JP2006052449A - Cold spray coating film formation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cold spray coating film formation method which can produce a coating film having a high hardness, a high density, and uniform properties throughout the entire coating film. <P>SOLUTION: This cold spray coating film formation method comprises generating a supersonic stream of a gas having a temperature lower than the melting or softening temperature of a spray material, throwing the spray material into the supersonic stream, and colliding the spray material in a solid phase against a substrate at a high speed to form the coating film, wherein a raw material powder for forming the coating film is prepared by mixing a coating film forming powder having a particle diameter of 5 to 50 μm with a peening powder having a particle diameter of 100 to 1,000 μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, a gas having a temperature lower than the melting point or softening temperature of the thermal spray material is converted into a supersonic flow, the thermal spray material is introduced into the supersonic flow, and the coating is applied to the substrate at a high speed in a solid state. The present invention relates to a method for forming a cold spray film.

  Generally, a technique for forming a film having excellent corrosion resistance and wear resistance on the surface of a casting mold or roll in an iron making process is known in order to extend the life. Means for plating or spraying metal are used. However, the film formed by plating has a disadvantage that a cermet material excellent in wear resistance cannot be applied over a large area, and cracks are likely to occur when the hardness is increased to HV300 or higher. On the other hand, since a coating by thermal spraying is oxidized during thermal spraying, it is difficult to form a dense metal, alloy, or cermet coating, and there is a problem that conductivity and thermal conductivity are low.

In recent years, “cold spray” has attracted attention as a new thermal spraying process for solving the above-described problems of the film forming method. As described in Non-Patent Document 1 and Non-Patent Document 2, this cold spray is a supersonic flow of a gas having a temperature lower than the melting point or softening temperature of the material powder, Is a technique in which particles of the above material are introduced into the substrate and collided with the base material in the solid state to form a film. Here, the material powder is a metal, an alloy, an intermetallic compound, ceramics, or the like, and the upper limit of the temperature of the working gas is the melting point or lower or the softening temperature or lower. The softening temperature of the material powder is defined as a temperature at which the strength or hardness of the material powder is half of the strength or hardness at room temperature.
As described in Non-Patent Documents 1 and 2, cold spray is a technique for forming a film by colliding a material powder against the surface of a substrate at a supersonic speed in a solid state with the configuration shown in FIG. is there. That is, a high-pressure working gas supplied from a gas source (air, nitrogen, helium, etc.) is branched into two paths, and one working gas passes through a gas heater and is at room temperature or higher than the melting point or softening temperature of the material powder. After being heated to a low temperature, it is supplied to the working gas supply hole of the cold spray device. The other working gas is supplied to the powder supply device, and is supplied to the powder supply hole of the cold spray device together with the material powder as a carrier gas. The working gas and material powder supplied to the inlet of the cold spray nozzle from this working gas supply hole and powder supply hole become supersonic flow through the tip and throat, and are ejected from the nozzle outlet at the tip of the divergent part. The
In this cold spray, the temperature of the working gas that heats and accelerates the material particles is significantly lower than the conventional plasma spraying method, flame spraying method, high-speed flame spraying method, etc. The substrate is allowed to collide with the substrate at a high speed (speed range of 300 to 1000 m / s), and the film is formed by causing plastic deformation of the substrate and particles by the energy. The film thus obtained has excellent properties of being dense and having high density, high thermal conductivity and electrical conductivity, little oxidation and thermal alteration, and good adhesion.
Tsuji, “New Spray Process Cold Spray”, Thermal Spray Technology, Vol. 20, No. 2, Sangyo Publishing Co., Ltd., August 30, 2000, p32-41 Tsuji, "Cold Spray Technology", Thermal Spray Technology, Vol. 21, No. 3, Sangyo Publishing Co., Ltd., February 5, 2002, p29-38

The film formation method by cold spray is satisfactory in terms of film forming operation and the obtained film performance, but the product film is required to have higher wear resistance, higher thermal conductivity, and conductivity. is there. For example, a continuous casting mold or a conductor roll in an iron making process.
The present invention has been made to meet such demands, and since it has high hardness and high density, it is possible to obtain a film having excellent wear resistance, thermal conductivity, and conductivity, and over the entire thickness of the film. It is an object of the present invention to provide a method for forming a cold spray film capable of obtaining a uniform property.

