JP6796446B2 - Thermal spray coating - Google Patents

Description

The present invention relates to a thermal spray coating, and more particularly to a thermal spray coating preferably used in equipment for transporting coal before pulverization. Examples of equipment for transporting coal before crushing include coal lifting equipment, chutes, and coal storage equipment. Hereinafter, the description will be focused on use in coal transportation equipment, but the application of the thermal spray coating of the present invention is not limited to this.

Coal carried by ship is landed, stored in a coal storage yard, and then transported to a power plant or the like. The coal includes powders having a particle size of about several μm and lumps having a diameter of about ten and several centimeters.

In the process of unloading the above coal from a ship and transporting it to a power plant, etc. via a storage yard, coal unloading equipment such as stackers and reclaimers, coal transportation equipment such as conveyors, coal storage equipment equipped with chutes, bunker, etc. Coal transport equipment is used. When coal collides with a coal transportation facility, it may be damaged and the facility may crack.

Therefore, in order to improve the wear resistance of the surface of the coal transport facility that comes into contact with coal and protect the coal transport facility, a method of forming a hard film (thermal spray coating) on the surface of the facility by a thermal spraying method is adopted. In the thermal spraying method, for example, powders such as metal, ceramics, and cermet (composite of metal and ceramics) are melted by a plasma flame or a combustion flame of a flammable gas, and the molten particles are sprayed onto the surface of the base material. Is a technique for depositing a film on the surface of a base material and forming a film.

As a technique related to the thermal spray coating, for example, Patent Documents 1 to 6 are known.

In Patent Document 1, the component composition of the sprayed coating is WC-Co-Cr, and the relationship between the Co content and the Cr content is appropriately defined, so that both slurry wear resistance and cavitation corrosion resistance are obtained. A component of a flue gas desulfurization apparatus with improved characteristics has been proposed.

According to Patent Document 2, a film formed by spraying and coating a mixed powder of 20 to 80% by weight of WC and the balance of a Ni—Cr self-dissolving alloy on the surface of the body of the roll and remelting the surface. Described is a conductor roll for an electroplating line in which WC particles mixed in the layer are deformed into an elliptical shape and the major axis of the WC particles is arranged in parallel with the coating layer. This conductor roll is described as having less shedding of metal carbide particles.

Patent Document 3 describes a hydrochloric acid-based plating solution or acid by spraying a mixed powder consisting of WC-Ni cermet and the balance Ni-based self-dissolving alloy on the roll surface and then remelting to form a film layer. It has excellent corrosion resistance and wear resistance to washing liquid or washing liquid, maintains a dense film layer that does not cause scratches due to WC dropout for a long time, and repeats the cycle of polishing the film surface and reusing it three or more times. Techniques that provide corrosion resistant rolls that are possible are described. Further, it is described that the remelting treatment is performed at, for example, 1100 ° C.

In Patent Document 4, chromium: 12 to 20%, boron: 2.5 to 4.5%, silicon: 2.0 to 5.0%, carbon: 0.4 to 1.1% by weight on the surface. , Iron: 5% or less, cobalt: 1% or less, molybdenum: 4% or less, copper: 4% or less, and the balance is composed of nickel containing unavoidable impurities. A coated rotor for a rubber kneader is described. It is stated that this rotor has excellent wear resistance and corrosion resistance, has a long life, is easy to manufacture, and has a low cost. In manufacturing the rotor, it is described that after the thermal spray coating is formed, it is heated to 1000 ° C. or higher to perform fusing to seal fine pores in the thermal spray coating.

Patent Document 5 describes a conductor roll having excellent corrosion resistance and wear resistance, in which a self-melting alloy sprayed layer containing WC cermet is formed on the roll surface and a WC cermet layer is further formed on the self-melting alloy sprayed layer. .. The autolytic alloy described in Patent Document 5 is a Ni-based alloy containing Cr, B, and Si.

Patent Document 6 describes a method for manufacturing a protector for a metal member, which is excellent in wear resistance and corrosion resistance, is excellent in adhesion of a coating film to a base material, has small deflection, and is also excellent in linearity. ing. In this manufacturing method, an autolyzed alloy is sprayed on one surface of a plate-shaped protector base material to form a sprayed coating, which is then remelted at a temperature of about 1000 to 1100 ° C. to form a dense coating (autolytic alloy layer). It is said. A Ni-based alloy is mentioned as a preferable autolytic alloy.

Japanese Patent No. 5814857 Japanese Unexamined Patent Publication No. 5-9699 JP-A-2002-88461 Japanese Unexamined Patent Publication No. 2003-277861 Japanese Unexamined Patent Publication No. 2006-183107 Japanese Unexamined Patent Publication No. 2016-864

The WC-Co-Cr-based thermal spray coating described in Patent Document 1 is excellent in slurry wear resistance, but cannot withstand an environment in which agglomerated coal collides one after another. Cracks occur and peeling occurs.

