JP4394993B2 - Method for producing thermal spraying powder - Google Patents

Description

  The present invention relates to a thermal spraying powder suitable for coating formation by thermal spraying and a method for producing the same.

  One of the methods for forming a film on the surface of an object for the purpose of imparting corrosion resistance, wear resistance, etc. is thermal spraying. In the thermal spraying, the material powder is melted or softened by heat, collides with the surface of the object at a high speed, and the material powder is deposited and solidified to form a coating (thermal spray coating). Thermal spraying is widely used industrially because it has features such as a high film deposition rate, a complex shape and a large area, and a local construction.

  By the way, the material powder (spraying powder) used for thermal spraying deteriorates the adhesion between the surface of the object and the thermal spraying powder and the adhesiveness between the thermal spraying powders due to the oxidation of the surface. It is known that the strength and performance of the sprayed coating are reduced by dropping from the film. The adhesion between the surface of the object and the thermal spraying powder can be improved by subjecting the surface of the object to a surface treatment. However, in order to improve the adhesion between the thermal spraying powders, it is necessary to suppress oxidation of the thermal spraying powders. Accordingly, there is a need for thermal spraying powders that are less oxidized.

  Therefore, in general, the thermal spraying powder is manufactured by a gas atomization method in which a high-pressure gas (nitrogen gas or the like) is sprayed onto a molten metal to make it fine. The thermal spraying powder produced by the gas atomization method can relatively reduce the degree of oxidation on the surface of the powder. However, the gas atomization method has problems such as high production cost and difficulty in obtaining a spray coating with sufficient strength due to variations in the degree of oxidation of the powder surface.

  Therefore, a water atomization method, which is a simple powder production method with a low production cost, is also used. The water atomization method is a method in which water is sprayed on a molten metal to make fine powder. However, since the surface of the powder of the water atomized powder obtained by the water atomization method is vigorously oxidized during the treatment, it is not possible to obtain a sprayed coating having high adhesion when used as a powder for thermal spraying. And since water atomized powder is not spherical, there exists a problem that the fluidity | liquidity at the time of spraying is bad.

Patent Document 1 discloses a metal powder obtained by spheroidizing a water atomized powder by high-speed impact with powder particles or an impactor by a high-speed air current. However, the metal powder subjected to high-speed impact becomes a high temperature due to impact energy, and oxidation of the surface of the metal powder is promoted in a high-temperature atmosphere. As a result, the surface of the resulting metal powder is more intensely oxidized.
JP-A-5-156321

Accordingly, the present inventors have led to the invention a method for producing a novel thermal spraying Powder to solve the above problems. That is, the present invention is inexpensive, low degree of oxidation of the surface, and an object thereof is to provide a method of manufacturing a thermal spray powder in the thermal spraying powder powder suitable for spraying.

  The method for producing a thermal spraying powder according to the present invention includes a primary powder production process in which a molten metal is rapidly solidified by a water atomization method to produce a primary powder, and the primary powder is disposed between opposing surfaces of a pair of grinding bodies facing each other. And a secondary powder manufacturing step of applying a compressive shearing force to the primary powder by relative movement of a set of the grinding bodies.

  In the method for producing a thermal spraying powder of the present invention, the secondary powder production step is preferably a step of applying a compressive shear force to the primary powder in an inert atmosphere.

  In the secondary powder manufacturing process, it is preferable that the time for continuously applying the compressive shear force to the primary powder is 2 seconds or less per powder. Furthermore, it is desirable to perform the secondary powder manufacturing process a plurality of times.

  Moreover, it is desirable that the primary powder is supplied between the opposing surfaces of the set of grinding bodies together with an inert gas stream. Further, the primary powder may be supplied between the opposing surfaces of the set of grinding bodies by its own weight.

In the thermal spraying powder produced by the thermal spraying powder production method of the present invention, the surface portion of the surface layer is ground and plastically deformed. When the surface portion of the surface layer portion is ground, the layer thickness of the surface layer portion becomes thin, so that the degree of oxidation of the thermal spraying powder is reduced. As a result, the adhesion of the sprayed coating is improved. In addition, when the surface portion of the surface layer portion is plastically deformed, the surface portion has an intricate shape, so that the surface area increases as compared with a conventional spherical thermal spraying powder. As a result, the thermal efficiency during thermal spraying is improved. Furthermore, since this thermal spraying powder is spheroidized, the powder has good fluidity during thermal spraying and is a thermal spraying powder suitable for thermal spraying.

