Plain bearing device for molten salt, pump, and method for operating the pump

Abstract

To provide a plain bearing device for molten salt that is superior in wear resistance and corrosion resistance in a molten salt environment, a pump with the plain bearing device for molten salt, and a method for operating the pump.SOLUTION: A plain bearing device for molten salt comprises a plain bearing and a sleeve which slides on the plain bearing, wherein a slide surface of the plain bearing and a slide surface of the sleeve are 330 or larger in Vickers hardness, and the slide surface of the plain bearing and the slide surface of the sleeve are formed of at least one kind selected from a group of a nickel-based alloy, a cobalt-based alloy, a nickel-based intermetallic compound, Al2O3, and ZrO2-Y2O3 composite ceramic including 97 mol% of ZrO2 and 3 mol% of Y2O3.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a plain bearing device for molten salt, a pump equipped with the plain bearing device for molten salt, and a method for operating the pump. [Background technology]

[0002] Solar thermal power generation is used alongside wind power generation and photovoltaic power generation as a means of generating renewable energy. A solar thermal power generation system comprises a heat collection facility that uses mirrors to reflect and concentrate sunlight and convert it into thermal energy, a heat storage facility that stores the collected thermal energy, and a power generation facility that uses the collected heat to generate steam to turn a steam turbine and generate electricity. A solar thermal power generation system can also generate electricity at night if some of the daytime thermal energy is stored in the heat storage facility.

[0003] Solar thermal power generation systems use a heat transfer medium for heat transfer and heat storage. Using molten salt as the heat transfer medium enables operation at high temperatures, which has the advantage of supplying high-temperature steam and increasing power generation efficiency.

[0004] In solar thermal power generation systems that use molten salt as a heat transfer medium, pumps equipped with plain bearing devices are used to circulate the molten salt within the system. In the plain bearing devices of such pumps, the plain bearing and a sleeve attached to the main shaft slide in contact with the high-temperature molten salt, and therefore the plain bearing and the sleeve are required to have wear resistance when operating in contact with the high-temperature molten salt. Furthermore, molten salts are generally highly corrosive, for example, nitrate-based molten salts are highly corrosive due to the high oxidizing power of nitric acid. Therefore, the sliding bearings and sleeves of pumps used in solar thermal power generation systems are also required to be resistant to corrosion by high-temperature molten salts.

[0005] Non-Patent Document 1 discloses a solar thermal power generation system that circulates molten salt using a pump equipped with a plain bearing device, and investigates the optimal combination of the plain bearing material in the plain bearing device and the material of the sleeve attached to the main shaft. Non-Patent Document 1 lists combinations of the plain bearing material and the sleeve material that offer excellent wear resistance and corrosion resistance, such as a combination of Ni-Resist Type I (austenitic cast iron) (upper bearing) and ductile cast iron (lower bearing) with Stellite® 6B (cobalt-based alloy), a combination of Ni-Resist Type I (austenitic cast iron) with Tribaloy® T-900 (cobalt-based alloy), and a combination of gray cast iron (Gray Cast Iron Grade 40) with Stellite® 6B (cobalt-based alloy). [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] DL Barth et al., “Development of a High-Temperature, Long-Shafted, Molten-Salt Pump for Power Tower Applications”, Proceedings of Solar Forum 2001 Summary of the Invention [Problem to be solved by the invention]

[0007] In the solar thermal power generation system of Non-Patent Document 1, the temperature of the molten salt is set to a maximum of 565°C during operation. On the other hand, in order to further increase the power generation efficiency, the temperature of the molten salt may be increased to a higher temperature (for example, 600°C). In this case, the viscosity of the molten salt decreases, making it difficult for a liquid film to form between the sliding surface of the plain bearing and the sliding surface of the sleeve, creating a more severe environment in terms of wear. As will be shown in the comparative example described later, such a higher temperature such as 600°C It was found that when operating at high temperatures, the combination of the sliding bearing material and sleeve material selected in Non-Patent Document 1 may not be sufficient in terms of wear resistance and corrosion resistance.

[0008] As described above, there is a demand for a sliding bearing device for use in a molten salt environment that exhibits excellent wear resistance and corrosion resistance in a molten salt environment.

[0009] An object of the present invention is to provide a sliding bearing device for use with molten salt that has excellent wear resistance and corrosion resistance in a molten salt environment, a pump equipped with the sliding bearing device for use with molten salt, and a method for operating the pump. [Means for solving the problem]

[0010] As a result of intensive research into solving the above problems, the inventors discovered that the above problems could be solved by forming the sliding surfaces of the sliding bearing and the sleeve from a specific material, and thus completed the present invention. Specific aspects of the present invention are as follows.

