WO2011152332A1

WO2011152332A1 - Gasket for pressure vessel, and method for producing said gasket

Info

Publication number: WO2011152332A1
Application number: PCT/JP2011/062325
Authority: WO
Inventors: 孝之島宗; 重治赤塚; 桂一郎松下
Original assignee: 株式会社フルヤ金属
Priority date: 2010-06-03
Filing date: 2011-05-30
Publication date: 2011-12-08
Also published as: JPWO2011152332A1

Abstract

Provided is a gasket for a pressure vessel, wherein the gasket is suitable for use as a consumable part, exerts sufficient strength, sealing properties and corrosion resistance even in a high-temperature and high-pressure state, has adequate surface hardness in relation to the material of the flange of the pressure vessel, and does not cause mutual diffusion with the flange. Specifically provided is a gasket (100) for a pressure vessel, wherein the gasket is disposed on the opening section of the pressure vessel and hermetically seals the aforementioned pressure vessel as a consequence of the sealing section of the gasket coming into contact with a flange having a surface formed from iridium or an iridium-based alloy. Additionally, the gasket is characterized in that a nickel-based alloy is used as a base (1), a nitride layer (2) formed from the nitride of a nickel-based alloy is formed on the surface of the base (1), and a coating layer (3) containing the oxide of a platinum-group metal is formed on the surface of the nitride layer (2).

Description

Gasket for pressure vessel and manufacturing method thereof

The present invention relates to a gasket used for a pressure vessel, and in particular, a pressure that is provided at an opening of the pressure vessel, and a sealing portion is in contact with a flange having a surface of iridium or an iridium base alloy to seal the pressure vessel. The present invention relates to a gasket for containers.

The hydrothermal synthesis method and the thermal synthesis method are methods in which chemical reactions such as dissolution, decomposition, and crystal growth are performed in a high-temperature and high-pressure solvent. The hydrothermal synthesis method uses water as a solvent. The low temperature synthesis method uses ammonia (ammonium chloride) as a solvent. In these methods, a pressure vessel called an autoclave is used.

The hydrothermal synthesis method and the low-temperature synthesis method are sometimes carried out at about 100 to 400 ° C. and about 100 to 300 atm in the vicinity of the critical point for the purpose of improving reaction efficiency and reacting a hardly decomposed substance or a hardly soluble substance. In recent years, hydrothermal synthesis methods and low-temperature synthesis methods have been used in ultra-high temperature and ultra-high pressure conditions far beyond the critical point for the purpose of further improving the reaction efficiency and reacting substances that could not be decomposed or dissolved near the critical point. For example, experiments at 800 ° C. and 4000 atmospheres have been conducted, and the conditions are expected to become more severe. Under such conditions, the pressure vessel is required to withstand use at, for example, an ultra-high temperature from room temperature to 1000 ° C. and an ultra-high pressure of 1 to 5000 atmospheres.

Under such conditions, the metals that can be used are limited, and as a physical material that retains physical strength and can withstand practical use, for example, nickel sold under the trade names INCONEL and HASTELLOY Base alloys and other equivalent metals are used. These metals are known to have high temperature resistance and extremely excellent physical strength at high temperatures.

However, although the nickel-based alloy is said to be chemically resistant, for example, a hydrothermal synthesis method or a low-temperature synthesis method in the vicinity of critical points performed at 100 to 400 ° C. and 100 to 300 atm. Under these conditions, its chemical resistance is not sufficient. Furthermore, since the melting point of the nickel-based alloy is about 1300 ° C., the service temperature varies depending on the use conditions, but is about 800 ° C. from the viewpoint of physical strength, and in a supercritical state exceeding 800 ° C. It is not suitable for use under the conditions of hydrothermal synthesis or low-temperature synthesis. Therefore, a noble metal such as a platinum group metal or gold is often used in a portion of the pressure vessel that comes into contact with a chemical solution or a chemical atmosphere.

However, since platinum group metals are extremely expensive, there are problems such as a very high price when the pressure vessel is formed of a bulk metal, poor workability, and insufficient physical strength. For this reason, usually, a two-layered autoclave using a platinum group metal or a platinum group metal base alloy for the purpose of chemical resistance is used as an inner cylinder in which the physical strength is held by the nickel base alloy as described above. (For example, refer to Patent Document 1).

In the pressure vessel including Patent Document 1, the main body and the lid are fixed by a nut or a clamp. The main body has a bottomed cylindrical shape with one end opened, and a flange (hereinafter sometimes referred to as a lower flange) is provided on the periphery of the opening. The lid is also provided with a flange (hereinafter sometimes referred to as an upper flange), and the pressure vessel is structured to seal between the upper flange and the lower flange via a gasket. Therefore, since a large pressure is applied to the flange, it is necessary to have a sufficient pressure resistance. Further, when the pressure vessel is sealed, the upper flange, the gasket, and the lower flange are in contact with each other by a line or a surface to form a seal portion (hereinafter, the corresponding contact portion is referred to as a seal portion). In particular, a high surface hardness is required for the seal portion.

Various forms have been proposed in order to give a sufficient pressure resistance to the flange. For example, even if there is a difference in thermal expansion, there is a shape that prevents it from affecting the pressure resistance. When the surface hardness of the flange and the gasket is small, the flange and the gasket are deformed by tightening, and accordingly, the contact area between the flange and the gasket is increased. Then, since the pressure applied to the seal portion is relatively small, there is a problem that sufficient sealing cannot be performed. Further, if the flange is harder than the gasket, there is a problem that the flange belonging to the inner cylinder is deformed at the time of tightening, shortening the life of the inner cylinder, and thus shortening the life of the apparatus. Therefore, the gasket needs to be softer than the flange. With this configuration, the flange is not deformed and the gasket is deformed. Therefore, only the deformed gasket is replaced, and the inner cylinder can be used repeatedly.

