WO2012023265A1 - Thermal neutron-blocking material and method for producing same - Google Patents

Thermal neutron-blocking material and method for producing same Download PDF

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Publication number
WO2012023265A1
WO2012023265A1 PCT/JP2011/004539 JP2011004539W WO2012023265A1 WO 2012023265 A1 WO2012023265 A1 WO 2012023265A1 JP 2011004539 W JP2011004539 W JP 2011004539W WO 2012023265 A1 WO2012023265 A1 WO 2012023265A1
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Prior art keywords
boride
cermet layer
cermet
mass
thermal neutron
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PCT/JP2011/004539
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French (fr)
Japanese (ja)
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山崎　裕司
浩郎 平田
裕記 矢永
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東洋鋼鈑株式会社
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Priority claimed from JP2010183484A external-priority patent/JP2012042317A/en
Priority claimed from JP2010183395A external-priority patent/JP2012042314A/en
Application filed by 東洋鋼鈑株式会社 filed Critical 東洋鋼鈑株式会社
Publication of WO2012023265A1 publication Critical patent/WO2012023265A1/en

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    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
    • G21F1/00—Shielding characterised by the composition of the materials
    • G21F1/02—Selection of uniform shielding materials
    • G21F1/08—Metals; Alloys; Cermets, i.e. sintered mixtures of ceramics and metals
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
    • G21F1/00—Shielding characterised by the composition of the materials
    • G21F1/12—Laminated shielding materials
    • G21F1/125—Laminated shielding materials comprising metals
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
    • G21F5/00—Transportable or portable shielded containers

Definitions

  • the present invention relates to a thermal neutron shielding material having a cermet layer on a metal base material and a manufacturing method thereof.
  • Patent Document 1 discloses that a glaze containing 10 to 20 wt% of gadolinium oxide and boron oxide is applied to a metal surface such as stainless steel by coating, baking or spraying. A thermal neutron shielding material used for a spent nuclear fuel storage container, a fuel transport container material, etc. is described.
  • Patent Document 1 when an oxide of boron (B) or gadolinium (Gd) having high neutron absorption capability is deposited on the metal surface by thermal spraying, an oxide simple substance such as boron oxide and gadolinium oxide, so-called ceramics, Since the thermal spray coating is formed by plasma spraying at a high temperature (about 6000 ° C.), when the thermal spray particles collide with the base material, a large tensile stress is generated in the coating due to solidification / shrinkage caused by cooling. Not only a high adhesion can not be obtained, but also a film thickness of 0.05 mm or more cannot be obtained.
  • the thermal spray coating of an oxide which is difficult to plastically deform has a problem that a fine coating cannot be obtained because microcracks and voids are unavoidable in the coating.
  • the storage container for storing the spent nuclear fuel and the fuel transport container may be exposed to an atmosphere such as salt water or water at the time of transportation or storage, so that there is a problem that corrosion resistance is necessary. Therefore, the present invention provides a thermal neutron shielding material having good corrosion resistance and higher thermal neutron shielding ability by forming a B-containing cermet layer having good adhesion to the metal matrix on the metal surface, and a method for producing the same. The purpose is to provide.
  • the thermal neutron shielding material according to claim 2 is characterized in that, in claim 1, the cermet layer further includes a binary boride.
  • the thermal neutron shielding material according to claim 3 is characterized in that, in claim 1, the cermet layer is a double boride cermet made of a bonded phase of an M2M′B2 type double boride and an M ′ based alloy.
  • the thermal neutron shielding material according to claim 4 is the cermet layer according to claim 3, wherein the cermet layer is composed of 35 to 95% by mass of a hard phase made of a double boride and a binder phase of a Ni-based alloy in which the balance binds the hard phase.
  • the B content is 3 to 7.5% by mass
  • the Mo content is 0.8 to (1.6-0.05X) in terms of Mo / B atomic ratio (X:% by mass of B contained, The same applies to the following X notation), characterized in that the Cr content is (55-5X)% or less, the balance is Ni of 10% by mass or more, and unavoidable impurities.
  • the B content is 3 to 7.5% by mass
  • the Mo content is 0.8 to (1.6-0.05X) in terms of Mo / B atomic ratio
  • the Cr and / or Ni content is The total of either one or both is (55-5X)% by mass or less
  • the C content is 0.95% by mass or less
  • the balance is 10% by mass or more Fe, and unavoidable impurities. .
  • the thermal neutron shielding material according to claim 6 is characterized in that, in any one of claims 1 to 5, the metal base material is ordinary steel, alloy steel, tool steel, stainless steel or aluminum alloy.
  • a method for producing a thermal neutron shielding material according to claim 7 is the method for producing a thermal neutron shielding material according to any one of claims 1 to 6, wherein the cermet layer is formed on a metal base material by thermal spraying. It is characterized by that.
  • the cermet in this specification means the composite material of a metal and a ceramic.
  • the thermal neutron shielding material of the present invention has a cermet layer formed on a metal base material such as ordinary steel, alloy steel, tool steel, stainless steel, and aluminum alloy, and the cermet layer has a hard phase composed of double boride and the balance Is a double boride cermet comprising a binder phase that binds a hard phase.
  • the cermet layer can be formed on the surface of ordinary steel, alloy steel, stainless steel or aluminum alloy currently used to improve the thermal neutron shielding ability and improve safety, and to reduce the thickness.
  • storage density of spent nuclear fuel can be increased.
  • the thermal neutron shielding material of the present invention has sufficient corrosion resistance to an atmosphere such as salt water or water during transportation or storage.
  • the thermal neutron shielding material according to Embodiment 1 of the present invention has a cermet layer formed on a metal base material, and MM′B or M 2 M′B 2 (M, M ′) is formed on the metal base material.
  • M, M ′ Transition metal
  • the cermet layer further includes a binary boride.
  • B is an indispensable element for forming the ternary boride in the cermet layer, and is contained in an amount of 3 to 7.5% by mass in the cermet layer.
  • the B content is less than 3% by mass, the amount of ternary boride formed is small and the ratio of hardness in the structure is small, so that sufficient hardness and wear resistance of the obtained cermet layer can be imparted. Can not.
  • it exceeds 7.5% by mass the hardness increases but the strength (toughness and thermal shock resistance) of the cermet layer is lowered. Therefore, the B content in the cermet layer is 3 to 7.5% by mass. Since the formed cermet layer contains ternary boride, it has excellent neutron shielding ability.
  • Preferred combinations of the ternary boride and the metal bonded phase are a combination of a Mo 2 FeB 2 type boride and an Fe-based alloy, a combination of a W 2 FeB 2 type boride and an Fe-based alloy, and a Mo 2 NiB 2 type boride. And a combination of a W 2 NiB 2 type boride and a Ni base alloy, and a combination of a WCoB type boride and a Co base alloy.
  • the cermet material combining Mo 2 FeB 2 type boride and Fe-based alloy is excellent in wear resistance and relatively inexpensive, and the cermet material combining W 2 FeB 2 type boride and Fe-based alloy is further Abrasion resistance is improved.
  • the cermet material combining the Mo 2 NiB 2 type boride and the Ni base alloy is excellent in wear resistance, corrosion resistance, and heat resistance, and the cermet material combining the W 2 NiB 2 type boride and the Ni base alloy is further Abrasion resistance is improved.
  • a cermet material combining a WCoB type boride and a Co-based alloy is excellent in heat resistance.
  • W or Ta can be substituted with Mo in an arbitrary ratio.
  • Mo and Ta can be substituted with W at an arbitrary ratio.
  • Fe, Ni, Cr, and Co can be replaced with Fe, Ni, and Co in the cermet at an arbitrary ratio, and characteristics such as corrosion resistance and heat resistance can be controlled.
  • the amount of ternary boride contained in the cermet layer is preferably in the range of 12 to 95% by mass based on the entire cermet layer.
  • the amount of the ternary boride is less than 12% by mass, sufficient neutron shielding ability cannot be obtained.
  • the amount of ternary boride exceeds 95% by mass, the metal phase with high plastic deformability decreases, and the amount of ceramics increases, resulting in defects such as pores in high-speed flame spraying, resulting in a dense sprayed coating. It cannot be obtained, and excellent adhesion with the metal base material cannot be obtained. Therefore, the ratio of the double boride in the cermet layer is desirably 12 to 95% by mass.
  • a binary boride to the ternary boride cermet.
  • the binary boride include B 4 C, AlB 12 , ZrB 12 , YB 12 , FeB, and NiB.
  • the ratio of the M ′ metal phase in the cermet layer is 5% by mass or more.
  • the proportion of the metal phase is less than 5% by mass, the metal phase having high plastic deformability decreases in the cermet layer, and the amount of ceramics increases, resulting in defects such as pores in high-speed flame spraying, resulting in a dense film. This is because defects that cannot be obtained and excellent adhesion cannot be easily obtained.
  • Table 1 The compositions of these binary borides are shown in Table 1.
  • the thickness of the cermet layer in the thermal neutron shielding material of Embodiment 1 is preferably 0.05 to 5 mm.
  • a dense coating is formed in the thermal spraying layer by collision of new powder particles on the sprayed coating that has already been formed. For this reason, when the thickness of the thermal spray layer is less than 0.05 mm, the thickness of the thermal spray coating is thin and a dense thermal spray layer cannot be obtained.
  • the thickness of the thermal spray layer exceeds 5 mm, the thickness of the thermal spray coating is Therefore, the residual stress in the thermal spray coating is increased and cracks are likely to occur in the thermal spray coating, and a thermal neutron shielding material having good corrosion resistance and high thermal neutron shielding capability cannot be obtained. Therefore, the thickness of the cermet layer in the thermal neutron shielding material is preferably 0.05 to 5 mm.
  • the thermal spray powder is adjusted so that the cermet layer is blended, and a thermal spray gun is formed on a metal base material such as ordinary steel, alloy steel, tool steel, stainless steel, or aluminum alloy. And is formed by spraying to a predetermined thickness.
  • a metal base material such as ordinary steel, alloy steel, tool steel, stainless steel, or aluminum alloy.
  • M, M ' transition metal type ternary boride powder, binary boride powder, and M' metal powder in the spraying powder charging container of the spray gun. It is preferable that the thermal spraying is performed in the atmosphere by applying the high-speed flame spraying method.
  • the high-speed flame spraying method forms a thermal spray layer at a relatively low temperature among the thermal spraying techniques, so it can be suitably used for cermet materials and double boride cermets, can reduce tensile residual stress in the thermal spray coating, High adhesion can be obtained.
  • the cermet layer of Embodiment 1 includes a metal phase having a high plastic deformability, it has very few defects such as pores, a dense film is obtained, and has excellent adhesion. In addition, when high-speed flame spraying is used, the composition fluctuation of the material can be suppressed and excellent corrosion resistance can be exhibited.
