KR100391568B1 - Thermal spraying method for Nitride by mixing oxides as binder - Google Patents

Abstract

The present invention relates to a thermal spray coating method of nitride using an oxide binder,

Claims [1] A method of thermally coating a nitride, comprising: mixing an oxide powder serving as a binder with a nitride powder; Shaping the mixed mixture into a rod shape; By coating the molded ceramic rod using a flame-type flame sprayer, it characterized in that it comprises a step of forming a composite coating layer of nitride-oxide on the surface of the workpiece,

Nitrogen, which is difficult to spray coating alone, is mixed with an oxide binder to form a ceramic rod, and the combustion gas ratio is appropriately controlled by using a brazing flame sprayer. It provides the effect of forming a good coating layer.

Description

Thermal spraying method for Nitride by mixing oxides as binder}

The present invention relates to a thermal spray coating method of nitride using an oxide binder, and more particularly, to a method of thermal spray coating using a flame spraying machine by mixing a nitride with an oxide to form a ceramic rod capable of thermal spray coating. .

Most nitrides such as silicon nitride, boron nitride, sialon and titanium nitride are highly corrosion resistant materials for molten metal. In particular, silicon nitride has excellent toughness among ceramic materials and is promising as a structural material at high temperatures, and has excellent corrosion resistance against highly reactive molten metals such as molten zinc and aluminum, and excellent molten metals do not wet well. Therefore, it is a material having high applicability in the industrial field dealing with molten metal.

Due to these characteristics, there have been many examples of manufacturing parts using nitride sintered bodies in the industry using molten metal. However, in the case of small parts, it is easy to manufacture the parts by a method such as sintering, but there are many technical difficulties in manufacturing a large member such as a roll, and it is difficult to apply practically because of high manufacturing cost.

In order to solve the above difficulty, various other methods of bonding nitride to the raw material have been tried, among which a method of attaching a piece of nitride to a roll (JP 97-346208). However, when using such a method, it is difficult to attach the nitride pieces so that they do not fall well, and there is a problem that a small space is created between the nitride pieces, causing defects on the product surface in contact with the portion.

As another method, in the case where the properties of the nitride are required only for the surface properties of the part, a method of coating with nitride may be used. This coating method has various advantages, but causes the following problems.

That is, when using the method of ion nitride the material itself as a method of forming the nitride, it is difficult to apply to large parts, because the material must be processed in the chamber.

As another method, the thermal spraying method may be used. In the case of coating using the thermal spraying method, even a large part may be easily coated regardless of the shape, and thus, the above problems may be solved. do.

That is, when thermally spraying nitride alone, the nitride is decomposed or oxidized while being exposed to a high temperature flame. In some known techniques (JP 97-25583, JP 95-62516), a technique of coating carbide or nitride alone as an upper coating on a lower coating layer has been filed, but a coating layer having practically practical properties could not be formed.

On the other hand, in order to prevent the decomposition of the nitride in some attempts to the nitride spray coating in the chamber filled with high pressure nitrogen, but did not obtain a healthy coating.

For this reason, a material containing nitride is practically applied on the thermal spray coating layer to form a sealing material (JP 97-235666), and a method of coating using a metal as a binder has been used.

Since the method of thermally spraying nitride alone lacks practicality, it can be said that the above-described method of thermal spraying using a binder is the most practical among the above-mentioned various thermal spraying methods. However, when the metal is used as the binder, since the molten metal preferentially erodes the metal binder, there is a problem in that the characteristics are greatly degraded in terms of corrosion resistance to the molten metal. Therefore, in case of thermal spray coating of nitride by using binder, it is necessary to use a material which is not eroded by molten metal.

The present invention has been made in view of the problems of the conventional thermal spray coating method of nitride as described above, and its object is to provide a molten metal by using an oxide having excellent melting resistance and lower melting point than nitride as a binder. It is to provide a thermal spray coating method that can form a coating layer that the binder is not eroded while utilizing the characteristics of the nitride excellent in corrosion resistance and releasability.

1 is a structural diagram showing the operation principle of the flame-type flame sprayer,

2 is an X-ray diffraction analysis showing the components of the coating layer formed by the embodiment of the present invention, A is the case where the ratio of acetylene: oxygen as a complete combustion condition, B is incomplete combustion conditions the ratio of acetylene: oxygen This is the case.