[0011] [1] A sliding bearing device for molten salt, Plain bearings, and A sleeve that slides with the plain bearing Equipped with The sliding surface of the sliding bearing and the sliding surface of the sleeve have a Vickers hardness of 330 or more, The sliding bearing device for molten salt, wherein the sliding surface of the sliding bearing and the sliding surface of the sleeve are formed from at least one material selected from the group consisting of a nickel-based alloy, a cobalt-based alloy, a nickel-based intermetallic compound, Al2O3, and a ZrO2-Y2O3 composite ceramic containing 97 mol% ZrO2 and 3 mol% Y2O3. [2] The sliding bearing device for molten salt according to [1], wherein the nickel-based alloy consists, in mass%, of 0.4 to 1.1% C, 0 to 1% Co, 12 to 26% Cr, 0 to 4% Cu, 0 to 4% Mo, 0 to 5% Fe, 2.5 to 4.5% B, 2.0 to 5.0% Si, and the remainder being Ni and unavoidable impurities. [3] The sliding bearing device for molten salt according to [1], wherein the nickel-based alloy consists, by mass%, of C: 0-0.08%, Co: 0-1.5%, Cr: 16%, Mo: 32%, Fe: 0-1.5%, Si: 3.4%, and the remainder being Ni and unavoidable impurities. [4] A sliding bearing device for use with molten salt according to any one of [1] to [3], wherein the cobalt-based alloy consists, in mass%, of 0.9 to 1.7% C, 0 to 3% Ni, 26 to 32% Cr, 3 to 9.5% W, 0 to 1% Mo, 0 to 1% Mn, 0 to 3% Fe, 0 to 2% Si, and the remainder being Co and unavoidable impurities. [5] A sliding bearing device for use with molten salt according to any one of [1] to [3], wherein the cobalt-based alloy consists, in mass%, of C: 0.15 to 0.45%, Ni: 1.5 to 4%, Cr: 25 to 30%, W: 0 to 0.5%, Mo: 4.5 to 7%, Mn: 0 to 1.5%, Fe: 0 to 3%, Si: 0 to 1.5%, and the remainder being Co and unavoidable impurities. [6] A sliding bearing device for use with molten salt according to any one of [1] to [5], wherein the nickel-based intermetallic compound consists of Al: more than 5 atomic % and 13 atomic % or less, V: 9.5 atomic % or more and less than 17.5 atomic %, Ti: 5 atomic % or less, B: 1000 weight ppm or less, and the remainder being Ni and unavoidable impurities. [7] A sliding bearing device for use with molten salt according to any one of [1] to [5], wherein the nickel-based intermetallic compound consists of 1 to 10.5 atomic % of Si, 5 to 16 atomic % of Ti, 0 to 10 atomic % of Nb, 0 to 1000 ppm by weight of B, and the remainder being Ni and unavoidable impurities. [8] The nickel-based intermetallic compound contains Si: 10.0 atomic % or more and 12.0 atomic % or less, Ti: 1.5 atomic % or more but less than 7.5 atomic %, Ta: more than 2.0 atomic % and 8.0 atomic % or less, and The sliding bearing device for use with molten salt according to any one of [1] to [5], wherein the intermetallic compound contains 25 to 500 ppm by weight of B relative to the weight of the intermetallic compound having a composition consisting of a total of 100 atomic % of Ni, and the remainder being Ni and unavoidable impurities. [9] A sliding bearing device for molten salt described in any one of [1] to [8], wherein the sliding surface of the sliding bearing and the sliding surface of the sleeve are formed from a coating material, and the thickness of the coating material is 0.2 mm or more.

[10] The sliding bearing device for molten salt according to [9], wherein the thickness of the coating material is 1 mm or more.

[11] The sliding bearing device for use with molten salt according to any one of [1] to

[10] , wherein the molten salt comprises a eutectic salt of sodium nitrate, sodium nitrite, and potassium nitrate.

[12] The sliding bearing device for use with molten salt according to any one of [1] to

[10] , wherein the molten salt is a carbonate mixture containing potassium carbonate, sodium carbonate, and lithium carbonate.

[13] A pump equipped with the sliding bearing device according to any one of [1] to

[12] .

[14] A method for operating the pump according to

[13] , comprising: the pump including a rotating shaft about which the sleeve is mounted; a step of rotating the rotating shaft by sliding the plain bearing and the sleeve, and taking in molten salt into the pump and then discharging it to the outside of the pump.

[15] The method for operating a pump according to

[14] , wherein the temperature of the molten salt is 300°C or higher and 600°C or lower. [Effects of the Invention]

[0012] The sliding bearing device for use with molten salt of the present invention and a pump equipped with the sliding bearing device for use with molten salt have excellent wear resistance and corrosion resistance in a molten salt environment. [Brief explanation of the drawings]

[0013] [Figure 1]FIG. 1 is a cross-sectional view showing the entire pump equipped with a sliding bearing device. [Figure 2] FIG. 2 is an enlarged view of a sliding bearing device applied to the pump shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] In the present application, a numerical range expressed as "A to B" (A and B are numerical values) includes the endpoint values ​​A and B.

[0015] The sliding bearing device, pump, and method of operating the pump according to the present invention will be described below.

[0016] 1. Slide bearing devices, pumps FIG. 1 is a cross-sectional view showing the entire pump equipped with a plain bearing device. As shown in FIG. 1, the pump has a casing 1. A main shaft (rotating shaft) 2 is arranged in approximately the radial center of the pump casing 1. A sleeve 3 is attached around a portion of the main shaft 2 (two locations in FIG. 1), and a plain bearing 4 is provided on the outer periphery of the sleeve 3. An impeller 5 is connected to one end of the main shaft 2 for drawing a heat transfer medium (molten salt) into the pump. The other end of the main shaft 2 extends outside the pump and is connected to a driving machine such as an engine or motor (not shown) that rotates the impeller 5. The rotation of the driving machine is transmitted to the main shaft 2, which rotates the impeller 5. The rotation of the impeller 5 draws in the molten salt.

