TWI727414B - Alloy powder composition - Google Patents

Abstract

The present invention relates to an alloy powder composition containing: an alloy powder; 0.005 mass% or more and 0.200 mass% or less of fluidity-improving particles; and 0.5 mass% or more and 1.5 mass% or less of lubricant, in which the alloy powder is made of austenitic stainless steel and has a 50% diameter D₅₀ of 20 μm or more and 30 μm or less, and in which the fluidity-improving particles are made of at least one metal oxide selected from the group consisting of Al₂O₃, MgO, ZrO₂, Y₂O₃, CaO, SiO₂, and TiO₂, have a 50% diameter D₅₀ of 5 nm or more and 35 nm or less, and have a hydrophobic surface.

Description

Alloy powder composition

The present invention relates to an alloy powder composition, and more specifically, to an alloy powder composition suitable for manufacturing high-density sintered components made of austenitic stainless steel.

"Press-molding method" refers to the process of mixing lubricant into alloy powder of stainless steel, iron, copper or the like, filling the alloy powder into the mold, and pressing the alloy powder into a sintering furnace. A method of heat-treating the molded body to obtain sintered components The press molding method can produce complex and highly accurate machine components with high productivity. Therefore, sintered components are widely used in fields such as electricity, machinery, and automobiles.

In the case of manufacturing a sintered component by using a compression molding method, when the alloy powder has a smaller particle size, the sintered component has a higher density. However, when the alloy powder has a smaller particle size, the alloy powder has low fluidity, which makes it difficult to fill the alloy powder into the mold. On the other hand, it is known that metal injection molding (MIM) methods, granulation methods, and similar methods are techniques for obtaining high-density sintered components, but these methods cannot be applied to applications that require low prices due to their high process costs. (For example, automotive applications).

In order to solve the aforementioned problems, conventional technologies have made various proposals.

For example, Patent Document 1 discloses a mixed powder for high-density sintered body Finally, Fe-B powder is blended into the main powder made of austenitic stainless steel.

Patent Document 1 states that (a) because Fe has a smaller diffusion coefficient in austenitic iron than that in ferrous iron, austenitic stainless steel is difficult to use sintering reaction; and (b) when it is combined with austenitic stainless steel When the secondary powder (for example, Fe-B powder) that causes the eutectic reaction in the main powder is added to the main powder, a liquid phase is formed in the gaps of the main powder, and local liquid phase sintering occurs to increase the sintered density of the sintered body.

Patent Document 2 discloses a powder composition for metallurgy, which contains 85% by weight or more of iron-based metal powder, 0.005% to 3% by weight of binder, 0.1% to 2% by weight of lubricant, and 0.005% by weight % To 2% by weight of particulate silica with an average particle size of less than 40nm.

Patent Document 2 states that (a) when particulate silica is blended into iron-based metal powder as a fluidizing agent, the fluidity of the powder composition increases; (b) when a lubricant is added to the iron-based metal powder, The ejection force required to remove the molded component from the mold cavity can be reduced; and (c) the fluidizing agent also acts as an internal lubricant during the molding process.

In order to efficiently mass-produce sintered components using the compression molding method, it is necessary to fill the mold with alloy powder with high efficiency. Therefore, the alloy powder used for sintering components needs to have high fluidity. In order to obtain high fluidity, alloy powders having an average particle size of about 60 μm are generally used to manufacture sintered components.

However, in the case of using austenitic stainless steel powder with an average particle size of about 60μm ^{to manufacture a sintered component under a general compaction pressure (about 7t/cm 2} ), the sintered density is about 86%, and it cannot be maintained. High sintered density (91% or above) required for air tightness. In addition, since the porosity is about 14%, corrosion resistance, hardness, and strength are insufficient.

On the other hand, due to the high sinterability of ferrous iron stainless steel, even Under the general manufacturing conditions of high productivity, high sintered density can also be achieved fairly easily by ferrite stainless steel. However, due to the poor heat resistance of the fat iron stainless steel, sintered components made of the fat iron stainless steel are still used in exhaust system components or the like at low temperature parts.

