CERMET POWDER

A powder material of the present invention contains ceramic-metal composite particles, wherein at least a part of the composite particles exhibit no breaking point in a stress-strain diagram obtained by applying a compressive load that increases up to a maximum value of 10 mN or more at a loading rate of 15.0 mN/s or less.

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Description
TECHNICAL FIELD

The present invention relates to a cermet powder material including ceramic-metal composite particles.

BACKGROUND ART

Cermet particles, which are ceramic-metal composite particles, are utilized for various purposes, for example, used as a material for forming a thermal spray coating, namely, a thermal spray powder, as described in Patent Document 1. One performance required for a thermal spray powder is that most of the powder thermally sprayed toward a substrate adheres or deposits on the substrate to form a coating, namely, high deposit efficiency. Cermet particles, however, are generally difficult to thermally spray with high deposit efficiency, as compared with metal particles. This is particularly remarkable in the case of a low-temperature thermal spraying process, such as cold spraying, because the degree of melting and softening of the metal component is reduced.

PRIOR ART DOCUMENTS

  • Patent Document 1: Japanese Laid-Open Patent Publication No. 2012-12686

SUMMARY OF THE INVENTION Problems that the Invention is to Solve

Accordingly, an objective of the present invention is to provide a cermet powder material that is improved in terms of deposit efficiency when used as a thermal spray powder.

Means for Solving the Problems

In order to achieve the above objective and in accordance with one aspect of the present invention, a powder material is provided that includes ceramic-metal composite particles, wherein at least a part of the composite particles exhibit no breaking point in a stress-strain diagram that is obtained by applying a compressive load that increases up to a maximum value of 10 mN or more at a loading rate of 15.0 mN/s or less.

In accordance with another aspect of the present invention, a method for forming a thermal spray coating is provided that includes thermally spraying the powder material according to the above aspect at a thermal spraying temperature of 3,000° C. or lower.

Effects of the Invention

The present invention succeeds in providing a cermet powder material that is improved in terms of deposit efficiency when used as a thermal spray powder.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a stress-strain diagram of two granulated-sintered cermet particles exhibiting different stress-strain behaviors from each other.

FIGS. 2(a) and 2(b) are photographs of the cross section of a granulated-sintered cermet particle in a powder material of Example 2.

FIGS. 3(a) and 3(b) are photographs of the cross section of a granulated-sintered cermet particle in a powder material of Comparative Example 2.

 MODES FOR CARRYING OUT THE INVENTION

One embodiment of the present invention will now be described. The present invention is not limited to the embodiment described below and appropriate modifications in design may be made to such an extent that the content of the present invention is not impaired.

A powder material according to the present embodiment is composed of granulated-sintered cermet particles. The granulated-sintered cermet particles are a composite material of ceramic fine particles and metal fine particles, and are produced by sintering a granulated material (granule) obtained by granulating a mixture of the ceramic fine particles and the metal fine particles.

The powder material of the present embodiment is used, for example, as a thermal spray powder. That is, the powder material is used, for example, in an application in which the powder material is thermally sprayed toward a substrate to thereby form a thermal spray coating on the substrate.

In order to obtain high deposit efficiency in use of the powder material of the present embodiment as a thermal spray powder, it is necessary that at least a part of the granulated-sintered cermet particles exhibit no breaking point in a stress-strain diagram that is obtained by applying a compressive load that increases up to a maximum value of 10 mN or more, preferably 100 mN or more, more preferably 200 mN or more, further preferably 500 mN or more, and most preferably 900 mN or more at a loading rate of 15.0 mN/s or less, preferably 14.0 mN/s or less, and most preferably 13.0 mN/s or less.

A loading rate of 15.0 mN/s or less is a rate sufficient for deforming the granulated-sintered cermet particle. As the loading rate when a compressive load is applied to the granulated-sintered cermet particle is lower, the disintegration properties of the granulated-sintered cermet particle during a thermal spraying process can be more accurately evaluated.

A compressive load of 10 mN or more is a load sufficient for deforming the granulated-sintered cermet particle. The compressive load applied to the granulated-sintered cermet particle is preferably larger because the disintegration properties of the granulated-sintered cermet particle during a thermal spraying process can be more accurately evaluated.