The above-mentioned Patent Documents 2 to 6 describe a thermal spray coating obtained by spraying a self-dissolving alloy containing Ni. A sprayed coating using a self-dissolving alloy containing Ni is subjected to a remelting treatment at about 1000 ° C. after spraying the self-dissolving alloy, so that it is difficult to peel off from the base material and has excellent corrosion resistance. However, since the base material is distorted by the high temperature heat treatment for remelting, it is difficult to apply it to the product after molding. Further, since heat treatment at a high temperature is required, it is difficult to apply it to a large facility such as a coal transport facility. Further, when a hard heat-treated steel such as martensitic steel or duplex stainless steel is used as the base material for forming the spray-coated film, the base material is softened or the strength is lowered due to the heat treatment. Difficult to apply.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thermal spray coating having excellent wear resistance, impact resistance, fusing resistance, and corrosion resistance.

The thermal spray coating according to the present invention that has been able to solve the above problems is a thermal spray coating in which the total amount of W and C is 20% by mass or more with respect to the entire thermal spray coating, and the thermal spray coating is tungsten carbide. , And a first phase containing a metal binder and satisfying a total amount of W and C of 70% by mass or more, and a total amount of Ni, Cr, B, and Si containing Ni, Cr, B, and Si. Containes at least a second phase satisfying 80% by mass or more, the first phase contains tungsten carbide particles, and when the thermal spray coating is observed in the thickness direction, the tungsten carbide particles become the first phase. The point is that the area ratio of the occupied area is 60% or more.

The metal binder preferably contains at least one selected from the group consisting of Co and Cr.

The component composition of the sprayed coating is, for example, W: 18 to 64%, Cr: 6 to 15%, C: 2 to 5%, Si: 1 to 4%, B: 1 to 4%, and, in mass%. Examples thereof include those containing Co: 2 to 9% and the balance: Ni and unavoidable impurities.

The tungsten carbide particles contained in the first phase preferably have a circle-equivalent diameter of 0.1 to 5 μm. A tungsten carbide-containing cermet film may be further formed on the surface of the sprayed coating. The film thickness of the sprayed coating is preferably 0.4 to 2 mm.

The present invention also includes a member for coal transportation equipment in which the thermal spray coating is formed on the surface of a base material.

According to the present invention, the sprayed coating in which the total amount of W and C satisfies 20% by mass or more with respect to the entire sprayed coating contains tungsten carbide and a metal binder, and the total amount of W and C is 70 mass. A sprayed coating containing at least a first phase satisfying% or more and a second phase containing Ni, Cr, B, and Si and satisfying a total amount of Ni, Cr, B, and Si of 80% by mass or more. The first phase contains tungsten carbide particles, and when the thermal spray coating is observed in the thickness direction, the area ratio of the region occupied by the tungsten carbide particles in the first phase is 60% or more. It is possible to provide a sprayed coating having excellent wear resistance, impact resistance, fusing resistance, and corrosion resistance.

FIG. 1A shows No. 1 shown in Table 1. The drawing substitute photograph in which No. 3 was taken, FIG. 1 (b) is No. 1 shown in Table 1. The drawing substitute photograph which took 8 is shown respectively.

The present inventors have been diligently studying the thermal spray coating used in coal transportation equipment in order to improve all the properties of wear resistance, impact resistance, fusing resistance, and corrosion resistance. As a result, with respect to the sprayed coating in which the total amount of W and C satisfies 20% by mass or more with respect to the entire sprayed coating, the sprayed coating contains tungsten carbide and a metal binder, and the total amount of W and C is increased. A film containing at least a first phase satisfying 70% by mass or more and a second phase containing Ni, Cr, B, and Si and having a total amount of Ni, Cr, B, and Si satisfying 80% by mass or more. In addition, the first phase contains tungsten carbide particles, and when the cross section of the sprayed coating in the thickness direction is observed, the area ratio of the region occupied by the tungsten carbide particles in the first phase is 60% or more. Then, it was found that all the above characteristics could be improved, and the present invention was completed.

In the present invention, "tungsten carbide" refers to all compounds such as WC and W ₂ C in which C is bonded to W to form a carbide. Further, in the present invention, the "tungsten carbide particles" mean particles in which the total amount of W and C satisfies 90% by mass or more.

First, the background to the completion of the present invention will be described.

The WC cermet sprayed coating described in Patent Document 1 contains a metal binder such as Co or Cr in addition to WC in order to prevent wear due to a fluid (slurry) containing earth and sand. However, when this WC cermet sprayed coating is used in coal transportation equipment, the sprayed coating cracks due to the impact of coal collision and peeling occurs, and at the peeled part, the interface between the base material and the sprayed coating corrodes. Floating of the sprayed coating occurred.

