KR102239632B1 - Alloy powder composition - Google Patents

Abstract

The present invention, as an alloy powder composition, alloy powder; 0.005 mass% or more and 0.200 mass% or less of fluidity improving particles; And a lubricant of 0.5% by mass or more and 1.5% by mass or more, and 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 include Al ₂ O ₃ , MgO, Made of at least one metal oxide selected from the group consisting of ZrO ₂ , Y 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 It relates to the composition.

Description

Alloy powder composition {ALLOY POWDER COMPOSITION}

The present invention relates to an alloy powder composition, and more particularly, to an alloy powder composition suitable for producing a high-density sintered component made of austenitic stainless steel.

In the "press-molding" method, a lubricant is mixed with alloy powders such as stainless steel, iron, copper, etc., the alloy powder is filled into a mold, the alloy powder is press-formed, and the molded body is sintered. It refers to a method of obtaining a sintered product by heat treatment in a (sintering furnace). The press molding method can produce complex and very sophisticated mechanical parts with high productivity. For this reason, sintered products are widely used in fields such as electricity, machinery and automobiles.

When a sintered product is manufactured using a press molding method, the sintered product has a higher density as the alloy powder has a smaller particle diameter. However, as the alloy powder has a smaller particle diameter, the alloy powder has a lower fluidity, which makes it difficult to fill the alloy powder into the mold. On the other hand, the metal injection molding (MIM) method, the granulation method, etc., are known as techniques for obtaining high-density sintered products, but these methods are due to high process cost, and are applied in applications requiring low cost (e.g., Automotive applications).

In order to solve the above-described problem, various proposals have been made in the prior art.

For example, Patent Document 1 discloses a mixed powder for a high-density sintered body in which Fe-B powder is mixed with a main powder made of an austenitic stainless steel.

Patent Document 1 discloses that (a) iron (Fe) has a smaller diffusion coefficient in austenite than in ferrite, so that the austenitic stainless steel is difficult to proceed with the sintering reaction, and (b) it is made of austenitic stainless steel. When auxiliary powder (e.g., Fe-B powder) that causes eutectic reaction with the main powder is added to the main powder, a liquid phase is formed in the gap of the main powder, and local liquid phase sintering is performed. Occurs to increase the sintered density of the sintered body.

Patent Document 2, as a powder composition for metallurgy, is an iron-based metal powder of 85% by mass or more, a binder of 0.005 to 3% by mass, a lubricant of 0.1 to 2% by mass, and 0.005 to 2 having an average particle diameter of less than 40 nm. It discloses containing mass% particulate silicon dioxide.

Patent Document 2 discloses that (a) when particulate silicon dioxide is mixed as a solvent in an iron-based metal powder, the fluidity of the powder composition increases; (b) when lubricant is added to the iron-based metal powder, the ejection force required to remove the molded part from the die can be reduced; (c) It is disclosed that the solvent also functions as an internal lubricant in the molding process.

In order to efficiently mass-produce sintered products using the press molding method, it is necessary to fill the mold with alloy powder with high efficiency. Therefore, the alloy powder for the sintered product is required to have high fluidity. In order to obtain high fluidity, generally an alloy powder having an average particle diameter of about 60 μm is used in the manufacture of a sintered product.

^{However, when a sintered product is manufactured at a general compaction pressure (about 7t/cm 2} ) using an austenitic stainless steel powder having an average particle diameter of about 60 μm, the sintering density is about 86%, The high sintering density (more than 90%) required to maintain airtightness cannot be obtained. In addition, since the porosity is about 14%, corrosion resistance, hardness and strength are insufficient.

On the other hand, since the ferritic stainless steel has high sinterability, the ferritic stainless steel can relatively easily achieve a high sintering density even under general production conditions of high productivity. However, since ferritic stainless steel is inferior in heat resistance, sintered products made of ferritic stainless steel remain used in exhaust system parts and the like at a low temperature.

In order to manufacture sintered products with excellent heat resistance and airtightness at low cost, an alloy powder composition containing austenitic stainless steel as a main component, excellent fluidity and sintering property, and capable of manufacturing high-density sintered products using a press molding method Required. However, so far no such alloy powder composition has been proposed.