[0017] Fig. 2 is an enlarged view of the plain bearing device shown in Fig. 1 (the plain bearing device on the upper side in Fig. 1). As shown in Fig. 2, the plain bearing device has a sleeve 3 attached to the outer periphery of a main shaft 2 via a sleeve housing 6. A hollow cylindrical plain bearing 4 is provided on the outer periphery of the sleeve 3. The outer periphery of the sleeve 3 and the inner periphery of the plain bearing 4 face each other with a very narrow clearance between them to form a sliding surface (sliding surface) 7. The outer periphery of the plain bearing 4 is The bearing is fixed to a support member 9 connected to the casing 1 of the pump (see FIG. 1) via a plain bearing housing 8.

[0018] The sliding bearing device for molten salt of this embodiment can have, for example, the same structure as the sliding bearing device shown in Fig. 2. That is, the sliding bearing device according to this embodiment can have a main shaft 2 and a sleeve 3, which are rotating bodies, and a sliding bearing 4, which is a fixed body.

[0019] The sliding bearing for molten salt according to this embodiment Device The present invention comprises a sliding bearing and a sleeve that slides on the sliding bearing, wherein the sliding surfaces of the sliding bearing and the sliding surfaces of the sleeve have a Vickers hardness of 330 or more, and the sliding surfaces of the sliding bearing and the sliding surfaces of the sleeve are formed from at least one material selected from the group consisting of a nickel-based alloy, a cobalt-based alloy, a nickel-based intermetallic compound, Al2O3, and a ZrO2-Y2O3 composite ceramic containing 97 mol% ZrO2 and 3 mol% Y2O3.

[0020] For example, if a sliding bearing device is operated at a high temperature of approximately 600°C using nitrate-based molten salt, the viscosity of nitrate-based molten salt at 600°C is approximately 2 mPa·s, making it difficult for a liquid film of molten salt to form between the sliding surface of the sliding bearing and the sliding surface of the sleeve, thereby making it difficult to provide lubrication. Therefore, the sliding bearing and sleeve are exposed to a harsh environment in terms of wear resistance. From the perspective of providing wear resistance, it is preferable to form the sliding surfaces of the sliding bearing and the sliding surfaces of the sleeve using high-hardness materials. However, when using nitrate-based molten salt, the oxidizing power of nitric acid makes the molten salt highly corrosive. Therefore, it is desirable to form the sliding surface using a high-hardness corrosion-resistant material to achieve both wear resistance and corrosion resistance in a sliding bearing device. However, a high-hardness corrosion-resistant material suitable for forming the sliding surface has not yet been discovered. The sliding bearing device of this embodiment has excellent corrosion resistance and wear resistance in a molten salt environment by using such materials to form the sliding surfaces of both the sliding bearing and the sleeve.

[0021] The molten salt used is not particularly limited, but may be a nitrate, a nitrite, a carbonate, or a mixture of two or more of these. As the nitrate, sodium nitrate, potassium nitrate, lithium nitrate, or a mixture of two or more of these may be used. As the nitrite, sodium nitrite may be used. As the carbonate, potassium carbonate, sodium carbonate, lithium carbonate, or a mixture of two or more of these may be used. As the molten salt, from the viewpoints of high stability, high safety, and cost reduction, a molten salt consisting of a eutectic salt of sodium nitrate, sodium nitrite, and potassium nitrate, a mixture of sodium nitrate and potassium nitrate, a carbonate mixture containing potassium carbonate, sodium carbonate, and lithium carbonate, etc. As the mixture of sodium nitrate and potassium nitrate, a molten salt containing (or consisting of) 60 wt % sodium nitrate and 40 wt % potassium nitrate can be used.

[0022] The temperature of the molten salt when using the sliding bearing device for molten salt of this embodiment is not particularly limited as long as it is at or above the melting point of the molten salt, but the lower limit can be 300°C or higher, 400°C or higher, or 500°C or higher, and the upper limit can be 550°C or lower or 600°C or lower. These lower and upper limits can be combined as desired. Because the sliding bearing device for molten salt of this embodiment has excellent wear resistance and corrosion resistance, the temperature of the molten salt can be set to a higher temperature than conventional (for example, 600°C), which can improve power generation efficiency when used in solar thermal power generation.

[0023] In this embodiment, the Vickers hardness of the sliding surface of the sliding bearing and the sliding surface of the sleeve is 330 or more, and can be 330 to 1500, or 500 to 1500. The Vickers hardness can be measured based on the JIS Z2244 method.

