JPH0681952A - Sliding material and piston ring, and manufacture of sliding material - Google Patents

Abstract

PURPOSE:To improve the sliding characteristics, such as wear resistance, of a Cr-N-O film having excellent initial draping ability and dissolve a problem on security of performance in industrial production by a method wherein comparatively low-cost Cr is main component and a color tone difference from a ground metal is increased. CONSTITUTION:A sliding material and a piston ring are characterized in such a way that a basic substrate is covered with a Cr-N-O film formed of chrome, nitrogen, and oxygen and having Vickers hardness of 1000-2000.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding material having a hard coating on a sliding portion and a method of manufacturing the sliding material.
The present invention relates to a sliding material used in sliding parts of various mechanical parts such as valve operating parts and a manufacturing method thereof. Due to higher rotation and higher output of these various devices, sliding parts such as machine parts are expected to have improved sliding characteristics such as wear resistance and seizure resistance under increasingly severe conditions. It is in response to such a request.

Further, the present invention relates to a piston ring, more specifically, a piston ring for an internal combustion engine coated with an ion plating film having improved wear resistance, seizure resistance and initial familiarity of a sliding surface. It is about.

[0003]

2. Description of the Related Art Conventionally, as a measure for improving sliding characteristics of iron-based sliding materials, surface treatment such as improvement of wear resistance by hard chrome plating and improvement of seizure resistance by nitriding or molybdenum spraying can be mentioned. However, these methods cannot obtain sufficient sliding properties as a sliding material, and recently physical vapor deposition (PVD) method or chemical vapor deposition (CV) method has been used.
Cr) -N system, Ti, which is chemically relatively stable by the method D)
A method for producing an N-based hard coating has been studied.

However, since the Cr-N-based coating has a relatively low hardness, it is apt to be worn, and sufficient sliding characteristics have not yet been obtained. Further, a Ti-N-based coating has been proposed as a coating having high coating hardness and excellent sliding characteristics.
This Ti-N-based coating has a track record of use as a cutting tool, but when used as a sliding member such as a machine part, it has a drawback that the coating hardness is too high and the mating material is abraded.

Further, the surface of the mating material, which has become rough due to abrasion with the Ti-N-based coating, abrasively wears the Ti-N-based coating, the sliding condition between the two deteriorates, and finally seizure occurs. It may happen. Further, since the hardness of the coating is too high, there is a drawback in that the "initial familiarity" with the mating material in contact with the coating is poor. The term "initial familiarity" used here means that the contact surface pressure is reduced due to minute and smooth wear of the sliding contact surface on the surface of the sliding member within a short period of time after the start of sliding, causing the lubricating oil film to run out. This is to prevent the occurrence of abrasion and seizure by making it difficult to cause. Since the Ti-N-based coating has poor initial familiarity, it tends to cause wear and seizure at the initial stage of sliding.

In addition to such problems in sliding characteristics,
The Cr-N type and Ti-N type coatings have manufacturing problems.
Generally, after coating a hard thin film, it is necessary to smooth the sliding surface of the film by polishing etc. so as to improve initial running-in and prevent excessive wear of the mating material, but the film hardness is high. Therefore, smoothing is difficult. Therefore, this polishing process takes a long time, does not result in a uniform finishing allowance, the film thickness becomes non-uniform, and the film is partially lost, resulting in a high rate of defective products.

Further, the Cr-N-based coating is silver or silver-white, and the Ti-N-based coating is gold or light yellow, and there is little difference in color tone from the metallic color of the base of the sliding member. Moreover, it has not been possible to automate it with an image analysis device or the like as a means for detecting a portion where the film is lost by the above-mentioned polishing. For this reason, it is necessary to use a method of enlarging with a microscope and inspecting with the naked eye, which is a big problem in terms of performance assurance.

The piston ring mainly seals the combustion chamber of the internal combustion engine, controls the film thickness of the lubricating oil film formed on the surface of the cylinder liner, and transfers the heat of the piston heated by the combustion of fuel to the cylinder liner. It works by transmitting and cooling. In order to perform such a function, the piston ring itself must overhang and adhere to the cylinder liner by its own tension, so that a large surface pressure is inevitably generated on the sliding surface, and therefore wear and wear. Sliding due to exposure to seizure. In addition, the hard combustion products generated during the combustion process reach the sliding surface between the piston ring and the cylinder liner, causing abrasive wear, and the sulfur and nitrogen components contained in gasoline are oxidized, and nitric acid and sulfuric acid are added. Therefore, the piston ring is mixed with the engine oil and promotes corrosive wear, and therefore the piston ring is exposed to a situation in which wear and seizure are likely to occur and slides.

