KR20230052220A - Processing method - Google Patents

Abstract

A technology of forming an aluminum oxide layer with low surface roughness on the surface of a substrate is provided. A processing method according to an aspect of the present disclosure includes a process of preparing a substrate, a process of forming an aluminum film on the surface of the substrate, a process of diffusing and infiltrating the aluminum into the substrate by heat-treating the substrate at a first temperature, and a process of forming an aluminum oxide layer by heat-treating the substrate, into which the aluminum has been diffused and infiltrated, at a second temperature higher than the first temperature.

Description

Processing method {PROCESSING METHOD}

The present disclosure relates to processing methods.

A technique of coating alloy steel with aluminum, then heating the aluminum in the coating to oxidize the aluminum, thereby forming an alumina layer is known (see Patent Document 1, for example).

Japanese Patent Laid-Open No. 8-193258

The present disclosure provides a technique capable of forming an aluminum oxide layer having a small surface roughness on the surface of a substrate.

A treatment method according to one aspect of the present disclosure includes a step of preparing a substrate, a step of forming an aluminum film on the surface of the substrate, and a step of diffusing and infiltrating the aluminum into the substrate by heat-treating the substrate at a first temperature; , and a step of forming an aluminum oxide layer by heat-treating the substrate into which the aluminum has diffused and penetrated at a second temperature higher than the first temperature.

According to the present disclosure, an aluminum oxide layer having a small surface roughness can be formed on the surface of a substrate.

1 is a flowchart showing an example of a processing method according to an embodiment.
2 is a diagram showing the results of composition analysis.
3 is a diagram showing the results of composition analysis.
4 is a diagram showing the results of composition analysis.
5 is a diagram showing measurement results of surface roughness.
6 is a diagram showing measurement results of surface roughness.
7 is a diagram showing the results of corrosion resistance evaluation.
8 is a diagram showing the results of corrosion resistance evaluation.
9 is a diagram showing the results of corrosion resistance evaluation.
10 is a diagram showing the results of corrosion resistance evaluation.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of a non-limiting example of this disclosure is described, referring an accompanying drawing. In all attached drawings, about the same or corresponding member or component, the same or corresponding reference code|symbol is attached|subjected, and redundant description is abbreviate|omitted.

[Processing method]

Referring to FIG. 1, an example of the processing method of the embodiment will be described. The processing method of the embodiment includes forming an aluminum oxide layer on the surface of the substrate by performing the substrate preparation step S1, the film forming step S2, the first heat treatment step S3, and the second heat treatment step S4 in this order. Hereinafter, each process is demonstrated.

(substrate preparation step S1)

The base material preparation step S1 is a step of preparing a base material to be treated. As the substrate, for example, a metal that does not contain aluminum (Al) (hereinafter referred to as "non-Al metal") or an alloy that does not contain Al (hereinafter referred to as "non-Al alloy") can be used. Examples of the non-Al metal include rolled steel materials (SS materials) for general structures. Examples of non-Al alloys include stainless steels such as SUS304, SUS316 and SUS316L, and nickel base alloys such as NCF600. Moreover, as a base material, you may use the metal containing Al and the alloy containing Al. However, from the viewpoint of low material cost and low processing cost, it is preferable to use a base material formed of a non-Al metal or non-Al alloy.

(Film Formation Step S2)

The film forming step S2 is a step of forming an aluminum film on the surface of the substrate. Aluminum can be formed into a film by, for example, physical vapor deposition (PVD) such as sputtering, vapor deposition, and ion plating. In the case of forming an aluminum film on the surface of a substrate by PVD, by using a mask such as a metal mask, aluminum can be selectively formed only on a portion where a substrate is required. The thickness of the aluminum film formed on the surface of the substrate in the film forming step S2 may be, for example, 1 μm to 2 μm.

