 2014, Bregenz, AustriaCorrosion response of 1.4970, 316L and 1.4571 austenitict l t fl i LBE ith 10 7 % di l ds ee s o ow ng w - mass sso ve oxygenat 400, 450 and 550°CINSTITUTE FOR APPLIED MATERIALS MATERIAL PROCESS TECHNOLOGY (IAM WPT)Valentyn Tsisar, Carsten Schroer, Olaf Wedemeyer, Aleksandr Skrypnik, Jürgen Konys    –    -KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association www.kit.eduIn-situ technology of Pb and Pb-Bi melt doping withoxygen in order to form the protective oxide layer on thef f t lsur ace o s eeDissolution Oxidation Severe oxidation316L T91 EP-823BASIS of Pb-Bi technologyC. Schroer (KIT-2014)Pb / Pb-Bi dissolvesand transports theoxygen;Components of steels(Si, Cr, Fe…) havehigh affinity to oxygenScheme of corrosion (material) loss and interaction modes of steels in Pb/Pb-Bi melts depending on the oxygen concentration in the liquid metal at fixed time and temperaturethan Pb or Bi.12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department2(modified based on the experimental graph of I. Gorynin et al., Metal Science and Heat Treatment,. 41,. No  9- 10, 1999, 384)Materials(Fe – Bal.)Austenitic steelsCr Ni Mo Mn Si Cu V W Al Ti C N P S B316L 16.73 9.97 2.05 1.81 0.67 0.23 0.07 0.02 0.018 - 0.019 0.029 0.032 0.0035 -1.4970 15.95 15.4 1.2 1.49 0.52 0.026 0.036 < 0.005 0.023 0.44 0.1 0.009 < 0.01 0.0036 < 0.01   1.4571 17.50 12 2.0 2.0 1.0 - - - - 0.70 0.08 - 0.045 0.015 -1.4970 (15-15Ti) 316L 1.4571 (material of CORRIDA loop)Shape and dimensions of sample for corrosion tests General view of initial sampleHV30 = 253;Grain size ranged from 20 to 65 µm;Intersecting deformation twins.HV30 = 132;Grain size averaged 50 µm (G 5.5);Annealing twins.HV30 = 245;Fine-grained structure with grainsize averaged 15 µm (G 9.5).Manufacturing procedure:12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department3 Electric Discharge Machining (EDM) + finishing turningTest parametersT = 550(+5)°C, T 385°C 10 7 % i t 10 4 10 5 %Omin ≈ , cO = – mass , excurs on o – – – mass , v = 2(+/–0.2) m/s, initially 1.5–1.6 m/s, t = 288; 715; 1007; 2011 hT = 450(+5)°C  ,Tmin ≈ 350°C, cO = 10–7 mass%, excursion to 10–5 mass% Ov = 2(+/–0.2) m/s,t = 500; 1007; 1925; 2015; 3749; 5015; 8766 hT = 400(+5)°C  ,Tmin ≈ 350°C, cO = 10–7 mass%,v = 2(+/–0.2) m/s,t =  1007; 2015; 4746 h; still continuing up to 10000h12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department4CORRIDA loopQuantification of corrosion lossGoal of quantificationMaterial loss, average of general corrosion and maximum of local corrosionThickness of adherent (oxide) scaleOverall change in dimensions, including the scaleAmount of metals transferred to the liquid metalMetallographic method (cylindrical specimens)Measurement of initial diameter in alaser micrometer with 0.1 µmresolutionDi t f ff t d t i l dame er o una ec e ma er a anthickness of corrosion zonesdetermined in a microscope (LOM)with 1 µm resolutionOccurrence of different corrosionmodes on opposing sides of the re-measured diameter is considered inthe evaluation12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department5Qualification of corrosion modes on surface of austeniticsteels after exposure to flowing LBE with 10–7 mass% Ot 450 d 550°Ca anSurface examinations - general corrosion appearanceAfter cleaning in glycerin After chemical cleaning1.4970, 550°C1007 h 2011 hOxidation – formation of golden-colored oxide film (shorter test) and green-colored oxide film (longer test)Light areas with exfoliated oxide film; Severe local solution-based corrosion attack in the form of hemispherical pits and longitudinal andtransversal grooves;The surface area covered by the oxide film decreases with exposure time in LBE, while the number ofsites affected by local corrosion attack respectively increases.12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department6Surface examinations of tested steels550°C 2000 hof Ni and Cr450°C, 2000 h,  Surface of austenitic steels are cowered by thin (≤0.5 µm) Cr-based oxide film;Porous corroded surface markedly depleted in Cr and Ni and penetrated withPb and Bi is also observed12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department7.Effect of temporal increase in oxygen concentration in LBEGrowth of rare magnetite protrusions on the surface of 316Lsteel (550°C, 1007 h) (Fig. a);Formation of islands of Fe-Cr spinel (1.4970 exposed at550°C (Fig b)12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department8. .Cross-section examination of tested steels1.4970550°C2011 h12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department9Local pit-type corrosion attackExpected sequence of evolution of corrosion pits wit time12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department10Quantification of corrosion loss at 450 and 550°C in LBE with 10–7 mass% OAverage corrosion loss of steels, expectedly, increase with rise in test temperature from 450 to 550°C450°C:Metal recession (change in diameter) does not exceed 4, 27, and 26 µm after 8766 h for 1.4571, 1.4970 and316L steels, respectively;Thickness