JPH04247863A - Formation of metallic nitride layer - Google Patents

Abstract

PURPOSE:To efficiently form a nitride layer by generating a glow discharge between counter electrodes and forming a nitride layer on the surface of a metallic base body by the reaction of the plasma of the gaseous nitrogen generated at this time and the metallic base body. CONSTITUTION:The positive electrode 2 and the negative electrode 3 facing each other are disposed within a hermetic vessel (vacuum vessel) 1. The metallic base body 4 is imposed on the negative electrode 3. The inside of the hermetic vessel 1 is evacuated by using a vacuum discharge system 8. The gaseous nitrogen is thereafter introduced from a gaseous nitrogen cylinder 6 into the vessel 1 to attain a prescribed pressure. A DC voltage is impressed between the counter electrodes 2 and 3 to generate the glow discharge. The nitride layer is formed on the surface of the metallic base body 4 by the reaction of the plasma of the gaseous nitrogen generated at this time and the metallic base body 4. The nitride layer is easily formed over the entire circumference without receiving restrictions in the shape of the metallic base body.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a nitride layer having excellent mechanical strength and corrosion resistance on the surface of a metal.

0002

[Prior Art] Nitride layers are formed on the surfaces of Al, Ti, stainless steel, etc. in order to modify the surface of metals and improve mechanical properties such as friction and wear resistance and corrosion resistance against the atmosphere. is being carried out.

As a method for forming metal nitrides, CV
D method, ■Ion plating method, ■MOCVD method, ■
Ion implantation methods are known. Among these, the ion implantation method (■) ionizes a predetermined element (nitrogen in this case), implants the ions into the metal substrate surface with high acceleration energy, and then heat-treats it at a predetermined temperature to form a nitride on the metal surface. It has the following characteristics compared to the other methods ① to ②.

That is, compared to other methods, the ion implantation method allows a low temperature process of 200°C or less, causes less change in the surface shape of the metal substrate after ion implantation, and improves the adhesion of the nitride layer. It has the advantage that a non-equilibrium phase with a higher solubility can be obtained.

[0005] Therefore, although the ion implantation method has recently begun to be used, even this excellent ion implantation method has the following problems.

[0006]

[Problems to be Solved by the Invention] The ion implantation method is not only limited in the shape and size of the metal used, but also requires a long time to implant the ions, and the ion implantation equipment is expensive. have shortcomings. For example, 100x100x1m
When implanting N+ ions into an Al substrate of m3 to form an AlN layer, the ion implantation conditions are as follows: torse amount: 1×
1018 cm-2, current density: 80 μA/cm2, and acceleration voltage: 50 keV, the processing time is about 30 minutes, so it is not suitable for industrial use. As described above, the method of forming AlN and TiN layers by ion implantation has problems such as being too expensive and time-consuming, and being applicable only to plate-shaped metal substrates such as Al and Ti. There is.

The present invention has been made to solve the above-mentioned drawbacks, and its object is to provide a method that can efficiently form a metal nitride on the surface of a metal substrate having an arbitrary shape.

[0008]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the method of the present invention includes disposing a metal substrate on the negative electrode side between opposing positive and negative electrodes in a closed container, and then Nitrogen gas is introduced at a pressure of , and a DC voltage is applied between the positive and negative electrodes to generate nitrogen plasma and form a nitride layer on the surface of the metal substrate.

[0009]

[Operation] As described above, the method of the present invention involves applying a DC voltage between the metal substrate on the negative electrode side and the positive electrode, which are placed in a closed container filled with nitrogen gas at a predetermined pressure.
Nitrogen radicals and nitrogen ions in the generated nitrogen plasma react with the metal substrate, and at the same time, nitrogen ions accelerated by this DC voltage penetrate into the metal substrate, forming a nitride layer on the surface of the metal substrate. .

0010

EXAMPLES The present invention will be explained below based on examples.

