JP2015151622A - Powder for flame spray, production method of powder for flame spray, and production method of sprayed coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide powder for flame spray capable of forming a coating at an excellent deposit rate by using a non-hot spray method, even when the powder for flame spray contains ceramics, and to provide a production method thereof.SOLUTION: Powder for flame spray in an embodiment, which is powder for flame spray for forming a coating by using a non-hot spray method, is constituted of secondary particles formed by aggregating primary particles, and the primary particle is constituted by including a metal layer on the surface of a ceramic particle.

Description

  The present invention relates to a thermal spraying powder, a thermal spraying powder manufacturing method, and a thermal spray coating manufacturing method.

  Conventionally, the thermal spraying method is a film forming method capable of efficiently forming a film of a wide range of materials from a low melting point material such as a resin to a high melting point material such as ceramics. This thermal spraying method is mainly used in a wide range of fields such as energy equipment such as a power plant that requires a thick film of 100 μm or more, transportation equipment such as automobiles, airplanes and ships, printing rolls and construction machinery.

  As the thermal spraying method, a flame spraying method such as a flame spraying method, in which a thermal spraying powder is heated and melted to a temperature higher than its melting point, and the droplets are transported by a high-speed gas flow to collide with a substrate, is widely used. Yes. However, in recent years, a non-melting spray method such as a cold spray method and a warm spray method in which a thermal spray powder is made to collide with a substrate at a high speed exceeding the speed of sound in a solid state has been developed and put into practical use. In the non-melting spray method, it is not necessary to melt the thermal spraying powder. Therefore, oxidation or phase transformation of the thermal spraying powder material due to high temperature heating can be suppressed, and a film can be formed without impairing the function of the thermal spraying powder material. Many of the materials used in this method are low melting point metals such as copper. On the other hand, an example of using a cermet or the like, which is a composite material of metal and ceramics, to form a functional coating that could not be formed by a thermal spraying method has been reported.

JP 2012-193441 A JP 2012-192401 A

  However, when using a thermal spraying powder containing a high-melting-point, high-hardness material such as ceramics and forming a coating using the non-melt spray method described above, it is necessary to select the thermal spraying powder material appropriately. The adhesion rate to the base material is lowered. Therefore, it is difficult to form a film with a high yield.

  The present invention has been made in order to solve the above-described problems, and even when the thermal spraying powder contains ceramics, the thermal spraying can form a film with an excellent adhesion rate by using the non-melting spray method. An object of the present invention is to provide a powder for use and a method for producing the same.

  The thermal spraying powder of the embodiment is a thermal spraying powder for forming a film using a non-melting spray method, and is composed of secondary particles in which primary particles are aggregated, and the primary particles are ceramic particles. It is characterized by comprising a metal layer on the surface.

It is sectional drawing which shows typically the powder for thermal spraying of embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing a thermal spraying powder 1 according to an embodiment. The thermal spraying powder 1 of the embodiment shown in FIG. 1 is a material for forming a film using a non-melting spray method. The non-thermal spraying method is a method in which the thermal spraying powder 1 is heated to a temperature equal to or lower than its melting point or softening point as required, and is allowed to collide with a substrate in a solid state to form a coating. The thermal spraying powder 1 is composed of secondary particles in which primary particles of ceramic particles 2 having a metal layer 3 on the surface are aggregated.
The primary particle refers to one ceramic particle 2 having a metal layer 3 on the surface, and the secondary particle refers to a particle in which a plurality of primary particles are aggregated.

  In the thermal spraying powder 1 of the present embodiment, the material of the ceramic particles 2 is a material whose melting point is higher than that of the elements constituting the metal layer 3. In the ceramic material, since the melting point of the metal material used as the metal layer 3 is about 1000 ° C., the melting point is preferably 1000 to 3000 ° C., more preferably 1500 to 3000 ° C. Further, the Vickers hardness of the ceramic particles 2 is preferably 10 to 100 GPa so as not to be plastically deformed upon collision with the substrate.

  As the ceramic material, for example, metal oxides, metal carbides, metal borides, metal nitrides, metal sulfides and the like are preferable from the viewpoints of wear resistance, heat resistance, environment resistance, and the like. The ceramic material may be a composite oxide, composite carbide, composite boride, composite nitride or composite sulfide of two or more metals. In addition, the ceramic materials may be used alone or in combination of two or more.

