The Irradiation Performance and MicrostructuralEvolution in 9Cr-2W Steel Under Ion Irradiation

Sultan Alsagabi, Indrajit Charit, and Somayeh Pasebani

(Submitted July 22, 2015; published online December 24, 2015)

Grade 92 steel (9Cr-2W) is a ferritic-martensitic steel with good mechanical and thermal properties. It isbeing considered for structural applications in Generation IV reactors. Still, the irradiation performance ofthis alloy needs more investigation as a result of the limited available data. The irradiation performanceinvestigation of Grade 92 steel would contribute to the understanding of engineering aspects includingfeasibility of application, economy, and maintenance. In this study, Grade 92 steel was irradiated by ironion beam to 10, 50, and 100 dpa at 30 and 500 �C. In general, the samples exhibited good radiation damageresistance at these testing parameters. The radiation-induced hardening was higher at 30 �C with higherdislocation density; however, the dislocation density was less pronounced at higher temperature. Moreover,the irradiated samples at 30 �C had defect clusters and their density increased at higher doses. On the otherhand, dislocation loops were found in the irradiated sample at 50 dpa and 500 �C. Further, the irradiatedsamples did not show any bubble or void.

Keywords 9Cr-2W steel, irradiation performance, irradiation-induced hardening, microstructural evolution

1. Introduction

Ferritic-martensitic (F-M) steels possess superior mechani-cal and thermal properties (Ref 1-3). For instance, high-temperature creep strength, adequate thermal conductivity, andlow thermal expansion coefficient (Ref 4-6). These steels havefound use in various structural applications in fossil fuel powerplants. Interestingly, F-M steels also possess low swelling rates;thus, these steels also show promise for structural applicationsin the advanced reactors (Ref 1, 7). F-M steels, austeniticstainless steels, and nickel-based alloys were candidate asstructural components in some advanced reactors such as thesuper-critical water reactors (SCWR) (Ref 8, 9). For example,Grade 91, HT9, and Grade 92 are considered as the structuralcomponents as a result of their superior properties (Ref 10, 11).The F-M steels would be less vulnerable to radiation-induceddamages such as swelling and transmutation as a result of theminor Ni content in these steels, making these steels moreresistant to helium transmutation when exposed to neutronirradiation (Ref 10, 11). Thus, the F-M steels have attractedmuch attention (Ref 8, 9).

The F-M steel 9Cr-2W (also known as Grade 92 steel) hadlower hardening than other F-M steels (Ref 12). The inducedradiation damage assessment on ferritic-martensitic steels needsfurther investigation because of the limited available data.

Therefore, the evaluation of the irradiation-induced damage iscrucial to evaluate the irradiation behavior as these steelsbecome exposed to irradiation such as the microstructuralevolutions which alter the mechanical properties (Ref 13). Forexample, the irradiation-induced microstructural evolutionssuch as the segregation of main strengthening elements in 9-12% Cr steels (Cr and W) and depletion of Fe in carbides wereobserved as dose increases at room temperature (Ref 14). Also,the irradiation-induced segregation and depletion become moresevere at higher dosage under heavy ion irradiation in 9-12% Crsteels (Ref 14).

Irradiation temperatures influence the radiation damage inF-M steels, which consequently alter the mechanical propertiesbefore reaching a saturation stage. (Ref 1, 8). The irradiation-induced swelling in 9-12% Cr steels showed low swelling rates.Two F-M steels had less than 2% swelling when irradiated at200 dpa (displacements per atom) and 400 �C (Ref 15). Inaddition, the radiation-induced hardening increased up to450 �C when the irradiation hardening began to saturate (Ref15). The irradiation-hardening saturation depends solely onboth irradiation temperature and dose; however, the highirradiation temperature is more important (Ref 16). Forinstance, the in situ irradiation work conducted by Topbasi et al.(Ref 10) on Grade 92 steel showed that defect cluster densityincreases with dose and saturates when reaching around 6 dpa.Also, the low temperature range (�200 �C) does not influenceeither the average size or distribution of irradiation-induceddefect clusters at that low temperature range (Ref 10). On theother hand, the irradiation damage assessment at elevatedtemperatures (290-500 �C) showed that small precipitates andvoids were created. Also, the segregation of strengtheningelements (Cr and W) near voids was more pronounced at highertemperatures (Ref 16).

