Pshenichnikov, A.

Stuckert, J.

English

KITopen

KIT – University of the State of Baden-Württemberg andNational Large-scale Research Center of the Helmholtz AssociationInstitute for Applied Materials, IAM-WPT, Program NUKLEARwww.kit.eduMicrostructure and mechanical properties of Zircaloy-4 claddings hydrogenated at temperatures typical for LOCA conditionsA. Pshenichnikov, J. StuckertQWS19, Karlsruhe 2013221.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopStructure assessment of annealed and hydrogenated specimensFracture surface investigationZirconium hydrides detectionProgress in understanding the mechanism of embrittlement of Zirconium alloysApplication to the results of QUENCH-LOCA testObjectives321.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-Workshop* According to E. Zuzek et al., Bull. Alloy Phase Diagr. (1990), 385Equilibrium phase diagram of Zr-H system*Region of interest is LOCA conditionsCooling in airselected examples of our tests700 wppm H 9500 wppm H421.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopMaterial: Conventional Zircaloy-4 cladding tubeICP-OES measurement of Zircaloy-4 chemical composition (by weight):Sn: 1.33±0.02%, Fe: 0.23±0.002%, Cr: 0.12±0.0003%, O: 0.116±0.003%, Zr balanceMaterial and methods of investigation• Hydrogenation in Ar+H2 gas mixture in LORA-furnace• Metallographic investigations and microhardness tests of the tube section• X-Ray diffraction analysis in the cladding tube wall middle• Scanning electron microscopy of polished and etched as well as fractured surfacesMethods of investigation:521.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopSpecimen before hydrogenationHydrogenation facilityLORA furnaceExperimental procedure Specimen withdrawal in air after hydrogenationCooled specimen after hydrogenationHydrogen gas partial pressure was 0.1 barEstimated cooling rate was 5 K/sH2 duration was 2 to 12 minutes621.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopResults of metallographic observations721.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopAnnealing of Zircaloy-4 cladding at various temperatures during 8 minutes and fast cooling  in air Optical metallography of annealed Zircaloy-4As-received 700 °C800 °C 900 °CAt 810 °C starts α → β phase  transformation821.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopHydrogenation of Zircaloy-4 cladding at 600 °C in Ar+H2 mixture and fast cooling in air Optical metallography of hydrogenated Zircaloy-4780 wppm H 1400 wppm H2000 wppm H 3490 wppm H921.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopHydrogenation of Zircaloy-4 cladding at 700 °C in Ar+H2 mixture and fast cooling in air 1330 wppm H 2250 wppm H4760 wppm H4000 wppm HOptical metallography of hydrogenated Zircaloy-4α - Zr„islands“1021.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopHydrogenation of Zircaloy-4 cladding at 800 °C in Ar+H2 mixture and fast cooling in air 1790 wppm H 3060 wppm H8600 wppm H 9550 wppm HOptical metallography of hydrogenated Zircaloy-41121.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopHydrogenation of Zircaloy-4 cladding at 900 °C in Ar+H2 mixture and fast cooling in air 880 wppm H 1500 wppm H2000 wppm H 6700 wppm HOptical metallography of hydrogenated Zircaloy-41221.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopScanning Electron Microscopypolished and etched specimens1321.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopScanning electron microscopy of annealed and hydrogenated Zircaloy-40 wppm H8600 wppm HAfter polishing and etching1421.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopScanning electron microscopy of annealed and hydrogenated Zircaloy-40 wppm H8600 wppm HAfter polishing and etching1521.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopScanning electron microscopy of annealed and hydrogenated Zircaloy-40 wppm H8600 wppm HAfter polishing and etchingα-Zr(O)?α-Zr (prior βphase)?γ- Zr hydrides?δ- Zr hydrides?1621.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopScanning Electron Microscopyfracture surface1721.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopScanning electron microscopy of fracture surfaces of hydrogenated Zircaloy-4 720 wppm H 1860 wppm H2790 wppm H 4850 wppm H700 °C1821.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopScanning electron microscopy of fracture surfaces of hydrogenated Zircaloy-4 1110 wppm H 3070 wppm H800 °C1921.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopScanning electron microscopy of fracture surfaces of hydrogenated Zircaloy-4 1170 wppm H 1640 wppm H900 °CBrittle fracture Ductile fracture on needles of α-Zr(O)2021.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopMicrohardness tests2121.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopMicrohardness of annealed and hydrogenated Zircaloy-4The diagonal length of resulting indented square was about 10 µm.hydrogen + T impactat 900 °Chydrogen impactat 600 °C2221.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopX-Ray diffraction analysis2321.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopX-Ray profiles of Zircaloy-4 sampleshydrogenated at 600 °CHydridesare compressed with 0.5% of local strain2421.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopX-Ray profiles of Zircaloy-4 sampleshydrogenated at 700 °C2521.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopX-Ray profiles of Zircaloy-4 sampleshydrogenated at 800 °C2621.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopChange of lattice parameters after hydrogenationof Zircaloy-4 samples 2D projection of HCP-lattice without hydrogen With hydrogenγ – hydride ZrH scheme δ – hydride ZrH1,66 schemeacScheme of decohesion mechanism, accompanied by hydride formation3D model of HCP-latticeac2721.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopConclusion• No “macroscopic” hydrides were detected by means of optical microscopy, only highmagnification SEM observations reveal presumable submicroscale hydrides.• Microhardness tests showed a relationship between hydrogen content hardening, annealingsoftening and hardening due to β → α transformation during cooling phase.• The XRD-analysis showed the presence of γ-, δ-phases of zirconium hydrides in all ofperformed experiments. With the increase of hydrogen content the hydride peak intensitywas also increased. Simultaneously the hydrogen should be partially dissolved in the latticewhich is indicated by increase of the lattice parameter “c”.• Because carried out observations have proved only the presence of hydrides and gave notenough information on the hydride structure and distribution, further detailed EBSD andTEM investigations should be performed in order to determine the location, morphologyand orientation of nano-scaled hydrides and to separate hydrides from other structuralfeatures.• The performed experiments can explain the absence of macroscopic hydrides in QUENCH-LOCA experiments. The increased brittleness of some zirconium claddings after QUENCH-LOCA tests could be caused by nano-scaled hydrides which are distributed in the bulk ofmaterial. The fact of the growth of the lattice parameter “c” allows to suggest that thedecohesion mechanism accompanied by hydride formation could be responsible forcladding destruction.2821.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopAknowledgementsThe authors would like to thank the following KIT colleagues:• Dr. Mario Walter for fruitful discussions• Mrs. Ursula Peters for her technical assistance with the hydrogenation tests• Ms. Julia Lorenz for the help during preparation of the specimens for metallographicobservations• Dr. Harald Leiste for carrying out of X-Ray diffraction measurements• Dr. Marcus Müller for carrying out of FEG-SEM observations2921.11.2013 A. Pshenichnikov , J. Stuckert19th QUENCH-WorkshopThank you for your attention!anton.pshenichnikov@kit.edujuri.stuckert@kit.eduhttp://www.iam.kit.edu/wpt/471.php 

Microstructure and mechanical properties of zircaloy-4 claddings hydrogenated at temperatures typical for LOCA conditions

https://publikationen.bibliothek.kit.edu/240093453/3816416

Microstructure and mechanical properties of zircaloy-4 claddings hydrogenated at temperatures typical for LOCA conditions

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