  As a metal element constituting such a ceramic material, for example, aluminum, chromium, tungsten, gadolinium, molybdenum and the like are preferably used. The ceramic material can be selected depending on the intended use of the resulting film. For example, tungsten carbide, chromium carbide, aluminum oxide, gadolinium oxide, molybdenum boride, molybdenum sulfide and the like are suitable.

The ceramic particles 2 may be particles having the above-described ceramic material as a main component, and may contain other components as long as the effects of the present embodiment are not impaired. Ceramic particles 2, for example, comprise a ceramic material described above 80 wt% or more, as other _components, can be used ceramic particles 2 containing SiO _2, TiO 2, Fe, Cr, C and the like.

  The average particle diameter of the ceramic particles 2 constituting the primary particles is preferably 0.1 to 10 μm, more preferably 1 to 5 μm. When the thermal spraying powder 1 is used and a film is formed using the non-melting spray method, the adhesion is affected by the surface activity in the powder state. In general, the finer the powder, the larger the surface area relative to the volume, the more the chemical activity on the surface is improved, and the adhesion is improved. In the thermal spraying powder 1, the thickness of the metal layer 3 is smaller than the average particle diameter of the ceramic particles 2. Therefore, when the average particle diameter of the ceramic particles 2 is in the above-described range, the chemical activity of the surface of the thermal spraying powder 1 can be improved and the adhesion to the substrate can be improved. The average particle diameter is a value measured by a laser diffraction particle size distribution measuring device, which indicates an average particle diameter with a 50% diameter that is a value of 50% relative particle amount in the particle size distribution curve.

  The metal layer 3 is deformed when the thermal spraying powder 1 and the base material collide to adhere the thermal spraying powder to the base material and to make primary particles adhere to each other. The metal material constituting the metal layer 3 is a material having a toughness sufficient for plastic deformation when the thermal spraying powder 1 collides with the substrate. The Vickers hardness of the metal layer 3 is preferably 5 GPa or less in order to be plastically deformed when the base material collides. Moreover, it is preferable that melting | fusing point of a metal material is 800-1600 degreeC.

  As the metal material as described above, for example, a metal whose main component is nickel, copper, or iron can be used. Examples of such metal materials include pure metals such as nickel, copper, and iron, and alloys obtained by adding other metal elements or non-metal elements to the above-described pure metals, such as nickel-based alloys, copper alloys, and iron-based alloys. Can be mentioned. The metal material can be appropriately selected from the viewpoints of bonding with the above-described ceramic material, adhesion of the metal layer 3, film forming properties, use of the sprayed coating to be manufactured, and the like.

  The thickness of the metal layer 3 is preferably 0.01 to 5 μm, more preferably 0.1 to 3 μm. The adhesiveness to the base material of the powder 1 for thermal spraying is improved because the thickness of the metal layer 3 is 0.01 micrometer or more. Moreover, it is possible to express the original characteristic of ceramic particles by being 5 micrometers or less.

  The average particle diameter of the secondary particles constituting the thermal spraying powder 1 is preferably 10 to 100 μm, more preferably 10 to 50 μm. The thermal spraying powder 1 has a secondary particle having an average particle diameter of 10 μm or more, so that it can be made to collide with the base material without being scattered by the high-pressure gas flow. The surface metal layer 3 has a mass sufficient for plastic deformation. Moreover, by being 100 micrometers or less, it is possible to make it collide with a base material at a high speed sufficient for plastic deformation of the metal layer 3 using a high-pressure gas flow. From such a viewpoint, the average particle size of the secondary particles is preferably designed appropriately in consideration of the specific gravity, melting point, hardness, etc. of the ceramic material and metal material constituting the thermal spraying powder 1. The shape of the secondary particles is preferably substantially spherical in order to cause each particle constituting the thermal spraying powder 1 to collide with the substrate at a substantially uniform speed, such as an elliptical spherical shape, a cylindrical shape, etc. There may be.

  The thermal spraying powder 1 of the present embodiment adheres to the base material by plastic deformation of the metal layer 3 on the surface of the primary particles when it collides with the base material. Furthermore, since the minute gaps between the agglomerated primary particles are filled with the plastically deformed metal when colliding with the base material, adhesion of the sprayed coating to the base material is improved. Therefore, when the thermal spraying powder 1 is applied to the non-melting spray method, the thermal spray coating can be formed with excellent adhesion and high yield.