  • ⁇ Particle size of sprayed powder As the particle size of the sprayed powder, a particle size of 15 to 100 ⁇ m can be usually used in the plasma spraying method, but when the high-speed flame spraying is used, a particle size of about 20 to 60 ⁇ m is preferable. When the particle size of the sprayed powder is coarse, it is difficult to form a dense cermet layer, and defects such as pores are easily formed in the cermet layer, and the hardness is lowered. On the other hand, when the particle size of the thermal spray powder becomes fine, the fluidity of the thermal spray powder decreases and the thermal spray workability is impaired.
  • Example 1 to 14 Examples will be described below, and the first embodiment will be described in more detail.
  • Table 2 shows the M2M′B2 type ternary boride, M ′ metal phase, boride content, metal phase content, and composition (wt%) in the cermet layer of the cermet layers formed in Examples 1 to 14.
  • the ratio of M2M′B2 type ternary boride and M ′ metal phase of the thermal spray powder was adjusted so that the cermet layer composition shown in Table 2 was obtained, and the cermet was formed on the metal base material. Form a layer.
  • Comparative Example 1 was obtained by setting the hard phase to 100% and the metal phase to 0%. Note that a tool steel (SKD) test piece is used as the metal base material for thermal spraying in Examples 1 to 14.
  • SSD tool steel
  • the spray powder is blended with the raw material powder so as to have the composition of the cermet layers of the compositions of Examples 1 to 14 shown in Table 2, and wet pulverized with a ball mill.
  • the wet pulverized powder is granulated with a spray dryer and held at 1150 ° C. for 1 hour to cause M 2 M′B 2 type ternary boride, which becomes a hard phase, and M ′ metal phase to react.
  • the formed M 2 M′B 2 type ternary boride and M ′ metal phase are classified to complete a sprayed powder having a size of 20 to 60 ⁇ m for forming a cermet layer.
  • shot (white alumina # 20) is used for the surface layer of the metal base material on which the cermet layer is formed, and the surface of the metal base material is roughened.
  • the prepared raw material powder is sprayed to form a cermet layer having a composition of Examples 1 to 14 having a thickness of 0.3 mm on the SKD steel base material.
  • the sprayer used was a high-speed flame sprayer (JP-5000 manufactured by PRAXAIR / TAFA), which forms a cermet layer under the following conditions.
  • Thermal spray distance (distance between substrate and thermal spray gun): 380 mm
  • Oxygen flow rate 1900 scfh Kerosene flow rate: 5gph
  • Example 15 Table 3 shows the MM′B type ternary boride, M ′ metal phase, boride content, metal phase content, and composition (wt%) in the cermet layer of the cermet layer formed in Example 15.
  • M ′ metal phase, boride amount, metal phase amount, and composition (wt%) in the cermet layer The same applies to other conditions such as the manufacture of metal, metal base material, and thermal spraying conditions.
  • Example 2 and Comparative Example 1 of Embodiment 1 shown in Table 2 the adhesion of the cermet layer formed on the surface of the metal base material was evaluated.
  • the adhesion evaluation was performed using a torsion tester.
  • the test method was performed by preparing a test piece that can be attached to a torsion tester, fixing one end of the test piece, and rotating the other end (see FIG. 1).
  • the torque value when peeling or cracking occurred in the cermet layer by rotation was defined as the adhesion of the cermet layer.
  • the adhesion strength of Example 2 showed a large and high value, but Comparative Example 1 showed a low torque value. The results are shown in Table 4.
  • the thermal neutron shielding material of the second embodiment is the same as that of the first embodiment in that a cermet layer is formed on a metal base material, but the cermet layer includes a hard phase composed of a double boride, The balance consists of a binder phase that binds the hard phase. That is, a double boride cermet comprising a M2M′B2 type double boride and a bonded phase of an M′-based alloy.
  • M Mo
  • M ′ Ni or Fe.
  • the cermet layer is composed of 35 to 95% by mass of a hard phase made of a double boride, and the balance is a Ni-base alloy or Fe-base alloy binder phase that binds the hard phase.
  • B content is 3 to 7.5% by mass
  • Mo content is 0.8 to (1.6-0.05X) in terms of Mo / B atomic ratio
  • Cr content is (55-5X) mass% or less
  • the balance is 10% by mass or more of Ni and unavoidable impurities.
  • the binder phase can be changed to an Fe-based alloy instead of the Ni-based alloy.
  • the cermet layer has a hard phase of 35 to 95% by mass made of double boride, and the balance is the hard alloy.
  • a Fe-phase binder phase that binds the phases B content is 3 to 7.5% by mass, Mo content is 0.8 to (1.6-0.05X) in terms of Mo / B atomic ratio, Cr and / or Ni content is not more than (55-5X) mass% in any one or both, C content is 0.05 to 0.95% by mass or less,
  • the balance consists of 10 mass% or more of Fe and inevitable impurities.
  • B is an indispensable element for forming a double boride in the cermet layer, and is contained in an amount of 3 to 7.5% by mass in the cermet layer.
  • the B content is less than 3% by mass, the formation of double borides is small and the ratio of the hard phase in the structure is small, so that sufficient hardness and wear resistance of the obtained cermet layer can be imparted. Can not.
  • it exceeds 7.5% by mass the hardness increases but the strength (toughness and thermal shock resistance) of the cermet layer is lowered. Therefore, the B content in the cermet layer is 3 to 7.5% by mass. Since the formed cermet layer contains double borides, the neutron shielding ability is excellent.
  • Mo is an indispensable element for forming a boride that becomes a hard phase like B.
  • a part of Mo is dissolved in the binder phase to improve the mechanical properties and wear resistance of the alloy, and to improve the corrosion resistance to a reducing atmosphere.
  • Mo 2 NiB 2 type or Mo 2 FeB 2 type double boride has a stoichiometric ratio of Mo to B of 1: 1, but is not actually a complete stoichiometric compound and has a composition range of several percent. Therefore, the atomic ratio of Mo / B (hereinafter abbreviated as Mo / B ratio) does not have to be 1, but it is important that the Mo / B atomic ratio is within a certain range around 1.
  • M ′ 5 B 3 type such as Cr 5 B 3 is different from Mo 2 NiB 2 type double boride.
  • Others such as M ′′ 3 B type (M ′: mainly composed of Ni, including Cr, Mo, etc.) such as boride and Ni 3 B (M ′: mainly composed of Cr, including Mo, Ni, etc.) Boride is formed as the third phase, and the strength of the cermet layer is significantly reduced.
  • Mo / B ratio is larger than (1.6-0.05X)
  • a Mo—Ni-based intermetallic compound is formed as the third phase, and the strength of the cermet layer is reduced.
  • Mo 2 FeB 2 type double boride cermet when the Mo / B ratio is smaller than 0.8, Fe boride such as Fe 2 B, which is different from Mo 2 FeB 2 type double boride, is formed. In addition to a decrease in wear resistance and corrosion resistance, the strength of the cermet layer is decreased. When the Mo / B ratio exceeds (1.6-0.05X), the amount of carbides such as M 6 C and M 23 C 6 (M represents a metal) and the formation of intermetallic compounds between Fe-Mo increase. This causes a decrease in strength.
  • Ni is an essential element for forming the double boride in the cermet layer and is the main element constituting the binder phase, like B and Mo. It is desirable to contain 10% by mass or more in the cermet layer. When the Ni content is less than 10% by mass, a sufficient liquid phase does not appear at the time of spraying, a dense sprayed layer cannot be obtained, and the strength is significantly reduced. This is because if the Ni content in the binder phase is small, the bond strength with the double boride is weakened, the strength of the binder phase is lowered, and consequently the strength of the cermet layer is lowered.
  • Cr may be added to replace Ni.
  • Cr is an element constituting a double boride by substitutional solid solution with Ni in the double boride in the cermet layer.
  • the added Cr also dissolves in the binder phase, and has the effect of greatly improving the corrosion resistance, wear resistance, high temperature characteristics, and mechanical characteristics of the cermet layer.
  • borides such as Cr 5 B 3 are formed and the strength is lowered.
  • Fe is an essential element for forming the double boride in the cermet layer and is the main element constituting the binder phase, like B and Mo. It is desirable to contain 10% by mass or more in the cermet layer. When the Fe content is less than 10% by mass, a sufficient liquid phase does not appear at the time of spraying, a dense sprayed layer cannot be obtained, and the strength is significantly reduced. This is because if the amount of Fe in the binder phase is small, the bond strength with the double boride is weakened, the strength of the binder phase is lowered, and consequently the strength of the cermet layer is lowered.
  • Ni or / and Cr may be added to replace Fe.
  • Ni or / and Cr show the effect of improving the corrosion resistance and oxidation resistance of the cermet layer.
  • the mechanical properties and wear resistance can be reduced by arbitrarily controlling the binder phase to martensite, ferrite, austenite and their mixed phase structure.
  • the content of Ni or / and Cr is added exceeding 35% by mass in the case of containing alone or in combination, the corrosion resistance and heat resistance are very excellent, but the strength is lowered. Therefore, the content of Ni or / and Cr is preferably (55-5X) mass% in terms of the total amount when contained alone or in combination.
  • the inevitable impurities and other elements contained in the process for producing the thermal spraying powder of the second embodiment may be contained in a very small amount so as not to impair the properties of the cermet layer. It is.
  • the Mo 2 FeB 2 type complex boride cermet has a role of reducing the oxide of the powder surface. Some of them are dissolved in the binder phase to improve the hardness. If the content is less than 0.05% by mass, the effect is small, and if it exceeds 1% by mass, the formation of carbides is promoted and the strength of the cermet layer tends to decrease. Moreover, it leads also to a fall of corrosion resistance. Therefore, the C content is desirably 0.05 to 1% by mass.
  • the amount of double boride contained in the cermet layer is preferably in the range of 35 to 95% by mass of the entire sprayed layer.
  • the amount of the double boride is less than 35% by mass, sufficient neutron shielding ability cannot be obtained.
  • the amount of the double boride exceeds 95% by mass, the binder phase having high plastic deformability decreases, and the amount of ceramics increases, so that defects such as pores are generated by thermal spraying, and a dense thermal spray coating cannot be obtained. An excellent adhesion with a metal base material cannot be obtained. Therefore, the ratio of the double boride in the cermet layer is desirably 35 to 95% by mass.
  • the thickness of the thermal spray layer in the thermal neutron shielding material of the second embodiment is the same as that of the first embodiment.
  • the thermal neutron shielding material according to the second embodiment is formed by adjusting the thermal spraying powder so that the cermet layer is blended, and using a thermal spray gun on the metal base material and spraying it to a predetermined thickness.
  • the particle size of the thermal spray powder in the second embodiment is the same as that in the first embodiment.
  • Example 16 will be shown below, and the second embodiment will be described in more detail.