In this thermal spraying powder, when the thickness of the surface layer portion is 10 nm or less, a thermal spray coating having better adhesion can be obtained.

When the specific surface area is 0.05 m ² / g or more, the thermal spraying powder has a better thermal efficiency during thermal spraying. Moreover, if the circularity of the cross section is 0.75 or more, the powder for thermal spraying has better fluidity.

  The method for producing a thermal spraying powder of the present invention comprises a primary powder producing step for producing a primary powder by a water atomizing method and a secondary powder producing step for imparting a compressive shear force to the primary powder. Therefore, a spherical secondary powder can be easily produced from a primary powder (water atomized powder) having a low production cost. In addition, in the secondary powder manufacturing process, since the energy required for manufacturing the secondary powder (spraying powder) from the water atomized powder by the compressive shear force is small, it is possible to manufacture the desired thermal spraying powder at a low cost. it can. In addition, in the secondary powder manufacturing process, the force applied to the primary powder is a compression shear force, so heat generation is reduced, and as a result, promotion of oxidation due to heat generation is suppressed.

  Moreover, in the secondary powder manufacturing process, the degree of oxidation of the thermal spraying powder (secondary powder) can be reduced by adjusting the time for continuously applying the compressive shear force to the primary powder. At this time, if the time for continuously applying the compressive shear force to the primary powder is 2 seconds or less per one powder, the generation of heat is further reduced, and the oxidation of the powder generated during the secondary powder manufacturing process is further increased. It is suppressed. As a result, a thermal spraying powder with a low degree of oxidation and better adhesion of the thermal spray coating can be produced.

  Furthermore, the primary powder can be treated in an inert atmosphere in the secondary powder manufacturing process by supplying the primary powder to the space between the opposing surfaces of the pair of grinding bodies together with an inert gas stream. Therefore, the oxidation of the surface layer part of the powder generated during the secondary powder production process is reduced, and the primary powder can be effectively processed.

The following describes the best mode for carrying out the manufacturing method of the thermal spraying powder at the end of the present invention.

[Powder for thermal spraying]
Below, the thermal spraying powder manufactured by the manufacturing method of the thermal spraying powder of this invention is demonstrated. The thermal spraying powder of the present invention comprises a central part mainly composed of a metal and a surface layer part located outside the central part and containing a metal oxide. The metal is not particularly limited as long as it is a metal or alloy usually used for thermal spraying. In addition to Fe, Ni, Cu, Mo, W, Al, Cr, etc., in which oxidation is likely to proceed in a high-temperature atmosphere during thermal spraying. An iron-based alloy is preferable. Specifically, carbon steel, alloy steel containing Cr, Ni, Co, Si and the like are used.

  In the powder for thermal spraying of the present invention, the surface portion of the surface layer portion is ground and plastically deformed to be spheroidized.

  In the thermal spraying powder of the present invention, the surface portion of the surface layer portion being ground means that the surface portion is peeled off and peeled off. Since the surface portion of the surface layer portion is ground, the layer thickness of the surface layer portion including the metal oxide is reduced, and the degree of oxidation of the thermal spraying powder is reduced. When thermal spraying is performed using a thermal spraying powder having a low degree of oxidation, the adhesion of the obtained thermal spray coating is improved. In particular, since the adhesion between the thermal spraying powders inside the thermal spray coating is improved, dropping of the thermal spraying powder from the thermal spray coating is reduced.

  In the thermal spraying powder of the present invention, the surface portion of the surface layer portion is plastically deformed is a state in which the surface portion is folded and complicated by being pressed (see FIG. 2I). More specifically, when there is a portion protruding outward, it is pressed against the surface portion and bent, or a flat portion is pressed and bent. When the surface portion of the surface layer portion is plastically deformed, the surface portion has an intricate shape, so that the surface area is increased as compared with a conventional spherical spraying powder (for example, gas atomized powder). As a result, the thermal efficiency during thermal spraying is improved. If the thermal efficiency of thermal spraying is high, the thermal spraying powder can be sufficiently melted even if the amount of heat during thermal spraying is small, and the thermal sprayed coating sprayed in a sufficiently melted state also improves its adhesion. .

  The thermal spraying powder of the present invention is spheroidized by being ground and plastically deformed. Therefore, the fluidity of the thermal spraying powder during thermal spraying is good and the thermal spraying powder is suitable for thermal spraying.

