Titanium alloy for supercritical water utilization equipment

Abstract

The present invention provides a Ti-O-based material in which the Ti-O-based material containing oxygen as a chemical component is used as a material constituting a device for handling supercritical water to reduce refining cost. The Ti-O-based material according to an embodiment of the present invention contains oxygen as a chemical component, wherein the oxygen content is 0.05 mass% to 3.0 mass% with the remainder being made up by titanium and unavoidable impurities, and in a supercritical water oxidation test carried out by placing a crucible containing a sample of the Ti-O-based material or a sample of pure titanium and an empty crucible that does not contain a sample in a reactor, the weight increase per unit area of the sample of the Ti-O-based material after the test is equal to or smaller than the weight increase per unit area of the sample of the pure titanium.

Description

[Technical Field]

[0001] The present invention relates to an apparatus for handling supercritical water, and more particularly to a corrosion-resistant metallic material, in particular a titanium alloy, applicable to an apparatus for handling supercritical water. [Background technology]

[0002] Technologies for handling supercritical water are being developed in various fields, such as the decomposition of harmful organic substances like dioxins, PCBs, and CFCs, and the creation of high-temperature and high-pressure steam conditions for power generation turbines in thermal power plants. Supercritical water is water under high temperature and high pressure conditions, such as temperatures above 374.15°C and pressures above 22.12 MPa, and its properties differ from those of water or water vapor at atmospheric pressure. Therefore, the oxidation and corrosion phenomena of metal materials caused by supercritical water may differ from those caused by water or water vapor. Accordingly, the components of equipment that handles supercritical water (hereinafter also referred to as supercritical water utilization equipment) need to have high corrosion resistance to supercritical water.

[0003] Patent Document 1 discloses the use of pure titanium specified in JIS Grade 1 to 3, or pure titanium specified in ASTM Grade 1 to Grade 4, as materials for the containers and piping of supercritical water utilization equipment. However, these pure titaniums are only permitted to have a maximum dissolved oxygen content of 0.4 mass% (ASTM Grade 4). Furthermore, even pure titanium specified in JIS Grade 4 is limited to a dissolved oxygen content of 0.4 mass% or less. Reducing the dissolved oxygen content from titanium oxide contained in raw ore and scrap titanium to the above permitted values ​​requires advanced refining methods such as the Chroll process, making the production of pure titanium time-consuming and costly.

[0004] On the other hand, in recent years, research has been conducted on reducing refining costs in titanium alloy materials by effectively utilizing oxygen as an alloying element. For example, Patent Document 2 discloses a titanium-oxygen-based material (Ti-O-based material) containing 0.05 mass% to 0.9 mass% oxygen, in which ductility and strength are improved by controlling the texture after rolling. However, Patent Document 2 does not provide any indication regarding the corrosion resistance of rolled sheets of this Ti-O-based material. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2002-361069 [Patent Document 2] Japanese Patent Publication No. 2019-151893 [Overview of the project] [Problems that the invention aims to solve]

[0006] The present invention aims to expand the potential of Ti-O-based materials by reducing refining costs, by utilizing Ti-O-based materials containing oxygen as a chemical component as materials for equipment that handles supercritical water. [Means for solving the problem]

[0007] The Ti-O-based material of the present invention is a Ti-O-based material containing oxygen as a chemical component, wherein the oxygen content is 0.05% by mass or more and 3.0% by mass or less, with the remainder being titanium and unavoidable impurities. In a supercritical water oxidation test conducted by placing a crucible containing a sample made of the Ti-O-based material or a sample made of pure titanium and an empty crucible without a sample in a reactor, the weight increase per unit area of ​​the sample made of the Ti-O-based material after the test is less than or equal to the weight increase per unit area of ​​the sample made of pure titanium, thereby achieving the above objective.

[0008] In the case of the above-mentioned Ti-O-based material, it is preferable that the thickness of the oxide film of the sample made of the above-mentioned Ti-O-based material, as measured from a scanning electron microscope (SEM) image of the cross-section of the sample after the above-mentioned supercritical water oxidation test, is less than or equal to the thickness of the oxide film of the sample made of the above-mentioned pure titanium.

[0009] The above Ti-O-based material preferably has an oxygen content of more than 0.4% by mass and 2.0% by mass or less.

[0010] Furthermore, it is more preferable that the above-mentioned Ti-O-based material has an oxygen content of 1.0% by mass or more and 2.0% by mass or less.

