Abstract
A rotor component for a rotary x-ray anode has a carrier body and a spray coating. The carrier body is made from one of the following materials a refractory metal, a refractory metal-based alloy, iron, an iron-based alloy or combinations thereof, and the spray coating contains copper or a copper-based alloy. The carrier body is materially bonded to the spray coating at least in sections at a connecting surface. The rotor component is characterized in that the microstructure of the rotor component has no transition region at the connecting surface between the carrier body and the spray coating.
Claims
1-15. (canceled)
16. A rotor component for an X-ray rotating anode, the rotor component comprising: a carrier body formed from a material selected from the group consisting of: a refractory metal, a refractory metal-based alloy, Fe, an Fe-based alloy and combinations thereof; and a spray coating containing Cu or a Cu-based alloy, wherein said carrier body is material-bonded to said spray coating at least in sections at a connecting surface, a microstructure of the rotor component having no transition zone at said connecting surface between said carrier body and said spray coating.
17. The rotor component according to claim 16, wherein said spray coating is a cold gas spray coating.
18. The rotor component according to claim 17, wherein said cold gas spray coating includes cold-formed Cu particles or Cu-based alloy particles at least in certain areas, which are at least partially stretched parallel to a surface of said carrier body and have a stretching ratio of >1.
19. The rotor component according to claim 18, wherein said cold gas spray coating after annealing has a recrystallized microstructure of said cold-formed Cu particles or said Cu-based alloy particles with an average grain size of 150 m.
20. The rotor component according to claim 16, wherein said spray coating is a Cu spray coating or a Cu-based alloy spray coating which has 1000 g/g oxygen, 500 g/g iron and 200 g/g nitrogen.
21. The rotor component according to claim 16, wherein said spray coating has a layer thickness of between 25 m and 5 cm.
22. The rotor component according to claim 16, wherein said spray coating has an electrical conductivity of 26 MS/m.
23. The rotor component according to claim 16, wherein said spray coating has a density of 90% of a theoretical density of the Cu or of the Cu-based alloy.
24. A method of manufacturing a rotor component for an X-ray rotating anode, the rotor component having a carrier body and a spray coating, which comprises the following steps of: providing the carrier body formed from a material selected from the group consisting of: a refractory metal, a refractory metal-based alloy, Fe, an Fe-based alloy and combinations thereof; and coating the carrier body by means of the spray coating having a powdery coating material, so that the rotor component has an at least partially material-bonded connection at a connecting surface between the carrier body and the spray coating being produced, wherein the spray coating contains Cu or a Cu-based alloy, and wherein a microstructure of the rotor component has no transition zone at the connecting surface between the carrier body and the spray coating.
25. The method according to claim 24, which further comprises applying the spray coating by means of cold gas spraying.
26. The method according to claim 25, which further comprises performing the cold gas spraying at a pressure of 10 to 100 bar and at a gas temperature of room temperature to 1000 C.
27. The method according to claim 24, which further comprises annealing the rotor component in a vacuum or in a protective gas atmosphere after the coating step.
28. The method according to claim 27, which further comprises performing the annealing of the rotor component at 400 to 750 C. for up to 5 hours after the coating step.
29. The method according to claim 24, which further comprises surface-treating the carrier body before performing the coating step.
30. The method according to claim 24, wherein the powdery coating material containing the Cu or the Cu-based alloy has a powder particle size of between 5 and 150 m.
Description
[0043] Further advantages and usefulness of the invention are shown in the following description of embodiments with reference to the attached figures.
