JP2006176818A - Powder for thermal spraying - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide powder for thermal spraying with which a dense sprayed coating with reduced surface roughness can be satisfactorily formed. <P>SOLUTION: In the powder for thermal spraying, the 90% particle diameters D<SB>90</SB>are ≤15 μm, and also, the ratio of the integrate volume of the particles with the particle diameters of ≤1 μm is ≤2%. The value obtained by dividing the bulk density of the powder for thermal spraying by the theoretical density of the material composing the powder for thermal spraying is preferably ≥0.15. The dispersion index of the particle diameters of the powder for thermal spraying is preferably ≤0.7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermal spraying powder.

  In order to impart useful properties such as corrosion resistance, wear resistance, and heat resistance to metal parts of various industrial machines and general-purpose machines, a technique for providing a thermal spray coating on the surface of the parts is known. Since the thermal spray coating is formed by spraying a base material with a thermal spray material softened or melted by heating, its surface is essentially not smooth and rough. Therefore, when a smooth surface is required, the sprayed coating is polished until the desired surface roughness is obtained. However, since the thermal spray coating having the above-mentioned useful properties is generally high in hardness, polishing of the thermal spray coating is not easy in many cases. In particular, in the case of a thermal spray coating formed by thermal spraying cermet containing tungsten carbide and metal, it is necessary to polish using diamond abrasive grains, which is very expensive. Accordingly, there is a need for a technique for forming a sprayed coating with a small surface roughness so that polishing after spraying can be omitted or simplified.

  Further, the thermal spray coating is essentially porous, and may include through pores that penetrate the thermal spray coating and reach the surface of the thermal spray coating from the base material. However, the thermal spray coating is required to contain no through pores depending on the application, such as when it is provided for the purpose of preventing corrosion of the substrate. In the case where it is required not to include the through pores, conventionally, a countermeasure has been taken by forming a thick sprayed coating. However, since the cost of the thermal spray coating increases as the thickness increases, it is desirable that the thickness of the thermal spray coating be the minimum necessary. Therefore, there is also a need for a technique for forming a thermal spray coating that does not include through pores even when the thickness is small. As another countermeasure for preventing the through pores, there is a method of closing the through pores by a sealing treatment. However, in this case as well, the cost increases because the number of processes increases.

  As one of the technologies that meet the demand for such a thermal spray coating, it is conceivable to form the thermal spray coating from a fine spray powder. When a fine-grained thermal spraying powder is sprayed, it is possible to obtain a dense thermal sprayed coating having a small surface roughness and no through pores. However, in this case, there is a high possibility that the supply of the thermal spraying powder from the thermal spraying powder supply device to the thermal sprayer becomes unstable. This is because the fluidity of the thermal spraying powder decreases as it becomes finer. For example, when the pulsation occurs in the supply of the thermal spraying powder, the quality of the thermal spray coating is greatly deteriorated. In addition, when a bridge (powder cross-linking) occurs in the thermal spraying powder, the thermal spraying powder is not smoothly supplied to the thermal spraying machine, and in some cases, the supply of the thermal spraying powder is stopped.

For example, Patent Document 1 discloses a technique for forming a thermal spray coating from a thermal spraying powder having a 90% particle diameter D ₉₀ of 20 μm or less. However, the thermal spraying powder described in Patent Document 1 does not define any proportion of the fine particles having a particle size of 1 μm or less in the thermal spraying powder, and thus may contain many fine particles having a particle size of 1 μm or less. If the thermal spraying powder contains many fine particles having a particle size of 1 μm or less, the fluidity of the thermal spraying powder is lowered and the thermal spraying powder is likely to aggregate. If the agglomerated thermal spray powder is mixed into the thermal spray coating, the uniformity and density of the thermal spray coating may decrease, through-holes may occur in the thermal spray coating, and the surface roughness of the thermal spray coating may increase. .
JP 2003-129212 A

  An object of the present invention is to provide a thermal spraying powder capable of satisfactorily forming a dense thermal spray coating having a low surface roughness.