[0024] (nickel-based alloy) The nickel-based alloy used for the sliding surface of the sliding bearing and the sliding surface of the sleeve is not particularly limited, but may be an alloy consisting of, in mass%, C: 0.4 to 1.1%, Co: 0 to 1%, Cr: 12 to 26%, Cu: 0 to 4%, Mo: 0 to 4%, Fe: 0 to 5%, B: 2.5 to 4.5%, Si: 2.0 to 5.0%, and the balance being Ni and unavoidable impurities (hereinafter referred to as "nickel-based alloy (1)"); in mass%, C: 0 to 0.08%, Co: 0 to 1.5%, An alloy consisting of 16% Cr, 32% Mo, 0-1.5% Fe, 3.4% Si, and the balance being Ni and unavoidable impurities (hereinafter referred to as "nickel-based alloy (2)"), an alloy consisting of, by mass, 0-0.08% C, 0-1% Co, 0-10% Cr, 0-4% Cu, 0-4% Fe, 0.5-2.5% B, 1.5-4% Si, and the balance being Ni and unavoidable impurities, or a combination of two or more of these can be used. Among these, from the viewpoint of corrosion resistance, the use of the above-mentioned nickel-based alloy (1) or nickel-based alloy (2) is preferred. Examples of the nickel-based alloy (1) include SFNi 4 and SFNi 5, which are used in the examples described below, and examples of the nickel-based alloy (2) include Tribaloy (registered trademark) T-700 (manufactured by Deloro Stellite).

[0025] (Cobalt-based alloy) The cobalt-based alloy used for the sliding surface of the sliding bearing and the sliding surface of the sleeve is not particularly limited, but examples thereof include an alloy consisting of, by mass%, C: 0.9 to 1.7%, Ni: 0 to 3%, Cr: 26 to 32%, W: 3 to 9.5%, Mo: 0 to 1%, Mn: 0 to 1%, Fe: 0 to 3%, Si: 0 to 2%, and the balance being Co and unavoidable impurities (hereinafter referred to as "cobalt-based alloy (1)"); an alloy consisting of, by mass%, C: 0.15 to 0.45%, Ni: 1.5 to 4%, Cr: 25 to 30%, W: 0 to 0.5%, Mo: 4.5 to 7%, Mn: 0 to 1.5%, Fe: 0 to 3%, Si: 0 to 1.5%, and the balance being Co and unavoidable impurities (hereinafter referred to as "cobalt-based alloy (2)"); and an alloy consisting of, by mass%, C: 0.9 to 1.4%. , an alloy consisting of, by mass%, Ni: 0-3%, Cr: 28-32%, W: 3.5-5.5%, Mo: 0-1.5%, Mn: 0-2%, Fe: 0-3%, Si: 0-2%, and the balance being Co and unavoidable impurities (hereinafter referred to as "cobalt-based alloy (3)"); an alloy consisting of, by mass%, C: 0-0.08%, Ni: 0-16%, Cr: 8.5-18%, Mo: 23-25.5%, Si: 0.4-3.4%, and the balance being Co and unavoidable impurities; an alloy consisting, by mass%, C: 0-1%, Ni: 0-30%, Cr: 10-24%, W: 0-15.5%, Fe: 0-5%, B: 1.5-4%, Si: 2-4%, and the balance being Co and unavoidable impurities; or a combination of two or more of these. Among these, from the viewpoint of corrosion resistance, it is preferable to use the cobalt-based alloy 1 or the cobalt-based alloy 2. Examples of the cobalt-based alloy 1 include Stellite (registered trademark) 6 and Stellite (registered trademark) 12 (both manufactured by Deloro Stellite Co., Ltd.), examples of the cobalt-based alloy 2 include Stellite (registered trademark) 21 (manufactured by Deloro Stellite Co., Ltd.), and examples of the cobalt-based alloy 3 include Stellite (registered trademark) 6B (manufactured by Deloro Stellite Co., Ltd.).

[0026] (nickel-based intermetallic compound) The nickel-based intermetallic compound used for the sliding surface of the sliding bearing and the sliding surface of the sleeve is not particularly limited, but may include a compound consisting of Al: more than 5 atomic % and 13 atomic % or less, V: 9.5 atomic % or more and less than 17.5 atomic %, Ti: 5 atomic % or less, B: 1000 weight ppm or less, and the balance being Ni and unavoidable impurities (hereinafter referred to as "nickel-based intermetallic compound (1)"); a compound consisting of Si: 1 to 10.5 atomic %, Ti: 5 to 16 atomic %, Nb: 0 to 10 atomic %, B: 0 to 1000 weight ppm, and the balance being Ni and unavoidable impurities (hereinafter referred to as "nickel-based intermetallic compound (2)"); Si: 10.0 atomic % or more and 12.0 atomic % or less, Ti: 1.5 atomic % or more and less than 7.5 atomic %, Ta: more than 2.0 atomic % and 8.0 atomic % or less; An intermetallic compound containing 25 to 500 ppm by weight of B relative to the weight of the intermetallic compound having a composition of 100 atomic % with the balance being Ni and unavoidable impurities (hereinafter referred to as "nickel-based intermetallic compound (3)"), γ'-NiAl3, or a combination of two or more of these can be used. Among these, from the viewpoint of improving toughness, it is preferable to use the above-mentioned nickel-based intermetallic compound (1), nickel-based intermetallic compound (2), or nickel-based intermetallic compound (3).

