Rotating positive electrode for x-ray tube, x-ray tube, x-ray inspection device, and method for manufacturing rotating positve electrode for x-ray tube

Abstract

A rotating positive electrode for an X-ray tube according to an embodiment is formed by laminating at least a target layer that generates X-rays by receiving thermal electrons, a first base layer, and a second base layer. The target layer of the rotating positive electrode for an X-ray tube contains one among tungsten, molybdenum, niobium, tantalum, rhenium, titanium, zirconium, and vanadium as a main component. The first base layer contains molybdenum as a main component and at least one carbide selected from titanium carbide, hafnium carbide, zirconium carbide, tantalum carbide, and niobium carbide. The second base layer contains molybdenum as a main component, and has lower oxygen content and carbon content than the first base layer.

Description

Rotating anode for X-ray tube, X-ray tube, X-ray inspection device, and method for manufacturing rotating anode for X-ray tube

[0001] FIELD Embodiments of the present invention relate to a rotating anode for an X-ray tube, an X-ray tube, an X-ray inspection device, and a method for manufacturing a rotating anode for an X-ray tube.

[0002] To generate X-rays from an X-ray tube, an electric current is passed through the cathode filament of the X-ray tube to heat the cathode, and the thermions emitted by the heating are accelerated by a high voltage (also called tube voltage) applied between the cathode and the anode (target) and collide with the target layer of the anode. X-rays are generated when thermions collide with the target layer. In rotating anode X-ray tubes, the anode is rotated at a high speed to obtain the X-ray output required by the market without compromising the durability of the X-ray tube.

[0003] Rotating anodes for X-ray tubes have a laminated structure consisting of a target layer and a high-strength base layer. A molybdenum (Mo) alloy with improved high-temperature strength is the TZM alloy, which is composed of 0.5 wt% Ti, 0.07 wt% Zr, 0.05 wt% carbon, and the balance Mo. The TZM alloy has excellent high-temperature strength due to the high melting point of its main component, molybdenum. Taking advantage of this property, it is used in fields requiring high-temperature strength, such as rotating anodes for X-ray tubes.

[0004] However, when this TZM alloy is used in a rotating anode for an X-ray tube, the base layer does not have sufficient gas emission characteristics, so impurities such as oxygen and carbon in the alloy are gasified, resulting in a problem of frequent discharges in the gas of the X-ray tube.

[0005] Patent No. 5238259

[0006] The problem to be solved by the present invention is to reduce the number of discharges of the X-ray tube without causing vibration problems of the X-ray tube caused by thermal deformation of the target layer.

[0007] A rotating anode for an X-ray tube according to an embodiment is formed by stacking at least a target layer that receives thermoelectrons to generate X-rays, a first base layer, and a second base layer. The target layer of the rotating anode for an X-ray tube contains one of tungsten, molybdenum, niobium, tantalum, rhenium, titanium, zirconium, and vanadium as a primary component. The first base layer contains molybdenum as a primary component and at least one carbide selected from titanium carbide, hafnium carbide, zirconium carbide, tantalum carbide, and niobium carbide. The second base layer contains molybdenum as a primary component and has a lower oxygen content and carbon content than the first base layer.

[0008] 2. A schematic top view showing a structural example of a rotating anode for an X-ray tube according to an embodiment. A schematic II-II cross-sectional view showing a structural example of a rotating anode for an X-ray tube according to an embodiment. A schematic side view showing a structural example of a rotating anode for an X-ray tube according to an embodiment. A schematic II-II cross-sectional view showing a first other modified example of the structural example of the rotating anode for an X-ray tube shown in FIG. 2. A schematic II-II cross-sectional view showing a second other modified example of the structural example of the rotating anode for an X-ray tube shown in FIG. 2. A schematic II-II cross-sectional view showing a third other modified example of the structural example of the rotating anode for an X-ray tube shown in FIG. 2. A schematic II-II cross-sectional view showing a fourth other modified example of the structural example of the rotating anode for an X-ray tube shown in FIG. 2. A schematic diagram showing a structural example of an X-ray tube including a rotating anode for an X-ray tube according to an embodiment. A schematic II-II cross-sectional view showing a structural example of a rotating anode for an X-ray tube according to Comparative Example 2. Embodiment

[0009] Hereinafter, embodiments of a rotating anode for an X-ray tube, an X-ray tube, an X-ray inspection device, and a method for manufacturing a rotating anode for an X-ray tube will be described in detail with reference to the drawings.

