JP2640234B2 - Oxide spray material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an oxide spray material using an oxide as a raw material.

[Conventional technology]

As a method for improving the heat resistance, corrosion resistance, and wear resistance of a material, a method of spraying a material having excellent performance on the surface of the material is known. In particular, heat transfer tubes, burner impellers and gas turbine parts for coal-fired boilers
Since it is used at a high temperature of 0 ° C. and further causes corrosion and abrasion, oxide powders, which are high melting point materials such as alumina and zirconia, are widely used as thermal spraying materials. On the other hand, as a means for spraying these oxide powders, a plasma spraying method using a thermal plasma arc or a high energy gas spraying method using gas combustion or explosion energy is used. In order to obtain a strong coating by these spraying methods, it is necessary to adhere the sprayed powder to the material surface in a molten state. However, since the oxide-based material has a high melting point of 2000 ° C. or higher, it is difficult to spray this material by the above-mentioned thermal spraying method, particularly, the high energy gas thermal spraying method. That is, in the high-energy gas spraying method, the gas temperature is relatively low at about 3000 ° C. at the maximum, and the gas flow rate is as high as Mach 2; It is difficult for the entire system powder to melt before reaching the surface of the material to be sprayed. for that reason,
Some of the powder adheres to the surface of the material to be sprayed without melting. As a result, the bond strength between the oxide particles in the sprayed coating becomes weaker, many pores are generated in the coating, and the adhesion to the surface of the material to be sprayed is reduced, resulting in a defect that a strong coating cannot be obtained. there were.

As a method of improving this, there is a method of reducing oxide particles to submicron or less.

[Problems to be solved by the invention]

When the powder of the submicron particles is used as a thermal spray material, the meltability is improved, but the fluidity of the powder during transportation is extremely deteriorated. The reason for the poor fluidity is that the finer the particles, the easier it is for the particles to agglomerate, especially when the humidity is high. As a result, the powder easily adheres to the inside of the powder transport tube, so that stable powder supply cannot be performed or clogging may occur. In addition, since the fine particles are small in weight and easily scattered inside the spray gun, there is a problem that the fine particles may adhere to the inside of the spray gun and agglomerate, mix with the unmelted state in the coating, and become a defect. .

An object of the present invention is to solve the above problems and to provide an oxide spray material capable of obtaining a dense and strong spray coating.

[Means for solving the problem]

An object of the present invention is to provide an oxide spray material characterized in that powder particles are formed by bonding oxide particles having an average particle diameter of 1 μm or less to form powder particles, and the inside of the powder particles is hollow. This is achieved by:

[Action]

The powder particles of the thermal spray material are large-diameter spherical particles having a surface layer formed by bonding a large number of oxide fine particles having an average particle diameter of 1 μm or less to form a surface layer. The heat is sufficiently transferred and the powder particles melt easily. Further, the hollow spherical powder particles are melted while being dispersed until they reach the surface of the material to be sprayed, and collide with the surface of the material to be sprayed, so that the molten oxide fine particles are sufficiently pressed against the surface.

If the average particle diameter of the oxide fine particles exceeds 1 μm, it is not preferable because the spraying heat cannot be sufficiently transmitted into the fine particles and adheres to the surface to be sprayed without being sufficiently melted, thereby making it difficult to perform pressure bonding.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is an explanatory view showing the structure of powder particles as an oxide spray material according to the present invention. One powder particle is composed of a plurality of oxide fine particles 1, and the inside of the powder particle is a cavity 2.

FIG. 2 shows an example of the procedure for producing the present powder particles. This production method is one of the established methods of forming a fine hollow sphere, in which the surface of a spherical mother particle 3 having a particle diameter of several tens of μm is applied to the surface.
The oxide fine particles 1 having a thickness of not more than μm have an average thickness of several μm to 10 μm.
Then, the base particles 3 are removed by a method such as heat treatment or dissolution. The average thickness of the particles is approximately 1
The average thickness is preferably in the range of 20 to 20 μm, preferably 5 to 10 μm. If the average adhesion thickness is too small, the powder tends to break during transportation, and if it is too large, melting by spraying heat is not sufficient.

At this time, as a material of the base particles 3, carbon which is burned at a relatively low temperature to become carbon dioxide gas, or an organic powder which is easily dissolved in an organic solvent such as ketone, acetone and ether is preferable. The particle diameter of the base particles is 200 μm or less, preferably several tens μm to 2 μm in consideration of fluidity and meltability.
The thickness is preferably about 00 μm.

When the particle size of the base particles exceeds 200 μm, the powder particles are easily crushed, so it is necessary to thicken the fine particle layer adhered to the base particles, so that it is difficult for heat to completely transfer inside the powder particles during thermal spraying. The powder particles are not sufficiently melted and adhere to the material to be sprayed to form a sprayed coating having low strength. On the other hand, as the particle size of the base particles becomes smaller, granulation becomes more difficult, and the fluidity during powder transportation gradually decreases. However, when the particle size of the base particles is several tens μm or more, sufficiently good results were obtained.

As a method for forming the powder particles, when the base particles 3 are carbon, the oxide fine particles are attached to the surface of the carbon with a binder containing carbon, and then heated at a temperature not lower than the temperature at which the carbon is burned (around 1000 ° C.). At this time, the carbon of the base particles is burned to form carbon dioxide gas, and powder particles having an outer layer of oxide fine particles and a hollow inside can be formed.

