METHOD OF MANUFACTURING HIGH-DENSITY YF3 COATING LAYER BY USING HVOF, AND HIGH-DENSITY YF3 COATING LAYER MANUFACTURED THROUGH SAME

Abstract

The proposed is a manufacturing method for a high-density YF.sub.3 coating layer by high-velocity oxygen fuel spraying (HVOF). More particularly, proposed is a manufacturing method for a high-density YF.sub.3 coating layer by HVOF, in which YF.sub.3 powder is melted and quenched to form densified spherical YF.sub.3 particles and then the YF.sub.3 particles are applied by HVOF to form a high-density YF.sub.3 coating layer with improved mechanical properties and plasma resistance.

Claims

1. A manufacturing method for a high-density YF.sub.3 coating layer by high velocity oxygen fuel spraying (HVOF), the method comprising the steps of: (a) feeding YF.sub.3 powder into a plasma jet and melting the YF.sub.3 powder; (b) preparing spherical YF.sub.3 particles by spraying molten YF.sub.3 droplets to a refrigerant; (c) removing the refrigerant after step (b) and drying the spherical YF.sub.3 particles; and (d) applying YF.sub.3 powder particles formed in step (c) to a substrate by HVOF, wherein in step (b), a distance from a spray outlet to a surface of the refrigerant is 400 to 600 mm when the molten YF.sub.3 droplets are sprayed.

2. The method of claim 1, wherein the refrigerant is any one or more selected from H.sub.2O, N.sub.2, and Ar.

3. The method of claim 1, wherein a particle size of the spherical YF.sub.3 particles in step (d) is 10 to 60 μm.

4. The method of claim 1, wherein the HVOF in step (d) is performed under conditions of an oxygen gas flow rate of 1900 to 2500 SCFH and a fuel rate of 4 to 6 GPH.

5. A high-density YF.sub.3 coating layer manufactured by the method of claim 1.

6. The YF.sub.3 coating layer of claim 5, wherein the high-density YF.sub.3 coating layer is composed of Y, O, and F, contains O in an amount of 6 to 8 at %, and contains F in an amount of 61 to 65 at %.

7. The YF.sub.3 coating layer of claim 5, wherein the high-density YF.sub.3 coating layer has a porosity of less than 1% and a hardness of 400 to 500 Hv.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and other objectives, features, and other advantages of the present invention will be more clearly understood from the following detailed description when taken in conjunction with the accompanying drawings, in which:

[0027] FIG. 1 a schematic diagram illustrating a preparation method for a spherical YF.sub.3 powder according to an embodiment of the present invention;

[0028] FIG. 2 is a flowchart illustrating a manufacturing method for a high-density YF.sub.3 coating layer by HVOF according to the present invention;

[0029] FIG. 3 illustrates SEM images of YF.sub.3 powder particles before/after spheroidizing according to an embodiment of the present invention; and

[0030] FIG. 4 illustrates SEM images of each coating layer formed from a spheroidized or non-spheroidized YF.sub.3 powder by different plasma spray coating methods according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0031] Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Generally, the nomenclature used herein and the laboratory procedures described below are those well known and commonly employed in the art.

[0032] It will be further understood that the terms “comprise”, “include”, and/or “have”, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

[0033] In one aspect, the present invention provides a manufacturing method for a high-density YF.sub.3 coating layer by HVOF, the method comprising the steps of: (a) feeding YF.sub.3 powder into a plasma jet and melting the YF.sub.3 powder; (b) preparing spherical YF.sub.3 particles by spraying molten YF.sub.3 droplets to a refrigerant; (c) removing the refrigerant after step (b) and drying the spherical YF.sub.3 particles; and (d) applying YF.sub.3 powder particles formed in step (c) to a substrate by high-velocity oxygen fuel spraying (HVOF).

[0034] FIG. 1 a schematic diagram illustrating a preparation method for a spherical YF.sub.3 powder according to an embodiment of the present invention. FIG. 2 is a flowchart illustrating the manufacturing method for the high-density YF.sub.3 coating layer by HVOF according to the present invention. Referring to these drawings, a description will be given in detail below.

[0035] In the present invention, step (a) is a step of feeding the YF.sub.3 powder into the plasma jet and melting the YF.sub.3 powder.

[0036] Plasma refers to a state in which a gas is heated by extremely high-temperature energy and separated into charged electrons and ions, and a plasma jet refers to a plasma in the form of a spray. In step (a) of the present invention, the YF.sub.3 powder is fed into the plasma jet to melt the YF.sub.3 powder within a short period of time.

