JP7446751B2 - Method of forming dense metal layer - Google Patents

Description

Embodiments of the present invention relate to a method for forming a dense metal layer.

Many of the piping and equipment used for supplying steam from boilers etc. to steam turbines, water supply from steam turbines etc. to boilers etc., and drainage from these systems, etc., are capable of handling liquids such as water or steam. Used in environments in contact with representative gases. Furthermore, in a directly water-cooled turbine generator used in a large-capacity generator, the system is cooled by water, and some of its constituent members are in contact with a cooling medium such as water. Many of these system components are made of metal members, and when used in an environment where they come into contact with water or steam, there is a risk that various types of corrosion will occur.

On the other hand, water and steam leaks caused by corrosion of system components directly lead to plant shutdowns, and many processes are required before recovery, including investigating the cause, implementing countermeasures, and verifying the effectiveness of the countermeasures. shall be. Therefore, even occurrence of corrosion in one component or system becomes a major obstacle to stable operation of the plant. Therefore, countermeasure techniques for the deterioration of components that come into contact with water or steam environments are important in improving the reliability of not only each system component but also the entire plant system.

For example, the coil conductor part, which is the conductive part of the stator coil in a water-directly cooled turbine generator, is composed of a solid wire (copper wire) and a hollow wire (hollow copper wire) with holes formed through which cooling water flows. be done. Clips that are connected to cooling piping and supply cooling water are brazed to both ends of the coil conductor. Brazing, which integrates multiple strands in a clip and connects the clip to a strand of strands made up of multiple strands, not only functions as an electrical connection, but also serves as a seal for cooling water at the end face of the strands. ing. Conventionally, problems have been experienced in which this end face corrodes and causes water leakage, so various countermeasures have been taken.

In addition, members that have a composite part of dissimilar materials, such as a joint between dissimilar materials, and are used in an environment where they come in contact with liquid have deterioration factors specific to the joint of dissimilar materials.

For example, in the stator coil clip part mentioned above, when the material of the clip is a metal other than copper, conventionally, in order to reduce corrosion acceleration factors, the pH value of the environment has been lowered at the joint between these dissimilar materials. Countermeasures are being taken to avoid risks, such as using parts that do not contain elements that cause oxidation, or separating parts in situations where different materials come into contact with the same liquid.

As other countermeasures, progress is being made in developing methods to suppress deterioration by coating the target area with thermal spraying and treating the surface with highly corrosion-resistant materials. Thermal spraying techniques include, in addition to normal thermal spraying using high-temperature construction, low-temperature spraying that performs construction at a relatively low temperature of about 300°C to 700°C.

International Publication No. 2014/073633

In order to operate large-scale power generation equipment such as power generation plants stably, improve the reliability of the equipment, and realize a smooth energy supply, it is necessary to have a means to avoid the risk of damage caused by corrosion of metal components. .

However, in normal thermal spraying, there is a large amount of heat input into the base material, and there are concerns about thermal effects on the base material and residual stress, so the target base materials that can serve as the base material are limited. Therefore, there is a method of forming a metal layer on a base material using a cold spray method, which is one of the low-temperature thermal spraying methods.

The cold spray method is often applied, for example, to metals in which it is difficult to form a metal layer by melting or melting, or to metals whose compositions make it difficult to form a metal layer.

On the other hand, there are issues with film formability, such as the existence of materials that are difficult to form even with low-temperature thermal spraying, and erosion caused by sprayed particles during coating layer construction, making it impossible to form a film. There are many materials that cannot be secured.

Furthermore, for parts made of materials with low melting points, low softening points, or materials that cause brazing, methods of plating to suppress heat input are being considered, but the shape of the base material, the location of the construction, There are situations in which there are significant limitations on the

The problem to be solved by the present invention is to provide a method for forming a dense metal layer that can reliably form a dense metal layer on the surface of a metal member used in a liquid-contact environment.