In order to manufacture sintered components with excellent heat resistance and airtightness at low cost, an alloy containing austenitic stainless steel as the main component, excellent fluidity and sinterability, and being able to manufacture high-density sintered components by a press molding method is required Powder composition. However, to date, no such alloy powder composition has been proposed.

Patent Document 1: JP-A-2001-089801

Patent Document 2: Japanese Patent No. 3964135

The present invention aims to provide an alloy powder composition, which contains austenitic stainless steel as a main component, has excellent fluidity and sinterability, and can be used to manufacture high-density sintered components by a compression molding method.

To achieve the goal, the alloy powder composition according to the present invention has the following configuration.

(1) The alloy powder composition includes:

Alloy powder made of austenitic stainless steel with a diameter of 50% (D _{50) of 20 μm or more and 30 μm or less;}

Made of at least one metal oxide selected from the group consisting of _{Al 2} O ₃ , MgO, ZrO ₂ , Y ₂ O ₃ , CaO, SiO ₂ , and TiO _{2, with 50% of 5nm or more and 35nm or less} Fluidity improving particles with a diameter (D ₅₀ ) and a hydrophobic surface; and

Lubricant.

(2) The alloy powder composition has a content of fluidity improving particles of 0.005 mass% or more and 0.200 mass% or less, and

The lubricant content of 0.5% by mass or more and 1.5% by mass or less.

The alloy powder composition may include a coating film composed of a silane coupling agent, which coats the particle surface of the alloy powder in addition to or instead of the fluidity improving particles.

_{The alloy powder with a D 50} of 20 μm to 30 μm has high sinterability but low fluidity. When fluidity improving particles satisfying predetermined conditions are added to this alloy powder, fluidity can be improved while still maintaining high sinterability. Therefore, when this alloy powder composition is used as a raw material, a low-cost compression molding method can be used to manufacture a sintered component with high density and high heat resistance. To be clear, even if the alloy powder made of austenitic stainless steel is used, a sintered density of 91% or more can be obtained by the compression molding method.

The same effect can be obtained even when the surface of the alloy powder is subjected to SC treatment in addition to or instead of adding fluidity improving particles.

Figure 1 shows that when using austenitic stainless steel (SUS304L) powder and fertilizer grained stainless steel (SUS434L) powder (both of which have a 50% diameter (D ₅₀ ) of about 60 μm) to manufacture sintered components, the compaction pressure and compaction The relationship between solid density and sintered density.

Figure 2 shows the results of the salt spray test of the sintered bodies obtained in Example 1 and Comparative Example 1.

Fig. 3 is a graph showing the influence of sintering temperature on the sintered density of SUS304L sintered body.

Figure 4 shows the relationship between the sintered density and hardness of the SUS304L sintered body.

[Specific example]

Specific examples of the present invention will be described in detail below.

1. Alloy powder composition

The alloy powder composition according to the present invention has the following configuration.

(1) The alloy powder composition includes:

Alloy powder made of austenitic stainless steel with a diameter of 50% (D _{50) of 20 μm or more and 30 μm or less;}

Made of at least one metal oxide selected from the group consisting of _{Al 2} O ₃ , MgO, ZrO ₂ , Y ₂ O ₃ , CaO, SiO ₂ , and TiO _{2, with 50% of 5nm or more and 35nm or less} Fluidity improving particles with a diameter (D ₅₀ ) and a hydrophobic surface; and

Lubricant.

(2) The alloy powder composition has a content of fluidity improving particles of 0.005 mass% or more and 0.200 mass% or less, and

The lubricant content of 0.5% by mass or more and 1.5% by mass or less.

1.1. Alloy powder

1.1.1. Composition

The alloy powder is made of austenitic stainless steel. In the present invention, the composition of austenitic stainless steel is not particularly limited, and the optimal composition can be selected according to the application.