of layer-type attack (ferrite) averaged 5, 7 and 4 µm after 8766 h for 1.4571, 1.4970 and 316Lsteels, respectively;Depth of pit-type attack average 50, 114 and 136 µm correspondingly. The percentage of circumferenceaffected by selective leaching increases with time and after 8766 h reached 100 %.550°C:Metal recession averaged ~ 60, 46 and 51 µm after 2011 h for 1.4571, 1.4970 and 316L steels, respectively;Layer-type attack averaged 23, 30 and 46 µm;Depth of pit-type attack averaged 182, 124 and 127 µm.Average values of metal recession, thickness of ferrite layer and depth of pit-type attack could result in underestimationof corrosion rate!Maximum depth of solution based attack seems to be most adequately reflects corrosion loss of austenitic steels and12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department11,therefore could be used as parameter for evaluation of corrosion rate using linear law!Percentage (%) of circumferenceaffected by solution-basedl ti l hi tt k th tse ec ve eac ng a ac aresulted in either formation oflayer-type (L) or pit-type (P)damage12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department12The percentage of surface affected by selective leaching attack increases with time.Effect of initial microstructure on the propagation depth of solution-based attackAs-received Exposed to LBE and chemically cleanedDeformation twins in the body of grain Preferential solution-based attack along twinsMicro-defects: cavitiesPre-existing “active” diffusion paths, i.e. grain or sub-grain boundaries and twins (deformation andsolution) are the preferential paths for solution-based attack via selective leaching of Ni and Cr andsubsequent penetration of Pb and Bi into steel matrix.12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department13Maximum depth of solution-based attack on austeniticsteels tested at 450 and 550°C in LBE with 10–7 mass% O450°C 550°C   450°C:1.4970 – the time dependence of maximum depth of attack consists of initial transient period of faster kinetics (up to2000 h) and steady-state period. Corrosion rate of calculated based on steady-state period is about 184 µm/year;1 4571 – steady-state period established after 2000 h resulted in corrosion rate 164 µm/year;.316L – available data are scarse enough to be approximated using linear law. Corrosion rate based on the nominalvalue after 8766h is 210 µm/year. In comparison with 1.4970 and 1.4571 the incubation time for 316L is substantiallylonger, i.e. about 4000 h.550°C:1 4970 i d th f tt k ft 2011h i 207. – max mum ep o a ac a er s µm;316L – maximum depth of attack after 2011h is 158µm;1.4571 – maximum depth of attack after 2011h is 587µm, i.e. about three times higher than those for 1.4970 and316L.Steel which showed the longest incubation period, i.e., 316L at 450°C and 1.4571 at 550°C, 12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department14revealed afterwards the deepest attack!Comparison of results at 10–7 and 10–6 mass% O(CORRIDA experiments) 10-6 mass% O – preferential oxidation(spinel formation);This workC.Schroer, Cor.Sci. 84 (2014) 11310-7 mass% O – preferential solution-based selective leaching of steel constituents(Ni, Cr);1 4571At both concentrations the local solution-based attack - critical factor affectingcorrosion resistance of austenitic steels in.550°C10-6 mass%O316LLBE;Under the other similar conditions of testthe finer grains (15µm) of steel (1.4571 bluemarkers) of steel the deeper corrosion attack(coarse-grained (50µm) 316L red markers).Maximum depth of pit-type corrosion attack on austenitic        steels tested in flowing LBE (~ 2 m/s) depending on temperature and oxygen concentration in the melt. 12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department15Comparison of corrosion rate of 316L tested in this work with literature dataCorrosion rates of 316L steel in comparison withdata generalized by Yamaki et al. :4 0°CCorrosion rate of 316L versus temperature and liquid metalYamaki et al. [Cor. Sci. 53, 2011, 3075-3085]580 µm/year - Yamaki et al.210 µm/year - this work (nominal value)550°C280 µm/year - Yamaki et al.560 / thi k (liµm year - s wor nearapproximation)Markedly higher corrosion loss of 316L steel inthi k ld b d bThis works wor cou e cause y:flowing conditions in this test while datapresented by Yamaki et al. correspondmainly to static conditions;i l d i thi k fmax mum va ues use n s wor orevaluation of corrosion loss while datapresented by Yamaki et al. could correspondto averaged values.log Jcorr (µm/year) = 6.5 – 27705 / RT12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department16Cross-section appearance of austenitic steels after test in flowing oxygen-containing LBE (~ 2 m/s, ~ 10–7 mass % O) t 400°C f 4746 ha  or .1.4970 316L 1.4571LBESmooth undamaged Smooth undamaged surface Smooth undamaged surfacesurfaceSmooth undamaged surface is observed on the cross-section of samples;Selective leaching attack is not detected under the given duration of test - 4746h;Samples revealed golden-colored oxide film - protective