[0010] Fig. 1 is a top view showing an example of the structure of a rotating anode for an X-ray tube according to an embodiment. Fig. 2 is a cross-sectional view taken along line II-II showing an example of the structure of a rotating anode for an X-ray tube according to an embodiment. Fig. 3 is a side view showing an example of the structure of a rotating anode for an X-ray tube according to an embodiment. Figs. 4 to 7 are cross-sectional views taken along line II-II showing other examples of the structure of the rotating anode for an X-ray tube shown in Fig. 2.

[0011] 1 to 7 show a rotating anode for an X-ray tube (hereinafter simply referred to as "anode") 102 and a rotor 103 according to an embodiment. The anode 102 has a cylindrical through-hole, with its thickness direction being its height direction, for inserting the rotor 103. The anode 102 is formed by laminating at least a target layer 102A, a first base layer (carbide-added layer) 102B, and a second base layer (pure molybdenum layer) 102C. In other words, the anode 102 has a structure with at least three layers.

[0012] The anode 102 may further include a coating material 102D on at least a portion of the anode 102 excluding the top surface. As shown in FIGS. 4 to 7 , the direction in which the first base layer 102B is stacked on the second base layer 102C is considered the top surface (the top surface of the paper in FIGS. 4 to 7 ). FIGS. 4 to 7 show examples in which the coating material 102D is provided on part or the entire side or back surface of the anode 102, and each example shows an example in which the method of disposing the coating material 102D is changed. The coating material 102D may be provided on the entire side (or part) of the second base layer 102C and the entire back surface (or part) of the anode 102 (as shown in FIG. 4 ). Alternatively, the coating material 102D may be provided on the entire side (or part) of the side surface of the anode 102 and the entire back surface (or part) of the anode 102 (as shown in FIG. 5 ). Alternatively, the coating material 102D may be provided only on the entire side surface (or a portion of the side surface) of the second base layer 102C (as shown in FIG. 6), or the coating material 102D may be provided only on the entire back surface (or a portion of the back surface) of the anode 102 (as shown in FIG. 7), or a combination thereof may be used.

[0013] The coating material 102D may contain oxide ceramics. Examples of the oxide ceramics include titanium oxide, aluminum oxide, silicon oxide, and zirconium oxide. The oxide ceramics may be a combination of two or more types of oxide ceramics. Examples of the combination of two or more types of oxide ceramics include Ti, ２ O ３ -Al ２ O ３ Unless otherwise specified, the following description will be given for the case of FIG. 2, not for the case of FIG.

[0014] The anode 102 is an electrode having a roughly disk shape. The anode 102 rotates as the rotor 103 rotates around the central axis D of rotation. A high tube voltage is applied between the cathode 101 (shown in FIG. 8 ) and the anode 102. Thermoelectrons emitted from the cathode collide with a target layer 102A, which is the surface of the anode 102 facing the cathode 101, due to the action of the tube voltage. The target layer 102A of the anode 102 receives the thermoelectrons and generates X-rays.

[0015] The first and second base layers 102B and 102C of the anode 102 are formed by dividing the single base layer 102E of the anode 102' according to Comparative Example 2 shown in FIG. 9 into two layers in the thickness direction. In other words, the combined thickness of the first and second base layers 102B and 102C of the anode 102 is approximately equal to the thickness of the single base layer 102E. It is also desirable that the thickness of the first base layer 102B near its center and the thickness of the second base layer 102C are approximately the same. For example, if the thickness of the base layer 102E of the anode 102' is 20 mm, the thickness of the first base layer 102B near its center and the thickness of the second base layer 102C are 10 mm.

[0016] The target layer 102A is mainly composed of any one of tungsten (W), molybdenum (Mo), niobium (Nb), tantalum (Ta), rhenium (Re), titanium (Ti), zirconium (Zr), and vanadium (V).