  In the thermal spraying powder of the present invention, the surface layer portion has no particular limitation on the layer thickness, and may be determined according to the required performance, but the surface layer portion preferably has a layer thickness of 10 nm or less. If the thickness of the surface layer portion is 10 nm or less, the degree of oxidation of the thermal spraying powder is low, so that the adhesion between the thermal spraying powders is further improved, and dropping of the thermal spraying powder from the thermal spray coating can be reduced. For example, a sprayed coating can be formed on the inner surface (sliding surface) of a cylinder bore of an engine cylinder and used as a substitute for a conventional cast iron liner. At this time, when the thermal spraying powder having a surface layer thickness of 10 nm or less is sprayed, the thermal spraying powder is less dropped from the thermal spray coating, resulting in increased frictional resistance and increased oil consumption caused by long-term use. Can be suppressed.

Also, the thermal spray powder of the present invention, a specific surface area of preferably 0.05 m ² / g or more, and more preferably from 0.10~0.20m ² / g. If the specific surface area is in the above range, the thermal efficiency during thermal spraying is further improved.

Further, in the thermal spraying powder of the present invention, the circularity of the cross section represented by (4π × sectional area) / (circumference of the cross section) ² is preferably 0.75 or more, more preferably 0.85 or more. It is. If the circularity is in the above range, the fluidity of the thermal spraying powder during thermal spraying is further improved. Here, the circularity of the cross section is represented by (4π × cross-sectional area) / (circumferential length of the cross section) ² , and a circle with a circularity of 1 is a perfect circle. The circularity of the cross section of the thermal spraying powder can be obtained, for example, by polishing the surface after embedding the powder with resin and measuring a micrograph of the surface with image analysis software.

[Production method of thermal spraying powder]
The manufacturing method of the thermal spraying powder of the present invention is a manufacturing method suitable for manufacturing the thermal spraying powder of the present invention, and includes two steps of a primary powder manufacturing process and a secondary powder manufacturing process. Below, each process is demonstrated.

  The primary powder production process is a process for producing a primary powder by rapidly cooling and solidifying a molten metal by a water atomization method. Therefore, the primary powder manufactured by the primary powder manufacturing process is a water atomized powder. For the water atomization method, a generally used apparatus may be used, and the treatment conditions are not particularly limited.

  The metal to be water atomized is not particularly limited as long as it is a metal or alloy used for thermal spraying. However, the method for producing a thermal spraying powder of the present invention proceeds with oxidation in a high temperature atmosphere during production or thermal spraying. It is a manufacturing method suitable for easy Fe, Ni, Cu, Mo, W, Al, Cr and the like. In particular, it is desirable to use Fe or an iron-based alloy. Specifically, carbon steel, alloy steel containing Cr, Ni, Co, Si and the like are used.

  The primary powder (water atomized powder) produced in the primary powder production process usually includes many undulated and necked neck shapes (see Fig. 2 (II)), and the surface is treated. It has an oxide film made of a metal oxide formed by oxidation therein. For example, the primary powder preferably has a circularity of a cross section having a neck shape of 0.80 or less, and more preferably 0.65 to 0.75. The average particle size is desirably 50 μm to 150 μm, and more desirably 60 μm to 80 μm.

  Then, the inventors apply a compressive shear force to the water atomized powder (primary powder) having an undulating shape having an oxide film as described above (secondary powder manufacturing process), thereby spraying it. The inventors have found that a suitable new thermal spraying powder can be easily produced, and completed the present invention.

  In the secondary powder manufacturing process, a primary powder (water atomized powder) is supplied between opposing surfaces of a pair of grinding bodies facing each other, and a compressive shearing force is applied to the primary powder by relative movement of the pair of grinding bodies. It is.

  In the secondary powder manufacturing process in which a compressive shearing force is applied to the primary powder, the constricted portion of the primary powder supplied between the opposing surfaces of the set of grinding bodies is easily pulverized. The pulverized primary powder is peeled off and removed by grinding the oxide film by a compressive shear force from a set of grinding bodies, and the protruding portion of the surface portion is folded by plastic deformation and becomes complicated. It is rounded up and spheroidized. As a result, since the oxide film of the primary powder is removed, the adhesion of the sprayed coating obtained by spraying the obtained thermal spraying powder is improved. Further, since the surface portion of the obtained thermal spraying powder has an intricate shape, the surface area of the thermal spraying powder is increased and the thermal efficiency during thermal spraying is improved. Furthermore, since it is spheroidized, the fluidity of the powder during thermal spraying is good, and a thermal spraying powder suitable for thermal spraying can be obtained.