[0011] The above supercritical water oxidation test is, The test conditions involve placing a crucible containing a sample made of the above-mentioned Ti-O-based material or a sample made of pure titanium, and an empty crucible inside a reactor, into which pure water adjusted to have a dissolved oxygen content of 0.01 mg / L or less and an electrical conductivity of 0.08 mS / cm or less is injected. The reactor is then heated to 500°C in an electric furnace, and the reactor is pressurized to a range of 22.12 MPa to 23 MPa using a high-pressure metering pump to create a supercritical state, and the sample contained in the crucible inside the reactor is exposed to the supercritical water for 50.0 hours or more. The above-mentioned pure titanium is defined by JIS or ASTM standards, and is preferably selected from the group consisting of JIS Grade 1 to 4 and ASTM Grade 1 to Grade 4.

[0012] The weight increment per unit area of ​​the above-mentioned Ti-O-based material sample and the above-mentioned pure titanium sample was calculated by roughly polishing the entire surface of the sample to be subjected to the supercritical water oxidation test with waterproof abrasive paper, adjusting all samples to have a similar surface roughness, measuring the length, width, and thickness of each sample to the nearest 1 μm using a micrometer, and calculating the total surface area of ​​each sample. After degreasing and washing the samples, each sample is placed in a crucible, dried in a drying oven, and then the weight of each sample, including the crucible, is weighed to the nearest 0.1 mg using an electronic balance. The empty crucible, dried in a dryer, is weighed to the nearest 0.1 mg using an electronic balance. After the test, the crucible containing the sample and the empty crucible are weighed with an electronic balance to the nearest 0.1 mg, it is preferably calculated by dividing, by the total surface area of each sample, a value obtained by subtracting the weight increment of the empty crucible from the weight difference of each sample weighed together with the crucible before and after the test.

[0013] The Ti-O-based material may be produced by a method selected from the group consisting of casting, additive manufacturing, sintering, rolling, forging, drawing and extrusion. The Ti-O-based material may be a cast material, an additive manufactured material or a sintered material, and among these, a cast material is preferable.

[0014] In one aspect of the present invention, a supercritical water utilization apparatus using the Ti-O-based material is provided.

[0015] Further, in another aspect of the present invention, a cast material for a supercritical water utilization apparatus using the Ti-O-based material is provided.

[0016] Further, in another aspect of the present invention, use of the Ti-O-based material in a supercritical water utilization apparatus is provided.

Effects of the Invention

[0017] According to the present invention, a Ti-O-based material that effectively utilizes oxygen, which has been recognized as a harmful component in terms of corrosion resistance in conventional titanium alloy materials, as an alloying element and reduces refining cost can be used as a material for an apparatus that handles supercritical water.

Brief Description of Drawings

[0018] [Figure 1] It is a figure showing SEM images of cross sections of respective test pieces after a supercritical water oxidation test for Test 1 of Examples. (a) Ti-0.05%O, (b) Ti-1.0%O, (c) Ti-2.0%O, (d) Ti-3.0%O, (e) Ti-4.0%O, (f) Ti-5.0%O

Mode for Carrying Out the Invention

[0019] First, the properties of the Ti-O-based material of the present invention will be described.

[0020] The Ti-O-based material of the present invention is a Ti-O-based material containing oxygen as a chemical component, and in a supercritical water oxidation test conducted by placing a crucible containing a sample made of the Ti-O-based material or a sample made of pure titanium and an empty crucible without a sample in a reactor, the weight increase per unit area of ​​the sample made of the Ti-O-based material after the test is less than or equal to the weight increase per unit area of ​​the sample made of pure titanium.

[0021] The pure titanium used in the supercritical water oxidation test is specified by JIS or ASTM standards, and is preferably selected from the group consisting of JIS Grade 1 to 4 and ASTM Grade 1 to Grade 4. The Ti-O-based material of the present invention has corrosion resistance to supercritical water comparable to, or even better than, pure titanium specified by JIS or ASTM standards, and is therefore suitable for use as a component in supercritical water utilization equipment.

[0022] Furthermore, it is preferable that the thickness of the oxide film of a sample made of the Ti-O-based material, as measured from a scanning electron microscope (SEM) image of the cross-section of the sample after the supercritical water oxidation test, is less than or equal to the thickness of the oxide film of a sample made of pure titanium. A Ti-O-based material that satisfies both the weight increment per unit area of ​​the sample after the test and the thickness of the oxide film is more suitable for use as a component of a supercritical water utilization device.