  When the thermal spraying powder 1 of the present embodiment is used for wear-resistant coating in, for example, printing rolls and construction machines, it is preferable to use a material having as high a hardness as possible as the ceramic particles 2. Therefore, as the ceramic particles 2, for example, ceramics such as tungsten carbide, chromium carbide, and aluminum carbide, or ceramic materials containing these as a main component are preferable. Further, as a metal material, nickel is a main component in consideration of the bondability with a ceramic material, the bondability of the metal layer 3, the ease of deformation, the film formability (ease of plating), and the corrosion resistance. It is particularly preferred to use a metal that does this.

  When the thermal spraying powder 1 of the present embodiment is used for neutron absorption, it is preferable to use a material having a large neutron collision cross section as the ceramic particles 2. Therefore, it is preferable to use gadolinium oxide as the ceramic particles 2. In this case, as the metal material, copper and nickel are preferable from the viewpoints of bondability with gadolinium oxide, bondability of the metal layer 3, ease of deformation, and film formability.

  When the thermal spraying powder 1 of the present embodiment is used for reducing friction of sliding parts in, for example, turbine members of power plants, automobiles, airplanes, ships, etc., a material having a low friction coefficient is used as the ceramic particles 2. Is preferred. Therefore, it is preferable to use molybdenum boride or molybdenum sulfide as the ceramic particles 2. In this case, copper and nickel are preferable as the metal material from the viewpoints of bonding with ceramics, bonding of the metal layer 3, ease of deformation, and film formability.

(Method of forming powder for thermal spraying)
Next, the manufacturing method of the thermal spraying powder 1 of the embodiment will be described.
The manufacturing method of the thermal spraying powder 1 according to the embodiment includes a step of forming a metal layer 3 on the surface of the ceramic particle 2 to form primary particles, and a step of aggregating the primary particles to form secondary particles. It has.

  In the step of forming the primary particles, the metal layer 3 is formed on the surface of the ceramic particles 2 using a plating method such as electrolytic plating or electroless plating or chemical vapor deposition. By these methods, a homogeneous metal layer 3 having good adhesion to the ceramic particles 2 can be formed on the surface of the ceramic particles 2.

  In the step of producing secondary particles, the primary particles obtained above are adhered and aggregated. As a method of aggregating the primary particles, a method of heat treatment at a high temperature or a method of pressure-molding the primary particles can be used.

  The method for heat-treating the primary particles is not particularly limited. For example, a method of pressure sintering using a high temperature isostatic pressing (HIP) furnace or a method of heating in a firing furnace is used. The heating temperature is a temperature at which the primary particles can be adhered by deforming the metal layer 3 on the surface of the primary particles, and is a temperature below the melting point of the metal material. For example, when nickel is used as the metal material, the heating temperature is preferably 800 to 1500 ° C, more preferably 900 to 1300 ° C.

  In order to set the average particle size of the secondary particles in the above-described range, the average particle size of the obtained secondary particles is estimated from the average particle size of the primary particles stacked during heating, the layer thickness, the mass, and the like. What is necessary is just to determine the lamination | stacking thickness and volume of the primary particle at the time of heating. Further, the primary particles may be pressed and pressure bonded simultaneously with or after the heat treatment. Further, in order to control the shape of the secondary particles to form, for example, a substantially spherical shape, a method of removing the corners by ball milling, a stamp mill, or the like can be used.

  Thus, the thermal spraying powder 1 composed of the secondary particles having the above average particle diameter can be manufactured. Moreover, after adhering primary particles by heat processing, you may crush and control the average particle diameter of a secondary particle to the above-mentioned range.

  In the method of pressure-molding primary particles, the primary particles are pressed to form a green compact and then crushed. In this case, the primary particles are pressurized by, for example, a press, a cold isostatic pressing (CIP) device, a pressurizer, or the like. The applied pressure is a pressure that can deform the metal layer 3 on the surface of the primary particles and adhere the primary particles to each other, and can be appropriately changed according to the material of the ceramic particles 2 and the metal layer 3. For example, when nickel is used as the metal material, the applied pressure is preferably 10 to 800 MPa, more preferably 50 to 400 MPa.