In order to achieve the above object, the invention according to claim 1 is such that the 90% particle diameter D ₉₀ of the thermal spraying powder is 15 μm or less, and the particle diameter relative to the total volume of all the particles in the thermal spraying powder is Provided is a thermal spraying powder characterized in that the ratio of the accumulated volume of particles of 1 μm or less is 2% or less.

The invention according to claim 2 provides the thermal spraying powder according to claim 1, wherein a value obtained by dividing the bulk density of the thermal spraying powder by the theoretical density of the material constituting the thermal spraying powder is 0.15 or more.
Invention of Claim 3 provides the powder for thermal spraying of Claim 1 or 2 whose dispersion index of the particle size of the powder for thermal spraying is 0.7 or less.

Invention of Claim 4 provides the powder for thermal spraying as described in any one of Claims 1-3 whose powder for thermal spraying is granulation-sintered powder.
Invention of Claim 5 provides the powder for thermal spraying as described in any one of Claims 1-4 in which each particle | grain in the powder for thermal spraying consists of cermets.

  ADVANTAGE OF THE INVENTION According to this invention, the powder for thermal spraying which can form a fine spray coating with a small surface roughness satisfactorily is provided.

Hereinafter, an embodiment of the present invention will be described.
The thermal spraying powder according to the present embodiment is a cermet granulated-sintered powder, and each particle in the thermal spraying powder is composed of at least one of cobalt, chromium and nickel and tungsten carbide.

  When the content of tungsten carbide as the ceramic component in the thermal spraying powder is more than 92% by mass, in other words, the total content of cobalt, chromium and nickel as the metal components in the thermal spraying powder is from 8% by mass. If the amount is too small, the thermal spray coating formed from the thermal spraying powder may become brittle and the thermal spray coating may not have high wear resistance. Therefore, the content of the ceramic component in the thermal spraying powder is preferably 92% by mass or less, and the content of the metal component in the thermal spraying powder is preferably 8% by mass or more.

When the 90% particle diameter D ₉₀ of the thermal spraying powder is larger than 15 μm (that is, when the ratio of the cumulative volume of particles having a particle diameter of 15 μm or less to the cumulative volume of all particles in the thermal spraying powder is smaller than 90%). Since a large number of particles having a particle diameter of more than 15 μm are contained in the thermal spraying powder, it is difficult to form a dense thermal spray coating having a small surface roughness from the thermal spraying powder. Therefore, it is essential that the 90% particle diameter D _{90 of} the thermal spraying powder is 15 μm or less (that is, the ratio of the cumulative volume of particles having a particle diameter of 15 μm or less is 90% or more). However, if the 90% particle diameter D ₉₀ of the thermal spraying powder is greater than 13μm even though 15μm or less (that is, if the ratio particle diameter of the accumulated volume of particles less than 13μm is less than 90 percent), The surface roughness and density of the thermal spray coating formed from the thermal spraying powder are not so improved. Therefore, the 90% particle diameter D ₉₀ of the thermal spraying powder is preferably 13 μm or less (preferably the ratio of the cumulative volume of particles having a particle diameter of 13 μm or less is 90% or more).

When the 90% particle diameter D ₉₀ of the thermal spraying powder is smaller than 5 μm (that is, when the ratio of the cumulative volume of particles having a particle diameter of 5 μm or less is larger than 90%), more specifically, when it is smaller than 7 μm (that is, particles) In the case where the ratio of the cumulative volume of particles having a diameter of 7 μm or less is larger than 90%), the spraying powder has a fluidity because many particles having a particle diameter of 5 μm (or 7 μm) or less are contained in the spraying powder. Slightly lower. Accordingly, the 90% particle diameter D ₉₀ of the thermal spraying powder is preferably 5 μm or more (preferably the ratio of the cumulative volume of particles having a particle diameter of 5 μm or less is 90% or less), and the 90% particle diameter D _{90 of the} thermal spraying powder is 90%. Is more preferably 7 μm or more (more preferably, the ratio of the cumulative volume of particles having a particle diameter of 7 μm or less is 90% or less).