Examples of the austenitic stainless steel used in the present invention include: (a) 18Cr-8Ni-low C steel (SUS304L); (b) 18Cr-12Ni-2.5Mo-low C steel (SUS316L); (c) 25Cr-20Ni steel (SUS310S); and (d) 21Cr-24.5Ni-4.5Mo-1.5Cu-low C steel (SUS890L).

1.1.2. Average particle size and particle size distribution

"50% diameter (D ₅₀ )" refers to the particle size (median diameter) when the integral value of the particle size is 50%.

"10% diameter (D ₁₀ )" refers to the particle size when the integral value of the particle size is 10%.

"90% diameter (D ₉₀ )" refers to the particle size when the integral value of the particle size is 90%.

The D _{50 of the} alloy powder will affect the density and productivity of the sintered component. Sinterability of the alloy powder decreases and the improvement of D _50, and can obtain a high density sintered components. However, in _{the case where D 50 is} too small, fluidity is reduced and it is difficult to efficiently fill the alloy powder into the mold. Therefore, D ₅₀ needs to be 20 μm or more. D _{50 is} preferably 22 μm or more.

On the other hand, with increasing fluidity D ₅₀ increases. However, when the D _{50 is} too large, the sinterability is reduced and a sintered component made of austenitic stainless steel with a high density (relative density of 91% or more) cannot be obtained. Therefore, D ₅₀ needs to be 30 μm or less. D _{50 is} preferably 28 μm or less.

Generally speaking, the sintered density increases as the particle size distribution of the alloy powder becomes narrower. On the other hand, making the particle size distribution of the alloy powder more narrow than necessary will result in an increase in the cost of the alloy powder. In order to achieve relatively high sintering density and low cost at the same time, the alloy powder preferably has (a) 10% diameter (D ₁₀ ) of 7 μm or more and 13 μm or less, and (b) 90% of 40 μm or more and 65 μm or less Diameter (D ₉₀ ).

1.2 Fluidity-improving particles

"Fluidity-improving particles" refer to nano-sized particles made of metal oxides. When a predetermined amount of metal oxide nanoparticles is added to the alloy powder of 20 μm to 30 μm, the fluidity of the alloy powder is improved. It is believed that this is due to the fact that the fluidity improving particles reduce the frictional resistance between the alloy powders.

1.2.1. Composition

In the present invention, the fluidity improving particles are made of Al ₂ O ₃ , MgO, ZrO ₂ , Y ₂ O ₃ , CaO, SiO ₂ , and TiO ₂ . Any of these metal oxides has a great effect of improving the fluidity of alloy powder made of austenitic stainless steel, and is therefore suitable as a material for fluidity-improving particles. The fluidity improving particles can be made of any of these metal oxides, or can be a mixture of two or more of these metal oxides.

Among them, ZrO ₂ , SiO ₂ , and/or TiO ₂ are preferably used as fluidity improving particles. This is because sintered components made of alloy powder compositions containing these metal oxides have excellent corrosion resistance against salt water spray.

In addition, the surface of the fluidity improving particles must be hydrophobic. The fluidity improving particles have a large surface area and therefore easily absorb moisture. When the fluidity improving particles absorb moisture, the contact resistance between the particles increases, and the fluidity of the alloy powder composition decreases.

In contrast, when the surface of the fluidity-improving particles is hydrophobic, the fluidity-improving particles can be prevented from absorbing water, thereby improving the fluidity of the alloy powder composition during compression molding.

Regarding the method of making the surface of the fluidity-improving particle hydrophobic, there is, for example, a method of treating the surface of the fluidity-improving particle with a silane coupling agent. The details of the treatment with the silane coupling agent will be described later.

1.2.2. Average particle size

Having a D ₅₀ is too small in the case of the flowability improving particles, the fluidity improving effect can not be obtained. _{Therefore, the fluidity improving particles must have a D 50 of} 5 nm or more, and preferably 6 nm or more.

