He, P.

Klimenkov, M.

Lindau, R.

Möslang, A.

English

KITopen

KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association www.kit.eduFatigue-structure correlation of 13.5%Cr ODS steels at 550°C for fusion applicationKarlsruhe Institute of TechnologyInstitute for Applied MaterialsApplied Materials Physics (IAM-AWP)Karlsruhe, GermanyP. He, M. Klimenkov,  A. Möslang, R. LindauInstitute for Applied Materials Applied materials physics (IAM-AWP) Introduction- Life-limiting failures of first wall and blanket structures- Fatigue issue on Reduced-activation F/M steels and ODS varients- Development of ODS RAF steels Experimental- Fabrication route- Sample preparation and monitoring  Fatigue and microstructural results- S-N curve, hysteresis loops- Structural results: grain structure, dislocation density, precipitates and ODS particles Summary1 | Pei He | ICFRM-16, Oct. 20-26, 2013, Beijing, ChinaOutlineInstitute for Applied Materials Applied materials physics (IAM-AWP)Materials challenges in fusion reactors2 | Pei He | Beijing, China                                                         Oct. 20-26, 2013ITER3 dpa/lifetimeFirst wall in ITER DEMO adv.Peak surface heat flux [MW/m2]0.6 2.5 (blankets)/10-15 (divertor)Number of pulses [×104] 2-5 Pulsed or steady-state operationTotal burn time [h] 104-3×104 OpenNeutron damage [dpa] 12-36 ~150Structural components: Fatigue Creep Creep-fatigue Irradiation ErosionCorrosionInstitute for Applied Materials Applied materials physics (IAM-AWP)3 | Pei He | ICFRM-16, Oct. 20-26, 2013, Beijing, ChinaBlanket: 30 dpa/year,  2.5MW/m2Reduced-activationferritic-martensitic steelsNanostructured RAF(M)-ODS-steels~300 - 800 °CMaterial challenges in Fusion ReactorTemperature (a) and stress (b) variation during one burn/dwell cycle and long-term stress variation (c)D. Munz et al., FUSION ENG DES (1991)Structural components: The lifetime can be limited by different failure modes For pulsed tokomaks (ITER), fatigue is the most life-limiting event. For steady-state operation, creep-fatigue and irradiation damages are of particular concern.Institute for Applied Materials Applied materials physics (IAM-AWP)4 | Pei He | ICFRM-16, Oct. 20-26, 2013, Beijing, ChinaReduced Activation F/M steels:10-3 10-2 10-1 100 101 102 103 104 105 10610-710-61x10-51x10-410-310-210-1100101102103104105Hands-on LevelLow Level WasteMedium Level WasteHigh Level Waste MANET-II OPTIFER EUROFER-97 F82H-mod EUROFER ref. FESurface Gamma Dose Rate [Sv/h]Time after Irradiation [y]Long term irradiation (12.5 MWa/m2) of a DEMO reactor first wallLindau et al., FUSION ENG DES (2005)The superiority of RAFM steels: Low activation capability low swelling, high thermal conductivity, low thermal expansion and better liquid-metal compatibility in comparison to austenitic steels.Materials Fatigue Topic Author12Cr steelMANETStrain-controlledisothermal Influence of irradiation (T, dose) and He implantination;In-situ and post-irradiation R. Lindau,J. Bertsch9Cr F82H mod.Strain-controlled isothermal Fatigue behavior and the growth of microcracks after He implantination; Post-neutron irradiationPost-ion implantinationJ. BertschT. HiroseF82H mod.OPTIFIER IVMANET IIThermal fatigue(TF)Fatigue endurance of RAFM steels under cyclic strains and stresses produced by temperature changesC. PetersenEUROFER97Isothermal; TF;Multiaxial fatigue;multi-step loading;Fatigue-creep interactionCyclic softening;Modelling of high temperature damage under TF loading;Creep-fatigue