Patent Document 1: Japanese Laid-Open Patent Publication No. 2001-089801 Patent Document 2: Japanese Patent No. 3964135

An object of the present invention is to provide an alloy powder composition containing an austenitic stainless steel as a main component, excellent in fluidity and sintering property, and capable of producing a high-density sintered product using a press molding method.

In order to achieve the above object, the alloy powder composition according to the present invention has the following configuration.

(1) The alloy powder composition is:

Alloy powder _{made of austenitic stainless steel and having a 50% diameter (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 , and 50% diameter (D 50} ) of 5 nm or more and 35 nm or less And fluidity-improving particles having a hydrophobic surface; And

slush

Includes.

(2) The alloy powder composition contains 0.005% by mass or more and 0.200% by mass or less of fluidity-improving particles, and

It has a content of a lubricant 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 that coats the particle surface of the alloy powder in addition to or in place of the fluidity improving particles.

_{The alloy powder having a D 50} of 20 to 30 μm has high sinterability but low fluidity. When fluidity improving particles satisfying predetermined conditions are added to such an alloy powder, fluidity may be improved while maintaining high sinterability. Therefore, if such an alloy powder composition is used as a raw material, a sintered product having high density and high heat resistance can be produced using a low-cost press molding method. In particular, even with an alloy powder made of austenitic stainless steel, a sintered density of 91% or more can be obtained by a press molding method.

In addition to or in place of the fluidity-improving particles, the same effect can be obtained even when the surface of the particles of the alloy powder is subjected to SC treatment.

1 shows when a sintered product is produced using austenitic stainless steel (SUS304L) powder and ferritic stainless steel (SUS434L) powder having both (both) of 50% diameter (D _{50) of about 60 μm} , The relationship between molding pressure and compact density and sintering density is shown.
2 shows the results of a salt water-spraying test of the sintered bodies obtained in Example 1 and Comparative Example 1. FIG.
3 is a graph showing the effect of the sintering temperature on the sintered density of the SUS304L sintered body.
4 is a graph showing the relationship between the sintered density and hardness of the SUS304L sintered body.

Hereinafter, an embodiment of the present invention will be specifically described.

1. Alloy powder composition

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

(1) The alloy powder composition is:

Alloy powder _{made of austenitic stainless steel and having a 50% diameter (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 , and 50% diameter (D 50} ) of 5 nm or more and 35 nm or less And fluidity-improving particles having a hydrophobic surface; And

slush

Includes.

(2) The alloy powder composition contains 0.005% by mass or more and 0.200% by mass or less of fluidity-improving particles, and

It has a content of a lubricant of 0.5% by mass or more and 1.5% by mass or less.

1.1. Alloy powder

1.1.1. Furtherance

The alloy powder is made of austenitic stainless steel. In the present invention, the composition of the austenitic stainless steel is not particularly limited, and an optimum composition may be selected according to the purpose.

Examples of austenitic stainless steel to which the present invention is applied 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 diameter and particle size distribution

"50% diameter (D ₅₀ )" refers to a particle diameter (median diameter) having an integrated value of 50% of the particle size.

"10% diameter (D ₁₀ )" refers to a particle diameter in which the integrated value of the particle size is 10%.

"90% diameter (D ₉₀ )" refers to a particle diameter with a combined value of 90% of the particle size.

The D ₅₀ of the alloy powder affects the density and productivity of the sintered product. _{As the D 50} of the alloy powder decreases, the sinterability improves, and a high-density sintered product can be obtained. However, when D ₅₀ is too small, the fluidity decreases and it becomes difficult to efficiently fill the mold with the alloy powder. Therefore, D ₅₀ needs to be 20 μm or more. D ₅₀ is preferably 22 µm or more.

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

In general, as the particle size distribution of the alloy powder narrows, the sintering density increases. On the other hand, narrowing the particle size distribution of the alloy powder more than necessary causes an increase in the cost of the alloy powder. In order to obtain a relatively high sintering density and low cost, the alloy powder is preferably (a) a 10% diameter (D ₁₀ ) of 7 μm or more and 13 μm or less, and (b) a 90% diameter of 40 μm or more and 65 μm or less ( D ₉₀ ).