[0044] The figures show:
[0045] FIG. 1: Schematic representation of an overview image of an X-ray tube with an X-ray rotating anode in longitudinal section according to the state of the art;
[0046] FIG. 2: Scanning electron microscope image of the transition zone between the steel body and copper in sample no. 1 (100 magnification) according to the state of the art;
[0047] FIG. 3: Scanning electron microscope image of the transition zone between the steel body and copper in sample no. 2 according to the invention (100 magnification);
[0048] FIG. 4a: Scanning electron microscope image of the transition zone between the steel body and copper in sample no. 2 according to the invention (500 magnification);
[0049] FIG. 4b: Scanning electron microscope image of the transition zone between the steel body and copper in sample no. 1 (500 magnification) according to the state of the art; 6
[0050] FIG. 4c: Line scan of the transition zone between the steel body and copper based on FIG. 4b;
[0051] FIG. 5: Scanning electron microscope image of the copper coating on sample no. 2 according to the invention (100 magnification) before the annealing step;
[0052] FIG. 6: Light microscope image of the copper coating on sample no. 2 according to the invention (200 magnification) before the annealing step after etching;
[0053] FIG. 7: Light microscope image of the copper coating on sample no. 2 according to the invention (200 magnification) after the annealing step and after etching;
[0054] FIG. 8: Light microscope image of the copper coating on sample no. 2 according to the invention after annealing and etching (50 magnification);
[0055] FIG. 9: Light microscope image of the copper coating on sample no. 1 (50 magnification) according to the state of the art after etching;
[0056] FIG. 1 shows a longitudinal section of an X-ray tube with a rotor and an X-ray rotating anode as known in the prior art. An X-ray tube usually consists of a glass bulb (5) with a vacuum interior (4). The glass bulb contains a cathode (3) with a heating coil (6) which emits electrons (7). Opposite the cathode (3) is the X-ray rotating anode (2), which comprises an anode disc (11) that is connected to the rotor (1) of an electric motor by a shaft (12). A stator (9, 10) is arranged outside the glass bulb (5) to drive the rotor. When connected to electricity, the stator (9, 10) generates a magnetic field rotating around the glass bulb (5), which exerts a torque on the rotor (1) and thus causes the X-ray rotating anode (2) to rotate. The rotor (1) and the X-ray rotating anode (2) are located in a high vacuum (4) in a glass flask (5). The electrons (7) emitted by the cathode (3) are accelerated towards the anode disc and, when they hit the anode disc, generate X-rays (8) by deceleration, which leave the X-ray tube through a radiation window in the glass bulb.
EXAMPLES
[0057] Sample no. 1 was produced using the back-casting process in accordance with the state of the art. A steel tube with a composition of 0.08-0.15 wt. % C, 1.00 wt. % Si, 1.50 wt. % Mn, 0.040 wt. % P, 0.030 wt. % S, 11.5 to 13.5 wt. % Cr, balance Fe and usual impurities with a length of 103 mm, an outer diameter of 62 mm and an inner diameter of 44 mm was provided for this purpose. This steel tube was inserted into a graphite mould and then back-cast with a copper melt (with at least 99.95 wt. % Cu, the remainder being the usual impurities, max. 0.05 wt. % in total). The steel tube was then turned so that the copper coating (on the outer sheath surface of the steel tube) had a thickness of 2 mm.
[0058] For sample no. 2 according to the invention, Cu powder was provided with 99.95 atomic 14% Cu and 28 g/g C, <10 g/g Fe, 4 g/g H, <5 g/g N and 201 g/g O. The average particle size d.sub.50 was 26.53 m. A steel component with a composition of 0.20-0.22 wt. % C, 0.55 wt. % Si, 1.60 wt. % Mn, 0.025 wt. % P, 0.025 wt. % S, 0.55 wt. % Cu, remaining Fe and usual impurities with a diameter of 25 mm and a height of 7 mm was provided and the surface was pre-cleaned. The steel component was then coated with the Cu powder using the cold gas spraying process. The following cold gas spraying process parameters were used: Pressure 32 bar, gas temperature 400 C., process gas N.sub.2. After coating, the sample was annealed at 550 C. for 1 h in a high vacuum. The coating was turned down to 1 mm, so that the total thickness of the sample was 8 mm.
[0059] The electrical conductivity of the coating was then measured in accordance with DIN EN 16813 (2017). Sample no. 1 had a conductivity of 24 MS/m. The electrical conductivity of sample no. 2 was 56 MS/m. In pure copper, the electrical conductivity is 58 MS/m (according to IACS). Consequently, the cold gas spray-coated steel component has almost twice the conductivity of the steel component produced by back-casting. In addition, the sample according to the invention has approximately the electrical conductivity of pure copper.
[0060] In addition, the adhesion strength of the copper spray coating to the steel component of sample no. 2 was tested. These tests were carried out in accordance with ASTM C633-13 (2013). This resulted in good coating adhesion values with an adhesive strength>16 MPa.
[0061] To analyse the interface and the applied coating, polished sections were created whose image surface is at a 90 angle to the coating plane and thus depict the two base materials and their interface. These polished sections were examined under a scanning electron microscope at 100 and 500 magnification and images were taken. On the other hand, light microscope images of the polished sections were also taken, in which the sections were etched beforehand to show the grain structure of the spray coating.
[0062] FIG. 2 shows the transition from steel to copper coating in a scanning electron micrograph in cross section of sample no. 1 of the example (Cu back casting on steel) according to the state of the art with a magnification of 100. FIG. 2 shows the steel body (A, dark area) in the lower half of the image and the copper coating (C, light area) in the upper half of the image. The copper coating is bonded to the steel over the entire surface via a transition zone (B) and the loosening of the steel surface due to the back-casting with copper is clearly visible. The transition zone (B) shows an approximate thickness of approx. 50 m. It can be clearly seen that the copper coating has penetrated the surface of the steel and that there are also steel components in the copper coating, i.e. both materials diffuse into each other and there are no homogeneous material properties in the transition zone.