(1st heat treatment process S3)

The first heat treatment step S3 is a step in which the aluminum film formed on the surface of the base material is diffused and penetrated into the base material by heat treating the base material at the first temperature T1. The first heat treatment step S3 is performed in an oxygen-containing atmosphere, for example, an air atmosphere. 1st temperature T1 is determined according to the kind of base material. The first temperature T1 may be equal to or higher than the temperature at which aluminum diffuses and penetrates into the substrate. It is preferable that 1st temperature T1 is a temperature lower than the alloying temperature of aluminum and the metal element contained in a base material. As a result, surface roughness of the substrate due to alloying of the metal element and aluminum contained in the substrate can be suppressed. 1st temperature T1 is 500 degreeC or more and 700 degreeC or less, for example.

(Second Heat Treatment Step S4)

2nd heat treatment process S4 is a process of forming an aluminum oxide layer by heat-processing the base material into which aluminum diffused and permeated at the 2nd temperature T2. The second heat treatment step S4 is performed in an oxygen-containing atmosphere, for example, an air atmosphere. 2nd temperature T2 is determined according to the kind of base material. 2nd temperature T2 is a temperature higher than 1st temperature T1. 2nd temperature T2 is 750 degreeC or more and 1000 degrees C or less, for example.

According to the processing method of the embodiment described above, aluminum is diffused and penetrated into the substrate by forming an aluminum film on the surface of the substrate and then heat-treating the substrate at the first temperature T1. Subsequently, an aluminum oxide layer is formed by heat-treating the substrate through which aluminum has diffused and permeated at a second temperature T2 higher than the first temperature T1. In this way, the temperature at which aluminum diffuses and penetrates into the substrate can be lowered. As a result, since the alloying of the metal element contained in the substrate and aluminum is suppressed, an aluminum oxide layer having a small surface roughness can be formed on the surface of the substrate.

[Example]

(Example 1)

As Example 1, an experiment was conducted to confirm that an aluminum oxide layer was formed on the surface of a substrate by treating the substrate using the treatment method of the embodiment. In Example 1, SUS316L and NCF600 were used as substrates. In Example 1, in the film forming step S2, a 1.6 μm aluminum film was formed on the surface of the substrate by sputtering. In Example 1, in the first heat treatment step S3, the substrate was subjected to heat treatment at 560°C for 3 hours in an air atmosphere. In Example 1, in the second heat treatment step S4, the substrate was subjected to heat treatment at 850°C for 1 hour in an air atmosphere. In Example 1, after the substrate was treated by the treatment method of the embodiment, the atomic concentration in the vicinity of the surface of the treated substrate was measured by X-ray Photoelectron Spectroscopy (XPS).

2 shows aluminum (Al) atomic concentration, oxygen (O) atomic concentration, and iron (Fe) atoms by XPS after performing the film forming step S2 and the first heat treatment step S3 in the processing method of the embodiment for SUS316L. It is a figure showing the result of measuring the concentration. In Fig. 2, the abscissa axis represents the depth from the surface of the substrate [nm], and the ordinate axis represents the atomic concentration [at%]. In Fig. 2, the solid line indicates the Al atom concentration, the broken line indicates the O atom concentration, and the dotted line indicates the Fe atom concentration.

As shown in FIG. 2, it can be seen that the Al atom concentration is substantially uniform at a depth of 1000 nm from the surface of the substrate, and is about 30 at% to 40 at%. On the other hand, it can be seen that the O atom concentration decreases from about 65 at% to about 10 at% over a depth of 1000 nm from the surface of the substrate. In addition, it can be seen that the Fe atom concentration rises from 0 at% to about 35 at% over a depth of 1000 nm from the surface of the substrate. From these results, it was shown that aluminum diffused and penetrated into SUS316L by performing the film forming step S2 and the first heat treatment step S3 in the processing method of the embodiment in this order with respect to SUS316L.