For the flange, platinum group metals having high surface hardness even at high temperatures or alloys thereof are often used. For the gasket, a heat-resistant and corrosion-resistant alloy is usually used, and a nickel-based alloy is mainly used. However, the nickel base alloy has a problem that softening occurs much more severely than the platinum group metal under a very high temperature condition such as a supercritical state exceeding 800 ° C., so that it cannot be applied as a gasket as it is. Further, since the gasket has a portion exposed directly in the pressure vessel, it is desirable that at least the exposed surface be a platinum group metal surface having corrosion resistance.

As a method of forming a platinum group metal layer on the surface of the base material, the use is different, but a titanium nitride layer is formed on the surface of the titanium base material in advance for use as an electrode, and platinum group metal and / or platinum group metal oxidation is performed on the surface. A technique for coating an electrode material including an object is disclosed (for example, see Patent Document 2).

JP 2006-193355 A JP 2006-130486 A

As described above, an appropriate surface hardness and corrosion resistance in a high temperature and high pressure state are required for a gasket for a pressure vessel. Patent Document 1 proposes to use a platinum group metal or an alloy thereof as a material of the gasket. However, an expensive platinum group metal or an alloy thereof is suitable for use as a consumable part such as a gasket. There is no problem.

It is preferable to select the material of the flange and gasket relatively. As described above, it is preferable to make the surface hardness of the gasket smaller than the surface hardness of the flange. Furthermore, if the same material is selected from platinum group metals for the flange and gasket, the flange seal and gasket may adhere to each other due to mutual diffusion while the pressure vessel is operated at high temperature and high pressure. It is preferable to do. However, although some proposals have been made regarding the shape of the gasket, there is almost no knowledge and literature regarding the material of the gasket, it has corrosion resistance, and has an appropriate surface hardness in relation to the material of the flange. At present, there is no gasket that protects the body.

Patent Document 2 proposes a technique for forming a platinum group metal layer and / or a platinum group metal oxide layer on the surface of a base material. However, this technique is only an electrode technique, and the surface strength is appropriately set. It's not about handling.

The present invention has been made to solve the conventional problems as described above. That is, an object of the present invention is a gasket for a pressure vessel that is provided in an opening of a pressure vessel and a sealing portion abuts on a flange having a surface of iridium or an iridium base alloy to seal the pressure vessel. It is suitable for use as a consumable part, has sufficient strength, sealability and corrosion resistance even in high-temperature and high-pressure conditions, and has an appropriate surface hardness in relation to the material of the flange of the pressure vessel. It is to provide a gasket for a pressure vessel that does not cause diffusion.

As a result of intensive investigations to solve the above problems, the present inventors have made a nickel-base alloy usable as a consumable part as a base material, and nitriding the surface of the base material to improve surface hardness and surface corrosion resistance. By improving and further nitriding the surface with a platinum group metal or a platinum group metal base alloy and performing surface oxidation treatment and diffusion treatment, for example, it is sufficient even in an ultrahigh temperature and high pressure state of 800 ° C. and 4000 atm. The inventors have found that pressure resistance and corrosion resistance can be imparted, and have completed the present invention. That is, the gasket for a pressure vessel according to the present invention is for a pressure vessel that seals the pressure vessel by being provided at the opening of the pressure vessel and having a seal portion in contact with a flange having a surface of iridium or an iridium-based alloy. A coating layer comprising a nickel-base alloy as a base material, a nitride layer of the nickel-base alloy formed on the surface of the base material, and a platinum group metal oxide on the surface of the nitride layer Is formed.

In the pressure vessel gasket according to the present invention, the platinum group metal is preferably iridium, ruthenium, rhodium, or a base alloy thereof. The surface of the gasket can have a more appropriate surface hardness.

In the pressure vessel gasket according to the present invention, it is preferable that the nitride layer has a thickness of 1 to 10 μm, and the coating layer has a thickness of 0.01 to 3 μm. The surface of the gasket can have an appropriate surface hardness. Moreover, it is possible to prevent the nickel-base alloy of the base material from being exposed and to further improve the corrosion resistance.

In the pressure vessel gasket according to the present invention, the Vickers hardness of the surface of the sealing portion measured according to JIS Z 2244: 2009 is preferably 300 Hv to 400 Hv. By making the hardness smaller than that of the sealing portion of the flange, the deformation of the flange can be prevented and the life of the pressure vessel can be kept longer.

In the gasket for a pressure vessel according to the present invention, it is preferable that the platinum group metal is diffused from the coating layer into the nitride layer. Adhesion between each layer can be made more reliable, and a gasket with higher pressure resistance can be obtained. Further, the surface hardness of the gasket can be optimized and the corrosion resistance can be further improved.