  Further, in the secondary powder manufacturing process, since compressive shearing force is applied to the primary powder, heat is generated more than in the case of spheronization (Patent Document 1) using collision between powders or a powder and a collision body, for example. Is reduced. As a result, promotion of oxidation due to heat generation is suppressed. Therefore, by removing the oxide film (above) and suppressing the oxidation, a powder for thermal spraying with a low degree of oxidation can be obtained.

  In addition, a secondary powder manufacturing process grind | pulverizes from the constriction part of the primary powder which has a neck shape, and is spheroidized after that. Therefore, the energy required for the secondary powder manufacturing process is low. For example, when water atomized powder, gas atomized powder, and reduced powder are treated as primary powder under the same conditions in the secondary powder manufacturing process, energy of 200 Wh / kg, 700 Wh / kg, and 1100 Wh / kg are required, respectively. Therefore, according to the manufacturing method of the present invention, the thermal spraying powder suitable for thermal spraying can be easily manufactured at low cost.

  In other words, the method for producing a thermal spraying powder of the present invention provides a spherical powder with a low degree of oxidation and a large surface area by applying a compressive shear force to a primary powder (water atomized powder) having an undulating shape and having an oxide film. A thermal spraying powder, that is, a thermal spraying powder suitable for thermal spraying is obtained. Moreover, since a large energy is not required for the secondary powder production process, the powder for thermal spraying can be produced at a low cost. Therefore, according to the manufacturing method of the present invention, an inexpensive thermal spraying powder can be manufactured.

  The set of grinding bodies used in the secondary powder manufacturing process is not particularly limited as long as it consists of a set of members that face each other and move relative to each other. A pair of plate members facing each other and a pair of cylindrical members having an inner peripheral surface and an outer peripheral surface facing each other are desirable. Further, either a form in which both of a pair of members move or a form in which only one of them moves may be used. At this time, the distance between the opposing surfaces of the pair of members is preferably 0.2 to 2.0 mm. The relative speed of the pair of members is preferably 100 to 200 m / s.

  The processing conditions of the secondary powder manufacturing process are not particularly limited, but in the secondary powder manufacturing process, the time (processing time) for continuously applying the compressive shear force to the primary powder is 2 seconds or less per powder. It is desirable that If the treatment time is 2 seconds or less, even if heat is generated by the compressive shear force applied to the primary powder, the amount of heat is small, so that the oxidation of the primary powder is suppressed and the primary powder is effectively treated. Can do. As a result, it is possible to produce a thermal spraying powder with a low degree of oxidation and good adhesion of the thermal spray coating.

  Moreover, you may implement a secondary powder manufacturing process in multiple times. As described above, the time during which the compressive shear force is continuously applied to the primary powder in the secondary powder production process is preferably 2 seconds or less per one powder. By performing the secondary powder manufacturing process for 2 seconds or less for each powder, and then performing the secondary powder manufacturing process for 2 seconds or less for each powder again, the oxidation of the primary powder is suppressed and the primary powder is further effective. Can be processed automatically.

In the secondary powder manufacturing process, it is desirable that the primary powder is supplied between the opposed surfaces of the set of grinding bodies together with the airflow. At this time, the airflow is preferably an inert gas such as He, Ne, Ar, N ₂ or the like. Further, the primary powder may be supplied between the opposing surfaces of a set of grinding bodies by its own weight. In any case, it is desirable that the secondary powder production process is performed in an inert atmosphere.

  In thermal spraying, if a large amount of thermal spraying powder having a particle size of 10 μm or less is used, the powder supply performance may be reduced, and the powder supply path may be blocked. Further, if a large amount of thermal spraying powder having a particle size of 45 μm or more is used, the melting becomes insufficient and the adhesion is deteriorated. According to the method for producing a thermal spraying powder of the present invention, a yield of 10 to 45 μm (volume ratio of the thermal spraying powder having a particle size of 10 to 45 μm with respect to the obtained thermal spraying powder) is 1 in the secondary powder production process. It is 60% or more in the pass and 75% or more in the two passes, and a thermal spraying powder suitable for thermal spraying can be obtained efficiently.