The gist of the present invention for solving the above problems is as follows.
(1) A gas having a temperature lower than the melting point or softening temperature of the thermal spray material is made into a supersonic flow, the thermal spray material is introduced into the supersonic flow, and the coating is made by colliding with the substrate at a high speed in the solid state. In the method of forming a cold spray film to be formed, a film is formed using a raw material powder obtained by mixing a raw material powder having a particle size of 5 to 50 μm and a peening powder having a particle size of 100 to 1000 μm. Method.
(2) A gas having a temperature lower than the melting point or softening temperature of the thermal spray material is changed to a supersonic flow, the thermal spray material is introduced into the supersonic flow, and the coating is applied to the substrate at a high speed in a solid state. In the forming method of the cold spray film to be formed, a gas / powder supply part in front of the nozzle throat part and / or a divergent part behind the throat part or a plurality of powder supply holes provided in a parallel part following the divergent part, a particle diameter of 5 to 50 μm A method for forming a cold spray film, comprising: forming a film by supplying the film raw material powder and a peening powder having a particle size of 100 to 1000 μm from separate powder supply holes.
(3) A coating raw material powder having a particle size of 5 to 50 μm is supplied from a powder supply hole provided in a chamber part in front of the nozzle throat part or in a divergent part behind the throat part or in a parallel part following the divergent part, and around the nozzle ejection hole. The method for forming a cold spray coating according to (2), wherein a coating is formed by separately supplying peening powder having a particle diameter of 100 to 1000 μm from a powder supply hole provided in the slit portion.
(4) A gas having a temperature lower than the melting point or softening temperature of the thermal spray material is made into a supersonic flow, the thermal spray material is introduced into the supersonic flow, and the coating is made by colliding with the substrate at a high speed in a solid state. The method for forming a cold spray film according to (2) or (3), wherein the method for forming a cold spray film includes a nozzle for forming a raw material and a nozzle for shot peening, respectively.
(5) The method for forming a cold spray coating according to any one of (1) to (4), wherein the Vickers hardness of the peening powder is 400 HV or more higher than the Vickers hardness of the coating material powder.
(6) The method for forming a cold spray film according to any one of (1) to (5), wherein the peening grains are a high hardness Fe-based alloy or WC.

  According to the method of the present invention, since a peening effect is imparted to the film formed almost simultaneously with the spray, and this effect continues throughout the film thickness, an extremely dense and highly uniform film having a uniform property is efficiently produced. Can get well.

Hereinafter, preferred embodiments of the present invention will be described.
First, in the present invention, when forming a film by cold spray, as a thermal spray powder, a film raw material powder with a particle size of 5 to 50 μm and a peening powder with a particle size of 100 to 1000 μm (depending on the particle size, it becomes a particle form, A powder mixed with this is referred to as a powder). The film raw material powder is a powder of components constituting the film after thermal spraying, and any one of metals such as Cu, Al, Cr, Ni, Mo, Fe, Nb, and alloys thereof may be selected. The coating raw material powder is optimally one having a particle size of 5 to 50 μm, but this does not change from the particle size range of the raw material powder used in ordinary cold spray. The desired film can be formed on the substrate under the spraying conditions.

In addition, the peening powder is mixed with the film raw material powder or sprayed separately, but the film raw material powder collides with the base material and at least part of it remains on the base material to form a film. The peening powder has a slow flight speed due to the particle size relationship, so it collides with the base material slightly later than the coating raw material powder and falls without adhering to the coating already formed. Therefore, as the peening powder, a high-hardness Fe-based alloy (for example, 1C-1.5Cr-Fe or the like) or WC particles, which is a peening powder used in normal shot peening, is preferable. The particle size of the peening powder needs to be larger than the particle size of the film raw material powder, and the particle size range is 100 to 1000 μm. By using particles having such particle diameters and components, the coating can be densified, and a peening effect that increases density and hardness is exhibited. If the particle size of the peening powder is smaller than 100 μm, the peening powder remains in the coating, and the powder larger than 1000 μm has a too large particle size and is difficult to supply from the film forming nozzle.
Furthermore, the mixing ratio of the peening powder and the coating raw material powder needs to be a larger amount of the coating raw material powder, but the mixing ratio of the peening powder is generally within the range of 5 vol% to 20 vol%. Is desirable.

  The hardness of the peening powder needs to be greater than the hardness of the film raw material powder, but the difference in hardness between the two is that the peening powder has a Vickers hardness of 400 HV or more larger than the film raw material powder. It is desirable to demonstrate If the hardness difference is less than 400 HV, the hardness of the peening powder is too low and the peening effect may not be exhibited even if it collides with the coating. Moreover, it is preferable that this hardness difference does not exceed 3000 HV at the maximum. In the present invention, even if the coating raw material powder is a soft material having a low hardness, it can be made into a coating having a sufficient hardness by mixing the peening powder, and it is as low as previously impractical. Even a coating material powder having a hardness can be formed as a coating.