A method for forming a dense metal layer according to an embodiment is a method for forming a dense metal layer in a metal member used in a liquid-contact environment, in which metal particles are collided with a base material at a temperature below the melting temperature. , using the kinetic energy to manufacture or procure the metal particles used in low-temperature spraying to form a film, with the average particle size X0 as the target particle size, and the metal particles having a particle size of the average particle size X. a step of releasing the agglomerated state of the metal particles obtained in the step of producing and procuring the metal particles; Regarding the metal particles, remove the metal particles having a predetermined particle size or more larger than the upper limit particle size vX (however, the magnification v is a positive real number larger than 1) of the particle size within the desired range where the effectiveness of the low-temperature spraying conditions exists. or, a sorting/confirmation step of confirming that the metal particles having the upper limit particle size vX or more of the particle size within the desired range are less than or equal to a predetermined frequency; and after the sorting/confirmation step, the metal particles are , a low-temperature spraying step of performing low-temperature spraying on the surface of the target member ,
The screening/confirmation step is characterized in that it includes a step of setting the upper limit particle size vX from the dependence of the magnification v on the average particle size X and the average particle size X.

FIG. 2 is a conceptual explanatory diagram qualitatively showing the influence of the particle size of metal particles in the method for forming a dense metal layer according to the first embodiment, in which (a) is a particle with a target particle size corresponding to the condition setting; (b) shows the case where the particle size is too small, and (c) shows the case where the particle size is too large. FIG. 2 is a conceptual explanatory diagram qualitatively showing the difference in the particle size distribution of metal particles in the method for forming a dense metal layer according to the first embodiment; FIG. b) shows the case where particles with a particle size of 7X are not included. It is a graph which shows the example of the 1st frequency distribution of the particle diameter of a metal particle in the formation method of the metal dense layer based on 1st Embodiment. It is a graph which shows the example of the 2nd frequency distribution of the particle size of a metal particle in the formation method of the metal dense layer based on 1st Embodiment. FIG. 2 is a block diagram showing the configuration of a cold spray device used in the method for forming a dense metal layer according to the first embodiment. 2 is a conceptual graph showing the upper limit of the particle size within a desired range of metal particles and the dependence of the boundary particle size on the average particle size in the method for forming a dense metal layer according to the first embodiment. FIG. 2 is a flow diagram showing the procedure of a method for forming a dense metal layer according to the first embodiment. It is a graph which shows the frequency distribution of the particle size of metal particles, cumulative distribution, and the example of the particle size within an expected range of the metal particle in the formation method of the metal dense layer which concerns on 2nd Embodiment. It is a graph which shows the example of the frequency distribution of the particle size of a metal particle in the formation method of the metal dense layer based on 3rd Embodiment.

Hereinafter, a method for forming a dense metal layer according to an embodiment of the present invention will be described with reference to the drawings. Here, parts that are the same or similar to each other are given the same reference numerals, and overlapping explanations will be omitted.

[First embodiment]
Below, the formation of a dense metal layer will be explained based on the findings confirmed by the inventors, and then the procedure of the method for forming a dense metal layer will be shown.

FIG. 1 is a conceptual explanatory diagram qualitatively showing the influence of the particle size of metal particles 10 in the method for forming a dense metal layer according to the first embodiment. In the case where the metal particles 10 sprayed onto the base material 1 are, in (a), particles 11 having a particle size within the desired range, and in (b), the metal particles 10 are small particles whose particle size is too small. In the case of No. 12, (c) shows the case of large-diameter particles 13 whose particle size is too large.

Here, the particle size within the desired range is a particle size within a range centered on the average particle size X for which cold spray conditions are considered to be reliably effective. Moreover, the metal particles 10 having a particle size within the desired range will be referred to as particles having a particle size within the desired range. It is assumed that the respective particle sizes of the small particle size particles 12 and the large particle size particles 13 deviate significantly from the particle size within the expected range.

In an attempt to manufacture metal particles 10 with a target particle size X0, the frequency distribution of the particle sizes of the metal particles 10 actually obtained after manufacturing is usually, for example, an approximately normal distribution if the horizontal axis is expressed as a logarithm of the particle size. In some cases, a shape close to that can be obtained. Although each of the figures shown below shows an example of a distribution having a shape close to a normal distribution, the present invention is not limited to this. In some cases, the grains are not symmetrical, and are biased towards the larger grain size side, for example. The following content is also applicable to cases where the left and right sides are not symmetrical.

Typical indicators for the frequency distribution of particle sizes include the mode diameter that gives the maximum value of the distribution, the median diameter that is the particle diameter (d50) corresponding to 50% of the accumulation, or the arithmetic mean diameter. Examples of the arithmetic mean diameter include number mean diameter, length mean diameter, area mean diameter, and volume mean diameter. Any of these may be used. In the following, the average diameter X will be indicated using the number average diameter according to the following equation (1).