The disintegration properties of the granulated-sintered cermet particle mean the ease of disintegration of the granulated-sintered cermet particle, the behavior after disintegration, and others. The evaluation and control of disintegration properties of the granulated-sintered cermet particle can lead to the amelioration of the problem of spitting (which is a phenomenon where a deposit made by adhesion or deposition of a thermal spray powder excessively molten to the inner wall of a nozzle in a thermal spraying machine drops off the inner wall during thermal spraying of the thermal spray powder and is incorporated into a thermal spray coating, the phenomenon causing the reduction in performance of the thermal spray coating) and the problem of the reduction in hardness of a thermal spray coating.

FIG. 1 is a stress-strain diagram that is obtained by applying a compressive load that increases up to a maximum value of 10 mN or more at a loading rate of 15.0 mN/s or less, to two granulated-sintered cermet particles exhibiting different stress-strain behaviors from each other. In FIG. 1, while a line with symbol A shows the behavior with a breaking point where a strain rapidly increases at a certain stress, a line with symbol B shows the behavior without such a breaking point. The proportion of granulated-sintered cermet particles exhibiting the stress-strain behavior shown by the line with symbol B in FIG. 1 to the granulated-sintered cermet particles in the powder material of the present embodiment is preferably 1% or more, more preferably 5% or more, and further preferably 10% or more. All or almost all (for example, about 90%) of the granulated-sintered cermet particles may exhibit the stress-strain behavior shown by the line with symbol B in FIG. 1.

The proportion of granulated-sintered cermet particles exhibiting no breaking point can be determined as follows, for example. That is, with respect to granulated-sintered cermet particles arbitrarily selected from the powder material and each having a predetermined particle diameter or less, the stress-strain behavior by applying a compressive load that increases up to a maximum value of 10 mN or more at a loading rate of 15.0 mN/s or less is measured. Then, the proportion of granulated-sintered cermet particles exhibiting no breaking point to the granulated-sintered cermet particles tested is calculated. For example, a microcompression testing machine (MCTE-500, manufactured by Shimadzu Corporation) can be employed in the stress-strain behavior measurement, but not limited thereto.

A granulated-sintered cermet particle exhibiting the stress-strain behavior shown by the line with symbol A in FIG. 1, when thermally sprayed toward a substrate, may cause breaking in collision with the substrate, and the resulting broken piece may rebound without depositing onto the substrate. On the contrary, a granulated-sintered cermet particle exhibiting the stress-strain behavior shown by the line with symbol B in FIG. 1 is likely to be plastically deformed without being broken in collision with the substrate, to deposit onto the substrate. As illustrated in FIG. 9 in Japanese Laid-Open Patent Publication No. 2011-208165 that discloses a metal material for thermal spraying, a metal particle generally exhibits a stress-strain behavior having no breaking point, and the stress-strain behavior shown by the line with symbol B in FIG. 1 can be said to be similar therewith. It is considered that this is the reason why the powder material of the present embodiment achieves high deposit efficiency when used as a thermal spray powder, regardless of being composed of the cermet particles.

As a means for obtaining the granulated-sintered cermet particles exhibiting no breaking point, it is effective to make the size of metal particle portions in each granulated-sintered cermet particle small as much as possible.

Specifically, the average diameter (directed average diameter) of the metal particle portions is preferably 3 μm or less, more preferably 1 μm or less, further preferably 0.5 μm or less, and particularly preferably 0.1 μm or less.

While the metal particle portions in each granulated-sintered cermet particle serve as a binder that binds ceramic particle portions in the same granulated-sintered cermet particle, application of a compressive load to the granulated-sintered cermet particle may cause cracking on the binding site between the ceramic particle portions to thereby break the granulated-sintered cermet particle. In this regard, as the average diameter of the metal particle portions is smaller, the size of the binding site between the ceramic particle portions is smaller, and as a result, breaking of the granulated-sintered cermet particle caused by cracking on the binding site can be suppressed.