  • Table 5 shows the composition of the cermet layer formed in Example 16 and the ratio between the boride and the bonding layer of the formed cermet layer.
  • the cermet layer was formed on the metal base material by adjusting the ratio of the double boride of the thermal spraying raw material powder and the metal powder as the binder phase so as to have the cermet layer composition shown in Table 5.
  • a stainless steel (SUS316L) test piece was used as the metal base material for thermal spraying.
  • the thermal spray powder was first blended with the raw material powder so as to have the thermal spray layer composition of Example 16 in Table 5, and wet pulverized with a ball mill.
  • the wet pulverized powder was granulated with a spray dryer and held at 1150 ° C. for 1 hour to form an M 2 M′B 2 type double boride which becomes a hard phase by reaction.
  • the formed M 2 M′B 2 type double boride cermet was classified to complete a sprayed powder having a size of 20 to 60 ⁇ m for forming a cermet layer.
  • shot white alumina # 20
  • the prepared raw material powder was sprayed to form a cermet layer having a composition of Example 16 having a thickness of 0.3 mm on the base material.
  • the thermal spraying machine and thermal spraying conditions used are the same as those in the first embodiment.
  • Comparative Example 2 For comparison, a sprayed layer formed using only a double boride that does not form a binder phase (not a cermet) as a thermal spraying powder is shown as Comparative Example 2 (see Table 5).
  • Comparative Example 2 the raw material powder for thermal spraying is different from that of Example 16, but the same is true for other conditions such as thermal spraying conditions.
  • Example 16 of Comparative Example 2 and Comparative Example 2 the adhesion of the thermal spray layer formed on the surface of the metal base material was evaluated.
  • the adhesion evaluation was performed using a torsion tester.
  • the test method was performed by preparing a test piece that can be attached to a torsion tester, fixing one end of the test piece, and rotating the other end (see FIG. 1).
  • the torque value when peeling or cracking occurred in the sprayed layer by rotation was defined as the adhesion of the sprayed layer.
  • the adhesion strength of Example 16 was large and high, while Comparative Example 2 showed a low torque value. The results are shown in Table 6.
  • the thermal neutron shielding material of the present invention is a high-hardness material, a material excellent in corrosion resistance and wear resistance, and has a thin wall thickness while maintaining excellent corrosion resistance and thermal neutron shielding properties. And storage density of spent nuclear fuel can be increased. Furthermore, the thermal neutron shielding material of the present invention has sufficient corrosion resistance to the atmosphere of salt water, water, etc. during transportation and storage of spent nuclear fuel, and can be widely applied to members that require thermal neutron shielding. The above availability is extremely high.

Abstract

[Problem] To provide a thermal neutron-blocking material having good corrosion resistance and stronger thermal neutron-blocking performance as a result of a B-containing cermet layer, which has good adhesion with a base metal, being formed on a metal surface. [Solution] A thermal neutron-blocking material in which a cermet layer is formed on a metal base material such as ordinary steel, steel alloy, tool steel, stainless steel, aluminum alloy, etc., wherein the cermet layer is formed from an MM'B or M2M'B2-type ternary boride and an M' metal phase (M, M' = transition metal). In addition, the cermet layer further comprises a binary boride. Furthermore, the cermet layer is a compound boride-type cermet formed from an M2M'B2-type compound boride and a binder phase of an M'-based alloy (M = Mo, M' = Ni or Fe).

Description

熱中性子遮蔽材料及びその製造方法Thermal neutron shielding material and manufacturing method thereof
　本発明は、金属母材上にサーメット層を有する熱中性子遮蔽材料及びその製造方法に関する。 The present invention relates to a thermal neutron shielding material having a cermet layer on a metal base material and a manufacturing method thereof.
　最近の環境、エネルギー問題の観点からＣＯ２を排出しない原子力発電による電力供給の増加が予想される。
　使用済み核燃料の貯蔵容器や燃料輸送容器（キャスク）等には熱中性子吸収能の高い材料が使用されるが、原子力発電の稼動増加により、使用済み核燃料の貯蔵密度を増加させる必要がある。
　核燃料の収容能力を高めるためには、容器の肉厚を薄くする必要があり、より熱中性子吸収能に優れる材料が求められている。 From the viewpoint of recent environmental and energy problems, an increase in power supply by nuclear power generation that does not emit CO 2 is expected.
Materials with high thermal neutron absorption capacity are used for spent nuclear fuel storage containers, fuel transport containers (casks), etc., but it is necessary to increase the storage density of spent nuclear fuel due to increased operation of nuclear power generation.
In order to increase the nuclear fuel storage capacity, it is necessary to reduce the wall thickness of the container, and a material with better thermal neutron absorption capacity is required.
　その一例として、使用済み核燃料を貯蔵する保管容器や燃料輸送容器を構成する材料として、熱中性子吸収能が大きいボロン（Ｂ）を添加したステンレス鋼やアルミニウム合金が提案されているが、Ｂの添加量が増加すると熱中性子遮蔽能は向上するが、熱間加工性を低下させるという問題点があり、Ｂの添加量は１％程度が上限とされていた。
　Ｂの添加量を増加させるため、特許文献１には、ステンレス鋼などの金属表面に、酸化ガドリニウムと酸化ボロンの含有量が各々１０～２０ｗｔ％である琺瑯剤を、塗布、焼き付け又は溶射により付着させた、使用済み核燃料の保管容器や燃料輸送容器材料などに用いる熱中性子遮蔽材料が記載されている。 As an example, stainless steel and aluminum alloy to which boron (B) having a large thermal neutron absorption capacity is added have been proposed as a material constituting a storage container for storing spent nuclear fuel and a fuel transport container. When the amount is increased, the thermal neutron shielding ability is improved, but there is a problem that the hot workability is lowered, and the upper limit of the addition amount of B is about 1%.
In order to increase the amount of B added, Patent Document 1 discloses that a glaze containing 10 to 20 wt% of gadolinium oxide and boron oxide is applied to a metal surface such as stainless steel by coating, baking or spraying. A thermal neutron shielding material used for a spent nuclear fuel storage container, a fuel transport container material, etc. is described.
特許第３７８９６７８号公報Japanese Patent No. 3789678
　しかし、特許文献１において、中性子吸収能の高いボロン（Ｂ）またはガドリニウム（Ｇｄ）の酸化物を溶射で金属表面に付着させる場合には、酸化ボロン、酸化ガドリニウムといった酸化物単体、いわゆるセラミックスが、高温（約６０００℃）のプラズマ溶射で溶射皮膜を形成するため、溶射粒子は基材に衝突する際に、冷却に伴う凝固・収縮によって皮膜には大きな引張応力が発生し、金属母材との高い密着力が得られないばかりでなく、０．０５ｍｍ以上の膜厚が得られない。
　また、塑性変形しにくい酸化物の溶射皮膜は、皮膜中にはマイクロクラックの発生、空隙（ポア）の残存が避けられないため、緻密な皮膜が得られない、という問題点がある。
さらに、使用済み核燃料を貯蔵する保管容器や燃料輸送容器は、輸送時や保管時には塩水、水等の雰囲気に曝される場合があるため耐食性が必要であるという課題もある。
　そこで、本発明は、金属表面に、金属母材との密着性のよいＢ含有サーメット層を形成することにより、良好な耐食性とより高い熱中性子遮蔽能を持つ熱中性子遮蔽材料及びその製造方法を提供することを目的とする。 However, in Patent Document 1, when an oxide of boron (B) or gadolinium (Gd) having high neutron absorption capability is deposited on the metal surface by thermal spraying, an oxide simple substance such as boron oxide and gadolinium oxide, so-called ceramics, Since the thermal spray coating is formed by plasma spraying at a high temperature (about 6000 ° C.), when the thermal spray particles collide with the base material, a large tensile stress is generated in the coating due to solidification / shrinkage caused by cooling. Not only a high adhesion can not be obtained, but also a film thickness of 0.05 mm or more cannot be obtained.
In addition, the thermal spray coating of an oxide which is difficult to plastically deform has a problem that a fine coating cannot be obtained because microcracks and voids are unavoidable in the coating.
Furthermore, the storage container for storing the spent nuclear fuel and the fuel transport container may be exposed to an atmosphere such as salt water or water at the time of transportation or storage, so that there is a problem that corrosion resistance is necessary.
Therefore, the present invention provides a thermal neutron shielding material having good corrosion resistance and higher thermal neutron shielding ability by forming a B-containing cermet layer having good adhesion to the metal matrix on the metal surface, and a method for producing the same. The purpose is to provide.
　上記課題を解決するために、
請求項１に記載の熱中性子遮蔽材料は、金属母材上にサーメット層を有する熱中性子遮蔽材料であって、前記サーメット層が、ＭＭ’Ｂ又はＭ２Ｍ’Ｂ２（Ｍ，Ｍ’＝遷移金属）型三元硼化物と、Ｍ’金属相と、からなるサーメットであることを特徴とする。
　請求項２に記載の熱中性子遮蔽材料は、請求項１において、前記サーメット層が、二元硼化物をさらに有することを特徴とする。
　請求項３に記載の熱中性子遮蔽材料は、請求項１において、前記サーメット層が、Ｍ２Ｍ’Ｂ２型複硼化物とＭ’基合金の結合相よりなる複硼化物サーメットであることを特徴とする（Ｍ＝Ｍｏ，Ｍ’＝ＮｉまたはＦｅ）。
　請求項４に記載の熱中性子遮蔽材料は、請求項３において、前記サーメット層は、複硼化物よりなる硬質相３５～９５質量％と、残部が該硬質相を結合するＮｉ基合金の結合相とからなり、Ｂ含有量が３～７．５質量％、Ｍｏ含有量が、Ｍｏ／Ｂ原子比で０．８～（１．６－０．０５Ｘ）（Ｘ：含有するＢの質量％、以下のＸ表記において同じ）、Ｃｒ含有量が（５５－５Ｘ）％以下、残部が１０質量％以上のＮｉ、および不可避的不純物よりなることを特徴とする。
　請求項５に記載の熱中性子遮蔽材料は、請求項３において、前記サーメット層は、複硼化物よりなる硬質相３５～９５質量％と、残部が該硬質相を結合するＦｅ基合金の結合相とからなり、Ｂ含有量が、３～７．５質量％、Ｍｏ含有量が、Ｍｏ／Ｂ原子比で０．８～（１．６－０．０５Ｘ）、Ｃｒおよび／又はＮｉ含有量が、いずれか一方または両者の合計で（５５－５Ｘ）％質量以下、Ｃ含有量が、０．９５質量％以下、残部が１０質量％以上のＦｅ、および不可避的不純物よりなることを特徴とする。
　請求項６に記載の熱中性子遮蔽材料は、請求項１～５のいずれかにおいて、前記金属母材は、普通鋼、合金鋼、工具鋼、ステンレス鋼又はアルミニウム合金であることを特徴とする。
　請求項７に記載の熱中性子遮蔽材料の製造方法は、請求項１～６のいずれかに記載の熱中性子遮蔽材料の製造方法であって、前記サーメット層を金属母材上に溶射によって形成することを特徴とする。
　なお、本明細書におけるサーメットとは、金属とセラミックの複合材料を意味する。 To solve the above problem,
The thermal neutron shielding material according to claim 1 is a thermal neutron shielding material having a cermet layer on a metal base material, wherein the cermet layer is MM′B or M 2 M′B 2 (M, M ′ = A cermet comprising a transition metal) type ternary boride and an M ′ metal phase.