interactionC. PetersenJ. AktaaC. VorpahlInstitute for Applied Materials Applied materials physics (IAM-AWP)5 | Pei He | ICFRM-16, Oct. 20-26, 2013, Beijing, ChinaFatigue behavior of EUROFER 97Alloy C Si Mn Cr V W TaEUROFER 97 0.12 0.06 0.42 8.87 0.19 1.1 0.14C. Petersen et al., J. Nucl. Mater. (2009)100 1000 10000 1000000,512 unirradiated 2 dpa 31 dpaEUROFER 97Tirr = Ttest = 300°C  Total Strain Range [%]Number of Cycles to Failure- Above t  0.9%:Lifetime reduction- Below t  0.9%:Lifetime extensionInstitute for Applied Materials Applied materials physics (IAM-AWP)6 | Pei He | ICFRM-16, Oct. 20-26, 2013, Beijing, ChinaCyclic softening- Pronounced cyclic softening (> 100 MPa)- beyond N~50  max becomes independent of  t lifetime limiting crack initiation & networkformation occurs before 100 cycles No evident cyclic softening for 9Cr-ODS and 12Cr ODS steels.  Ferritic ODS steels enable higher operational temperature. S-N curve for 9Cr–ODS and 12Cr–ODS steels and Mod. 9Cr– 1Mo steel at 0.5% total strain at 923 KUkai et al., J. Nucl. Mater. (2007)C. Vorpahl et al., J. Nucl. Mater., 2011, p16EUROFER 97, 550 °C 650 °CInstitute for Applied Materials Applied materials physics (IAM-AWP)7 | Pei He | ICFRM-16, Oct. 20-26, 2013, Beijing, China Developing RAF ODS steels by optimization of production route powder metallurgy + thermomechanical processing (TMP) Exploring structure-property correlation Strain-controlled low cycle fatigue tests at 550 °C Structure evolution before and after fatigue tests-- grain structure-- precipitates and oxide particles-- dislocation densityThe objective of this workNo. Cr W Ti Y2O3 RemarksK9 13.5 1.1 0.3 0.3 1 kg, HIP + TMPK14 13.5 1.1 0.3 0.0 1kg, HIP + TMPInstitute for Applied Materials Applied materials physics (IAM-AWP) Introduction- Life-limiting failures of first wall and blanket structures- Fatigue issue on Reduced-activation F/M steels and ODS varients- Development of ODS RAF steels Experimental- Fabrication route- Sample preparation and monitoring  Fatigue and microstructural results- S-N curve, hysteresis loops- Structural results: grain structure, dislocation density, precipitates and ODS particles Summary8 | Pei He | ICFRM-16, Oct. 20-26, 2013, Beijing, ChinaOutlineInstitute for Applied Materials Applied materials physics (IAM-AWP)9 | Pei He | ICFRM-16, Oct. 20-26, 2013, Beijing, ChinaFabrication processZOZ Simoloyer CM01milling container MA: under H2, 1000/4'/700/1'/24h, Glove-Box HIP: 1150°C, 100 MPa, 2.5h TMP: 3 passes cross rolling at 1100°C + Annealing at 1050°C, 2h, VacuumCapsules after HIPCross rolling processInstitute for Applied Materials Applied materials physics (IAM-AWP)10 | Pei He | Beijing, China                                                         Oct. 20-26, 2013• Deformation volume:- Length    7.60 mm- Diameter 2.00 mm• Total specimen length: 27.0 m• Cylindrical gauge lengthLCF Specimen UTM with vacuum furnaceT = 550 °CFatigue sample and Universal testing machinefatigueInstitute for Applied Materials Applied materials physics (IAM-AWP)Fatigue sample geometry and preparationNo. Abrasive size[µm]Remarks1 18.3 Grinding paper2 15 Thread and diamond paste3 94 6Mechanical polishing proceduresElectro polishing procedureNo. Electrolyte Voltage5 20 % H2SO4+80 % CH3OH12 V20 µmK9-020 µmK9-120 µmK9-220 µmK9-320 µmK9-420 µmK9-5• The surface conditions of fatigue samples are evidently improved.  