1.2. Fluidity-improving particles

"Flow improving particle" refers to nanometer-sized particles made of metal oxide(s). When a predetermined amount of metal oxide nanoparticles are added to the alloy powder of 20 to 30 μm, the fluidity of the alloy powder is improved. This is thought to be because the fluidity-improving particles reduce the frictional resistance between the alloy powders.

1.2.1. Furtherance

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 or TiO ₂ . Any of these metal oxides has a great effect of improving the fluidity of an alloy powder made of austenitic stainless steel, and is therefore suitable as a material for fluidity-improving particles. The fluidity improving particles may be made of any of these metal oxides, and may be a mixture of two or more of these metal oxides.

Among these, ZrO ₂ , SiO ₂ and/or TiO ₂ are preferable as the fluidity improving particles. This is because the sintered product produced from the alloy powder composition containing these metal oxides is excellent in corrosion resistance against salt water spraying.

In addition, the surface of the fluidity improving particles needs to be hydrophobic. The fluidity-improving particles have a large surface area and are therefore easy to 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.

On the other hand, when the surface of the fluidity improving particles is hydrophobic, the fluidity improving particles can be prevented from absorbing moisture, and the fluidity of the alloy powder composition during press molding is improved.

As a method of making the surface of the fluidity improving particles hydrophobic, for example, there is a method of treating the surface of the fluidity improving particles with a silane coupling agent. Specific details of the treatment using the silane coupling agent will be described later.

1.2.2. Average particle diameter

When the fluidity improving particles have too small D ₅₀ , the fluidity improving effect cannot be obtained. Therefore, the fluidity improving particles need to have a _{D 50} of 5 nm or more, preferably 6 nm or more.

On the other hand, when the fluidity improving particles have too large D ₅₀ , a sintered body having a high density can be obtained. Therefore, the fluidity improving particles need to have _{a D 50} of 35 nm or less, preferably 20 nm or less.

1.2.3. content

"Content of the 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 ).

If 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 the fluidity improving particles needs to 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, when the content of the fluidity improving particles is excessive, the sinterability of the alloy powder decreases. Therefore, the content of the fluidity improving particles needs to be 0.200% by mass or less. The content of the fluidity improving particles is preferably 0.100% by mass or less.

1.3. slush

1.3.1. Furtherance

In addition to the fluidity improving particles, a lubricant is added to the alloy powder. Lubricants are added to facilitate 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 bis stearate amide, calcium stearate, magnesium stearate, aluminum stearate, and barium stearate. These lubricants may be used alone or in combination of two or more thereof.

1.3.2. content

"Content of lubricant" refers to the ratio of the mass (W _{L ) of the lubricant to the total} mass (W total) of the alloy powder composition (=W _L × 100/W _total ).

If the content of the lubricant is too small, the sinterability of the alloy powder decreases. Therefore, the content of the lubricant 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, when the content of the lubricant is excessive, 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, more preferably 1.2% by mass or less.

1.4. Treatment with Cylindrical Coupling Agent

1.4.1. summary

"Treatment with a silane coupling agent (SC treatment)" refers to a treatment of coating the surface of an alloy powder with a coating film made of a silane coupling agent. The type of the silane coupling agent is not particularly limited, and the optimum type may be selected according to the purpose.

Examples of the silane coupling agent include 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-methacryloxypropylmethylethoxysilane.

The SC treatment on the surface of the alloy powder has an effect of improving the fluidity of the alloy powder, similar to the fluidity-improving particles. This is considered to be because the surface of the alloy powder becomes hydrophobic by the SC treatment to prevent moisture absorption.

The SC treatment may be performed in place of the addition of the flowability improving particles, or in addition to the addition of the flowability improving particles. When the SC treatment and the addition of the fluidity improving particles are performed at the same time, there is an advantage that the hydrophobic function of the alloy powder is improved and the fluidity is further improved.

1.4.2 Content of coating film

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

If 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% by mass or more. The content of the coating film is preferably 0.01% by mass or more.

On the other hand, when the content of the coating film is excessive, 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 for producing alloy powder composition

The alloy powder composition according to the present invention includes (a) applying SC treatment to the alloy powder as necessary, adding a lubricant thereto, and mixing, (b) further adding fluidity-improving particles to the mixture of the alloy powder and the lubricant to mix them. It can be produced by doing. Alternatively, the alloy powder composition according to the present invention can be produced by (a') applying the SC treatment to the alloy powder, adding a lubricant thereto, and mixing.