<Explanation of symbols for the main parts of the drawings>

1: ceramic rod 2: fuel gas, oxygen injection port

3: carrier gas inlet 4: nozzle cap

5: molten ceramic particles

In order to achieve the above object, the present invention provides a method of spray coating a nitride, comprising: mixing an oxide powder serving as a binder with a nitride powder; Molding a ceramic rod into the mixed mixture; The ceramic rod is coated with a flame-type flame sprayer to form a composite coating layer of nitride-oxide on the surface of the workpiece.

In this case, as the oxide powder serving as the binder, one of the oxide powders of aluminum, zirconium, calcium, magnesium, titanium, yttrium, hafnium, silicon, cerium or boron may be used, or two or more thereof may be mixed and used. As the nitride powder, one of silicon nitride, boron nitride, sialon or titanium nitride powder is used, or two or more kinds thereof are used in combination.

In addition, the present invention, during the process of coating the ceramic rod using a flame-type flame sprayer, by controlling the mixing ratio of fuel gas and oxygen to achieve incomplete combustion, while the ceramic rod is melted by using nitrogen as a carrier gas Inhibit the decomposition or oxidation of nitrides.

Hereinafter, the present invention, the thermal spray coating method of the nitride using the oxide binder in detail as follows.

1 is a structural diagram showing the operation principle of the flame-type flame sprayer.

When fuel gas and oxygen are supplied to the inside of the flame sprayer nozzle through the fuel gas and the oxygen injection port 2 and burned, the composite ceramic rod 1 of oxide-nitride melts due to the combustion heat, and the carrier gas injection port 3 The molten ceramic particles 5 are accelerated by the gas supplied through the same, and adhered to the base material to form a coating layer. As the fuel gas, hydrocarbon gases such as acetylene, propane and butane are used.

At this time, since the temperature of the combustion gas can reach 2500-3000 ° C., the ceramic rod 1 can be melted. However, in general, the melting point of nitride is higher than the melting point of oxides such as aluminum, zirconium, calcium, and magnesium, which are commonly used at about 2500 to 3000 ° C. Therefore, the ceramic rod 1 can be melted if it reaches only the melting point of the oxide before it is heated to the melting point of the nitride, so that the ceramic rod 1 can be separated from the ceramic rod 1 to form a coating layer.

However, it is advantageous for the oxide to have a low melting point because nitride can decompose or oxidize after long exposure to high temperatures. By doing so, the oxide is melted and released from the ceramic rod 1 before the nitride is decomposed and oxidized, whereby a composite coating layer of nitride-oxide can be obtained.

In order to lower the melting point of the oxide, the melting point can be lowered by mixing or alloying two types of oxides. For example, the melting point of aluminum oxide is about 2000 ° C, but when the titanium oxide is mixed, the melting point is about 1700 ° C, the boron oxide is mixed, 1035 ° C, and the calcium oxide is mixed, about 1360 ° C. In addition, when the three species of oxides are mixed at an appropriate ratio, the melting point of the oxides is further lowered, so that it is easier to spray the nitrides.

When selecting an oxide, it is preferable to select the kind which is not eroded by the molten metal used. In general, oxides such as aluminum, zirconium, calcium, magnesium, titanium, yttrium, hafnium, silicon, and cerium do not react with highly reactive molten metals such as zinc or aluminum, so it is more desirable to choose this kind of oxide. Do.

Meanwhile, in the air atmosphere, boron nitride decomposes or oxidizes severely from about 1000 ° C. and silicon nitride from about 1200 ° C. However, reducing the amount of oxygen in the atmosphere can inhibit decomposition or oxidation reactions at higher temperatures.

Since the ceramic rod is melted by the heat generated during combustion of the hydrocarbon gas, the ceramic rod is exposed to the combustion gas atmosphere. At the same time, the carrier gas injected through the carrier gas injection port is also mixed with the combustion gas, so that an atmosphere of the combustion gas-carrier gas is substantially formed inside the nozzle of the thermal sprayer.

However, compressed air is generally used as a carrier gas, and since a large amount of oxygen is contained in the air to oxidize and decompose nitride, it is preferable to use nitrogen as a carrier gas to suppress such a reaction.