When the ratio of the cumulative volume of particles having a particle diameter of 1 μm or less to the cumulative volume of all particles in the thermal spraying powder is larger than 2% (that is, when the 2% particle diameter D _{2 of the} thermal spraying powder is smaller than 1 μm). Since the spraying powder contains many particles having a particle size of 1 μm or less, the fluidity of the spraying powder is greatly reduced. Supply becomes unstable. In addition, agglomeration of the thermal spraying powder occurs, and as a result, the uniformity and density of the thermal spray coating are reduced, through-holes are formed in the thermal spray coating, and the surface roughness of the thermal spray coating is increased. Therefore, it is essential that the ratio of the cumulative volume of particles having a particle diameter of 1 μm or less is 2% or less (that is, the 2% particle diameter D _{2 of the} thermal spraying powder is 1 μm or more). However, even if the ratio of the cumulative volume of particles having a particle diameter of 1 μm or less is 2% or less, the ratio is 1.5% or more (that is, the 1.5% particle diameter D _{1.5 of the} thermal spraying powder is smaller than 1 μm). ), The supply stability of the thermal spraying powder during thermal spraying is not improved so much. Therefore, the ratio of the cumulative volume of particles having a particle diameter of 1 μm or less is preferably 1.5% or less (that is, the 1.5% particle diameter D _1.5 of the thermal spraying powder is 1 μm or less).

  When the dispersion index of the particle size of the thermal spraying powder is larger than 0.7, more specifically, when it is larger than 0.67, the proportion of particles having a small particle size contained in the thermal spraying powder is increased, so that the thermal spraying is performed. The fluidity of the powder for use is slightly reduced. Alternatively, since the ratio of particles having a large particle size contained in the thermal spraying powder is increased, the density of the thermal spray coating formed from the thermal spraying powder may be slightly decreased or the surface roughness may be slightly increased. . Accordingly, the dispersion index of the particle size of the thermal spraying powder is preferably 0.7 or less, more preferably 0.67 or less.

  When the value obtained by dividing the bulk density of the thermal spraying powder by the theoretical density of the material constituting the thermal spraying powder is smaller than 0.15, more specifically, smaller than 0.17, the thermal spraying powder at the time of thermal spraying There is a possibility that the supply stability is slightly lowered and the density of the thermal spray coating formed from the thermal spraying powder is somewhat lowered. Therefore, the value obtained by dividing the bulk density of the thermal spraying powder by the theoretical density of the material constituting the thermal spraying powder is preferably 0.15 or more, more preferably 0.17 or more.

  Next, a method for producing a thermal spraying powder according to the present embodiment, that is, a method for producing a granulated-sintered cermet powder composed of at least one of cobalt, chromium and nickel and tungsten carbide will be described. First, a slurry is prepared by mixing a metal powder composed of at least one of cobalt, chromium, and nickel and a tungsten carbide powder in a dispersion medium. A suitable binder may be added to the slurry. Next, granulated powder is produced from the slurry using a rolling granulator, a spray granulator or a compression granulator. A granulated-sintered cermet powder composed of at least one of cobalt, chromium and nickel and tungsten carbide is produced by sintering the granulated powder thus obtained and further pulverizing and classifying it. Note that the granulated powder may be sintered in a vacuum or in an inert gas atmosphere, or using an electric furnace or a gas furnace.

  The thermal spraying powder according to the present embodiment is used in applications for forming a thermal spray coating by, for example, high-speed flame spraying. The thermal spray coating formed by high-speed flame spraying of the thermal spraying powder according to the present embodiment has good wear resistance. As a high-speed flame sprayer that can spray the powder for thermal spraying according to the present embodiment particularly preferably, for example, “JP-5000” manufactured by Praxair / TAFA, “Diamond Jet (hybrid type)” manufactured by Sulzer Metco High output type high-speed flame sprayers such as “θ gun” manufactured by Witeco Japan, Inc.