3 shows the aluminum (Al) atomic concentration, oxygen (O) atomic concentration and It is a diagram showing the result of measuring the iron (Fe) atom concentration. In Fig. 3, the abscissa axis represents the depth from the surface of the substrate [nm], and the ordinate axis represents the atomic concentration [at%]. In Fig. 3, the solid line indicates the Al atom concentration, the broken line indicates the O atom concentration, and the dotted line indicates the Fe atom concentration.

As shown in Fig. 3, it can be seen that the Al atom concentration is approximately uniform at a depth of 400 nm from the surface of the substrate, and is about 35 at%. In addition, it can be seen that the O atom concentration is substantially uniform at a depth of 400 nm from the surface of the substrate, and is about 65 at%. In addition, it can be seen that the Fe atom concentration is about 0 at% at a depth of 400 nm from the surface of the substrate. From these results, it was revealed that an aluminum oxide layer was formed at a depth of up to 400 nm from the surface of the substrate.

4 shows the aluminum (Al) atomic concentration, oxygen (O) atomic concentration and It is a figure showing the result of measuring the nickel (Ni) atom concentration. In Fig. 4, the abscissa axis represents the depth from the surface of the substrate [nm], and the ordinate axis represents the atomic concentration [at%]. In Fig. 4, the solid line indicates the concentration of Al atoms, the broken line indicates the concentration of O atoms, and the dotted line indicates the concentration of Ni atoms.

As shown in Fig. 4, it can be seen that the Al atom concentration is approximately uniform at a depth of 200 nm from the surface of the substrate, and is about 35 at%. In addition, it can be seen that the O atom concentration is substantially uniform at a depth of 200 nm from the surface of the substrate, and is about 65 at%. In addition, it can be seen that the Ni atom concentration is about 0 at% at a depth of 200 nm from the surface of the substrate. From these results, it was revealed that an aluminum oxide layer was formed at a depth of up to 200 nm from the surface of the substrate.

(Example 2)

As Example 2, an experiment was conducted to confirm that an aluminum oxide layer having a small surface roughness was formed on the surface of the substrate by treating the substrate using the treatment method of the embodiment. In Example 2, after the substrate was treated by the treatment method of the embodiment, the surface roughness of the substrate was measured with a laser microscope. In Example 2, SUS316L and NCF600 were used as substrates. In Example 2, a 1.6 μm aluminum film was formed on the surface of the substrate by sputtering in the film forming step S2. In Example 2, in the first heat treatment step S3, the substrate was subjected to heat treatment at 560°C for 3 hours in an air atmosphere. In Example 2, in the second heat treatment step S4, the substrate was subjected to heat treatment at 850°C for 1 hour in an air atmosphere. In addition, for comparison, after forming an aluminum oxide layer on the surface of the substrate by calorizing instead of the treatment method of the embodiment, the surface roughness of the substrate was measured with a laser microscope.

5 is a diagram showing measurement results of the surface roughness of a base material in the case of using SUS316L as the base material. In FIG. 5, the bar graph shows the rate of change of the measured value of the surface of the substrate after treatment with respect to the measured value of the surface of the substrate before treatment. In FIG. 5 , the bar graph described as “after the first heat treatment” shows the result when the film forming step S2 and the first heat treatment step S3 in the processing method of the embodiment are performed on the substrate. In addition, the bar graph described as "after the second heat treatment" shows the results when the film forming step S2, the first heat treatment step S3, and the second heat treatment step S4 in the treatment method of the embodiment are performed on the substrate. In addition, the bar graph described "after the calorizing treatment" shows the result when the calorizing treatment is performed with respect to the base material. In Fig. 5, "Ra" and "Ry" are the arithmetic average roughness and maximum height roughness defined in JISB0601:2013, respectively, and "S" is the surface area of the substrate surface.

As shown in Fig. 5, it can be seen that the maximum height roughness Ry is smaller in "after second heat treatment" than in "after calorizing treatment". From this result, when SUS316L is used as the substrate, by treating the substrate using the treatment method of the embodiment, an aluminum oxide layer having a smaller surface roughness can be formed on the surface of the substrate than when the substrate is treated using a calorizing treatment. What could have appeared.

