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Li, J.-F.*; Kawai, Masayoshi*; Kikuchi, Kenji; Igarashi, Tadashi*; Kurishita, Hiroaki*; Watanabe, Ryuzo*; Kawasaki, Akira*
Journal of Nuclear Materials, 321(2-3), p.129 - 134, 2003/09
Times Cited Count：14 Percentile：66.77(Materials Science, Multidisciplinary)For the development of tantalum-clad tungsten targets for spallation neutron sources, the bonding strength of tantalum-tungsten interface was investigated by means of an easy-to-use and miniaturized small punch (SP) test, in which a punching load is vertically applied to the center of a jointed disk. Cracks initiated and propagated in the tungsten side for all the samples hot-isostatically pressed (HIPed) at temperatures from 1673 to 2073 K, whereas nocrack and debonding were observed in the interface, indicating that the jointed interface is strongly bonded. The re-crystallization of tungsten occurs and results in its strength reduction, consequently the crack-initiating load decreases with HIPing temperature. The finite element analysis of the measured SP testing results shows that the maximum bonding strength can exceed 1000 MPa. The present study shows that SP test is suitable for the strength evaluation of jointed tantalum-tungsten interfaces.
Kawai, Masayoshi*; Furusaka, Michihiro*; Kikuchi, Kenji; Kurishita, Hiroaki*; Watanabe, Ryuzo*; Li, J.*; Sugimoto, Katsuhisa*; Yamamura, Tsutomu*; Hiraoka, Yutaka*; Abe, Katsunori*; et al.
Journal of Nuclear Materials, 318, p.35 - 55, 2003/05
R&D works for MW class solid target composed of tungsten to produce pulsed intense neutron source has been made in order to construct a future scattering facility. Three methods were investigated to prevent corrosion of tungsten from water; those are hipping, brazing and electric coating in molten salt bath. Hipping condition was optimized to be 1500 degree C in the previous work: here small punch test shows highest load for crack initiation of hipped materials at the boundary of W/Ta. The basic techniques for the other two methods were developed. Erosion test showed that uncovered W is susceptible of flowing water velocity. At high velocity w is easy to be eroded. For solid target design slab type and rod type targets were studied. As long as the optimized neutron performance is concerned, 1MW solid target is better than mercury target.
Kawai, Masayoshi*; Li, J.*; Watanabe, Ryuzo*; Kurishita, Hiroaki*; Kikuchi, Kenji; Igarashi, Tadashi*; Kato, Masahiro*
Dai-23-Kai Nihon Netsu Bussei Shimpojiumu Koen Rombunshu, p.313 - 315, 2002/11
The objective of the present study is to develop the stainless-steel-bonded tungsten alloys by powder metallurgy processes. Commercially available tungsten powders and stainless steel (SUS304L) powder were used as the raw materials and mixed by ball milling at the ratios of 97mass% W -3% SUS and 93mass% W -7mass% SUS. Powder compacts were formed by die pressing and cold isostatic pressing (CIP), then sintered mainly in vacuum at the temperatures above the melting point of the stainless steel phase. Some samples were fabricated by glass-encapsulated hot isostatic pressing (HIPing) at lower temperatures. The microstructural observation was made by scanning electron microscopy (SEM). The thermal properties of the produced alloy and various tungsten materials supplied from Allied Material Corp. was measured with the laser-frash method. It was found that stable liquid-phase-sintered microstructures were not easily formed in the tungsten-stainless steel system. The electron probe microanalysis (EPMA) revealed that tungsten was considerably dissolved in the stainless steel phase during sintering. Therefore, thermal conductivity of the W/7 mass% SUS alloy was 22.8-53.5 W/m/K that was very lower than theoretical value calculated from those of pure tungsten and stainless steel. Its temperature dependence is resembled to that of stainless steel, i.e., thermal conductivity increased with the specimen temperature as like stainless steel. The diffusivity of pure tungsten is compared with those of tungsten alloys.