Further, when the thermal spray coating is formed by using the self-dissolving alloy described in Patent Documents 2 to 6, high temperature heat treatment is required, so that the WC particles form a metal phase and a double carbide, or the WC particles. Is decomposed and eluted into the metal phase, so that the number of high-purity WC particles is reduced, and the abrasion resistance and impact resistance are lowered.

Therefore, in the present invention, studies have been repeated in order to effectively exert the characteristics of both the tungsten carbide cermet sprayed coating and the sprayed coating using a self-melting alloy, and the total amount of W and C is calculated with respect to the entire sprayed coating. The sprayed coating satisfying 20% by mass or more contains tungsten carbide, a metal binder, and a first phase in which the total amount of W and C satisfies 70% by mass or more, and Ni, Cr, B, and Si. In addition, the film contained at least the second phase in which the total amount of Ni, Cr, B, and Si was 80% by mass or more. By forming the second phase, the fusing property and corrosion resistance of the sprayed coating can be improved. Further, the first phase contains tungsten carbide particles, and when the cross section in the thickness direction of the sprayed coating was observed, the area ratio of the region occupied by the tungsten carbide particles in the first phase was set to 60% or more. Then, by forming the first phase in which the tungsten carbide particles are present in a predetermined amount on the sprayed coating as described above, it is possible to impart further impact resistance in addition to the abrasion resistance which is an advantage of the tungsten carbide cermet sprayed coating. found.

Such a thermal spray coating of the present invention is suitably formed by a high-speed frame thermal spraying method. That is, according to the high-speed frame thermal spraying method, for example, since the construction can be performed at a relatively low temperature and high speed as compared with the plasma thermal spraying method, it is possible to suppress the formation of double carbides by tungsten carbide and the decomposition of tungsten carbide, and thermal spraying. Tungsten carbide can be present in the film in a highly pure state. Further, by omitting the heat treatment at a high temperature performed in Patent Documents 2 to 6, the tungsten carbide particles can be allowed to exist in the sprayed coating as they are. As a result, both wear resistance and impact resistance can be improved, and fusing resistance and corrosion resistance can also be improved.

As described in Patent Document 1, the WC-Co-Cr-based sprayed coating is excellent in slurry wear resistance, and as described in Patent Documents 2 to 6, Ni It is known that a sprayed coating obtained by spraying a self-dissolving alloy containing the above has excellent corrosion resistance, but these cannot be combined because the conditions for forming the sprayed coating, such as the presence or absence of remelting treatment, are different. Even if they are combined, a thermal spray coating that clearly shows the difference between the first phase and the second phase specified in the present invention cannot be formed.

Hereinafter, the thermal spray coating according to the present invention will be described.

Since the sprayed coating of the present invention satisfies the total amount of W and C of 20% by mass or more with respect to the entire sprayed coating, it has excellent wear resistance. If the total amount of W and C is less than 20% by mass, the amount of tungsten carbide particles described later cannot be secured, so that the wear resistance cannot be improved. The upper limit of the total amount of W and C is not particularly limited, but is preferably 70% by mass or less, for example.

The sprayed coating contains at least the first phase and the second phase. Hereinafter, the second phase will be described first, and then the first phase will be described.

(Phase 2)
The second phase is a phase containing Ni, Cr, B, and Si, and the total amount of Ni, Cr, B, and Si satisfies 80% by mass or more. By containing Ni, Cr, B, and Si in a total amount of 80% by mass or more with respect to the second phase, the fusing property and corrosion resistance of the sprayed coating can be improved. In particular, the presence of a self-dissolving alloy containing Ni in the sprayed coating improves the adhesion between the sprayed coating and the base material. Therefore, even if the sprayed coating is melted after being formed, the sprayed coating can be peeled off. It can be suppressed and the fusing property can be improved.

The upper limit of the total amount of Ni, Cr, B, and Si in the second phase is not particularly limited, but may be 100% by mass. That is, the second phase may be a phase composed of Ni, Cr, B, and Si.

The second phase may further contain elements such as W, C, Co, Cu, Mo, and Fe as other elements. In this case, the total amount of Ni, Cr, B, and Si in the second phase may be, for example, 95% by mass or less.

(Phase 1)
The first phase is a phase containing tungsten carbide and a metal binder, and the total amount of W and C satisfies 70% by mass or more. The wear resistance of the sprayed coating can be improved by containing tungsten carbide and a metal binder and satisfying a total amount of W and C of 70% by mass or more.

The upper limit of the total amount of W and C in the first phase is not particularly limited, but may be, for example, 90% by mass or less.

The first phase may further contain elements such as Ni, Co, Cr, Cu, Mo, Fe, B, and Si as other elements.

The metal binder is a substance having an action of adhering hard and brittle tungsten carbide.

The metal binder preferably contains, for example, at least one selected from the group consisting of Co and Cr. Co and Cr are elements useful as binder metals. In particular, since Co has excellent ductility, the toughness of the sprayed coating can be ensured. On the other hand, Cr contributes to the improvement of the corrosion resistance of the sprayed coating. It is more preferable to contain both Co and Cr.