6 is a diagram showing measurement results of the surface roughness of a substrate in the case of using NCF600 as the substrate. In FIG. 6 , a bar graph shows a rate of change in the measured value of the surface of the substrate after treatment with respect to the measured value of the surface of the substrate before treatment. In FIG. 6 , the bar graph described as “after the first heat treatment” shows the result when the film forming step S2 and the first heat treatment step S3 in the treatment method of the embodiment are performed on the substrate. In addition, the bar graph described as "after the second heat treatment" shows the results when the film forming step S2, the first heat treatment step S3, and the second heat treatment step S4 in the treatment method of the embodiment are performed on the substrate. In addition, the bar graph described "after the calorizing treatment" shows the result when the calorizing treatment is performed with respect to the base material. In Fig. 6, "Ra" and "Ry" are the arithmetic mean roughness and maximum height roughness defined in JISB0601:2013, respectively, and "S" is the surface area of the substrate surface.

As shown in FIG. 6 , it can be seen that the arithmetic average roughness Ra and the maximum height roughness Ry are smaller in “after the second heat treatment” than in “after the calorizing treatment”. From this result, even in the case of using NCF600 as the substrate, it is possible to form an aluminum oxide layer having a small surface roughness on the surface of the substrate by treating the substrate using the treatment method of the embodiment and by treating the substrate using the calorizing treatment. What could have appeared.

(Example 3)

As Example 3, an experiment was conducted to confirm that an aluminum oxide layer having high corrosion resistance to corrosive gas was formed on the surface of the substrate by treating the substrate using the treatment method of the embodiment. In Example 3, after forming an aluminum oxide layer on the surface of the substrate by the treatment method of the embodiment, the substrate was exposed to ClF ₃ gas, which is a corrosive gas. In addition, elemental analysis of the surface of the substrate before and after exposure to ClF ₃ gas was performed by energy dispersive X-ray spectroscopy (EDX). In Example 3, SUS316L and NCF600 were used as substrates. In Example 3, a 1.6 μm aluminum film was formed on the surface of the substrate by sputtering in the film forming step S2. In Example 3, in the first heat treatment step S3, the substrate was subjected to heat treatment at 560°C for 3 hours in an air atmosphere. In Example 3, in the second heat treatment step S4, the substrate was subjected to heat treatment at 850°C for 1 hour in an air atmosphere. In Example 3, when the substrate is exposed to the ClF ₃ gas, the substrate is accommodated in a chamber, the temperature in the chamber is adjusted to 400°C and the pressure is 3 kPa, and the ClF ₃ gas is supplied into the chamber at a flow rate of 100 sccm. , held for 5 hours. In addition, for comparison, after forming an aluminum oxide layer on the surface of the substrate by calorizing treatment instead of the treatment method of the embodiment, the substrate is exposed to ClF ₃ gas, and before and after exposure to ClF ₃ gas by EDX. Elemental analysis of the surface of the substrate was performed.

7 and 8 are diagrams showing the results of elemental analysis in the case of using SUS316L as a base material. Fig. 7 shows the result when an aluminum oxide layer is formed on the surface of the substrate by the treatment method of the embodiment, and Fig. 8 shows the result when the aluminum oxide layer is formed on the surface of the substrate by calorizing treatment. 7 and 8, the bar graph shows the composition ratio [weight (wt)%] of the substrate. In FIGS. 7 and 8 , bar graphs labeled “before exposure” show the composition ratio before exposing the substrate to ClF ₃ gas, and bar graphs written “after exposure” show the composition ratio after exposing the substrate to ClF ₃ gas.