[0063] FIG. 3 shows the transition from steel to copper coating in a scanning electron micrograph in cross-section of sample no. 2 of the example according to the invention (cold gas spray coating on steel) at a magnification of 100. FIG. 3 shows the steel body (A, dark area) in the lower half of the image and the copper coating (C, light area) in the upper half of the image. The bonding of the copper coating to the steel is complete over the entire surface and no mixing of the materials can be recognised, i.e. there is no transition zone.
[0064] FIG. 4a is an enlarged image of FIG. 3 and also shows the transition from steel to the copper coating in a scanning electron microscope image in cross-section of sample no. 2 of the example according to the invention (cold gas spray coating on steel) at a magnification of 500. FIG. 4a shows the steel body (A, dark area) in the lower half of the image and the copper coating (C, light area) in the upper half of the image. The surface of the steel is clearly recognisable and exhibits unevenness. These irregularities can be caused either by the surface treatment of the steel before cold spraying or by the impact of the copper on the steel surface. In the figure shown, the surface unevenness amounts to a maximum of 10 m. However, it can be clearly seen that the steel surface has not been dissolved and no mixing of the materials has taken place. There is a clear demarcation between the steel body (A) and the copper coating (C).
[0065] FIG. 4b is an enlarged image of FIG. 2 and also shows the transition from steel to copper coating in a scanning electron microscope image in cross-section of sample no. 1 of the example (Cu back casting on steel) according to the state of the art with a magnification of 500. FIG. 4b shows the steel body (A, dark area) in the right half of the image and the copper coating (C, light area) in the left half of the image. The transition zone (B) is clearly recognisable. The copper has partially penetrated deep into the steel surface. The steel surface shows clear signs of melting, meaning that there is steel in the copper layer.
[0066] FIG. 4c shows a line scan of the transition zone from copper to steel based on FIG. 4b. For this purpose, the element concentrations of the elements chromium, iron and copper are measured along a line starting from the copper coating (C, light area) in the direction of the steel body (A, dark area). The peak intensities after excitation with the Cu K(alpha) line used for evaluation are corrected iteratively in relation to the atomic number, the absorption and the fluorescence in this method and thus provide the possibility of a standard-free quantitative calculation of the element composition (in atomic %). It can be clearly seen that in the area of the transition zone (B), high quantities of iron are present in the copper coating and high quantities of copper have penetrated deep into the surface of the steel body. The high Cu content in the area of the Cu layer (C) before the transition zone (B) and the high Fe content in the steel body (A) after the transition zone (B) are clearly recognisable. In the area of the Cu layer (C), higher Fe contents are also recognisable (especially in comparison to the Cu contents in the steel body (A)). This shows that Fe can also penetrate beyond the transition zone into the Cu coating (C). It can also be seen that the steel body also contains a proportion of chromium.
[0067] FIG. 5 shows a copper coating (C) in a scanning electron micrograph in cross-section of sample no. 2 of the example according to the invention (cold spray coating on steel) before the annealing step with a magnification of 100. The copper coating shows a homogeneous layer with a density of 97% (97-98.66%) of the theoretical density of copper. Individual layers are not recognisable.
[0068] FIG. 6 shows the copper coating (C) in an optical microscope image in cross-section of sample no. 2 of the example according to the invention (cold gas spray coating on steel) before the annealing step at a magnification of 200. The grain boundaries were emphasised by etching the Cu particles so that the microstructure is clearly visible. The elongated shape of the Cu particles and the many layers can be recognised. This coating is clearly different from a Cu coating using back-casting (see FIG. 9).
[0069] FIG. 7 shows the copper coating (C) in an optical microscope image in cross-section of sample no. 2 of the example according to the invention (cold gas spray coating on steel) after the annealing step with a magnification of 200. The grain boundaries were emphasised by etching the Cu particles so that the microstructure is clearly visible. The fine-grained and equiaxed microstructure of the coating can be recognised.
[0070] FIG. 8 shows a copper coating (C) in an optical microscope image in cross-section of sample no. 2 of the example according to the invention (cold gas spray coating on steel) after the annealing step with a magnification of 50. This low magnification was chosen in order to have a direct comparison with the grain size in the back-casting process. After etching the Cu particles, a fine-grained and uniform microstructure of the copper coating (C) can be recognised. The steel body (A, dark area) can also be recognised.
[0071] FIG. 9 shows a copper coating (C) in an optical microscope image in cross-section of sample no. 1 of the example (Cu back-casting on steel) according to the state of the art with a magnification of 50. After etching the copper particles, it can be clearly seen that a large-grained structure of the copper coating is formed during back-casting.