[0023] In this invention, the thickness of the oxide film on a sample made of Ti-O-based material and a sample made of pure titanium after a supercritical water oxidation test is the average value of the oxide film thickness measured from three or more different fields of view in a scanning electron microscope (SEM) image of the cross-section of the sample.

[0024] The above supercritical oxidation test can be conducted using any test apparatus and test conditions, provided that at least a sample made of the target Ti-O-based material or a sample made of pure titanium can be exposed to supercritical water for a certain period of time in a crucible installed in the reactor. Specific test examples will be described in the embodiments described later, but preferred embodiments include, for example, the following. - A reactor is fitted with a crucible containing a sample made of the target Ti-O-based material or a sample made of pure titanium, and an empty crucible. Pure water, adjusted to have a dissolved oxygen content of 0.01 mg / L or less and an electrical conductivity of 0.08 mS / cm or less, is injected into the reactor. The reactor is heated to 500°C in an electric furnace, and the reactor is pressurized to a range of 22.12 MPa to 23 MPa using a high-pressure metering pump to create a supercritical state. The sample contained in the crucible inside the reactor is then exposed to the supercritical water for a certain period of time.

[0025] There are no particular restrictions on the time for which the sample contained in the crucible in the reactor is exposed to supercritical water; for example, it may be 50.0 hours or longer. Furthermore, depending on the characteristics of the supercritical water utilization apparatus to which the target Ti-O-based material is applied, a time condition of less than 50.0 hours may be set. In the examples described later, as representative examples, test examples in which the sample contained in the crucible in the reactor is exposed to supercritical water for 50.0 hours, 25.0 hours, and 1.75 hours will be described.

[0026] In the supercritical oxidation test described above, the sample made of the target Ti-O-based material or pure titanium is exposed to supercritical water for a certain period of time in a crucible placed inside the reactor. Furthermore, since the process of achieving the supercritical state in this test inevitably passes through the subcritical region, the sample used in the test is exposed to subcritical water for a certain period of time. Moreover, by heating and pressurizing water at room temperature and pressure, the sample used in the test is also exposed to water or steam at a certain high temperature and pressure for a certain period of time.

[0027] Therefore, the Ti-O-based material of the present invention may possess not only corrosion resistance to supercritical water, more specifically, corrosion resistance to supercritical water at temperatures between 374.15°C and 500°C and pressures between 22.12 MPa and 23 MPa, but also corrosion resistance to water in the subcritical region adjacent to the supercritical region (i.e., subcritical water), or to water or water vapor under temperature and pressure conditions higher than normal temperature and pressure.

[0028] The Ti-O-based material of the present invention, possessing these characteristics, can be useful not only as a component of a supercritical water utilization device, but also as a component of a device that handles subcritical water, and as a component of a device that handles water or steam under temperature and pressure conditions higher than normal temperature and pressure. Therefore, it is expected that the potential uses of Ti-O-based materials with reduced refining costs will be further expanded.

[0029] Next, the component composition of the Ti-O-based material of the present invention will be described.

[0030] The Ti-O-based material of the present invention contains a certain amount of oxygen (O) as a chemical component, with the remainder consisting of titanium and unavoidable impurities.

[0031] From the standpoint of reducing refining costs, a higher oxygen content (solid-dissolved oxygen content) is desirable, but excessive oxygen content may impair corrosion resistance to supercritical water. Furthermore, in the Ti-O-based material of the present invention, the oxygen content may be 0.4 mass% or less, which corresponds to pure titanium as defined by JIS or ASTM standards, but excessively low oxygen content may be undesirable in practical terms in terms of the effort and cost of material production. In other words, as mentioned above, the solid-dissolved oxygen content of pure titanium as defined by JIS or ASTM standards is up to 0.4 mass% (JIS Grade 4, ASTM Grade 4), but in the Ti-O-based material of the present invention, the oxygen content may exceed 0.4 mass%.

[0032] Based on the above, in the present invention, the oxygen content is 0.01% by mass or more and 10.0% by mass or less, preferably 0.03% by mass or more and 7.5% by mass or less, more preferably 0.05% by mass or more and 5.0% by mass or less, even more preferably 0.05% by mass or more and 3.0% by mass or less, even more preferably more than 0.4% by mass and 2.0% by mass or less, and even more preferably 1.0% by mass or more and 2.0% by mass or less.