As shown in FIG. 7 , when an aluminum oxide layer is formed on the surface of a substrate by the treatment method of the embodiment, it is found that the F concentration, which was 0 wt% before exposure, increases to 6.58 wt% after exposure. In addition, as shown in FIG. 8, when an aluminum oxide layer is formed on the surface of the substrate by calorizing treatment, it can be seen that the F concentration, which was 0 wt% before exposure, increased to 10.03 wt% after exposure. That is, when the aluminum oxide layer is formed on the surface of the substrate by the treatment method of the embodiment, the F concentration after exposure to the ClF ₃ gas is lower than when the aluminum oxide layer is formed on the surface of the substrate by calorizing treatment. Able to know. From these results, when SUS316L was used as the substrate, it was found that an aluminum oxide layer having high corrosion resistance to ClF ₃ gas can be formed on the surface of the substrate by using the treatment method of the embodiment and by using the calorizing treatment.

9 and 10 are diagrams showing the results of elemental analysis in the case of using NCF600 as a base material. Fig. 9 shows the result when an aluminum oxide layer is formed on the surface of the substrate by the treatment method of the embodiment, and Fig. 10 shows the result when the aluminum oxide layer is formed on the surface of the substrate by calorizing treatment. 9 and 10, the bar graph shows the composition ratio [weight (wt)%] of the substrate. In FIGS. 9 and 10 , bar graphs labeled “before exposure” show the composition ratio before exposing the substrate to ClF ₃ gas, and bar graphs written “after exposure” show the composition ratio after exposing the substrate to ClF ₃ gas. .

As shown in FIG. 9, when an aluminum oxide layer is formed on the surface of the substrate by the treatment method of the embodiment, the F concentration, which was 0 wt% before exposure, increases to 2.64 wt% after exposure. It can be seen. In addition, as shown in FIG. 10, when an aluminum oxide layer is formed on the surface of the substrate by calorizing treatment, it is found that the F concentration, which was 0 wt% before exposure, increases to 3.68 wt% after exposure. That is, when an aluminum oxide layer is formed on the surface of the substrate by the treatment method of the embodiment, the F concentration after exposure to ClF ₃ gas is lower than when the aluminum oxide layer is formed on the surface of the substrate by calorizing treatment. Able to know. From these results, it was shown that even when NCF600 is used as the substrate, an aluminum oxide layer having high corrosion resistance to ClF ₃ gas can be formed on the surface of the substrate by using the treatment method of the embodiment or by using the calorizing treatment. .

Embodiment disclosed this time is an illustration in all points, and it should be thought that it is not restrictive. The above embodiment may be omitted, substituted, or changed in various forms without departing from the appended claims and the gist thereof.

In the above embodiment, the case where the first heat treatment step S3 and the second heat treatment step S4 are performed in an oxygen-containing atmosphere has been described, but the present disclosure is not limited to this. For example, at least one of the first heat treatment step S3 and the second heat treatment step S4 may be performed in a reducing atmosphere. As the reducing atmosphere, an atmosphere containing a reducing gas such as hydrogen gas and an inert gas such as argon gas is exemplified.

Claims (6)

The process of preparing the base material;
A step of forming an aluminum film on the surface of the substrate;
a step of diffusing and infiltrating the aluminum into the substrate by heat-treating the substrate at a first temperature;
A step of forming an aluminum oxide layer by heat-treating the substrate into which the aluminum diffuses and penetrates at a second temperature higher than the first temperature.
Having, processing method. According to claim 1,
The process of diffusion and infiltration and the process of forming the aluminum oxide layer are performed in an atmosphere containing oxygen. According to claim 2,
The processing method in which the atmosphere containing the said oxygen is an air atmosphere. According to any one of claims 1 to 3,
The said base material is stainless steel or a nickel-base alloy, the processing method. According to any one of claims 1 to 4,
The processing method, wherein the substrate is formed of a metal or alloy that does not contain aluminum. According to any one of claims 1 to 5,
The processing method in which the said aluminum is formed into a film on the surface of the said base material by physical vapor deposition.

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