11 | Pei He | Beijing, China                                                         Oct. 20-26, 2013Institute for Applied Materials Applied materials physics (IAM-AWP) Introduction- Life-limiting failures of first wall and blanket structures- Fatigue issue on Reduced-activation F/M steels and ODS varients- Development of ODS RAF steels Experimental- Fabrication route- Sample preparation and monitoring  Fatigue and microstructural results- S-N curve, hysteresis loops- Structural results: grain structure, dislocation density, precipitates and ODS particles Summary12 | Pei He | ICFRM-16, Oct. 20-26, 2013, Beijing, ChinaOutlineInstitute for Applied Materials Applied materials physics (IAM-AWP)Fatigue results for 13.5Cr1.1W0.3Ti ODS steel (TMP)103 104 1050,010,11550 C tpe Strain range,[%]Cycles to failure, Nf  100 101 102 103 104 105 106200400600800Stress amplitude,a[MPa]Number of cycles to failure,Nf 550°C =0.54% =0.56% =0.6% =0.6% =0.7% =0.8% =0.9%• Simple linear relationship for totalstrain and elastic strain and plasticstrain as a function of Nf.• S-N curves reveal constant stress during thewhole test irrespective of the strain range(no cyclic softening)13 | Pei He | ICFRM-16, Oct. 20-26, 2013, Beijing, China∆εt σa [MPa] Nf0.54% 350 9000.9% 520 1.7*105Institute for Applied Materials Applied materials physics (IAM-AWP)Fatigue results for 13.5Cr1.1W0.3Ti ODS steel (TMP)• The stress stability of 13.5Cr1.1W0.3Ti ODS ferritic steel is supported by hysteresis loops.• Superposition of hysteresis loops suggest no cyclic softening or hardening• At t  0.54 %, slight plastic deformation; at t  0.9 %, plastic deformation  0.3%14 | Pei He | ICFRM-16, Oct. 20-26, 2013, Beijing, China-0,4 -0,2 0,0 0,2 0,4-600-400-2000200400600  3rd cycle 100 cycle 0.5Nf 0.95Nf   Stress, MPaStrain, [%]∆σ∆εp ∆εe∆εt  0.54 %, T=550°C t  0.9 %, T=550°CInstitute for Applied Materials Applied materials physics (IAM-AWP)Fatigue results100 101 102 103 104200400600800  EUROFER, HIP EUROFER ODS, HIP 13.5Cr1.1W0.3Ti, 13.5Cr1.1W0.3Ti ODS, HIP 13.5Cr1.1W0.3Ti ODS, HIP+TMP  Stress,[MPa]Number of cycles to failure, Nf• RAFM steels (EUROFER):pronounced cyclic softening• 13.5Cr ferritic ODS steel (TMP):- outstanding fatigue resistance- constant stress15 | Pei He | Beijing, China                                                         Oct. 20-26, 2013t  0.7 %, T=550°CInstitute for Applied Materials Applied materials physics (IAM-AWP)Microstructure evolution for EUROFER 97 at 550 °CC. Vorpahl et al., J. Nucl. Mater., 2011, p16Cyclic softening (100 MPa) can attributed to• Formation of coarse precipitates at GB• Dramatic  reduction of dislocation density16 | Pei He | Beijing, China                                                         Oct. 20-26, 2013As-recieved ∆εt = 0.45% after 60,850 cycles Institute for Applied Materials Applied materials physics (IAM-AWP)Microstructure evolution for 13.5Cr ODS steelAs recieved ∆εt=0.9%, after failure1µm0.5µm 200nmAs received- Elongated grains retained from TMP- Nanoscale equiaxed grains - Random distribution of Ti oxidesAfter LCF test- Stable grain structure - Multiple dislocation-precipitate (Ti oxide) interaction1µm17 | Pei He | Beijing, China                                                         Oct. 20-26, 2013Institute for Applied Materials Applied materials physics (IAM-AWP)Dislocation densityAs recieved ∆εt=0.9% after failure50nmLtn218 | Pei He | Beijing, China                                                         Oct. 20-26, 2013Measurement Dislocation densitybefore LCF [m-2]Dislocation densityafter LCF [m-2]1 1.15×1015 7.0×10142 4.21×1014 4.77×10143 7.56×1014 8.05×1014Average 