In order to solve the problems of wear and seizure caused by the above sliding conditions, the piston ring has its sliding surface subjected to some surface treatment. Typical surface treatment methods that have been conventionally performed include improvement of wear resistance by hard chromium plating and improvement of seizure resistance by nitriding or molybdenum spraying. However, since the sliding characteristics of the piston rings treated by these methods are not sufficient for the current required level, the chemical comparison between the Cr-N system and the Ti-N system was recently conducted by the ion plating method. It has been considered to apply a chemically stable compound to the piston ring as a hard coating.

However, since the Cr-N type coating has a relatively low hardness, it is apt to be worn and the sliding characteristics have not yet been obtained. Further, a Ti—N-based ion plating film has been proposed as a film having high film hardness and excellent sliding characteristics (see Japanese Patent Publication No. 4-19412).

[0011]

SUMMARY OF THE INVENTION In view of the above problems, the present invention relates to a sliding material containing a relatively inexpensive Cr as a main component and a Cr--N--O system coating excellent in initial conformability. This was conducted for the purpose of development.In particular, by improving the sliding characteristics such as wear resistance and seizure resistance of the coating, and increasing the color difference with the base metal, performance assurance in industrial production The purpose is to solve the problem.

Similarly, in view of the above problems, the present invention develops a piston ring for an internal combustion engine, which is composed of a relatively inexpensive Cr as a main component and which is coated with a Cr—N—O type coating excellent in initial conformability. The purpose of this study is to improve the sliding characteristics such as wear resistance and seizure resistance of the coating, and to increase the color difference with the underlying metal to improve the performance assurance in industrial production. The purpose is to solve the problem.

[0013]

The present invention has excellent sliding characteristics such as abrasion resistance and seizure resistance, good initial familiarity, and a large color tone difference with a base metal, in sliding parts of machine parts. The above problem is solved by providing a film. That is, the sliding material according to the present invention has
Consisting of chromium, nitrogen and oxygen, with a Vickers hardness of 1
It is characterized in that a film of 000 or more and 2000 or less is formed.

Further, according to the present invention, at least the sliding surface of the piston ring which slides on the cylinder liner has excellent sliding characteristics such as wear resistance and seizure resistance, good initial familiarity, and a color tone difference from the base metal. The above problem is solved by providing a large coating film. That is, the piston ring for an internal combustion engine according to the present invention is made of chromium, nitrogen and oxygen at least on the outer peripheral sliding surface with the cylinder liner, and has a Vickers hardness of 1000 or more and 200 or more.
It is characterized in that an ion plating film having a thickness of 0 or less and a thickness of 1 to 50 μm is formed.

According to the present invention, ion plating,
The sliding material can be produced by bringing the vapor of chromium and a gas phase of a mixture of nitrogen gas and oxygen gas or a gas containing at least nitrogen and oxygen into a substrate by a PVD method such as vacuum deposition or sputtering. . Cathode ion plating is preferable as the ion plating, but the ion plating is not limited to this, and various systems such as those illustrated on page 903 of the revised 5th edition metallurgical handbook can be used.

The base material on which the coating is applied is preferably an iron-based material, but a titanium-based material, an aluminum-based material or the like can also be used. Further, the mating material of the sliding material may be made of various materials such as iron-based materials and aluminum-based materials. If the thickness of the ion plating film formed on the sliding surface of the piston ring is less than 1 μm, it has no effect.
Even if it exceeds 50 μm, there is no particular improvement in performance.
The range is 50 μm.

[0017]

Function Chromium forms a stable hard substance with nitrogen and oxygen. In particular, nitrogen significantly increases the hardness of chromium. If the amount is too small or too large, the hardness of the coating decreases and the wear resistance of the coating decreases. Therefore, it is necessary to determine the nitrogen content so that the Vickers hardness does not become less than 1000. When oxygen coexists with nitrogen, it enhances the hardness of the film, improves the sliding characteristics, and makes the film color dark (non-metallic).
Even if the amount of oxygen is small, it is effective for improving the sliding characteristics, but if it is too small, the effect of changing the color tone is not sufficiently exerted. Therefore, it is necessary to add oxygen so that the change in the color tone can be detected. On the other hand, when the amount of oxygen is too large, the hardness of the coating exceeds Vickers hardness of 2000, the wear of the mating material increases, so the amount of nitrogen added needs to be less than this hardness. The above-mentioned ratio of chromium, nitrogen and oxygen is atomic%
The ratio of Cr: N: O = 1: 0.9-0.1: 0.1-1.
It is preferably in the range of 2.

