Titanium particles or titanium alloy particles

Abstract

The present invention addresses the problem of providing active metal particles, the surface layer of which is unlikely to undergo oxidation, and a method for producing the same. This active metal particle surface modification method according to the present invention involves generating heat by moving an active metal powder in a fluid, and modifying the surface layer of the active metal particles by reacting said surface layer with an arbitrary component in the fluid by using heat. Said movement is preferably a motion which involves vibrating while moving in a substantially circular trajectory. A vibrating mill is preferably used when moving the active metal powder. As the surface layer thereof, the titanium powder or titanium alloy powder obtained by the surface modification method has a nitrogen-containing film having a thickness within the range of more than 1nm and no more than 6nm. The powder has a fluidity of 25 seconds / 50g to 45 seconds / 50g, inclusive.

Description

[Technical Field]

[0001] The present invention ,blood Titanium particles or titanium alloy particles Regarding do. [Background technology]

[0002] Titanium and titanium alloys have properties such as high specific strength, high corrosion resistance, and excellent biocompatibility, but they suffer from poor machinability and plastic workability, resulting in high processing costs. For this reason, additive manufacturing and injection molding, which can produce metal parts with complex three-dimensional shapes in near-net shape with little need for post-processing, are expected to be effective processing methods for titanium and titanium alloys. As these expectations grow, so too is the demand for titanium powder and titanium alloy powder as raw materials for forming metal parts.

[0003] When active metal powders such as titanium powder or titanium alloy powder are reused in additive manufacturing (AM), the surface layers of the active metal particles in the active metal powder naturally oxidize with each reuse, increasing the oxygen concentration in the surface layers. If the oxygen concentration exceeds a threshold, the active metal powder can no longer be used for AM. Therefore, in order to increase the number of times the active metal powder can be reused, users require active metal powders that contain a large amount of active metal particles with a low oxygen concentration in the surface layers at the time of delivery. Meanwhile, AM typically requires active metal powders with small particle sizes. Generally, the smaller the particle size of the active metal powder, the more susceptible the surface layers of the active metal particles in the active metal powder are to natural oxidation, and the amount of oxygen in the surface layers tends to increase over time. Therefore, there is a need for a technology to suppress the natural oxidation of the surface layers of the active metal particles in active metal powders.

[0004] Furthermore, in injection molding, in order to obtain dense sintered bodies at low temperatures and in a short time, it is necessary to reduce the voids between the active metal particles during molding. To meet this requirement, active metal powders containing fine active metal particles are used. As mentioned above, the smaller the particle size of the active metal powder, the more susceptible the surface layer of the active metal particles in the active metal powder is to natural oxidation, and the amount of oxygen in the surface layer tends to increase over time. For this reason, there is a need for technology to prevent natural oxidation of the surface layer of the active metal particles in the active metal powder used in injection molding. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-183199 Summary of the Invention [Problem to be solved by the invention]

[0006] One method for suppressing natural oxidation of active metal particles in active metal powder is to coat the active metal particles in the active metal powder with a nitride film (see, for example, JP 2019-183199 A). However, the nitrogen content of titanium powder and titanium alloy powder is not specified in JIS standard and ASTM standards, for example, it is set at 300 ppm. Furthermore, in order to maximize the properties of titanium or titanium alloys, the lower the nitrogen content of the active metal particles, the better. Therefore, when titanium particles or titanium alloy particles in titanium powder or titanium alloy powder are coated with a nitride film as described above, the thickness of the nitride film must be kept to the minimum required to effectively inhibit oxidation.

[0007] The object of the present invention is not only to make the surface layer less susceptible to natural oxidation, but also to make it possible to demonstrate the properties of the active metal powder itself compared to conventional materials. Titanium particles or titanium alloy particles The purpose is to provide. [Means for solving the problem]

[0008] The titanium particles or titanium alloy particles according to the present invention have a nitrogen-containing coating as a surface layer. The nitrogen-containing coating has a thickness of more than 1 nm and not more than 6 nm. Therefore, the titanium particles or titanium alloy particles not only have a surface layer that is resistant to natural oxidation, but also can exhibit the properties of the titanium or titanium alloy itself compared to conventional particles.