As discussed above, the F-M steels are potential candidatesto be employed in the advanced reactors. However, furtherunderstanding needs to be gained. . The 9Cr-2W F-M steel hasshown much potential for some in-core and out-of-coreapplications in advanced reactors (Ref 18). In this work, thefocus was on studying microstructural evolutions in 9Cr-2W

Sultan Alsagabi, Department of Chemical and Materials Engineering,University of Idaho, Moscow, ID 83844 and King Abdulaziz City forScience and Technology, P.O. Box 6086, Riyadh 11442, Saudi Arabia;and Indrajit Charit and Somayeh Pasebani, Department of Chemicaland Materials Engineering, University of Idaho, Moscow, ID 83844.Contact e-mail: dr.alsagabi@gmail.com.

JMEPEG (2016) 25:401–408 �ASM InternationalDOI: 10.1007/s11665-015-1841-2 1059-9495/$19.00

Journal of Materials Engineering and Performance Volume 25(2) February 2016—401

steel at different radiation doses induced by iron ions (10, 50,and 100 dpa) and temperatures (30 and 500 �C). Also, thenanoindentation experiments were carried out to assess theextent of radiation damage.

2. Experimental Procedure

The investigated material was procured from the TianjinTiangang Weiye Steel Co., China in the form of cylindrical barswith a diameter of 14 mm and has the nominal composition asshown in Table 1. The procured steel was in F92 condition inaccordance with the ASTM A182 and normalized at atemperature between 1040 and 1080 �C and tempered at atemperature between 730 and 800 �C according to the ASTMA182 standard. The actual details of the processing conditionsare proprietary by the company, and hence are not available.Optical metallography samples were prepared using conven-tional grinding/polishing techniques followed by etching withAqua Regia to examine under a light microscope.

Polished mirror-like surface samples, with 14-mm diameter,were prepared for irradiation with iron ions (Fe+2). For thatpurpose, IoneX 1.7 MV Tandetron accelerator with SNICSsputter ion source at Texas A&M Ion Beam Laboratory wasemployed. Irradiation was conducted at temperatures of 30 and500 �C. At 30 �C, samples were attached to an electricallyisolated stage by double-sided copper tape which can read thebeam current directly via a current integrator. At elevatedtemperature, samples were mounted using silver paint to aheated stage, and the temperature was measured by a thermo-couple near the edge of the stage. A Firestick-type resistanceheater was used to heat the samples. The temperature differencebetween the center and the edge of the stage was controlledprecisely, and temperature calibration was performed to checkif there is any difference. At elevated temperature, the stageemits electrons when it is heated, and the current cannot bedirectly measured. However, as a result of the high stability ofthe sputter source, a current measurement was taken from theFaraday cup directly in front of the sample stage every �20 minwhich gives accurate results.

In order to extract Fe ions, the sputter ion source is started tomaximum power after turning the ionizer which has a tungstenfilament with ceramic coating. Heating process has to beconducted slowly as the thermal expansion of tungsten relativeto ceramic coating is different. After that, the filament startsproducing electrons once it is hot. In order to extract the ionspecies from the target cathode (pure Fe 99.95%), variousvoltages are needed. Figure 1 shows the implantation beam lineand the hot stage at the Texas A&M Ion Beam Laboratory usedin this study.

The displacement per atom (dpa) was measured based on thepeak damage level in sample, and a peak damage dose of 10,50, and 100 dpa was achieved using a fluence of 5.869 1015,2.939 1016, and 5.869 1016 ion/cm2. The radiation damageprofile (i.e., dpa versus depth) shown in Fig. 2 was estimatedusing the Stopping and Range of Ions in Matter (SRIM)2008.04 software.