[0017] The first base layer 102B contains molybdenum as a main component and at least one of titanium carbide, hafnium carbide, zirconium carbide, tantalum carbide, and niobium carbide. In other words, the first base layer 102B contains carbides as additives and iron (Fe) as an inevitable impurity in the raw material powder, resulting in high strength. Furthermore, it is preferable that the oxygen content of the first base layer 102B be 300 ppm or less and the carbon content be 400 ppm or more and 1000 ppm or less. It is even more preferable that the carbon content be 400 ppm or more and 600 ppm or less.

[0018] The second base layer 102C contains molybdenum as a primary component and has a lower oxygen content and carbon content than the first base layer 102B. Preferably, the second base layer 102C has an oxygen content of 30 ppm or less and a carbon content of 400 ppm or less, which are lower than the first base layer 102B. Because the second base layer 102C does not contain carbides as additives like the first base layer 102B (although they may be contained as impurities), the second base layer 102C has a lower carbon content than the first base layer 102B and exhibits superior gas release characteristics. On the other hand, the anode 102' according to Comparative Example 2 shown in FIG. 9 has a base layer 102E, which is made of a single layer of the same material, but is made of a TZM alloy. Although it has high strength, it exhibits inferior gas release characteristics.

[0019] Furthermore, the difference in oxygen content between the first base layer 102B and the second base layer 102C is preferably 5 ppm to 300 ppm, more preferably 10 ppm to 250 ppm. On the other hand, the difference in carbon content between the first base layer 102B and the second base layer 102C is preferably 100 ppm to 300 ppm. It is preferable that the first base layer 102B and the second base layer 102C each have a thickness of 0.5 mm or more, and the thickness ratio between the first base layer 102B and the second base layer 102C is preferably 1 / 6 to 6.

[0020] The oxygen and carbon contents are measured at four locations and the average values ​​are used. The four measurement locations are offset by 90 degrees on the disk, excluding the surface layer and the joints. Measurements are performed under the same conditions for both the first substrate layer 102B and the second substrate layer 102C. Numerical values ​​that do not indicate a lower limit of the content indicate that the content may be 0 (below the detection limit).

[0021] The oxygen content is measured by inert gas fusion-infrared absorption method. The oxygen content is measured using a LECO ON836 or a device with equivalent or better performance. The carbon content is measured by high-frequency induction furnace combustion-infrared absorption method. The carbon content is measured using a HORIBA EMIA-920V2 or a device with equivalent or better performance.

[0022] Furthermore, adding carbide only to the first base layer 102B of the first and second base layers 102B and 102C means that the crystal grain size (e.g., average crystal grain size) of the first base layer 102B is smaller than the crystal grain size (e.g., average crystal grain size) of the second base layer 102C. Adding carbide to the first base layer 102B suppresses grain growth within the first base layer 102B. The average crystal grain size of the first base layer 102B is, for example, smaller than the average crystal grain size of the second base layer 102C and is 40 μm or more and 130 μm or less. The average crystal grain size of the first base layer 102B is, for example, 40 μm or more and less than 100 μm. The average crystal grain size of the second base layer 102C is, for example, larger than the average crystal grain size of the first base layer 102B and is 80 μm or more and 250 μm or less. The average crystal grain size of the second base layer 102C is, for example, not less than 80 μm and less than 180 μm.

[0023] For example, the ratio of the average crystal grain size of the first base layer 102B to the average crystal grain size of the second base layer 102C is less than 0.8. The average crystal grain size of the first base layer 102B is preferably 50 μm or more and 90 μm or less. The average crystal grain size of the second base layer 102C is preferably 90 μm or more and 150 μm or less. The average crystal grain sizes of the first base layer 102B and the second base layer 102C can be determined by a cutting method. In the cutting method, the anode 102 is cut in the thickness direction, and the cross section is polished and etched, and the obtained observation surface is observed under a microscope. The observation field should be three or more fields per base layer, and should not be biased to a specific position.