[0027] <Nickel-based intermetallic compounds (1)> The Al content in the nickel-based intermetallic compound (1) is preferably, in atomic percent, more than 6%, more than 7%, or more than 8%, and is preferably 11% or less, 10% or less, or 9% or less. The V content in the nickel-based intermetallic compound (1) is preferably 10.5% or more, 11.5% or more, or 12.5% ​​or more, in atomic percent, and is preferably less than 16.5%, less than 15.5%, or less than 14.5%. The nickel-based intermetallic compound (1) may or may not contain Ti. The Ti content in the nickel-based intermetallic compound (1) is preferably 4.5% or less, 4% or less, 3.5% or less, or 3% or less, in atomic percent, and is preferably 0.5% or more, 1% or more, 1.5% or more, or 2% or more. The nickel-based intermetallic compound (1) may or may not contain B. The B content in the nickel-based intermetallic compound (1) is preferably 900 weight ppm or less, 800 weight ppm or less, 700 weight ppm or less, or 600 weight ppm or less, and is preferably 50 weight ppm or more, 100 weight ppm or more, 200 weight ppm or more, 300 weight ppm or more, or 400 weight ppm or more. Examples of the nickel-based intermetallic compound (1) include Ni3(Al,V) used in the examples described later and the intermetallic compounds described in JP-A-2006-299403.

[0028] <Nickel-based intermetallic compounds (2)> The Si content in the nickel-based intermetallic compound (2) is preferably 3.1 to 9.2 atomic %, more preferably 5.1 to 9.2 atomic %, and even more preferably 7.2 to 9.2 atomic %. The Ti content in the nickel-based intermetallic compound (2) is preferably 5.1 to 11.2 atomic %, more preferably 5.1 to 9.2 atomic %, and even more preferably 7.2 to 9.2 atomic %. The Nb content in the nickel-based intermetallic compound (2) is preferably 0.5 to 10 atomic %, more preferably 3.1 to 9.2 atomic %, and even more preferably 3.1 to 5.1 atomic %. The nickel-based intermetallic compound (2) preferably contains Nb, but may not contain Nb. The content of B in the nickel-based intermetallic compound (2) is preferably 10 to 1000 ppm by weight, more preferably 10 to 800 ppm by weight, even more preferably 25 to 600 ppm by weight, and even more preferably 50 to 500 ppm by weight. The nickel-based intermetallic compound (2) preferably contains B, but may not contain B. The Ni content in the nickel-based intermetallic compound (2) is preferably 77.5 to 81.5 atomic %, more preferably 78 to 82 atomic %, and even more preferably 78.5 to 80.5 atomic %. Examples of the nickel-based intermetallic compound (2) include Ni3(Si,Ti)+Nb used in the examples described below and the intermetallic compounds described in Japanese Patent Application Laid-Open No. 2006-299410.

[0029] <Nickel-based intermetallic compounds (3)> The specific content of Si in the nickel-based intermetallic compound (3) is, for example, 10 The Si content may be in the range between any two of the values ​​exemplified herein. The specific content of Ti in the nickel-based intermetallic compound (3) is, for example, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, or 7.5 atomic %. The range of the Ti content may be between any two of the values ​​exemplified here. The specific content of Ta in the nickel-based intermetallic compound (3) is, for example, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, or 8.0 atomic %. The range of the Ta content may be between any two of the values ​​exemplified here. The Ni content in the nickel-based intermetallic compound (3) is, for example, 78.5 to 81.0 atomic %, preferably 78.5 to 80.5 atomic %. The content of B in the nickel-based intermetallic compound (3) is preferably 25 to 100 ppm by weight. Specific examples of the content of B include 25, 40, 50, 60, 75, 100, 150, 200, 300, 400, and 500 ppm by weight. The range of the content of B may be between any two of the values ​​exemplified here. Examples of the nickel-based intermetallic compound (3) include Ni3(Si,Ti)+Ta used in the examples described below and the intermetallic compounds described in WO 2011 / 030905.

[0030] (Al2O3, ZrO2-Y2O3 composite ceramic) The sliding surfaces of the plain bearing and the sleeve can be made of Al2O3 or a ZrO2-Y2O3 composite ceramic (hereinafter referred to as "ZrO2-Y2O3") containing (or consisting of) 97 mol% ZrO2 and 3 mol% Y2O3. These materials have excellent corrosion resistance and wear resistance, and their use in a plain bearing device results in a plain bearing device with excellent corrosion resistance and wear resistance.

[0031] As will be shown in the examples below, a sliding bearing device using material combination A or B shown in Table 1 below is excellent in both corrosion resistance and wear resistance.

[0032] [Table 1]

[0033] Furthermore, as will be shown in the examples described below, a sliding bearing device using any of the material combinations C to E shown in Table 2 below has excellent corrosion resistance and wear resistance, and has even better corrosion resistance and wear resistance than a sliding bearing device using the material combination shown in Table 1 above.

[0034] [Table 2]

[0035] Furthermore, as will be shown in the examples described below, a sliding bearing device using any of the material combinations F to H shown in Table 3 below has excellent corrosion resistance and wear resistance, and has extremely good corrosion resistance and wear resistance even compared to sliding bearing devices using the material combinations shown in Tables 1 and 2 above.

[0036] [Table 3]

[0037] In this embodiment, the sliding surfaces of the sliding bearing and the sliding surfaces of the sleeve are formed from the above-mentioned specific material. There is no particular limitation on the method of formation, but the specific material may be formed by forging or casting the specific material and then surface processing to obtain a sliding bearing and sleeve formed entirely from the specific material, including the sliding surfaces, or the above-mentioned specific material may be applied to the surfaces of a sliding bearing and sleeve that have been formed in advance to form sliding surfaces made of a coating material. A sliding bearing device can be manufactured by a conventionally known method using the sliding bearing manufactured as described above, and further, a pump can be manufactured by a conventionally known method using this sliding bearing device.

