JPS6033190B2 - Method for forming a silicon carbide film with excellent adhesion on the surface of a metal substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming a carbonized raw film with excellent adhesion on the surface of a metal substrate using a plasma chemical vapor deposition method.

Traditionally, cutting tools such as woodworking drills and saw blades, dies, bearings, and wear-resistant parts such as guides for textile machinery have been given wear resistance, and mechanical seals have been used to resist acids and alkali. For the purpose of imparting corrosion resistance, and to impart non-magnetism and wear resistance to the guide pins and head surfaces of magnetic tapes,
Coating with carbonized carbide (hereinafter referred to as SIC), which has high hardness and excellent wear resistance and corrosion resistance, has been carried out.

This SIC coating is usually produced by plasma chemical vapor deposition, which has a low reaction temperature and good coating adhesion, in which a compound is deposited on the surface of a metal substrate using glow discharge in a reduced pressure atmosphere of 0.1 to several torr. It is formed by However, SIC has a thermal expansion coefficient of 4 × 10-6 +-1℃-1
And the coefficient of thermal expansion of metals such as steel and AI: 10 to 25 x 1
This difference in coefficient of thermal expansion makes it difficult for the SIC film to form, especially if the formation of the SIC film has to be carried out at high reaction temperatures for the purpose of obtaining good quality. Cracks often occur in the film, and in severe cases, peeling occurs.

Therefore, from the above-mentioned viewpoint, the present inventors conducted research to form a SIC film with excellent adhesion on the surface of a metal substrate without cracking or peeling, and found that it was possible to form an SIC film on the surface of a metal substrate using plasma chemical vapor deposition. If a Si film is vapor-deposited on the surface of the metal substrate before forming the SIC film,
Since this Si film is amorphous without crystallization, the coefficient of thermal expansion of crystalline Si is 6.
~7xlo-6 skin-1℃-1 greater coefficient of thermal expansion: 7
~8×10-6ｽ-1℃-1, and this thermal expansion coefficient is intermediate between that of the SIC film and the metal substrate, so the SI
Since the strain that occurs due to the difference in thermal expansion during the formation of the SIC film between the C film and the metal substrate is alleviated, the occurrence of cracks and peeling is significantly suppressed. Although it has lower hardness than SIC, it has high metallic malleability, so it acts as a buffer against mechanical shock, and the formation of the Si film and SIC film is continuous. Since the adhesion between the Si film and the SIC film is strong, and the adhesion between the Si film and the surface of the metal substrate is also excellent, it is possible to form a strong SIC film on the surface of the metal substrate as a whole. I gained knowledge.

This invention has been made based on the above knowledge, and it is desirable that the thickness of the Si film is 0.5 to 10 Am. This means that if the thickness is less than 0.5 Am, the desired effect will not be achieved. This is because if the thickness exceeds 10 mm, problems caused by the softness of Si, such as plastic deformation, tend to occur.

Next, the method of the present invention will be specifically explained using examples.

Example 1 The experiment was carried out using a plasma chemical hollywood mounting system shown schematically in FIG.

The apparatus shown in FIG. 1 includes a vacuum chamber 7 surrounded by a heater 6 on the outer peripheral side, and a vacuum chamber 7 housed within the vacuum chamber and connected to the e side of a power source (high frequency or direct current) 4 through an insulator 5. an exhaust pump 3 that opens into the vacuum chamber, and a C2 source, an Ar source, a 2 source, and a SiH4 source that also open into the vacuum chamber via a flow meter 8. It consists of things. That is, in the apparatus shown in FIG.
The metal base S is placed on top of the SUS304 container.
After placing the KD-11 dice, the temperature inside the vacuum chamber 7 is raised to 30,000, and the exhaust pump 3 is turned on.
The pressure in the vacuum chamber was reduced to 5 x 10-4 Torr, and then Ar was introduced to bring the pressure inside the vacuum chamber to 5 x 10-2 Torr, and a negative voltage of -700 V was applied to the electrode 2. A glow discharge was generated to etch the die surface for 5 minutes, followed by flowing SiH4 into the vacuum chamber without evacuating ~ and adjusting the pressure inside the chamber to 0.3 Torr. In this state, a voltage of -450 V was applied to generate a glow discharge, and a reaction was carried out for 30 minutes to form a Si film on the surface of the die.
Subsequently, C2 was introduced into the vacuum chamber while adjusting the molar ratio of Si to C2 to 1:2, and a reaction was carried out for 2 hours to form a SIC film on the Si film. did. As a result, the coating formed on the surface of the die, which is a metal base, consists of three layers of S with a thickness of 1 m and an SI layer with a thickness of 4 m.
It consists of a C layer, is amorphous, and has a microvitkers hardness (H
v: 10 female load): 3200k9/ground. In addition, a test piece made of SKD-11 made of the same material as the above-mentioned die was inserted into the above-mentioned chamber at the same time, and a test piece of the same size and made of the same material was bonded to the film-deposited surface of this test piece using an epoxy adhesive. However, when a tensile test was performed, 5
Peeling occurred at the interface between the adhesive and the coating due to the tensile strength of 00k9/Son.