[0009] The thickness of the nitrogen-containing coating is preferably greater than 1 nm and less than 5 nm, more preferably greater than 1 nm and less than 4 nm, even more preferably greater than 1 nm and less than 3 nm, and particularly preferably greater than 1 nm and less than 2 nm. The nitrogen-containing coating is preferably composed primarily of a compound having a titanium-containing composition or a compound having a titanium alloy composition. The nitrogen-containing coating is particularly preferably composed primarily of titanium nitride or titanium alloy nitride. Examples of titanium nitride include TiN and TiN. For the reasons mentioned above, the nitrogen-containing coating is preferably composed primarily of TiN (TiN and TiN can be identified by X-ray photoelectron spectroscopy (XPS)). The nitrogen-containing coating preferably contains a metal oxide. The sphericity of each particle in the titanium powder or titanium alloy powder is preferably greater than 0.8 and less than 1.0. Furthermore, the titanium powder or titanium alloy powder preferably has a 50% average particle size (median size) in the range of 10 μm to 120 μm, more preferably in the range of 10 μm to 40 μm (the median size can be measured using a particle size distribution analyzer). Titanium powder or titanium alloy powders with a 50% average particle size (median size) in the range of 10 μm to 120 μm exhibit sufficient natural oxidation suppression effects in additive manufacturing and injection molding, while titanium powders with a 50% average particle size (median size) in the range of 10 μm to 40 μm exhibit particularly strong natural oxidation suppression effects. Furthermore, the titanium powder or titanium alloy powder preferably has a fluidity in the range of 25 sec / 50 g to 45 sec / 50 g. Furthermore, the titanium particles or titanium alloy particles according to the present invention preferably exhibit an oxygen increase of 130 ppm or less when heated in air at 60°C for 4 hours.

[0010] By the way, fine titanium powder and fine titanium alloy powder with a particle size of 20 μm or less ignite within 10 seconds in a small gas flame ignition test and continue to burn, so they are classified as Class 2 flammable solids under the Fire Service Act. .thisTherefore, not only are their storage and handling subject to specified quantity restrictions, but also more advanced safety measures are required during their production and handling. However, it has been shown that the above-mentioned titanium powder or titanium alloy powder classified to a particle size of 20 μm (i.e., titanium powder or titanium alloy powder with a particle size of 20 μm or less) does not ignite in a small gas flame ignition test. Therefore, the above-mentioned titanium powder or titanium alloy powder is not subject to the above restrictions, nor does it have to meet the above requirements. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing an example of an EELS line used when measuring the nitride film thickness of titanium alloy particles in titanium alloy powders according to Examples and Comparative Examples. [Figure 2] FIG. 2 is a diagram showing an example of an element concentration profile used when measuring the nitride film thickness in titanium alloy particles in titanium alloy powders according to Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0012] The titanium particles or titanium alloy particles according to the embodiment of the present invention are obtained by a method for surface modification of active metal particles, such as titanium particles or titanium alloy particles. The method for surface modification of active metal particles according to the embodiment of the present invention is a method for surface modification of active metal particles in an active metal powder. The active metal powder referred to here is not particularly limited, but may be, for example, a gas-atomized active metal powder produced by a gas atomization method. Examples of such active metal powders include titanium powder and titanium alloy powder. When the active metal powder is a gas-atomized active metal powder, the gas used in producing the active metal powder must be a rare gas such as argon gas or another inert gas, i.e., a gas that does not substantially react with the surface layer of the active metal particles in the active metal powder. In this method for surface modification of active metal particles, heat is generated by moving the active metal powder in a fluid, and the heat causes the surface layer of the active metal particles in the active metal powder to react with optional components in the fluid, thereby modifying the surface layer. Therefore, by selecting a reactive fluid suitable for forming an oxidation-inhibiting coating, the surface layer of the active metal particles in the active metal powder can be coated with an oxidation-inhibiting coating, making the surface layer less susceptible to natural oxidation. Furthermore, with this method for surface modification of active metal particles, it is possible to form a thinner oxidation-inhibiting coating than conventional methods by controlling factors such as the degree and duration of movement of the active metal powder. Therefore, by utilizing this method for surface modification of active metal particles, it is possible to obtain an active metal powder that not only has a surface layer that is less susceptible to natural oxidation, but also allows the active metal powder to exhibit the properties of the active metal powder itself compared to conventional methods.