The thermal neutron shielding material according to claim 2 is characterized in that, in claim 1, the cermet layer further includes a binary boride.
The thermal neutron shielding material according to claim 3 is characterized in that, in claim 1, the cermet layer is a double boride cermet made of a bonded phase of an M2M′B2 type double boride and an M ′ based alloy. (M = Mo, M ′ = Ni or Fe).
The thermal neutron shielding material according to claim 4 is the cermet layer according to claim 3, wherein the cermet layer is composed of 35 to 95% by mass of a hard phase made of a double boride and a binder phase of a Ni-based alloy in which the balance binds the hard phase. The B content is 3 to 7.5% by mass, the Mo content is 0.8 to (1.6-0.05X) in terms of Mo / B atomic ratio (X:% by mass of B contained, The same applies to the following X notation), characterized in that the Cr content is (55-5X)% or less, the balance is Ni of 10% by mass or more, and unavoidable impurities.
The thermal neutron shielding material according to claim 5, wherein the cermet layer is composed of 35 to 95% by mass of a hard phase made of a double boride and a binder phase of an Fe-based alloy in which the remainder binds the hard phase. The B content is 3 to 7.5% by mass, the Mo content is 0.8 to (1.6-0.05X) in terms of Mo / B atomic ratio, and the Cr and / or Ni content is The total of either one or both is (55-5X)% by mass or less, the C content is 0.95% by mass or less, the balance is 10% by mass or more Fe, and unavoidable impurities. .
The thermal neutron shielding material according to claim 6 is characterized in that, in any one of claims 1 to 5, the metal base material is ordinary steel, alloy steel, tool steel, stainless steel or aluminum alloy.
A method for producing a thermal neutron shielding material according to claim 7 is the method for producing a thermal neutron shielding material according to any one of claims 1 to 6, wherein the cermet layer is formed on a metal base material by thermal spraying. It is characterized by that.
In addition, the cermet in this specification means the composite material of a metal and a ceramic.
　本発明の熱中性子遮蔽材料は、普通鋼、合金鋼、工具鋼、ステンレス鋼、アルミニウム合金などの金属母材上にサーメット層を形成させ、サーメット層は、複硼化物よりなる硬質相と、残部が硬質相を結合する結合相と、からなる複硼化物サーメットである。
　前記サーメット層は、ＭＭ’Ｂ又はＭ２Ｍ’Ｂ２（Ｍ，Ｍ’＝遷移金属）型三元硼化物、Ｍ’金属相、を含有するか、Ｍ２Ｍ’Ｂ２型複硼化物とＭ’基合金の結合相とよりなる複硼化物サーメット（ここでＭ＝Ｍｏ，Ｍ’＝ＮｉまたはＦｅ）であるので、熱中性子遮蔽材料として良好な耐食性および高い熱中性子遮蔽能を有している。
　また、現在使用されている普通鋼、合金鋼、ステンレス鋼又はアルミニウム合金の表面に、上記サーメット層を形成して熱中性子遮蔽能を向上させて安全性を高めることができ、肉厚を薄くすることが可能となり、使用済核燃料の貯蔵密度を増加することができる。
　さらに、本発明の熱中性子遮蔽材料は、輸送時や保管時には塩水、水等の雰囲気に対する十分な耐食性を有している。 The thermal neutron shielding material of the present invention has a cermet layer formed on a metal base material such as ordinary steel, alloy steel, tool steel, stainless steel, and aluminum alloy, and the cermet layer has a hard phase composed of double boride and the balance Is a double boride cermet comprising a binder phase that binds a hard phase.
The cermet layer contains MM′B or M 2 M′B 2 (M, M ′ = transition metal) type ternary boride, M ′ metal phase, or M 2 M′B 2 type double boride. And a boride cermet (here, M = Mo, M ′ = Ni or Fe) composed of a binder phase of an M′-based alloy and having good corrosion resistance and high thermal neutron shielding ability as a thermal neutron shielding material ing.
In addition, the cermet layer can be formed on the surface of ordinary steel, alloy steel, stainless steel or aluminum alloy currently used to improve the thermal neutron shielding ability and improve safety, and to reduce the thickness. And storage density of spent nuclear fuel can be increased.
Furthermore, the thermal neutron shielding material of the present invention has sufficient corrosion resistance to an atmosphere such as salt water or water during transportation or storage.
金属母材とサーメット層との密着性を評価する試験方法についての概略説明図である。It is a schematic explanatory drawing about the test method which evaluates the adhesiveness of a metal base material and a cermet layer.
［実施の形態１］
　本発明の実施の形態１の熱中性子遮蔽材料は、金属母材上にサーメット層を形成させたものであり、金属母材上に、ＭＭ’Ｂ又はＭ２Ｍ’Ｂ２（Ｍ，Ｍ’＝遷移金属）型三元硼化物と、Ｍ’金属相と、からなるサーメット層を有することを特徴とする。
　また、熱中性子遮蔽材料は、前記サーメット層が、二元硼化物をさらに有することを特徴とする。
　また、熱中性子遮蔽材料は、前記サーメット層が、Ｍ２Ｍ’Ｂ２型複硼化物とＭ’基合金の結合相よりなる複硼化物サーメットであることを特徴とする（Ｍ＝Ｍｏ，Ｍ’＝ＮｉまたはＦｅ）。
　金属母材表面に形成させる前記サーメット層は、金属粉末として溶射することができる。 [Embodiment 1]
The thermal neutron shielding material according to Embodiment 1 of the present invention has a cermet layer formed on a metal base material, and MM′B or M 2 M′B 2 (M, M ′) is formed on the metal base material. = Transition metal) type ternary boride and an M ′ metal phase, and has a cermet layer.
In the thermal neutron shielding material, the cermet layer further includes a binary boride.
Further, the thermal neutron shielding material is characterized in that the cermet layer is a double boride cermet comprising a bonded phase of M2M′B2 type double boride and an M ′ based alloy (M = Mo, M ′ = Ni Or Fe).
The cermet layer formed on the surface of the metal base material can be sprayed as a metal powder.
　Ｂは、本サーメット層中の三元硼化物を形成するために必要不可欠な元素であり、サーメット層中に、３～７．５質量％含有させる。Ｂ含有量が３質量％未満になると、三元硼化物の形成量が少なく、組織中の硬質の割合が少なくなるため、得られたサーメット層の十分な硬度と耐摩耗性を付与することができない。
　一方、７．５質量％を超えると、硬度は高くなるがサーメット層の強度（靭性や耐熱衝撃性）の低下をもたらす。よって、本サーメット層中のＢ含有量は、３～７．５質量％とする。
　形成されるサーメット層には三元硼化物が含まれるため中性子遮蔽能力に優れている。 B is an indispensable element for forming the ternary boride in the cermet layer, and is contained in an amount of 3 to 7.5% by mass in the cermet layer. When the B content is less than 3% by mass, the amount of ternary boride formed is small and the ratio of hardness in the structure is small, so that sufficient hardness and wear resistance of the obtained cermet layer can be imparted. Can not.
On the other hand, if it exceeds 7.5% by mass, the hardness increases but the strength (toughness and thermal shock resistance) of the cermet layer is lowered. Therefore, the B content in the cermet layer is 3 to 7.5% by mass.
Since the formed cermet layer contains ternary boride, it has excellent neutron shielding ability.
　上記Ｂ以外の元素として、ＭＭ’Ｂ又はＭ２Ｍ’Ｂ２（Ｍ，Ｍ’＝遷移金属）型三元硼化物としてのＭとしては、Ｍｏ、Ｗ、Ｔａ、Ｍ’としては、Ｆｅ、Ｎｉ、Ｃｒ、Ｃｏを選択的に添加する。 As elements other than B, M as MM′B or M 2 M′B 2 (M, M ′ = transition metal) type ternary boride is Mo, W, Ta, M ′ is Fe, Ni, Cr and Co are selectively added.
　三元硼化物と金属結合相の好ましい組合せは、Ｍｏ２ＦｅＢ２型硼化物とＦｅ基合金との組合せ、Ｗ２ＦｅＢ２型硼化物とＦｅ基合金との組合せ、Ｍｏ２ＮｉＢ２型硼化物とＮｉ基合金との組合せ、Ｗ２ＮｉＢ２型硼化物とＮｉ基合金との組合せ、ＷＣｏＢ型硼化物とＣｏ基合金との組合せである。
　Ｍｏ２ＦｅＢ２型硼化物とＦｅ基合金とを組合せたサーメット材は、耐摩耗性に優れ、比較的安価であり、Ｗ２ＦｅＢ２型硼化物とＦｅ基合金とを組合せたサーメット材は更に耐摩耗性が向上する。Ｍｏ２ＮｉＢ２型硼化物とＮｉ基合金とを組合せたサーメット材は、耐摩耗性、耐食性、耐熱性に優れ、Ｗ２ＮｉＢ２型硼化物とＮｉ基合金とを組合せたサーメット材は、さらに耐摩耗性が向上する。ＷＣｏＢ型硼化物とＣｏ基合金とを組合せたサーメット材は、耐熱性に優れる。 Preferred combinations of the ternary boride and the metal bonded phase are a combination of a Mo 2 FeB 2 type boride and an Fe-based alloy, a combination of a W 2 FeB 2 type boride and an Fe-based alloy, and a Mo 2 NiB 2 type boride. And a combination of a W 2 NiB 2 type boride and a Ni base alloy, and a combination of a WCoB type boride and a Co base alloy.
The cermet material combining Mo 2 FeB 2 type boride and Fe-based alloy is excellent in wear resistance and relatively inexpensive, and the cermet material combining W 2 FeB 2 type boride and Fe-based alloy is further Abrasion resistance is improved. The cermet material combining the Mo 2 NiB 2 type boride and the Ni base alloy is excellent in wear resistance, corrosion resistance, and heat resistance, and the cermet material combining the W 2 NiB 2 type boride and the Ni base alloy is further Abrasion resistance is improved. A cermet material combining a WCoB type boride and a Co-based alloy is excellent in heat resistance.
　前記Ｍｏ２ＦｅＢ２型硼化物またはＭｏ２ＮｉＢ２型硼化物中において、ＷまたはＴａはＭｏと任意の割合で置換することができる In the Mo 2 FeB 2 type boride or Mo 2 NiB 2 type boride, W or Ta can be substituted with Mo in an arbitrary ratio.