[0033] The Ti-O-based material of the present invention having such a component composition can be manufactured using conventional methods for manufacturing and processing metal materials. Applicable manufacturing and processing methods for the Ti-O-based material of the present invention include, but are not limited to, casting, additive manufacturing, sintering, rolling, forging, drawing, and extrusion. Among these, from a practical standpoint, casting, additive manufacturing, and sintering are preferred, and casting is more preferred. For example, the Ti-O-based material according to one embodiment of the present invention is manufactured using a casting method, thereby producing the Ti-O-based material of the present invention as a cast material, and this cast material can be used to produce a cast material for a supercritical water utilization device. These cast materials can then be suitably used as components constituting the supercritical water utilization device.

[0034] The present invention will be described in more detail below based on examples. The apparatus configuration, measurement conditions, etc., shown in the following embodiments can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the embodiments shown below. [Examples]

[0035] [Test 1] Six types of Ti-O-based material ingots were melted down, each containing 0.05%, 1.0%, 2.0%, 3.0%, 4.0%, and 5.0% oxygen by mass, with the remainder being titanium and unavoidable impurities. In the following, to distinguish each Ti-O-based material, they will also be referred to as Ti-0.05%O, Ti-1.0%O, Ti-2.0%O, Ti-3.0%O, Ti-4.0%O, and Ti-5.0%O, according to their oxygen content.

[0036] Next, strip-shaped test pieces measuring 20 mm in length, 10 mm in width, and 2 mm in thickness were cut from these ingots to be used as samples for supercritical hydroxide oxidation tests. The entire surface of each test piece was roughly polished with waterproof abrasive paper to ensure that all test pieces had a similar surface roughness. Subsequently, the length, width, and thickness of each test piece were measured to the nearest 1 μm using a micrometer, and the total surface area of ​​each test piece was calculated.

[0037] After degreasing and washing the test specimens, each specimen was placed individually in an alumina crucible measuring 26 mm in diameter and 19 mm in depth, and dried in a drying oven. Then, the weight of each test specimen, including the crucible, was weighed to the nearest 0.1 mg using an electronic balance.

[0038] Furthermore, in order to measure the weight increase due to the oxidation of the crucible itself, empty crucibles without test specimens were dried in a dryer and weighed to the nearest 0.1 mg using an electronic balance.

[0039] A 2.8L reactor made of Hastelloy C276 was placed inside a crucible containing a test specimen and an empty crucible. Pure water, adjusted to have a dissolved oxygen content of 0.01 mg / L or less and an electrical conductivity of 0.08 mS / cm or less, was injected. The reactor was then heated to 500°C in an electric furnace, and the reactor was pressurized to approximately 23 MPa using a high-pressure metering pump to achieve a supercritical state.

[0040] After exposing the test specimens, placed in crucibles within the reactor, to supercritical water for 50.0 hours, the reactor was cooled and depressurized, and the gas was replaced with argon. Then, the crucibles containing the test specimens and the empty crucibles were removed and weighed to the nearest 0.1 mg using an electronic balance.

[0041] The weight increase per unit area was calculated by subtracting the weight increase of the empty crucible from the weight difference of each test specimen, which was weighed with the crucible before and after the above test, and then dividing the result by the total surface area of ​​each test specimen.

[0042] As a result, the weight increment per unit area of ​​each test specimen was 16.55 μg / mm². 2(Ti-0.05%O), 15.37 μg / mm³ 2 (Ti-1.0%O), 14.03 μg / mm³ 2 (Ti-2.0%O), 16.55 μg / mm³ 2 (Ti-3.0%O), 38.29 μg / mm³ 2 (Ti-4.0%O), and 62.65 μg / mm³ 2 The result was (Ti-5.0%O). Here, Ti-0.05%O is pure titanium equivalent to JIS Grade 1 or ASTM Grade 1 based on its oxygen content. Therefore, from the above results, it was confirmed that for Ti-O-based materials with an oxygen content of 0.05 mass% to 3.0 mass%, the weight increase per unit area of ​​the test specimen after the supercritical hydroxide oxidation test was less than or equal to the weight increase per unit area of ​​the test specimen made of pure titanium.