[0013] In the surface modification method for active metal particles according to the embodiment of the present invention, the active metal powder may be a pure metal powder or an alloy powder. Examples of the fluid include gas, liquid, and nanoparticles. The fluid may consist of only one component or multiple components. If the fluid consists of multiple components, a diluent component may be included. The motion is not particularly limited as long as it generates heat. Examples of such motion include vibration, reciprocating motion, and motion involving collision. To impart such motion to such active metal powder, a device that imparts speed to the powder, such as a vibration mill, planetary mill, or jet mill, can be used. Among the motions exemplified above, vibration motion is more preferable, and motion that traces a substantially circular orbit while vibrating is particularly preferable. To impart the latter motion to the active metal powder, a vibration mill is preferably used. In a vibration mill, a container containing the active metal powder is subjected to a circular motion while being irradiated with high-frequency waves. This motion causes the active metal particles in the active metal powder to repeatedly collide with each other inside the container, increasing the sphericity of the active metal particles in the active metal powder. By using a vibration mill, such a secondary effect can be achieved. Note that the term "approximately circular orbit" includes a circular orbit and an elliptical orbit that approximates a circle. Furthermore, when the motion involves collisions, a jet mill can be used as a means for achieving such motion. Furthermore, the heat is preferably frictional heat.

[0014] One known surface treatment method for active metal particles involves adding a reactive gas to the atomizing gas. For example, JP 2019-500503 A and JP 2019-516020 A disclose methods of adding an active gas, such as oxygen, to the atomizing gas. However, when a nitride coating is formed on titanium particles in titanium powder using the method disclosed in these publications, the reaction proceeds at temperatures near the melting point of titanium (1668°C), resulting in TiN as the primary component of the nitride coating. TiN is susceptible to degradation, requiring careful handling in downstream processes. Furthermore, in this case, nitrogen atoms easily diffuse into the molten titanium, resulting in an excessively high nitrogen content in the titanium particles in the final titanium powder. Furthermore, when a nitride coating is formed by heat treatment, nitrogen atoms diffuse into the titanium particles during cooling, resulting in an insufficient contribution of the added nitrogen to oxidation suppression. In contrast, in the surface modification method of the present invention, the reactive fluid reacts with the surface layer of the solidified active metal particles at a relatively low temperature, which makes it possible to suppress the internal diffusion of nitrogen. In addition, the main component of the nitride coating is Ti. 2 It is believed that Ti will become N. 2 N is less likely to change in quality in the air, so compared to TiN, no special care is required in handling it in post-processing. 2 Since N has approximately twice the volume per nitrogen atom compared to TiN, a thicker coating can be formed with the same amount of nitrogen. Therefore, the surface modification method of active metal particles according to the embodiment of the present invention can form an oxidation-inhibiting coating that is superior to the oxidation-inhibiting coating obtained by adding a reactive gas to the atomizing gas. Furthermore, in this surface modification method of active metal particles, only the surface layer of the active metal particles in the active metal powder is heated, while the interior of the active metal particles is maintained at a low temperature. Therefore, this surface modification method of active metal particles can suppress the diffusion of nitrogen into the interior of the active metal particles.

