Liquid metal bearing with high sealing performance

Abstract

The invention relates to the technical field of metal sliding bearings, and provides a liquid metal sliding bearing with high sealing performance, which comprises a mandrel, a graphite sealing assembly, a flange and a shaft sleeve, and further comprises a ternary gallium-based liquid metal and a silicon carbide ceramic coating, wave-shaped check rings are arranged among the multiple graphite rings at intervals, initial contact loads are provided through the wave-shaped check rings, the graphite rings and the flange are tightly attached, static sealing with excellent performance is formed in the static state, and the fit clearance between the mandrel and the shaft sleeve is filled with ternary gallium-based liquid metal. A silicon carbide ceramic coating is plated at the matching position of the mandrel and the flange, and a silicon carbide ceramic coating is also plated at the matching position of the mandrel and the shaft sleeve. By using the graphite ring, the ternary gallium-based liquid metal and the silicon carbide ceramic coating, the liquid metal has good fluidity, so that the interface can be fully filled, the liquid metal is not easy to volatilize, the lubricating effect is better, the friction factor is low, and the wear resistance is better.

Description

Technical Field

[0001] The invention relates to the technical field of liquid metal sliding bearings, and in particular to a liquid metal bearing with high sealing performance. Background Art

[0002] Liquid metal is usually used as a lubricant between liquid metal bearing components inside CT tubes due to its excellent fluidity, thermal conductivity and thermal stability. Liquid metal as a lubricant has high requirements for the sealing inside the device. If the sealing effect is not good, it will cause liquid metal leakage, bearing operation blockage and wear, and even damage the CT tube, thus affecting its working performance.

[0003] In order to prevent liquid metal from leaking out of the bearing through the slit and affecting the service life of the bearing, the existing liquid metal bearing sealing technology usually uses the PVD method to coat the surface of the parts with a layer of aluminum oxide, chromium oxide, chromium nitride, titanium oxide, titanium nitride, titanium aluminum nitride, etc. between the bearing core and the bearing sleeve parts, so as to improve the wettability of the bearing surface and the lubricating medium; but the process is complicated, the cost is high, and the wear resistance is not significantly improved. Moreover, the PVD film layer is very prone to film shedding or evaporation and thinning during the subsequent high-temperature treatment of the bearing, which brings a relatively large potential risk to the long-term stable operation of the bearing. Alternatively, by coating the sliding surface of the bearing with wear-resistant materials such as tetrahedral amorphous carbon, molybdenum disulfide, diamond and polycrystalline diamond, a lower sliding friction coefficient and higher wear resistance can be obtained, and even the bearing surface after coating is heated, chemically treated and sandblasted to achieve the effect of simultaneously improving the wettability of the bearing lubricant and the friction surface, and improving the wear resistance between the sliding surfaces. However, the heating, chemical treatment and sandblasting process of the bearing surface after coating is complicated. During the application of the process, the wear-resistant coating already on the surface needs to be specially protected, which greatly increases the difficulty of the bearing manufacturing process. In addition, the heating, chemical treatment and sandblasting process will also cause the wear-resistant coating already on the bearing surface to crack or fall off prematurely. In the end, not only will the bearing surface fail to obtain good wetting characteristics, but the wear-resistant coating on the bearing surface may also be damaged, affecting the wear resistance. Therefore, it is necessary to provide a new liquid metal bearing with high sealing performance. Summary of the invention

[0004] The object of the present invention is to provide a liquid metal bearing with high sealing performance, aiming to solve the problems mentioned in the background technology.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a liquid metal bearing with high sealing performance, comprising a core shaft, a graphite sealing assembly, a flange and a sleeve, the liquid metal bearing also comprising a ternary gallium-based liquid metal and a silicon carbide ceramic coating, a plurality of graphite rings are arranged on the inner side of the graphite sealing assembly, and a corrugated retaining ring is arranged between the graphite rings at intervals, and the initial contact load is provided by the corrugated retaining ring, so that the graphite ring and the flange are tightly fitted, and a static seal with excellent performance is formed in a static state; the fit between the core shaft and the sleeve is a clearance fit, and the fitting gap between the core shaft and the sleeve is filled with a ternary gallium-based liquid metal, a layer of silicon carbide ceramic coating is plated at the fitting position of the core shaft and the flange, and a layer of silicon carbide ceramic coating is also plated at the fitting position of the core shaft and the sleeve.