Average diameter X=Σ(n・d)/Σn...(1)
Here, d is a representative value of each particle size channel, and n is a percentage of the number basis for each channel.

Note that when the large-sized particles 13 are removed by the sorting described later, the average particle size of the metal particles 10 after the removal operation changes from the average particle size before. However, hereinafter, the average particle size X will refer to the same value as the average particle size of the metal particles 10 before the removal operation is performed.

In cold spraying, optimal conditions are set according to the particle size that is the average value or intermediate value of the frequency distribution of the particle size of metal particles 10 sprayed onto the base material 1, and cold spraying is performed under these conditions. . In the case of cold spraying carried out under such optimal conditions, as shown in FIG. 21 is formed, leading to the formation of the dense metal layer 20.

In the case of small particle size particles 12 whose particle size is too small compared to the particle size within the desired range, which is the diameter of the particle size within the desired range particle 11, as shown in FIG. Even if it is sprayed onto the surface, it does not stick and scatters as non-adhesive parts 22.

In the case of large particle size particles 13 whose particle size is too large compared to the particle size within the desired range, which is the diameter of the particle size particles 11 within the desired range, as shown in FIG. When sprayed onto the surface of the base material 1, the adhesive layer 30 on the surface of the base material 1 is scooped out to form an excavated portion 32, and then the excavated particles 23 are scattered.

From the above, it can be seen that the presence of metal particles 10 whose particle size greatly deviates from the intended particle size range is not preferable for the particle size of the metal particles 10 supplied in the method for forming a dense metal layer. As mentioned above, in the case of small-sized particles 12, most of them do not adhere to the surface of the base material 1, which reduces the overall adhesion efficiency. Furthermore, in the case of large-sized particles 13, excavated portions 32 are formed in the adhesion layer 30 on the surface of the base material 1, which deteriorates the quality of the formation of the dense metal layer 20 itself. Therefore, it is important to ensure quality and adhesion efficiency that the metal particles 10 are mainly particles having a particle size within the desired range. Among the metal particles 10 having a particle size outside the desired range, the influence of the large particle size particles 13 is particularly problematic.

FIG. 2 is a conceptual explanatory diagram qualitatively showing the difference in particle size distribution of the metal particles 10 in the method for forming a dense metal layer according to the first embodiment. Regarding the manufactured or procured metal particles 10, (a) shows a case in which large-sized particles are included, and (b) shows a case in which large-sized particles are not included. As shown in (a), when the metal particles 10 to be cold-sprayed contain large-sized particles 13, the presence of the large-sized particles 13 is caused by the metal dense layer 20 (see FIG. ). Therefore, as shown in (b), it is desirable that the metal particles 10 used for cold spray contain as few large particles 13 as possible.

FIG. 3 is a graph showing an example of the frequency distribution of particle sizes of metal particles in the method for forming a dense metal layer according to the first embodiment. The horizontal axis is a logarithmic axis showing particle diameter (μm value), and the vertical axis is each frequency (%).

The frequency distribution of the particle size of the metal particles 10 is generally measured by the manufacturer of the metal particles 10 when the metal particles 10 are procured. However, the procurement side may measure the procured metal particles 10 after obtaining them. The average particle size X obtained from the actual measurement results usually almost matches the target particle size X0, but if it deviates from the target particle size X0, Cold spray conditions are set.

In FIG. 3, the particle diameter within the desired range is in the range from X/v to vX with the average particle diameter X as the center on a logarithmic scale. Here, "v" is a positive real number larger than 1 and indicates a magnification with respect to X.

Since the metal particles 10 obtained by manufacturing or the metal particles 10 obtained by procurement are fine particles with a particle size of the order of 100 μm or less, in many cases, some or many of the metal particles 10 are It aggregates to form a particle group, and its diameter also increases. As a result, the frequency distribution of particle sizes is often different from that immediately after production.

Therefore, it is also effective to check the proportion of particles with a particle size equal to or larger than the average particle size X after manufacturing or procurement, for example, using a mesh that corresponds to the average particle size X after manufacturing. It is. In addition, as described above, by the sieving operation, that is, by sieving using a mesh, the agglomerated lumps are often loosened and returned to the original individual metal particles 10. Alternatively, if necessary, the aggregates can be disintegrated using a bead mill using mechanical impact caused by beads.