[0015] EXAMPLES In the following, examples and comparative examples will be shown to explain the present invention in more detail, but the present invention is not limited to these examples. [Example]

[0016] 1. Preparation of Ti-6Al-4V powder First, Ti-6Al-4V powder (hereinafter referred to as "titanium alloy powder") was prepared by the gas atomization method disclosed in Japanese Patent Laid-Open Publication No. 10-204507. The titanium alloy powder was collected in a mill pot (MB-1, manufactured by Chuo Kakoki Co., Ltd.) with an internal volume of 3.4 L under an argon atmosphere. Next, the atmosphere inside the mill pot was replaced with nitrogen, and the mill pot was placed in a vibration mill (MB-1, manufactured by Chuo Kakoki Co., Ltd.). The vibration mill was operated at a vibration frequency of 1200 rpm for 90 minutes to subject the titanium alloy powder to vibration crushing. The titanium alloy powder after vibration crushing was then classified using sieves with 20 μm and 45 μm openings according to the method described in JIS K 0069 to obtain titanium alloy powder with the target particle size of 20 μm to 45 μm. The titanium alloy powder with a particle size of 20 μm or less was subjected to a small gas flame ignition test.

[0017] 2. Measurement of the physical properties of titanium alloy powder (1) Measurement of oxygen and nitrogen content The oxygen and nitrogen contents of the titanium alloy powder having a particle size of 20 μm-45 μm obtained as described above were measured according to the methods described in JIS H1620 and JIS H 1612, and the oxygen content was found to be 680 ppm and the nitrogen content was 160 ppm.

[0018] (2) Measurement of nitride film thickness (2-1) The titanium alloy powder with particle sizes of 20 μm–45 μm obtained as described above was processed into 100-nm-thick plate-like sections using a focused ion beam (FIB) system. These sections were then placed in a transmission electron microscope (TEM) (JEOL Ltd., JEM-2100F). Electron energy loss spectroscopy (EELS) analysis was performed on a 1,000,000-fold magnification TEM image of the section at 2-nm increments of measurement depth, yielding the EELS traces shown in Figure 1. The elemental concentration profile shown in Figure 2 was then obtained from these EELS traces (note that the elemental concentration profile in Figure 1 is merely an example). As shown in Figure 1, this elemental concentration profile plots the titanium, oxygen, and nitrogen concentrations versus measurement depth (note that the titanium concentration is based on the intensity at 454 eV (Ti-2p), the nitrogen concentration is based on the intensity at 397 eV (N-1s), and the oxygen concentration is based on the intensity at 530 eV (O-1s)). The difference between the two measurement depths corresponding to half of the maximum nitrogen concentration value on the nitrogen concentration curve of this element concentration profile was measured, and this difference was taken as the thickness of the nitride film. The thickness of the nitride film of the titanium alloy particles in this titanium alloy powder was 4 nm. Furthermore, the above element concentration profile revealed that a 4 nm oxide film had formed on the nitride film.

[0019] (3) Flow rate measurement The flowability of the titanium alloy powder having a particle size of 20 μm-45 μm obtained as described above was measured in accordance with "JIS Z2502:2012 Metal powder - Flowability measurement method," and was found to be 31.9 seconds / 50 g.

[0020] (4) Small gas flame ignition test When small gas flame ignition tests (Fire Service Act Class 2 Hazardous Materials Test) were conducted on titanium alloy powders with particle sizes of 20 μm-45 μm and titanium alloy powders with particle sizes of 20 μm or less, none of the titanium alloy powders ignited. [Example]