The first phase needs to contain tungsten carbide particles, and when the cross section in the thickness direction of the sprayed coating is observed, the area ratio of the region occupied by the tungsten carbide particles in the first phase is 60% or more. It is important to be. Impact resistance can be improved by setting the area ratio of the tungsten carbide particles in the first phase to 60% or more.

The first phase preferably contains a plurality of the tungsten carbide particles. When the first phase contains a plurality of tungsten carbide particles, the total area ratio of the region occupied by the plurality of tungsten carbide particles in the first phase is preferably 60% or more. The plurality of particles means two or more particles, and the upper limit of the number of tungsten carbide particles is not particularly limited. The ratio of W and C is not particularly limited.

The area ratio of the region occupied by the tungsten carbide particles with respect to the first phase can be calculated, for example, by observing the cross section of the sprayed coating in the thickness direction with a scanning electron microscope and image-analyzing the captured reflected electron image. When the cross section of the sprayed coating of the present invention is observed with a scanning electron microscope, a first phase satisfying the above requirements and a second phase satisfying the above requirements can be identified based on the brightness. The first phase is observed as a relatively light color and the second phase is observed as a relatively dark color. A person skilled in the art can visually distinguish and identify the first phase and the second phase because the difference in weight of the atoms occupying them is large and the light and darkness is clear.

For the identified first phase, a region in which the tungsten carbide particles are present is selected using an electron probe microanalyzer (EPMA), and the region occupied by the tungsten carbide particles having the same brightness as the tungsten carbide particles is occupied. It can be regarded as such, and the area ratio may be calculated. As the tungsten carbide particles, as described above, particles having a total amount of W and C of 90% by mass or more may be selected.

If the number of observation points in the first phase is small, the measurement error becomes large. Therefore, it is preferable to select five or more points for selecting the brightness and average the measurement results.

The tungsten carbide particles contained in the first phase preferably have a circle-equivalent diameter of 0.1 to 5 μm. In general, the film to which tungsten carbide is added has improved wear resistance as compared with the case where it is not added, but when the equivalent circle diameter of the tungsten carbide particles is 0.1 to 5 μm, many fine tungsten carbide particles are present. Since the phase is formed, the impact resistance to fine coal particles is improved. If only tungsten carbide particles having a small particle size are used, the effect of improving wear resistance may not be sufficiently exhibited. Therefore, the equivalent circle diameter of the tungsten carbide particles is preferably 0.1 μm or more, more preferably 1 μm or more. However, with only tungsten carbide particles having a large particle size, when a large number of small and hard coal particles collide with each other, the metal binder existing in the gap between the tungsten carbide particles may wear and the wear resistance may decrease. Therefore, the equivalent circle diameter of the tungsten carbide particles is preferably 5 μm or less, more preferably 4 μm or less.

The component composition of the entire sprayed coating is not particularly limited as long as the total amount of W and C is 20% by mass or more with respect to the entire sprayed coating, but in mass%, W: 18 to 64%, Cr: 6 to It is preferable to satisfy at least one requirement selected from the group consisting of 15%, C: 2 to 5%, Si: 1 to 4%, B: 1 to 4%, or Co: 2 to 9%, and all of them. It is more preferable to meet the requirements. W is more preferably 47% or more. Cr is more preferably 9% or less. C is more preferably 3% or more. Si is more preferably 3% or less. B is more preferably 2% or less. Co is more preferably 6% or more.

The rest of the sprayed coating is Ni and unavoidable impurities.

A tungsten carbide-containing cermet film may be further formed on the surface of the sprayed coating. The cermet is a composite material obtained by molding and sintering ceramic particles and metal powder particles, and the tungsten carbide-containing cermet film means a film containing tungsten carbide and a metal binder.

The metal binder contained in the tungsten carbide-containing cermet film preferably contains at least one selected from the group consisting of Ni, Co, Cr and Fe.

The thermal spray coating preferably has a film thickness of 0.4 to 2 mm. By setting the film thickness to 0.4 mm or more, the effect of improving wear resistance against collision of coal lumps is sufficiently exhibited. The film thickness of the sprayed coating is more preferably 0.8 mm or more. However, if the film thickness of the sprayed coating is made too large, it tends to peel off from the surface of the base material. Therefore, the film thickness of the sprayed coating is preferably 2 mm or less, more preferably 1.5 mm or less.

The film thickness of the sprayed coating means the film thickness of a single layer in the case of a single layer, and the total film thickness in the case of a plurality of layers of two or more layers.

The present invention also includes a member for coal transportation equipment in which the thermal spray coating is formed on the surface of a base material.

The type of the above-mentioned base material is not particularly limited, but in addition to general structural steel, low alloy steel, and austenitic stainless steel, since high temperature construction is not required in the present invention, carbon steel and tool steel after tempering, Precipitate hardening type stainless steel, martensite type stainless steel, copper alloy, aluminum alloy and the like can be mentioned.