[0037] At this time, the temperature of the plasma jet is high enough to melt the YF.sub.3 powder, and may be adjusted in consideration of the melting point of the YF.sub.3 powder.

[0038] Then, step (b) is a step of preparing the spherical YF.sub.3 particles by spraying the molten YF.sub.3 droplets to the refrigerant. When the molten YF.sub.3 droplets are sprayed to the refrigerant, the distance from a spray outlet for the YF.sub.3 droplets to the surface of the refrigerant is set to 400 to 600 mm.

[0039] Specifically, the distance means the distance from the spray outlet of a plasma spray gun to the surface of the refrigerant, and is set to 400 to 600 mm to ensure that the molten YF.sub.3 droplets are sprayed to the refrigerant without loss to improve the yield and exhibit a quenching effect. When the distance is less than 400 mm, the loss of solvent and powder due to spraying pressure is significant, and on the other hand, when it exceeds 600 mm, the yield is reduced due to spraying angle and it is difficult to achieve a sufficient quenching effect of molten powder. Preferably, the distance is 400 to 500 mm.

[0040] In addition, the refrigerant quenches the sprayed molten YF.sub.3 droplets to make them spherical and dense. Specifically, during the process of quenching the molten YF.sub.3 droplets rapidly sprayed to the refrigerant, the YF.sub.3 droplets become spherical to minimize surface energy and are densified at the same time, thereby improving hardness. At this time, the refrigerant may be any one or more selected from H.sub.2O, N.sub.2, and Ar, and in general, the refrigerant is distilled water at room temperature.

[0041] Then, step (c) is a step of removing the refrigerant after step (b) and drying the spherical YF.sub.3 particles. The refrigerant removal and drying of the spherical YF.sub.3 powder may be performed by a conventional method, so detailed descriptions thereof will be omitted. At this time, the drying time or drying temperature is not limited because it may vary depending on the evaporation temperature according to the type of refrigerant. For example, when the refrigerant is distilled water, the drying may be performed at a temperature of 100° C. to 120° C. for at least 15 hours.

[0042] The YF.sub.3 powder particles formed in step (c) has a particle size of 10 to 60 μm. In general, the smaller the particle size of the YF.sub.3 powder particles, the denser a coating layer can be formed. However, when the particle size is less than 10 μm, cohesive force is generated due to a close inter-particle distance, making it technically difficult to feed the powder. On the other hand, and it exceeds 60 μm, the coating layer cannot be formed at high density. Therefore, the particle size of the YF.sub.3 powder particles is 10 to 60 μm, preferably 24 to 45 μm.

[0043] Steps (a) to (c) are a process of spheroidizing and densifying the YF.sub.3 powder, that is, powder particles including the F component. In order to secure corrosion resistance against HF that may be generated in a series of processes, in all or some processes, a container to be used is coated with a Teflon coating of equal to or greater than 50 μm or is made of a ceramic material.

[0044] Finally, step (d) is a step of applying the YF.sub.3 powder particles formed in step (c) to the substrate by high-velocity oxygen fuel spraying (HVOF).

[0045] HVOF is a thermal spray technology whereby powder or precursor is converted into molten droplets using a high-temperature heat source, and then and then the droplets are quenched and solidified by colliding with a substrate at high speed to form a laminated film. It is a method that requires a high density of powder or precursor to form a coating layer. Specifically, a film is formed by burning fuel gas (propane, methylacetylene, heptane, and hydrogen) together with oxygen at high pressure to generate a high-speed jet of 2000 m/s, which is used as a heat source. As a result, it is possible to manufacture a dense coating layer that exhibits excellent bonding strength and improved fatigue properties and thermal shock resistance.

[0046] Furthermore, since the YF.sub.3 powder particles are applied by such HVOF in step (d), it is possible to solve the problem in which when forming a conventional F-based coating layer, the content of F is reduced as the degree of oxidation is increased due to a high-temperature plasma atmosphere. In other words, when the YF.sub.3 powder particles are applied by HVOF in step (d), the degree of oxidation is reduced during coating because a relatively low heat source is used compared to a conventional plasma spraying method. Thus, it is possible to increase the F content and control the element composition ratio. In addition, in the case of HVOF, the size of scattered splats formed as a result of collision of the droplets accelerated at a very high speed is reduced, leading to a reduction in the size of generated particles. This is advantageous in terms of improving the mechanical properties of the coating layer compared to the conventional plasma spraying method.