Watanabe, Ryuzo*
PNC TJ9601 98-005, 85 Pages, 1998/03
To fabricate a long life fuel cladding tubes for the fast breeder reactor, the concept of functionally graded material was applied for the material combination of molybdenum/stainless steel/ titanium, in which titanium is placed at the inner side to withstand against fission products and neutron irradiation, and molybdenum at the outer side to withstand corrosion by liquid sodium coolant. Slurry dipping method was employed for the processing because of its capability of shape forming and microstructural control. The graded layers of titanium and molybdenum were formed on both sides of stainless steel substrate according to an optimum composition profile for the thermal stress reduction. Such graded layers were successfully formed by slurry dipping. Dispersion, sedimentation, viscosity, rheology, as well as yield value, of the slurries were investigated in detail inconnection with properties of dispersion medium, dispersion reagent, binder and raw powders. Low- and high-viscosity slurries were investigated to enlarge a possibility of film thickness control. For the low-viscosity slurry it is necessary to suppress the sedimentation of dispersion particles, while for the high-viscosity slurry it turned out to be important to clarify the flow characteristics of the slurry for the determination of the yield value, which is needed for the precise control of the dip-coated layer thickness. The forming conditions were determined for the low-viscosity slurry in taking sedimentation rate and sedimentation height as measures of slurry stability and dispersion, respectively. It was confirmed that slow sedimentation and low sedimentation height gave reproducible film forming. The high-viscosity slurry was free from sedimentation, and the control of the film thickness with viscosity and yield value was rather easier. The consolidation Process of the dip-coated layer, including drying and debinding, followed conventional powder metallurgical techniques, with particular ...
Watanabe, Ryuzo*
PNC TJ9601 98-004, 79 Pages, 1997/03
In order to obtain long life fuel cladding tubes for the fast breeder reactor, the concept of functionally graded material was applied for the material combination of Molybdenum/stainless steel/ Titanium, in which Titanium and Molybdenum were placed at the inner and outer sides, respectively. Slurry dipping method was employed because of its capability of shape forming and microstructural control. We have hitherto reported the design criteria for the graded layers, preparation of the slurry, and microstructural control of the dip-coated layers. In the present report, the thickness control of the dip-coated layer is described in detail. The thickness of the dip-coated layer depends primarily on the viscosity of the slurry. Nevertheless, for the stable dispersion of the powder in the slurry, which dominates the microstructural homogeneity, an optimum viscosity value is present for the individual slurries. With stable slurries of Ti, Mo, stainless steel powders and their mixtures, the thicknesses of dip-coated layers were controlled in dependence of their viscosities and yield values. For Ti and stainless steel powders and their mixture a PAANa was used as a dispersing agent. A NaHMP was found to be effective for the dispersion of Mo powder and Mo/stainless steel powder mixture. For all slurries tested in the present investigation PVA addition was helpful for the viscosity control. Dip-coating maps have been drawn for the stabilization of the slurries and for the formation of films with a sufficient strength for further manipulation for the slurries with low viscosity (
10 mPas). The final film thickness for the low-viscosity slurry with the optimum condition was about 200
m. The slurries with high viscosities of several hundreds mPa s had a good stability and the yield value was easy to be controlled. The film thickless was able to be adjusted in the size range between several tens and several hundreds m. The final thickness of the graded layer ...
Watanabe, Ryuzo*; *
PNC TJ9601 96-002, 91 Pages, 1996/03
This report is the PNC contract research for year of 1995 titled "Formation of Ti/SUS/Mo graded layer by slurry dipping". Fuel cladding material for FBR is used under a severe envimnment. The life of conventionally used SUS316 is known to be only two years. The development of long-life core material having high temperature strength, radiation resistance and corrosion resistance property is now essential. To create a super-long-life core materials for FBR it seems promising to employ the concept of functionally graded materials, in which these different materials are configurated with grading: as base material is used SUS316 stainless steel, the inner wall is made of Ti for the radiation resistance and corrosion resistance property against the fusion products with graded intermediated layers towards the base metal and the outer shell is the graded Mo layer for the corrosion resistance against liquid sodium. In this year, the formation of the graded inner layer of Ti/SUS316 as well as the graded outer layer of Mo/SUS316 by slurry dipping was investigated. Prior to fabricate the FGM layers, optimization of slurry was discussed. The key point of slurry dipping process is to prevent the particle settling in a slurry during dipping and to control the thickness of dip-formed layers on a substrate. In this study, on the basis of the stabilization mechanism of particles in a slurry, the concentration of dispersant and binder in a slurry has been optimized so as to prevent the particle settling. Then, the viscosity of a slurry has been presented as a function of powder and binder concentration in the slurry, in which Mori-Ototani's viscosity equation is mainly considered. The use of this viscosity equation allows us to show the relation between the slurry composition (Powder and binder concentration) and the thickness of dip-formed layer. According to the relation presented as processing maps, FGMs have been fabricated, in which the thickness of the layers and the ...