[0021] 1. Preparation of Ti-6Al-4V powder First, Ti-6Al-4V powder (hereinafter referred to as "titanium alloy powder") was prepared by the gas atomization method disclosed in JP-A-10-204507. The titanium alloy powder was transferred to the mill pot of a vibration mill (FV-20, manufactured by Chuo Kakoki Co., Ltd.) under an argon atmosphere. The atmosphere inside the mill pot was then replaced with argon, and the vibration mill was operated at a frequency of 1200 rpm for 118 minutes. (Note: The temperature was adjusted to maintain a constant temperature throughout the powder to prevent changes in reaction rate due to temperature changes during surface treatment.) Nitrogen gas was then quickly introduced into the mill pot, and the vibration mill was operated again for 2 minutes under the same conditions. The titanium alloy powder in the mill pot was then classified into three fractions of particle sizes of 20 μm-45 μm, 45-105 μm, and 15 μm-52 μm using a sieve according to the method described in JIS K 0069, to obtain the desired titanium alloy powder.

[0022] 2. Measurement of the physical properties of titanium alloy powder (1) Measurement of oxygen and nitrogen content The oxygen and nitrogen contents of the titanium alloy powder having a particle size of 20 μm-45 μm were measured according to the same method as in Example 1, and the oxygen content was found to be 700 ppm and the nitrogen content was found to be 130 ppm.

[0023] (2) Measurement of nitride film thickness According to the same method as that shown in Example 1, the thickness of the nitride film of each of the titanium alloy particles in the titanium alloy powder having a particle size of 20 μm-45 μm, the titanium alloy particles in the titanium alloy powder having a particle size of 45-105 μm, and the titanium alloy particles in the titanium alloy powder having a particle size of 15 μm-52 μm was measured, and the thickness of the nitride film of each of the titanium alloy particles in the titanium alloy powder was 1 nm.

[0024] (3) Flow rate measurement The flowability of the titanium alloy powder having a particle size of 20 μm-45 μm was measured according to the same method as that shown in Example 1, and the flowability was 37.3 seconds / 50 g. [Example]

[0025] 1. Preparation of Ti-6Al-4V powder The target titanium alloy powder was obtained by the same method as that for producing titanium alloy powder shown in Example 2, except that the first operation time of the vibration mill was 30 minutes and the second operation time of the same vibration mill was 5 minutes.

[0026] 2. Measurement of the physical properties of titanium alloy powder (1) Measurement of oxygen and nitrogen content The oxygen and nitrogen contents of the titanium alloy powder having a particle size of 20 μm-45 μm were measured according to the same method as in Example 1, and the oxygen content was 660 ppm and the nitrogen content was 170 ppm.

[0027] (2) Measurement of nitride film thickness The thickness of the nitride film of the titanium alloy particles in the titanium alloy powder having a particle size of 20 μm-45 μm was measured according to the same method as that shown in Example 1, and was found to be 3 nm.

[0028] (3) Flow rate measurement The flowability of titanium alloy powder having a particle size of 20 μm-45 μm was measured according to the same method as that shown in Example 1, and the flowability was 35.3 seconds / 50 g. [Example]

[0029] 1. Preparation of Ti-6Al-4V powder The target titanium alloy powder was obtained by the same production method as the titanium alloy powder production method shown in Example 2, except that the first operation time of the vibration mill was 105 minutes and the second operation time of the same vibration mill was 15 minutes.

[0030] 2. Measurement of the physical properties of titanium alloy powder (1) Measurement of oxygen and nitrogen content The oxygen and nitrogen contents of the titanium alloy powder having a particle size of 20 μm-45 μm were measured according to the same method as in Example 1, and the oxygen content was 690 ppm and the nitrogen content was 250 ppm.

[0031] (2) Measurement of nitride film thickness The thickness of the nitride film of the titanium alloy particles in the titanium alloy powder having a particle size of 20 μm-45 μm was measured according to the same method as that shown in Example 1, and was found to be 6 nm.

[0032] (3) Flow rate measurement The flowability of the titanium alloy powder having a particle size of 20 μm-45 μm was measured according to the same method as that shown in Example 1, and the flowability was 33.3 seconds / 50 g.