Afterward, the samples were prepared for TEM using aFocused Ion Beam (FIB) Quanta 3D Field Emission GunScanning Electron Microscope. Before milling the sample, theirradiated surface was protected with a Pt deposition layer.Then, sample milling was conducted for each condition to

Table 1 The chemical composition of the received Grade92 steel

Element Composition (wt.%)

C 0.09P 0.015S 0.001Mo 0.55V 0.19N 0.045Ni 0.12W 1.66B 0.003Cr 8.68Mn 0.42Si 0.34Al 0.02Nb 0.079Fe Bal.

Fig. 1 The IoneX 1.7 MV Tandetron accelerator at the Texas A&M Ion Beam Laboratory showing (a) the implantation beam line and (b) thehot stage

402—Volume 25(2) February 2016 Journal of Materials Engineering and Performance

deliver a sample with thickness less than 100 nm using FocusedIon Beam. For the detailed microstructural characterization, aTF30-FEG Transmission Electron Microscope with STEMmode was employed. In order to investigate, the FIBed sampleswere attached to a copper TEM grid. The dislocation density ofinvestigated samples was estimated, while the samples wereoriented in a two-beam condition and also the electron energyloss spectrum (EELS) technique was applied to estimate thesample thickness.

Finally, the hardness measurement as a function of depthwas conducted using Hysitron Nanoindenter model TI-950TriboIndenter. The Nanoindenter was employed to induce apenetration depth profile of 1000 nm using a pyramidaldiamond tip with an included angle of 142.35�, Berkovich tiptype. The depth profile of hardness measurement was con-ducted via multi-cycling indentation technique. For eachcondition, more than 10 arrays of indentations were collectedfor accuracy in order to estimate the damage profile.

3. Results and Discussion

3.1 As-received Condition

The microstructure of the as-received Grade 92 steel isshown in Fig 3 and 4. Figure 3 shows the optical microstruc-ture of the typical tempered martensite structure. Figure 4shows the bright-field TEM microstructure of the as-receivedGrade 92 steel. The microstructure shows a lightly temperedferritic-martensitic (F-M) structure with high-dislocation den-sity. The elongated lath structure was more dominant. Thedislocation density of the as-received condition was measuredto be approximately 3.9± 0.89 1014 m�2.

3.2 Nanoindentation Results

Figure 5 shows the hardness data as a function of inden-tation depth for different conditions. More than 10 arrays oftesting were performed for each condition to ensure theaccuracy of testing. Hardness was measured for samplesirradiated at room temperature (30 �C) and elevated tempera-

ture (500 �C). The ion irradiation was conducted to createdamage doses of 10, 50, and 100 dpa.

The irradiated samples at room temperature (30 �C) showedan evident hardening phenomenon; thus, the hardness increasedas the dose increased. At high irradiation temperature (500 �C),the irradiation hardening was less pronounced. The hardnesswas found to be lower at high temperatures when comparing tothe obtained hardness profiles. Clearly, the higher irradiationdose conditions had higher hardness especially in the nearsurface region, which is less than 300 nm. However, the 10 dpaand 500 �C condition showed higher hardness near surfaceregion than 50 dpa and 500 �C.

The induced hardening after irradiation was reported forF-M steels and other iron-based alloys (Ref 19-23). In the workby Liu et al. (Ref 19), the 16MND5 steel was irradiated usingproton (to 0.5 dpa) and iron-ion irradiation (to 1.37 dpa). Theproton irradiation created more hardening as a result of smallcluster damage (and higher dispersion) associated with theproton irradiation damage (Ref 19). However, ion or neutronirradiation induces damage in large clusters resulting in lowerhardiness as a result of the dispersion of the large defects (Ref19). Also, the irradiation-hardening characteristics of two F-M

Fig. 4 TEM micrograph of the as-received Grade 92 steel

Fig. 2 The radiation damage profile, displacement per atom (dpa)versus depth Fig. 3 The optical microscopy of the as-received Grade 92 steel

Journal of Materials Engineering and Performance Volume 25(2) February 2016—403

steels (i.e., HCM12A and T91) were compared by Allen et al.(Ref 24) at 400 and 500 �C. The hardening of those irradiatedsteels showed gradual decrease as irradiation temperatureincreased (Ref 24). The induced hardening was attributed tothe microstructural defects such as the interstitial and vacancyclusters, and dislocation loops (Ref 19-23). Thus, as theirradiation temperature increases, the recovery of the irradia-tion-induced defects occurred at higher rates leading to lowerhardness (Ref 19-23).