This embodiment has the following advantages.
Since the thermal spray 90% particle diameter D ₉₀ of the powder is set to 15μm or less, according to the thermal spraying powder of this embodiment, it is possible to form small thermal spray coating dense and surface roughness.

  Furthermore, since the ratio of the cumulative volume of particles having a particle diameter of 1 μm or less to the cumulative volume of all particles in the thermal spraying powder is set to 2% or less, the thermal spraying powder according to the present embodiment provides thermal spraying. The film can be satisfactorily formed.

  Since the value obtained by dividing the bulk density of the thermal spraying powder by the theoretical density of the material constituting the thermal spraying powder is set to 0.15 or more, according to the thermal spraying powder according to this embodiment, thermal spraying during thermal spraying It is possible to more reliably prevent a decrease in the supply stability of the coating powder and a decrease in the density of the thermal spray coating formed from the thermal spraying powder.

  -Since the dispersion index of the particle size of the thermal spraying powder is set to 0.7 or less, according to the thermal spraying powder according to the present embodiment, there is an adverse effect caused by the irregular size of the particles in the thermal spraying powder. Occurrence is suppressed.

  The granulated-sintered powder generally has better fluidity than the melt-ground powder and the sintered-ground powder, and is less likely to be contaminated with impurities during the production process. Therefore, the thermal spraying powder according to this embodiment made of granulated-sintered powder also has these advantages.

-Each particle | grain in the powder for thermal spraying which concerns on this embodiment consists of cermets. Therefore, according to the thermal spraying powder according to the present embodiment, it is possible to form a thermal spray coating having good wear resistance.
The embodiment may be modified as follows.

  Each particle in the thermal spraying powder may further contain ceramics other than tungsten carbide such as chromium carbide instead of tungsten carbide or in addition to tungsten carbide.

  Each particle in the thermal spraying powder may further contain a metal other than cobalt, chromium and nickel instead of cobalt, chromium and nickel or in addition to cobalt, chromium and nickel.

  The thermal spraying powder may contain components other than cermet granulated and sintered powder composed of at least one of cobalt, chromium and nickel and tungsten carbide. However, the content of the granulated-sintered powder in the thermal spraying powder is preferably 50% by mass or more, more preferably 80% by mass or more.

  The powder for thermal spraying may be a melt-ground cermet powder or a sintered-ground cermet powder instead of the granulated-sintered cermet powder. In this case, each particle in the thermal spraying powder may be composed of at least one of cobalt, chromium and nickel and tungsten carbide, or may be other than that. The melt-pulverized powder is manufactured by pulverizing and classifying the raw material powder after cooling and solidifying, and the sintered-ground powder is manufactured by pulverizing and classifying the raw material powder after sintering.

-The powder for thermal spraying which concerns on this embodiment may be used in the use which forms a thermal spray coating by thermal spraying methods other than high-speed flame spraying.
Next, examples and comparative examples of the present invention will be described.

  In Examples 1 to 7 and Comparative Examples 1 to 4, a granulated-sintered cermet powder containing tungsten carbide as a main component and 12% by weight of cobalt was prepared as a thermal spraying powder. In Example 8, a melt-pulverized cermet powder composed of tungsten carbide and cobalt was prepared as a thermal spraying powder. In Example 9 and Comparative Example 5, a granulated / sintered cermet powder containing tungsten carbide as a main component and containing 10% by weight of cobalt and 4% by weight of chromium was prepared as a thermal spraying powder. The details of each thermal spraying powder according to Examples 1 to 9 and Comparative Examples 1 to 5 are as shown in Table 1.