Next, a method for producing the thermal spray coating according to the present invention will be described.

The thermal spray coating contains a first powder containing tungsten carbide and a metal binder, and the total amount of W and C satisfies 70% by mass or more.
A second powder containing Ni, Cr, B, and Si and satisfying a total amount of Ni, Cr, B, and Si of 80% by mass or more.
It can be formed by spraying a mixed powder prepared so that the total amount of W and C satisfies 20% by mass or more with respect to the entire mixed powder by a high-speed frame thermal spraying method.

The first powder may contain unavoidable impurities in addition to tungsten carbide and a metal binder.

The second powder may contain elements such as C, Co, Cu, Mo and Fe in addition to Ni, Cr, B and Si.

High-speed frame thermal spraying [High Velocity Oxy-Fuel (HVOF) thermal spraying method] is to burn flammable gas such as acetylene and propane or liquid fuel such as kerosene at high pressure and eject it from a nozzle as a supersonic frame. This is a thermal spraying method in which a powdered thermal spray material is put into the spray material, accelerated at a high speed, and deposited on a substrate to form a film. The particle velocity of the sprayed material to be accelerated is as high as 500 to 800 m / sec.

Since the frame temperature at the time of high-speed frame spraying is about 2000 to 3000 ° C. and the sprayed material is sprayed at high speed, tungsten carbide is hardly decomposed and composite carbide of tungsten carbide is hardly formed. Therefore, there is a region where tungsten carbide is concentrated in the sprayed coating, and in addition to wear resistance, impact resistance can be improved. On the other hand, for example, since the frame temperature at the time of plasma spraying is about 9000 ° C. or higher, tungsten carbide is decomposed or a composite carbide of tungsten carbide is easily formed, so that the sprayed coating of the present invention can be formed. Is not appropriate.

After forming the above-mentioned thermal spray coating, a third powder containing tungsten carbide and a metal binder may be further sprayed to form a tungsten carbide-containing cermet film.

The third powder may have the same composition as the first powder, or may have a different composition.

As the thermal spraying method, the high-speed frame thermal spraying method is preferable as described above.

The thermal spray coating according to the present invention can be used, for example, in coal transportation equipment. Specifically, it may be used for equipment that transports coal after crushing, but is particularly preferably used for equipment that transports coal before crushing. Examples of equipment for transporting coal before crushing include coal lifting equipment such as stackers and reclaimers, coal transportation equipment such as conveyors, and coal storage equipment equipped with chutes and bunkers. The thermal spray coating of the present invention may be formed at a location in contact with coal (for example, a wall surface, a bottom surface, a pipe, etc.) in such equipment.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples, and the present invention shall be carried out with modifications to the extent that it can be adapted to the gist of the above and the following. Of course, they are all within the technical scope of the present invention. In the following, with respect to the components,% means mass%.

A thermal spray coating coating member having a thermal spray coating formed on the surface of the base material was produced, and the wear resistance, impact resistance, fusing resistance, and corrosion resistance of the thermal spray coating were evaluated.

First, the conditions for forming the thermal spray coating will be described.

(No. 1)
A carbon steel sheet was prepared as a base material, and a thermal spray coating coating member having a thermal spray coating formed on the surface of the base material was manufactured.

The thermal spray coating was formed by a high-speed frame thermal spraying method (HVOF thermal spraying method) using a raw material powder in which 20% of tungsten carbide cermet powder and 80% of Ni-based alloy powder were mixed. As the tungsten carbide cermet powder, WC-14% Co-6% Cr was used. As the Ni-based alloy powder, Ni-16% Cr-4% Si-3.5% B-0.6% C was used. The thermal spray coating was formed so as to have the film thickness shown in Table 1 below.

The conditions for high-speed frame spraying are as follows.
<Conditions for high-speed frame spraying>
Thermal spraying device: "JP5000" manufactured by TAFA
Barrel length: 8 inch
Oxygen flow rate: 2000 scfh
Kerosene flow rate: 6.0 gp
Thermal spraying distance: 400 mm

(No. 2)
No. In No. 2, except that a powder obtained by mixing 40% of tungsten carbide cermet powder and 60% of Ni-based alloy powder is used as the raw material powder. A thermal spray coating coating member was manufactured under the same conditions as in 1.

(No. 3)
No. In No. 3, except that a powder obtained by mixing 60% of tungsten carbide cermet powder and 40% of Ni-based alloy powder is used as the raw material powder. A thermal spray coating coating member was manufactured under the same conditions as in 1.

(No. 4)
No. In No. 4, except that a powder obtained by mixing 80% of tungsten carbide cermet powder and 20% of Ni-based alloy powder is used as the raw material powder. A thermal spray coating coating member was manufactured under the same conditions as in 1.

