KR100320130B1 - Method of forming AlN layer for aluminum parts - Google Patents

Abstract

The present invention relates to a method for forming an aluminum nitride layer of an aluminum component that forms an aluminum nitride layer by activating a nitrogen gas in a plasma state using a plasma nitriding method to cause a contact reaction with an aluminum surface.

Due to the practice of the present invention, it is possible to form a film even in a low-cost aluminum alloy, thereby reducing manufacturing costs, and the aluminum nitride (AlN) film not only has good corrosion resistance, but also has a dense structure and no porosity, thereby preventing corrosion essentially. In addition, the heat transfer coefficient is excellent at about 200-300 W / mk similar to that of aluminum. Therefore, AlN has a high melting point and hardness, and heat conductivity is similar to that of aluminum, so that the heat transfer ability is excellent, thereby increasing heat transfer efficiency as well as increasing durability due to improved corrosion resistance. It also improves performance and saves energy.

Description

Method of forming aluminum nitride layer of aluminum parts {Method of forming AlN layer for aluminum parts}

The present invention relates to a method of forming an aluminum nitride layer on the surface of an aluminum component, and more particularly, to activate a nitrogen gas in a plasma state by using a plasma nitriding method, and then to make a contact reaction with the surface of the aluminum aluminum nitride layer It relates to a method for forming an aluminum nitride layer of an aluminum component for forming a film.

Surface treatment methods for aluminum components include a chemical etching method and a functional coating formation method by plasma spraying.

As a chemical etching method, there is a Nikasil method in which aluminum parts are immersed in an electrolytic bath containing nickel, silicon, and the like, and rigid materials such as nickel and silicon are attached to the surface of the parts. However, when the Nikasil method is used as a cylinder liner of an engine, fuels having a high sulfur content remove the coating and lose the coating function.

In a similar way to Nikasil, there is an Alusil method, in which aluminum parts are made from aluminum alloys with a high silicon content, followed by initial processing and immersing in an acid bath to reveal abrasion resistant silicon. However, the Alusil method is a low-speed, low-pressure process, and is suitable for small aluminum parts, which are not expensive, because the cost of aluminum alloy materials is high, but large parts are expensive and have slow production speed.

Another chemical etching method is a method of preparing and exposing a billet formed by a fine lamination between a fine silicon crystal and a metal on the surface layer of an aluminum alloy containing 25% silicon by spray lamination method, and then spherical silicon particles smaller than 10 μm. There is a hypereutectic Al-Si alloy process that maintains on the liner surface to increase wear resistance and reduce friction. However, this method has to increase the abrasion resistance of the piston when applied to the parts rubbed with the liner, that is, the cylinder liner of the engine, and there is a problem in that the unit cost increases due to the coating treatment.

In the conventional method of forming an aluminum nitride layer using plasma, if the aluminum nitride layer is increased by 10 µm or more due to the high thermal expansion coefficient between the aluminum nitride layer and the base aluminum, defects occur in the nitride layer after the nitriding treatment.

Further, as a technique for forming a protective film on an aluminum component such as an evaporator, there are largely anodizing and painting methods.

The anodizing method is an artificial reinforcement of the natural oxide film (Al ₂ O ₃ ), which always occurs when aluminum comes into contact with oxygen in the air once it comes into contact with air. That is, when sulfuric acid, oxalic acid, and chromic acid are used as electrolytes, aluminum is used as an anode, lead is used as a cathode, and a direct current power source is connected. Then, a thin oxide film begins to form on the surface of aluminum and grows over time. This coating is porous with many fine pores on the surface, and it is possible to secure corrosion resistance only through a process called sealing treatment to fill the porous pores.

Painting is a dipping method that sprays paint on the surface of a product by spraying it or paints it or dips it in the paint.