As another means for obtaining the granulated-sintered cermet particles exhibiting no breaking point, it is also effective to make the size of metal particle portions in each granulated-sintered cermet particle smaller than the size of ceramic particle portions in the same granulated-sintered cermet particle. Specifically, the ratio of the average diameter (directed average diameter) of the metal particle portions to the average diameter (directed average diameter) of the ceramic particle portions is preferably less than 1.5, more preferably 1 or less, further preferably 0.5 or less, and most preferably 0.1 or less. As this ratio is smaller, the size of the binding site between the ceramic particle portions is relatively smaller, and as a result, breaking of the granulated-sintered cermet particle caused by cracking on the binding site can be suppressed.

The average diameter (directed average diameter) of the ceramic particle portions in each granulated-sintered cermet particle is preferably 6 μm or less, more preferably 1 μm or less, further preferably 0.5 μm or less, and particularly preferably 0.1 μm or less.

As still another means for obtaining the granulated-sintered cermet particles exhibiting no breaking point, it is also effective to make the ratio of the average diameter (directed average diameter) of the metal particle portions to the average diameter (volume average diameter) of the granulated-sintered cermet particles small as much as possible. Specifically, this ratio is preferably 0.15 or less, more preferably 0.1 or less, further preferably 0.05 or less, and particularly preferably 0.01 or less. As this ratio is smaller, the size of the binding site between the ceramic particle portions is relatively smaller, and as a result, breaking of the granulated-sintered cermet particle caused by cracking on the binding site can be suppressed.

The average diameter of the metal particle portions and the average diameter of the ceramic particle portions in each granulated-sintered cermet particle basically reflect the average diameter of the metal fine particles and the average diameter of the ceramic fine particles, respectively, these fine particles being used in production of the granulated-sintered cermet particles. These average diameters, however, are also affected by sintering that is performed in production of the granulated-sintered cermet particles, and thus are generally slightly different from the average diameter of the metal fine particles and the average diameter of the ceramic fine particles.

The ceramic fine particles for use in production of the granulated-sintered cermet particles are composed of a single-component ceramic or a composite ceramic, for example, including at least one selected from carbides, such as tungsten carbide and chromium carbide, borides, such as molybdenum boride and chromium boride, nitrides, such as aluminum nitride, silicides, and oxides.

The metal fine particles for use in production of the granulated-sintered cermet particles are composed of a single-component metal or a metal alloy, for example, including at least one selected from cobalt, nickel, iron, chromium, silicon, aluminum, copper, and silver. The metal fine particles are, however, preferably composed of a metal having a face-centered cubic lattice structure or a body-centered cubic lattice structure. A metal having a face-centered cubic lattice structure or a body-centered cubic lattice structure is easily slip-deformed, and thus a granulated-sintered cermet particle produced from such a metal is less likely to be broken when a compressive load is applied. Specific examples of a metal having a face-centered cubic lattice structure include nickel, aluminum, and iron (y-iron) with an austenite phase. Specific examples of a metal having a body-centered cubic lattice structure include tungsten, molybdenum, and iron (α-iron) with a ferrite phase.

In particular, tungsten carbide fine particles and cobalt fine particles are preferably used in combination. Since tungsten carbide and cobalt are highly wettable with each other, namely, compatible with each other, a granulated-sintered cermet particle produced by combining tungsten carbide fine particles and cobalt fine particles is less likely to be broken when a compressive load is applied.

The metal particle portions are preferably present with being dispersed in each granulated-sintered cermet particle as much as possible. As a means for allowing the metal particle portions to be present with being dispersed, it is effective to sufficiently mix the ceramic fine particles with the metal fine particles by a dry method or a wet method, preferably by a wet method, in production of the granulated-sintered cermet particles.

The ceramic content in the granulated-sintered cermet particles is preferably 95% by mass or less, more preferably 92% by mass or less, and further preferably 90% by mass or less. In other words, the metal content in the granulated-sintered cermet particles is preferably 5% by mass or more, more preferably 8% by mass or more, and further preferably 10% by mass or more. As the ceramic content is lower (in other words, as the metal content is higher), the plastic deformability of each granulated-sintered cermet particle is enhanced, and as a result, the powder material is enhanced in terms of deposit efficiency when used as a thermal spray powder.