[0043] Furthermore, each test specimen after the above tests was subjected to tissue observation (analysis) using an optical microscope, SEM / EDX (scanning electron microscope / energy dispersive X-ray analyzer), and XRD (X-ray diffractometer).

[0044] Figures 1(a) to 1(f) show SEM images of cross-sections of specimens after supercritical water oxidation testing for Ti-0.05%O, Ti-1.0%O, Ti-2.0%O, Ti-3.0%O, Ti-4.0%O, and Ti-5.0%O, respectively. The scale bar in Figure 1(a) is 4 μm, and the same magnification is used for Figures 1(b) to 1(f). In Figures 1(a) to 1(f), for clarity, the approximate range of the oxide film is indicated by double-headed arrows.

[0045] The oxide film thickness of each specimen (average value from a total of three fields of view), measured from two different fields of view of the SEM images in Figures 1(a) to (f) and the cross-section of each specimen, was 10.3 μm (Ti-0.05%O), 9.02 μm (Ti-1.0%O), 10.3 μm (Ti-2.0%O), 11.6 μm (Ti-3.0%O), 20.1 μm (Ti-4.0%O), and 17.1 μm (Ti-5.0%O). From this, it was confirmed that for Ti-O-based materials with an oxygen content of 0.05% by mass or more and 2.0% by mass or less, the weight increase per unit area of ​​the test specimen after the supercritical hydroxide oxidation test is less than or equal to the weight increase per unit area of ​​the test specimen made of pure titanium, and the thickness of the oxide film on the test specimen after the supercritical hydroxide oxidation test is less than or equal to the thickness of the oxide film on the test specimen made of pure titanium.

[0046] These results indicate that titanium-oxygen alloy materials containing a certain amount of oxygen as an alloying element can possess corrosion resistance to supercritical water, and that this corrosion resistance may be comparable to, or even superior to, that of pure titanium as defined by JIS or ASTM standards. This means that not only Ti-O alloy materials with an oxygen content similar to that of pure titanium, but also Ti-O alloy materials exceeding the upper limit of 0.4 mass% for dissolved oxygen content defined by JIS or ASTM standards for pure titanium, can be used as components in supercritical water utilization equipment.

[0047] [Exam 2] Next, supercritical water oxidation tests were conducted on two types of Ti-O-based materials (Ti-0.05%O and Ti-1.0%O) using the same procedure as in Test 1 above, except that the test specimens placed in the crucible inside the reactor were exposed to supercritical water for 25.0 hours. For comparison, similar supercritical water oxidation tests were also conducted on 9Cr steel (ASME SA-387 / SA-387M Grade 91 (chromium-molybdenum steel sheet for boilers and pressure vessels)) and carbon steel (SPCC; steel grade specified in JIS G 3141 (cold-rolled steel sheet and strip)).

[0048] After the above test, the weight increment per unit area of the test piece was 11.09 μg / mm 2 (Ti-0.05%O) and 7.85 μg / mm 2 (Ti-1.0%O). Compared with Ti-0.05%O, Ti-1.0%O had a smaller weight increment per unit area of the test piece after the supercritical water oxidation test. Further, for 9Cr steel and carbon steel, the weight increment per unit area was 15 μg / mm 2 or more and 30 μg / mm 2 or more, respectively. The results obtained for Ti-0.05%O and Ti-1.0%O were significantly smaller than those for 9Cr steel, which is known as a heat-resistant steel, and the difference from carbon steel was clear.

[0049] From these results, it was suggested that by adjusting the oxygen content in a titanium-oxygen-based material containing a certain amount of oxygen as an alloying element, the material is useful as a member exposed to supercritical water under a time condition shorter than 50.0 hours.

[0050] [Test 3] Next, a supercritical water oxidation test was performed on two types of Ti-O-based materials (Ti-0.05%O and Ti-1.0%O) by the same procedure as in the above Test 1, except that the test piece housed in a crucible inside the reactor was exposed to supercritical water for 1.75 hours.

[0051] After the above test, the weight increment per unit area of the test piece was 5.69 μg / mm 2 (Ti-0.05%O) and 4.24 μg / mm 2 (Ti-1.0%O). Compared with Ti-0.05%O, Ti-1.0%O had a smaller weight increment per unit area of the test piece after the supercritical water oxidation test.