The oxide film formed on the surface of aluminum by the anodization method is a porous material having many fine pores on the surface, causing corrosion by pitting. Corrosion by fitting is a local corrosion in the form of a small hole on the surface of the material where corrosion is concentrated in this area, so that the corrosion rate is particularly fast and penetrates deep into the metal. Fitting corrosion is not only easy to find because it is the most destructive of all corrosion, but also small in size and easily masked by corrosion products. In addition, since the corrosion proceeds quickly, parts such as an evaporator have a risk of corrosion occurring in a portion in which the refrigerant flows in the evaporator and the refrigerant flows out.

The surface treatment of the aluminum parts by the coating method can prevent corrosion by fittings such as the anodizing method, but the coating formed of the paint has a poor heat transfer efficiency, and in the case of a component such as an evaporator, cooling performance decreases and accordingly There was a problem of increasing consumption.

Accordingly, the present invention has been made to solve the above problems, and an object of the present invention is to uniformly form an aluminum nitride layer by using a plasma generating power source, and to compact and uniform three-dimensional parts having small holes or bent shapes. The present invention provides a method for forming an aluminum nitride layer of an aluminum component that improves corrosion resistance and heat exchange efficiency by forming an aluminum nitride layer of a structure.

1 is a view schematically showing the configuration of an apparatus for performing a method for forming an aluminum nitride layer of an aluminum component according to an embodiment of the present invention;

2 is a flowchart of a method for forming an aluminum nitride layer of an aluminum component according to an embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

1: heater power supply 2: pulse DC supply

3: rotary pump 4: diffusion pump

5 gas supply unit 6 power supply unit

7: sample stand (cathode stand) 8: heater

9 sample support 10 reaction chamber

11 reaction chamber wall 12 switchgear

13: multi connection port

Forming an aluminum nitride layer method of the aluminum component of the present invention in order to attain the object of the aluminum parts to place the sample stage in the reaction chamber by operating the exhaust device 10. As the degree of vacuum inside the reaction chamber ^-5 to ^{10- 6} torr evacuation step, gas injecting gas such as hydrogen and argon through the gas supply device, gas injection step to maintain the vacuum degree at 0.5 to 2 torr, and supplying power to the heater in the reaction chamber to adjust the temperature in the chamber An elevated temperature step of raising the temperature to a process temperature; a pretreatment step of removing an oxide film formed on the aluminum surface by generating an argon plasma by applying a high voltage using the sample stage and the reaction chamber wall as an anode; and injecting nitrogen gas into the reaction chamber. By using a sample table and the reaction chamber wall as an anode, high voltage is applied to generate nitrogen plasma. To form an aluminum nitride layer on the titanium surface was composed characterized in that consists of a nitride layer forming step.

Hereinafter, a method of forming an aluminum nitride layer of an aluminum component according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view schematically showing a configuration of an apparatus for performing a method of forming an aluminum nitride layer of an aluminum component according to an embodiment of the present invention, Figure 2 is a view of the aluminum component according to an embodiment of the present invention It is a flowchart of the method of forming an aluminum nitride layer.

As can be seen in Figures 1 and 2, the aluminum nitride layer forming method of an aluminum component according to an embodiment of the present invention is an exhaust step (S1) for evacuating the inside of the reaction chamber 10, and the gas for pretreatment Gas injection step (S2) for injecting, an elevated temperature step (S3) for raising the temperature inside the reaction chamber (10), a pretreatment step (S4) for pretreating the surface of the aluminum component with argon plasma, and the surface It consists of a nitride layer forming step (S5) to form an aluminum nitride layer.

In the exhausting step S1, the opening and closing device 12 is opened and the aluminum part is supported by the sample support 9 on the sample table 7 in the reaction chamber 10, and then the rotary pump 3 and the diffusion pump ( Step 4) is performed sequentially to minimize the residual amount of oxygen by making the vacuum degree in the reaction chamber about 10 ^-6 torr.

The gas injection step (S2) is a step of injecting gas such as hydrogen and argon through the gas supply part 5 and then maintaining the vacuum degree in the reaction chamber 10 at 0.5 to 2 torr.