  Next, the green compact to which the primary particles are adhered is crushed by a ball mill, a stamp mill or the like to form secondary particles having the above average particle diameter.

  Using the thermal spraying powder 1 of the present embodiment thus obtained, a thermal spray coating can be formed as follows, for example, by a cold spray method.

  High pressure gas such as compressed air, inert gas such as pressurized helium and nitrogen is heated and supplied to the inside of a cold spray gun which is a thermal spraying device. Further, the thermal spraying powder 1 of the present embodiment is supplied into the cold spray gun. The supplied thermal spraying powder 1 is heated and accelerated by the high-pressure gas. The heated and accelerated thermal spraying powder 1 is ejected from a nozzle of a cold spray gun and collides with a base material which is an object to be sprayed to form a thermal spray coating. For example, the pressure and temperature of the high-pressure gas in forming the thermal spray coating are appropriately adjusted depending on the melting point of the material constituting the thermal spray powder, the average particle diameter of the thermal spray powder, and the like. For example, when a material containing tungsten carbide is used as the ceramic and nickel is used as the metal material, the pressure of the high pressure gas is preferably about 0.5 to 5 MPa, and the temperature of the high pressure gas is preferably about 300 to 1000 ° C. Moreover, it is preferable that the distance (spraying distance) from the nozzle tip of a cold spray gun to a base material is 5-100 mm, and the film thickness of the sprayed coating to be formed is 50-500 micrometers although it depends on a use. Is preferred.

  As described above, according to the thermal spraying powder of the present embodiment, when used in a method such as a non-melting spray method, in which the thermal spraying powder is made to collide with the base material without being melted, the film is deposited. Therefore, it is possible to form a film with a high yield.

Next, examples will be described.
Example 1
As an example of the thermal spraying powder, a wear resistant coating application is considered, and a primary particle is formed by forming a nickel layer having a thickness of 3 μm on the surface of tungsten carbide having an average particle size of 10 μm by an electroless plating method. The primary particles were filled in an alumina box and then aggregated by heating at 900 ° C. for 60 minutes in a firing furnace. At this time, secondary particles were formed into a substantially spherical shape having an average particle diameter of 40 μm by appropriately applying vibration to the particles.

  The spray powder thus obtained was sprayed at a right angle using a non-melting spray device (spray gun) using compressed air of 1 MPa called a low pressure type at a preheating temperature of the spray powder of 500 ° C. In this state, a film was formed on a stainless steel substrate at a spraying distance of 10 mm. As a result, 15% or more of the injected thermal spraying powder adhered to the substrate. In addition, the adhesion rate to the base material of the powder for thermal spraying was computed from ratio with the weight increase amount of the base material with respect to the supplied powder.

(Example 2)
Using the same material system as in Example 1, that is, tungsten carbide as the ceramic particles and nickel as the metal, a nickel layer having a thickness of 3 μm was formed on the tungsten carbide surface by chemical vapor deposition. The primary particles were packed in an alumina box and aggregated by heating at 900 ° C. for 60 minutes in a firing furnace. At this time, the secondary particles were formed into a substantially spherical shape having an average particle diameter of 40 μm by appropriately vibrating the particles. The thermal spraying powder thus obtained was prepared by controlling the average particle size of the secondary particles to about 40 μm. Using this thermal spraying powder, a film formation test was performed under the same conditions as in Example 1. As a result, in Example 2, 38% of the injected thermal spraying powder adhered to the substrate.

(Examples 3 and 4)
The same material system as in Example 1 was used. In Example 3, a nickel layer having a thickness of 3 μm was formed on the tungsten carbide surface by an electroless plating method, and then the primary particles were filled in an alumina box and heated at 900 ° C. for 60 minutes in a firing furnace. And fired. Thereafter, the powder was pulverized by a stamp mill to control the average particle size of the secondary particles to 40 μm to prepare a thermal spraying powder. Further, in Example 4, the primary particles after plating in Example 3 were pressure-molded at 50 MPa for 1 minute using a pressure press to form a green compact, and then crushed into secondary particles. Was controlled to 40 μm to prepare a powder for thermal spraying. Using the thermal spraying powder thus obtained, a film formation test was performed under the same conditions as in Example 1.
As a result, in Example 3, 48% of the injected thermal spraying powder adhered to the substrate in Example 4, and it was found that the secondary particle forming method of this example was effective.