On the other hand, the flowability improving particles having a D ₅₀ is too large in the case, can not be obtained a sintered body having a high density. _{Therefore, the fluidity improving particles must have a D 50 of} 35 nm or less, and preferably 20 nm or less.

1.2.3. Content

"The content of fluidity-improving particles" refers to _{the ratio of the mass (W p} ) of the fluidity-improving particles to the total mass (W _total ) of the alloy powder composition (=W _p ×100/W _total ).

In the case where the content of the fluidity improving particles is too small, the fluidity of the alloy powder decreases. In order to obtain high fluidity, the content of fluidity improving particles must be 0.005% by mass or more. The content of the fluidity improving particles is preferably 0.01% by mass or more.

On the other hand, in the case where the content of the fluidity improving particles becomes too large, the sinterability of the alloy powder decreases. Therefore, the content of fluidity improving particles must be 0.200% by mass or less. The content of the fluidity improving particles is preferably 0.100% by mass or less.

1.3. Lubricants

1.3.1. Composition

In addition to the fluidity improving particles, a lubricant is further added to the alloy powder. The lubricant is added to promote ejection of the molded body from the mold during press molding.

The composition of the lubricant is not particularly limited, as long as it is a compound having a lubricating effect. Examples of lubricants include lithium stearate, zinc stearate, ethylene distearate, Calcium stearate, magnesium stearate, aluminum stearate, and barium stearate. These lubricants can be used alone or in combination of two or more of them.

1.3.2. Content

"Lubricant content" refers to the ratio of the mass of the lubricant (W _L ) to the total mass of the alloy powder composition (W _total ) (=W _L ×100/W _total ).

In the case where the content of the lubricant is too small, the sinterability of the alloy powder decreases. Therefore, the lubricant content needs to be 0.5% by mass or more. The content of the lubricant is preferably 0.7% by mass or more, and more preferably 0.8% by mass or more.

On the other hand, in the case where the content of the lubricant is too large, the fluidity of the alloy powder decreases. Therefore, the content of the lubricant needs to be 1.5% by mass or less. The content of the lubricant is preferably 1.3% by mass or less, and more preferably 1.2% by mass or less.

1.4. Treatment with silane coupling agent 1.4.1. Overview

"Treatment with silane coupling agent (SC treatment)" refers to the treatment of coating the surface of alloy powder with a coating film made of silane coupling agent. There is no specific restriction on the type of silane coupling agent, and the best type can be selected according to the application.

Examples of silane coupling agents include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-methacryloxypropylmethyl Ethoxysilane.

The SC treatment on the surface of the alloy powder is similar to the fluidity improving particles, and has the effect of improving the fluidity of the alloy powder. It is believed that this is because the surface of the alloy powder becomes hydrophobic by the SC treatment and prevents moisture absorption.

Instead of adding fluidity-improving particles or adding fluidity-improving particles, SC treatment can be performed. When SC treatment and fluidity improving particles are added at the same time, there are advantages of improving the hydrophobic function of the alloy powder and further improving fluidity.

1.4.2. Content of Coating Film

_{"The content of the coating film" refers to the ratio of the mass (W SC} ) of the coating film introduced by the SC treatment to the total mass (W _total ) of the _{alloy powder composition (=W SC} ×100/W _total ).

In the case where the content of the coating film is too small, the fluidity of the alloy powder decreases. Therefore, the content of the coating film needs to be 0.005 mass% or more. The content of the coating film is preferably 0.01% by mass or more.

On the other hand, in the case where the content of the coating film is too large, the sinterability of the alloy powder decreases. Therefore, the content of the coating film needs to be 0.300% by mass or less. The content of the coating film is preferably 0.100% by mass or less.

2. Method of manufacturing alloy powder composition

The alloy powder composition according to the present invention can undergo (a) subject the alloy powder to SC treatment as necessary, add lubricant to it and mix it, and (b) further add fluidity improving particles to the alloy powder-lubricant mixture And mix them to make. Alternatively, the alloy powder composition according to the present invention can be manufactured by subjecting the alloy powder to SC treatment through (a'), adding a lubricant to it and mixing it.