[0006] As a further solution of the present invention, the metal contact parts of the graphite sealing assembly and the flange are connected by fasteners, and the mating surfaces of the flange and the sleeve are connected by fasteners, and the mating surfaces are sealed; the metal mating parts of the graphite sealing assembly and the core shaft are also coated with a layer of silicon carbide ceramic coating.

[0007] As a further solution of the present invention, the sealing treatment step is: preparing a layer of silicon carbide ceramic coating by chemical vapor deposition method.

[0008] As a further solution of the present invention, the ternary gallium-based liquid metal does not wet when used on the silicon carbide ceramic coating.

[0009] As a further solution of the present invention, the graphite sealing assembly, flange and sleeve are all sleeved on the outside of the core shaft, and the flange is located between the graphite sealing assembly and the sleeve.

[0010] As a further solution of the present invention, a radial boss is arranged on the side of the core shaft, and the radial boss is used to limit the axial displacement of the core shaft, and the radial boss is located on the inner side of the flange.

[0011] As a further solution of the present invention, a gap is provided at the fitting position between the inner circle of the graphite ring and the outer circle of the core shaft, and an axial pre-tightening force is applied to the graphite ring through a corrugated retaining ring to achieve a sealing effect.

[0012] In summary, the beneficial effects of the present invention are:

[0013] By setting graphite rings and arranging corrugated retaining rings at intervals between the graphite rings, the corrugated retaining rings provide an initial contact load, so that the graphite rings and the flanges fit closely, and a static seal with excellent performance is formed in a static state. The graphite material has good sealing performance, and has the characteristics of high temperature resistance, corrosion resistance, radiation resistance, and high rebound rate. It can be used in harsh environments such as those requiring extremely low leakage, thermal shock resistance, high pressure, large temperature difference, pressure difference fluctuation, corrosive media, and radiation. By using ternary gallium-based liquid metal and silicon carbide ceramic coating, good fluidity can ensure that the interface is fully filled, and it is not easy to volatilize and has better lubrication effect, and leads to a low friction factor and better wear resistance. In addition, the ternary gallium-based liquid metal does not wet when used on the silicon carbide ceramic coating, and the silicon carbide ceramic coating on the contact surface with the liquid metal can effectively prevent the liquid metal from leaking from the gap, and the sealing is better. And the process of the present invention is relatively simple and the cost is relatively low. In addition, by arranging a radial boss on the side of the mandrel, the axial displacement of the mandrel can be limited, and the liquid metal bearing is more stable when used. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0015] Figure 1 The figure is a cross-sectional schematic diagram of a liquid metal bearing with high sealing performance according to an embodiment of the present invention.

[0016] Figure 2 This is a distribution diagram of a silicon carbide ceramic coating of a liquid metal bearing with high sealing performance according to an embodiment of the present invention.