[0033] (Comparative Example 1) 1. Preparation of Ti-6Al-4V powder Ti-6Al-4V powder (hereinafter referred to as "titanium alloy powder") was produced by the gas atomization method disclosed in Japanese Patent Laid-Open No. 10-204507, and the obtained titanium alloy powder was classified using sieves with openings of 20 μm and 45 μm according to the method described in JIS K 0069 to obtain titanium alloy powder with the target particle size of 20 μm to 45 μm. The titanium alloy powder with a particle size of 20 μm or less was subjected to a small gas flame ignition test.

[0034] 2. Measurement of the physical properties of titanium alloy powder (1) Measurement of oxygen and nitrogen content The oxygen and nitrogen contents of the titanium alloy powder having a particle size of 20 μm-45 μm were measured according to the same method as in Example 1, and the oxygen content was 790 ppm and the nitrogen content was 30 ppm.

[0035] (2) Measurement of nitride film thickness When the thickness of the nitride film of the titanium alloy particles in the titanium alloy powder having a particle size of 20 μm-45 μm was measured according to the same method as that shown in Example 1, the thickness of the titanium alloy powder was 0 nm.

[0036] (3) Flow rate measurement When the flowability of titanium alloy powder having a particle size of 20 μm-45 μm was measured according to the same method as that shown in Example 1, the titanium alloy powder did not flow.

[0037] (4) Small gas flame ignition test When a small gas flame ignition test (Fire Service Act Class 2 Hazardous Material Test) was carried out on a titanium alloy powder having a particle size of 20 μm or less in accordance with the same method as that shown in Example 1, the titanium alloy powder ignited.

[0038] (Comparative Example 2) 1. Preparation of Ti-6Al-4V powder Ti-6Al-4V powder (hereinafter referred to as "titanium alloy powder") was prepared by the gas atomization method disclosed in Japanese Patent Laid-Open Publication No. 10-204507. The titanium alloy powder was collected in a mill pot (MB-1, manufactured by Chuo Kakoki Co., Ltd.) with an internal volume of 3.4 L under open air conditions. The mill pot was then placed in a vibration mill (MB-1, manufactured by Chuo Kakoki Co., Ltd.), and the vibration mill was operated at a vibration frequency of 1200 rpm for 90 minutes to subject the titanium alloy powder to vibration crushing. The titanium alloy powder after vibration crushing was then classified using sieves with openings of 20 μm and 45 μm according to the method described in JIS K 0069 to obtain titanium alloy powder with the target particle size of 20 μm to 45 μm. The titanium alloy powder with a particle size of 20 μm or less was subjected to a small gas flame ignition test.

[0039] 2. Measurement of the physical properties of titanium alloy powder (1) Measurement of oxygen and nitrogen content The oxygen and nitrogen contents of the titanium alloy powder having a particle size of 20 μm-45 μm were measured according to the same method as in Example 1, and the oxygen content was 1080 ppm and the nitrogen content was 50 ppm.

[0040] (2) Measurement of nitride film thickness When the thickness of the nitride film of the titanium particles in the titanium alloy powder having a particle size of 20 μm-45 μm was measured according to the same method as that shown in Example 1, the thickness of the nitride film was 0 nm.

[0041] (3) Flow rate measurement The flowability of the titanium alloy powder having a particle size of 20 μm-45 μm was measured according to the same method as that shown in Example 1, and the flowability was 32.4 seconds / 50 g.

[0042] (4) Small gas flame ignition test When a small gas flame ignition test (Fire Service Act Class 2 Hazardous Material Test) was carried out on a titanium alloy powder having a particle size of 20 μm or less in accordance with the same method as that shown in Example 1, the titanium alloy powder ignited.

[0043] The results obtained in Examples 1-4 and Comparative Examples 1-3 above are summarized in Table 1 below.