3.3 Microstructural Evolution in Irradiated Samples

Figure 6 shows a series of bright-field images of theirradiated samples for different conditions. According to theestimated damage profile, the maximum damage would occur at1 lm. However, it should be noted that dose level is different atvarying depths and will not be constant as a function of depth;however, the damage profile should be constant across thesurface of the samples (Ref 25). These images basically showan overview of the FIBed TEM samples without giving anyspecific details on radiation damage.

To understand any damage in detail, higher magnificationTEM images of the samples irradiated at 30 �C are shown inFig. 7. These irradiated samples did not display any irradiation-induced precipitates, resolvable loops, and voids. However, theirradiated samples showed the presence of irradiation-induceddefect clusters appearing as �dots� and the overall concentrationof these clusters increased as the dose increased. The highdensity of induced clusters in the form of dots did not appearbeyond the irradiated area. The unirradiated area did not show

any form of such clusters which confirm the fact that theseclusters in the irradiated area were not created as artifacts byFIBing.

The irradiation-induced damage enhances the conglomera-tion of the induced defects which form within the displacementcascade (Ref 25). The defect clusters can migrate away fromthe cascade if they become stable; however, the variousmicrostructure defects such as dislocations and grain bound-aries can act as sinks where these clusters might be absorbed(Ref 25). As the irradiation dose increases, the irradiation-induced cluster formation becomes more pronounced . Forinstance, the irradiation-induced clusters were formed at lowerdose (i.e., around 2.5 dpa) in NF616 steel and their size did notchange at higher temperature (i.e., 200 �C) as demonstrated byTopbasiet al. (Ref 10). The defect cluster density in irradiatedNF616 steel showed similar behavior where cluster densityincreased as the dose increased (Ref 10). However, the defectcluster’s saturation density decreases as temperature increasedto 200 �C which was attributed to the limited mobility ofclusters at that temperature (200 �C) as shown by Topbasi et al.(Ref 10). The defect clusters were not influenced by thermaldefect migration; as a result, defect clusters were believed to becreated and destroyed directly in the cascade events at highertemperature (Ref 10).

Samples irradiated at higher temperature (i.e., 500 �C) didnot show any voids or cavities. However, some dislocationloops were found in the sample irradiated at 50 dpa at 500 �C,as shown in Fig. 8. For instance, the irradiation-inducedvacancies and interstitials give raise to dislocation loops asthey can shrink or grow depending on the irradiation flux

Fig. 5 The hardness profile as a function of depth for Grade 92 steel irradiated at (a) 10 dpa and 30 �C, (b) 50 dpa and 30 �C, (c) 100 dpa and30 �C, (d) 10 dpa and 500 �C, (e) 50 dpa and 500 �C, and (f) 100 dpa and 500 �C

404—Volume 25(2) February 2016 Journal of Materials Engineering and Performance

(Ref 25). The irradiation-induced interstitials form the disloca-tion loops, while the irradiation-induced vacancies agglomerateinto platelets which collapse to form dislocation loops. At

higher irradiation temperature, the irradiation-induced disloca-tion loops become more stable as they grow in size reachingcritical size. After that, they remain stable within themicrostructure and they might interact with other loops or withthe dislocation networks.

The dislocation density of the irradiated sample wasinvestigated at the two-beam condition via TEM, as shown inFigure 9. First, the irradiated samples showed denser disloca-tion density than the unirradiated condition. In addition, thedislocation structure showed a gradual increase in the disloca-tion density as the dose increased to 30 �C. For instance, thedislocation density of the irradiated sample increased as thedose increased from 10 to 100 dpa at 30 �C from 4.39 1014 to5.39 1014 m�2, respectively. At higher irradiation temperature(500 �C), the dislocation structure of the irradiated samples wasless dense than those at 30 �C. Nevertheless, the dislocationstructure of irradiated samples was denser than the unirradiatedconditions.