  When the above mixed powder is actually sprayed onto the substrate to form a film on the surface, an appropriate cold spray device gun is used. As this equipment, the cold shown in FIG. A spray gun may be used. In the apparatus of FIG. 2, the raw material powder and the peening powder are mixed at the position of the powder supply device, and this is sent to the spray device from the powder supply hole by the working gas which is a carrier gas, and is operated at a predetermined pressure supplied to the nozzle. The gas causes supersonic flow through the taper and throat, and is jetted onto the substrate from the nozzle outlet at the tip of the divergent section.

FIG. 1 shows an example of a gun of a cold spray device that is more suitable for carrying out the present invention, without being limited to the case where the present invention is implemented using an existing cold spray device.
As shown in the figure, the spray section of the cold spray nozzle basically includes a tapered portion 1, a throat section 3, a divergent section 2, and a parallel section 19. Two powder supply holes 4 are provided opposite to each other across the injection shaft in the thick parallel portion on the outlet side (injection direction) of the divergent portion 2. Further, the parallel part has a structure in which an injection nozzle part 5 is attached to the outlet side of the powder supply hole 4, and the injection nozzle part 5 formed of a long pipe can be replaced with a thick part of the parallel part. The nut 20 is attached so as to maintain airtightness.
Further, the tip 1 of the cold spray nozzle and the gas / powder supply unit 7 are fixed by a nut 8 via a honeycomb-shaped commutator 21 and a gasket 6 for adjusting the gas flow. The gas / powder supply unit 7 is provided with a working gas supply hole 9, a powder supply hole 10, a temperature measurement hole 11 and a pressure measurement hole 12, and an appropriate gas supply source, powder supply source, temperature measurement mechanism and pressure, respectively. Connected to the measurement mechanism. In the present invention, it is preferable to provide a honeycomb-shaped commutator 21 for adjusting the gas flow, but it is not essential and is not limited to the honeycomb shape.
Further, in order not to clog the commutator 21, a pipe may be inserted as shown in FIG. 2 to bring the position where the coating material and / or peening powder is mixed with the working gas to the first detail.

  When the film forming method of the present invention is carried out using the apparatus of FIG. 1, first, the working gas is supplied from the working gas supply hole 9, and the peening powder and the desired film raw material powder are supplied from the powder supply hole 4 or 10. Supplied. The temperature and pressure of the working gas are measured through the temperature measurement hole 11 and the pressure measurement hole 12, and are controlled so that they are within a set range, specifically, a range of 0 to 700 ° C. and 1 to 6 MPa. .

  The working gas increases in speed at the outlet side of the taper 1, reaches the speed of sound at the throat 3 and further expands at the divergent part 2 to decrease the pressure to about atmospheric pressure, and accelerates to supersonic speed. Expands at the divergent portion 2 and the pressure decreases, so that a negative pressure occurs at the position of the powder supply port 4. Therefore, the peening powder and the coating material powder can be supplied from the powder supply port 4 together with the supply gas at a pressure as low as about 0.2 MPa. The peening powder is mixed with the film raw material powder, and then accelerated and heated by the working gas in the spray nozzle portion 5 to become a supersonic flow and ejected from the outlet, and collides with the base material to densify the film. During film formation, the film raw material powder that collided with the base material first forms a film, and the peening powder that arrives with a slight delay collides with this film to peen the film, increasing its hardness and densifying the film. To. As a result of repeating the above peening by spraying the mixed powder a plurality of times to a predetermined thickness, the coating has a dense property with uniform hardness over the entire thickness.

In the cold spray equipment shown in FIG. 1, two powder supply ports 4 are provided in the parallel portion on the outlet side of the divergent portion of the cold spray nozzle. However, the number of the powder supply ports 4 may be one, depending on circumstances. May be 3 or more. When providing a plurality of supply ports 4, peening powder is supplied from at least one supply port without supplying peening powder from all of the supply ports 4, and film raw material powder is supplied from at least one other supply port. It is possible to use it by supplying.
Further, as shown in FIG. 4, the peening powder may be supplied from (a) the powder supply hole 4 or 9 provided in the slit portion 22 around the nozzle ejection hole, or (b) from the adjacent nozzle provided separately. . In this case, since the peening powder speed may be low, a supply gas having a low pressure of about 0.2 MPa may be used.
As described above, when the film raw material powder and the peening powder are supplied from one nozzle, there is an advantage that the installation of the apparatus is simple and the film forming conditions can be easily set. On the other hand, when separate nozzles are provided for film formation and peening, there is a merit that the possibility of peening powder mixing into the film is reduced.
Using the above cold spray nozzle, the formed film can have a porosity of 2% or less and a metal oxide of 0.001 to 1%. By specifying the porosity and oxide amount of the film within such a low range, it is possible to obtain a film having excellent characteristics such as being dense and less oxidized and having a conductivity of 90% or more of the raw material powder.

