JPH06265023A - Rigid convering material, slide member covered therewith, and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve slide characteristics and toughness by a method wherein solid dissolution of given allotment oxygen is carried out in crystalline structure of Cr, in a rigid covering member, such as a piston ring for an internal combustion engine. CONSTITUTION:The outer peripheral surface of a piston ring 1 having formed of a steel and in a rectangular shape in cross section is covered with a rigid film 2 through arc ion plating. In the rigid film 2, solid dissolution of 3-20wt.% oxygen is effected in crystalline structure of CrN and Vickers hardness is set to a range of 1600-2200. Further, the thickness of the film 2 is set to approximate 10-70mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard coating material having improved sliding characteristics and toughness, and is effectively used as a hard coating applied to a sliding surface of a sliding member such as a piston ring for an internal combustion engine. It is something.

[0002]

2. Description of the Related Art In recent years, the use environment of piston rings has become more and more severe with the increase in engine output and exhaust gas handling. The number of engines that cannot satisfy durability performance in terms of treatment has increased. In order to deal with this situation, a hard coating such as TiN or CrN using the PVD method has been proposed. CrN coatings, which can cope with thicker films, are used especially for engines that require durability.

[0003]

The CrN coating is excellent in wear resistance and seizure resistance, has good manufacturability, and is capable of forming a thick coating having a thickness of more than 30 μm. However, since the CrN film has a brittle property in itself, when the surface is subjected to excessive repeated stress due to sliding during use, cracks may occur and the surface may be peeled off.

An object of the present invention is to use Cr as a hard coating material.
It is to improve the sliding characteristics and toughness of N.

[0005]

The hard coating material of the present invention has a CrN crystal structure in which [O] is dissolved in a proportion of 3 to 20% by weight and has a Vickers hardness of 1600 to 1600.
It is characterized by being in the range of 2200.

In the sliding member of the present invention, at least the sliding surface is coated with a hard coating made of the above hard coating material. For example, a piston ring coated with the hard coating made of the above hard coating material is severe. It has sufficient durability even under various conditions. The hard coating material can be coated by ion plating.

[0007]

According to the above-mentioned means, [O] is solid-dissolved in CrN at a predetermined ratio, so that seizure resistance and toughness are improved.

[0008]

1 is a longitudinal sectional view showing a part of a piston ring according to an embodiment of the present invention. The piston ring 1 in this embodiment is a ring having a rectangular cross section made of steel, cast iron, titanium, titanium alloy or the like. A hard coating 2 is coated on the outer peripheral surface of the piston ring 1 by arc ion plating. The hard coating 2 is a crystal structure of CrN in which oxygen [O] is dissolved in a proportion of 3 to 20% by weight, and has a Vickers hardness of 1600 to 220.
It is in the range of 0. The film thickness of the hard coating 2 is 10 μm to 70 μm
m is preferred.

The arc ion plating method is one of the ion plating methods, which uses vacuum arc discharge to vaporize and ionize the coating material of the cathode to form a coating on the surface of the object to be coated. . This arc ion plating method has a feature that the ionization rate of vapor is high and a dense and excellent adhesion film can be obtained.

The basic structure of the arc ion plating apparatus will be described with reference to FIG. In the vacuum chamber 10, a cathode 11 made of a material forming a film and an object 12 to be coated on which the film is formed are installed. The cathode 11 is connected to an arc supply source 13 installed outside the vacuum chamber 10, and the arc supply source 13 is connected to an anode (not shown). A negative bias voltage is applied to the object to be coated 12 by a bias voltage supply source 14. The vacuum chamber 10 has a gas inlet 15 connected to a source of process gas.
And an exhaust port 16 connected to the pump.

Therefore, when an arc discharge is generated between the cathode 11 and the anode in the vacuum chamber 10, the arc forms an arc spot on the surface of the cathode 11 and randomly and at high speed on the surface of the cathode 11. Move to. Due to the energy of the arc current (several tens to several hundreds A) concentrated on the arc spot, the material of the cathode 11 instantly evaporates, and at the same time becomes the metal ions 17 and jumps out into the vacuum. On the other hand, when a bias voltage is applied to the object to be coated 12, the metal ions 17 are accelerated and adhere to the surface of the object to be coated 12 together with the reaction gas particles 18, and a dense film is formed.

In the present invention, in the above arc ion plating apparatus, Cr metal is used as the material of the cathode 11 and N ₂ gas and O ₂ gas are used as the process gas, so that the object 12 to be coated is The piston ring can be coated with a hard coating of [O] in CrN.

The concentration of oxygen [O] can be controlled by controlling the oxygen partial pressure during ion plating. If you increase the oxygen partial pressure,
The concentration of [O] increases.