The method of producing the alloy powder is not particularly limited. Examples of the method of producing the alloy powder include a water injection method, a gas injection method, a melt spinning method, a rotating electrode method, and a reduction method.

The method of mixing the raw material blend is also not particularly limited. Examples of the mixer for mixing the raw material blend include a double cone mixer and a V cone mixer.

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

3. Function

1 shows when a sintered product is produced using austenitic stainless steel (SUS304L) powder and ferritic stainless steel (SUS434L) powder having both (both) of 50% diameter (D _{50) of about 60 μm} , The molding pressure and the relationship between the green density and the sintering density are shown. The sintering temperature was set at 1200°C. In the case of the same molding pressure, the green compact density was substantially the same regardless of the powder composition. However, the sintering density largely depends on the powder composition, and austenitic stainless steels have a lower sintering density than ferritic stainless steels.

For example, when the molding pressure was 7t/cm ² , the green compaction density was about 83% in each of austenitic stainless steel and ferritic stainless steel. On the other hand, the sintered density of ferritic stainless steel is about 91% (approximately 8% increase), while the sintered density of austenitic stainless steel is about 86-87% (approximately 3-4% increase). This is considered to be because the diffusion coefficient of Fe in austenite is lower than that in ferrite.

As described above, when a sintered product is produced using a press molding method, an alloy powder having _{a D 50 of about 60 μm is generally used. The alloy powder having a D 50} of about 60 μm is excellent in fluidity and low in cost, but has low sinterability. Therefore, when a sintered product is produced under general conditions using austenitic stainless steel powder having low sinterability, the achievable sintering density is less than 90%.

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

On the other hand, the _{alloy powder having a D 50} of 20 to 30 μm has high sinterability and low fluidity. When fluidity improving particles satisfying predetermined conditions are added to such an alloy powder, fluidity can be improved while maintaining high sinterability. Therefore, if such an alloy powder composition is used as a raw material, a sintered product having high density and high heat resistance can be produced using a low-cost press molding method. Specifically, even in an alloy powder made of austenitic stainless steel, a sintered density of 91% or more can be obtained by a press forming method.

In place of or in addition to the addition of the fluidity improving particles, the same effect can be obtained if the SC treatment is applied to the surface of the alloy powder.

Example

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

1. Sample production

SUS304L, SUS316L, SUS310S, or SUS890L was used as the alloy powder. The alloy powder was produced by the water spray method. The 50% diameter (D ₅₀ ) and particle size distribution of the alloy powder were controlled by the classification method. In addition, some of the alloy powder was pre-treated with a silane coupling agent, 3-methacryloxy propyl trimethoxysilane.

SiO ₂ , Al ₂ O ₃ , MgO, ZrO ₂ , Y ₂ O ₃ , CaO, or TiO ₂ were used as the fluidity improving particles. By pulverizing a reagent having a compound purity of 97% or more into nano-sized with an attritor, particles with improved fluidity are produced. Except for Comparative Example 9, the surface of the flowability improving particles was subjected to SC treatment with 3-methacryloxy propyl trimethoxysilane.

In addition, lithium stearate, zinc stearate, or ethylene bis stearic acid amide were used as lubricants.

After the SC treatment was performed on the alloy powder as necessary, a predetermined amount of lubricant was added to the alloy powder, and the raw materials were mixed using a double cone mixer. Further, if necessary, a predetermined number of fluidity improving particles were added, and the raw materials were mixed using a double cone mixer to obtain an alloy powder composition.

The obtained alloy powder composition was filled into a mold having an inner diameter of 11 mm, and press-molded at a pressure of 686 MPa using a hydraulic press. Press molding was performed at 70°C or lower.

Further, heat treatment was applied to the molded body to obtain a sintered body. The sintering temperature was 1170°C. The sintering atmosphere was vacuum.

2. Test method

2.1. Powder properties

2.1.1. Particle size distribution of alloy powder

The particle size distribution of the alloy powder was measured by laser diffraction (Microtrac, MT-3300). From the obtained particle size distribution, D ₅₀ (average, cumulative 50%), D ₁₀ (cumulative 10%) and D ₉₀ (cumulative 90%) were calculated.