There are no specific restrictions on the method of manufacturing alloy powder. Examples of the method of manufacturing alloy powder include a water spray method, a gas spray method, a melt-spinning method, a rotating electrode method, and a reduction method.

The method used to mix the raw material blend is also not particularly limited. Used to mix raw materials Examples of material mixers include double-cone mixers and V-cone mixers.

More specifically, the SC treatment is preferably performed by spraying the solution containing the silane coupling agent onto the alloy powder and drying it.

3. Function

Figure 1 shows that when using austenitic stainless steel (SUS304L) powder and fertilizer grained stainless steel (SUS434L) powder (both of which have a 50% diameter (D ₅₀ ) of about 60 μm) to manufacture sintered components, the compaction pressure and compaction The relationship between solid density and sintered density. Set the sintering temperature to 1,200°C. In the case of the same compaction pressure, regardless of the powder composition, the compaction density is substantially the same. However, the sintered density greatly depends on the powder composition, and the austenitic stainless steel has a lower sintered density than the fat iron stainless steel.

For example, when the compaction pressure is 7t/cm ² , the compaction density in each of the austenitic stainless steel and the ferrite stainless steel is about 83%. On the other hand, the sintered density of ferrite stainless steel is about 91% (an increase of about 8%), while the sintered density of austenitic stainless steel is about 86% to 87% (an increase of about 3% to 4%). It is believed that this is because the diffusion coefficient of Fe in austenitic iron is lower than that in fat iron.

As mentioned above, in the case of manufacturing a sintered component by a press molding method, an alloy powder _{having a D 50 of about 60 μm is generally used. The alloy powder with a D 50} of about 60 μm has excellent fluidity and low cost, but has low sinterability. Therefore, when the austenitic stainless steel powder with low sinterability is used to manufacture sintered components under normal conditions, the achievable sintered density is less than 90%.

On the other hand, regarding a method of obtaining a high-density sintered body, for example, a metal injection molding (MIM) method is known. _{Since powders with a D 50} of about 10 μm are used in the MIM method, even in the case of austenitic stainless steel, the sintered density reaches about 97%. However, the MIM method has a high process cost.

_{In contrast, alloy powders having a D 50} of 20 μm to 30 μm have high sinterability but low fluidity. When fluidity improving particles satisfying predetermined conditions are added to this alloy powder, fluidity can be improved while maintaining high sinterability. Therefore, when this alloy powder composition is used as a raw material, a low-cost compression molding method can be used to manufacture a sintered component with high density and high heat resistance. Specifically, even in the case of alloy powder made of austenitic stainless steel, a sintered density of 91% or more can be obtained by pressing.

The same effect can be obtained when the surface of the alloy powder is subjected to SC treatment in addition to or instead of adding fluidity improving particles.

[Example]

(Examples 1 to 41, Comparative Examples 1 to 14)

1. Manufacturing samples

Use SUS304L, SUS316L, SUS310S, or SUS890L as alloy powder. The alloy powder is produced by the water spray method. _{The 50% diameter (D 50} ) and particle size distribution of the alloy powder are controlled by the classification method. In addition, some alloy powders are pretreated with silane coupling agent-3-methacryloxypropyltrimethoxysilane.

SiO ₂ , Al ₂ O ₃ , MgO, ZrO ₂ , Y ₂ O ₃ , CaO, or TiO _{2 are} used as fluidity improving particles. The fluidity-improving particles are prepared by pulverizing reagents with a compound purity of 97% or more to nano-size using a grinder. Except for Comparative Example 9, the surface of the fluidity improving particles was subjected to SC treatment with 3-methacryloxypropyltrimethoxysilane.

In addition, lithium stearate, zinc stearate, or ethylene distearate is used as a lubricant.

After SC processing the alloy powder as necessary, a predetermined amount of lubricant is added to the alloy powder, and the raw materials are mixed with a double cone mixer. In addition, a predetermined number of fluidity improving particles are added thereto as needed, and the raw materials are mixed with a double cone mixer to obtain an alloy powder composition.