(No. 5)
No. In No. 5, a thermal spray coating coating member in which two thermal spray coatings were laminated on the surface of the base material was manufactured. Specifically, on the surface of the base material, as a lower layer, the above No. After forming the thermal spray coating shown in No. 3, as an upper layer, No. The thermal spray coating shown in No. 7 was formed.

(No. 6)
No. In No. 6, except that only Ni-based alloy powder is used as the raw material powder. A thermal spray coating coating member was manufactured under the same conditions as in 1.

(No. 7)
No. In No. 7, the above No. 7 was used, except that only tungsten carbide cermet powder was used as the raw material powder. A thermal spray coating coating member was manufactured under the same conditions as in 1.

(No. 8)
No. In No. 8, except that the thermal spray coating is formed by the plasma spraying method instead of the high-speed frame thermal spraying method (HVOF thermal spraying). A thermal spray coating coating member was manufactured under the same conditions as in 2. The conditions for plasma spraying are as follows.
<Plasma spraying conditions>
Thermal spraying device: "F4" manufactured by Sulzer Metco
Nozzle diameter: φ6 mm
Argon gas + hydrogen flow rate: 60NLPM
Torch input: 40kW
Thermal spraying distance: 150 mm

Next, the cross section of the sprayed coating formed on the surface of the substrate in the thickness direction was observed with a scanning electron microscope at an observation magnification of 500 times, and the component composition of the sprayed coating was analyzed with EPMA. The analysis results are shown in Table 1 below. Table 1 below also shows the results of calculating the total amount of W and C with respect to the entire sprayed coating.

In addition, No. In No. 5, the component composition of the thermal spray coating formed as the lower layer is No. 1 shown in Table 1 below. It is the same as No. 3 and the component composition of the sprayed coating formed as the upper layer is No. 1 shown in Table 1 below. It is the same as 7.

Next, a cross section in the thickness direction of the thermal spray coating formed on the surface of the base material was observed with a scanning electron microscope at an observation magnification of 2000 times and photographed.

The photograph taken was image-analyzed and the A phase containing tungsten carbide and a metal binder and the B phase containing Ni, Cr, B, and Si were identified based on the brightness. Phase A was observed as white or light gray with white particles, and phase B was observed as black or dark gray. As a result, the No. 1 shown in Table 1 below. The sprayed coatings 1 to 4 and No. 1 shown in Table 1 below. The A phase and the B phase were observed in the lower layer portion of the sprayed coating of 5.

Next, the component compositions of the A phase and the B phase were analyzed by EPMA. As a result, in each sample, the total amount of W and C contained in the A phase was 70% by mass or more, and the total amount of Ni, Cr, B, and Si contained in the B phase was 80% by mass or more. I found that I was satisfied. That is, the A phase was identified as the first phase, and the B phase was identified as the second phase.

Regarding the identified first phase, the component composition of the region (hereinafter, may be referred to as WC region) in which the total amount of W and C satisfies 90% by mass or more of the tungsten carbide particles occupies a large amount, and Co and Cr are contained. , The component composition of the metal binder moiety in which the total amount of W and C was less than 90% by mass was analyzed by EPMA, respectively. The analysis was performed at 5 points each, and the average value of each component was calculated. The analysis results are shown in Table 1 below.

As shown in Table 1 below, the region dominated by the tungsten carbide particles was mostly composed of W and C, and the metal binder portion was mostly composed of W, Co, and Cr. In addition, the identified first phase contained a plurality of tungsten carbide particles in which the total amount of W and C was 90% by mass or more.

The total area ratio of the tungsten carbide particles satisfying 90% by mass or more of the total amount of W and C with respect to the identified first phase was calculated by image analysis. For the total area ratio of the tungsten carbide particles, the brightness at a position where the total amount of W and C is 90% by mass or more is measured by image analysis, and the region showing the same brightness as the brightness is regarded as the range occupied by the tungsten carbide particles. The ratio in the whole was calculated. The results are shown in Table 1 below.

The component composition of the identified second phase was analyzed by EPMA. The analysis was performed at 5 points each, and the average value of each component was calculated. The analysis results are shown in Table 1 below. Further, in Table 1 below, the total amount of Ni, Cr, B, and Si in the second phase was calculated and shown together.

No. 1 shown in Table 1 below. The drawing substitute photograph of No. 3 is shown in FIG. 1 (a). Substitute photographs of drawings taken in FIG. 8 are shown in FIG. 1 (b).

Further, a cross section of the thermal spray coating formed on the surface of the base material in the thickness direction was observed with a scanning electron microscope at an observation magnification of 2000 times and photographed. The photograph taken was image-analyzed, and the diameter equivalent to the circle of the tungsten carbide particles was measured. As a result, the No. 1 shown in Table 1 below. In each of the sprayed coatings 1 to 4, the diameter equivalent to a circle of the tungsten carbide particles was 0.1 to 5 μm. In addition, the No. 1 shown in Table 1 below. In the thermal spray coating of No. 5, the equivalent circle diameter of the tungsten carbide particles existing in the lower layer portion was 0.1 to 5 μm.