  The “ratio of particles having a particle diameter of 1 μm or less” in Table 1 shows the ratio of the integrated volume of particles having a particle diameter of 1 μm or less to the integrated volume of all particles in each thermal spraying powder. This ratio was measured using a laser diffraction / scattering type particle size analyzer “LA-300” manufactured by Horiba, Ltd.

In the column of “10% particle diameter D ₁₀ ”, “50% particle diameter D ₅₀ ” and “90% particle diameter D ₉₀ ” in Table 1, the laser diffraction / scattering type particle size measuring device “LA” manufactured by Horiba, Ltd. 10% particle diameter D ₁₀ , 50% particle diameter D ₅₀ and 90% particle diameter D ₉₀ of each thermal spraying powder measured using −300 ″ are shown. Incidentally, the 10% particle size D ₁₀ of the thermal spraying powder, the volume of the integrated volume of particles in the thermal spraying powder from small particles of the particle size until more than 10% of the total volume of all particles in the thermal spraying powder in this order Is the particle diameter of the particles that are accumulated last. 50% particle size D ₅₀ of the thermal spraying powder is accumulated volume of the integrated volume particles in the thermal spraying powder from small particles of particle size in the order until the 50% of the total volume of all particles in the thermal spraying powder It is the particle diameter of the particles accumulated last. 90% particle diameter D ₉₀ of the thermal spraying powder is accumulated volume of the integrated volume of particles in the thermal spraying powder from small particles of the particle size to a more than 90% of the total volume of all particles in the thermal spraying powder in this order It is the particle diameter of the particles accumulated last.

In the “dispersion index” column of Table 1, the dispersion index D of the particle size of each thermal spraying powder calculated according to the formula: D = (D ₉₀ −D ₁₀ ) / (D ₉₀ + D ₁₀ ) is shown. Wherein, D ₉₀ represents the 90% particle diameter of the thermal spraying powder, D ₁₀ is respectful 10% particle size of the thermal spraying powder.

  In the "bulk density / theoretical density" column of Table 1, the bulk density of each thermal spraying powder measured using a bulk specific gravity measuring machine (see JIS Z2504) is divided by the theoretical density of the material constituting the thermal spraying powder. Indicates the value.

  In order to form a sprayed coating having a thickness of 200 μm, each of the thermal spraying powders according to Examples 1 to 4, 6 to 9 and Comparative Examples 1 to 5 was subjected to high-speed flame spraying under the first thermal spraying conditions shown in Table 2, and Example 5 The powder for thermal spraying according to the above was subjected to high-speed flame spraying under the second spraying conditions shown in Table 2. Then, based on whether or not a sprayed coating could be formed, each thermal spraying powder was evaluated in two stages: good (◯) and defective (×). That is, when the thermal spray coating can be formed, it is good, and when the supply of the thermal spraying powder from the thermal spraying powder supply device to the thermal spraying machine is stopped and the thermal spray coating cannot be formed, it is regarded as defective. evaluated. The results of this evaluation are shown in the “film formation” column of Table 1.

  The surface roughness Ra at any 15 locations on the thermal spray coating formed by high-speed flame spraying of the respective thermal spraying powders according to Examples 1 to 9 and Comparative Examples 1 to 5 was measured under the conditions shown in Table 3. Based on the average value of the surface roughness Ra at 15 locations measured at this time, each thermal spraying powder was evaluated in three stages of excellent (◎), good (◯), and poor (x). That is, when the average value of the surface roughness Ra was less than 1.3 μm, it was evaluated as good, when it was 1.3 μm or more and less than 1.6 μm, and when it was 1.6 μm or more, it was evaluated as bad. The results of this evaluation are shown in the column “Surface Roughness of Sprayed Coating Before Polishing” in Table 1. Further, based on the measured standard deviation of the surface roughness Ra at 15 locations, each thermal spraying powder was evaluated in three stages: excellent (◎), good (◯), and poor (x). That is, when the standard deviation of the surface roughness Ra was less than 0.3, it was evaluated as good, when it was 0.3 or more and less than 0.45, good, and when it was 0.45 or more, it was evaluated as bad. The results of this evaluation are shown in the “Surface roughness variation” column of Table 1.