[0038] When the sliding surfaces of the sliding bearing and sleeve are formed with a coating material, the method for forming the coating material is not particularly limited, but it can be formed by plasma spraying, spray melting, weld overlay (TIG, PTA, LMD, MAG, SMAW), etc. Of these, LMD (laser metal deposition) is preferred because it can increase the hardness of the formed coating material. The thickness of the coating material is not particularly limited, but the lower limit can be 0.2 mm or more or 1 mm or more, and the upper limit can be 5 mm or less or 2 mm or less. These lower and upper limits can be combined arbitrarily.

[0039] 2. How to operate the pump A method of operating the pump of this embodiment includes a step in which a pump including the plain bearing device described in item 1 above includes a rotating shaft around which the sleeve is attached, and the rotating shaft is rotated by sliding the plain bearing and the sleeve, and molten salt is taken into the pump and then discharged to the outside of the pump. The temperature of the molten salt is not particularly limited, but the range of values ​​shown in the above item 1 can be used, and for example, the upper limit can be set to 600°C.

[0040] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the contents described in the examples. [Example]

[0041] (Corrosion resistance evaluation) Test pieces (length: 20 mm, width: 15 mm, thickness: 5 mm) having the compositions shown in Table 4 below were prepared. In Table 4, unless otherwise noted, the content of each element means mass%. Also, in Table 4, the numerical range of "AB" (A and B are numbers) means A or more and B or less. In addition to the above, test pieces (length: 20 mm, width: 15 mm, thickness: 5 mm) were also prepared, each having the composition of ZrO2-Y2O3 composite ceramic (referred to as ZrO2-Y2O3) consisting of 97 mol% zirconium oxide (ZrO2) and 3 mol% yttrium oxide (Y2O3), silicon carbide (SiC), silicon nitride (Si3N4), titanium carbide (TiC), and tungsten carbide (WC). SDSS, SUS316, and SUS420J2 shown in Table 4, as well as the above-mentioned SiC, Si3N4, TiC, and WC materials, correspond to the materials of the comparative examples of the present application, while the other materials shown in Table 4 and the above-mentioned ZrO2-Y2O3 correspond to the materials of the examples of the present application.

[0042] In addition, 20 g of salt consisting of 60 wt% NaNO3 and 40 wt% KNO3 was prepared in an alumina container. Each of the above test pieces was placed in the salt in the alumina container, and the entire container was heated to 600°C to melt the salt. Each test piece was then immersed in the molten salt for 96 hours while maintaining the temperature at 600°C. After immersion, each test piece was removed, washed with pure water, and then measured according to ASTM standards. The corrosion products adhering to the surface of each test piece were completely removed using a rust removal method conforming to G1. Based on the weight of each test piece before the immersion test (weight before test, unit: g), the weight of each test piece after the corrosion products were removed (weight after test, unit: g), and the surface area of ​​the test piece before the immersion test (test piece surface area, 20 mm x 15 mm), the weight loss per unit area (g / mm ) before and after the test was calculated using the following formula: 2 ) was calculated.

[0043]

number

[0044] The weight loss of each test piece was evaluated for corrosion resistance based on the criteria in Table 5. Furthermore, a Vickers hardness tester (AVK, manufactured by Akashi Seisakusho Co., Ltd.) was used to measure the The Vickers hardness of each test piece was measured based on JIS Z2244. The evaluation results of corrosion resistance and Vickers hardness values ​​are shown in Table 6.

[0045] [Table 4]

[0046] [Table 5]

[0047] [Table 6]

[0048] As shown in Table 6, all of the test specimens Nos. 1 to 13 were at or better than the usable level for evaluation of corrosion resistance. Among them, test specimens Nos. 6 and 8 exhibited good corrosion resistance, and test specimens Nos. 3 to 5, 10, and 11 exhibited extremely good corrosion resistance. Since corrosion resistance is an important indicator for use as a sliding member in a sliding bearing device for molten salt, the material compositions of Nos. 1 to 13, which were evaluated for corrosion resistance at or above a usable level, were then subjected to the following evaluation of wear resistance.

[0049] (Wear resistance evaluation) The viscosity of water at 20°C is about 1 mPa·s, which is close to that of molten salt at 600°C (composition: 100% by weight NaNO3). Therefore, the state of liquid film formation between the sliding surface of the plain bearing and the sliding surface of the sleeve is similar for 20°C water and 600°C molten salt, and the lubrication state is also similar. Taking this into consideration, water at 20°C is used to evaluate wear resistance. For bearing devices including plain bearings (devices consisting of the main shaft 2, sleeve housing 6, sleeve 3, plain bearing 4, plain bearing housing 8, and support member 9 in FIG. 2, bearing inner diameter 65 mm, bearing width 20 mm), each bearing device was prepared in which the materials for the sliding surface of the sleeve 3 ("rotating side" in Table 8) and the sliding surface of the plain bearing 4 ("fixed side" in Table 8) were set as shown in Table 8. Here, for Stellite (registered trademark) 6B, Al2O3, ZrO2-Y2O3, SDSS, and SUS316 in Table 8, sleeves 3 and plain bearings 4 formed entirely, including the sliding surfaces, from each of these materials were used. On the other hand, for the materials in Table 8 other than those mentioned above (SFNi4, SFNi5, Ni3(Al,V), Ni3(Si,Ti)+Nb, Ni3(Si,Ti)+Ta, Tribaloy (registered trademark) T700, Stellite (registered trademark) 6, and Stellite (registered trademark) 12), the surfaces of a sleeve 3 and a plain bearing 4 (all made of SUS316L) that had been previously formed were coated with the respective materials, and a sleeve 3 and a plain bearing 4 on which a sliding surface (thickness: 1 mm) made of the coating material was formed were used. Each bearing device was then submerged in water maintained at 20°C, and allowed to slide for 96 hours with a bearing surface pressure (bearing load / (bearing inner diameter x bearing width)) of 0.07 MPa and a sliding speed of 4.0 m / sec, and the wear rate (μm / h) of the sliding surface of the sliding bearing 4 was calculated. The wear rate of the sliding surface of each of the resulting sliding bearings was evaluated for wear resistance based on the criteria in Table 7 below. Table 8 shows the evaluation results for wear resistance.