  The method for producing a thermal spraying powder of the present invention is not limited to the above embodiment, and further includes a collecting means for collecting the secondary powder, a classification means for classifying the obtained secondary powder, and the like. May be.

Below, the example of the thermal spraying powder of this invention and its manufacturing method is described using drawing.
[Production of Powders A to F for Thermal Spray]
[Primary powder production process]
In the primary powder production process, a metal powder (water atomized powder) was produced using a water atomization method.

  Carbon steel (Fe-1 wt% C) was heated to 1700 ° C. in a ceramic crucible and melted. The molten carbon steel is discharged together with a high-pressure water stream from the nozzle. The discharged molten metal was pulverized by a water flow and rapidly solidified to obtain a water atomized powder (primary powder). The primary powder had an oxide film thickness of 34 nm on the surface layer.

The treatment conditions for water atomization were: water pressure: 200 kg / cm ² , atomization atmosphere (chamber atmosphere): N ₂ .

[Secondary powder production process]
From the water atomized powder (primary powder) obtained in the primary powder production process, a thermal spraying powder (secondary powder) was produced using the high-speed rotary pulverizer shown in FIG. In addition, FIG. 1 is explanatory drawing which shows typically the longitudinal cross-section of the main-body part of a high-speed rotary crusher.

  The high-speed rotary pulverizer 1 includes a cylindrical stator 11 placed on a box-shaped base 10 and a columnar rotor 12.

  The stator 11 has a short cylindrical lower casing 113 and an upper casing 114 connected to upper and lower ends thereof. The lower casing 113 is provided with a supply port 13 for supplying the primary powder together with gas into the machine from the tangential direction. The upper casing 114 is provided with a discharge port 14 for discharging the obtained secondary powder together with the gas from the tangential direction to the outside of the apparatus. Note that a suction blower (not shown) is disposed at the discharge port 14.

  The rotor 12 is coaxially inserted into the stator 11 with a minute gap of 0.2 to 2.0 mm in the radial direction. The space consisting of this minute gap becomes the grinding chamber 15. A rotating shaft 16 is inserted through the shaft center portion of the rotor 12, and the rotating shaft 16 is supported by bearings 17 and 18 attached to the lower casing 113 and the upper casing 114, respectively. Yes. A pulley 161 is attached to the lower end of the rotating shaft 16 protruding into the base 19, and the pulley 191 attached to the pulley 161 and the output shaft 19r of the motor R installed on the base 10 includes A V-belt 19 is wound around. Therefore, the rotor 12 is rotationally driven by the drive unit composed of the motor R.

  Then, a secondary powder is produced from the primary powder using the high-speed rotary pulverizer 1. When the high-speed rotary crusher 1 operates the suction blower and the motor R, the primary powder is supplied from the supply port 13 together with the argon gas into the machine. Since the rotor 12 is rotated at a high speed by the motor R, the primary powder is ground in the grinding chamber 15 and the secondary powder is discharged from the discharge port 14 together with the argon gas to the outside of the machine.

In the secondary powder production process, the rotation speed was 9000 rpm, the air volume was 4 Nm ² / min, and the supply amount was 4 kg / hr. Then, by adjusting the air volume from the suction blower, the average processing time per single particle, that is, the average time from when the primary particles are supplied to the inside of the machine until it is discharged to the outside is 0.5 seconds, It was 1 second, 2 seconds, 3 seconds, 5 seconds, and 10 seconds. The obtained secondary particles were used as thermal spraying powders A to F, respectively.

<Comparative example>
[Manufacture of thermal spraying powders G and H]
A thermal spraying powder G was obtained in the same manner as in the above example except that the secondary powder production step was not performed. That is, the thermal spraying powder G is the primary powder of the above-described embodiment. In addition, thermal spraying powder H was obtained in the same manner as in the above example, except that the atmosphere in the chamber of the water atomization was set to air in the primary powder manufacturing process, and the secondary powder manufacturing process was not performed.
The thermal spraying powders G and H are water atomized powders.

[Production of thermal spraying powders I to L]
In the secondary powder manufacturing process, thermal spraying powders I to L were obtained in the same manner as in the above example except that the primary powders were collided with each other by a high-speed air stream or the primary powder and the colliding body were collided using a jet mill. .
In addition, the process by a jet mill was made into the crushing pressure: 0.6MPa, collision body distance: 30mm, supply amount: 10kg / hr, and processing time: 30min.