[0044] [Table 1] [Example]

[0045] The titanium alloy powder produced in Example 3 and the titanium alloy powder produced in Comparative Example 2 were each heated at 60°C for 4 hours to examine the oxidation prevention effect of the nitride film. As a result, the oxygen content of the titanium alloy powder produced in Comparative Example 2 increased by 160 ppm, whereas the oxygen content of the titanium alloy powder produced in Example 3 increased by only 130 ppm, a 20% decrease in the increase in oxygen compared to the titanium alloy powder produced in Comparative Example 2. From these results, it is expected that the formation of a nitride film is effective in suppressing the oxidation of titanium alloy powder and can effectively suppress the increase in oxygen content during recycling of titanium alloy powder used in additive manufacturing.

[0046] (summary) As is clear from Table 1, the titanium alloy powders according to Examples 1-4 have a higher nitrogen content than the titanium alloy powders according to Comparative Examples 1 and 2, and the titanium alloy particles are covered with a nitride film several nanometers thick. Therefore, the titanium alloy powders according to Examples 1-4 are less susceptible to oxidation. The titanium alloy powders according to Examples 1-4 contain approximately 650-700 ppm of oxygen. This is believed to be due to the combination of the 400 ppm of oxygen originally present in the titanium alloy powder and the 300 ppm of oxygen added as an oxide film. Furthermore, the 20 μm-45 μm titanium alloy powders according to Examples 1-4 exhibit high fluidity and are suitable for additive manufacturing. Furthermore, the titanium alloy powders according to Examples 1-4 do not ignite in a small gas flame ignition test (Fire Service Act, Class 2 Hazardous Materials Test) even when the particle size is 20 μm or less. Therefore, the titanium alloy powders according to Examples 1-4 can be handled with normal care. The titanium alloy powders according to Examples 1 to 4 have all of the above properties and have never existed before.

[0047] The thickness of the nitride film of each of the titanium alloy powders according to Examples 1-4 is almost equal to the theoretical value calculated from the following formula (I), and is about twice the theoretical value calculated from the following formula (II). Therefore, it is presumed that the nitride film of each of the titanium alloy powders according to Examples 1-4 is mainly composed of TiN.

[0048] d=1 / 3 ΔC N (d 50 / 2) (M Ti2N / M N ) (ρ Ti / ρ Ti2N ) (I)

[0049] d=1 / 3 ΔC N (d 50 / 2) (M TiN / M N ) (ρ Ti / ρ TiN ) (II)

[0050] In the two equations (I) and (II), "d" is the thickness of the nitride film, and "ΔC N" is the increase in nitrogen content compared to the untreated powder, and "d 50 " is the median diameter (50% particle size) of the titanium alloy powder, and "M Ti2N " is the molecular weight of TiN, and "M TiN " is the molecular weight of TiN, and "M N " is the atomic weight of N, and "ρ Ti " is the density of Ti, and "ρ Ti2N " is the density of Ti2N, and "ρ TiN " is the density of TiN.

Claims

1. A nitrogen-containing coating having a thickness of more than 1 nm and not more than 6 nm is provided as a surface layer, The nitrogen-containing coating is Ti ２ N is the main component Titanium particles or titanium alloy particles.

2. The nitrogen-containing coating contains a metal oxide.

2. The titanium or titanium alloy particles according to claim 1.

3. The flow rate is in the range of 25 seconds / 50g or more and 45 seconds / 50g or less.

3. Titanium particles or titanium alloy particles according to claim 1 or 2.

4. The sphericity is in the range of 0.8 to 1.

0.

4. Titanium particles or titanium alloy particles according to claim 3.

5. When heated in air at 60°C for 4 hours, the increase in oxygen is 130 ppm or less.

5. Titanium particles or titanium alloy particles according to any one of claims 1 to 4.

6. The 50% average particle size (median size) is in the range of 15 μm to 40 μm.

6. Titanium particles or titanium alloy particles according to any one of claims 1 to 5.

7. The 50% average particle size (median size) is in the range of 15 μm or more and 20 μm or less.

7. Titanium particles or titanium alloy particles according to claim 6.

Images