Now, the minimum particle size in the large particle size region, that is, the particle size region of the large particle size particles 13 is assumed to be wX. However, "w" is a positive real number larger than 1 and indicates a magnification with respect to X. Furthermore, metal particles 10 having a diameter of X/w or less are referred to as small particle size particles 12. Furthermore, the particles in the intermediate region excluding the small particle size particles 12 in the small particle size region and the large particle size particles 13 in the large particle size region are referred to as intermediate particle size particles, and this region is referred to as the intermediate particle size region. . Here, the grain size wX at the boundary between the large grain size region and the intermediate grain size region will be referred to as the boundary grain size. That is, the boundary grain size wX is also the minimum value of the grain size in the large grain size region.

As described above, the particle size within the desired range is a particle size within a range that can be considered to correspond to the conditions of cold spray. Therefore, the maximum value vX of the grain size within the desired range is smaller than the boundary grain size wX. That is, magnification v<magnification w.

The large particle size particles 13 in the large particle size region reliably hinder film formation. Further, as described above, for particles having a particle size within the desired range, the cold spray conditions set corresponding to the average particle size X are certainly effective.

On the other hand, among the metal particles 10 in the intermediate particle size region, metal particles 10 having a larger particle size than the particle size within the desired range are set in accordance with the average particle size X as the distance from the particle size within the desired range increases. reduced effectiveness of cold spray conditions. That is, the proportion of the metal particles 10 that are effective for film formation decreases until the boundary particle size wX is reached, at which point the proportion becomes zero. That is, the boundary grain size wX can be said to be the upper limit of the region where the cold spray conditions are effective.

The frequency distribution curve G1 indicated by G1 in FIG. 3 has a shape that is symmetrical about the average particle diameter X on the logarithmic axis.

In the frequency distribution curve G1, the frequency of the metal particles 10 having the boundary grain size wX, which is the minimum value of the grain size in the large grain size region, which is the diameter region of the large grain size particles 13, is less than 10%. In addition, the inventors confirmed that, for example, when the average particle size X is 2 μm, the value of the magnification w is about 7. This point will be discussed later.

In this way, in the metal particles 10 distributed according to the frequency distribution curve G1 used in cold spraying, for example, the frequency of metal particles with the particle size of the boundary particle size wX is set to less than 10%, and the large particle size particles 13 are Existence rate is limited. That is, the metal particles 10 distributed according to the frequency distribution curve G1 have the effect of limiting quality deterioration due to the large diameter particles 13.

FIG. 4 is a graph showing an example of a second frequency distribution of particle sizes of metal particles in the method for forming a dense metal layer according to the first embodiment.

The frequency distribution curve G2 shown in FIG. 4 differs from the frequency distribution curve G1 shown in FIG. 3 in the distribution in the portion indicated by C, that is, the portion near the boundary with the large grain size region within the intermediate grain size region. The distribution has substantially no metal particles 10 in the large particle size region.

In this way, the metal particles 10 having the particle size distribution of the frequency distribution curve G1 are improved to the metal particles 10 having the particle size distribution of the frequency distribution curve G1a by, for example, having a mesh corresponding to the boundary particle size wX. This is possible by using a sieve to remove metal particles 10 having a particle size equal to or larger than the boundary particle size wX.

If the metal particles 10 having the particle size distribution of the frequency distribution curve G1a are used, the formation of the dense metal layer 20 can be further ensured because there are no metal particles 10 in the large particle size region that interfere with film formation. 5 is a block diagram showing the configuration of a cold spray device used in the method for forming a dense metal layer according to the first embodiment.

The cold spray device 50 includes a metal particle supply section 51 , a gas supply section 52 , a gas heating section 53 , and an injection section 54 .

The metal particle supply section 51 has a metal particle storage tank 51a that stores the metal particles 10 and a transfer pipe 51b that transfers the metal particles 10 from the metal particle storage tank 51a to the injection section 54.

The gas supply section 52 supplies gas such as helium or air to the injection section 54 . The gas heating section 53 heats the gas supplied from the gas supply section 52 before it flows into the injection section 54 . The gas heating section 53 is, for example, an electric heater or a heating device using high temperature gas.