The method for manufacturing a pressure vessel gasket according to the present invention includes: a pressure vessel that seals the pressure vessel by being in contact with a flange having a surface of iridium or an iridium-based alloy provided at an opening of the pressure vessel. A method for manufacturing a gasket for use in a process comprising: nitriding treatment using a nickel-based alloy as a base material and nitriding the surface of the base material to form a nitride layer; and a platinum group metal on the surface of the nitride layer. A coating step in which a coating solution containing the compound is applied to form a coating layer; a thermal decomposition step in which the coating layer is thermally decomposed to form a coating precursor layer; and a thermal decomposition step in an atmosphere containing oxygen. And a stabilization step of heating the coating precursor layer to a coating layer containing the platinum group metal oxide by heating at a temperature higher than the heating temperature.

In the method for manufacturing a pressure vessel gasket according to the present invention, the nitriding treatment step is preferably performed by heating in an atmosphere containing nitrogen gas, ammonia gas, or a nitrogen-hydrogen mixed gas. Nitriding can be performed more efficiently.

In the method for manufacturing a pressure vessel gasket according to the present invention, it is preferable that the coating step and the thermal decomposition step are repeated a plurality of times so that the thickness of the coating layer is 0.01 to 3 μm. It is possible to obtain a uniform coating layer with less pores, and as a result, the surface of the gasket can be more reliably coated with the platinum group metal oxide.

The present invention is a gasket for a pressure vessel which is provided at an opening of a pressure vessel and seals the pressure vessel by contacting a flange having a seal portion having a surface of iridium or an iridium base alloy, and is a consumable part Suitable for use as a material, has sufficient strength, sealability and corrosion resistance even in high-temperature and high-pressure conditions, and has an appropriate surface hardness in relation to the flange material of the pressure vessel, and does not cause mutual diffusion with the flange. A gasket for a pressure vessel can be provided.

It is a schematic diagram which shows one form of the cross-sectional structure of the gasket for pressure vessels which concerns on this embodiment. It is sectional drawing which shows an example of a pressure vessel. It is a figure for demonstrating the example of a form of the gasket in a medium-sized pressure vessel, (a) is a cross-sectional partial enlarged view which shows one form of a flange and a gasket, (b) is a top view which shows one form of a gasket It is. It is a figure for demonstrating the form example of the gasket in a large sized pressure vessel, (a) is a cross-sectional partial enlarged view which shows one form of a flange and a gasket, (b) is a top view which shows one form of a gasket It is.

Hereinafter, the present invention will be described in detail with reference to embodiments, but the present invention is not construed as being limited to these descriptions. As long as the effect of the present invention is exhibited, the embodiment may be variously modified.

FIG. 1 is a schematic diagram showing an embodiment of a cross-sectional structure of a pressure-resistant container gasket according to the present embodiment. The gasket 100 for a pressure vessel according to the present embodiment is provided for an opening of a pressure vessel, and a seal portion is in contact with a flange having a surface of iridium or an iridium base alloy to seal the pressure vessel. A gasket comprising a nickel-base alloy as a base material 1, a nickel-base alloy nitride layer 2 formed on the surface of the base material 1, and a coating layer containing a platinum group metal oxide on the surface of the nitride layer 2 3 is formed.

FIG. 2 is a cross-sectional view showing an example of a pressure vessel. The pressure vessel 900 has a main body 81 and a lid 91. The main body 81 and the lid 91 are fixed by a fixing jig 72 such as a nut or a clamp. An intermediate layer 82 is disposed on the inner surface of the main body 81, and an inner cylinder 83 is disposed on the inner surface of the intermediate layer 82. On the other hand, an intermediate layer 92 is disposed on the inner surface of the lid 91, and an innermost layer 93 is disposed on the inner surface of the intermediate layer 92.

The main body 81 and the lid 91 are made of a heat-resistant alloy such as low alloy steel or nickel chrome alloy. The intermediate layer 82 and the intermediate layer 92 are made of a nickel-based alloy having excellent heat and corrosion resistance such as trade names Inconel and Hastelloy. The inner cylinder 83 and the innermost layer 93 are made of a platinum group metal or a platinum group metal base alloy. The platinum group metal or platinum group metal base alloy is, for example, platinum, platinum base alloy, iridium, iridium base alloy, ruthenium, ruthenium base alloy, rhodium, rhodium base alloy, and platinum is often used among them. . Examples of the platinum-based alloy include a platinum-iridium alloy, a platinum-ruthenium alloy, a platinum-rhodium alloy, a platinum-gold alloy, and a platinum-rhenium alloy. Examples of iridium based alloys include iridium-ruthenium alloys, iridium-platinum alloys, iridium-rhodium alloys, iridium-gold alloys, and iridium-rhenium alloys. Examples of the ruthenium-based alloy include a ruthenium-iridium alloy, a ruthenium-platinum alloy, a ruthenium-rhodium alloy, a ruthenium-gold alloy, and a ruthenium-rhenium alloy. Examples of rhodium-based alloys include rhodium-iridium alloys, rhodium-platinum alloys, rhodium-ruthenium alloys, rhodium-gold alloys, and rhodium-rhenium alloys.

The pressure vessel 900 has a structure in which a lower flange 84 provided in the opening of the main body 81 and an upper flange 94 provided in the lid 91 are sealed via a gasket 71. The lower flange 84, the gasket 71, and the upper flange 94 are in contact with each other at a linear or planar seal portion to form a seal portion. The sealing part of the lower flange 84 and the upper flange 94 has the surface of iridium or an iridium base alloy. Examples of the iridium-based alloy include an iridium-platinum alloy, an iridium-ruthenium alloy, an iridium-rhodium alloy, an iridium-gold alloy, and an iridium-rhenium alloy. The pressure vessel 900 is suitably used for producing a single crystal by a hydrothermal synthesis method or a low temperature synthesis method. Since the surface of the seal portion is iridium or an iridium-based alloy having a higher hardness among the platinum group metals, it is particularly suitable when used under supercritical high-temperature and high-pressure conditions. In the present embodiment, the pressure vessel 900 is a sealing method in which the lower flange 84 and the upper flange 94 of the main body 81 and the lid 91 are sealed via the gasket 71, and the sealing portions of the lower flange 84 and the upper flange 94 are sealed. If it has the surface of iridium or an iridium base alloy, it will not restrict | limit to the kind of pressure vessel.