[0017] Figure numerals: 1-core shaft, 2-graphite sealing assembly, 3-graphite ring, 4-flange, 5-radial boss, 6-sleeve, 7-ternary gallium-based liquid metal, 8-silicon carbide ceramic coating, 9-wave-shaped retaining ring. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0020] See also Figure 1 and Figure 2A liquid metal bearing with high sealing performance provided by an embodiment of the present invention comprises a core shaft 1, a graphite sealing assembly 2, a flange 4 and a sleeve 6, wherein the graphite sealing assembly 2, the flange 4 and the sleeve 6 are all sleeved on the outside of the core shaft 1, and the flange 4 is located between the graphite sealing assembly 2 and the sleeve 6. The liquid metal bearing also comprises a ternary gallium-based liquid metal 7 and a silicon carbide ceramic coating 8. It should be noted that the gallium indium tin alloy is a new type of liquid metal with the advantages of being non-toxic, pollution-free, having a low melting point and high thermal conductivity. It can accelerate heat conduction and improve heat dissipation, and has good fluidity to ensure that the interface is fully filled, has a high boiling point, and is not easy to volatilize. In addition, the lubrication effect of the ternary component gallium indium tin alloy is significantly better than that of the binary component eutectic gallium indium alloy. Therefore, the liquid metal in the embodiment of the present invention is a ternary gallium-based liquid metal 7. The inner side of the graphite sealing assembly 2 is provided with a plurality of graphite rings 3, and a corrugated retaining ring 9 is provided between the graphite rings 3. The corrugated retaining ring 9 provides an initial contact load, so that the graphite ring 3 and the flange 4 fit tightly, and a static seal with excellent performance is formed in a static state. The cooperation between the mandrel 1 and the sleeve 6 is a clearance cooperation, and the cooperation gap between the mandrel 1 and the sleeve 6 is filled with a ternary gallium-based liquid metal 7. A layer of silicon carbide ceramic coating 8 is plated at the cooperation between the mandrel 1 and the flange 4, and a layer of silicon carbide ceramic coating 8 is also plated at the cooperation between the mandrel 1 and the sleeve 6. The silicon carbide ceramic coating 8 is prepared by a chemical vapor deposition method.

[0021] In the embodiment of the present invention, the metal contact parts of the graphite sealing component 2 and the flange 4 are connected by fasteners, and the matching surfaces of the flange 4 and the shaft sleeve 6 are connected by fasteners, and the matching surfaces are sealed; the metal matching parts of the graphite sealing component 2 and the core shaft 1 are also plated with a layer of silicon carbide ceramic coating 8. The sealing treatment step is: preparing a layer of silicon carbide ceramic coating 8 by chemical vapor deposition. The ternary gallium-based liquid metal 7 does not wet when used on the silicon carbide ceramic coating 8, and the silicon carbide ceramic coating 8 on the contact surface with the liquid metal can effectively prevent the liquid metal from leaking from the gap, and the sealing performance is better.

[0022] In the embodiment of the present invention, a radial boss 5 is provided on the side of the core shaft 1, and the radial boss 5 is used to limit the axial displacement of the core shaft 1. The radial boss 5 is located on the inner side of the flange 4, so that the liquid metal bearing is more stable when used.

[0023] In the embodiment of the present invention, a gap is provided at the fitting place between the inner circle of the graphite ring 3 and the outer circle of the core shaft 1, and a reasonable roughness level is selected at the fitting place between the end faces of the graphite ring 3 and the flange 4, and an axial preload is applied to the graphite ring 3 through a corrugated retaining ring to achieve a sealing effect. During operation, the core shaft 1 is fixed, and the shaft sleeve 6 rotates to drive the liquid metal to produce a dynamic pressure effect to achieve lubrication; by providing a silicon carbide ceramic coating 8 on the outer wall of the shaft, the liquid metal can be assisted to flow better on the outer wall of the shaft, so that the lubrication effect is improved, and the overall device is more stable during operation.

[0024] The technical principle of the embodiment of the present invention is as follows: Graphite material has good sealing performance, and has the characteristics of high temperature resistance, corrosion resistance, radiation resistance, and high rebound rate. It can be used in harsh environments requiring extremely low leakage, thermal shock resistance, high pressure, large temperature difference, pressure difference fluctuation, corrosive media, radiation, etc. Graphite, as the element with the highest melting point, can withstand ultra-high temperatures of 3650°C. At high temperatures, its performance is almost unchanged, and it can be used for sealing in ultra-high temperature conditions, while meeting the sealing requirements of a large temperature fluctuation range. And flexible graphite has good chemical inertness, and the activation energy required for its reaction is high. Except for some strongly oxidizing media, it hardly reacts chemically with other chemical media. Flexible graphite has good compression rebound performance, and the interlayer compound generated by its chemical treatment has a loose and porous gas-solid two-phase structure, and its expansion is about two hundred times that of ordinary graphite. Carbon graphite is the friction material with the widest range of applications, and has good combination performance with a variety of metals, non-metals and their coatings. Carbon graphite is the preferred material for sealing devices such as end face seals, circumferential seals, open ring seals and floating ring seals. Graphite packing seal is a way to achieve sealing by using the good compression and rebound characteristics of graphite packing, applying axial load to the material through mechanical structures (such as glands, etc.) to force it to expand radially, contact the extrusion shaft and the packing surface to prevent the leakage of the sealing medium. The sealing performance of the graphite ring depends largely on the transmission of axial force.