[Production of thermal spraying powders M to O]
Powders M to O for thermal spraying were manufactured using a gas atomization method.

  Carbon steel (Fe-1 wt% C) was heated to 1700 ° C. in a ceramic crucible and melted. The melted carbon steel melt is discharged from the nozzle together with high-pressure nitrogen gas. The discharged molten metal was pulverized with high-pressure gas and rapidly solidified to obtain thermal spraying powders M to O.

The gas atomizing treatment conditions were as follows: gas pressure: 30 kg / cm ² , atomizing atmosphere: N ₂ (where powder O is in the air), classification conditions: −45 / + 10 (where powder N is −58). . The classification condition −45 / + 10 indicates that the powder that was shaken off by the 45 μm mesh was shaken by the 10 μm mesh, and the remaining powder was used as the thermal spraying powder.

[Evaluation of thermal spraying powder]
The shape of the thermal spraying powder was observed with a scanning electron microscope (SEM). The result is shown in FIG. 2 (I) is an SEM photograph of thermal spraying powder B (secondary powder), (II) is thermal spraying powder G (primary powder, ie, water atomized powder), and (III) is thermal spraying powder M (gas atomized powder). It is.

  The thermal spray powder G (water atomized powder), which is a primary powder, has a shape having protrusions and a constriction (FIG. 2 (II)). The thermal spray powder G, which is a secondary powder obtained by processing this primary powder in the secondary powder manufacturing process, is crushed from the constricted portion by the compressive shear force between the stator 11 and the rotor 12, and the surface portion is ground. At the same time, the protrusion is pressed into a complicated shape and is spheroidized (FIG. 2 (I)). Moreover, the thermal spraying powder M which is a gas atomized powder is spherical (FIG. 2 (III)).

Although the thermal spraying powders B and M are both spherical, the thermal spraying powder B has a specific surface area of 0.13 m ² / g because the powder surface is complicated, and the specific surface area of the thermal spraying powder M (0 0.03 m ² / g). Further, the particle size of the thermal spraying powder G, which is the primary powder, has a yield of 10 to 45 μm of 31%, but the thermal spraying powder B obtained from the thermal spraying powder G has a yield of 10 to 45 μm of 62% in one pass. In 2 passes, it was 84%. Furthermore, the 10-45 micrometer yield of the powder M for thermal spraying was 13%.

  Moreover, the surface layer part of the powder for thermal spraying was observed with the transmission electron microscope (TEM). From the TEM photograph, the layer thickness of the surface layer portion of the thermal spraying powders A to F, that is, the thickness of the oxide film layer was measured. The results are shown in FIG. The thermal spraying powders A to F were powders having a surface layer portion thinner than the primary powder (thermal spraying powder G: 36 nm). In particular, when the average treatment time per single particle was 2 seconds or less, it was possible to obtain thermal spraying powders (thermal spraying powders A to C) having a surface layer portion thickness of 10 nm or less.

  FIG. 4 shows a TEM photograph. FIG. 4 (IV) shows thermal spraying powder B (secondary powder), (V) thermal spraying powder K (powder pulverized by collision with high-speed air flow), and (VI) thermal spraying powder M (gas atomized powder). It is a TEM photograph.

[Formation of sprayed coating]
A thermal spray coating was formed on the surface of the substrate using the above-mentioned powders A to O for thermal spraying.

  As a base material, a cylinder bore formed by processing a pipe of an aluminum expanded material (A5056-H34) into an outer diameter of φ100 mm, an inner diameter of φ82 mm, and a length of 135 mm, and a columnar base material for a cylindrical tensile test of φ25 mm × 39 mm Prepared.

  The inner surface of the cylinder bore and one end surface of the columnar base material were roughened by a water jet (water pressure: 276 MPa, injection nozzle diameter: φ0.38 mm, distance from nozzle to surface: 12.5 mm). Thereafter, the inner surface of the roughened cylinder bore and one end surface of the columnar base material were sprayed.

  For spraying, plasma spraying was used. FIG. 5 shows a cross-sectional view of the plasma spraying device 5 that sprays the inner surface of the cylinder bore S. The plasma spraying device 5 includes a spraying gun 50 including a supply main body 51 that supplies plasma gas and a nozzle 59 that protrudes from the front end of the plasma spraying device 5 and has pores 58; a powder supply path 57 that supplies spraying powder; Have The supply main body 51 includes a plasma gas supply path 53 that supplies plasma gas (argon and hydrogen gas) to the nozzle 59, and a cooling water supply path 54 that supplies cooling water that cools the nozzle 59. A powder supply path 57 is disposed at the tip of the nozzle 59.