  The surface roughness Ra at any 15 locations on the thermal spray coating formed by high-speed flame spraying of the respective thermal spraying powders according to Examples 1 to 9 and Comparative Examples 1 to 5 is shown in Table 3 after the thermal spray coating is mirror-polished. It was measured again under the conditions shown. Based on the average value of the surface roughness Ra at 15 locations measured at this time, each thermal spraying powder was evaluated in three stages of excellent (◎), good (◯), and poor (x). That is, when the average value of the surface roughness Ra was less than 0.006 μm, it was evaluated as good, when it was 0.006 μm or more and less than 0.010 μm, and when it was 0.010 μm or more, it was evaluated as bad. The results of this evaluation are shown in the column “Surface Roughness of Polished Coating after Polishing” in Table 1.

  Each of the thermal spraying powders according to Examples 1 to 9 and Comparative Examples 1 to 5 was subjected to high-speed flame spraying and a 50 μm thick sprayed coating was subjected to a salt spray test (see JIS Z 2371). It was visually confirmed whether red rust was generated on the substrate. Based on the occurrence of red rust after the salt spray test, each thermal spraying powder was evaluated in three stages: excellent (）), good (◯), and poor (x). That is, when red rust is observed after 24 hours of salt water spray, it is not good. After 24 hours of salt water spray, red rust is not observed, but after 48 hours of salt water spray, red rust is observed, and 48 hours of salt water. When red rust was not observed even after spraying, it was evaluated as excellent. The results of this evaluation are shown in the “Dense” column of Table 1.

表１に示すように、実施例１〜９においては、研磨前の溶射皮膜の表面粗さ及び緻密さに関する評価がいずれも優又は良であった。この結果から、実施例１〜９に係る溶射用粉末によれば緻密で表面粗さの小さい溶射皮膜を形成可能であることが分かる。

As shown in Table 1, in Examples 1 to 9, the evaluations regarding the surface roughness and the denseness of the sprayed coating before polishing were both excellent or good. From this result, it can be seen that the thermal spray coating according to Examples 1 to 9 can form a thermal spray coating having a high density and a small surface roughness.

The technical idea that can be grasped from the embodiment will be described below.
The thermal spraying powder according to claim 5, wherein the content of the ceramic component in the thermal spraying powder is 92% by mass or less.

The thermal spraying powder according to claim 5, wherein the content of the metal component in the thermal spraying powder is 8% by mass or more.
The thermal spraying powder according to claim 5, wherein the cermet contains tungsten carbide.

The thermal spraying powder according to claim 5, wherein the cermet contains at least one of cobalt, chromium, and nickel.
The thermal spraying powder according to any one of claims 1 to 5, wherein the thermal spraying powder is used in an application in which a thermal spray coating is formed by high-speed flame spraying.

A thermal spraying method characterized by spraying the thermal spraying powder according to any one of claims 1 to 5.
A thermal spray coating formed by thermal spraying the thermal spraying powder according to any one of claims 1 to 5.

Claims (5)

The 90% particle diameter D ₉₀ of the thermal spraying powder is 15 μm or less, and the ratio of the cumulative volume of particles having a particle diameter of 1 μm or less to the cumulative volume of all particles in the thermal spraying powder is 2% or less. Thermal spray powder.   The thermal spraying powder according to claim 1, wherein a value obtained by dividing the bulk density of the thermal spraying powder by the theoretical density of the material constituting the thermal spraying powder is 0.15 or more.   The thermal spraying powder according to claim 1 or 2, wherein a dispersion index of a particle size of the thermal spraying powder is 0.7 or less.   The thermal spraying powder according to any one of claims 1 to 3, wherein the thermal spraying powder is a granulated-sintered powder.   The thermal spraying powder according to any one of claims 1 to 4, wherein each particle in the thermal spraying powder is made of cermet.