　前記Ｗ２ＮｉＢ２型硼化物、Ｗ２ＦｅＢ２型硼化物、ＷＣｏＢ型硼化物中において、ＭｏおよびＴａはＷと任意の割合で置換することができる。 In the W 2 NiB 2 type boride, W 2 FeB 2 type boride, and WCoB type boride, Mo and Ta can be substituted with W at an arbitrary ratio.
　Ｆｅ、Ｎｉ、Ｃｒ、Ｃｏは、サーメット中のＦｅ、Ｎｉ、Ｃｏと任意の割合で置換することができ、耐食性、耐熱性といった特性を制御することができる。 Fe, Ni, Cr, and Co can be replaced with Fe, Ni, and Co in the cermet at an arbitrary ratio, and characteristics such as corrosion resistance and heat resistance can be controlled.
　なお、実施形態１の溶射用の粉末を製造する過程で含まれる不可避的不純物（Ｓｉ、Ａｌ、Ｍｇ、Ｐ、Ｓ、Ｎ、Ｏ、Ｃ等）や他の元素（希土類等）が、サーメット層の特性を損なわない程度に極く少量含まれても差し支えないことは勿論である。 In addition, inevitable impurities (Si, Al, Mg, P, S, N, O, C, etc.) and other elements (rare earth, etc.) included in the process of manufacturing the thermal spraying powder of Embodiment 1 are added to the cermet layer. Of course, it may be contained in such a small amount that it does not impair the characteristics of the above.
　サーメット層中に含まれる三元硼化物の量は、サーメット層全体の１２～９５質量％の範囲であることが好ましい。三元硼化物の量が１２質量％未満になると、十分な中性子遮蔽能が得られない。一方、三元硼化物の量が９５質量％を超えると塑性変形能の高い金属相が少なくなり、セラミックス量が多くなることにより、高速フレーム溶射ではポア等の欠陥を生じ、緻密な溶射皮膜が得られず、金属母材との優れた密着力が得られない。
　よって、本サーメット層中の複硼化物の割合は、１２～９５質量％とすることが望ましい。 The amount of ternary boride contained in the cermet layer is preferably in the range of 12 to 95% by mass based on the entire cermet layer. When the amount of the ternary boride is less than 12% by mass, sufficient neutron shielding ability cannot be obtained. On the other hand, if the amount of ternary boride exceeds 95% by mass, the metal phase with high plastic deformability decreases, and the amount of ceramics increases, resulting in defects such as pores in high-speed flame spraying, resulting in a dense sprayed coating. It cannot be obtained, and excellent adhesion with the metal base material cannot be obtained.
Therefore, the ratio of the double boride in the cermet layer is desirably 12 to 95% by mass.
　また、三元硼化物サーメットに、さらに二元硼化物を添加することも可能である。
二元硼化物としては、例えば、Ｂ４Ｃ、ＡｌＢ１２、ＺｒＢ１２、ＹＢ１２、ＦｅＢ、ＮｉＢ等が挙げられる。二元硼化物を添加する場合、サーメット層中のＭ’金属相の割合が５質量％以上存在することが好ましい。
　金属相の割合が５質量％未満であると、サーメット層において塑性変形能の高い金属相が少なくなり、セラミックス量が多くなることにより、高速フレーム溶射ではポア等の欠陥を生じ、緻密な皮膜が得られず、優れた密着力が得られないという欠陥が出やすくなるからである。
　これらの二元硼化物の組成を表１に示す。 It is also possible to add a binary boride to the ternary boride cermet.
Examples of the binary boride include B 4 C, AlB 12 , ZrB 12 , YB 12 , FeB, and NiB. When adding a binary boride, it is preferable that the ratio of the M ′ metal phase in the cermet layer is 5% by mass or more.
When the proportion of the metal phase is less than 5% by mass, the metal phase having high plastic deformability decreases in the cermet layer, and the amount of ceramics increases, resulting in defects such as pores in high-speed flame spraying, resulting in a dense film. This is because defects that cannot be obtained and excellent adhesion cannot be easily obtained.
The compositions of these binary borides are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
＜サーメット層の厚み＞
　実施の形態１の熱中性子遮蔽材料におけるサーメット層の厚みとしては、０．０５～５ｍｍとすることが好適である。
　サーメット層を溶射により形成する場合、溶射層は，すでに形成されている溶射皮膜上に新たな粉末粒子が高速で衝突することによって、緻密な皮膜が形成される。このため、溶射層の厚みが０．０５ｍｍ未満の場合は、溶射皮膜の厚さが薄く、緻密な溶射層が得られず、一方、溶射層の厚みが５ｍｍを超える場合は、溶射皮膜の厚さが厚くなり、溶射皮膜中の残留応力が高くなり溶射皮膜に割れを発生しやすくなり、良好な耐食性や高い熱中性子遮蔽能を備えた熱中性子遮蔽材料が得られない。
　よって、熱中性子遮蔽材料におけるサーメット層の厚みとしては、０．０５～５ｍｍとすることが望ましい。 <Thickness of cermet layer>
The thickness of the cermet layer in the thermal neutron shielding material of Embodiment 1 is preferably 0.05 to 5 mm.
When the cermet layer is formed by thermal spraying, a dense coating is formed in the thermal spraying layer by collision of new powder particles on the sprayed coating that has already been formed. For this reason, when the thickness of the thermal spray layer is less than 0.05 mm, the thickness of the thermal spray coating is thin and a dense thermal spray layer cannot be obtained. On the other hand, when the thickness of the thermal spray layer exceeds 5 mm, the thickness of the thermal spray coating is Therefore, the residual stress in the thermal spray coating is increased and cracks are likely to occur in the thermal spray coating, and a thermal neutron shielding material having good corrosion resistance and high thermal neutron shielding capability cannot be obtained.
Therefore, the thickness of the cermet layer in the thermal neutron shielding material is preferably 0.05 to 5 mm.
＜金属母材上へのサーメット層の形成＞
　実施の形態１の熱中性子遮蔽材料は、サーメット層の配合になるように溶射用粉末を調整し、普通鋼、合金鋼、工具鋼、ステンレス鋼、又はアルミニウム合金などの金属母材上に溶射ガンを使用して，所定の厚みになるように噴射して形成する。
　溶射ガンの溶射粉末投入容器に、ＭＭ’Ｂ又はＭ２Ｍ’Ｂ２（Ｍ，Ｍ’＝遷移金属）型三元硼化物粉末、二元硼化物粉末、Ｍ’金属粉末を混合調整して投入し、高速フレーム溶射法を適用して、大気中で溶射施工することが好ましい。
　高速フレーム溶射法は、溶射技術の中でも比較的低温で溶射層を形成するため、サーメット材料や複硼化物サーメットに好適に採用でき、溶射皮膜中の引張の残留応力を低減でき、金属母材との高い密着力を得ることができる。 <Formation of cermet layer on metal matrix>
In the thermal neutron shielding material of the first embodiment, the thermal spray powder is adjusted so that the cermet layer is blended, and a thermal spray gun is formed on a metal base material such as ordinary steel, alloy steel, tool steel, stainless steel, or aluminum alloy. And is formed by spraying to a predetermined thickness.
Mix and adjust MM'B or M 2 M'B 2 (M, M '= transition metal) type ternary boride powder, binary boride powder, and M' metal powder in the spraying powder charging container of the spray gun. It is preferable that the thermal spraying is performed in the atmosphere by applying the high-speed flame spraying method.
The high-speed flame spraying method forms a thermal spray layer at a relatively low temperature among the thermal spraying techniques, so it can be suitably used for cermet materials and double boride cermets, can reduce tensile residual stress in the thermal spray coating, High adhesion can be obtained.
　また、実施の形態１のサーメット層は、塑性変形能の高い金属相を含むため、ポア等の欠陥が極めて少なく、緻密な皮膜が得られ、優れた密着力を有している。加えて、高速フレーム溶射を用いた場合、材料の組成変動を抑制することができ、優れた耐食性を発揮できる。 In addition, since the cermet layer of Embodiment 1 includes a metal phase having a high plastic deformability, it has very few defects such as pores, a dense film is obtained, and has excellent adhesion. In addition, when high-speed flame spraying is used, the composition fluctuation of the material can be suppressed and excellent corrosion resistance can be exhibited.
＜溶射粉末の粒度＞
　溶射粉末の粒度としては、通常、プラズマ溶射法では１５～１００μｍのものを用いることができるが、上記高速フレーム溶射を用いた場合では、２０～６０μｍ程度のものを用いることが好ましい。
　溶射粉末の粒度が粗いと、緻密なサーメット層を形成することが困難となりサーメット層にポア等の欠陥ができやすく硬度が低下する。一方、溶射粉末の粒度が微細になると、溶射粉末の流動性が低下し溶射作業性を損なう。 <Particle size of sprayed powder>
As the particle size of the sprayed powder, a particle size of 15 to 100 μm can be usually used in the plasma spraying method, but when the high-speed flame spraying is used, a particle size of about 20 to 60 μm is preferable.
When the particle size of the sprayed powder is coarse, it is difficult to form a dense cermet layer, and defects such as pores are easily formed in the cermet layer, and the hardness is lowered. On the other hand, when the particle size of the thermal spray powder becomes fine, the fluidity of the thermal spray powder decreases and the thermal spray workability is impaired.
＜実施例１～１４＞
　以下に、実施例を示し、実施の形態１についてさらに詳細に説明する。
表２に、実施例１～１４において形成するサーメット層の、Ｍ２Ｍ’Ｂ２型三元硼化物、Ｍ’金属相、硼化物量、金属相量、サーメット層中の組成（ｗｔ％）を示す。
　実施例１～１４のそれぞれにおいて、表２に示すサーメット層組成となるように、溶射粉のＭ２Ｍ’Ｂ２型三元硼化物及びＭ’金属相の割合を調整して、金属母材上にサーメット層を形成する。また、硬質相を１００％とし金属相を０％としたものを比較例１とした。
なお、実施例１～１４の溶射の金属母材には工具鋼(ＳＫＤ)の試験片を用いる。 <Examples 1 to 14>
Examples will be described below, and the first embodiment will be described in more detail.
Table 2 shows the M2M′B2 type ternary boride, M ′ metal phase, boride content, metal phase content, and composition (wt%) in the cermet layer of the cermet layers formed in Examples 1 to 14.
In each of Examples 1 to 14, the ratio of M2M′B2 type ternary boride and M ′ metal phase of the thermal spray powder was adjusted so that the cermet layer composition shown in Table 2 was obtained, and the cermet was formed on the metal base material. Form a layer. In addition, Comparative Example 1 was obtained by setting the hard phase to 100% and the metal phase to 0%.