Figure 10 shows the quantitative dislocation density of theinvestigated samples. At 30 �C, the dislocation densityincreased from 3.99 1014 m�2 for the unirradiated conditionto reach 4.39 1014, 4.79 1014, and 5.39 1014 m�2 for samples

Fig. 7 Irradiated microstructure at 30 �C and (a) 10 dpa, (b) 50 dpa, and (c) 100 dpa

Fig. 8 Dislocation loops in samples irradiated at 50 dpa and500 �C

Fig. 6 Irradiated microstructure of different conditions: (a) 10 dpa and 30 �C at 2.9 kx, (b) 50 dpa and 30 �C at 2.9 kx, (c) 100 dpa and 30 �Cat 2.9 kx, (d) 10 dpa and 500 �C at 2.9 kx, (e) 50 dpa and 500 �C at 5.9 kx, and (f) 100 dpa and 500 �C at 5.9 kx

Journal of Materials Engineering and Performance Volume 25(2) February 2016—405

irradiated at 10, 50, and 100 dpa, respectively. The ionimplantation enhances the formation of high-dislocation density(Ref 25). For instance, the dislocation density increased as aresponse to the high surface stresses caused by the high dose ofimplanted surfaces during the ion implantation processes.

At higher temperature (500 �C), it should be noted that thedislocation density of the unirradiated condition was estimatedfrom the unirradiated region of the 100 dpa and 500 �Ccondition. The irradiated sample at 10 dpa and 500 �C wassubjected to less irradiation time at higher temperature (i.e.,500 �C), which could explain the higher dislocation densitycompared to the irradiated conditions at 50 dpa and 100 dpa at500 �C. Also, it should be noted that the dislocation densities atelevated temperature yield comparable results indicating theannealing effect while irradiating the sample at elevatedtemperature.

The presence of small black dots was revealed by TEM inP92 steel (irradiated to 34.5 dpa at room temperature), (Ref 16,26). The density of these black dots increased as temperatureincreased and/or dose increased as they enhance the solute atomdiffusivity which via radiation-enhanced diffusion. The elementsegregation becomes more pronounced by the radiation-en-hanced diffusion which might explain these small dots (Ref 16,26). However, the current investigated steel (Grade 92 steel) did

not show such black dots even at higher dose of 50 and 100 dpaat 30 and 500 �C. Moreover, the work by Topbasi et al. (Ref10) did not report any such observation (i.e., small precipitatesor dots) besides the irradiation-induced defect clusters in thesample irradiated at 200 �C up to 7.6 dpa (Ref 10).

The investigated sample did not show any cavities such asbubble or void at 30 and 500 �C. It should be noted that theelevated temperature is defined as a crucial factor for the voidformation. The current investigation was conducted at 30 and500 �C, which might suggest that the investigated temperatureswere insufficient for atom mobility to nucleate and form voidsas the low-defect mobility limits the growth of such defects. Forexample, the irradiated Grade 91 steel irradiated at lowtemperature with mixed proton, and neutron spectra did notshow any void formation (Ref 27). As the irradiation temper-ature was raised to 550 �C in the work by Klueh and Vitek (Ref17), some very small voids were observed in P92 steel at 7 dpa(void swelling rate �0.03%) and these voids remained verysmall even at a higher dpa of 12 (void swelling rate �0.044%).It should be noted that other F-M steels exhibited some voids athigher temperatures (Ref 28-31). For example, F82H steel hadvoids formed at a temperature of 470 �C and P92 steel showedsome voids at 550 �C (Ref 16, 30). In brief, the investigatedGrade 92 steel in the current work did not show any voids at500 �C even when irradiated to 100 dpa. Finally, the rasteringmode of ion irradiation employed in this study tends to produceno significant void formation if at all under this type of doselevel.