The film densification process according to the present invention will be described with reference to FIG.
The film raw material powder and the peening powder are jetted simultaneously. (A) Since the coating raw material powder is soft, when it collides with the substrate, it is plastically deformed and at least part of it remains on the substrate to form a coating. (B) The peening powder does not plastically deform because of its slow flight speed due to the particle size and because it is hard. For this reason, even when it collides with the base material, it hits the already formed film and densifies the film, but falls without adhering. (C) This process can be repeated during film formation to form a dense film.

Using a gun for a cold spray nozzle shown in FIG. 1, nitrogen gas at a temperature of 400 ° C. and a pressure of 4 MPa is supplied from the working gas supply hole 9, and a powder having the composition, particle size and hardness shown in Table 1 from the powder supply hole 10. From the powder supply hole 4, peening grains having the composition, particle diameter and hardness shown in Table 1 were supplied together with nitrogen gas at room temperature and pressure of 0.2 MPa to form a film on the substrate. As a comparative example, a film raw material powder not containing peening powder is supplied from the supply hole 4 and sprayed under the above conditions to form a film.
As shown in the evaluation items of Table 1, it can be seen that the film of the present invention has higher hardness and higher density than the film of the comparative example.

An example of the gun of the cold spray apparatus suitable for implementing this invention method is shown, (a) is a top view, (b) is sectional drawing. It is a schematic diagram of the conventional cold spray equipment. It is a schematic diagram of the film densification process by the method of the present invention. An example of a cold spray apparatus suitable for carrying out the method of the present invention is shown, in which (a) is a nozzle provided with a slit, and (b) is a diagram in which two nozzles are brought close to each other.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tip detail 2 Wide end part 3 Throat part 4 Peening powder supply hole 5 Nozzle part 6 Gasket 7 Gas / powder supply part 8 Nut 9 Working gas supply hole 10 Raw material powder supply hole 11 Temperature measurement hole 12 Pressure measurement hole 13 Film raw material powder 14 Peening Powder 15 Base Material 16 Raw Material Film Formation Gun 17 Shot Peening Gun 18 Chamber 19 Parallel Portion 20 Nut 21 Commutator 22 Slit

Claims (6)

  Cold that forms a film by making a gas at a temperature lower than the melting point or softening temperature of the thermal spray material into a supersonic flow, injecting the thermal spray material into the supersonic flow, and colliding with the substrate at a high speed in a solid state A method of forming a cold spray film, comprising forming a film using a raw material powder obtained by mixing a raw material powder having a particle size of 5 to 50 µm and a peening powder having a particle size of 100 to 1000 µm.   Cold that forms a film by making a gas at a temperature lower than the melting point or softening temperature of the thermal spray material into a supersonic flow, injecting the thermal spray material into the supersonic flow, and colliding with the substrate at a high speed in a solid state In the spray film forming method, a gas / powder supply part in front of the nozzle throat part and / or a film raw material having a particle diameter of 5 to 50 μm from a plurality of powder supply holes provided in the divergent part behind the throat part or the parallel part following the divergent part A method for forming a cold spray film, comprising forming a film by supplying powder and a peening powder having a particle diameter of 100 to 1000 μm from separate powder supply holes.   The coating material powder having a particle diameter of 5 to 50 μm is supplied from the powder supply hole provided in the chamber part in front of the nozzle throat part or the divergent part behind the throat part or in the parallel part following the divergent part, and into the slit part around the nozzle ejection hole The method for forming a cold spray coating according to claim 2, wherein the coating is formed by separately supplying peening powder having a particle diameter of 100 to 1000 µm from the provided powder supply hole.   A cold that forms a film by making a gas at a temperature lower than the melting point or softening temperature of the thermal spray material into a supersonic flow, injecting the thermal spray material into the supersonic flow, and colliding with the substrate at a high speed in the solid state. The method for forming a cold spray film according to claim 2 or 3, wherein the spray film forming method includes a nozzle for forming a raw material film and a nozzle for shot peening, respectively.   5. The method for forming a cold spray coating according to claim 1, wherein the peening powder has a Vickers hardness of 400 HV or more higher than the Vickers hardness of the coating material powder.   The method of forming a cold spray film according to any one of claims 1 to 5, wherein the peening grains are a high hardness Fe-based alloy or WC.

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