  When spraying, a voltage is applied between the tip 511 (cathode) of the supply body 51 and the nozzle 59 (anode), and plasma is generated by gas discharge in the plasma gas supplied from the plasma gas supply path 53. Let Then, by cooling the nozzle 59 with cooling water, the plasma jet Jp is ejected from the pores 58. A thermal spraying powder is supplied into the plasma jet Jp, and the thermal spraying powder is heated and accelerated to form a thermal spray coating.

  When spraying the inner surface of the cylinder bore S, the spray gun 50 is disposed inside the cylinder bore S. At this time, the cylinder bore S is arranged so that the central axis Z of the cylinder bore S and the ejection direction of the plasma jet Jp (direction of the pore 58) are orthogonal to each other. The thermal spray gun 50 moves along the central axis Z while rotating about the central axis Z, and sprays the inner surface of the cylinder bore S. Table 1 shows the thermal spraying conditions.

また、引張試験用の柱状基材の一端面に溶射を行う場合は、プラズマ溶射装置５を用い、溶射ガン５０を回転・移動させない他は、上記と同様な手順で溶射被膜を形成した。
なお、溶射用粉末Ａ〜Ｏを用いて形成された溶射被膜を、それぞれ、溶射被膜Ａ〜Ｏとする。

When spraying one end surface of the columnar base material for the tensile test, a sprayed coating was formed in the same procedure as above except that the plasma spraying device 5 was used and the spray gun 50 was not rotated or moved.
The thermal spray coatings formed using the thermal spraying powders A to O are referred to as thermal spray coatings A to O, respectively.

[Evaluation of thermal spray coating]
In order to evaluate the performance of the thermal spraying powder, an endurance test against sliding and a tensile test were performed. Below, each test is demonstrated.

[An endurance test]
In order to evaluate the durability against the sliding of the cylinder bore sprayed with the thermal spraying powder B and the thermal spraying powder N, a durability test was performed. The test method for the durability test will be described below. The sprayed powder B for spraying is referred to as cylinder bore B, and the sprayed powder N for spraying is referred to as cylinder bore N.

A piston ring of φ81 mm × 1.2 mm made of wrought aluminum (A5056-H34) was prepared. The piston ring and the cylinder bore A or the cylinder bore N were slid. The sliding conditions were as follows: load: 29.4 N, surface pressure: 330 MPa, stroke: 40 mm, frequency: 5 Hz, temperature: 70 ° C., lubricating oil: 5 W-30, oil amount: 0.1 mg / cm ² .

  The sprayed coating near the top dead center of the top ring of the cylinder bore inner diameter after sliding was observed with a scanning electron microscope (SEM). The result is shown in FIG. In the cylinder bore B (FIG. 6 (VII)), the dropping of the thermal spraying powder from the thermal spray coating was suppressed. On the other hand, in the cylinder bore N (FIG. 6 (VIII)), the thermal spraying powder dropped off from the thermal spray coating.

  Therefore, the cylinder bore B formed using the thermal spraying powder B is excellent in durability after sliding, and exhibits excellent adhesion even when used for an engine cylinder of an automobile or the like.

[Tensile test]
A tensile test was performed in order to evaluate the adhesion between the thermal spraying powders of the thermal spray coating. Below, the preparation method and test method of the test body of a tension test are demonstrated using FIG.

  The test body 7 has the same shape as the first test body 71 and the first test body 71, which is the above-described columnar base material with the sprayed coating 71a formed on one end surface 71s, and has been roughened and sprayed. The second specimen 72 was not produced.

  First, the end surface 71s (sprayed surface) of the first test body 71 and the end surface 72s on one side of the second test body 72 were coaxially bonded (1 → 2 in FIG. 7). For adhesion, the surface to be adhered was washed with acetone, then adhered with EP138 adhesive manufactured by Cemedine, and dried at 150 ° C. for 1 hour. Then, it processed into the shape which has the shoulder parts 74 and 76 whose center parallel part 75 becomes (phi) 5 mm x 35 mm (2-3 of FIG. 7), and obtained the test body 7 (3 of FIG. 7).