The obtained alloy powder composition is filled in a mold with an inner diameter of 11 mm, and is molded by a hydraulic press under a pressure of 686 MPa. Press molding is performed at 70°C or below.

In addition, the molded body is subjected to heat treatment to obtain a sintered body. The sintering temperature is 1,170°C. The sintering atmosphere is in a vacuum.

2. Test method

2.1. Powder characteristics

2.1.1. Particle size distribution of alloy powder

The laser diffraction method (Microtrac, MT-3300) is used to measure the particle size distribution of the alloy powder. From the obtained particle size distribution, calculate D ₅₀ (average, cumulative 50%), D ₁₀ (cumulative 10%), and D ₉₀ (cumulative 90%).

2.1.2. Fluidity evaluation of alloy powder composition

The fluidity of alloy powder was evaluated according to the method used to measure the fluidity of metal powder (JIS Z 2502: 2012). However, when a lubricant is added to the alloy powder, the fluidity is reduced and the alloy powder does not flow through the pore diameter of 2.63 mm used in the method for measuring the fluidity of metal powder (JIS Z 2502: 2012) funnel. because Here, a funnel with a pore diameter of 5 mm is used in the method for measuring the apparent density of metal powder (JIS Z 2504: 2012). Put 50g of the alloy powder composition in the funnel, and measure the time for the alloy powder composition to completely flow out.

2.2. Sintered body characteristics

2.2.1. Relative density of sintered body

The density of the sintered body is measured to calculate the relative density of the sintered body. SUS304L: 7.93 g/cm ³ , SUS316L: 7.98 g/cm ³ , SUS310S: 7.98 g/cm ³ , and SUS890L: 8.05 ^{g/cm 3 are} used as the true density.

2.2.2. Hardness

The Rockwell hardness (HRB) test was performed in accordance with JIS Z 2245:2016.

2.2.3. Corrosion resistance

According to JIS Z 2371:2015, the neutral salt water spray test was carried out. The evaluation of corrosion resistance is described by the time of confirmation of corrosion (confirmation of rust at 24, 48, 72, 96, and 120 hours), and the case where corrosion does not occur even after 120 hours is described as "120 <".

3. Results

3.1. Table 1 (Examples 1 to 20, Comparative Examples 1 to 9)

Table 1 shows the characteristics of the alloy powder composition and sintered body, the particle size of the alloy powder, the average particle size and content of the fluidity improving particles, and the type and content of lubricants. Figure 2 shows the results of the salt spray test of the sintered bodies obtained in Example 1 and Comparative Example 1. Table 1 and Figure 2 reveal the following results.

Table 1

3.1.1. Particle size of alloy powder (Examples 1 to 5, Comparative Examples 1 to 3)

(1) having a D ₅₀ of 63.2μm in the alloy powder, alloy powder flowability of the composition is high, but the sintered body sintered density, hardness, and corrosion resistance decreases (Comparative Example 1). In the case where the alloy powder has a D ₅₀ of 33.4 μm, the hardness and corrosion resistance are improved, but the sintered density (relative density) is lower than 91% (Comparative Example 2).

(2) the case of having a D ₅₀ of less than 20μm, the sintered density of the sintered body, hardness, and corrosion resistance in the alloy powder while the alloy powder flowability-diminishing composition (Comparative Example 3).

(3) In the case where the alloy powder has a D ₅₀ of 20 μm to 30 μm, the fluidity of the alloy powder composition is high, and the sintered density, hardness, and corrosion resistance of the sintered body are also increased (Examples 1 to 5).

(4) The corrosion resistance increases as the sintered density of the sintered body increases (Figure 2).

3.1.2. The content of fluidity improving particles (Examples 6 to 10, Comparative Example 4)

(1) In the case where the content of fluidity improving particles (SiO ₂ ) is 0.050% by mass to 0.200% by mass, the fluidity of the alloy powder composition increases, and the sintered density also increases (Examples 6 to 10).