Each of the granulated-sintered cermet particles preferably has an outer shape close to a true sphere as much as possible. Specifically, the granulated-sintered cermet particles have an aspect ratio of preferably 1.30 or less. A granulated-sintered cermet particle having an aspect ratio of 1.30 or less is less likely to be broken when a compressive load is applied. The aspect ratio of the granulated-sintered cermet particle can be determined by, for example, dividing the length of the long side of the minimum rectangle circumscribed to the particle as an image by a scanning electron microscope, by the length of the short side of the same rectangle.

The granulated-sintered cermet particles each include pores having a median diameter of preferably 2.0 μm or less, more preferably 1.7 μm or less, and further preferably 1.5 μm or less. When a compressive load is applied to the granulated-sintered cermet particle, cracking may occur around the pores in the granulated-sintered cermet particle to thereby allow the granulated-sintered cermet particle to be broken. In this regard, as the median diameter of the pores is smaller, breaking of the granulated-sintered cermet particle due to the occurrence of cracking around the pores in the granulated-sintered cermet particle can be suppressed. The median diameter of the granulated-sintered cermet particles, however, is preferably 0.001 μm or more, more preferably 0.005 μm or more, and further preferably 0.01 μm or more from the viewpoint of the ease of coating formation.

The granulated-sintered cermet particles have a porosity of preferably 30% or less, more preferably 25% or less, and further preferably 20% or less. As the porosity of the granulated-sintered cermet particles is lower, breaking of each granulated-sintered cermet particle due to the occurrence of cracking around the pores in the granulated-sintered cermet particle can be suppressed. The porosity of the granulated-sintered cermet particles, however, is preferably 0.1% or more and further preferably 1% or more from the viewpoint of the ease of coating formation. The porosity of the granulated-sintered cermet particles can be measured by, for example, a mercury intrusion method.

The above embodiment can be modified as follows.

    • The powder material of the above embodiment may include any component other than the granulated-sintered cermet particles. For example, the powder material may include free ceramic particles or free metal particles. Alternatively, the powder material may include molten-crushed cermet particles or sintered-crushed cermet particles. The molten-crushed cermet particles are produced by melting a mixture of ceramic fine particles and metal fine particles, cooling and solidifying the mixture molten, then crushing the mixture solidified, and then, if necessary, classifying the mixture crushed. The sintered-crushed cermet particles are produced by sintering and crushing a mixture of ceramic fine particles and metal fine particles, and then, if necessary, classifying the mixture crushed.
    • The powder material of the above embodiment may be composed of molten-crushed cermet particles or sintered-crushed cermet particles instead of the granulated-sintered cermet particles, or may include any component in addition to the molten-crushed cermet particles or sintered-crushed cermet particles. A granulated-sintered cermet particle, however, generally has an outer shape close to a true sphere, as compared with a molten-pulverized cermet particle and a sintered-pulverized cermet particle, and is less likely to be broken when a compressive load is applied. Also from the viewpoint that the size and number of the pores can be arbitrarily controlled in a relatively easy manner, the granulated-sintered cermet particles are preferable.
    • When the powder material of the above embodiment is used as a thermal spray powder, the powder material may be mixed with other component and then thermally sprayed, or may be thermally sprayed as it is without being mixed with other component.
    • The use of the powder material of the embodiment is not particularly limited to a thermal spray powder, and the powder material may be used as a material for forming a sintered body or as polishing abrasives, for example. The powder material of the above embodiment, however, includes granulated-sintered cermet particles that are less likely to be broken when a compressive load is applied, and thus the powder material is suitable for an application in which a compressive load acts on the powder material during use.
    • The thermal spraying temperature in the thermal spraying process in which the powder material of the embodiment is thermally sprayed is not particularly limited, but is preferably 3,000° C. or lower, more preferably 2,500° C. or lower, and further preferably 2,000° C. or lower in order to restrain spitting due to excessive melting of the powder material or in order to suppress thermal degradation of the ceramic fine particles in the granulated-sintered cermet particles.
    • In addition, the thermal spraying temperature in the thermal spraying process in which the powder material of the embodiment is thermally sprayed is not particularly limited, but is preferably 300° C. or higher, more preferably 400° C. or higher, and further preferably 500° C. or higher in order to obtain high deposit efficiency.
    • The method for thermally spraying the powder material of the embodiment may be high velocity flame spraying, such as high velocity oxygen fuel (HVOF) spraying, or may be explosion thermal spraying or atmospheric plasma spraying (APS). Alternatively, the method may also be a low-temperature thermal spraying process, such as cold spraying, warm spraying, and high velocity air fuel (HVAF) spraying. In cold spraying, a working gas at a temperature lower than the melting point and the softening point of the powder material is accelerated to a supersonic velocity, and the working gas accelerated is used to allow the powder material to collide and deposit onto a substrate in the solid state. In warm spraying, a nitrogen gas as a cooling gas is incorporated into a combustion flame in which kerosene and oxygen as a combustion improver are used, thereby forming a combustion flame at a lower temperature than that of HVOF spraying, and this combustion flame heats and accelerates the powder material to allow the powder material to collide and deposit onto a substrate at a supersonic velocity. In HVAF spraying, air is employed as a combustion improver instead of oxygen to thereby form a combustion flame at a lower temperature than that of HVOF spraying, and this combustion flame heats and accelerates the powder material to allow the powder material to collide and deposit onto a substrate.