[0024] Furthermore, adding carbide only to the first base layer 102B of the first and second base layers 102B and 102C means that the Vickers hardness of the first base layer 102B is greater than that of the second base layer 102C. The Vickers hardness of the first base layer 102B is, for example, greater than that of the second base layer 102C and is 150 Hv or greater and 300 Hv or less. The Vickers hardness of the first base layer 102B is, for example, greater than 205 Hv and 300 Hv or less. The Vickers hardness of the second base layer 102C is, for example, smaller than that of the first base layer 102B and is 130 Hv or greater and 200 Hv or less. The Vickers hardness of the second base layer 102C is, for example, greater than 160 Hv and 200 Hv or less.

[0025] The ratio of the Vickers hardness of the first base layer 102B to the Vickers hardness of the second base layer 102C is, for example, greater than 1.1. It is desirable that the ratio of the Vickers hardness of the first base layer 102B to the Vickers hardness of the second base layer 102C is, for example, greater than 1.3. The Vickers hardness of the first base layer 102B is preferably 210 Hv or more and 270 Hv or less. The Vickers hardness of the second base layer 102C is preferably 170 Hv or more and 180 Hv or less. The Vickers hardness is based on JIS Z 2244.

[0026] The bending strength of the first base layer 102B at room temperature is, for example, 700 MPa or more. It is preferable that the bending strength of the first base layer 102B at room temperature exceeds, for example, 710 MPa. On the other hand, it is preferable that the bending strength is 1500 MPa or less. If the bending strength is too high, it may have a negative effect on processability, and this is not preferable. With the above configuration, sufficient strength can be obtained. The bending strength is based on JIS_R_1601.

[0027] The rotor 103 is an external member of the anode 102 and is a rotator that axially supports the anode 102. The rotor 103 is provided so that the anode 102 can rotate around a rotation axis.

[0028] Fig. 8 is a schematic diagram showing the configuration of an X-ray tube equipped with an anode 102. In Fig. 8, the same members as those shown in Figs. 1 to 4 are given the same reference numerals and their explanations will be omitted.

[0029] FIG. 8 shows an X-ray tube 1 including an anode 102. The X-ray tube 1 is used in an X-ray inspection device. For example, X-ray inspection devices include inspection devices in the medical field (general X-ray imaging devices, mammography devices, X-ray CT (Computed Tomography) devices, X-ray therapy devices, etc.) and inspection devices in the scientific and industrial fields (e.g., X-ray diffraction devices, X-ray fluorescence analysis devices, non-destructive testing devices, material inspection devices for thickness etc., airport baggage inspection devices, etc.). The X-ray tube 1 has an X-ray tube housing 10. The X-ray tube housing 10 is a housing made of glass, metal, or the like, whose interior is maintained under vacuum. The X-ray tube housing 10 houses a cathode 101, an anode 102, and a rotor 103.

[0030] The cathode 101 has a filament formed of a metal such as tungsten or nickel in the shape of a thin wire. The cathode 101 is connected to an X-ray high voltage device (not shown) via a cable or the like. The cathode 101 generates heat and emits thermoelectrons when a cathode voltage and a filament current are applied from the X-ray high voltage device.

[0031] Thermoelectrons emitted from the cathode 101 collide with a focal position F of the target layer 102A of the anode 102 due to the action of the tube voltage. The target layer 102A of the anode 102 receives the thermoelectrons at the focal position F and generates X-rays. By rotating the anode 102 around the central axis of rotation D, the X-ray tube 1 generates X-rays while shifting the focal position F on the target layer 102A.

[0032] Bearings (not shown) are connected to both ends of the rotor 103. A stator coil 104 is attached to the outside of the X-ray tube housing 10 so as to surround the rotor 103. The stator coil 104 is housed in the X-ray tube 1. The stator coil 104 is connected to a rotor drive power supply (not shown) and receives power from the rotor drive power supply to rotate the rotor 103 according to the principle of electromagnetic induction. The anode 102 rotates around the central axis of rotation D in conjunction with the rotation of the rotor 103.

[0033] Next, a description will be given of a method for manufacturing the anode 102. Although there are no particular limitations on the method for manufacturing the anode 102, the following method can be given as a preferred method.