Watanabe, Ryuzo*; *
PNC TJ9601 95-003, 122 Pages, 1995/03
Molybdenum/stainless steel/Titanium functionally gradient material (FGM), which will be used as long life fuel cladding tubes in the fast breeder reactor, has been fabricated by slurry dipping and sintering process emphasizing the increase in corrosion resistance to liquid sodium and fission products. The formation procedure is briefly mentioned here as follows. Cylindrical green compacts of SUS304 stainless steel powder and Al
O
powder was prepared by die compaction and CIP as a substrate for slurry dipping. Mo, SUS, Ti powder was suspended in pure water with binder and milled by tumbler ball mill to get a slurry having an appropriate viscosity for dipping. The substrate was dipped in the slurry then withdrawn and dried. This procedure was repeated with slurries of different compositions to get a graded layer. After drying, the coated sample was debinded binder. The formed compacts were HIP-sintered, and subjected to microstructural analysis, EPMA, and hardness test. The thermal stress analysis was done by FEM to evaluate the bonding characteristics. The main results are listed below. (1)Slurry dipping process is available for forming functionally graded layer on the inner and outer surface of a cylinder-type substrate. Slurry viscosity determines the thickness of coating layer and yield strength of slurry determines the homogeneity of the thickness of the coating. Selection of sort of binder and dispersant and optimization of the slurry holds a key to form the homogeneous coating layer. (2)It is shown that in the HIPed samples, a single layered coating debonded at the bonding interface, while a good bonding was obtained in the case of the graded coating. However, the sample fabricated on a substrate of SUS powder component was delaminated in the interface between the dipped layer and substrate owing to the high residual thermal stress. The use of the AlO green compact as a substrate, which has the same heat expansion coefficient of ...
Watanabe, Ryuzo*; *
PNC TJ9601 94-003, 87 Pages, 1994/03
This report is the PNC contract research for fiscal year of 1993 titled "Formation of Ti/SUS/Mo graded layer by slurry dipping." Fuel sheath material for FBR is used under a severe enviroment. The life of conventionally used SUS316 is known to be only two years. The development of long-life core material having high temperature strength, radiation resistance and anti-corrosion property is now essential. To create a super-long-life core materials for FBR it seems promising to employ the concept of functionally gradient material, in which these different materials are configurated with grading : as base material is used SUS316 stainless steel, the inner wall is made of Ti for the radiation resistant and anti-corrosion property with graded intermediate layers towards the base metal and the outer shell is the graded Mo layer for the corrosion resistance against liquid sodium. The shape of the core tube is a long cylindrical tube and its dimensions are 8.5mm in outer diameter, about 2m in length, shell thickness is 0.5mm and the thickness of the gradient layer is about 0.1mm. However, we have not yet acquired sufficient techniques to realize such shape and dimmensions, and the investigation is planned to get basic informations on the processing of the core materials with graded structures. Slurry dipping has been employed for forming a graded layer on curved inner and outer surfaces. And it is indispensable that the graded layers have showed sufficient thermal-stress relief function, as well as good bonding capability. In this year (FY 1993), the formation of the graded inner layer of Ti/SUS316 by slurry dipping was investigated. The formation procedure is briefly mentioned here as follows. Cylindrical green compacts of SUS304 stainless steel powder was prepared by die compaction and CIP as a substrate for slurry dipping. A coarse Ti powder was suspended in ethanol and milled by tumbler ball mill to get a slurry having an appropriate viscosity for dipping. The ...
*; Watanabe, Ryuzo*
PNC TJ9601 93-004, 68 Pages, 1993/03
Molybdenum/stainless steel functionally gradient material (FGM). which will be used as long life fuel cladding tubes in the fast breeder reactor, has been fabricated by slurry dipping and sintering process emphasizing the increase in unti-corrosion against liquid sodium and fission products. Slurries of different compositions were prepared by mixing the appropriate amount of molybdenum and stainless steel powders in the ethanol. Green compacts giving cylindrical shape, substrates. were formed by die pressing of stainless steel powders. The substrates were dipped in the slurry, dried in the air and CIP'ed stepwizely: they were encapsulated in Pyrex glass tubes and then HIP'ed 2h at 1573K at the pressure of 150MPa. The microstructural observation in the cross section of the sintered compacts revealed that the uniform dipped layer was formed and there was no defect such as large residual pores or small cracks. A defect free Mo/stainless steel FGM was successfully fabricated by the slurry dipping and sintering process, however, in the case of single phase coating of Mo layer on the stainless steel substrate, the serious delamination was observed. Some oxides and compounds were detected in the FGM layer by the use of SEM-EDX and EPMA analysis.
Saito, Shigeru; Kikuchi, Kenji*; Hamaguchi, Dai; Suzuki, Kazuhiro; Endo, Shinya; Obata, Hiroki; Kurishita, Hiroaki*; Watanabe, Ryuzo*; Kawai, Masayoshi*; Yong, D.*
no journal, ,
no abstracts in English