scaling;Corrosion tests are still continuing with expected max. duration about 10000h.12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department17Quantification of corrosion loss of austenitic steelsafter exposure to flowing LBE (2 m/s) at 400°C with10 7 % O– massMetal recession is in the range of error of the metallographicmeasurements (±2–4 µm) i e no metal recession observed;, . .,Metallographic investigations clearly showed absence of solution-based attack at400°C for duration of test 4746 h.12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department18Possible effect of Ti(C,N) precipitation and Cr-rich lamellaeon the preferential initiation and propagation corrosioneTi(C,N) precipitation incomposition of 1 4970 andInitial state .1.4571Cr-rich lamellae (Fe-20%Cr-316L 1.4970E4%Ni) in composition of316Lsure to LBETi(C,N) precipitation andCr-rich lamellae areAfter expos corrosion resistant to LBEwith 10-7mass%O12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department19Effect of surface preparation on the corrosion responseLongitudinal grooveInitial surface After test in LBETransver70 µmrsal grooveLBETurning tracesGeneral surface topography of 1.4970 sample after 5015 h test in LBE at 450°C and subsequent cleaningPits of sample 12Oxide filmdinal dinal ee T lOxide filmLong axisD LongitudLongitudgroovegrooveTTTransversa  grooveMacro-defects: transversal and longitudinal grovesPreferential corrosion in the form of transversal and longitudinal groves is associated with surface3Exfoliated area12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department20pattern obtained after finishing turningEffect of surface finishing on the corrosion appearanceof 1.4970 steel tested in flowing oxygen-containing LBE(~ 2 m/s ~ 10–7 mass % O) at 400°C, .Flattened surface area of rod sample finished by:Grinding (500-grid SiC paper) – similar surfaceappearance as on the turned surface i e oxidation;, . .Polishing (diamond pastes 9-1µm) – origination ofsolution-based liquid-metal attack.1007 h 4746 h  SurfaceSurface Cross-sectionFe-crystalliteIntergranular tt kLBEa acPreferential solution-based Solution-based attack resulted in LBE is detected between Fe-t llit d t itiattack along grain-boundaries(intergranular)the formation of separated Fe-based crystallites (fine andcoarse);Composition of coarsecrystallites: Fe(bal.)-3.5mass%Crcrys a es an aus en cmatrix;Volume increase due totransformation from fcc γ-ironto bcc α-iron.12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department21ConclusionsInteraction of austenitic steels (1.4970, 316L and 1.4571) with flowing (2 m/s) LBE with 10-7 mass % O was accompaniedby oxidation (400, 450 and 550°C) and solution-based liquid-metal attack (450 and 550°C) resulted in selectiveleaching of Ni and Cr from the sub-oxide layers and subsequent development of ferrite zone penetrated by LBE:400°C: oxidation – thin Cr-based oxide film (protective scaling)solution-based attack is not observed after 4746 h; test is continuing up to 10000h450°C: oxidation – thin (≤ 0.5 µm) Cr-based oxide filmsolution-based selective leaching with maximum depth of local attack 114µm (1.4571), 183µm (1.4970)and 210µm (316L) for 8766h550°C: oxidation – thin (≤ 0.5 µm) Cr-based oxide filmsolution-based selective leaching with maximum depth of local attack 587µm (1.4571), 207µm (1.4970)and 158µm (316L) for 2011 hCr-based oxide film, formed in-situ on the surface of austenitic steels, is not a sufficient protective barrier withrespect to the selective leaching attack at least at 450 and 550°C in the LBE with 10-7 mass%O!In the LBE with 10-7 mass%O the selective leaching is a main corrosion mechanism of austenitic steels causingsubstantial corrosion loss, while in LBE with 10-6 mass%O the oxidation prevails.The local deep solution-based attack due to selective leaching of steel constituents is a critical factor affectingcorrosion resistance of austenitic steels in oxygen-controlled LBE while oxidation is only postpones the unavoidablestart of selective leaching.12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department22Thank you for attention !!!AcknowledgementsThe construction and operation of the CORRIDA loop wasfinancially supported by the Nuclear Safety Programme of KIT.The presented work is part of the MATTER project that hasreceived funding by the 7th Framework Program of the EU(Grant Agreement No. 269706).12th International Workshop on Spallation Materials Technology                                                               Institute for Applied Materials –IWSMT - 12 Material Process Technology (IAM-WPT)19-23 October 2014, Bregenz, Austria Corrosion Department23

Corrosion response of 1.4970, 316L and 1.4571 austenitic steels to flowing LBE with 10⁻⁷ mass % dissolved oxygen at 400, 450 and 550⁰C

https://publikationen.bibliothek.kit.edu/230103307/3816983

Corrosion response of 1.4970, 316L and 1.4571 austenitic steels to flowing LBE with 10⁻⁷ mass % dissolved oxygen at 400, 450 and 550⁰C

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