Next, the characteristics of the obtained thermal spray coating coating member were evaluated by the following procedure.

In addition, No. of Table 2 below. No. 9 shows the results of evaluating the wear resistance and the corrosion resistance as the characteristics of the base material for comparison.

<Abrasion resistance>
The wear resistance of the thermal spray coating coating member was evaluated by performing a Suga wear test.

For the Suga wear test, a Suga wear tester manufactured by Suga Test Instruments Co., Ltd. was used, and based on JIS H8503 (reciprocating motion wear test), the abrasive paper was # 320SiC, the load was 3.25 kgf, and the number of reciprocating times was 2000. The amount of wear (mg) was measured. The measurement results are shown in Table 2 below.

In addition, the wear resistance was evaluated according to the following criteria based on the amount of wear. The evaluation results are shown in Table 2 below.
(Evaluation criteria)
⊚: The amount of wear is 20 mg or less, and the wear resistance is particularly excellent (passed).
◯: The amount of wear is more than 20 mg and 50 mg or less, and the wear resistance is excellent (passed).
Δ: The amount of wear is more than 50 mg and 100 mg or less, and the wear resistance is good (passed).
X: The amount of wear is more than 100 mg, and the wear resistance has not been improved (failed).

<Impact resistance>
The impact resistance of the sprayed coating member was evaluated based on the presence or absence of cracks in the sprayed coating by performing a steel ball drop impact test.

The steel ball drop impact test was carried out by dropping a steel ball from a height of 2 m toward the thermal spray coating and applying an impact. As the steel ball, a steel ball made of SUJ2 having a diameter of 38 mm and a weight of about 220 g was used. The steel ball was repeatedly dropped 200 times at the same position on the sprayed coating. The surface of the film after being dropped 200 times was confirmed for cracks by a penetrant inspection test.

Based on the results of the penetrant inspection test, the impact resistance was evaluated according to the following criteria. The evaluation results are shown in Table 2 below.
(Evaluation criteria)
◯: If there was no crack, or if there was a crack but it was fine and it was difficult to determine whether it was a crack, it was passed and evaluated as having excellent impact resistance.
X: When large cracks spreading in a radial pattern occurred, it was rejected, and it was evaluated that the impact resistance could not be improved.

<Fusing property>
The fusing property of the thermal spray coating coating member was evaluated based on the peeling state of the thermal spray coating by cutting the thermal spray coating coating member into a circle by gas cutting or plasma cutting, observing the cut portion.

Gas cutting was performed with oxygen-acetylene using a low-pressure manual gas cutting device manufactured by Chiyoda Seiki Co., Ltd. Plasma cutting was performed with a current value of 60 A using a plasma cutting machine (air plasma) manufactured by Daihen Corporation.

The peeled state of the sprayed coating was evaluated according to the following criteria.
(Evaluation criteria)
◯: Passed because the sprayed coating was chipped or peeled off at the cut part by 2 mm or less.
X: Failed because the sprayed coating was chipped at the cut part and the peeling was more than 2 mm.

Based on the results of gas cutting and plasma cutting, the fusing property was evaluated according to the following criteria. The evaluation results are shown in Table 2 below.
(Evaluation criteria)
◯: Excellent fusing property because it passed both gas cutting and plasma cutting.
X: Since at least one of gas cutting and plasma cutting failed, the fusing property could not be improved.

<Corrosion resistance>
The corrosion resistance of the thermal spray coating coating member was evaluated based on the two test results.

(Corrosion resistance test 1)
A cas test (CASS test; copper-accelerated acetic acid salt spray test) specified in JIS H8502 was performed to confirm the presence or absence of rust.

The CASS test is a continuous spray test performed using a solution of cupric chloride (II) dihydrate added to an acetic acid-acidic sodium chloride solution. The continuous spray test was carried out using a solution containing sodium chloride: 50 g / L and cupric chloride (II) hydrate: 0.205 g / L, the pH of which was adjusted to 3.0 with acetic acid. The test was conducted at 50 ° C.

The equipment specified in JIS Z2371 was used for the CASS test. The test time was 48 hours, and the surface of the test piece was visually observed at each time point 1 hour, 5 hours, 24 hours, and 48 hours after the start of the test to confirm the presence or absence of rust. Based on the confirmation results, evaluation was made according to the following criteria. The evaluation results at each time point are shown in Table 2 below.
(Evaluation criteria)
◯: No rust occurred and passed.
×: Fail due to rust.