(2) In the case where the content of fluidity improving particles is too high, the sintered density is reduced (Comparative Example 4).

3.1.3. Type and amount of lubricant (Examples 11 to 14, Comparative Examples 5 to 6)

(1) In the case where the content of the lubricant is small, the sintered density of the sintered body is reduced (Comparative Example 5). On the other hand, when the lubricant content is too high, the sintered density decreases Is small, and the fluidity of the alloy powder composition is also reduced (Comparative Example 6).

(2) When the content of the lubricant is appropriate, the sintered density of the sintered body is high, and the fluidity of the alloy powder composition is also increased (Examples 11 and 12).

(3) Even if the type of lubricant was changed, almost the same effect was observed (Examples 13 and 14).

3.1.4. Diameter and SC treatment of fluidity improving particles (Examples 15 to 20, Comparative Examples 7 to 9)

(1) The sintered density of the sintered body with reduced flowability improving particles of D ₅₀ is increased (Examples 15 to 20).

(2) In _{the case where the D 50 of the} fluidity improving particles exceeds 35 nm, the sintered density of the sintered body decreases (Comparative Examples 7 and 8).

(3) In the case where the fluidity improving particles were not subjected to SC treatment, fluidity was reduced (Comparative Example 9).

3.2. Table 2 (Examples 21 to 28)

Table 2 shows the characteristics of the alloy powder composition and the sintered body, and the composition of the fluidity improving particles. Table 2 reveals the following results.

(1) Even when Al ₂ O ₃ , MgO, ZrO ₂ , Y ₂ O ₃ , CaO, or TiO _{2 are} used as fluidity improving particles, the fluidity of the alloy powder composition is high, and the sintered density of the sintered body , Hardness, and corrosion resistance are also increased (Examples 21 to 26).

(2) Even in the case of using two materials as the fluidity improving particles, almost the same effect was observed (Examples 27 and 28).

(3) _{The sintered body containing ZrO 2} or TiO ₂ has higher corrosion resistance than the sintered body containing other fluidity improving particles (Example 23, Example 26).

3.3. Table 3 (Examples 29 to 34, Comparative Examples 10 to 12)

Table 3 shows the characteristics of the alloy powder composition and the sintered body, and the composition of the alloy powder. Table 3 reveals the following results.

(1) Even when the composition of the alloy powder is different, the fluidity of the alloy powder composition is improved by adding an appropriate number of fluidity improving particles, and the sintered density, hardness, and corrosion resistance of the sintered body are also increased (implemented Examples 29 to 34).

(2) In the case where no fluidity improving particles are added at all, the fluidity of the alloy powder composition decreases regardless of the composition of the alloy powder. As a result, the sintered density, hardness, and corrosion resistance of the sintered body were also reduced (Comparative Examples 10 to 12).

3.4. Table 4 (Examples 35 to 41, Comparative Examples 13 and 14)

Table 4 shows the characteristics of the alloy powder composition and the sintered body, and the SC treatment. Table 4 reveals the following results.

(1) Even in the case of SC treatment instead of adding fluidity improving particles, the fluidity of the alloy powder composition increases, and the sintered density, hardness, and corrosion resistance of the sintered body also increase (Examples 35 to 40) .

(2) In the case where the content of the coating film formed by the SC treatment is too small, the fluidity of the alloy powder composition decreases (Comparative Example 13). On the other hand, in the case where the content of the coating film formed by the SC treatment is too high, the sintered density of the sintered body decreases (Comparative Example 14).

(3) When the fluidity improving particles (SiO ₂ ) are added and the SC treatment is performed at the same time, substantially the same effect is obtained (Example 41).

(Example 42, Comparative Example 15)

1. Manufacturing samples

A sintered body was manufactured by using SUS304L powder (D ₅₀ = 25.1 μm, high-density powder) in the same manner as in Example 3, except that the sintering temperature was changed (Example 42). _{Another sintered body was manufactured by using SUS304L powder (D 50} = 63.2 μm, general sintered powder) in the same manner as in Comparative Example 1, except that the sintering temperature was changed (Comparative Example 15).