2.1.2. Evaluation of flowability of alloy powder composition

The flowability of the alloy powder was evaluated according to the method of measuring the flowability of the metal powder (JIS Z 2502: 2012). However, when a lubricant is added to the alloy powder, the fluidity decreases, and the alloy powder does not flow through the funnel having a pore diameter of 2.63 mm used in the method of measuring the fluidity of the metal powder (JIS Z 2502: 2012). Therefore, a funnel having a pore diameter of 5 mm used in a method of measuring the apparent density of metal powder (JIS Z 2504:2012) was used. 50 g of the alloy powder composition was put into the funnel, and the time until the alloy powder composition completely flowed was measured.

2.2. Sintered body characteristics

2.2.1. Relative density of sintered body

The density of the sintered body was 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 were used as actual densities.

2.2.2. Hardness

Rockwell hardness (HRB) test was performed according to JIS Z 2245: 2016.

2.2.3. Corrosion resistance

The neutral brine spray test was performed according to JIS Z 2371: 2015. The evaluation of corrosion resistance was described as the time at which corrosion was confirmed (confirmation of whether rust occurred in 24, 48, 72, 96 and 120 hours), and "120<" if no corrosion occurred after 120 hours. It was described as.

3. Results

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

Table 1 shows the alloy powder composition and the sintered body, the particle diameter of the alloy powder, the average particle diameter and content of the fluidity improving particles, and the type and content of the lubricant. 2 shows the results of a salt water spray test of the sintered bodies obtained in Example 1 and Comparative Example 1. FIG. The following can be seen from Table 1 and FIG. 2.

[Table 1] (continued)

3.1.1. The particle size of the alloy powder (Examples 1 to 5, Comparative Examples 1 to 3)

(1) When the alloy powder had a D ₅₀ of 63.2 μm, the flowability of the alloy powder composition was high, but the sintered density, hardness and corrosion resistance of the sintered body were decreased (Comparative Example 1). When the alloy powder had a D ₅₀ of 33.4 µm, the hardness and corrosion resistance were improved, but the sintered density (relative density) was less than 91% (Comparative Example 2).

(2) When the alloy _{powder had a D 50} of less than 20 μm, the sintered density, hardness and corrosion resistance of the sintered body were high, but the fluidity of the alloy powder composition was decreased (Comparative Example 3).

(3) When the alloy _{powder had a D 50} of 20 to 30 μm, the flowability of the alloy powder composition was high, but the sintered density, hardness and corrosion resistance of the sintered body were high, and the flowability of the alloy powder composition was also increased (Example 1~5).

(4) As the sintered density of the sintered body increased, the corrosion resistance increased (Fig. 2).

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

(1) Fluidity improvement When _{the content of particles (SiO 2} ) was 0.050 to 0.200 mass%, the fluidity of the alloy powder composition increased, and the sintering density also increased (Examples 6 to 10).

(2) When the content of the fluidity improving particles was excessive, the sintered density decreased (Comparative Example 4).

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

(1) When the content of the lubricant was small, the sintered density of the sintered body decreased (Comparative Example 5). On the other hand, when the content of the lubricant was excessive, the sintering density decreased, and the fluidity of the alloy powder also decreased (Comparative Example 6).

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

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

3.1.4. Fluidity-improving particle diameter and SC treatment (Examples 15 to 20, Comparative Examples 7 to 9)

(1) Improved flowability As the D ₅₀ of the particles decreased, the sintered density of the sintered body increased (Examples 15 to 20).

(2) When D ₅₀ of the fluidity improving particles exceeded 35 nm, the sintered density of the sintered body decreased (Comparative Examples 7 and 8).

(3) Flowability improvement When the SC treatment was not applied to the particles, the flowability decreased (Comparative Example 9).

3.2. Table 2 (Examples 21-28)

Table 2 shows the properties of the composition of the alloy powder composition, the sintered body, and the fluidity-improving particles. The following can be seen from Table 2.

(1) When Al ₂ O ₃ , MgO, ZrO ₂ , Y ₂ O ₃ , CaO, or TiO ₂ were used as the fluidity improving particles, the fluidity of the alloy powder composition was high, and the sintered density, hardness, and Corrosion resistance was also increased (Examples 21-26).