[0052] From this result, it was suggested that by adjusting the oxygen content in a titanium-oxygen-based material containing a certain amount of oxygen as an alloying element, the material is useful as a member exposed to supercritical water under a time condition of about 2.0 hours.

Industrial Applicability

[0053] According to the present invention, by effectively utilizing oxygen, which was previously recognized as a harmful component in terms of corrosion resistance in conventional titanium alloy materials, as an alloying element, and thereby reducing refining costs, Ti-O-based materials can be used as materials for equipment that handles supercritical water. This makes it possible to provide materials for supercritical water utilization equipment at a low cost, and is expected to expand the industrial potential of supercritical water.

Claims

1. A Ti-O-based material for supercritical water utilization equipment, containing oxygen as a chemical component, The oxygen content is greater than 0.4% by mass and less than or equal to 3.0% by mass, with the remainder consisting of titanium and unavoidable impurities. In a supercritical water oxidation test conducted by placing a crucible containing a sample made of the Ti-O-based material and a crucible containing a sample made of pure titanium inside a reactor, the weight increase per unit area of ​​the sample made of the Ti-O-based material after the test is less than or equal to the weight increase per unit area of ​​the sample made of pure titanium. Ti-O material for supercritical water utilization equipment.

2. The thickness of the oxide film on the sample made of the Ti-O-based material, as measured from a scanning electron microscope (SEM) image of the cross-section of the sample after the supercritical water oxidation test, is less than or equal to the thickness of the oxide film on the sample made of pure titanium. The Ti-O-based material for a supercritical water utilization apparatus according to claim 1.

3. The Ti-O-based material for a supercritical water utilization device according to claim 2, wherein the oxygen content is greater than 0.4% by mass and less than or equal to 2.0% by mass.

4. The Ti-O-based material for a supercritical water utilization device according to claim 3, wherein the oxygen content is 1.0% by mass or more and 2.0% by mass or less.

5. The Ti-O-based material for a supercritical water utilization apparatus according to Claim 1, wherein an empty crucible not containing a sample is placed inside the reactor in the supercritical water oxidation test.

6. The supercritical water oxidation test described above is The test conditions involve placing a crucible containing a sample made of the Ti-O-based material, a crucible containing a sample made of pure titanium, and an empty crucible inside a reactor, injecting pure water adjusted to have a dissolved oxygen content of 0.01 mg / L or less and an electrical conductivity of 0.08 mS / cm or less, heating the reactor to 500°C in an electric furnace, and pressurizing the reactor to a range of 22.12 MPa to 23 MPa using a high-pressure metering pump to create a supercritical state, and exposing the sample contained in the crucibles inside the reactor to the supercritical water for 50.0 hours or more. The aforementioned pure titanium is defined by JIS or ASTM standards and is selected from the group consisting of JIS Grade 1 to 4 and ASTM Grade 1 to 4. The Ti-O-based material for a supercritical water utilization apparatus according to claim 5.

7. The weight increment per unit area of ​​the sample made of the Ti-O-based material and the sample made of pure titanium is, The entire surface of the samples to be subjected to the supercritical water oxidation test was roughly polished with waterproof abrasive paper, and after adjusting all samples to have a similar surface roughness, the length, width, and thickness of each sample were measured to the nearest 1 μm using a micrometer, and the total surface area of ​​each sample was calculated. After degreasing and washing the samples, each sample is placed in a crucible, dried in a drying oven, and then the weight of each sample, including the crucible, is weighed to the nearest 0.1 mg using an electronic balance. The empty crucible, dried in a dryer, is weighed to the nearest 0.1 mg using an electronic balance. After the test, weigh the crucible containing the sample and the empty crucible to the nearest 0.1 mg using an electronic balance. The difference in weight of each sample, measured with the crucible before and after the test, minus the weight increase due to the empty crucible, is calculated by dividing this difference by the total surface area of ​​each sample. The Ti-O-based material for a supercritical water utilization apparatus according to claim 5.

8. A Ti-O-based material for a supercritical water utilization device according to any one of claims 1 to 7, which is a cast material.

9. A supercritical water utilization apparatus using a Ti-O-based material for supercritical water utilization apparatus according to any one of claims 1 to 8.

10. A component for a supercritical water utilization apparatus using the Ti-O-based material for supercritical water utilization apparatus as described in claim 8.

11. Use of the Ti-O-based material for supercritical water utilization apparatus according to any one of claims 1 to 8 in a supercritical water utilization apparatus.

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