The temperature raising step (S3) is a proper process for supplying power from the heater power supply device 1 to the heater 8 installed in the reaction chamber 10 so as to generate a temperature in the reaction chamber 10 so as to generate a plasma reaction. The step of raising the temperature.

In the pretreatment step S4, an oxide film formed on the surface of the aluminum component is removed by generating an argon plasma by applying a high voltage from the power supply device 6 using the sample stage 7 and the reaction chamber wall 11 as anodes. In this case, the reaction chamber wall 11 is grounded and a negative high voltage is applied to the sample stage 7 to generate argon plasma, and the generated argon plasma is formed on the surface of the aluminum component by sputtering. It acts to remove the aluminum oxide (Al ₂ O ₃ ) film.

In order to completely remove foreign substances and the like on the surface of the aluminum component, the aluminum component is first immersed in a solution mixed with NaCl: NaOH: distilled water at a ratio of 1: 5: 50 for 1-3 minutes and etched prior to the evacuation step (S1). After immersing in ethanol and washing with an ultrasonic cleaner for 30 minutes, the etching and drying steps may be performed, and the exhaust step (S1) to pretreatment step (S4) may be repeated.

In the nitride layer forming step S5, power is supplied to the heater 8 in the reaction chamber 10 to raise the temperature in the reaction chamber 10 to 400-500 ° C., and then the gas supply part 5 in the reaction chamber 10. Inject nitrogen gas from the tank and maintain the pressure at 0.5-2.0 torr for 3-5 hours, and use the sample stand (7) and the multi-connection port (13) as anodes. An aluminum nitride layer is formed on the aluminum surface by applying a high voltage from the supply device 6 to generate a nitrogen plasma. Here again, as in the above, the reaction chamber wall 11 is grounded, and a negative high voltage is applied to the sample stage 7 to generate nitrogen plasma. Thus, the nitrogen ions in the plasma state form the element surface. That is, it combines with aluminum and forms an aluminum nitride (AIN) layer by diffusion.

In the case of using the DC power as the power applied from the power supply device 6, since the aluminum nitride formed on the sample surface is an electrical insulator, the current flows from the aluminum nitride to the surface, and the current flows to some extent. After the aluminum nitride is formed, the surface is completely covered with a non-conductor, so that plasma is not generated, so that further nitriding is difficult even if the process time is increased.

Therefore, in order to continuously induce the formation of the aluminum nitride layer, it is necessary to apply self-bias to the aluminum sample by using a bipolar pulsed DC power source or a radio frequency (RF) power source. This self-biasing allows an electric field similar to a DC power source to be maintained and the nitriding reaction can continue on the aluminum surface.

In addition, in order to efficiently generate nitrogen plasma, high-density plasma is generated by using a microwave system, an electron cyclotron resonance (ECR) system, plasma immersion ion implantation (PIII), plasma source ion implantation (PSII), etc. It is possible to effectively increase the thickness of the aluminum nitride layer in time.

In addition, in the case of using an ion beam apparatus capable of directly injecting nitrogen ions into the reaction chamber after generating nitrogen ions without supplying nitrogen gas by the gas supply unit 5, an aluminum nitride layer having an increased thickness may be formed. The time to form can be further shortened.

It is preferable that the thickness of the said aluminum nitride layer is 5-20 micrometers.

In addition, by injecting oxygen gas from the gas supply unit 5 into the reaction chamber 10 after the step of forming the nitride layer (S5), the pressure is maintained at 1-3 torr and treated for 1-3 hours to oxidize the surface of the aluminum nitride. It may further comprise the step of forming an aluminum layer, wherein the thickness of the aluminum oxide layer is preferably 1-5 ㎛, which is a thermal expansion when the thickness increases when forming an aluminum nitride layer on aluminum parts Although defects are caused by the addition of an aluminum oxide film, it is possible to control the thick film and increase the marketability while preventing such a problem.