Next, the present invention will be described more specifically with reference to examples and comparative examples.

Examples 1 to 7 and Comparative Examples 1 to 4 HVOF Spraying

Powder materials of Examples 1 to 7 and Comparative Examples 1 to 4, each of which is composed of granulated-sintered cermet particles, were prepared, and were each thermally sprayed in conditions shown in Table 1. The details of each of the powder materials are shown in Table 2. Although not shown in Table 2, the average diameter of the granulated-sintered cermet particles in each of the powder materials was measured using a laser diffraction/scattering particle size measuring apparatus “LA-300”, manufactured by Horiba Ltd., and all the average diameters were found to be 17 μm.

The chemical composition of the granulated-sintered cermet particles of each of the powder materials is shown in the column “Composition of cermet particles” in Table 2. In this column, “WC/12% Co” represents a cermet including 12% by mass of cobalt and the balance of tungsten carbide, “WC/12% FeCrNi” represents a cermet including 12% by mass of an iron-chromium-nickel alloy and the balance of tungsten carbide, “WC/10% Co/4% Cr” represents a cermet including 10% by mass of cobalt, 4% by mass of chromium, and the balance of tungsten carbide, and “WC/20% CrC/7% Ni” represents a cermet including 20% by mass of chromium carbide, 7% by mass of nickel, and the balance of tungsten carbide. The chemical composition of the granulated-sintered cermet particles was measured using a fluorescent X-ray analysis apparatus “LAB CENTER XRF-1700”, manufactured by Shimadzu Corporation.

The measurement results of the respective average diameters (directed average diameters) of the ceramic particle portions and the metal particle portions in the granulated-sintered cermet particles of each of the powder materials are shown in the columns “Average diameter of ceramic particle portions” and “Average diameter of metal particle portions” in Table 2, respectively. In this measurement, a scanning electron microscope “S-3000N”, manufactured by Hitachi High-Technologies Corporation, was used. Specifically, the average diameter of the ceramic particle portions and the average diameter of the metal particle portions were determined by observing the cross section of each of six granulated-sintered cermet particles having a particle diameter within ±3 μm from the average diameter of the granulated-sintered cermet particles by a reflection electron microscope at 5,000-fold magnification, and using the resulting cross section photograph of each of the particles. For reference, the cross section photographs of the granulated-sintered cermet particles of the powder materials in Example 2 and Comparative Example 2 are shown in FIGS. 2 and 3, respectively.

The value obtained by dividing the average diameter of the metal particle portions by the average diameter of the ceramic particle portions, the average diameters being determined as above with respect to each of the powder materials, is shown in the column “Average diameter of metal particle portions/Average diameter of ceramic particle portions” in Table 2.

