KR100346019B1 - Method and Apparatus for Coating Inner Surface of Tubes or Cylinders Using Laser Ablation - Google Patents

Abstract

The present invention relates to a method and apparatus for uniformly longitudinally coating the inner wall of a tube or cylinder with a carbide and nitride thin film or an amorphous diamond-like carbon thin film of Cr or Ti using laser ablation. According to the method of the present invention, a very dense thin film having enhanced corrosion resistance, abrasion resistance, and abrasion resistance can be coated on the inner wall of the tube or cylinder.

Description

Method and device for coating inner wall of tube or cylinder using laser ablation {Method and Apparatus for Coating Inner Surface of Tubes or Cylinders Using Laser Ablation}

The present invention relates to a method for coating inner walls of tubes and cylinders using laser ablation and a laser ablation coating apparatus used therein. More specifically, the present invention relates to corrosion resistance to inner walls of tubes and cylinders. The present invention relates to a method of uniformly coating a carbide or nitride thin film of Cr or Ti or an amorphous diamond-like carbon thin film in the longitudinal direction by using laser ablation to enhance wear resistance and abrasion resistance.

Tubes and cylinders are very widely used, from water pipes in everyday life to piping in chemical plants or piping in nuclear power plants. Iron, non-ferrous, polymer and composite materials are used as the material of these piping materials, but iron-based pipes are widely used in terms of mechanical properties and cost. Such pipe materials are required to have chemical resistance, corrosion resistance and wear resistance according to the intended use. In particular, the inner layer of the piping of a chemical plant or the piping of a nuclear power plant should have very excellent physical properties.

As a method for improving properties for imparting chemical resistance, corrosion resistance, and abrasion resistance to an inner surface layer of such a pipe material, a method of coating a thin film of excellent physical properties such as Cr and the like by a wet method has been used.

The surface oxidation method is a method of exposing the iron-based surface to an oxidizing atmosphere to produce a dense iron-based oxide to form an oxide layer of corrosion resistance and hardness, and is not a method of coating a new material. This method has the advantage that the process is relatively simple, but the layer of the material formed on the surface is limited to the oxide of the base material, there is a disadvantage that the lubricating properties and impact resistance of the oxide layer is bad.

The wet coating method has the advantage of being able to form a uniform coating in the longitudinal direction of the tube or cylinder.However, in order to coat a dense thin film of high hardness, ion coating must be involved in forming the coating layer. It is impossible to synthesize dense thin films of high hardness (Hv 2000 or higher) because they cannot be made. Therefore, very thick coatings are required to ensure sufficient mechanical and chemical resistance. In addition, this wet coating method has a large pollution causing factor, it was necessary to replace it with a more environmentally friendly process.

Dry coating of thin films using plasma such as ion plating and PACVD can produce high energy ion bombardment to coat a variety of high quality thin films and has an advantage of being environmentally friendly. However, since the technique of inducing plasma to the inner surface of the cylinder is limited, this dry coating method has a limitation in the length / inner diameter ratio that enables uniform coating on the inner surface of the cylinder.

Recently, an inner wall coating technique for guiding plasma to the inner surface of a cylinder by using a magnetic field, such as a running plasma, has been actively studied. It became possible. However, these methods have a limitation in that they cannot form ions of sufficient energy necessary for the synthesis of dense thin films having high hardness and wear resistance. Therefore, these methods are practically not utilized at all in the coating of a hard thin film on the inner surface of the cylinder.

On the other hand, laser ablation is a technology capable of synthesizing high temperature superconductors, dielectric thin films and amorphous diamond-like carbon thin films, and is being actively researched since the early 1980s. In particular, the amorphous diamond-like carbon thin film synthesized by laser ablation has a very high hardness, excellent lubricity, abrasion resistance, and chemical stability, and is also called an amorphous diamond. In laser ablation, thin films of various materials can be synthesized by varying the target material.

Accordingly, the present inventors have intensively studied a method of uniformly coating a high hardness thin film on the cylinder in the longitudinal direction while avoiding the problem of environmental pollution and limitations on the coating material. In addition, the ion generation source can be easily guided to the inside of the cylinder by the straightness of the laser to form a uniform coating on the inner surface of the cylinder, thereby uniformly coating a dense thin film of high hardness having wear resistance, high lubricity and corrosion resistance It has been found that the present invention can be completed and the present invention has been completed.