2. Test method

2.1 Relative density of sintered body

The relative density of the sintered body was measured in the same manner as in Example 3.

2.2. Hardness

The Rockwell hardness (HRB) test was performed in the same manner as in Example 3.

3. Results

Figure 3 shows the effect of sintering temperature on the sintered density of SUS304L sintered body. Figure 4 shows the relationship between the sintered density and hardness of the SUS304L sintered body. The following results are revealed from Figure 3 and Figure 4.

(1) The sintering density increases with the increase of the sintering temperature. Specifically, in the case of using an _{alloy powder having a D 50} of about 25 μm, when the sintering temperature is 1,170° C. or higher, the relative density of the sintered body exceeds 91%. However, in the case of using an _{alloy powder having a D 50} of about 60 μm, even when the sintering temperature is 1,250° C., the relative density is lower than 90%.

(2) The hardness increases with the increase of sintered density.

Although specific examples of the present invention have been described in detail, the present invention is not limited to these specific examples, and various modifications can be made within the scope without departing from the spirit of the present invention.

This application is based on Japanese Patent Application No. 2018-163003 filed on August 31, 2018, the content of which is incorporated herein by reference.

(Industrial applicability)

The alloy powder composition according to the present invention can be used to manufacture various sintered components that require heat resistance (for example, sensor bosses and sintered flanges).

Claims (9)

An alloy powder composition comprising: alloy powder; fluidity improving particles of 0.005% by mass or more and 0.200% by mass or less; and lubricants of 0.5% by mass or more and 1.5% by mass or less, the above-mentioned lubricants are selected At least one of the group consisting of lithium stearate, zinc stearate, ethylene distearate, calcium stearate, magnesium stearate, aluminum stearate, and barium stearate, wherein the The alloy powder is made of austenitic stainless steel and has a 50% diameter D _{50 of} 20 μm or more and 30 μm or less, and the fluidity improving particles are selected from Al ₂ O ₃ , MgO, ZrO ₂ , Y _It is made of at least one metal oxide of the group consisting of 2 O ₃ , CaO, SiO ₂ , and TiO _{2 , has a 50% diameter D 50 of} 5 nm or more and 35 nm or less, and has a hydrophobic surface. The alloy powder composition of claim 1, wherein the fluidity improving particles are made of at least one metal oxide selected from the group consisting of _{ZrO 2} , SiO ₂ and TiO _2. The alloy powder composition of claim 1, which further comprises a coating film composed of a silane coupling agent, which coats the surface of the particles of the alloy powder. The alloy powder composition of claim 2, which further comprises a coating film composed of a silane coupling agent, which coats the surface of the particles of the alloy powder. Such as the alloy powder composition of claim 3, which has a coating film content of 0.005 mass% or more and 0.300 mass% or less. Such as the alloy powder composition of claim 4, which has a coating film content of 0.005 mass% or more and 0.300 mass% or less. An alloy powder composition, comprising: alloy powder; a coating film composed of a silane coupling agent, which coats the particle surface of the alloy powder; and 0.5% by mass or more and 1.5% by mass or less of lubricant, the above-mentioned lubrication The agent is at least one selected from the group consisting of lithium stearate, zinc stearate, ethylene distearate, calcium stearate, magnesium stearate, aluminum stearate, and barium stearate , Wherein the alloy powder is made of austenitic stainless steel and has a 50% diameter D _{50 of} 20 μm or more and 30 μm or less. Such as the alloy powder composition of claim 7, which has a coating film content of 0.005 mass% or more and 0.300 mass% or less. The alloy powder composition of any one of claims 1 to 8, wherein the alloy powder has: a 10% diameter D _{10 of} 7 μm or more and 13 μm or less; and a 90% diameter D of 40 μm or more and 65 μm or less ₉₀ .

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