The measurement result of the median diameter of pores in the granulated-sintered particles of each of the powder materials is shown in the column “Median diameter of pores” in Table 2. More specifically, the median diameter of the pores was determined by performing a measurement using a mercury intrusion porosimeter “AutoPore IV 9500”, manufactured by Micromeritics, in conditions of a mercury contact angle of 130° and a surface tension of 485 dynes/cm (0.485 N/m), and extracting data of 66 psi (0.045 MPa) or more from the measurement results.

The result obtained by measuring the proportion of granulated-sintered cermet particles exhibiting no breaking point in a stress-strain diagram that was obtained by applying a compressive load that increased up to a maximum value of 981 mN at a loading rate of 12.9 mN/s, to the granulated-sintered cermet particles of each of the powder materials, using a microcompression testing machine (MCTE-500, manufactured by Shimadzu Corporation) is shown in the column “Proportion of cermet particles exhibiting no breaking point” in Table 2. The proportion of the granulated-sintered cermet particles exhibiting no breaking point was calculated as a proportion of granulated-sintered cermet particles exhibiting no breaking point in 12 granulated-sintered cermet particles having a particle diameter of 50 μm or less arbitrarily selected in each of the powder materials.

The process temperature in thermal spraying of each of the powder materials in conditions shown in Table 1 is shown in the column “Thermal spraying temperature” in Table 2.

The value obtained by dividing the weight of a thermal spray coating obtained by thermal spraying of each of the powder materials by the weight of the powder material thermally sprayed is shown on percentage basis in the column “Deposit efficiency” in Table 2.

TABLE 1 Thermal spraying machine: HVOF spraying machine “JP-5000”, manufactured by Praxair/TAFA Inc. Flow rate of oxygen: 1,900 scfh (about 893 L/min) Flow rate of kerosene: 5.1 gph (about 0.32 L/min) Thermal spraying distance: 380 mm Barrel length of thermal spraying machine: 4 inches (about 101.6 mm) Substrate: SS 400 plate blast-treated

TABLE 2 Average Average diameter of Proportion of diameter of Average metal particle cermet particles Thermal Composition ceramic diameter of portions/Average Median exhibiting no spraying Deposit of cermet particle metal particle diameter of ceramic diameter of breaking temperature efficiency particles portions (μm) portions (μm) particle portions pores (μm) point (%) (° C.) (%) Example 1 WC/12% Co 2 0.7 0.35 0.3 25% 1900 49 Example 2 WC/12% Co 0.2 0.14 0.7 0.3 25% 1900 55 Example 3 WC/12% Co 2 0.7 0.35 0.3 13% 1900 48 Example 4 WC/12% Co 2 0.7 0.35 0.3 87% 1900 59 Example 5 WC/10% Co/4% Cr 2 0.7 0.35 0.3 13% 1900 47 Example 6 WC/20% CrC/7% Ni 2 0.7 0.35 0.3 13% 1900 47 Example 7 WC/12% FeCrNi 2 0.7 0.35 0.3 13% 1900 51 Comparative WC/12% Co 2 3 1.5 0.3  0% 1900 44 Example 1 Comparative WC/12% Co 0.7 3 4.3 0.01>  0% 1900 45 Example 2 Comparative WC/12% Co 2 3 1.5 0.01>  0% 1900 37 Example 3 Comparative WC/12% Co 2 3 1.5 2.5  0% 1900 33 Example 4

As shown in Table 2, in the case where each of the powder materials of Examples 1 to 7 was used, high deposit efficiency could be obtained as compared with the case where each of the powder materials of Comparative Examples 1 to 4 was used.

Examples 8 to 11 and Comparative Examples 5 to 7 Cold Spraying

Powder materials of Examples 8 to 11 and Comparative Examples 5 to 7, each of which is composed of granulated-sintered cermet particles, were prepared, and were each thermally sprayed in conditions shown in Table 3. The details of each of the powder materials are shown in Table 4. Although not shown in Table 4, the average diameter of the granulated-sintered cermet particle in each of the powder materials was measured using a laser diffraction/scattering particle size measuring apparatus “LA-300”, manufactured by Horiba Ltd., and all the average diameters were found to be 17 μm.