[0034] First, tungsten powder and rhenium powder are prepared as raw material powder for the target layer 102A of the anode 102 and mixed using a ball mill or the like. The rhenium content is preferably, for example, 2 wt % to 12 wt %. As raw material powder for the first base layer 102B of the anode 102, molybdenum powder containing inevitable impurities and carbide powder are prepared and mixed using a ball mill or the like. The molybdenum powder contains iron (Fe) as an inevitable impurity at a concentration of 5 ppm to 100 ppm. Preferably, the iron concentration is 5 ppm to 50 ppm. More preferably, the iron concentration is 5 ppm to 30 ppm. The molybdenum powder also contains nickel (Ni) as an inevitable impurity at a concentration of 5 ppm to 40 ppm. Preferably, the nickel concentration is 5 ppm to 20 ppm. The molybdenum powder also contains potassium (K) as an inevitable impurity at a concentration of 5 ppm to 30 ppm. Preferably, the potassium concentration is 5 ppm to 20 ppm. The total of iron (Fe), nickel (Ni), and potassium (K) as inevitable impurities is 15 ppm to 100 ppm. The total of the inevitable impurities is preferably 15 ppm to 60 ppm. The carbide powder is, for example, at least one of titanium carbide, hafnium carbide, zirconium carbide, tantalum carbide, and niobium carbide, and the total content of the carbide powder is selected to be 0.2 wt% to 1.5 wt% in the mixed powder. Because of the inclusion of carbide, the first base layer 102B can maintain higher strength than the second base layer 102C. If the average particle size of the carbide powder is smaller than that of the molybdenum powder, the carbide is more likely to be dispersed uniformly in the grain boundary phase of the molybdenum.

[0035] On the other hand, molybdenum powder is prepared as raw material powder for the second base layer 102C of the anode 102. The molybdenum powder for the first base layer 102B and the molybdenum powder for the second base layer 102C are the same. That is, the molybdenum powder contains iron (Fe) as an inevitable impurity at 5 ppm to 100 ppm. Preferably, the iron content is 5 ppm to 50 ppm. More preferably, the iron content is 5 ppm to 30 ppm. The molybdenum powder also contains nickel (Ni) as an inevitable impurity at 5 ppm to 40 ppm. Preferably, the nickel content is 5 ppm to 20 ppm. The molybdenum powder also contains potassium (K) as an inevitable impurity at 5 ppm to 30 ppm. Preferably, the potassium content is 5 ppm to 20 ppm. The total content of inevitable impurities, iron (Fe), nickel (Ni), and potassium (K), is 15 ppm or more and 100 ppm or less. The total content of the inevitable impurities is preferably 15 ppm or more and 60 ppm or less. Although the strength of the second base layer 102C is inferior to that of the first base layer 102B, as described above, the molybdenum powder contains iron as an inevitable impurity, so the second base layer 102C can also maintain sufficient strength. In addition, the strength of the second base layer 102C can also be adjusted by controlling the crystal grain size (making it smaller to a certain extent).

[0036] Next, the mixed raw material powder for the target layer 102A, the mixed raw material powder for the first base layer 102B, and the raw material powder for the second base layer 102C are layered and placed in a mold, and molded at a pressure of 200 MPa or more to obtain a compact. As an example of a thickness ratio between the first base layer 102B and the second base layer 102C being 1 / 6 or more and 6 or less, the raw material powder for the first base layer 102B is layered to a thickness of 1 / 2 of the entire base layer (10 mm when the entire base layer is 20 mm thick), and the raw material powder for the second base layer 102C is layered to a thickness of 1 / 2 of the entire base layer (10 mm when the entire base layer is 20 mm thick). The thickness of the second base layer 102C may be greater than the thickness of the first base layer 102B. This is because increasing the proportion of the second base layer 102C improves gas release characteristics and also improves the cooling effect of the target layer 102A by radiative cooling. In this case, the strength of the anode 102 is adjusted by controlling the crystal grain size of the second base layer 102C to be small. The molding pressure is preferably 200 to 500 MPa. If the molding pressure is less than 200 MPa, the density of the molded body is insufficient, making it difficult to obtain a high-density sintered body. On the other hand, if the molding pressure exceeds 500 MPa, cracks are likely to occur in the molded body, which is not preferable.