[0025] The lubrication performance of gallium-based liquid metal is closely related to the selection of friction pair materials. When steel / ceramic pairs are used, gallium-based liquid metal exhibits good lubrication performance. This is because when bearing steel is paired with SiC ceramics, a Fe-Ga lubricating protective film is formed on the wear surface of the steel block. When gallium-based liquid metal is used to lubricate bearing steel, a layer of FeGa3 friction film is easily formed on the surface of the material. This film is strongly bonded to the steel surface and has good mechanical and tribological properties at room temperature. The melting point of this friction film (824-860°C) is significantly lower than that of steel (about 1300°C), and nanoindentation shows that this friction film is more compliant than steel at both room temperature and high temperature, which helps it act as an easy-to-shear interface layer and leads to a low friction factor, which greatly improves the wear resistance of liquid metal bearings.

[0026] For those skilled in the art, although several embodiments and examples of the present invention are described, these embodiments and examples are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the scope of the subject matter of the invention. These embodiments and their variations are included in the scope and subject matter of the invention, and are included in the invention described in the claims and the scope of their equivalents.

[0027] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A liquid metal bearing with high sealing performance, comprising a core shaft (1), a graphite sealing assembly (2), a flange (4) and a sleeve (6), characterized in that: The liquid metal bearing further comprises a ternary gallium-based liquid metal (7) and a silicon carbide ceramic coating (8); a plurality of graphite rings (3) are arranged on the inner side of the graphite sealing assembly (2); and a wave-shaped retaining ring (9) is arranged at intervals between the plurality of graphite rings (3); the wave-shaped retaining ring (9) provides an initial contact load so that the graphite ring (3) and the flange (4) are tightly fitted, thereby forming a static seal with excellent performance in a static state; the fit between the core shaft (1) and the sleeve (6) is a clearance fit; the fitting clearance between the core shaft (1) and the sleeve (6) is filled with the ternary gallium-based liquid metal (7); a layer of silicon carbide ceramic coating (8) is plated at the fitting position between the core shaft (1) and the flange (4); and a layer of silicon carbide ceramic coating (8) is also plated at the fitting position between the core shaft (1) and the sleeve (6).

2. The liquid metal bearing with high sealing performance according to claim 1, characterized in that: The metal contact parts of the graphite sealing component (2) and the flange (4) are connected by fasteners, and the matching surfaces of the flange (4) and the shaft sleeve (6) are connected by fasteners, and the matching surfaces are sealed; the metal matching parts of the graphite sealing component (2) and the core shaft (1) are also coated with a layer of silicon carbide ceramic coating (8).

3. The liquid metal bearing with high sealing performance according to claim 2, characterized in that: The sealing treatment step is: preparing a layer of silicon carbide ceramic coating (8) by chemical vapor deposition method.

4. The liquid metal bearing with high sealing performance according to claim 2, characterized in that: The ternary gallium-based liquid metal (7) does not wet when used on the silicon carbide ceramic coating (8).

5. The liquid metal bearing with high sealing performance according to claim 1, characterized in that: The graphite sealing component (2), flange (4) and shaft sleeve (6) are all sleeved on the outside of the core shaft (1), and the flange (4) is located between the graphite sealing component (2) and the shaft sleeve (6).

6. The liquid metal bearing with high sealing performance according to claim 1, characterized in that: A radial boss (5) is arranged on the side of the core shaft (1), and the radial boss (5) is used to limit the axial displacement of the core shaft (1). The radial boss (5) is located on the inner side of the flange (4).

7. The liquid metal bearing with high sealing performance according to claim 1, characterized in that: A gap is provided at the fitting position between the inner circle of the graphite ring (3) and the outer circle of the core shaft (1), and an axial pre-tightening force is applied to the graphite ring (3) through the corrugated retaining ring to achieve a sealing effect.

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