[0047] In order to generate a high-temperature/high-pressure flame by burning fuel and oxygen, HVOF may be performed under the following conditions. That is, the oxygen gas flow rate may be 1800 to 2000 SCFH, the fuel rate may be 4 to 6 GPH, and the fuel may be kerosene, propane, propylene, acetylene, hydrogen, or the like. The high-density YF.sub.3 coating layer manufactured by the above method has a porosity of less than 1%. Due to its high density, the hardness of the coating layer is significantly increased to 400 to 500 Hv. Also, the coating layer has a high content of F because it is manufactured by HVOF using a relatively low-temperature heat source and thus the degree of oxidation is reduced during coating.

[0048] In other words, the high-density YF.sub.3 coating layer may include F in an amount of 61 to 65 at % and O in an amount of 6 to 8 at %.

[0049] Consequently, the high-density YF.sub.3 coating layer manufactured by the above method has improved mechanical strength, improved ion bombardment resistance during dry etching, and significantly improved plasma resistance.

[0050] Hereinafter, the present invention will be described in more detail by way of Examples, but the present invention is not limited by these Examples.

EXAMPLE

1. Preparation Example

(1) Spheroidizing of YF.SUB.3 .Powder

Preparation Examples 1 to 7: Spheroidizing of YF.SUB.3 .Powder

[0051] A commercially available YF.sub.3 powder was subjected to spheroidizing according to the schematic diagram illustrated in FIG. 1 and the flowchart illustrated in FIG. 2.

[0052] Referring to FIGS. 1 and 2, a plasma was generated in a plasma device first, and then the YF.sub.3 powder was fed into a plasma jet and heated uniformly. At this time, the spraying conditions such as the plasma formation condition, the type of fuel gas, and the like were as illustrated in Table 1 below.

[0053] Then, the heated YF.sub.3 powder was sprayed in the form of molten droplets onto the surface of a refrigerant (water) spaced a distance of 200 to 800 mm apart from a spray outlet to quench the YF.sub.3 droplets, after which the YF.sub.3 was separated from water and dried. A densified spherical YF.sub.3 powder was obtained through the above process. Each spherical YF.sub.3 powder of Preparation Examples 1 to 7 was prepared according to the distance.

TABLE-US-00001 TABLE 1 Voltage (V) Current (A) Power (kW) Ar(NLPM) H.sub.2 (NLPM) 75~78 600~610 44~48 40~44 9~13

Control 1

[0054] A commercially available YF.sub.3 powder not subjected to spheroidizing was used as Control 1.

[0055] Table 2 below illustrates the yield of each spheroidized YF.sub.3 powder of Preparation Examples 1 to 7 prepared according to the distance from the spray outlet to the refrigerant.

TABLE-US-00002 TABLE 2 Distance (mm) Yield (%) Preparation 200 Not measurable Example 1 Preparation 300 70 Example 2 Preparation 400 84 Example 3 Preparation 500 90 Example 4 Preparation 600 87 Example 5 Preparation 700 80 Example 6 Preparation 800 75 Example 7

2. Analysis of Sphericity and Density of Spheroidized YF.SUB.3 .Powder

(1) Yield According to Distance

[0056] Table 2 above illustrates the yield of each spheroidized YF.sub.3 powder of Preparation Examples 1 to 7 prepared according to the distance from the spray outlet for spraying YF.sub.3 droplets to the refrigerant. As can be seen from Table 1, when the distance is 400 to 600 mm, YF.sub.3 can be densified through spheroidizing.

(2) SEM Image

[0057] FIG. 3 illustrates SEM images of the YF.sub.3 powder before spheroidizing (Control 1) and the YF.sub.3 powder after spheroidizing (Preparation Example 4). As can be seen from FIG. 3, the YF.sub.3 powder becomes spherical in shape and densified through spheroidizing.

[0058] In other words, the YF.sub.3 powder (Control 1) before spheroidizing had a non-spherical shape and had a D50 of 34.6 μm, whereas the YF.sub.3 powder (Preparation Example 4) after spheroidizing had a spherical shape and was densified to have a D50 of 26.4 μm.