Note that a tool steel (SKD) test piece is used as the metal base material for thermal spraying in Examples 1 to 14.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　溶射粉は、まず、表２の実施例１～１４の組成のサーメット層組成になるように原料粉末を配合し、ボールミルでの湿式粉砕する。次に、湿式粉砕した粉末をスプレードライヤーによって造粒し、１１５０℃で１時間保持し、硬質相となるＭ２Ｍ’Ｂ２型三元硼化物とＭ’金属相を反応形成させる。
　その後、この形成されたＭ２Ｍ’Ｂ２型三元硼化物及びＭ’金属相を分級して、サーメット層形成用の２０～６０μｍの大きさの溶射粉末を完成させる。
　一方、サーメット層を形成させる金属母材の表層にはショット（ホワイトアルミナ♯２０）を使用し、金属母材の表面を粗面化する。 First, the spray powder is blended with the raw material powder so as to have the composition of the cermet layers of the compositions of Examples 1 to 14 shown in Table 2, and wet pulverized with a ball mill. Next, the wet pulverized powder is granulated with a spray dryer and held at 1150 ° C. for 1 hour to cause M 2 M′B 2 type ternary boride, which becomes a hard phase, and M ′ metal phase to react.
Thereafter, the formed M 2 M′B 2 type ternary boride and M ′ metal phase are classified to complete a sprayed powder having a size of 20 to 60 μm for forming a cermet layer.
On the other hand, shot (white alumina # 20) is used for the surface layer of the metal base material on which the cermet layer is formed, and the surface of the metal base material is roughened.
　その後、用意した原料粉末を溶射してＳＫＤ鋼母材上に、厚み０．３ｍｍの、実施例１～１４の組成のサーメット層を形成する。用いた溶射機は、高速フレーム溶射機(PRAXAIR/TAFA製JP-5000)で、以下の条件でサーメット層を形成する。
　溶射距離（基材と溶射ガンとの距離）：３８０ｍｍ
　酸素流量：１９００ｓｃｆｈ
　灯油流量：５ｇｐｈ Thereafter, the prepared raw material powder is sprayed to form a cermet layer having a composition of Examples 1 to 14 having a thickness of 0.3 mm on the SKD steel base material. The sprayer used was a high-speed flame sprayer (JP-5000 manufactured by PRAXAIR / TAFA), which forms a cermet layer under the following conditions.
Thermal spray distance (distance between substrate and thermal spray gun): 380 mm
Oxygen flow rate: 1900 scfh
Kerosene flow rate: 5gph
＜実施例１５＞
　表３に、実施例１５において形成するサーメット層の、ＭＭ’Ｂ型三元硼化物、Ｍ’金属相、硼化物量、金属相量、サーメット層中の組成（ｗｔ％）を示す。実施例１５においては、実施例１～１４と、ＭＭ’Ｂ型三元硼化物、Ｍ’金属相、硼化物量、金属相量、サーメット層中の組成（ｗｔ％）が異なるが、溶射粉の製造、金属母材、溶射条件等、その他の条件においては同様である。
Figure JPOXMLDOC01-appb-T000003
 <Example 15>
Table 3 shows the MM′B type ternary boride, M ′ metal phase, boride content, metal phase content, and composition (wt%) in the cermet layer of the cermet layer formed in Example 15. In Example 15, although different from Examples 1 to 14 in MM′B type ternary boride, M ′ metal phase, boride amount, metal phase amount, and composition (wt%) in the cermet layer, The same applies to other conditions such as the manufacture of metal, metal base material, and thermal spraying conditions.
Figure JPOXMLDOC01-appb-T000003
＜実施の形態１の評価＞
＜金属母材との密着性評価＞
　表２に記載した実施の形態１の実施例２及び比較例１について、金属母材の表面に形成したサーメット層の密着性を評価した。密着性評価はねじり試験機を用いて行った。試験方法は、ねじり試験機に取り付けられるような試験片を作成し、試験片の一端を固定し、他端を回転させて行った（図１参照）。回転により、サーメット層に剥離又はクラックを生じた時のトルク値をサーメット層の密着力とした。
　実施例２の密着力は大きく高い値を示したが、比較例１は低いトルク値を示した。その結果を表４に示す。 <Evaluation of Embodiment 1>
<Evaluation of adhesion to metal matrix>
For Example 2 and Comparative Example 1 of Embodiment 1 shown in Table 2, the adhesion of the cermet layer formed on the surface of the metal base material was evaluated. The adhesion evaluation was performed using a torsion tester. The test method was performed by preparing a test piece that can be attached to a torsion tester, fixing one end of the test piece, and rotating the other end (see FIG. 1). The torque value when peeling or cracking occurred in the cermet layer by rotation was defined as the adhesion of the cermet layer.
The adhesion strength of Example 2 showed a large and high value, but Comparative Example 1 showed a low torque value. The results are shown in Table 4.
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
［実施の形態２］
　次に、本発明の実施の形態２について説明する。
実施の形態２の熱中性子遮蔽材料は、金属母材上にサーメット層を形成させたものである点で実施の形態１と同様であるが、サーメット層は、複硼化物よりなる硬質相と、残部が硬質相を結合する結合相と、からなる。すなわち、Ｍ２Ｍ’Ｂ２型複硼化物とＭ’基合金の結合相とよりなる複硼化物サーメットである。ここで、Ｍ＝Ｍｏ，Ｍ’＝ＮｉまたはＦｅである。 [Embodiment 2]
Next, a second embodiment of the present invention will be described.
The thermal neutron shielding material of the second embodiment is the same as that of the first embodiment in that a cermet layer is formed on a metal base material, but the cermet layer includes a hard phase composed of a double boride, The balance consists of a binder phase that binds the hard phase. That is, a double boride cermet comprising a M2M′B2 type double boride and a bonded phase of an M′-based alloy. Here, M = Mo, M ′ = Ni or Fe.
　また、サーメット層は、複硼化物よりなる硬質相３５～９５質量％と、残部が該硬質相を結合するＮｉ基合金又はＦｅ基合金の結合相とからなり、
Ｂ含有量が、３～７．５質量％、
Ｍｏ含有量が、Ｍｏ／Ｂ原子比で０．８～（１．６－０．０５Ｘ）、
Ｃｒ含有量が（５５－５Ｘ）質量％以下、
残部が１０質量％以上のＮｉ、および不可避的不純物よりなる。 The cermet layer is composed of 35 to 95% by mass of a hard phase made of a double boride, and the balance is a Ni-base alloy or Fe-base alloy binder phase that binds the hard phase.
B content is 3 to 7.5% by mass,
Mo content is 0.8 to (1.6-0.05X) in terms of Mo / B atomic ratio,
Cr content is (55-5X) mass% or less,
The balance is 10% by mass or more of Ni and unavoidable impurities.
　なお、上記結合相は、Ｎｉ基合金に代えてＦｅ基合金に変更することも可能であり、この場合、サーメット層は、複硼化物よりなる硬質相３５～９５質量％と、残部が該硬質相を結合するＦｅ基の結合相とからなり、
Ｂ含有量が、３～７．５質量％、
Ｍｏ含有量が、Ｍｏ／Ｂ原子比で０．８～（１．６－０．０５Ｘ）、
Ｃｒおよび／又はＮｉ含有量が、いずれか一方または両者の合計で（５５－５Ｘ）質量％以下、
Ｃ含有量が、０．０５～０．９５％質量以下、
残部が１０質量％以上のＦｅ、および不可避的不純物よりなる。 The binder phase can be changed to an Fe-based alloy instead of the Ni-based alloy. In this case, the cermet layer has a hard phase of 35 to 95% by mass made of double boride, and the balance is the hard alloy. And a Fe-phase binder phase that binds the phases,
B content is 3 to 7.5% by mass,
Mo content is 0.8 to (1.6-0.05X) in terms of Mo / B atomic ratio,
Cr and / or Ni content is not more than (55-5X) mass% in any one or both,
C content is 0.05 to 0.95% by mass or less,
The balance consists of 10 mass% or more of Fe and inevitable impurities.
　Ｂは、サーメット層中の複硼化物を形成するために必要不可欠な元素であり、サーメット層中に、３～７．５質量％含有させる。Ｂ含有量が３質量％未満になると、複硼化物の形成量が少なく、組織中の硬質相の割合が少なくなるため、得られたサーメット層の十分な硬度と耐摩耗性を付与することができない。一方、７．５質量％を超えると、硬度は高くなるがサーメット層の強度（靭性や耐熱衝撃性）の低下をもたらす。よって、本サーメット層中のＢ含有量は、３～７．５質量％とする。形成されるサーメット層には複硼化物が含まれるため中性子遮蔽能力に優れている。 B is an indispensable element for forming a double boride in the cermet layer, and is contained in an amount of 3 to 7.5% by mass in the cermet layer. When the B content is less than 3% by mass, the formation of double borides is small and the ratio of the hard phase in the structure is small, so that sufficient hardness and wear resistance of the obtained cermet layer can be imparted. Can not. On the other hand, if it exceeds 7.5% by mass, the hardness increases but the strength (toughness and thermal shock resistance) of the cermet layer is lowered. Therefore, the B content in the cermet layer is 3 to 7.5% by mass. Since the formed cermet layer contains double borides, the neutron shielding ability is excellent.
　ＭｏはＢ同様硬質相となる硼化物を形成するために必要不可欠な元素である。また、Ｍｏの一部は結合相に固溶して、合金の機械的特性および耐摩耗性を向上させる他に、還元性雰囲気に対する耐食性を向上させる。
　Ｍｏ２ＮｉＢ２型またはＭｏ２ＦｅＢ２型複硼化物は、ＭｏとＢの化学量論比は１：１であるが、実際は完全な化学量論的な化合物ではなく、数％の組成範囲を有するため、Ｍｏ／Ｂの原子比（以下Ｍｏ／Ｂ比と略す）は１である必要はないが、１の前後のある特定の範囲にすることが重要である。 Mo is an indispensable element for forming a boride that becomes a hard phase like B. In addition, a part of Mo is dissolved in the binder phase to improve the mechanical properties and wear resistance of the alloy, and to improve the corrosion resistance to a reducing atmosphere.
Mo 2 NiB 2 type or Mo 2 FeB 2 type double boride has a stoichiometric ratio of Mo to B of 1: 1, but is not actually a complete stoichiometric compound and has a composition range of several percent. Therefore, the atomic ratio of Mo / B (hereinafter abbreviated as Mo / B ratio) does not have to be 1, but it is important that the Mo / B atomic ratio is within a certain range around 1.