Accordingly, an object of the present invention is to provide a thin film of carbide or nitride of Cr or Ti by laser ablation to impart excellent mechanical and chemical properties such as corrosion resistance, abrasion resistance and abrasion resistance to inner surfaces of tubes and cylinders used for various piping materials. It is to provide a method for uniformly coating a high hardness and dense thin film such as an amorphous diamond-like carbon thin film in the longitudinal direction.

It is another object of the present invention to provide a coating apparatus for use in uniformly coating longitudinally dense thin films of high hardness by laser ablation on an inner surface of a tube or cylinder.

1 is a schematic diagram of a laser ablation coating apparatus according to the present invention.

Figure 2 is a graph showing the tendency of monolithically increasing the hardness of the thin film according to the present invention from 15 to 25 kPa as measured by nanoindentation (nanoindentation).

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

1: tube or cylinder 2: vacuum flange

3: excimer laser 4: optical window

5: gas feedthrough 6: lens

7: target material

The object of the present invention,

Mount an ablation target made of coating material on the central axis inside the tube or cylinder to be coated on the inner wall,

An excimer laser beam of UV wavelength is focused into the center axis of the tube or cylinder with a parallel beam to guide the inside of the tube or cylinder,

Laser ablation, wherein the ablation target material is rotated and moved back and forth along the central axis of the tube or cylinder, thereby uniformly longitudinally coating a thin film of the coating material on the inner wall of the tube or cylinder. It is achieved by the method of coating the inner wall of a tube or cylinder using a ration.

In the method of the present invention, the ablation target may use various materials depending on the material to be coated. For example, graphite is used to coat an amorphous diamond-like carbon thin film. In addition, Cr or Ti may be used as an ablation target. In this case, a nitride or carbide thin film of Cr or Ni may be formed by introducing a reactive gas such as nitrogen and methane into the tube or cylinder while causing laser ablation. It can also be coated.

In addition, according to the present invention,

A vacuum flange (2) for sealing both ends of the tube or cylinder (1) to be coated on the inner wall to make the interior vacuum;

A gas inlet (5) for introducing a reactive gas and a UV optical window (4) for guiding an excimer laser beam (3) of UV wavelength into a tube or cylinder, provided on one side of the flange;

A target manipulator for fixing a vacuum port, a gauge port, and a target material (7) installed on the flange opposite the flange on which the UV optical window and the gas inlet are installed;

Means (6) for concentrating the excimer laser with a parallel beam and positioning it on the central axis of the cylinder; And

An apparatus for coating an inner wall of a tube or cylinder using laser ablation is provided, which comprises means for moving back and forth within the tube or cylinder while rotating the ablation target material.

In the laser ablation coating apparatus according to the present invention, a lens 6 may be used as a means for condensing the excimer laser with a parallel beam and positioning it on the central axis of the cylinder.

Hereinafter, the present invention will be described in more detail with reference to the schematic diagram of FIG. 1.

1 is a schematic diagram of a laser ablation coating apparatus for use in the inner wall coating method of a tube or cylinder according to the present invention. Referring to Fig. 1, first, both ends of a tube or cylinder 1 to be coated are sealed with a vacuum flange 2, and the inside of the cylinder is brought into a vacuum state. A flange on one side of the tube is provided with a UV optical window 4 and a gas inlet for introducing a reactive gas so that a high power excimer laser beam of UV wavelength can be transmitted, and a vacuum port, a gauge port and a target on the opposite flange. Install the Manipulator.

The excimer laser is condensed by means of a lens 6 into a very small parallel beam, positioned on the central axis of the cylinder, and inside the cylinder while rotating the ablation target material 7 fixed to the target manifold at a low speed. Moving back and forth results in a very uniform inner coating in the longitudinal direction of the cylinder.

Hereinafter, the advantages and effects obtained by the coating method according to the present invention through the embodiments will be described in more detail. In the following examples, but limited to the case of CrN, the scope of the present invention is not limited to this embodiment, it is also possible to coat a wide variety of thin films according to the type of target material and reactive gas.