3. Formation of YF.SUB.3 .Coating Layer

Example 1: Formation of YF.SUB.3 .Coating Layer Using HVOF Device

[0059] The prepared spherical YF.sub.3 powder (Preparation Example 4) was applied using an HVOF device (Praxair, JP5220). At this time, a high-speed flame was generated under the conditions of oxygen 2,000 SCFH (standard cubic feet of gas per hour) and kerosene 6 GPH (gallon per hour).

[0060] Comparative Example 1: Formation of non-spheroidized YF.sub.3 coating layer using atmospheric plasma spraying (APS) device

[0061] The non-spheroidized YF.sub.3 powder of Control 1 was applied using an APS device (OerlikonMetco, F4MB). At this time, a plasma was generated under the conditions of a voltage of 80.0 V, a current of 600 A, and a gas supply of argon gas 40 NLPM and hydrogen gas 8 NLPM. Comparative Example 2: Formation of non-spheroidized YF.sub.3 coating layer using suspension plasma spraying (SPS) device

[0062] The non-spheroidized YF.sub.3 powder of Control 1 was applied using an SPS device (Progressive, 100HE). At this time, a plasma was generated under the conditions of a voltage of 285.0 V, a current of 380 A, and a gas supply of argon gas 340 SCFH, nitrogen gas 100 SCFH, and hydrogen gas 80 SCFH.

4. Coating Layer Analysis According to Plasma Spray Coating Method

(1) Physical Properties

[0063] Table 3 below and FIG. 4 illustrate a comparison of the physical properties (hardness, porosity, and surface roughness), and coating state of each coating layer formed from the spherical or non-spherical spherical YF.sub.3 powder by different plasma spray coating methods.

TABLE-US-00003 TABLE 3 Comparative Comparative Example 1 Example 1 Example 2 Item (HVOF coating) (APS coating) (SPS coating) Hardness (Hv) <500 <300 <500 Porosity (%) <1% <3% <1% Surface 2~3 3~4 1~2 roughness (μm)

[0064] As can be seen from Table 3 and FIG. 4, in the case of Example 1 formed by HVOF coating using the spherical YF.sub.3 powder, the porosity and surface roughness are reduced, the hardness is significantly increased, and the density is increased compared to Comparative Example 1 formed by APS coating using the non-spherical YF.sub.3 powder. This result was due to the fact that the YF.sub.3 powder was highly densified through spheroidizing. Furthermore, the high densification of YF.sub.3 through spheroidizing made it possible to use the HVOF coating method.

[0065] Meanwhile, in the case of Example 1 formed by HVOF coating using the spherical YF.sub.3 powder, similar physical properties are exhibited and the density is increased compared to Comparative Example 2 formed by SPS coating using the non-spherical YF.sub.3 powder.

(1) XPS

[0066] Table 4 below illustrates XPS analysis results of each coating layer formed from the spheroidized or non-spheroidized YF.sub.3 powder by different plasma spray coating methods.

TABLE-US-00004 TABLE 4 Component ratio Compound Unit O F Y Example 1 (HVOF) YF.sub.3 at. % 7.1 63.4 29.5 Comparative 6.5 62.2 31.3 Example 1 (APS) Comparative 11.2 59.4 29.4 Example 2 (SPS)

[0067] As can be seen from Table 4 above, in the case of Example 1 formed by HVOF coating using the spheroidized YF.sub.3 powder, the O content is low while the F content is high compared to Comparative Example 2 formed by SPS coating using the non-spheroidized YF.sub.3 powder. This is because, since HVOF coating uses a relatively low-temperature heat source compared to SPS coating, the degree of oxidation is low, which is advantageous for the formation of F-based coating layers.

[0068] Meanwhile, in the case of Example 1 formed by HVOF coating using the spheroidized YF.sub.3 powder, the F content is similar compared to Comparative Example 1 formed by APS coating using the non-spheroidized YF.sub.3 powder.

[0069] From the analysis results, it is revealed that in the case of HVOF coating using the spheroidized YF.sub.3 powder, the physical properties are significantly improved compared to APS coating using the non-spheroidized YF.sub.3 powder, and a coating layer having a low O content and a high F content can be formed compared to SPS coating using the spheroidized YF.sub.3 powder.

[0070] Thus, when the spheroidized YF.sub.3 powder is applied by HVOF, a coating layer having a high F content while having high mechanical properties can be formed.

[0071] Although referred embodiments of the present invention have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions, and substitutions are possible, without departing from the scope and spirit of the present disclosure as disclosed in the accompanying claims.