From this, it is clear that the adhesion strength of the coating to the die substrate is 500k9/ or more. Furthermore, when the resulting die with the Sj coating and the SIC coating was used for green compact compacting in powder metallurgy, it was found that under the same conditions except that the Si coating was not interposed, the die was approximately 3 times smaller than the die with the Si coating directly formed. It showed twice the service life. Note that in the die without the Si coating, the SIC
The adhesion strength between the coating and the die base surface is only 200K.
9/ It was just a sign of the earth. Example 2 The surface of the Ti material was prepared under the same conditions as in Example 1, except that the material of the metal substrate was Ti, the reaction time for forming the CSiC film was 3 hours, and the thickness was 6 mm. A SIC film with a thickness of 6 mm was formed via a Si film with a thickness of 1 mm.

In this case as well, the coating showed an adhesion strength of 500k9/female or more. Example 3 A textile machine guide made of wood was used as the metal base, and Si with a thickness of 0.8 cm was coated on the guide surface under the same conditions as in Example 1, except that the heating temperature in the vacuum chamber was 200q0. Layer and thickness: 3.5 m SIC
The layers were formed by successive vapor deposition.

The resulting film has a Pickers hardness of 3000
It showed a k9/range and an adhesion strength of 500k9/carp or more. Although we attempted to form a SIC layer under the same conditions except that no Si layer was formed, peeling occurred and it was not possible to form a satisfactory SIC layer.
It was not possible to form a layer. Furthermore, when this AI-made textile machine guide with Si coating and SIC coating was incorporated into an actual machine, it exhibited a service life approximately three times longer than that of an alumina (AI203) thermally sprayed guide. Example 4 The metal substrate was a gate valve sliding plate (made of SUS304), a high frequency of 13.58 MHZ was applied to the electrode, the etching output was 200 W, and the reaction output for film formation was 70 W. Example 1
Under the same conditions as in , a coating consisting of a Si layer with a thickness of 2 meters and a SIC layer with a thickness of 6 meters was formed by continuous vapor deposition on the surface of the sliding plate.

This coating also had an adhesion strength of 500k9/female or more and a Vickers hardness of 3200k9/fence. When the resulting sliding plate was used in a pulverized coal transport pipe, it exhibited a service life approximately three times longer than that of a conventional surface nitrided plate. Example 5 Metals were prepared under the same conditions as in Example 1, except that the reaction gas for film formation was not used and the pressure in the vacuum chamber during film formation was 0.2 Torr. The surface of the SKD-11 die, which is the base, has a thickness of 0.8 mm.
A film consisting of a Si layer of 3.5 m thick and a SIC layer of 3.5 m thick was formed by vapor deposition.

The resulting coating has an adhesion strength of over 500k9/m
It had a Vickers hardness of 00k9/Iso.
Example 6 A gate valve with a metal substrate was prepared under the same conditions as in Example 4, except that Ar was not used as a reactive gas for film formation, that is, Ar was completely exhausted from the vacuum chamber after the etching process. A coating consisting of a Si layer with a thickness of 0.8 mm and an SIC layer with a thickness of 3.5 mm was formed on the surface of the sliding plate.

The resulting coating has an adhesion strength of over 500 kg/3
100k9/indicated the Vickers hardness of the fence. Example 7
The metal base is a woodworking drill made of SKH-9, and the SI
When forming the C layer, the reaction gas composition for the initial 30 minutes was set to a molar ratio of Si to C2 of 1:1, and then C2
The amount of inflow on day 2 was increased, and 1.5 hours later, the amount of inflow was 1.
The thickness of the woodworking drill was applied to the surface of the woodworking drill under the same conditions as in Example 1 except that the thickness was changed to:
A film consisting of a Si layer of 1 m thick and an SIC layer of 4 m thick was formed.

In addition, in the SIC layer of the film formed as a result,
Vickers hardness near the boundary with the Si layer: 1500k9/
This hardness increases toward the surface of the coating, and the Vickers hardness at that surface is 3600k9.
/ Pointed to the seashore. The coating also had an adhesion strength of 500k9/base. Furthermore, when this drill with a surface coating was put into practical use, it showed a service life four times longer than that of a drill without coating. As described above, according to the method of the present invention, it is possible to form an SIC film on the surface of a metal substrate without cracking or peeling during film formation and having extremely high adhesion.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a plasma chemical spraying apparatus. In the drawings, 1...metal base, 2...
・Electrode, 3...exhaust pump, 4...power supply,
5...Insulator, 6...Heater, 7...Vacuum chamber, 8...Flowmeter.

Claims (1)

[Claims] 1. When forming a silicon carbide film on the surface of a metal substrate by plasma chemical vapor deposition, a Si film is first vapor-deposited and then a silicon carbide film is formed by vapor deposition. Method of forming silicon carbide film.