(2) Even when two types of materials were used 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 (Examples 23 and 26).

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

Table 3 shows the properties of the alloy powder composition and the sintered body, and the composition of the alloy powder. The following can be seen from Table 3.

(1) Even when the composition of the alloy powder was different, the flowability of the alloy powder composition was increased by adding an appropriate number of flowability improving particles, and the sintered density, hardness and corrosion resistance of the sintered body were also increased (Examples 29-34).

(2) Improved flowability When no particles were added, the flowability of the alloy powder composition decreased 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 properties of the alloy powder composition, the sintered body, and the SC treatment. The following can be seen from Table 4.

(1) Improved flowability Even when the SC treatment was performed instead of adding particles, the flowability of the alloy powder composition increased, and the sintered density, hardness and corrosion resistance of the sintered body increased (Examples 35 to 40).

(2) When the content of the coating film by the SC treatment was too small, the fluidity of the alloy powder composition decreased (Comparative Example 13). On the other hand, when the content of the coating film by the SC treatment was excessive, the sintered density of the sintered body decreased (Comparative Example 14).

(3) When both the addition of the fluidity improving particles (SiO ₂ ) and the SC treatment were performed, substantially the same effect was obtained (Example 41).

(Example 42, Comparative Example 15)

1. Preparation of the sample

_{A sintered body was prepared 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 prepared 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

3 shows the effect of the sintering temperature on the sintered density of the SUS304L sintered body. 4 shows the relationship between the sintered density and hardness of the SUS304L sintered body. The following can be seen from FIGS. 3 and 4.

(1) As the sintering temperature increased, the sintering density increased. _{In particular, when an alloy powder having a D 50} of about 25 μm is used, the relative density of the sintered body exceeded 91% when the sintering temperature was 1170° C. or higher. However, _{when an alloy powder having a D 50} of about 60 μm was used, the relative density was less than 90% even when the sintering temperature was 1250°C.

(2) As the sintering density increased, the hardness increased.

Although the embodiment of the present invention has been described in detail, the present invention is not limited to this embodiment, and various modifications may be made without departing from the essence of the present invention.

The present invention 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 products (eg, sensor bosses and sintered flanges) requiring heat resistance.

Claims (9)

As an alloy powder composition,
Alloy powder;
0.005 mass% or more and 0.200 mass% or less of fluidity improving particles; And
0.5% by mass or more and 1.5% by mass or less lubricant
Including,
The alloy powder is made of austenitic stainless steel, 50% diameter D _{50 of 20 μm or more and 30 μm or less, 10% diameter D 10} of 7 μm or more and 13 μm or less, and 90% of 40 μm or more and 65 μm or less Has a diameter D ₉₀ ,
The fluidity-improving particles are 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, and 50 nm or more and 35 nm or less.} An alloy powder composition having a% diameter D ₅₀ and having a hydrophobic surface. The method of claim 1,
The fluidity-improving particle is an alloy powder composition made of at least one metal oxide selected from the group consisting _{of ZrO 2} , SiO ₂ and TiO _2. The method of claim 1,
Alloy powder composition further comprising a coating film composed of a silane coupling agent coating the particle surface of the alloy powder. The method of claim 2,
Alloy powder composition further comprising a coating film composed of a silane coupling agent coating the particle surface of the alloy powder. The method of claim 3,
An alloy powder composition having a coating film content of 0.005% by mass or more and 0.300% by mass or less. The method of claim 4,
An alloy powder composition having a coating film content of 0.005% by mass or more and 0.300% by mass or less. As an alloy powder composition,
Alloy powder;
A coating film composed of a silane coupling agent coating the surface of the particles of the alloy powder; And
0.5% by mass or more and 1.5% by mass or less lubricant
Including,
The alloy powder is made of austenitic stainless steel, 50% diameter D _{50 of 20 μm or more and 30 μm or less, 10% diameter D 10} of 7 μm or more and 13 μm or less, and 90% of 40 μm or more and 65 μm or less Alloy powder composition having a diameter D _90. The method of claim 7,
An alloy powder composition having a coating film content of 0.005% by mass or more and 0.300% by mass or less. delete

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