FIG. 3 is a view for explaining an example of a gasket in a medium-sized pressure vessel, (a) is an enlarged sectional view showing one embodiment of a flange and a gasket, and (b) is one embodiment of the gasket. FIG. 4A and 4B are views for explaining an example of a gasket in a large pressure vessel. FIG. 4A is an enlarged cross-sectional view showing an embodiment of a flange and a gasket, and FIG. 4B is an embodiment of the gasket. FIG. Here, the medium-sized pressure vessel is a pressure vessel having an inner cylinder with an inner diameter of 20 to 70 mm and a capacity of 0.0001 to 0.008 m ³ . The large pressure vessel is a pressure vessel having an inner cylinder with an inner diameter of 70 to 150 mm and a capacity of 0.008 to 0.05 m ³ .

The inner cylinder 83 and the lower flange 84 may be integrally formed of iridium or an iridium-based alloy, or may be formed of different materials. In the case of molding with different materials, the present embodiment is not limited to the method of joining the inner cylinder 83 and the lower flange 84. As a method for joining, for example, as shown in FIGS. 3 and 4, there is a method in which a flange-like attachment portion 83 a is provided on the periphery of the opening of the inner cylinder 83 and a lower flange 84 is attached thereon by welding. The lower flange 84 is preferably formed integrally with iridium or an iridium base alloy, but the outermost layer of iridium or iridium base alloy and another platinum group so that at least the surface of the seal portion is iridium or iridium base alloy. It is good also as a form which the lower layer which consists of metals made | formed the laminated body. The form of the laminated body is, for example, a form in which the outermost layer is iridium and the lower layer is any one of platinum, ruthenium, rhodium or a base alloy thereof, the outermost layer is iridium based alloy, and the lower layer is platinum, ruthenium, rhodium or Any form of the base alloy, the outermost layer is iridium, an intermediate layer is provided between the outermost layer and the lower layer, the intermediate layer is an iridium alloy, and the lower layer is platinum, ruthenium, rhodium, or any of its base alloys It is a form.

The gasket has various shapes depending on conditions such as the shape of the flange of the pressure vessel used and the pressure. For example, in a medium-sized pressure vessel as shown in FIG. 3, a gasket 71a called a lens ring is used which has a tapered shape that maximizes the thickness of the inner peripheral side of the ring and decreases toward the outer periphery. The Moreover, in the large pressure vessel 900 as shown in FIG. 2, the thickness is made thinner than the ring portion on the outer peripheral side of the ring 77 called the gray lock seal ring with the structure as shown in FIG. A gasket 71b having a shape in which an outer ring 78 is formed is used. The lens ring type gasket 71a and the gray lock seal ring type gasket 71b, and the upper flange 94 and the lower flange 84 are in contact with each other at the seal location S. In addition, since the seal | sticker location S has contact | abutted by the linear form with a very small contact area, high sealing performance can be ensured. Further, the gray lock seal ring type gasket is referred to as a self-tightening gasket, and when the pressure in the pressure vessel increases, the diameter of the gasket expands and enters the gap between the upper flange 94 and the lower flange 84. The airtightness between the pressure vessel main body and the lid can be made extremely high.

The size of the gasket differs depending on the specifications of the pressure vessel to be applied. However, in the lens ring type gasket 71a as shown in FIG. 3, generally, the inner dimension e is 20 to 70 mm, and the outer dimension f is 30. The wall thickness is 10 to 30 mm at the thickest part. In the gray rock seal ring type gasket 71b as shown in FIG. 4, the inner dimension g of the ring 77 is generally 70 to 150 mm, the outer dimension h of the outer ring 78 is 100 to 200 mm, The thickness is 10 to 30 mm at the thickest part.

The gasket for a pressure vessel according to the present embodiment has a configuration in which a nitride layer 2 and a coating layer 3 are sequentially coated on the surface of a substrate 1 as shown in FIG. The base material 1 is a nickel base alloy. As the nickel-base alloy, for example, those sold under the trade names Inconel, Hastelloy, and equivalents thereof can be used. Further, stainless steel such as SUS316L mainly composed of chromium and nickel can be used. The nickel content in the substrate 1 is preferably 8 to 80% by mass. More preferably, it is 8 to 70% by mass.

The nitride layer 2 contains a nickel-based alloy nitride. As mentioned above, nickel-base alloys are said to have high-temperature resistance and corrosion resistance, but their physical strength and corrosion resistance are not sufficient under the conditions of hydrothermal synthesis or low-temperature synthesis in supercritical conditions. In this embodiment, the nitride layer 2 is formed on the surface to improve the physical strength and corrosion resistance of the surface at high temperatures. Further, in the low temperature synthesis method, it is preferable that oxygen does not exist, and therefore it is preferable that no oxide is formed on the surface of the substrate 1. By forming the surface of the substrate 1 as the nitride layer 2, it is possible to prevent oxides from being formed on the surface of the substrate 1.