[0037] Next, the compact is sintered. In order to minimize the influence of oxygen in the sintering process, it is preferable that the sintering atmosphere be an inert gas atmosphere or a reducing (hydrogen) atmosphere. In this case, sintering is performed at 1800°C to 2500°C for 1 to 24 hours. Sintering is preferably performed at 2000°C to 2200°C. Furthermore, as an example of a configuration in which the coating material 102D is provided on at least a portion of the anode 102 except for the top surface, a Ti coating is provided on at least a portion of the side peripheral surface and back surface of the anode 102. ２ O ３ -Al ２ O ３ The coating layer 102D is formed by plasma spraying the thermal spray material of the above system in the atmosphere (as shown in FIGS. 4 to 7). After that, the anode 102 is manufactured through a forging process and a machining process.

[0038] The anode 102 is composed of a target layer 102A mainly made of tungsten and containing rhenium, a first base layer 102B mainly made of molybdenum with carbide added, and a second base layer 102C mainly made of molybdenum.

[0039] Here, the target layer 102A of the anode 102 has a relative density of 90% or more, and the material may contain at least one of tungsten (W), molybdenum (Mo), niobium (Nb), tantalum (Ta), rhenium (Re), titanium (Ti), zirconium (Zr), and vanadium (V) as its main component.

[0040] The first base layer 102B of the anode 102 may be a base material containing 0.2 to 1.5 wt % of at least one of titanium carbide, hafnium carbide, zirconium carbide, and tantalum carbide, with the remainder being molybdenum.

[0041] The anode 102 according to the embodiment described below was manufactured using the above-described manufacturing method. The raw material powder for the target layer 102A of the anode 102 was a mixed powder containing 10 wt% rhenium powder and 90 wt% tungsten powder. The raw material powder for the first base layer 102B of the anode 102 was a ball mill mixture of molybdenum powder containing inevitable impurities and carbide powders of titanium carbide and zirconium carbide. The titanium carbide ratio was 0.5 wt% and the zirconium carbide ratio was 0.08 wt%. The raw material powder for the second base layer 102C of the anode 102 was the same molybdenum powder used as the raw material for the first base layer 102B. The inevitable impurities in the molybdenum powder used were 20 ppm iron, 15 ppm nickel, and 10 ppm potassium.

[0042] Using these raw material powders, anodes 102 according to the examples described below were manufactured using the manufacturing method described above. The sintering process was carried out at 2100°C for 12 hours in a hydrogen atmosphere. The thickness of the first base layer 102B of the sintered body was 10 mm, and the thickness of the second base layer 102C was 10 mm. The thicknesses of the base layers 102B and 102C were measured using a scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDX). The anode 102 was cut in the thickness direction, and the cross section was polished and etched to obtain an observation surface. The thickness of the first base layer 102B was determined using SEM and EDX from the range in which carbides were detected in the first base layer. The thickness of the second base layer 102C is the difference between the thickness of the anode 102 and the thickness of the first base layer 102B.

[0043] The oxygen and carbon contents were measured for each base layer of the sintered body corresponding to the anode 102 according to the example. The measurement results for the oxygen and carbon contents are shown in Table 1. As shown in Table 1, in the sintered body corresponding to Example 1, the oxygen content of the first base layer 102B was 200 ppm, and the carbon content was 550 ppm. Similarly, in the sintered body corresponding to Example 1, the oxygen content of the second base layer 102C was less than 10 ppm (detection limit), and the carbon content was 300 ppm. Although the oxygen content of the first base layer 102B of the sintered body corresponding to Example 1 was 200 ppm, it was confirmed that the number of discharges was zero or nearly zero if the oxygen content was at least 300 ppm or less. Meanwhile, the oxygen and carbon contents were also measured for each base layer of Comparative Example 1, which was manufactured using a molybdenum powder under different reduction conditions as the raw material powder and by a method similar to that of the example.

[0044] The crystal grain size (e.g., average crystal grain size) and Vickers hardness were measured for each base layer for the sintered body corresponding to the Example and the sintered body corresponding to Comparative Example 1. The bending strength of the first base layer was also measured for the sintered body corresponding to the Example and the sintered body corresponding to Comparative Example 1. The measurement results of the crystal grain size, Vickers hardness, and bending strength are shown in Table 2.