On the other hand, the power source used to maintain the temperature 400-500 ℃ when forming the aluminum nitride layer is selected from a single pole pulse DC power source, a dipole pulse DC power source, a radio frequency (RF) power source or a combination of two or more. The DC power source is -500 to -600 V, and the radio frequency (RF) power source is 200 to 400 W, and the power source used for forming the aluminum oxide layer is the DC power source -300 to -500 V, radio frequency (RF) power source. It is preferable that the power supply is 200-400 W.

When aluminum parts are used as cylinder liners, the material is cast from Al-Si, Al-Mg, and Al-Mg-Si aluminum die castings. Surface roughness through the processing is characterized in that Rz 1-9 ㎛.

On the other hand, the aluminum component used by this invention can obtain the same effect also if it uses an aluminum alloy component.

As described above, according to the method for forming an aluminum nitride layer of an aluminum component according to an embodiment of the present invention, by forming an aluminum nitride layer on the surface of the aluminum component, a film can be formed on a low-cost aluminum alloy, thereby reducing manufacturing costs. AlN film is not only good at corrosion resistance but also has a dense structure and no porosity, which can fundamentally prevent corrosion.AlN has a heat transfer coefficient of 200-300 W / mk similar to that of aluminum, so AlN has a high melting point and hardness. The thermal conductivity is similar to that of aluminum, so the heat transfer ability is excellent, thereby increasing the durability and improving the energy efficiency by improving heat transfer efficiency.

Claims (10)

The aluminum part was placed on the sample table in the reaction chamber and the exhaust system was operated to increase the vacuum degree in the reaction chamber by 10.^-5To 10^-6an exhaust step of torring, a gas injection step of injecting gas such as hydrogen and argon through a gas supply device, and maintaining a vacuum of 0.5 to 2 torr; A temperature raising step to raise the temperature, a pretreatment step of removing an oxide film formed on the aluminum surface by generating an argon plasma by applying a high voltage using the sample stage and the reaction chamber wall as an anode, and injecting nitrogen gas into the reaction chamber. A method of forming an aluminum nitride layer of an aluminum component, comprising: forming a nitride layer on an aluminum surface by applying a high voltage to the anode and the reaction chamber wall as an anode to generate a nitrogen plasma. The aluminum nitride layer of the aluminum component according to claim 1, further comprising an oxide layer forming step of forming an aluminum oxide layer on the surface of the aluminum nitride by injecting oxygen gas into the reaction chamber after the forming of the nitride layer. Formation method. The method of claim 1, wherein the reaction chamber wall is grounded and the sample stage is applied with a negative high voltage. [Claim 2] The aluminum power source of claim 1, wherein the power source used in the nitride layer forming step is selected from a monopolar pulsed DC power source, a bipolar pulsed DC power source, a radio frequency (RF) power source, or a combination of two or more thereof. Method of forming an aluminum nitride layer of a part. 5. The method of forming an aluminum nitride layer of an aluminum component according to claim 4, wherein the direct current power source -500 to -600 V and the radio frequency (RF) power source are 200 to 400 W. The method of claim 1, wherein the gas supply unit is replaced with an ion beam device. 3. The method for forming an aluminum nitride layer of an aluminum component according to claim 2, wherein a power source used for forming the aluminum oxide layer is a DC power source of -300 to -500 V, and a radio frequency (RF) power source is 200 to 400 W. . The aluminum nitride layer forming method of an aluminum component according to claim 1 or 2, wherein the aluminum nitride layer has a thickness of 5-20 m. The method for forming an aluminum nitride layer of an aluminum component according to claim 2, wherein the aluminum oxide layer has a thickness of 1-5 µm. The method according to claim 1 or 2, wherein when the aluminum component is used as a cylinder liner, the material is cast from Al-Si, Al-Mg, and Al-Mg-Si aluminum die casting. A method of forming an aluminum nitride layer of an aluminum component, characterized by a cylindrical shape of about 2-3 mm and a surface roughness of Rz 1-9 μm through surface processing.