The chemical composition of the granulated-sintered cermet particle of each of the powder materials is shown in the column “Composition of cermet particle” in Table 4. In this column, “WC/25% FeCrNi” represents a cermet including 25% by mass of an iron-chromium-nickel alloy and the balance of tungsten carbide, and WC/25% FeSiCr” represents a cermet including 25% by mass of an iron-silicon-chromium alloy and the balance of tungsten carbide. The chemical composition of the granulated-sintered cermet particle was measured using a fluorescent X-ray analysis apparatus “LAB CENTER XRF-1700”, manufactured by Shimadzu Corporation.

The measurement results of the respective average diameters (directed average diameters) of the ceramic particle portions and the metal particle portions in the granulated-sintered cermet particles of each of the powder materials are shown in the columns “Average diameter of ceramic particle portions” and “Average diameter of metal particle portions” in Table 4, respectively. In this measurement, a scanning electron microscope “S-3000N”, manufactured by Hitachi High-Technologies Corporation, was used. Specifically, the average diameter of the ceramic particle portions and the average diameter of the metal particle portions were determined by observing the cross section of each of six granulated-sintered cermet particles having a particle diameter within ±3 μm from the average diameter of the granulated-sintered cermet particles by a reflection electron microscope at 5,000-fold magnification, and using the resulting cross section photograph of each of the particles.

The value obtained by dividing the average diameter of the metal particle portions by the average diameter of the ceramic particle portions, the average diameters being determined as above with respect to each of the powder materials, is shown in the column “Average diameter of metal particle portions/Average diameter of ceramic particle portions” in Table 4.

The measurement result of the median diameter of pores in the granulated-sintered particles of each of the powder materials is shown in the column “Median diameter of pores” in Table 4. More specifically, the median diameter of the pores was determined by performing a measurement using a mercury intrusion porosimeter “AutoPore IV 9500”, manufactured by Micromeritics, in conditions of a mercury contact angle of 130° and a surface tension of 485 dynes/cm (0.485 N/m), and extracting data of 66 psi (0.045 MPa) or more from the measurement results.

The result obtained by measuring the proportion of a granulated-sintered cermet particles exhibiting no breaking point in a stress-strain diagram that was obtained by applying a compressive load that increased up to a maximum value of 200 mN at a loading rate of 12.9 mN/s, to the granulated-sintered cermet particle of each of the powder materials, using a microcompression testing machine (MCTE-500, manufactured by Shimadzu Corporation) is shown in the column “Proportion of cermet particles exhibiting no breaking point” in Table 4. The proportion of the granulated-sintered cermet particle exhibiting no breaking point was calculated as a proportion of granulated-sintered cermet particle exhibiting no breaking point in 12 granulated-sintered cermet particles having a particle diameter of 30 μm or less arbitrarily selected in each of the powder materials.

The process temperature in thermal spraying of each of the powder materials in conditions shown in Table 3 is shown in the column “Thermal spraying temperature” in Table 4.

The result obtained by evaluating the deposit efficiency of each of the powder materials based on the thickness of a thermal spray coating formed per passage of the thermal spraying nozzle in thermal spraying of each of the powder materials in conditions shown in Table 3 is shown in the column “Deposit efficiency” in Table 4. Specifically, the case where the thickness of the thermal spray coating formed per passage was 200 μm or more was rated as “Good”, and the case where the thickness was less than 200 μm was rated as “Poor”.

TABLE 3 Thermal spraying machine: low pressure cold spraying apparatus “DYMET”, manufactured by OCPS Type of working gas: air Pressure of working gas: 0.7 MPa Temperature of working gas heater: 500° C. Thermal spraying distance: 20 mm Traverse velocity: 5 mm/sec. Amount of powder material supplied: 15 g/min. Substrate: SS 400 plate blast-treated

TABLE 4 Average Average diameter of Proportion of diameter of Average metal particle cermet particles Thermal Composition ceramic diameter of portions/Average Median exhibiting no spraying of cermet particle metal particle diameter of ceramic diameter of breaking temperature Deposit particles portions (μm) portions (μm) particle portions pores (μm) point (%) (° C.) efficiency Example 8 WC/25% FeCrNi 2 0.7 0.35 0.3 87% 400 Good Example 9 WC/25% FeCrNi 2 0.7 0.35 0.3 25% 400 Good Example 10 WC/25% FeCrNi 2 0.7 0.35 0.3 13% 400 Good Comparative WC/25% FeCrNi 2 3 1.5 0.3  0% 400 Poor Example 5 Comparative WC/25% FeCrNi 0.7 3 4.3 0.01>  0% 400 Poor Example 6 Example 11 WC/25% FeSiCr 2 0.7 0.35 0.3 13% 400 Good Comparative WC/25% FeSiCr 2 3 1.5 0.3  0% 400 Poor Example 7