The nitride layer 2 only needs to be formed on the surface of at least the portion of the base material 1 exposed in the pressure vessel, but is more preferably formed on the entire surface of the gasket. The nitride content of the nitride layer 2 has a distribution in which the surface is the largest and gradually decreases toward the inside of the substrate.

The coating layer 3 contains a platinum group metal oxide. In the pressure vessel gasket according to the present embodiment, the platinum group metal is preferably iridium, ruthenium, rhodium, or a base alloy thereof. Since these platinum group metals and their base alloys have higher hardness among platinum group metals, the surface hardness of the gasket can be set within a predetermined range. The oxides of the platinum group metals and their base alloys are, for example, iridium oxide, ruthenium oxide, rhodium oxide, iridium oxide / platinum, iridium ruthenium oxide, iridium rhodium oxide, iridium rhenium oxide, iridium oxide / gold.

The covering layer 3 only needs to be formed at least in a portion of the gasket that is exposed in the pressure vessel. Particularly preferably, the covering layer 3 covers the entire surface of the gasket. By forming it on the entire surface of the gasket, the durability of the gasket can be improved. Moreover, even when used at high temperature and high pressure under supercritical conditions, appropriate surface hardness and corrosion resistance can be further improved.

The content of the platinum group metal oxide in the coating layer 3 is preferably 90% by mass or more. More preferably, it is 80% by mass or more, and particularly preferably 100% by mass, that is, a form in which all is an oxide of a platinum group metal and an unoxidized platinum group metal is not exposed. If it is less than 90% by mass, the surface of the gasket and the surface of the sealing portion of the flange may be mutually diffused and bonded during operation of the pressure vessel. In the low temperature synthesis method, it is preferable that no oxide is formed. However, an oxide of a platinum group metal is chemically extremely stable, and its oxide layer is dense. Therefore, since the influence on the synthesis reaction is extremely small, it can be used in the low-temperature synthesis method.

In the pressure vessel gasket 100 according to this embodiment, the thickness of the nitride layer 2 is 1 to 10 μm. More preferably, it is 3 to 5 μm. If it is less than 1 μm, the surface hardness and corrosion resistance are insufficient. When it exceeds 10 μm, the surface hardness becomes higher than that of the flange, and the flange is deformed.

In the pressure vessel gasket according to the present embodiment, the thickness of the coating layer 3 is preferably 0.01 to 3 μm. More preferably, it is 0.1 to 3 μm. If the thickness is less than 0.01 μm, the surface of the gasket cannot be sufficiently covered. If it exceeds 3 μm, it will be easy to peel depending on handling conditions such as rapid heating and quenching. Moreover, the usage-amount of a platinum group metal increases and it is economically unpreferable. Platinum group metal oxides are chemically very stable and have a very low impact on low-temperature synthesis.However, by reducing the amount of platinum group metal oxides, the impact on low-temperature synthesis is reduced. It can be further reduced. In the present embodiment, by providing the nitride layer 2 between the base material 1 and the coating layer 3, the thickness of the coating layer 3 containing an oxide can be made as thin as possible.

In the pressure vessel gasket according to the present embodiment, it is preferable that the Vickers hardness of the surface of the seal portion measured according to JIS Z 2244: 2009 is 300 Hv to 400 Hv (300 Hv or more and 400 Hv or less). More preferably, it is 315Hv to 385Hv. If the Vickers hardness is less than 300 Hv, a large deformation (crushing) occurs due to tightening, and a sufficient seal cannot be obtained. When the Vickers hardness exceeds 400 Hv, the surface hardness becomes higher than that of the flange, and the flange is deformed. As a result, the life of the pressure vessel is shortened. Usually, the surface hardness of the flange and gasket that can withstand use under a pressure condition of 1000 atm or higher is assumed to be 300 Hv or more in terms of Vickers hardness. In this embodiment, the seal portion of the flange of the pressure vessel has a surface made of iridium or an iridium-based alloy, and the surface hardness is 350 Hv to 450 Hv in terms of Vickers hardness. In this embodiment, since the surface hardness of the seal location of the gasket is in the above range, the surface hardness of the seal location of the gasket can be made smaller than the surface hardness of the seal location of the flange. The nickel-base alloy has a Vickers hardness of about 200 Hv. However, the Vickers hardness at the gasket seal portion can be obtained by forming the nitride layer 2 on the surface of the base material 1 so that the surface hardness is within a predetermined range, for example, The Vickers hardness can be 300Hv to 400Hv.

In the pressure vessel gasket according to the present embodiment, it is preferable that a platinum group metal is diffused from the coating layer 3 in the nitride layer 2. Adhesion between each layer can be made more reliable, and a gasket with higher pressure resistance can be obtained. In addition, the hardness of the gasket surface can be optimized.

The method for manufacturing a gasket for a pressure vessel according to the present embodiment includes a nitriding process in which a nickel-based alloy is used as a base material and the surface of the base material is nitrided to form a nitride layer, and the surface of the nitride layer is formed. A coating step of applying a coating solution containing a platinum group metal compound to form a coating layer; a thermal decomposition step of thermally decomposing the coating layer to form a coating precursor layer; and an atmosphere containing oxygen, And a stabilization step of heating the coating precursor layer to a coating layer containing the platinum group metal oxide by heating at a temperature higher than the heating temperature of the pyrolysis step.