The selected area diffraction patterns in samples irradiatedto 100 dpa at 30 and 500 �C are shown in Figure 11. Thesepatterns contain typical bright diffraction spots without anyfaint diffraction rings. Hence, the irradiated samples did notshow any sign of amorphization. The definite amorphizationof Grade 92 was obtained by (Ref 26) at higher dose (230dpa) at room temperature, where the amorphization wasevidenced by the loss of diffraction contrast and theappearance of amorphous halos (Ref 26). However, in thecurrent work, the maximum dose was 100 dpa and theinvestigated samples did not show any irradiation-inducedamorphization at that dose. At temperature above 230 �C,Grade 92 steel is not expected to undergo any amorphizationand it can undergo amorphization below that temperature onlyat sufficiently high doses (Ref 26, 32, 33). At elevatedtemperatures, the induced annealing action at high temperaturereduces the lattice disorder (Ref 26, 32, 33).

Fig. 10 The dislocation density of the investigated samples for dif-ferent conditions

Fig. 9 The two-beam condition of irradiated sample at (a) 10 dpa and 30 �C, (b) 50 dpa and 500 �C, and (c) 100 dpa and 500 �C

406—Volume 25(2) February 2016 Journal of Materials Engineering and Performance

4. Conclusion

The heavy ion irradiation damage experiments in Grade 92as a result of iron-ion irradiation were conducted to 10, 50, and100 dpa at 30 and 500 �C, respectively, in the present study.The study provided a largely qualitative description of themicrostructural evolution and consequent hardening effects dueto the irradiation effects. The microstructural evolution of theirradiated samples and the nanoindentation hardness data wasinvestigated to assess the irradiation-induced damage. The mainresults are summarized below:

1. The irradiation-induced hardening was obvious and hard-ness increased as dose increased at 30 �C. But, the irradi-ation-induced hardening was less definite at elevatedtemperature (500 �C) as defect annihilation mechanismbecame more pronounced. This was accompanied by thehigher dislocation density of samples irradiated at 30 �C.

2. The irradiated samples at 30 �C showed the presence ofirradiation-induced defect clusters to appear as dots in theirradiated area and the density of these clusters increasedas the dose increased. At higher temperature (500 �C),some dislocation loops were found in the samples irradi-ated at 50 dpa and 500 �C.

3. The investigated sample did not show any cavities suchas bubble or void under the irradiation test parameters.

Acknowledgments

The authors gratefully acknowledge the assistance of Dr. YaqiaoWu, Ms. Jatuporn Burns, Ms. Joanna Taylor, and Mr. BryanForsmann at the Microscopy and Characterization Suite (MaCS)facility of the Center for Advanced Energy Studies (CAES). Thework was partly supported by the U.S. Department of Energy, OfficeofNuclear Energy underDOE IdahoOperationsOfficeContract DE-AC07-05ID14517, as a part of Advanced Test Reactor NationalScientific User Facility (ATR NSUF) experiments. Acknowledge-ment is also extended to Mr. Lloyd M. Price and Dr. Lin Shao at theDepartment of Nuclear Engineering, Texas A&M University fortheir help in carrying out the ion irradiation tests.

References

1. R.L. Klueh, R. Donald, and R. Harries, High-Chromium Ferritic andMartensitic Steels for Nuclear Applications, 1st ed., Conshohocken,PA, 2001

2. M. Yurechko, C. Schroer, A. Skrypnik, O. Wedemeyer, and J. Konys,Creep-to-Rupture of the Steel P92 at 650 �C in Oxygen-ControlledStagnant Lead in Comparison to Air, J. Nucl. Mater., 2013, 432, p 78–86

3. F. Abe, T. Horiuchi, M. Taneike, and K. Sawada, Stabilization ofMartensitic Microstructure in Advanced 9Cr Steel During Creep atHigh Temperature, Mater. Sci. Eng. A, 2004, 378, p 299–303