As shown in Table 4, in the case where each of the powder materials of Examples 8 to 11 was used, high deposit efficiency could be obtained as compared with the case where each of the powder materials of Comparative Examples 5 to 7 was used.

Claims

1. A powder material comprising ceramic-metal composite particles, wherein at least a part of the composite particles exhibit no breaking point in a stress-strain diagram that is obtained by applying a compressive load that increases up to a maximum value of 10 mN or more at a loading rate of 15.0 mN/s or less.

2. The powder material according to claim 1, wherein the composite particles have a proportion of the composite particles exhibiting no breaking point of 10% or more.

3. The powder material according to claim 1, wherein the composite particles each include metal particle portions having an average diameter of 3 μm or less.

4. The powder material according to claim 1, wherein the composite particles each include metal particle portions and ceramic particle portions and have a ratio of an average diameter of the metal particle portions to an average diameter of the ceramic particle portions of less than 1.5.

5. The powder material according to claim 1, wherein the composite particles each include metal particle portions and ceramic particle portions and have a ratio of an average diameter of the metal particle portions to an average diameter of the ceramic particle portions of less than 1.5, and the average diameter of the metal particle portions is 3 μm or less.

6. The powder material according to claim 1, wherein the composite particles each include metal particle portions, and a ratio of an average diameter of the metal particle portions to an average diameter of the composite particles is 0.15 or less.

7. The powder material according to claim 1, wherein the composite particles have an aspect ratio of 1.30 or less.

8. The powder material according to claim 1, wherein the composite particles each include pores having a median diameter of 2.0 μm or less.

9. The powder material according to claim 1, wherein the composite particles have a porosity of 30% or less.

10. The powder material according to claim 1, wherein the powder material is used as a thermal spray powder.

11. The powder material according to claim 10, wherein the powder material is thermally sprayed at a thermal spraying temperature of 3,000° C. or lower.

12. A method for forming a thermal spray coating, comprising thermally spraying the powder material according to claim 1 at a thermal spraying temperature of 3,000° C. or lower.

13. The powder material according to claim 1, wherein the at least a part of the composite particles exhibit no breaking point in a stress-strain diagram that is obtained by applying a compressive load that increases up to a maximum value of 100 mN or more at a loading rate of 15.0 mN/s or less.

14. The powder material according to claim 1, wherein the composite particles each include ceramic particle portions containing at least one selected from tungsten carbide, chromium carbide, molybdenum boride, chromium boride, and aluminum nitride.

15. The powder material according to claim 1, wherein the composite particles each include metal particle portions having a face-centered cubic lattice structure or a body-centered cubic lattice structure.

16. A powder material comprising ceramic-metal composite particles, wherein

at least 10% of the composite particles exhibit no breaking point in a stress-strain diagram that is obtained by applying a compressive load that increases up to a maximum value of 200 mN or more at a loading rate of 15.0 mN/s or less,
the composite particles each include ceramic particle portions containing tungsten carbide and metal particle portions containing cobalt, nickel, iron, or chromium, the composite particles have a ratio of an average diameter of the metal particle portions to an average diameter of the ceramic particle portions of less than 1,
the average diameter of the metal particle portions is 1 μm or less,
a ratio of the average diameter of the metal particle portions to the average diameter of the composite particles is 0.1 or less, and
the composite particles each include pores having a median diameter of 2.0 μm or less.
Patent History
Publication number: 20150147572
Type: Application
Filed: May 17, 2013
Publication Date: May 28, 2015
Inventors: Kazuto Sato (Kiyosu-shi), Hiroaki Hattori (Kiyosu-shi), Junya Yamada (Kiyosu-shi)
Application Number: 14/402,013