FIG. 1 is a schematic diagram showing the main structure of an apparatus to which the nitride layer forming method of the present invention is applied. FIG. 1 shows an apparatus for forming a nitride layer 11 on the surface of a plate-shaped metal substrate 4. In FIG. In FIG. 1, a positive electrode 2 and a negative electrode 3 facing each other are arranged in a vacuum container 1, and a plate-shaped metal substrate 4 is placed on the negative electrode 3. A glow discharge DC power source 5 installed outside the vacuum container 1 is connected to the positive electrode 2,
Nitrogen gas is sent from a nitrogen gas cylinder 6 into the vacuum container 1 through an adjustment circuit 7 for adjusting the pressure and flow rate of nitrogen gas. A regulating valve 9 for adjusting the gas pressure during glow discharge is connected between the vacuum vessel 1 and the evacuation system 8, and a vacuum gauge 10 is separately attached to the vacuum vessel 1.

[0012] In order to form a nitride layer on the surface of the metal substrate 4 using this apparatus, first, the inside of the vacuum container 1 is evacuated by the vacuum evacuation system 8 to create a vacuum of about 1 x 10-7 torr. The regulating valve 9 is throttled to reduce the exhaust speed of the evacuation system 8, and at the same time nitrogen gas is introduced into the vacuum container 1 through the regulating circuit 7 to adjust the gas pressure to a predetermined value. After that, when a DC voltage is applied between the positive electrode 2 and the negative electrode 3 to cause a glow discharge and generate nitrogen gas plasma, the nitrogen ions generated at this time react with the metal substrate 4, and at the same time, The accelerated nitrogen ions can penetrate into the metal substrate 4 and form a nitride layer 11 on the surface of the metal substrate 4.

Next, a specific example of forming a metal nitride on the surface of a metal substrate by the method of the present invention will be shown.

The conditions for forming metal nitride are as follows. Metal substrate: Al plate, mirror finish Substrate temperature: 200℃ Nitrogen gas pressure: 2.0torr Discharge conditions: DC600V, 0.6mA/cm2 Distance between electrodes: 50mm

FIG. 2(a) shows the distribution of Al and N in the depth direction of the AlN layer thus obtained by Auger electron spectroscopy (AES). Figure 2(b) also shows the case of the AlN layer.
It was shown to. Ion implantation conditions were acceleration voltage: 50 keV,
Dose amount: 1×10 18 cm −2 . Figure 2(a),
From the comparison in (b), the present invention shows that the AlN layer formed near the surface gradually decreases toward the inside, and the
It can be seen that the surface is in an extremely favorable state as a surface modified layer by IN.

FIG. 3 shows the relationship between the AlN layer and the Al layer shown in FIG. 2(a).
This figure shows the Auger electron spectrum of Al as a substrate. As shown in Figure 3, the Auger electron kinetic energies of Al that breaks down into the AlN layer are 58 keV (LVV) and 1384 k.
eV (KLL), and in the Al substrate, it is 70 keV (
LVV) and 1390 keV (KLL). In this way, the phenomenon in which the peak position of the Auger electron kinetic energy of Al in the AlN layer moves to a lower energy side compared to the case of the Al base is due to chemical shift, and Al in the metallic state changes to AlN. It indicates that Of course, a similar Auger electron spectrum can be obtained using the ion implantation method as well.

FIG. 4 is a schematic diagram showing an apparatus configuration for forming a nitride layer on the entire surface including the back surface of the metal substrate 4.
Components common to those in FIG. 1 are designated by the same reference numerals. Figure 4 is Figure 1
The difference is that the metal base 4 is used as a negative electrode and is placed between two opposing positive electrodes 2a and 2b, and the metal base 4 is used as a negative electrode.
The reason is that the nitride layer 11a is formed on the entire surface extending to the back surface.