In addition, in the condition for combusting a hydrocarbon gas, the ratio (year consumption) fully opened, the smaller than the consumption during the combustion gas oxidizing gas of H ₂ O, CO ₂ in addition to H _2, the reducing gas CO in oxygen to form much of the hydrocarbon Therefore, decomposition and oxidation of the nitride can be prevented.

At this time, while the molten fugitive particles fly to the coating object, the air is mixed with the combustion gas and the carrier gas to increase the oxygen partial pressure, but since the particle flight speed is about 100 to 200m per second, the reaction time with oxygen is extremely short, It can form a coating layer in the form.

In this way, a ceramic rod is prepared by mixing one or two or more oxides and one or two or more nitrides, and then using a flame-type flame sprayer using the same as nitrogen, nitrogen is used as a carrier gas, and hydrocarbons are used. By spraying the gas and oxygen in an appropriately controlled ratio, a good composite coating layer of oxide and nitride can be obtained.

Hereinafter, the present invention will be described in detail through examples.

EXAMPLE

Aluminum oxide and silicon nitride were adjusted in a ratio of 1: 1 to molar ratio, and uniformly mixed. A small amount of paraffin-based organic binder was mixed with a mixture of nitride and oxide, extruded into a rod form, dried, and then sintered at a temperature of 1200 ° C. for 30 minutes in an atmosphere maintained in a nitrogen atmosphere to have a diameter of 6 mm. Phosphorous ceramic rods were prepared.

As a thermal spraying machine, a Rokide ^™ gun, which is a type of hot flame spraying machine, was used. Acetylene gas was used as the fuel gas, and the amount of oxygen was adjusted to be 1: 2.5, which is a complete combustion ratio, and 1: 1.9, which is an incomplete combustion ratio. Nitrogen gas was used as a carrier gas instead of compressed air.

2 is an X-ray diffraction analysis showing the components of the coating layer formed by the embodiment of the present invention, A is the case where the ratio of acetylene: oxygen as a complete combustion condition, B is incomplete combustion conditions the ratio of acetylene: oxygen This is the case.

In the case of A, silicon oxide was formed in addition to aluminum oxide and silicon nitride as raw materials. Silicon oxide is formed by the oxidation of silicon nitride during the thermal spraying process. In the case of B, it can be seen that the oxidation reaction is suppressed so that almost no silicon oxide is formed and the silicon nitride completely forms the coating layer.

As described above, according to the present invention, a ceramic rod is formed by mixing nitrides, which are difficult to spray coating alone, with an oxide. By coating, the composite coating layer of nitride and oxide can be formed favorably.

In addition, in the present invention, since the oxide is used as the binder material, peeling of the coating layer due to erosion of the binder metal can be prevented as in the case of using a metal.

Therefore, when the present invention is applied to parts such as dies, taps, molds, etc., in which molten metals are in contact with molten metal plating facilities and molten metals such as molten zinc and molten aluminum, these molten metals come into contact with each other. It is much cheaper than that to obtain the effect of improving the life of the parts, as well as the releasability is excellent, it is also possible to improve the work efficiency.

Claims (4)

Claims [1] A method of thermally coating a nitride, comprising: mixing an oxide powder serving as a binder with a nitride powder; Shaping the mixed mixture into a rod shape; Coating the molded ceramic rod with a flame-type flame sprayer to form a composite coating layer of nitride-oxide on the surface of the workpiece, wherein the thermal spray coating method of the nitride using an oxide binder. The oxide powder according to claim 1, wherein one of the oxide powders of aluminum, zirconium, calcium, magnesium, titanium, yttrium, hafnium, silicon, cerium or boron is used, or two or more thereof are used in combination. And, as the nitride powder, one kind of silicon nitride, boron nitride, sialon, or titanium nitride powder is used, or two or more kinds thereof are mixed and used. The method of claim 1 or 2, wherein during the process of coating the ceramic rod using a sealed flame sprayer, incomplete combustion is achieved by adjusting the mixing ratio of fuel gas and oxygen, thereby reducing the amount of nitride during melting of the ceramic rod. A thermal spray coating method of nitride using an oxide binder, characterized in that the decomposition or oxidation reaction is suppressed. The thermal spraying of nitride using an oxide binder according to claim 1 or 2, wherein during the coating process using the sealing flame sprayer, nitrogen is used as a carrier gas to suppress decomposition or oxidation of the nitride. Coating method.