4. R.L. Klueh and J.M. Vitek, Tensile Properties of 9Cr-1MoVNb and12Cr-1MoVW Steels Irradiated to 23 dpa at 390 to 550 �C, J. Nucl.Mater., 1991, 182, p 230–239

5. G.S. Was, P. Ampornrat, G. Gupta, S. Teysseyre, E.A. West, T.R. Allenet al., Corrosion and Stress Corrosion Cracking in Supercritical Water,J. Nucl. Mater., 2007, 371, p 176–201

6. S. Alsagabi, T. Shrestha, and I. Charit, High Temperature TensileDeformation Behavior of Grade 92 Steel, J. Nucl. Mater., 2014, 453,p 151–157

7. R.L. Klueh and P.J. Maziasz, The Microstructure of Chromium-Tungsten Steels, Metall. Mater. Trans. A, 1989, 20A, p 373–382

8. R.L. Klueh and A.T. Nelson, Ferritic/Martensitic Steels for NextGeneration Reactors, J. Nucl. Mater., 2007, 371, p 37–52

9. F. Abe, Strengthening Mechanisms in Creep of Advanced FerriticPower Plant Steels Based on Creep Deformation Analysis, AdvancedSteels: The Recent Scenario in Steel Science and Technology,Metallurgical Industry, Y. Weng, D. Hand, Eds., 2011, p 409–422

10. C. Topbasi, A.T. Motta, and M. Kirk, In Situ Study of Heavy ionInduced Radiation Damage in NF616 (P92) alloy, J. Nucl. Mater.,2012, 425, p 48–53

11. K. Sawada, M. Takeda, K. Murayama, R. Ishii, M. Yamada, Y. Nygae,and R. Komine, Effect of W on the Recovery of Lath Structure DuringCreep of High Chromium Martensitic Steels, Metall. Mater. Trans. A,1999, 267, p 19–25

12. Horsten, M., Osch, M., Gelles, D.S., Hamilton, M.L., Effects ofIrradiation on Materials: 19th International Symposium, ASTM STP1366, M.L. Hamilton, A.S. Kumar, S.T. Rosinski, M.L. Grossbeck,Eds., American Society for Testing and Materials, 2000, p 579–593

13. M.A. Kirk, P.M. Baldo, A.C.Y. Liu, E.A. Ryan, R.C. Birtcher, Z. Yao,S. Xu, M.L. Jenkins, M. Hernandez-Mayoral, D. Kaoumi, and A.T.Motta, In Situ Transmission Electron Microscopy and Ion Irradiation ofFerritic Materials, Microsc. Res. Tech., 2009, 72, p 182–186

14. S.X. Jin, L.P. Guo, Z. Yang, D.J. Fu, C.S. Liu, R. Tang et al.,Microstructural Evolution of P92 Ferritic/Martensitic Steel UnderArgon Ion Irradiation, Mater. Charact., 2011, 62, p 136–142

15. R.L. Klueh, J.J. Kai, and D.J. Alexander, Microstructure-MechanicalProperties Correlation of Irradiated Conventional and Reduced-Acti-vation Martensitic Steels, J. Nucl. Mater., 1995, 225, p 175–186

16. S. Jin, L. Guo, T. Li et al., Microstructural Evolution of P92 Ferritic/Martensitic STEEL Under Ar Ion Irradiation at Elevated Temperature,Mater. Charact., 2012, 68, p 63–70

17. R.L. Klueh and J.M. Vitek, Elevated-Temperature Tensile Properties ofIrradiated 9Cr-1MoVNb Steel, J. Nucl. Mater., 1985, 132, p 27–31

18. E.I. Samuel, B.K. Choudhary, D.P. Rao Palaparti, and M.D. Mathew,Creep Deformation and Rupture Behaviour of P92 Steel at 923 K,Procedia Eng., 2013, 55, p 64–69

19. X. Liu, R. Wang, A. Ren et al., Evaluation of Radiation Hardening inIon-Irradiated Fe Based Alloys by Nanoindentation, J. Nucl. Mater.,2014, 444, p 1–6

Fig. 11 The selected area diffraction patterns of Grade 92 matrix irradiated to 100 dpa at (a) 30 and (b) 500 �C