　Ｍｏ２ＮｉＢ２型複硼化物サーメットの場合、Ｍｏ／Ｂ比が０．８より小さい場合には、Ｍｏ２ＮｉＢ２型複硼化物とは異なる、Ｃｒ5 Ｂ3などのＭ'5Ｂ3型（Ｍ'：Ｃｒを主体とし、Ｍｏ、Ｎｉ等を含む）硼化物やＮｉ3ＢなどのＭ''3Ｂ型（Ｍ''：Ｎｉを主体とし、Ｃｒ、Ｍｏ等を含む）などの他の硼化物が第３相として形成され、サーメット層の強度の低下が著しい。Ｍｏ／Ｂ比が（１．６－０．０５Ｘ）より大きい場合には、Ｍｏ－Ｎｉ系の金属間化合物を第３相として形成し、サーメット層の強度の低下を招く。 In the case of Mo 2 NiB 2 type double boride cermet, when the Mo / B ratio is less than 0.8, M ′ 5 B 3 type such as Cr 5 B 3 is different from Mo 2 NiB 2 type double boride. Others such as M ″ 3 B type (M ′: mainly composed of Ni, including Cr, Mo, etc.) such as boride and Ni 3 B (M ′: mainly composed of Cr, including Mo, Ni, etc.) Boride is formed as the third phase, and the strength of the cermet layer is significantly reduced. When the Mo / B ratio is larger than (1.6-0.05X), a Mo—Ni-based intermetallic compound is formed as the third phase, and the strength of the cermet layer is reduced.
　Ｍｏ２ＦｅＢ２型複硼化物サーメットの場合、Ｍｏ／Ｂ比が０．８より小さい場合には、Ｍｏ２ＦｅＢ２型複硼化物とは異なる、Ｆｅ２Ｂ等のＦｅ硼化物が形成するため、耐摩耗性および耐食性が低下することに加え、サーメット層の強度が低下する。Ｍｏ／Ｂ比が（１．６－０．０５Ｘ）を超える場合、Ｍ６ＣやＭ２３Ｃ６（Ｍは金属を表す）などの炭化物およびＦｅ－Ｍｏ間の金属間化合物の形成量が増加するために強度の低下を招く。 In the case of Mo 2 FeB 2 type double boride cermet, when the Mo / B ratio is smaller than 0.8, Fe boride such as Fe 2 B, which is different from Mo 2 FeB 2 type double boride, is formed. In addition to a decrease in wear resistance and corrosion resistance, the strength of the cermet layer is decreased. When the Mo / B ratio exceeds (1.6-0.05X), the amount of carbides such as M 6 C and M 23 C 6 (M represents a metal) and the formation of intermetallic compounds between Fe-Mo increase. This causes a decrease in strength.
　Ｍｏ２ＮｉＢ２型複硼化物サーメットの場合、Ｎｉは、ＢおよびＭｏ同様に、本サーメット層中の複硼化物の形成に必要不可欠な元素であり、結合相を構成する主な元素であり、サーメット層中に１０質量％以上含有させることが望ましい。Ｎｉ含有量が１０質量％未満の場合は、溶射時に十分な液相が出現せず緻密な溶射層が得られず、強度の低下が著しい。これは結合相中のＮｉが少ないと複硼化物との結合力が弱まることに加え、結合相の強度が低下し、ひいてはサーメット層の強度低下を招くためである。 In the case of the Mo 2 NiB 2 type double boride cermet, Ni is an essential element for forming the double boride in the cermet layer and is the main element constituting the binder phase, like B and Mo. It is desirable to contain 10% by mass or more in the cermet layer. When the Ni content is less than 10% by mass, a sufficient liquid phase does not appear at the time of spraying, a dense sprayed layer cannot be obtained, and the strength is significantly reduced. This is because if the Ni content in the binder phase is small, the bond strength with the double boride is weakened, the strength of the binder phase is lowered, and consequently the strength of the cermet layer is lowered.
　Ｍｏ２ＮｉＢ２型複硼化物サーメットの場合、ＣｒをＮｉと置換するように添加してもよい。Ｃｒは、サーメット層中の複硼化物中のＮｉと置換固溶し、複硼化物を構成する元素である。また、添加したＣｒは、結合相中にも固溶し、サーメット層の耐食性、耐摩耗性、高温特性、および機械的特性を大幅に向上させる効果がある。サーメット層中のＣｒ含有量が、（５５－５Ｘ）質量％を超えると、Ｃｒ５Ｂ３などの硼化物を形成し、強度が低下する。 In the case of Mo 2 NiB 2 type double boride cermet, Cr may be added to replace Ni. Cr is an element constituting a double boride by substitutional solid solution with Ni in the double boride in the cermet layer. The added Cr also dissolves in the binder phase, and has the effect of greatly improving the corrosion resistance, wear resistance, high temperature characteristics, and mechanical characteristics of the cermet layer. When the Cr content in the cermet layer exceeds (55-5X) mass%, borides such as Cr 5 B 3 are formed and the strength is lowered.
　Ｍｏ２ＦｅＢ２型複硼化物サーメットの場合、Ｆｅは、ＢおよびＭｏ同様に、本サーメット層中の複硼化物の形成に必要不可欠な元素であり、結合相を構成する主な元素であり、サーメット層中に１０質量％以上含有させることが望ましい。Ｆｅ含有量が１０質量％未満の場合は、溶射時に十分な液相が出現せず緻密な溶射層が得られず、強度の低下が著しい。これは結合相中のＦｅが少ないと複硼化物との結合力が弱まることに加え、結合相の強度が低下し、ひいてはサーメット層の強度低下を招くためである。 In the case of the Mo 2 FeB 2 type double boride cermet, Fe is an essential element for forming the double boride in the cermet layer and is the main element constituting the binder phase, like B and Mo. It is desirable to contain 10% by mass or more in the cermet layer. When the Fe content is less than 10% by mass, a sufficient liquid phase does not appear at the time of spraying, a dense sprayed layer cannot be obtained, and the strength is significantly reduced. This is because if the amount of Fe in the binder phase is small, the bond strength with the double boride is weakened, the strength of the binder phase is lowered, and consequently the strength of the cermet layer is lowered.
　Ｍｏ２ＦｅＢ２型複硼化物サーメットの場合、Ｎｉ又は／及びＣｒをＦｅと置換するように添加してもよい。Ｎｉ又は／およびＣｒは、サーメット層の耐食性および耐酸化性を向上させる効果を示す。また、ＮｉとＣｒを組み合わせて使用（複合含有）することで、結合相をマルテンサイト、フェライト、オーステナイトおよびこれらの混相組織に任意に制御することにより、機械的特性および耐摩耗性を低減することなく、用途に応じた耐食性、耐熱性の付与が可能である。Ｎｉ又は／およびＣｒの含有量は、単体含有あるいは複合含有した場合のいずれも含有量が３５質量％を超えて添加すると、耐食性および耐熱性は非常に優れるものの、強度の低下を生じる。よって、Ｎｉ又は／およびＣｒの含有量は、単体含有あるいは複合含有した場合の合計量で、（５５－５Ｘ）質量％にすることが望ましい。 In the case of Mo 2 FeB 2 type double boride cermet, Ni or / and Cr may be added to replace Fe. Ni or / and Cr show the effect of improving the corrosion resistance and oxidation resistance of the cermet layer. Also, by using Ni and Cr in combination (comprising inclusion), the mechanical properties and wear resistance can be reduced by arbitrarily controlling the binder phase to martensite, ferrite, austenite and their mixed phase structure. In addition, it is possible to impart corrosion resistance and heat resistance according to the application. When the content of Ni or / and Cr is added exceeding 35% by mass in the case of containing alone or in combination, the corrosion resistance and heat resistance are very excellent, but the strength is lowered. Therefore, the content of Ni or / and Cr is preferably (55-5X) mass% in terms of the total amount when contained alone or in combination.
　なお、実施形態２の溶射用の粉末を製造する過程で含まれる不可避的不純物や他の元素が、サーメット層の特性を損なわない程度にごく少量含まれても差し支えないことは実施形態１と同様である。
　Ｃについては、Ｍｏ２ＦｅＢ２型複硼化物サーメットの場合、粉末表面の酸化物を還元する役割を有している。また一部は結合相中に固溶して硬度の向上をもたらす。含有量が０．０５質量％未満では効果が少なく、１質量％を超えると炭化物の形成を促進し、サーメット層の強度が低下する傾向を示す。また、耐食性の低下にも繋がる。したがって、Ｃの含有量は、０．０５～１質量％にすることが望ましい。 As in the case of the first embodiment, the inevitable impurities and other elements contained in the process for producing the thermal spraying powder of the second embodiment may be contained in a very small amount so as not to impair the properties of the cermet layer. It is.
For C, if the Mo 2 FeB 2 type complex boride cermet has a role of reducing the oxide of the powder surface. Some of them are dissolved in the binder phase to improve the hardness. If the content is less than 0.05% by mass, the effect is small, and if it exceeds 1% by mass, the formation of carbides is promoted and the strength of the cermet layer tends to decrease. Moreover, it leads also to a fall of corrosion resistance. Therefore, the C content is desirably 0.05 to 1% by mass.
　サーメット層中に含まれる複硼化物の量は、溶射層全体の３５～９５質量％の範囲であることが好ましい。複硼化物の量が３５質量％未満になると、十分な中性子遮蔽能が得られない。一方、複硼化物の量が９５質量％を超えると塑性変形能の高い結合相が少なくなり、セラミックス量が多くなることにより、溶射ではポア等の欠陥を生じ、緻密な溶射皮膜が得られず、金属母材との優れた密着力が得られない。よって、本サーメット層中の複硼化物の割合は、３５～９５質量％とすることが望ましい。 The amount of double boride contained in the cermet layer is preferably in the range of 35 to 95% by mass of the entire sprayed layer. When the amount of the double boride is less than 35% by mass, sufficient neutron shielding ability cannot be obtained. On the other hand, when the amount of the double boride exceeds 95% by mass, the binder phase having high plastic deformability decreases, and the amount of ceramics increases, so that defects such as pores are generated by thermal spraying, and a dense thermal spray coating cannot be obtained. An excellent adhesion with a metal base material cannot be obtained. Therefore, the ratio of the double boride in the cermet layer is desirably 35 to 95% by mass.
＜サーメット層の厚み＞
実施形態２の熱中性子遮蔽材料における溶射層の厚みは、実施形態１の場合と同様である。 <Thickness of cermet layer>
The thickness of the thermal spray layer in the thermal neutron shielding material of the second embodiment is the same as that of the first embodiment.
＜金属母材上へのサーメット層の形成＞
　実施の形態２の熱中性子遮蔽材料は、サーメット層の配合になるように溶射用粉末を調整し、金属母材上に溶射ガンを使用して，所定の厚みになるように噴射して形成する。
溶射ガンの溶射粉末投入容器に、Ｍ２Ｍ’Ｂ２（Ｍ，Ｍ’＝遷移金属）型複硼化物粉末、金属粉末を混合調整して投入し、高速フレーム溶射法を適用して、大気中で溶射施工することが好ましい。 <Formation of cermet layer on metal matrix>
The thermal neutron shielding material according to the second embodiment is formed by adjusting the thermal spraying powder so that the cermet layer is blended, and using a thermal spray gun on the metal base material and spraying it to a predetermined thickness. .