In the nitriding treatment step, the surface of the substrate 1 is nitrided by heating in a gas containing nitrogen or a nitrogen compound. The nitriding treatment may be performed on at least the surface of the portion of the substrate 1 that is exposed in the pressure vessel, but more preferably on the entire surface. In the present embodiment, the nitride layer 2 may be formed on the surface of the substrate 1 and is not limited by the type of atmospheric gas in the nitriding treatment, but more preferably nitrogen gas, ammonia gas or nitrogen-hydrogen mixed The atmosphere includes gas. The atmospheric temperature and processing time vary depending on the material of the base material 1, the atmospheric gas, the shape of the gasket, and the like, but it is preferable to select conditions under which the thickness and surface hardness of the nitride layer 2 are within a predetermined range.

The atmospheric temperature is preferably 500 to 1200 ° C., and the treatment time is preferably 1 to 3 hours. For example, when pure nitrogen gas is used as the atmospheric gas, the thickness of the nitride layer may be 1 to 10 μm by setting the atmospheric temperature to 700 to 1200 ° C. and the processing time to 1 to 3 hours. And the surface hardness can be within a predetermined range. When ammonia gas is used as the atmospheric gas, the thickness of the nitride layer can be reduced to 1 to 10 μm by setting the atmospheric temperature to 500 to 900 ° C. and the processing time to 1 to 3 hours. The hardness can be within a predetermined range. Further, when a nitrogen-hydrogen mixed gas is used as the atmospheric gas, the thickness of the nitride layer is set to 1 to 10 μm by setting the atmospheric temperature to 500 to 900 ° C. and the processing time to 1 to 3 hours. And the surface hardness can be within a predetermined range. In the nitrogen-hydrogen mixed gas, the ratio of nitrogen to hydrogen is preferably nitrogen: hydrogen = 60: 40 to 90:10. More preferably, nitrogen: hydrogen = 80: 20 to 85:15.

In addition, as a pretreatment of the nitriding treatment step, it is preferable to process a nickel-base alloy into a gasket shape and perform surface polishing and cleaning.

In the coating step, a coating solution containing a platinum group metal compound is coated on the surface of the nitride layer obtained in the nitriding step, and dried to form a coating layer. The coating solution is not particularly limited in the present embodiment as long as a layer containing a platinum group metal can be formed by thermal decomposition performed later. For example, it is a solution in which a platinum group metal salt as a platinum group metal compound, water or alcohol as a solvent, and turpentine oil as a reducing agent are blended. Examples of the platinum group metal salt include iridium chloride, ruthenium chloride, rhodium chloride, iridium nitrate, ruthenium nitrate, rhodium nitrate, chloroplatinic acid, and dinitrodiammine platinum. Further, a platinum group metal-based alloy may be formed by thermal decomposition using a combination of a plurality of types of platinum group metal compounds. Examples of the platinum group metal-based alloy include ruthenium-platinum alloy, iridium-platinum alloy, iridium-ruthenium alloy, ruthenium-gold alloy, iridium-gold alloy, and iridium-rhenium alloy. For example, ruthenium-platinum alloy is ruthenium chloride. And a coating solution containing chloroplatinic acid can be applied and thermally decomposed. The blending ratio of ruthenium chloride and chloroplatinic acid is preferably 60:40 to 90:10, and more preferably 70:30 to 80:20.

In the thermal decomposition step, the coating layer obtained in the coating step is subjected to thermal decomposition to form a coating precursor layer containing a platinum group metal. The thickness of the coating precursor layer is preferably 0.01 to 3 μm when the coating layer is formed, and it is preferable to repeat the coating step and the thermal decomposition step several times until the thickness reaches the thickness. A uniform coating layer with few pores can be obtained, and the surface of the gasket can be more reliably coated with an oxide of a platinum group metal by an oxidation treatment performed later. The coating amount per coating step is preferably 0.008 to 0.2 μm. More preferably, it is 0.01 to 0.1 μm.

Thermal decomposition can be performed in a heating furnace such as a muffle furnace. The temperature is preferably 300 to 700 ° C. More preferably, it is performed at 500 to 600 ° C. The treatment time varies depending on the temperature and the components of the coating solution, but is preferably 5 to 15 minutes. The thermal decomposition is preferably performed in an air atmosphere.

In the stabilization step, the coating precursor layer obtained in the thermal decomposition step is oxidized to form a coating layer containing a platinum group metal oxide. The stabilization treatment can be performed by heating at a temperature higher than the heating temperature in the thermal decomposition step in an atmosphere containing 10 to 25% by mass of oxygen. For example, an atmosphere containing oxygen can be obtained by flowing air through a heating furnace such as a muffle furnace.

In the stabilization step, it is preferable that a diffusion treatment in which the platinum group metal diffuses into the nitride layer is performed simultaneously with an oxidation treatment in which the platinum group metal is oxidized to form a coating layer. Therefore, the heating temperature for the stabilization treatment is a temperature at which the platinum group metal diffuses, and is specifically preferably 650 to 900 ° C. More preferably, it is 700 to 800 ° C. The treatment time varies depending on the temperature and the components of the coating precursor layer, but is preferably 1 to 5 hours. When the temperature is lower than 650 ° C., the platinum group metal does not diffuse, the interlayer strength between the nitride layer 2 and the coating layer 3 is insufficient, and the coating layer 3 may peel off when used under high temperature and high pressure conditions. If it exceeds 900 ° C., a lot of energy is required for heating, which is uneconomical in balance with the degree of diffusion.