On the other hand, when the base particles are organic powder, the powder particles of the present invention are obtained by attaching oxide fine particles to the surface of the organic powder with an organic binder and then immersing the particles in a solvent in which the organic powder is easily dissolved. Can be produced. At this time, by heating the obtained powder at a temperature of 800 ° C. to 1000 ° C., the powder is sintered, the bonding force between the fine particles is increased, and the strength of the powder particles can be improved. Regarding the strength of the powder particles, a certain degree of strength is required to prevent the powder particles from being broken during transportation in the pipe.

 Hereinafter, the embodiment of the present invention will be described in detail.

The oxide of fine particles having an average particle diameter of 1 μm or less is converted to zirconia +
Sprayed powder with 8% yttria and hollow inside was prepared by the above method using carbon as the base particle, and 0.3 mm thick on the steel sheet surface by the explosive spraying method, which is a kind of high energy gas spraying method. Sprayed. The thermal spraying conditions are as follows.

Oxygen flow rate: 70 / min Acetylene flow rate: 40 / min Powder supply rate: 10 mg / sec Next, the resulting sprayed coating was measured for micro Vickers hardness (load: 300 g) and the porosity of the cross section. As comparative materials, commercially available stabilized zirconia powder (particle size: 10 to 40 μm), stabilized zirconia powder (particle size: 10 to 40 μm) described in Japanese Patent Application No. 62-73532, and alumina powder (particle size: 10 to 40 μm) were used. 4040 μm) was mixed at a ratio of 96: 4, and a similar sample was prepared using the granulated powder, and the same measurement was performed. Table 1 shows the results.

As is clear from these results, the thermal spray coating using the oxide-based powder material according to the present invention can provide a strong coating excellent in the hardness and porosity of the thermal spray coating cross section as compared with the case where the conventional thermal spray powder is used. You can see that.

FIG. 3 shows an enlarged view of the thermal spray coating obtained in this example. As shown in FIG. 3 (a), the thermal spray coating of the oxide thermal spray material of the present invention is such that the pores 4 formed between the fine oxide particles 5 are fine and uniformly distributed in the coating. On the other hand, as shown in FIG. 3 (b), the thermal spray coating made of a commercially available stabilized zirconia powder, which is a conventional thermal spray material shown in the comparative example, has large pores 4 between oxide particles 5 having a large particle size. Intervening.

As shown in the above examples, the reason why a film sprayed using the oxide spray material according to the present invention exhibits excellent characteristics is as follows.

When this powder is sprayed by the explosive spraying method, the heat of the spraying is sufficiently transmitted to the high melting point oxide fine particles forming the surface layer of the powder particles, so that the powder particles are easily melted even at a relatively low temperature, The powder particles are sufficiently melted and dispersed until reaching the surface of the material to be sprayed and collide with the surface of the material to be sprayed. For this reason, the pores formed between the individual oxide particles in the thermal spray coating are fine and uniformly distributed in the coating, resulting in a dense coating.

〔The invention's effect〕

According to the configuration of the present invention, the powder particles of the oxide-based thermal spray material have a surface layer portion composed of high-melting oxide fine particles and a cavity formed therein. Since the particles are well melted, the fine particles are well bonded to each other, and are well pressed against the surface of the material to be sprayed, a very dense and strong thermal spray coating with few pores can be formed.

In addition, the powder of the oxide-based thermal spray material of the present invention has excellent fluidity due to spherical particles having a large outer diameter, does not cause clogging in the powder transport tube, and also adheres and agglomerates inside the thermal spray gun. Therefore, there is no possibility that the deposits inside the spray gun are mixed into the coating film unmelted and become a defect.

Therefore, since the thermal spray coating is a dense coating formed of an oxide thermal spray material, a strong thermal spray coating with excellent corrosion resistance can be obtained. By applying this coating to the product, the heat resistance, abrasion resistance, and corrosion resistance of the product can be obtained. Can be significantly improved, which greatly contributes to extending the life of the product.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the structure of powder particles of the oxide-based thermal spray material according to the present invention, and FIG. 2 is a cross-sectional view for explaining a method for producing powder of the oxide-based thermal spray material according to the present invention. FIG. 3 (a) is an explanatory view showing the porosity of the cross section of the thermal spray coating made of the oxide thermal spray material according to the present invention, and FIG. 3 (b) is the cross section of the thermal spray coating of the comparative thermal spray material. FIG. 4 is an explanatory diagram showing a state of pore generation. 1 ... fine particles, 2 ... cavities.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-262453 (JP, A) JP-A-58-151474 (JP, A) JP-A-57-210969 (JP, A) 150178 (JP, A) JP-A-56-33469 (JP, A) Metal, 57 [4] (Showa 62-4-1); 54-57 Adu, Therm Spraying (1986); 241-249, M.P. R. Dorfman and J.M. D. Realdon, "Spherical Ceramic Powers for Thermal Spraying"

Claims (3)

(57) [Claims] 1. An oxide-based thermal spray material characterized in that oxide particles having an average particle diameter of 1 μm or less are combined to form powder particles, and the inside of the powder particles is hollow. 2. The oxide spray material according to claim 1, wherein said oxide comprises at least one of zirconia, alumina, titania, yttria, magnesia, calcia, and chromia. 3. The method according to claim 1, wherein the diameter of the cavity of the powder particles is 200 μm or less.
Item 2. The oxide spray material according to item 1.