7.75×1014 6.6×1014n: intersection number of the gridlines and dislocations;L: length of the gridlines;t: thickness of the sampleParticle-dislocation interactionInstitute for Applied Materials Applied materials physics (IAM-AWP)ODS particles50nmYTiAs received ∆εt=0.9%, after failure19 | Pei He | Beijing, China                                                         Oct. 20-26, 2013d  5 nm 50nmY-Ti oxides Institute for Applied Materials Applied materials physics (IAM-AWP)Fatigue-Microstructure correlation50nmStablized nanoscale dispersoidsUltra stable microstucture(grain, dislocaiton density)Outstanding fatigue resistance for 13.5Cr ODS steel after TMPBefore LCF test After LCF test20 | Pei He | Beijing, China                                                         Oct. 20-26, 2013100 101 102 103 104200400600800  EUROFER, HIP EUROFER ODS, HIP 13.5Cr1.1W0.3Ti, 13.5Cr1.1W0.3Ti ODS, HIP 13.5Cr1.1W0.3Ti ODS, HIP+TMP  Stress,[MPa]Number of cycles to failure, Nft  0.7 %, T=550°CInstitute for Applied Materials Applied materials physics (IAM-AWP)100 1000 10000 1000000,511,52 EUROFER ODS, 0.3Y2O3 unirradiated 2 dpa 31 dpa Strain range,[%]Cycles to failure, Nf Fatigue-Microstructure correlation21 | Pei He | Beijing, China                                                         Oct. 20-26, 2013- high strain regime, shorter lifetime→ accelerated crack initiation due toirradiation hardening or oxide dispersionstrengthening.- low strain regime, prolonged lifetime→ Micro-crack growth impeded by irradiationdefects or oxide particles- Critical strain range is dependent on the materials(0.7% or 0.9% ).• HIP vs. HIP+TMP-10 time lifetime prolongation at ∆ε=0.7% after TMP• 13.5Cr1.1W ODS (TMP) vs. EUROFER ODS- Above t  0.7 %: Lifetime reduction- Below t  0.7 %: Lifetime extensionInstitute for Applied Materials Applied materials physics (IAM-AWP)Fatigue-Microstructure correlation22 | Pei He | Beijing, China                                                         Oct. 20-26, 2013aKIc RAFM steel:Low strengthODS steel or irradiated steels: high strengthLow strainHigh strain Grain boundary Crack Irradiation defects or ODS particles50% life time for crack segment with the dimension of grain sizeVery early crack network formationdue to irradiation hardening or oxide strengtheningHigh strainLow strainJ. Bertsch et al., J.Nucl.Mater. (2000)Institute for Applied Materials Applied materials physics (IAM-AWP)23 | Pei He | ICFRM-16, Oct. 20-26, 2013, Beijing, ChinaSummary TMP leads to a remarkable lifetime extension for 13.5Cr1.1W ODS steel.→ Lifetime extension with a factor of 10 to 20 when ∆εt ≤ 0.7%. EUROFER ODS vs. 13.5Cr1.W ODS steel after TMP→ dependent on the strain range.∆εt＞0.7%, shorter lifetime; ∆εt ≤ 0.7%, prolonged lifetime.→ different microstructural barriers (oxide particles, irradiation defects  or grain boundaries) and their influence on the crack growth. The constant stress amplitude for 13.5Cr1.1W ODS steelirrespective of strain range→ stable grain structure, constant dislocation densities of 1014 m-2.→ highly stabilized nanoscale oxide with an average diameter of 5 nm.Institute for Applied Materials Applied materials physics (IAM-AWP)24 | Pei He | ICFRM-16, Oct. 20-26, 2013, Beijing, China

Fatigue-structure correlation of 13.5%Cr ODS steels at 550⁰C for fusion application

https://publikationen.bibliothek.kit.edu/230093444/3816409

Fatigue-structure correlation of 13.5%Cr ODS steels at 550⁰C for fusion application

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