  The obtained specimen 7 has a sprayed coating 71a formed on the roughened end surface 71s, and since the sprayed coating 71a and the end surface 72s are bonded, the end surfaces 71s and 72s and the sprayed coating 71a The adhesion of is good. Therefore, in this tensile test, the adhesion between the thermal spraying powders can be evaluated by using the test body having the above-mentioned shape. The tensile test was performed at a tensile speed of 1 mm / min with a normal tensile tester. The result of the tensile test is shown in FIG. In FIG. 8, the tensile strength is the average value and the maximum and minimum values when a plurality of tests are performed on each thermal spraying powder, and the layer thickness of the surface layer portion indicates the average value. In addition, the average value of the tensile strength is: ● for sprayed coatings B to D, ▲ for G and H (water atomized powder), ◆ for I to L (powder crushed by collision with high-speed air current), and M to O (powder). Gas atomized powder) is indicated by ■.

  The thermal spray coating B and the thermal spray coating C formed using the thermal spraying powders B and C having a surface layer portion thickness of 10 nm or less had a tensile strength of 50 MPa or more. A thermal spray coating having a tensile strength of 50 MPa or more has excellent adhesion, and exhibits excellent durability even when used for an engine cylinder of an automobile or the like.

  Even when the thermal spraying powder D having a surface layer portion thickness exceeding 10 nm is used, the thermal spraying coatings GL formed using the thermal spraying powders GL having a surface layer portion thickness of 30 nm or more are superior. The tensile strength was shown.

  Further, the thermal spraying powder C and the thermal spraying powder M, which is a normal gas atomized powder, have no great difference in the layer thickness of the surface layer portion, but the thermal spraying coating C showed a larger tensile strength than the thermal spraying coating M. Furthermore, although the thermal spraying powder D has a slightly thicker surface layer than the thermal spraying powder N, the thermal spray coating D showed a greater tensile strength than the thermal spraying powder N.

It is the figure which showed typically the cross section of the high speed rotary mill used in the Example. It is a SEM photograph which shows the shape of the thermal spraying powder, (I) is the thermal spraying powder B, (II) is the thermal spraying powder G, and (III) is the thermal spraying powder M. It is a graph which shows the layer thickness of the surface layer part with respect to the average process time per single particle about the thermal spraying powder of an Example. It is a TEM photograph which shows the surface layer part of the thermal spraying powder, (IV) is thermal spraying powder B, (V) is thermal spraying powder K, (VI) is thermal spraying powder M. It is the figure which showed typically the cross section of the plasma spraying apparatus. It is the SEM photograph of the sprayed coating near the top dead center of the top ring of the inner diameter of the cylinder bore after sliding, (VII) is the sprayed coating with the thermal spraying powder B sprayed, and (VIII) is the thermal spraying powder N sprayed. It is a thermal spray coating. It is explanatory drawing which shows the test body used for a tension test. It is a graph which shows the tensile strength of the sprayed coating with respect to the layer thickness of a surface layer part.

Explanation of symbols

1: High-speed rotary crusher 11: Stator (grinding body)
12: Rotor (grinding body)
13: Supply port 14: Discharge port 15: Grinding chamber 5: Plasma spraying device S: Cylinder bore 7: Specimen (for tensile test)

Claims (6)

A primary powder production process for producing a primary powder by rapidly solidifying a molten metal by a water atomization method;
A secondary powder manufacturing step of supplying the primary powder between opposing surfaces of a set of grinding bodies facing each other, and applying a compressive shear force to the primary powder by relative movement of the set of grinding bodies;
A method for producing a thermal spraying powder, comprising: The secondary powder manufacturing process, the manufacturing method of the thermal spraying powder according to claim 1, wherein a step of applying a compressive shear force in an inert atmosphere to a primary powder. The secondary powder manufacturing process, the manufacturing method of the thermal spraying powder of time according to claim 1 or 2, wherein less than 2 seconds per powder continuously applying a compressive shearing force to the primary powder. Furthermore, the manufacturing method of the powder for thermal spraying in any one of Claims 1-3 which implements the said secondary powder manufacturing process in multiple times. The said primary powder is a manufacturing method of the powder for thermal spraying in any one of Claims 1-4 supplied between the opposing surfaces of the said set of grinding bodies with the airflow of an inert gas. The said primary powder is a manufacturing method of the powder for thermal spraying in any one of Claims 1-4 supplied by the dead weight between the opposing surfaces of the said set of grinding bodies.

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