[0045]

[0046]

[0047] The anode 102 according to the example was incorporated into an X-ray tube 1, and a 20,000-cycle test was performed to check the number of discharges of the anode 102. The number of discharges was also checked for the anode according to Comparative Example 1. In addition, an anode 102' (shown in FIG. 9 ) according to Comparative Example 2, in which the base layer 102E made of the same material (single layer) is made of a TZM alloy and has inferior gas release characteristics, was incorporated into an X-ray tube, and a 20,000-cycle test was performed to check the number of discharges of the anode 102'. The measurement results of the number of discharges are shown in Table 3. No vibration failure occurred in the X-ray tube 1 equipped with the anode 102 according to the example, the anode according to Comparative Example 1, or the X-ray tube equipped with the anode 102' according to Comparative Example 2.

[0048] On the other hand, in the X-ray tube 1 equipped with the anode 102 according to the embodiment, the number of discharges of the anode 102 was 0 to 3, whereas in the X-ray tube equipped with the anode according to Comparative Example 1 and the X-ray tube equipped with the anode 102' according to Comparative Example 2, discharges with the anode 102' occurred 15 times.

[0049]

[0050] In the above example, the anode 102 is formed by stacking the target layer 102A, the first base layer 102B, and the second base layer 102C in this order, but this is not limited to this case. Also, although the anode 102 has been described as having two base layers (the first base layer 102B and the second base layer 102C), this is not limited to this case. For example, the anode 102 may have three or more base layers. For example, in the case of a three-layer anode, the base layers are stacked in the order of the first base layer 102B, the second base layer 102C, and the first base layer 102B.

[0051] As described above, with the anode 102 and the X-ray tube 1 including it, the first base layer 102B can sufficiently maintain the strength of the anode 102, while the second base layer 102C can improve the gas release characteristics of the anode 102. As a result, with the anode 102 and the X-ray tube 1 including it, the number of discharges of the X-ray tube 1 can be reduced without causing vibration problems of the X-ray tube 1 that would otherwise occur due to thermal deformation of the target layer.

[0052] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents.

Claims

1. A rotating anode for an X-ray tube, comprising at least a target layer which receives thermoelectrons and generates X-rays, a first base layer and a second base layer, wherein the target layer is primarily composed of any of tungsten, molybdenum, niobium, tantalum, rhenium, titanium, zirconium and vanadium, the first base layer is primarily composed of molybdenum and contains at least one type of carbide selected from the group consisting of titanium carbide, hafnium carbide, zirconium carbide, tantalum carbide and niobium carbide, and the second base layer is primarily composed of molybdenum and has a lower oxygen content and carbon content than the first base layer.

2. The rotating anode for an X-ray tube according to claim 1, wherein the first base layer has an oxygen content of 300 ppm or less and a carbon content of 400 ppm or more and 1000 ppm or less.

3. The rotating anode for an X-ray tube according to claim 2, wherein the second base layer has an oxygen content of 30 ppm or less and a carbon content of 400 ppm or less.

4. A rotating anode for an X-ray tube as set forth in claim 1, wherein the crystal grain size of said first base layer is smaller than the crystal grain size of said second base layer.

5. A rotating anode for an X-ray tube as set forth in claim 1, wherein the Vickers hardness of said first base layer is greater than the Vickers hardness of said second base layer.

6. A rotating anode for an X-ray tube as described in claim 1, further comprising a coating material containing at least one of titanium oxide, aluminum oxide, silicon oxide, and zirconium oxide on the side peripheral surfaces of said first base layer and said second base layer and on the back surface of said second base layer.

7. The rotating anode for an X-ray tube according to claim 1, wherein the bending strength of the first base layer at room temperature is 700 MPa or more.

8. An X-ray tube comprising: a cathode that emits thermoelectrons; the rotating anode for an X-ray tube according to any one of claims 1 to 7; and a rotor that axially supports the rotating anode for an X-ray tube.

9. An X-ray inspection device comprising the X-ray tube according to claim 8.

10. A method for manufacturing a rotating anode for an X-ray tube, comprising the steps of: laminating raw material powder; and sintering the raw material powder in an inert gas atmosphere or a reducing atmosphere to manufacture the rotating anode for an X-ray tube according to any one of claims 1 to 7.

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