The heating temperature is a temperature lower than the melting point of the metal particles 10 and a temperature effective for the cold spray method. For example, since copper has a temperature range in which it becomes brittle due to heat input, it is important to select the temperature conditions for both the base material 1 to be applied and the metal particles 10 to be used. Furthermore, since zinc and tin have low melting points, low-temperature spraying is preferable to high-temperature spraying. As described above, the heating temperature varies depending on the type of metal particles 10 and further varies depending on the particle size of the metal particles 10, but is approximately, for example, about 250 to 750°C.

The injection unit 54 accelerates the metal particles 10 supplied from the metal particle supply unit 51 with the gas supplied from the gas supply unit 52 and injects them. The flow velocity of the injected metal particles 10 is, for example, about 500 m/sec.

FIG. 6 is a conceptual graph showing the upper limit of the particle size within the intended range of metal particles and the dependence of the boundary particle size on the average particle size in the method for forming a dense metal layer according to the first embodiment. . The horizontal axis is the average particle size X, and the vertical axis is the magnification v and w of the average particle size of the upper limit of the particle size within the desired range and the boundary particle size, respectively. A solid line V indicates a magnification v, and a broken line W indicates a magnification w.

Cold spray is a method in which the metal particles 10 collide with the base material 1 at high speed at a temperature below their melting temperature, and the kinetic energy is used to form a film. For this reason, it is necessary that the heat capacity of the metal particles 10 is commensurate with the kinetic energy; if the heat capacity is too large, the kinetic energy may not be sufficient to relatively adhere the metal particles 10 to the base material 1. It's going to disappear.

For example, if the average particle size The boundary particle size wX under cold spray conditions corresponding to the particle size cannot be 7 times 40 μm.

That is, cold spraying is performed under conditions that are optimal for the average particle size X. On the other hand, since the heat capacity is proportional to the cube of the particle size with respect to an increase in the average particle size X, the range of the desired particle size range to which this condition can be applied becomes narrower, and the upper limit magnification v becomes smaller. The same applies to the magnification w of the boundary grain size. Therefore, as shown in FIG. 6, the dependence characteristic curve of the magnification v and the magnification w on the average particle diameter X has a downward-sloping shape.

In addition, in FIG. 6, the values of magnification v and magnification w are shown to be determined as one for each average particle size X, but in reality, they have a width, and the width is not shown in the diagram. Not yet.

The degree of width also becomes smaller as the average particle size X becomes larger. When the average particle diameter X is X1, that is, 2 μm, it is, for example, about plus or minus 1. Further, when the average particle diameter X is X3, that is, 40 μm, the difference is, for example, about plus or minus 0.4. The width also has the same tendency as the magnification v and the magnification w, and in the case of the average particle size X2, that is, 20 μm, it is, for example, about plus or minus 0.7.

Therefore, in this case, when the average particle diameter X is X1, that is, 2 μm, the magnification v is about 4 to 6, and the magnification w is about 6 to 8. However, even in this case, the difference between the magnification v and the magnification w is about 2. This point also applies below. When the average particle diameter X is X2, that is, 20 μm, the magnification v is about 2.8 to 4.2, and the magnification w is about 4.3 to 5.7. Further, when the average particle diameter X is X3, that is, 40 μm, the magnification v is about 1.6 to 2.4, and the magnification w is about 2.6 to 3.4.

Based on the above knowledge, etc., the steps of the method for forming a dense metal layer according to the present embodiment will be described below.

FIG. 7 is a flow diagram showing the procedure of the method for forming a dense metal layer according to the first embodiment.

First, the metal element and composition of the metal particles 10 used in the cold spray method (low temperature thermal spray method) are selected (step S01). In the case of a single metal element, the metal element is one of copper (Cu), zinc (Zn), tin (Sn), silver (Ag), aluminum (Al), gold (Au), or an alloy. In this case, use a combination of these. These metals are electrically conductive and have lower melting points than materials for structural members such as steel. Furthermore, the metal element of the metal particles 10 may be a copper alloy containing one or more of gold, silver, zinc, tin, and phosphorus.

Next, a target particle size of the metal particles 10 is set (step S02). That is, a target particle size X0 is set as a specification when manufacturing or procuring.

Here, the target particle size X0 is set, for example, to a particle size in the range of about 1 μm to about 40 μm, preferably in the range of about 1 μm to about 20 μm.