In the method for manufacturing a pressure vessel gasket according to the present embodiment, since the coating layer is formed by thermal decomposition, the coating layer may crack and become porous, but a nitride layer is formed on the surface of the substrate. Therefore, the nickel-based alloy of the base material is not exposed, and appropriate hardness and corrosion resistance can be ensured even in a high temperature and high pressure state.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not construed as being limited to the examples.

Example 1
The product name Inconel 625, which is a nickel-based alloy, was processed into a lens ring type pressure vessel gasket shape having an inner dimension of 30 mm, an outer dimension of 50 mm, a maximum thickness of 10 mm, and a minimum thickness of 5 mm as a base material, and surface polishing was performed. . Thereafter, the surface was nitrided in pure nitrogen gas at 1100 ° C. for 3 hours. Here, a nitride layer mainly composed of nickel nitride having a thickness of about 10 μm was formed. Next, iridium chloride was dissolved in amyl alcohol, turpentine oil was further added, and a 0.5 mol-Ir / l solution having a molar concentration in terms of iridium was used as a coating solution. This coating solution was applied on the surface of the obtained nitride layer, and allowed to stand in a dryer at 60 ° C. for 10 minutes to be dried. The coating amount per one time was 10 ml / m ² . This was put into a muffle furnace and heated at 600 ° C. for 10 minutes to perform a thermal decomposition treatment. A coating of a coating precursor layer having an apparent thickness of 2.9 μm made of iridium oxide and iridium metal corresponding to 20 g-Ir / m ² in terms of iridium mass was repeated 10 times from coating of the coating solution to thermal decomposition treatment. Obtained. Furthermore, it put into the muffle furnace which flowed air, it heated at 800 degreeC for 5 hours, the oxidation process and the diffusion process were performed, and the gasket for pressure vessels was produced. The surface of the coating layer was iridium oxide. The apparent thickness of the coating layer was 2.5 μm. In addition, after processing, it was taken out after standing to cool in a furnace. The Vickers hardness of the portion to be a seal portion of the obtained pressure vessel gasket was 350 Hv.

The obtained pressure vessel gasket of Example 1 was brought into close contact with an iridium plate having a thickness of 2 mm, which was assumed to be a flange of the pressure vessel, and was adjusted to 100 t / cm ² using a bolt-nut with a spring washer. Fixed to. When this was held at 700 ° C. and atmospheric pressure for 10 hours and the presence or absence of adhesion due to diffusion was confirmed, adhesion due to diffusion was not recognized.

(Example 2)
As a base material, SUS316L, which is a nickel-based alloy, was processed into a lens ring type pressure vessel gasket shape in the same manner as in Example 1, and surface polishing was performed. Thereafter, the surface was nitrided in ammonia gas at 700 ° C. for 5 hours. Here, a nitride layer mainly composed of nickel nitride and chromium nitride having a thickness of about 10 μm was formed. Next, ruthenium chloride and chloroplatinic acid were prepared in a molar ratio of 3: 1, dissolved in n-butanol, and a solution having a total molar concentration of ruthenium and platinum of 0.3 mol-Ru · Pt / l was prepared. A coating solution was obtained. This coating solution was applied on the surface of the obtained nitride layer, allowed to stand at room temperature (24 ° C.) for 10 minutes, and dried. The coating amount per one time was 0.08 μm. This was put into a muffle furnace and heated at 500 ° C. for 10 minutes to perform a thermal decomposition treatment. The coating precursor having a thickness of 0.8 μm consisting of a mixture of ruthenium platinum oxide corresponding to 12 g-Ru · Pt / m ² in terms of the total mass of ruthenium and platinum is repeated 10 times from coating of the coating solution to thermal decomposition treatment. A layer stack was obtained. Furthermore, it put into the muffle furnace which flowed air, it heated at 750 degreeC for 5 hours, the oxidation process and the diffusion process were performed, and the gasket for pressure vessels was produced. The surface of the coating layer was ruthenium platinum oxide. The thickness of the coating layer was 0.8 μm. In addition, after processing, it was taken out after standing to cool in a furnace. The Vickers hardness of the portion to be a sealed portion of the obtained pressure vessel gasket was 320 Hv. As in Example 1, when the presence or absence of adhesion due to diffusion with the iridium plate was confirmed, adhesion was not confirmed.

(Example 3)
Inconel 625, which is a nickel-based alloy as a base material, is processed into a lens ring type pressure vessel gasket shape in the same manner as in Example 1, polished on the surface, washed with a neutral detergent, and further washed with alcohol. did. Thereafter, the surface was nitrided in a nitrogen-hydrogen mixed gas (80% N ₂ + 20% H ₂ ) under low temperature plasma conditions. The low temperature plasma conditions were maintained at a temperature of 100 ° C. and a gas pressure of 1000 Pa for 3 hours. Here, a nitride layer mainly composed of nickel nitride having a thickness of about 10 μm was formed. Next, iridium nitrate was dissolved in water, and an aqueous solution having a molar concentration in terms of iridium of 0.06 to 0.07 mol-Ir / l was used as a coating solution. This coating solution was applied on the surface of the obtained nitride layer, allowed to stand at room temperature (24 ° C.) for 10 minutes, and dried. The coating amount per one time was 12 to 14 ml / m ² . This was put into a muffle furnace and heated at 500 ° C. for 10 minutes to perform a thermal decomposition treatment. The coating solution coating and thermal decomposition treatment were repeated 12 times to obtain a laminate of a coating precursor layer made of iridium oxide corresponding to 18 g-Ir / m ² in terms of iridium mass and having an apparent thickness of 2.5 μm. Furthermore, it put into the muffle furnace which flowed air, it heated at 700 degreeC for 1 hour, the oxidation process and the diffusion process were performed, and the gasket for pressure vessels was produced. The surface of the coating layer was iridium oxide. The thickness of the coating layer was 2.2 μm. In addition, after processing, it was taken out after standing to cool in a furnace. The Vickers hardness of the portion to be a seal portion of the obtained pressure vessel gasket was 380 Hv. As in Example 1, when the presence or absence of adhesion due to diffusion with the iridium plate was confirmed, adhesion was not confirmed.