The film hardness can be controlled by controlling the oxygen partial pressure and bias voltage during ion plating. The hardness increases with increasing oxygen partial pressure (see Table 1). Further, when the bias voltage is increased, the hardness increases (see Table 2).

[0015]

[0016]

In order to evaluate the film toughness of the hard film 2, a film toughness evaluation test was conducted using a van der Horst friction tester. The outline of the test performed using the Van der Horst friction tester will be described with reference to FIG.

The piston ring 1 is arranged along the axis of the rotor 20 at the upper end of the outer peripheral surface 21 of a rotor (cast iron material: JIS FC250) 20 which rotates about a horizontal axis, and the load P is applied to the piston ring 1. It is operated and pressed onto the outer peripheral surface 21 of the rotor 20. In this state, piston ring 1
The rotor 20 is rotated while supplying the lubricating oil to the contact portion between the rotor 20 and the rotor 20.

When the sliding speed of the rotor 20 was varied, the sliding speed when a crack was generated in the hard coating 2 of the piston ring 1 was measured. The measurement was performed on eight types of piston rings having different [O] contents in the coating. The hard coating of the piston ring used for this measurement has a thickness of 50 μm and a surface roughness of 0.6 μm Rz.
Met.

The measurement of [O] in the CrN coating is mainly E
Performed by PMA and also confirmed by ESCA.

The test conditions are as follows. Lubricating oil: Nisseki High Diesel S3 10W Engine oil Load (P): 5 lbs Sliding speed: Varies in the range of 0 to 7 m / s Temperature: Room temperature

Table 3 shows the test results, and FIG. 4 shows a graphical representation thereof.

In the above, when the content of [O] in the coating is 4.4%, 8.5%, 10.4% and 15.7%, cracks occur at a sliding speed of 7 m / s. I didn't.

As shown in the test results of FIG. 4, C
It can be seen that the solid solution of [O] in rN improves the film toughness during sliding.

In order to ensure sufficient toughness, the hard coating in the present invention has a content of [O] dissolved in CrN of 3% by weight or more. And, when the content of [O] is 23% by weight, as shown in FIG. 5, a diffraction peak of Cr ₂ O ₃ other than CrN is observed by X-ray diffraction (tube: Cu), Since the film toughness deteriorates, the upper limit was made 20% by weight. FIG. 6 is an X-ray diffraction (tube: Cu) when the content of [O] is 10% by weight, and the diffraction peak of Cr ₂ O ₃ does not appear. CrN is a NaCl type crystal structure,
Cr ₂ O ₃ has an orthorhombic crystal structure.

The hardness of the hard film is not dense is coating is less than H _V 1600, contains defects such as pits, H _V 2
If it exceeds 200, edge peeling is likely to occur during the manufacturing process, so the hardness of the hard coating is set to a range of 1600 to 2200 in terms of Vickers hardness.

Next, in order to evaluate the seizure resistance of the hard coating, a seizure resistance evaluation test of the coating was conducted using a high surface pressure seizure tester. The outline of the test performed using the high surface pressure seizure tester will be described with reference to FIG.

The stator 30 is provided with a circular recess on the surface on the side of the rotor 31 which will be described later, and the disk 32 is placed in this recess.
(Cast iron material: JIS FC250) is fixed. The disk 32 projects toward the rotor 31 side, and
The side surface is a vertical flat surface. An oil hole 33 is formed in the center of the disk 32 in the axial direction of the stator 30, and an elongated oil hole 34 communicating with the oil hole 33 is formed obliquely in the stator 30. These oil holes 33,
Through 34, lubricating oil is supplied to a contact portion between the disk 32 of the stator 30 and a pin 35 described later.

The rotor 31 rotates about a horizontal axis, and a circular recess is formed on the surface on the side of the stator 30, and a disk-shaped pin holder 36 is concentrically fixed to the rotor 31 in this recess. On the surface of the pin holder 36 on the stator 30 side, four recesses are formed at equal intervals on the same circle, and pins 35 (8 mmφ) as test pieces are inserted and fixed in these recesses, respectively. There is. Each pin 35 horizontally projects from the surface of the pin holder 36 toward the stator 30.

Various surface treatment films 37 are formed on the protruding end faces of the pins 35, and the end faces are in contact with the surface of the disk 32 of the stator 30.

Therefore, the load P is applied to the stator 30 to press the disk 32 against the pin 35, and the rotor 31 is rotated while supplying the lubricating oil to the contact portion between the pin 35 and the disk 32 through the oil holes 33 and 34.

By keeping the sliding speed of the rotor 31 constant,
When the load P was changed, the seizure load when the pin 35 seized was measured. The measurement is a Cr plating film,
The present invention is provided with a pin as a comparative material having a nitride film of stainless steel, a CrN film in which oxygen [O] is not dissolved in the film, and a CrN film in which oxygen [O] is dissolved in the film. A seizure test was carried out on the pins and the test conditions described below.