Next, metal particles are manufactured or procured using the target particle size X0 set in step S02 as the specification (step S03). The metal particles 10 can be produced by dry granulation or wet granulation, including one or more of spray granulation, melt granulation, shear granulation, electrolytic granulation, or a continuous process of these. As a result, atomized powder or electrolytic powder can be obtained.

Next, the frequency distribution of particle sizes of the manufactured metal particles 10 is measured (step S04). In addition, when procuring metal particles, in most cases, the frequency distribution of the particle size of the metal particles 10 after production is measured at the manufacturer and the records are provided, so the records can be used without having to measure again. .

Although not shown, if the frequency distribution of the particle size of the metal particles 10 after manufacture is not measured, the frequency distribution may be measured either at the receiving stage or at a subsequent stage, as described below. .

If the frequency distribution of particle diameters of the metal particles 10 after manufacture has been measured, the average particle diameter X based on the frequency distribution can be used as the average particle diameter. In the following explanation, if the frequency distribution of the particle size of the metal particles 10 after manufacture is not measured, it may be treated as if the target particle size X0 is the average particle size X for convenience until it is measured. .

Here, it is assumed that the particle size of the metal particles 10 is a particle size value obtained by measuring the particle size using a laser diffraction/scattering method.

A specific example of a device using the laser diffraction/scattering method is the Microtrac MT 3000II series (MicrotracBEL), and the particle size distribution was measured under the following measurement conditions (LOW-WET MT3000II MODE).

(1) Particle permeability; reflection (2) Deep medium refractive index: 1.333
(3) Measurement time: 30 seconds Regarding the shape of the particles, it was confirmed that, for example, spherical or spheroidal shapes are particularly excellent. However, the shape of the particles is not limited to these, and may be other shapes such as flakes.

Next, the aggregation state of the obtained metal particles 10 is determined and the aggregation state is canceled (step S05). Basically, as described above, the agglomerated state is removed by sieving. The mesh of the sieve may correspond to, for example, the average particle size X, or the boundary particle size wX. Further, if necessary, it may be further crushed using a ball mill or the like.

Next, conditions for sorting and checking the metal particles 10 are set (step S06). That is, for example, when metal particles 10 having a frequency distribution of the frequency distribution curve G1 shown in FIG. 3 are obtained, in order to obtain metal particles 10 having a frequency distribution of the frequency distribution curve G1a, the set conditions Sorting to remove metal particles 10 with a particle size larger than the particle size, or confirmation that metal particles 10 with a particle size of a set condition occur at a predetermined frequency, for example, 10% or less, or a set condition Conditions are set in order to confirm that the accumulation of metal particles 10 having a particle size equal to or larger than . Hereinafter, selection and confirmation in this sense will be referred to as selection and confirmation.

Here, for example, if a condition is set to remove particles with a particle size larger than vX, which is the maximum value of the particle size within the period range, or to remove particles with a particle size larger than the boundary particle size wX, specifically, , the value of the grain size vX or the boundary grain size wX is set in consideration of the dependence of the magnification v or the magnification w on the average grain size X shown in FIG. For example, when the average grain size X is 40 μm, the grain size vX is about twice 40 μm, or about 80 μm, and the boundary grain size wX is about three times 40 μm, or about 120 μm.

Next, the metal particles 10 are sorted and confirmed according to the sorting conditions set in step S06 (step S07). Specifically, if the set condition is, for example, to remove particles with a grain size larger than or equal to the boundary grain size wX, then the mesh corresponding to the boundary grain size wX, that is, the grains larger than or equal to the boundary grain size wX, is removed. Sorting is performed using a mesh with a size that does not allow particles of this size to pass through.

In addition, regarding the small particle size particles 12, similarly, a predetermined mesh is formed that allows only the small particle size particles 12 to pass through, or allows only the metal particles 10 whose diameter is smaller than the lower limit X/w of the particle size particles within the predetermined range to pass through. Separation and removal is possible by using a sieve.

Regarding the sorting of the metal particles 10, although the large particle size side and the small particle size side are removed in the same way in FIG. 3 etc., the purpose is mainly to remove the undesirable large particle size particles 13. It is said that That is, although the small diameter particles 12 that reduce the formation efficiency may be removed, at least the large diameter particles 13 must be removed.