[0050] [Table 7]

[0051] [Table 8]

[0052] From the results in Table 8, it can be seen that both the sliding surfaces on the rotating side and the fixed side are made of SFNi 4, SFNi 5, Ni3(Al,V), Ni3(Si,Ti)+Nb, Ni3(Si,Ti)+Ta, Tribaloy (registered trademark) T-700, Stellite (registered trademark) 6, Stellite (registered trademark) 12, Stellite (registered trademark) 6B, Al2O3, or ZrO2-Y2O The sliding bearing device formed by No. 3 had good or extremely good wear resistance. Among these, the following had particularly good wear resistance: a sliding bearing device in which the sliding surface on the rotating side was formed of Ni3(Si,Ti)+Nb or Ni3(Si,Ti)+Ta and the sliding surface on the fixed side was formed of Al2O3 or ZrO2-Y2O3; a sliding bearing device in which the sliding surface on the rotating side was formed of Al2O3 or ZrO2-Y2O3 and the sliding surface on the fixed side was formed of Ni3(Si,Ti)+Nb or Ni3(Si,Ti)+Ta; and a sliding bearing device in which both the sliding surfaces on the rotating side and the fixed side were formed of Al2O3 or ZrO2-Y2O3. On the other hand, a sliding bearing device in which either or both of the sliding surfaces on the rotating side and the fixed side are formed from SDSS or SUS316 has poor wear resistance.

[0053] (comprehensive evaluation) Since both corrosion resistance and wear resistance are necessary for use as sliding components, the evaluation results of the corrosion resistance and wear resistance described above were subjected to an overall evaluation based on the criteria in Table 9. The results of the overall evaluation are shown in Table 10.

[0054] [Table 9]

[0055] [Table 10]

[0056] From the results in Table 10, it can be seen that the sliding bearing devices (corresponding to the examples of the present application) in which both the rotating side and fixed side sliding surfaces are formed of SFNi 4, SFNi 5, Ni3(Al,V), Ni3(Si,Ti)+Nb, Ni3(Si,Ti)+Ta, Tribaloy (registered trademark) T-700, Stellite (registered trademark) 6, Stellite (registered trademark) 12, Stellite (registered trademark) 6B, Al2O3, or ZrO2-Y2O3 received the following overall evaluation. , usable, good, particularly good, or extremely good. Among these, sliding bearing devices in which the sliding surface on the rotating side was formed of Tribaloy® T-700 or Stellite® 12 and the sliding surface on the fixed side was formed of Ni3(Al,V), Ni3(Si,Ti)+Nb, Ni3(Si,Ti)+Ta, Tribaloy® T-700, Stellite® 12, Al2O3, or ZrO2-Y2O3, as well as sliding bearing devices in which the sliding surface on the rotating side was formed of Ni3(Al,V), Ni3(Si,Ti)+Nb, Ni3(Si,Ti)+Ta, Tribaloy® T-700, Stellite® 12, Al2O3, or ZrO2-Y2O3 and the sliding surface on the fixed side was formed of Tribaloy® T-700 or Stellite® 12, received a good overall evaluation. Furthermore, the sliding bearing devices in which both the rotating and fixed side sliding surfaces were formed from Ni3(Al,V), Ni3(Si,Ti)+Nb or Ni3(Si,Ti)+Ta, the sliding bearing devices in which the rotating side sliding surface was formed from Ni3(Al,V) and the fixed side sliding surface was formed from Al2O3 or ZrO2-Y2O3, and the sliding bearing devices in which the rotating side sliding surface was formed from Al2O3 or ZrO2-Y2O3 and the fixed side sliding surface was formed from Ni3(Al,V) performed particularly well in terms of the overall evaluation. Furthermore, the overall evaluation was extremely favorable for sliding bearing devices in which the sliding surface on the rotating side was formed of Ni3(Si,Ti)+Nb or Ni3(Si,Ti)+Ta and the sliding surface on the fixed side was formed of Al2O3 or ZrO2-Y2O3, sliding bearing devices in which the sliding surface on the rotating side was formed of Al2O3 or ZrO2-Y2O3 and the sliding surface on the fixed side was formed of Ni3(Si,Ti)+Nb or Ni3(Si,Ti)+Ta, and sliding bearing devices in which both the sliding surfaces on the rotating side and the fixed side were formed of Al2O3 or ZrO2-Y2O3. On the other hand, the sliding bearing device (corresponding to the comparative example of the present application) in which either or both of the sliding surfaces on the rotating side and the fixed side were formed from SDSS or SUS316 was rated as unusable in the overall evaluation.