(Comparative Example 1)
A powder for thermal spraying is created by simply mixing tungsten carbide with an average particle size of 40 μm as a ceramic material and nickel powder with an average particle size of 40 μm as a metal at a weight ratio (tungsten carbide / nickel powder) of 80% / 20%. did. Using this thermal spraying powder, a film formation test was performed under the same conditions as in Example 1. As a result, in Comparative Example 1, only 7% of the charged powder adhered to the substrate.

(Comparative Example 2)
A nickel layer having a thickness of 3 μm is formed by electroless plating on the surface of tungsten carbide having an average particle diameter of 10 μm, and a thermal spraying powder (primary particles) that is not subjected to an agglomeration process is used under the same conditions as in Example 1. A membrane test was performed. As a result, the adhesion rate was only 3%, and it became clear that the adjustment of secondary particles by the final aggregation of the present invention has an important effect.

(Comparative Example 3)
Using the same material system as that of Example 1, a nickel layer having a thickness of 10 μm was formed on the ceramic surface by a physical vapor deposition method using an electron beam to produce primary particles. The primary particles were filled in an alumina box, heated in a firing furnace at 900 ° C. for 60 minutes, and aggregated to prepare a thermal spraying powder in which the average particle size of the secondary particles was controlled to about 40 μm. Using this thermal spraying powder, a film formation test was performed under the same conditions as in Example 1. As a result, in Comparative Example 2, the adhesion rate was only 8%.

  The result of Comparative Example 3 is that it is difficult to form a metal layer on the entire surface of the ceramic particles by a method such as physical vapor deposition using an electron beam, and an interface where the ceramic particles are in contact with each other is formed even after aggregation. It is believed that there is. When such an interface is formed, cracking occurs at the fragile interface during film formation, and the film is finally peeled off starting from this crack, so that the adhesion rate is estimated to be low. Therefore, it was found that a film forming method with good throwing power, such as a plating method and chemical vapor deposition in the examples, is suitable as a method for forming the metal layer on the ceramic particle surface.

  Thus, it was found that by using the thermal spraying powder of the example, a high adhesion rate can be realized even by the non-melt spray method.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Thermal spraying powder, 2 ... Ceramic particle, 3 ... Metal layer.

Claims (10)

A thermal spraying powder for forming a film using a non-melt spray method,
Composed of secondary particles in which primary particles are aggregated,
The said primary particle is equipped with the metal layer on the surface of ceramic particle | grains, The powder for thermal spraying characterized by the above-mentioned.   2. The thermal spraying powder according to claim 1, wherein the ceramic particles have an average particle size of 0.1 μm to 10 μm.   The thermal spraying powder according to claim 1 or 2, wherein the metal layer has a thickness of 0.01 µm or more and 5 µm or less.   4. The thermal spraying powder according to claim 1, wherein an average particle size of the secondary particles is 10 μm or more and 100 μm or less. 5.   The thermal spraying powder according to any one of claims 1 to 4, wherein the metal layer is formed by a plating method or a chemical vapor deposition method.   The thermal spraying powder according to any one of claims 1 to 5, wherein the ceramic particles include at least one selected from tungsten carbide, chromium carbide, aluminum oxide, and gadolinium oxide.   The thermal spraying powder according to claim 1, wherein the metal layer contains iron, copper, or nickel as a main component.   The ceramic particles include at least one selected from tungsten carbide, chromium carbide, aluminum oxide, gadolinium oxide, molybdenum boride, and molybdenum sulfide, and the metal layer is mainly composed of copper or nickel. The thermal spraying powder according to any one of claims 1 to 7. A method for producing a thermal spraying powder for forming a film using a non-melting spray method,
Forming a metal layer on the surface of the ceramic particles to form primary particles;
And a step of agglomerating the primary particles to form secondary particles. A method for producing a thermal spraying powder, comprising: Heating the thermal spraying powder according to any one of claims 1 to 8 at a temperature lower than a melting point of an element constituting the metal layer;
And a step of transporting the heated powder for thermal spraying with a high-pressure gas stream to collide with a substrate.

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