FIG. 5 is a schematic diagram showing the configuration of an apparatus for forming a nitride layer on the outer peripheral surface of a metal substrate 4a having a cylindrical shape. Parts common to those in FIGS. 1 and 4 are designated by the same reference numerals. 5 is different from FIGS. 1 and 4 in that the metal base 4a is a negative electrode, the positive electrode 2c is cylindrical and is placed outside the metal base 4a, and the outer peripheral surface of the metal base 4a is nitrided. This is because the material layer 11b was formed. Also, although not shown, by arranging another positive electrode inside the metal base 4a, a nitride layer can be simultaneously formed on the outer and inner peripheral surfaces of the metal base 4a.

One of the advantages of the method of the present invention is as shown in FIG.
As shown in FIG. 5, an AlN layer can be obtained under the same formation conditions as described in FIG. also has similar characteristics.

Furthermore, as the metal substrates 4 and 4a, a metal nitride layer can be formed on the surface of Ti, Fe, stainless steel, etc. in addition to Al in the same manner as described above.

[0021]

Effects of the Invention: In order to modify the surface of a metal and improve its wear resistance and corrosion resistance, there is a method for forming a nitride layer of the metal on the surface, such as ion implantation. It was not an appropriate method as the layer lacked stability and the processing time was long. On the other hand, according to the method of the present invention, as explained in the examples, a predetermined metal substrate is placed in nitrogen plasma generated by direct current glow discharge so as to have a negative potential. It has become possible to efficiently form a nitride layer that is smoothly distributed from the surface to the depth direction. In particular, if the metal substrate is used as a negative electrode and a positive electrode is placed around it without any major restrictions on the shape of the metal substrate, a nitride layer can be easily formed almost all around the metal substrate. When the metal substrate is plate-shaped, a nitride layer can be formed on only one surface or on both the front and back surfaces at the same time, which greatly expands the range of applications compared to conventional methods.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the main part configuration of an apparatus to which the nitride layer forming method of the present invention is applied.

[Figure 2] (a) is a distribution map of Al and N in the depth direction obtained by Auger electron spectroscopy of the AlN layer obtained by the method of the present invention, and (b) is shown for comparison with (a). Distribution diagram of Al and N in the depth direction obtained by Auger electron spectroscopy of an AlN layer formed by ion implantation method

[Figure 3] Auger electron spectrum diagram of Al in the AlN layer and Al substrate obtained by the method of the present invention

FIG. 4 is a schematic diagram of the main part configuration of an apparatus to which the nitride layer forming method of the present invention is applied, showing an embodiment different from FIG. 1;

[Figure 5]
A schematic diagram of the main part configuration of an apparatus to which the nitride layer forming method of the present invention is applied, showing an embodiment different from FIGS. 1 and 4.

[Explanation of symbols]

1 Vacuum container 2 Positive electrode 2a Positive electrode 2b Positive electrode 2c Positive electrode 3 Negative electrode 4 Metal base 4a Metal base 5 DC power supply 6 Nitrogen gas cylinder 7 Adjustment circuit 8 Vacuum exhaust system 9 Adjustment valve 10 Vacuum gauge 11 Nitride layer 11a Nitride layer 11b Nitride layer

Claims (5)

[Claims] Claim 1: A method for forming a nitride layer on the surface of a metal substrate, comprising: evacuating the airtight container in which the metal substrate is placed on the negative electrodes of opposing positive and negative electrodes, and introducing nitrogen gas to maintain a predetermined pressure. After that, a direct current voltage is applied between the opposing electrodes to cause glow discharge, and a nitride layer is formed on the surface of the metal substrate by a reaction between the nitrogen gas plasma generated at this time and the metal substrate. A method for forming a metal nitride layer. 2. A method for forming a metal nitride layer according to claim 1, wherein a metal substrate on which a nitride layer is formed is used as the negative electrode. 3. A method for forming a metal nitride layer according to claim 1 or 2, wherein the metal substrate is Al. 4. A method for forming a metal nitride layer according to claim 1 or 2, wherein the metal substrate is Ti. 5. The method of forming a metal nitride layer according to claim 1 or 2, wherein the metal substrate is Fe or an alloy thereof.