<Example 1>

After washing the AISI4210 steel pipe with a length of 1 m x 10 cm using trichloroethylene (TCE), acetone and ethanol, flanges were installed at both ends of the steel pipe as shown in FIG. 1 and a turbo molecular pump system Pump System) was used to vacuum up to 10 ^-6 Torr. Using KrF (wavelength 248 nm, pulse energy 350 mJ) excimer laser, two cylindrical lenses and one lens are used to make a parallel beam of size 0.3 mm, divergence 6 × 10 ^-3 radians. It was located on the central axis of the steel pipe. The opposite flange was mounted with a Cr target at an angle of 45 ° to the laser beam and moved at a feed rate of 1 cm / min while rotating at a rotational speed of 1 rpm. The pulse rate of the laser used for the synthesis of the thin film was 10 Hz and the pulse energy was varied from 100 mJ to 300 mJ. At this time, the synthesis rate of the Cr thin film was measured at 10㎛ / h. By this process, a pure Cr layer was coated to a thickness of 0.5 μm on the inner wall of the AISI4210 steel pipe. This process is essential to enhance the adhesion of the CrN layer to be coated in the next step.

After the coating of the Cr layer was completed, the N ₂ gas was introduced at a flow rate of 5-10 sccm while the Cr target was rotated at a rotational speed of 0.5 rpm while moving in the opposite direction at a feed rate of 5 mm / min to the inner wall of the steel pipe. The CrN layer was coated.

<Example 2>

According to the method of Example 1, the cross section of the coated steel pipe was cut and observed with a scanning electron microscope. As a result, it was confirmed that the entire coating layer had a thickness of 1.3 ± 0.1 μm and was coated with a very uniform thin film in the longitudinal direction.

The composition of the thin film was a function of the output of the irradiated laser beam and the nitrogen flow rate, and the Cr: N ratio was 1: 1 at a laser beam of 200 mJ and a nitrogen flow rate of 10 sccm.

The hardness of the thin film was measured by nano-indensation after coating by attaching a small Si plate in the tube, which tended to monotonously increase from 15 to 25 kPa as the laser power increased.

<Example 3>

According to the method of Example 1, coated and uncoated steel pipes at 20 ° C of 10% After maintaining for 1 hour in dilute sulfuric acid solution, the degree of damage to the inner surface was observed, and no damage was observed on the inner surface of the coated steel pipe, but 10 per 1 cm 2 on the inner surface of the uncoated steel pipe.³More than one surface etch pit was observed. This shows that the CrN coating layer according to the present invention is very dense.

Since the method of coating the inner wall of the tube or cylinder using the laser ablation of the present invention is a dry process, there is no pollution-causing factor, and the ion generation source can be easily induced into the cylinder using the straightness of the laser so that uniform coating on the inner surface of the cylinder is possible. There is no limitation of the length / inner diameter ratio.

In addition, the plasma plume generated by laser ablation generates ions with high ion energy, and since most of these ions are ionized, a high energy ion collision is applied to the surface of the coating layer by applying a bias voltage to the tube or cylinder. In this case, a dense thin film of high density, which could not be realized by the conventional method, can be coated on the inner wall of the cylinder, thereby providing corrosion resistance, abrasion resistance and abrasion resistance to the inner wall of the tube and the cylinder.

Claims (5)

Mount an ablation target made of coating material on the inner central axis of the tube or cylinder to be coated on the inner wall, An excimer laser beam of UV wavelength is focused into the center axis of the tube or cylinder with a parallel beam to guide the inside of the tube or cylinder, Laser ablation comprising uniformly coating the thin film longitudinally on the inner wall of the tube or cylinder by causing laser ablation while rotating and moving the ablation target material along the central axis of the tube or cylinder Method for coating inner walls of tubes or cylinders using ration. The method of claim 1, wherein the ablation target is graphite and the amorphous diamond-like carbon thin film is coated on the inner wall of the tube or cylinder. The method of claim 1, wherein the ablation target is Cr or Ti, and while causing the laser ablation, additional nitrogen or methane reactive gas is introduced into the tube or cylinder to cause Cr or Ti to the inner wall of the tube or cylinder. Method of coating a carbide or nitride thin film. A vacuum flange for sealing both ends of the tube or cylinder to be coated on the inner wall to make the inside vacuum; A gas feedthrough for introducing a UV optical window and a reactive gas for guiding an excimer laser beam of UV wavelength into a tube or cylinder, which is installed at one side of the flange; A target manipulator that moves back and forth while rotating inside the tube or cylinder, fixing a vacuum port, a gauge port, and a target material installed on the flange opposite the flange in which the UV optical window and the gas inlet are installed. ); And Means for focusing the excimer laser with a parallel beam and positioning it on the central axis of the cylinder Including, the inner wall coating apparatus of the tube or cylinder using laser ablation. 5. The apparatus of claim 4 wherein the means for concentrating the excimer laser with a parallel beam to position on the central axis of the cylinder is a lens.