The test conditions are as follows. Lubricating oil: Nisseki High Diesel S3 10W Engine oil Oil temperature 80 ° C Load (P): Stepping up from initial 20kgf by 10kgf at 3 minute intervals Sliding speed: 8m / s const Temperature: Room temperature

As shown in the test results of FIG. 8, C
It can be seen that the CrN film has better seizure resistance than the r-plated film and the nitride film. Further, it can be seen that in the CrN coating, the present invention having [O] as a solid solution in the coating is superior in seizure resistance to the coating having no [O] as a solid solution.

FIG. 9A is a vertical sectional view showing a part of a piston ring which is another embodiment of the present invention. The piston ring 1 in this embodiment has a hard coating 2 on its outer peripheral surface and upper and lower surfaces by arc ion plating. The hard coating 2 is a crystal structure of CrN in which oxygen [O] is dissolved in a proportion of 3 to 20% by weight, and has a Vickers hardness of 1600 to 2200. The film thickness of the hard coating 2 is preferably 10 μm to 70 μm.

FIG. 9B is a vertical sectional view showing a part of a piston ring which is still another embodiment of the present invention.
The piston ring 1 in this embodiment has an outer peripheral surface, upper and lower surfaces, and an inner peripheral surface coated with a hard coating 2 by arc ion plating. Hard coating 2 is Cr
Oxygen [O] is dissolved in the crystal structure of N at a ratio of 3 to 20% by weight, and has a Vickers hardness of 1600 to 2
It is in the range of 200. The film thickness of the hard coating 2 is 10 μm to 7
0 μm is preferred.

In the above embodiment, an example in which the piston ring is coated with a hard coating is shown. However, the hard coating is not limited to coating the piston ring, but other sliding members such as a tappet which is a valve train component of an internal combustion engine. It is effective to cover at least the sliding surface of a cam or cam.

[0038]

As described above, the hard coating material of the present invention is excellent in wear resistance, seizure resistance and toughness. Therefore, by coating the sliding member such as the piston ring with this hard coating material, sufficient durability can be provided even under severe conditions.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a part of a piston ring according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining the configuration of an arc ion plating device.

FIG. 3A is a partial cross-sectional front view for explaining the outline of the Van der Horst friction test, and FIG. 3B is a side view of the same.

FIG. 4 is a graph showing the results of tests conducted using a Van der Horst friction tester.

FIG. 5 is a diagram showing an X-ray diffraction result of a hard coating in which [O] is solid-dissolved in CrN at a ratio of 23% by weight.

FIG. 6 is a diagram showing an X-ray diffraction result of a hard coating in which [O] is solid-dissolved in CrN at a ratio of 10% by weight.

FIG. 7 is a vertical sectional view showing a high surface pressure seizure tester.

FIG. 8 is a graph showing the results of tests conducted using a high surface pressure seizure tester.

9 (a) and 9 (b) are vertical cross-sectional views each showing a part of a piston ring according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piston ring 2 Hard film 10 Vacuum chamber 11 Cathode 12 Object to be coated 13 Arc supply source 14 Bias voltage supply source 15 Gas inlet 16 Exhaust outlet 17 Metal ion 18 Reactive gas particle 20 Rotor 21 Rotor outer peripheral surface 30 Stator 31 Rotor 32 Disc 33 , 34 Oil hole 35 pin 36 Pin holder 37 Surface treatment film

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Shoji Tanaka 1-9-9 Yaesu, Chuo-ku, Tokyo Teikoku Piston Ring Co., Ltd. (72) Hiroto Fukudome 1-9-9 Yaesu, Chuo-ku, Tokyo Empire Piston Ring Co., Ltd. (72) Inventor, Hiroshi Tamagaki 2-3-1, Niihama, Arai-cho, Takasago, Hyogo Prefecture Kobe Steel Works, Takasago Works

Claims (6)

[Claims] 1. A crystalline structure of CrN contains [O] in a proportion of 3 to 20% by weight, and has a Vickers hardness of 16.
Hard coating material characterized by being in the range of 0 to 2200. 2. A sliding member, wherein at least a sliding surface is coated with a hard film made of the hard coating material according to claim 1. 3. The sliding member according to claim 2, wherein the member coated with the hard coating is a piston ring, and the surface on which the hard coating is formed is an outer peripheral surface. 4. The sliding member according to claim 2, wherein the member coated with the hard coating is a piston ring, and the surfaces coated with the hard coating are an outer peripheral surface and upper and lower surfaces. 5. The member coated with the hard coating is a piston ring, and the surface coated with the hard coating is the outer peripheral surface, the upper and lower surfaces, and the inner peripheral surface.
The sliding member described. 6. A method of manufacturing a sliding member, wherein at least the sliding surface is coated with the hard coating material according to claim 1 by ion plating.