As mentioned above, if the frequency distribution of the particle size of the metal particles 10 after manufacturing is not measured, the metal particles are The frequency distribution of particle sizes of 10 is measured. Of course, even if the frequency distribution of particle diameters of the metal particles 10 after manufacture is not measured, further measurement may be performed.

Next, conditions for performing cold spray using the cold spray device 50 are set (step S08). At this stage, since the average particle size X of the metal particles 10 is known through frequency distribution measurement, conditions that match this average particle size X are set.

Next, cold spray is performed using the cold spray device 50 under the conditions set in step S08 (step S09).

As described above, the particle size distribution of the metal particles 10 to be injected by the cold spray method is set to the optimum conditions for the average particle size By spraying, the dense metal layer 20 can be reliably formed on the surface of the base material 1 as the metal member 10.

[Second embodiment]
The second embodiment is a modification of the first embodiment, and defines the desired particle size distribution from a different perspective. Other points are similar to the first embodiment.

FIG. 8 is a graph showing the particle size distribution and cumulative particle size distribution of metal particles in the method for forming a dense metal layer according to the second embodiment. The horizontal axis shows the grain size in logarithmic form, the vertical axis shows the frequency (%) for the solid curve G3, and the accumulation (%) for the broken curve S3.

In this embodiment, the manufactured metal particles 10 are released from agglomeration by a sieving operation, and, for example, metal particles 10 in a large particle size region are sieved, or metal particles 10 in a large particle size region are not present. This has been confirmed.

As a result, if the accumulation of metal particles with a particle size larger than the particle size within the expected range, that is, the particle size exceeds vX, is 5% or less, it is determined to be good.

By using such criteria to limit the proportion of particles outside the desired range in the entire metal particles 10, the dense metal layer 20 can be reliably formed.

[Third embodiment]
The third embodiment is a modification of the first embodiment, and defines the desired particle size distribution from a different viewpoint. Other points are similar to the first embodiment.

FIG. 9 is a graph showing an example of the particle size distribution of the metal particles 10 and the particle size within the desired range in the method for forming a dense metal layer according to the third embodiment. The horizontal axis is the logarithmic particle size, and the vertical axis is the frequency (%).

In the frequency distribution curve G4 shown by G4 in FIG. 9, the frequency is distributed over a wide range around the average particle size X. That is, the kurtosis of the frequency near the average particle size X is low, and the distribution shape has short tails on both sides in the horizontal axis direction.

On the other hand, the frequency distribution curve GX according to the comparative example indicated by GX has a distribution shape in which the kurtosis of the frequency near the average particle size X is high, but has long tails on both sides in the horizontal axis direction.

Ideally, a distribution shape in which the kurtosis of the frequency near the average particle size X is high and the tails on both sides in the horizontal axis direction are short is a preferable distribution.

However, even if the kurtosis is low, the proportion of metal particles in the large particle size region is small or zero to suppress the factors that hinder the formation of the dense metal layer 20, and to keep the ratio within the desired range. By including a large amount of metal particles 10, the dense metal layer 20 can be formed efficiently.

Metal particles 10 having such a frequency distribution may be obtained as a result of manufacturing. Even in that case, a sieving operation is performed to release the metal particles 10 from agglomeration after production, and the sieving operation results in metal particles 10 with a predetermined particle size or more being below a predetermined accumulation, or metal particles 10 with a predetermined particle size being below a predetermined frequency. Confirm that it is.

Moreover, when large-diameter particles are present, the metal particles 10 in the large-diameter region can be removed by the above-mentioned sieving operation.

[Other embodiments]
According to each of the embodiments described above, a dense metal layer can be reliably formed on the surface of a metal member used in a liquid-contact environment.

Although the embodiments of the present invention have been described above, the embodiments are presented as examples and are not intended to limit the scope of the invention.

Moreover, the features of each embodiment may be combined.

Further, the embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention.

The embodiments and their modifications are included within the scope and gist of the invention as well as within the scope of the invention described in the claims and its equivalents.