M 2 M′B 2 (M, M ′ = transition metal) type double boride powder and metal powder are mixed and introduced into a spray powder container of a spray gun, and a high-speed flame spraying method is applied to the atmosphere. Thermal spraying is preferable.
＜溶射粉末の粒度＞
　実施の形態２における溶射粉末の粒度は、実施の形態１と同様である。 <Particle size of sprayed powder>
The particle size of the thermal spray powder in the second embodiment is the same as that in the first embodiment.
＜実施例１６＞
　以下に、実施例１６を示し、実施の形態２についてさらに詳細に説明する。
表５に、実施例１６において、形成したサーメット層の組成、形成したサーメット層の硼化物と結合層の割合を示す。実施例１６において、表５に示すサーメット層組成となるように、溶射用原料粉末の複硼化物及び結合相となる金属粉の割合を調整して、金属母材上にサーメット層を形成した。なお、溶射の金属母材にはステンレス鋼(SUS316L)の試験片を用いた。 <Example 16>
Example 16 will be shown below, and the second embodiment will be described in more detail.
Table 5 shows the composition of the cermet layer formed in Example 16 and the ratio between the boride and the bonding layer of the formed cermet layer. In Example 16, the cermet layer was formed on the metal base material by adjusting the ratio of the double boride of the thermal spraying raw material powder and the metal powder as the binder phase so as to have the cermet layer composition shown in Table 5. A stainless steel (SUS316L) test piece was used as the metal base material for thermal spraying.
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000005
　溶射粉は、まず、表５の実施例１６組成の溶射層組成になるように原料粉末を配合し、ボールミルでの湿式粉砕した。次に、湿式粉砕した粉末をスプレードライヤーによって造粒し、１１５０℃で１時間保持し、硬質相となるＭ２Ｍ’Ｂ２型の複硼化物を反応形成させた。その後、この形成されたＭ２Ｍ’Ｂ２型複硼化物サーメットを分級して、サーメット層形成用の２０～６０μｍの大きさの溶射粉末を完成させた。
　一方、サーメット層を形成させる金属母材の表層にはショット（ホワイトアルミナ♯２０）を使用し、金属母材の表面を粗面化した。 The thermal spray powder was first blended with the raw material powder so as to have the thermal spray layer composition of Example 16 in Table 5, and wet pulverized with a ball mill. Next, the wet pulverized powder was granulated with a spray dryer and held at 1150 ° C. for 1 hour to form an M 2 M′B 2 type double boride which becomes a hard phase by reaction. Thereafter, the formed M 2 M′B 2 type double boride cermet was classified to complete a sprayed powder having a size of 20 to 60 μm for forming a cermet layer.
On the other hand, shot (white alumina # 20) was used for the surface layer of the metal base material for forming the cermet layer, and the surface of the metal base material was roughened.
　その後、用意した原料粉末を溶射して、母材上に厚み０．３ｍｍの、実施例１６の組成のサーメット層を形成した。用いた溶射機や溶射条件等は、前記実施形態１と同様である。 Thereafter, the prepared raw material powder was sprayed to form a cermet layer having a composition of Example 16 having a thickness of 0.3 mm on the base material. The thermal spraying machine and thermal spraying conditions used are the same as those in the first embodiment.
＜比較例２＞
　また、比較のため、結合相を形成しない（サーメットとならない）複硼化物のみを溶射用粉末として用いて形成した溶射層を比較例２（表５参照）として示す。比較例２においては、実施例１６と、溶射用原料粉末が異なるが、溶射条件等、その他の条件においては同様である。 <Comparative Example 2>
For comparison, a sprayed layer formed using only a double boride that does not form a binder phase (not a cermet) as a thermal spraying powder is shown as Comparative Example 2 (see Table 5). In Comparative Example 2, the raw material powder for thermal spraying is different from that of Example 16, but the same is true for other conditions such as thermal spraying conditions.
＜実施例１６、比較例２の評価＞
＜金属母材との密着性評価＞
　実施の形態２の実施例１６、比較例２について、金属母材の表面に形成した溶射層の密着性を評価した。密着性評価はねじり試験機を用いて行った。試験方法は、ねじり試験機に取り付けられるような試験片を作成し、試験片の一端を固定し、他端を回転させて行った（図１参照）。回転により、溶射層に剥離又はクラックを生じた時のトルク値を溶射層の密着力とした。実施例１６の密着力は大きく高い値を示したが、比較例２は低いトルク値を示した。その結果を表６に示す。 <Evaluation of Example 16 and Comparative Example 2>
<Evaluation of adhesion to metal matrix>
For Example 16 of Comparative Example 2 and Comparative Example 2, the adhesion of the thermal spray layer formed on the surface of the metal base material was evaluated. The adhesion evaluation was performed using a torsion tester. The test method was performed by preparing a test piece that can be attached to a torsion tester, fixing one end of the test piece, and rotating the other end (see FIG. 1). The torque value when peeling or cracking occurred in the sprayed layer by rotation was defined as the adhesion of the sprayed layer. The adhesion strength of Example 16 was large and high, while Comparative Example 2 showed a low torque value. The results are shown in Table 6.
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000006
　以上説明したように、本発明の熱中性子遮蔽材料は、優れた耐食性、および熱中性子遮断性を維持しつつ、高硬度材料であり、耐食耐摩耗に優れた材料であり、肉厚を薄くすることが可能となり、使用済核燃料の貯蔵密度を増加することができる。
さらに、本発明の熱中性子遮蔽材料は、使用済核燃料の輸送時や保管時の塩水、水等の雰囲気に対する十分な耐食性を有しており、熱中性子遮断性を要する部材に広く適用でき、産業上の利用可能性が極めて高い。 As described above, the thermal neutron shielding material of the present invention is a high-hardness material, a material excellent in corrosion resistance and wear resistance, and has a thin wall thickness while maintaining excellent corrosion resistance and thermal neutron shielding properties. And storage density of spent nuclear fuel can be increased.
Furthermore, the thermal neutron shielding material of the present invention has sufficient corrosion resistance to the atmosphere of salt water, water, etc. during transportation and storage of spent nuclear fuel, and can be widely applied to members that require thermal neutron shielding. The above availability is extremely high.

Claims (7)

  1. 金属母材上にサーメット層を有する熱中性子遮蔽材料であって、前記サーメット層が、ＭＭ’Ｂ又はＭ２Ｍ’Ｂ２（Ｍ，Ｍ’＝遷移金属）型三元硼化物と、Ｍ’金属相と、からなるサーメットであることを特徴とする熱中性子遮蔽材料。 A thermal neutron shielding material having a cermet layer on a metal base material, wherein the cermet layer is an MM′B or M 2 M′B 2 (M, M ′ = transition metal) type ternary boride, and M ′ A thermal neutron shielding material characterized by being a cermet comprising a metal phase.
  2. 前記サーメット層が、二元硼化物をさらに有することを特徴とする請求項１に記載の熱中性子遮蔽材料。 The thermal neutron shielding material according to claim 1, wherein the cermet layer further includes a binary boride.
  3. 前記サーメット層が、Ｍ２Ｍ’Ｂ２型複硼化物とＭ’基合金の結合相よりなる複硼化物サーメットであることを特徴とする（Ｍ＝Ｍｏ，Ｍ’＝ＮｉまたはＦｅ）請求項１記載の熱中性子遮蔽材料。 The cermet layer is a double boride cermet composed of a binder phase of M2M′B2 type double boride and an M′-based alloy (M = Mo, M ′ = Ni or Fe). Thermal neutron shielding material.
  4. 前記サーメット層は、複硼化物よりなる硬質相３５～９５質量％と、残部が該硬質相を結合するＮｉ基合金の結合相とからなり、Ｂ含有量が３～７．５質量％、Ｍｏ含有量が、Ｍｏ／Ｂ原子比で０．８～（１．６－０．０５Ｘ）（Ｘ：含有するＢの質量％、以下のＸ表記において同じ）、Ｃｒ含有量が（５５－５Ｘ）％以下、残部が１０質量％以上のＮｉ、および不可避的不純物よりなることを特徴とする請求項３に記載の熱中性子遮蔽材料。 The cermet layer is composed of 35 to 95% by mass of a hard phase made of a double boride, and the balance is a Ni-base alloy bonded phase that binds the hard phase, with a B content of 3 to 7.5% by mass, Mo Content is 0.8 to (1.6-0.05X) in terms of Mo / B atomic ratio (X:% by mass of B contained, the same in the following X notation), and Cr content is (55-5X) The thermal neutron shielding material according to claim 3, wherein the thermal neutron shielding material is made up of Ni of not more than 10%, the balance being 10% by mass or more, and inevitable impurities.
  5. 前記サーメット層は、複硼化物よりなる硬質相３５～９５質量％と、残部が該硬質相を結合するＦｅ基合金の結合相とからなり、Ｂ含有量が、３～７．５質量％、Ｍｏ含有量が、Ｍｏ／Ｂ原子比で０．８～（１．６－０．０５Ｘ）、Ｃｒおよび／又はＮｉ含有量が、いずれか一方または両者の合計で（５５－５Ｘ）％質量以下、Ｃ含有量が、０．９５質量％以下、残部が１０質量％以上のＦｅ、および不可避的不純物よりなることを特徴とする請求項３に記載の熱中性子遮蔽材料。 The cermet layer is composed of 35 to 95% by mass of a hard phase made of a double boride, and the balance is an Fe-based alloy binder phase that binds the hard phase, and the B content is 3 to 7.5% by mass, Mo content is 0.8 to (1.6-0.05X) in terms of Mo / B atomic ratio, and Cr and / or Ni content is (55-5X)% or less by mass of either one or both The thermal neutron shielding material according to claim 3, wherein the C content is 0.95 mass% or less, the balance is Fe of 10 mass% or more, and unavoidable impurities.
  6. 前記金属母材は、普通鋼、合金鋼、工具鋼、ステンレス鋼又はアルミニウム合金であることを特徴とする請求項１～５のいずれかに記載の熱中性子遮蔽材料。 The thermal neutron shielding material according to any one of claims 1 to 5, wherein the metal base material is plain steel, alloy steel, tool steel, stainless steel, or aluminum alloy.
  7. 請求項１～５のいずれかに記載の熱中性子遮蔽材料の製造方法であって、
    前記サーメット層を金属母材上に溶射によって形成することを特徴とする熱中性子遮蔽材料の製造方法。     A method for producing a thermal neutron shielding material according to any one of claims 1 to 5,
    A method of manufacturing a thermal neutron shielding material, wherein the cermet layer is formed on a metal base material by thermal spraying.
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