Example 4
In Example 1, rhodium chloride was dissolved in amyl alcohol as a coating solution, turpentine oil was added, and a solution having a molar concentration of rhodium of 0.4 mol-Rh / l was used. A gasket for a pressure vessel was produced. The surface of the coating layer was rhodium oxide (Rh ₂ O ₃ ). The Vickers hardness of the portion to be a sealed portion of the obtained pressure vessel gasket was 380 Hv. As in Example 1, when the presence or absence of adhesion due to diffusion with the iridium plate was confirmed, adhesion was not confirmed.

(Example 5)
In Example 1, except that chloroplatinic acid and rhodium chloride were dissolved in amyl alcohol as a coating solution, turpentine oil was further added, and a solution of 0.4 mol-Pt + Rh / l in terms of the combined molar concentration of platinum and rhodium was used. A pressure vessel gasket was prepared according to Example 1. The ratio of platinum to rhodium was 80% by mass of rhodium: 20% by mass of platinum. The surface of the coating layer was platinum and rhodium oxide (Rh ₂ O ₃ ). The Vickers hardness of the portion to be a seal portion of the obtained pressure vessel gasket was 350 Hv. As in Example 1, when the presence or absence of adhesion due to diffusion with the iridium plate was confirmed, adhesion was not confirmed.

(Comparative Example 1)
In Example 1, as a pyrolysis treatment condition, an iridium metal layer containing no oxide was formed as a butane gas burner flame, and a pressure vessel gasket was produced without further oxidation treatment. The surface of the pressure vessel gasket was iridium metal. The thickness of the iridium metal layer was 1 μm. The Vickers hardness of the portion to be a sealed portion of the obtained pressure vessel gasket was 450 Hv. As in Example 1, when the presence or absence of adhesion due to diffusion with the iridium plate was confirmed, adhesion was observed and peeling was difficult.

The gasket for a pressure vessel according to the present invention is suitable as a gasket for sealing a pressure vessel provided with a flange having an opening having a surface of iridium or an iridium base alloy at the opening. In particular, it can be effectively used as a gasket for a pressure vessel used in a hydrothermal synthesis method or a low temperature synthesis method in a supercritical state.

100 Gasket for pressure vessel 1 Base material 2 Nitride layer 3

Cover layer

71, 71a, 71b Gasket 72 Fixing jig 77 Ring 78 Outer ring 81 Body 82 Intermediate layer 83 Inner cylinder 83a Flange mounting portion 84 Lower flange 91 Lid 92 Intermediate layer 93 Inner layer 94 Upper flange 900 Pressure vessel S Seal location

Claims

A gasket for a pressure vessel that is provided in an opening of the pressure vessel and seals the pressure vessel in contact with a flange having a surface of iridium or an iridium-based alloy,
A nickel-base alloy is used as a base material, a nitride layer of the nickel-base alloy is formed on the surface of the base material, and a coating layer containing a platinum group metal oxide is formed on the surface of the nitride layer. Gasket for pressure vessel.
The pressure vessel gasket according to claim 1, wherein the platinum group metal is iridium, ruthenium, rhodium or a base alloy thereof.
3. The thickness of the nitride layer is 1 to 10 μm, and the thickness of the coating layer is 0.01 to 3 μm. Gasket for pressure vessel.
The pressure vessel gasket according to any one of claims 1 to 3, wherein the surface of the seal portion measured according to JIS Z 2244: 2009 has a Vickers hardness of 300 Hv to 400 Hv.
The pressure vessel gasket according to any one of claims 1 to 4, wherein the platinum group metal is diffused from the coating layer into the nitride layer.
A method for producing a gasket for a pressure vessel, which is provided in an opening of the pressure vessel, and a sealing portion is in contact with a flange having a surface of iridium or an iridium base alloy, and seals the pressure vessel,
A nitriding step in which a nickel-based alloy is used as a base material and the surface of the base material is nitrided to form a nitride layer;
A coating step of coating a coating solution containing a platinum group metal compound on the surface of the nitride layer to form a coating layer;
A thermal decomposition step of thermally decomposing the coating layer to form a coating precursor layer;
A stabilization step of heating the coating precursor layer to a coating layer containing an oxide of the platinum group metal in an atmosphere containing oxygen at a temperature higher than the heating temperature of the pyrolysis step;
A method for producing a gasket for a pressure vessel, comprising:
The method of manufacturing a gasket for a pressure vessel according to claim 6, wherein the nitriding step is performed by heating in an atmosphere containing nitrogen gas, ammonia gas or nitrogen-hydrogen mixed gas.
The method for producing a gasket for a pressure vessel according to claim 6 or 7, wherein the coating step and the thermal decomposition step are repeated a plurality of times so that the thickness of the coating layer is 0.01 to 3 µm.