Journal of Materials Engineering and Performance Volume 25(2) February 2016—407

20. C. Heintze, C. Recknagel, F. Bergner, M. Hernandez-Mayoral, and A.Kolitsch, Ion-Irradiation-Induced Damage of Steels Characterized byMeans of Nanoindentation, Nucl. Instrum. Methods B, 2009, 267,p 1505–1508

21. R. Kasada, Y. Takayama, K. Yabuuchi, and A. Kimura, A NewApproach to Evaluate Irradiation Hardening of Ion Irradiated FerriticAlloys by Nano-indentation Techniques, Fusion Eng. Des., 2011, 86,p 2658–2661

22. K. Katoh and M. Ando, Radiation and Helium Effects on Microstruc-tures, Nano-indentation Properties and Deformation Behavior inFerrous Alloys, J. Nucl. Mater., 2003, 323, p 251–262

23. P. Hosemann, C. Vieh, R.R. Greco, S. Kabra, J.A. Valdez, M.J.Cappiello, and S.A. Maloy, Nanoindentation on Ion Irradiated Steels,J. Nucl. Mater., 2009, 389, p 239–247

24. T.R. Allen, L. Tan, J. Gan, G. Gupta, G.S. Was, E.A. Kenik, S.Shutthanandan, and S. Thevuthasan, Microstructural Development inAdvanced Ferritic–Martensitic Steel HCM12A, J. Nucl. Mater., 2006,351, p 174–186

25. G. Was, Fundamentals of Radiation Materials Science: Metals andAlloys, 1st ed., Springer, Berlin, 2007

26. S.X. Jin, L.P. Guo, Z. Yang, D.J. Fu, C.S. Liu, R. Tang et al.,Microstructural evolution of P92 ferritic/martensitic steel under argonion irradiation, Mater. Charact., 2001, 62, p 136–142

27. B.H. Sencer, F.A. Garner, D.S. Gelles, G.M. Bond, and S.A. Maloy,Microstructural Evolution in Modified 9Cr-1Mo Ferritic/MartensiticSteel Irradiated with Mixed High-Energy Proton and Neutron Spectraat Low Temperatures, J. Nucl. Mater., 2002, 307, p 266–271

28. C.H. Zhang, K.Q. Chen, Y.S. Wang, J.G. Sun, B.F. Hu, Y.F. Jin et al.,Microstructural Changes in a Low-Activation Fe-Cr-MnAlloy Irradiatedwith 92 MeVAr Ions at 450 �C, J. Nucl. Mater., 2000, 283, p 259–262

29. C.H. Zhang, J. Jang, M.C. Kim, H.D. Cho, Y.T. Yang, and Y.M. Sun,Void Swelling in a 9Cr Ferritic/Martensitic Steel Irradiated withEnergetic Ne-Ions at Elevated Temperatures, J. Nucl. Mater., 2008,375, p 185–191

30. E. Wakai, T. Sawai, K. Furuya, A. Naito, T. Aruga, K. Kikuchi et al.,Effect of Triple Ion Beams in Ferritic/Martensitic Steel on SwellingBehavior, J. Nucl. Mater., 2002, 307, p 278–282

31. F. Zhao, J. Qiao, Y. Huang, F. Wan, and S. Ohnuki, Effect of IrradiationTemperature on Void Swelling of China Low Activation MartensiticSteel (CLAM), J. Nucl. Mater., 2008, 59, p 344–347

32. H. Tanigawa, H. Sakasegawa, H. Ogiwara, H. Kishimoto, and A.Kohyama, Radiation Induced Phase Instability of Precipitates inReduced-Activation Ferritic/Martensitic Steels, J Nucl. Mater., 2007,367, p 132–136

33. X. Jia and Y. Dai, Microstructure in Martensitic Steels T91 and F82HAfter Irradiation in SINQTarget-3, J. Nucl.Mater., 2003, 318, p 207–214

408—Volume 25(2) February 2016 Journal of Materials Engineering and Performance