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WO-2026094923-A1 - X-RAY TUBE TARGET AND METHOD FOR PRODUCING SAME

WO2026094923A1WO 2026094923 A1WO2026094923 A1WO 2026094923A1WO-2026094923-A1

Abstract

The present invention provides an X-ray tube target for which it is possible to improve bonding strength while maintaining practical heat resistance and mechanical properties. Also provided is a method for producing such target.　One embodiment provides an X-ray tube target comprising a molybdenum alloy substrate, a carbon substrate, and an alloy layer disposed between the molybdenum alloy substrate and the carbon substrate. The alloy layer contains a solid solution formed from at least two elements selected from the group consisting of Ti, V, Zr, Nb, Mo, Ta, and W. The minimum hardness of the alloy layer is at least 70% of the maximum hardness.

Inventors

  • MORI, YOICHIRO
  • SUENAGA, SEIICHI
  • MIZOBE, Masanori

Assignees

  • 株式会社Niterra Materials

Dates

Publication Date
20260507
Application Date
20251028
Priority Date
20241031

Claims (8)

  1. Carbon substrate and Molybdenum alloy substrate and The carbon substrate and the molybdenum alloy substrate are joined together by an alloy layer containing a solid solution made of at least two elements selected from the group consisting of Ti, V, Zr, Nb, Mo, Ta, and W. An X-ray tube target wherein the minimum hardness of the alloy layer is 70% or more of the maximum hardness.
  2. The X-ray tube target according to claim 1, wherein the solid solution is at least one selected from the group consisting of MoNbTi alloy, NbTi alloy, and ZrNb alloy.
  3. The X-ray tube target according to claim 1, wherein the hardness of the alloy layer is measured in Vickers hardness.
  4. The X-ray tube target according to claim 1, wherein the alloy layer contains a metal carbide.
  5. A method for manufacturing an X-ray tube target, comprising the step of joining a carbon substrate and a molybdenum alloy substrate using a material integrally molded from a material consisting of at least one element selected from the group consisting of Ti, V, Zr, and Mo, and a material consisting of at least one element selected from the group consisting of Nb, Ta, and W.
  6. The method for manufacturing an X-ray tube target according to claim 5, further comprising the step of preparing the integrally molded material using cladding, chemical vapor deposition, or screen printing, prior to the joining process.
  7. The method for manufacturing an X-ray tube target according to claim 5, wherein, before the joining, a first brazing layer is placed between the integrally molded material and the molybdenum alloy substrate, and a second brazing layer is placed between the integrally molded material and the carbon substrate.
  8. The integrally molded material includes a core material made of at least one element selected from the group consisting of Nb, Ta, and W; a first surface material formed on one surface of the core material and in contact with the first brazing layer; and a second surface material formed on the other surface of the core material and in contact with the second brazing layer. The method for manufacturing an X-ray tube target according to claim 7, wherein the first surface material and the second surface material each contain at least one element selected from the group consisting of Ti, V, Zr, and Mo.

Description

X-ray tube target and method for manufacturing the same Embodiments of the present invention relate to an X-ray tube target and a method for manufacturing the same. Medical CT scanners, aiming for higher resolution, often employ rotating anodes that provide high X-ray output. High output requires a high energy electron beam to irradiate the target. Rotating anodes enable high-power irradiation while suppressing target degradation by rotating the target relative to the electron beam, constantly changing the focal point. However, targets irradiated with high-energy electron beams within a vacuum tube must possess high heat resistance and sufficient heat volume for continuous operation. While molybdenum alloys are used to meet the heat resistance requirements described above, in recent years, to improve inspection speed, the diameter of the anode has been increased to allow imaging of a wider area at once. However, this increase in diameter has led to an increase in the target weight and a greater load on the rotor shaft. Therefore, it is being considered to reduce weight while maintaining the size of the irradiation surface and heat volume by replacing a portion of the molybdenum alloy with graphite, which combines heat resistance and lightweight properties. The joining of molybdenum alloy and graphite requires the use of joining materials and methods that take into account sufficient heat resistance and mechanical properties for practical use in X-ray tubes. A schematic cross-sectional view showing an enlarged view of the joint portion of a cross-section along the stacking direction of an X-ray tube target according to the embodiment.Figure 1 is a schematic cross-sectional view showing the measurement points for Vickers hardness of an X-ray tube target.A schematic magnified view of the area around the micro-Vickers indentation shown in Figure 2.A cross-sectional view showing an example of an X-ray tube target according to the embodiment. For example, Patent Documents 1 and 2 describe joining by combining multiple high-melting-point metals and their alloys, and then solidifying a portion of these components. High-power X-ray tubes used for specific applications require that the joint layer maintain its structure without melting even when exposed to high temperatures of 1600°C. Zr is an example of a brazing material that wets well to both molybdenum alloy substrates and carbon substrates. Zr undergoes a eutectic reaction with Mo contained in the molybdenum alloy substrate at 1550°C, causing it to melt. Therefore, a joint layer made of Zr cannot ensure heat resistance. Patent Documents 1 and 2 propose a brazing material configuration in which a high-melting-point metal that does not undergo a eutectic reaction with Zr, such as Ta, Nb, or W, is inserted between the Zr and the molybdenum alloy substrate, preventing direct contact between Zr and the molybdenum alloy. In multilayer bonding layers containing elements such as Ta, Nb, and W, layers that melt and solidify at the bonding temperature coexist with layers that do not melt. The material structure differs between the melting and solidifying layers, often resulting in different mechanical properties and thermal expansion coefficients. Specifically, the MoNbTi diffusion phase, NbTi alloy phase, and ZrNb alloy phase described in Patent Document 2 are solid solutions, exhibiting high hardness and excellent mechanical properties due to solid solution strengthening. On the other hand, Nb-rich phases show less solid solution strengthening and reflect the properties of pure Nb, resulting in lower hardness and inferior mechanical properties compared to alloys. Furthermore, the thermal expansion coefficient in alloy phases changes proportionally to the alloy composition. Therefore, if the alloy composition has a gradual concentration gradient along the thickness direction of the bonding layer, the thermal expansion coefficient also changes gradually. Conversely, near the interface between the Nb-rich phase and other alloy phases, the concentration changes abruptly, leading to a large difference in thermal expansion coefficients. Large differences in thermal expansion coefficients make the material prone to brittleness due to repeated thermal fatigue. According to the embodiment, an X-ray tube target and a method for manufacturing the same can be provided, which can ensure heat resistance at 1600°C using a bonding layer composed of only two or more solid solution alloys. Examples of solid solution alloys include MoNbTi alloy, NbTi alloy, and ZrNb alloy. The following describes an embodiment of an X-ray tube target and its manufacturing method. (Target for X-ray tube in the embodiment) The X-ray tube target of this embodiment includes a carbon substrate, a molybdenum alloy substrate, and an alloy layer disposed between the carbon substrate and the molybdenum alloy substrate. The alloy layer contains a solid solution of at least two elements selected from the group consi