(Corrosion resistance test 2)
Half of the area of the test piece was immersed in a sulfuric acid aqueous solution having a concentration of 20%, and the presence or absence of rust was confirmed. The test was conducted at 50 ° C. The test time was 96 hours, and the surface of the test piece was visually observed at each time point 24 hours, 48 hours, 72 hours, and 96 hours after the start of the test, and the presence or absence of rust and the peeling of the sprayed coating were observed. I confirmed the presence or absence of. Based on the confirmation results, evaluation was made according to the following criteria. The evaluation results at each time point are shown in Table 2 below.
(Evaluation criteria)
◯: Passed because no rust was generated and no peeling of the sprayed coating was observed.
×: Fail due to rust.
XX: Failed because the sprayed coating was peeled off.

Based on the evaluation results of the corrosion resistance test 1 and the corrosion resistance test 2, the corrosion resistance was evaluated according to the following criteria.
(Evaluation criteria)
◯: Corrosion resistance is excellent because the result after 48 hours has passed in the corrosion resistance test 1 and the result after 96 hours has passed in the corrosion resistance test 2.
X: Corrosion resistance has not been improved because the result after 48 hours has passed in the corrosion resistance test 1 or the result after 96 hours has failed in the corrosion resistance test 2.

Based on the evaluation results of wear resistance, impact resistance, fusing resistance, and corrosion resistance, the characteristics of the thermal spray coating coating member were comprehensively evaluated according to the following criteria.
(Comprehensive evaluation)
◯: Examples of inventions evaluated as acceptable in all of wear resistance, impact resistance, fusing resistance, and corrosion resistance.
X: Comparative example in which at least one of wear resistance, impact resistance, fusing resistance, and corrosion resistance was evaluated as rejected.

It can be considered from Table 2 below as follows.

No. Reference numerals 1 to 5 are examples that satisfy the requirements specified in the present invention, and are excellent in all of wear resistance, impact resistance, fusing resistance, and corrosion resistance.

On the other hand, No. Reference numerals 6 to 9 are examples that do not satisfy any of the requirements specified in the present invention, and at least one of the properties of wear resistance, impact resistance, fusing resistance, and corrosion resistance cannot be improved.

First, No. Reference numeral 9 denotes a carbon steel sheet used as a base material, which does not form a thermal spray coating. In the Suga wear test, the amount of wear was large, so the wear resistance was inferior. In addition, rust was generated in both the corrosion resistance test 1 and the corrosion resistance test 2, and the corrosion resistance was poor.

No. No. 6 is an example in which a Ni-based alloy film was formed on the surface of the base material by a high-speed frame spraying method. Compared with No. 9, the corrosion resistance could be improved, and the impact resistance and the fusing resistance were also good. However, since tungsten carbide was not blended, the wear resistance could not be improved.

No. No. 7 is an example in which a WC-CoCr film was formed on the surface of the base material by a high-speed frame spraying method. Compared with 9, the wear resistance could be improved. However, since the Ni-based alloy was not used, the corrosion resistance could not be improved. Moreover, the impact resistance and the fusing property were poor.

No. No. 8 is an example in which a thermal spray coating was formed on the surface of the base material by a plasma spraying method. Compared with 9, the wear resistance could be improved. In addition, the fusing property was also good. However, since a part of tungsten carbide is decomposed or a composite carbide is formed at the time of thermal spraying, the total area ratio of the region occupied by the tungsten carbide particles in the first phase does not satisfy 60% or more, and the impact resistance is improved. could not. In addition, No. In No. 8, the degree of flatness of the particles constituting the sprayed coating is low, and many penetrating pores are present in the sprayed coating, so that the environmental blocking property is inferior. As a result, in the CASS test, the base material was rusted, and in the sulfuric acid immersion test, the interface between the base material and the sprayed coating was corroded and peeled off.

Claims (6)

It is a thermal spray coating in which the total amount of W and C satisfies 20% by mass or more with respect to the entire thermal spray coating.
The sprayed coating is
A first phase containing tungsten carbide and a metal binder and satisfying a total amount of W and C of 70% by mass or more.
It contains at least a second phase containing Ni, Cr, B, and Si and satisfying a total amount of Ni, Cr, B, and Si of 80% by mass or more.
The first phase contains tungsten carbide particles having a circle-equivalent diameter of 0.1 to 5 μm .
A thermal spray coating used in coal transportation equipment, wherein the area ratio of the region occupied by the tungsten carbide particles in the first phase is 60% or more when the cross section in the thickness direction of the thermal spray coating is observed. The thermal spray coating according to claim 1, wherein the metal binder contains at least one selected from the group consisting of Co and Cr. By mass%
W: 18-64%,
Cr: 6 to 15%,
C: 2-5%,
Si: 1-4%,
B: 1 to 4%, and Co: 2 to 9%,
The balance: The thermal spray coating according to claim 1 or 2, which comprises Ni and unavoidable impurities. The thermal spray coating according to any one of claims 1 to 3, wherein a tungsten carbide-containing cermet film is further formed on the surface. The thermal spray coating according to any one of claims 1 to 4 , wherein the film thickness is 0.4 to 2 mm. A member for coal transportation equipment, wherein the thermal spray coating according to any one of claims 1 to 5 is formed on the surface of a base material.