DESCRIPTION OF SYMBOLS 1... Base material, 10... Metal particle, 11... Intended diameter particle, 12... Small particle diameter particle, 13... Large particle diameter particle, 20... Metal dense layer, 21... Attached part, 22... Non-adhered part, 23 ...Scattered particles after excavation, 30...Adhesion layer, 32...Drilling section, 50...Cold spray device, 51...Metal particle supply section, 51a...Metal particle storage tank, 51b...Transfer pipe, 52...Gas supply section, 53...Gas Heating section, 54... injection section

Claims (13)

In a method for forming a dense metal layer in a metal member used in a wetted environment,
Manufacturing the metal particles using an average particle size a step of producing and procuring metal particles to obtain the metal particles having an average particle size of X;
an agglomeration state release step for releasing the agglomeration state of the metal particles obtained in the metal particle production/procurement step; and an effective low -temperature spraying condition for the metal particles from which the agglomeration state has been released by the agglomeration state release step. remove the metal particles having a predetermined particle size or more larger than the upper limit particle size v a sorting/confirmation step of confirming that the metal particles having the upper limit particle size vX or more are less than or equal to a predetermined frequency;
After the screening and confirmation step, a low-temperature spraying step of spraying the metal particles onto the surface of the target member;
has
A method for forming a dense metal layer , wherein the screening/confirmation step includes a step of setting the upper limit grain size vX from the dependence of the magnification v on the average grain size X and the average grain size X. 2. The method for forming a dense metal layer according to claim 1, wherein the particle size of the metal particles is determined based on measurement using a laser diffraction/scattering method. 3. The method of forming a dense metal layer according to claim 1, wherein the conditions for the low-temperature spraying step are set based on the average particle size X. The method for forming a dense metal layer according to any one of claims 1 to 3, wherein the average particle size X is 1 to 40 μm. The metal according to any one of claims 1 to 4, wherein the predetermined grain size is a minimum value wX (however, the magnification w is a positive real number larger than 1) in a large grain size region. How to form a compact layer. When the average particle size The method for forming a dense metal layer according to claim 5 . 7. The method of forming a dense metal layer according to claim 5 , wherein in the frequency distribution of particle diameters of the metal particles, the frequency of the metal particles at the minimum value wX is less than 10% . The sorting/confirming step is a step of confirming that the metal particles having the upper limit particle size vX or more of the particle size within the desired range are less than or equal to the predetermined frequency, and in the cumulative particle size distribution, the metal particles having the upper limit particle size vX or more are The method for forming a dense metal layer according to any one of claims 1 to 6, wherein the method is determined to be good if the cumulative amount of grains having a grain size larger than vX is 5% or less . Any one of claims 1 to 8 , wherein the metal particles are metal particles containing one or more metal elements, metal alloy particles, or mixed particles thereof. The method for forming a dense metal layer described in . A claim characterized in that the metal element is one of copper (Cu), zinc (Zn), tin (Sn), silver (Ag), aluminum (Al), and gold (Au), or an alloy containing the same. Item 9. The method for forming a dense metal layer according to item 9 . 10. The method for forming a dense metal layer according to claim 9 , wherein the alloy is a copper alloy containing one or more of gold, silver, zinc, tin, and phosphorus (P) . In the low-temperature spraying step, a set value or an actual value of the temperature of the transfer gas for transporting the metal particles is lower than the melting temperature of the metal particles and is in the range of 250°C to 750°C. The method for forming a dense metal layer according to any one of claims 1 to 11 . In a method for forming a dense metal layer in a metal member used in a wetted environment,
Manufacturing the metal particles using an average particle size a step of producing and procuring metal particles to obtain the metal particles having an average particle size of X;
an agglomeration state release step for releasing the agglomeration state of the metal particles obtained in the metal particle production/procurement step; and an effective low-temperature spraying condition for the metal particles from which the agglomeration state has been released by the agglomeration state release step. a sorting step of removing the metal particles having a predetermined particle size or more, which is larger than the upper limit particle size vX (however, the magnification v is a positive real number larger than 1) of the particle size within the expected range in which the metal particles exist;
After removing the metal particles having a predetermined particle size or more larger than the upper limit particle size vX in the sorting step, a confirmation step of confirming the average particle size X1 of the metal particles after the removal;
a condition setting step of setting the low temperature thermal spraying conditions based on the average particle size;
a low-temperature spraying step of performing the low-temperature spraying of the metal particles onto the surface of a target member based on the low-temperature spraying conditions set in the condition setting step;
has
A method for forming a dense metal layer, wherein the sorting step includes a step of setting the upper limit grain size vX from the dependence of the magnification v on the average grain size X and the average grain size X.

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