[0057] From the above results, the sliding surface and Bis It has been found that a sliding bearing device for molten salt, in which the sliding surface of the sleeve is formed from at least one material selected from the group consisting of nickel-based alloys, cobalt-based alloys, nickel-based intermetallic compounds, Al2O3, and ZrO2-Y2O3 composite ceramics containing 97 mol% ZrO2 and 3 mol% Y2O3, has excellent corrosion resistance and wear resistance. [Explanation of symbols]

[0058] 1. Casing 2...Spindle 3 Sleeve 4. Plain bearing 5. Impeller 6···Sleeve housing 7. Sliding surface (sliding surface) 8. Plain bearing housing 9. Support member

Claims

1. A molten salt sliding bearing device for use in a pump, comprising: Plain bearings, and A sleeve that slides with the plain bearing Equipped with the Vickers hardness of the sliding surface of the sliding bearing and the sliding surface of the sleeve is 330 or more; The sliding surface of the sliding bearing and the sliding surface of the sleeve are made of a nickel-based alloy, a cobalt-based alloy, a nickel-based intermetallic compound, or Al ２ O ３ , and ZrO ２ 97 mol% and Y ２ O ３ ZrO containing 3 mol% ２ -Y ２ O ３ It is formed from at least one selected from the group consisting of composite ceramics, The nickel-based alloy A nickel-based alloy (1) consisting of, in mass%, C: 0.4 to 1.1%, Co: 0 to 1%, Cr: 12 to 26%, Cu: 0 to 4%, Mo: 0 to 4%, Fe: 0 to 5%, B: 2.5 to 4.5%, Si: 2.0 to 5.0%, and the balance Ni and inevitable impurities; A nickel-based alloy (2) consisting of, in mass%, C: 0 to 0.08%, Co: 0 to 1.5%, Cr: 16%, Mo: 32%, Fe: 0 to 1.5%, Si: 3.4%, and the balance being Ni and unavoidable impurities; or It is a combination of these, The cobalt-based alloy is Cobalt-based alloy (1) consisting of, in mass%, C: 0.9 to 1.7%, Ni: 0 to 3%, Cr: 26 to 32%, W: 3 to 9.5%, Mo: 0 to 1%, Mn: 0 to 1%, Fe: 0 to 3%, Si: 0 to 2%, and the balance Co and inevitable impurities; A cobalt-based alloy (3) consisting of, in mass%, C: 0.9 to 1.4%, Ni: 0 to 3%, Cr: 28 to 32%, W: 3.5 to 5.5%, Mo: 0 to 1.5%, Mn: 0 to 2%, Fe: 0 to 3%, Si: 0 to 2%, and the balance being Co and unavoidable impurities; or It is a combination of these, The nickel-based intermetallic compound is A nickel-based intermetallic compound (1) comprising Al: more than 5 atomic % and 13 atomic % or less, V: 9.5 atomic % or more and less than 17.5 atomic %, Ti: 5 atomic % or less, B: 1000 weight ppm or less, and the balance being Ni and unavoidable impurities; A nickel-based intermetallic compound (2) consisting of Si: 1 to 10.5 atomic %, Ti: 5 to 16 atomic %, Nb: 0 to 10 atomic %, B: 0 to 1000 weight ppm, and the balance being Ni and unavoidable impurities; A nickel-based intermetallic compound (3) containing 25 to 500 ppm by weight of B relative to the weight of the intermetallic compound having a composition of 100 atomic % in total consisting of Si: 10.0 atomic % or more and 12.0 atomic % or less, Ti: 1.5 atomic % or more but less than 7.5 atomic %, Ta: more than 2.0 atomic % and 8.0 atomic % or less, and the balance being Ni and unavoidable impurities; or A combination of two or more of these The sliding bearing device for molten salt.

2. 2. The sliding bearing device for use with molten salt according to claim 1, wherein the sliding surface of the sliding bearing and the sliding surface of the sleeve are formed from a coating material, and the thickness of the coating material is 0.2 mm or more.

3. 3. The sliding bearing device for use with molten salt according to claim 2, wherein the coating material has a thickness of 1 mm or more.

4. 4. The sliding bearing device for use with molten salt according to claim 1, wherein the molten salt comprises a eutectic salt of sodium nitrate, sodium nitrite, and potassium nitrate.

5. 4. The sliding bearing device for use with molten salt according to claim 1, wherein the molten salt is a carbonate mixture containing potassium carbonate, sodium carbonate, and lithium carbonate.

6. A pump equipped with the sliding bearing device according to any one of claims 1 to 5.

7. 7. A method of operating a pump according to claim 6, comprising the steps of: the pump including a rotating shaft about which the sleeve is mounted; a step of rotating the rotating shaft by sliding the plain bearing and the sleeve, and taking in molten salt into the pump and then discharging it to the outside of the pump.

8. 8. The method for operating a pump according to claim 7, wherein the temperature of the molten salt is 300°C or higher and 600°C or lower.

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