In order to form the ion plating film, chromium and other components must be gasified from another source. Nitrogen and oxygen may be supplied as separate gases or may be supplied as compounds such as NO ₂ and NO.

Hereinafter, the effect of introducing oxygen will be described in more detail with reference to a Cr-NO system ion plating film.

Table 1 shows the Cr produced by the method of Example.
An example of a -N-based or Cr-NO-based coating is shown. C
The atomic% ratio of r, N and O is the ratio in the film,
Determined by CA analysis. Surface roughness and deposition rate (R
Dep) was about the same regardless of the oxygen atomic% ratio. The coating hardness tended to increase as the oxygen atomic percentage increased. The color tone of the film is oxygen atom%
The black color became darker as the ratio increased. Other properties were not related to the atomic percentage of oxygen. Table 1 Gas ratio Surface roughness μm Film thickness Rdep Film hardness Color NoCr: N: O Ra Rmax Rz μm μm / min HmV 1: 0.5: 0.0 0.07 2.13 1.48 2.28 0.18 1320 Silver 1: 0.5: 0.5 0.09 1.66 1.20 2.24 0.17 1740 Black Gray 1: 0.1: 1.2 0.11 2.02 1.24 2.75 0.21 1860 Black

For these coatings, 200 to 700
The heat treatment was performed in air at a temperature of ° C for 1 hour. The relationship between the heat treatment temperature and the film hardness is shown in FIG. Both Cr-N-based coating and Cr-N-O-based coating are 200 ° C
As-de without heat treatment by performing heat treatment in
The film hardness was improved compared to the po film. Furthermore, the hardness of the film was hardly decreased at temperatures up to 500 ° C. However, the Cr-N-based coating showed a decrease in coating hardness of about 50% between the heat treatment temperatures of 500 and 700 ° C. On the other hand, Cr-N-O having an oxygen atom% ratio of 1.2
The decrease in film hardness of the system-based film is about 25%.
The Cr-N-O-based coating has a high coating hardness even at 0 ° C. Conventionally, the Vickers hardness of a Cr-N ion plating film was said to be about 1500, but even after heat treatment at 700 ° C by introducing oxygen, a hardness comparable to that of a Cr-N ion plating film was obtained. Was given. Therefore, it was found that the Cr-N-O type ion plating film is a sliding material capable of sufficiently preventing the deterioration of the sliding characteristics due to the temperature rise of the sliding surface. Hereinafter, the present invention will be described in detail with reference to examples.

[0022]

【Example】

Example 1 A mirror-finished high-chromium steel (JIS SUJ2) substrate was previously ultrasonically cleaned in a fluorocarbon solution, and the sliding surface with the cylinder liner was subjected to an arc ion plating method in the procedure described below. A Cr-NO hard coating was formed.

After ultrasonically cleaning the substrate, the substrate was mounted in a vacuum container (chamber) of an ion plating apparatus, and then vacuumed until the pressure in the chamber reached 1.3 × 10 ⁻³ Pa (pascal). . From the time when this degree of vacuum is achieved, the substrate is heated to 300 to 600 ° C. by the heater incorporated in the chamber to release the gas component adhering to or adsorbing on the substrate surface, and then 200
Cooled to ° C. When the pressure in the chamber became 4 × 10 ⁻³ Pa or less, arc discharge was generated on the surface of the Cr target serving as the cathode, and most of the Cr was ejected from the target surface in the ionized state. . At this time, a bias voltage of -700 to -1000 V was applied to the jig to which the substrate was attached, the ionized Cr ejected from the target was attracted to the surfaces of the substrate and the jig, and these ions were further absorbed. It collides with the surface to be processed at high speed.

The surface activation treatment was carried out by so-called sputter cleaning, in which oxides and the like on the surface to be treated were scraped by the collision of the ionized metal. Further, when a small amount of nitrogen gas is introduced into the chamber simultaneously with the occurrence of arc discharge, a part of ionized Cr is combined with the nitrogen gas and deposited as a Cr-N-based film on the surface of the substrate. Then, the flow rate of nitrogen gas is further increased, a predetermined amount of oxygen gas is introduced, and the pressure is set to about 1.3 Pa.
Was applied to form a Cr—N—O type hard coating on the surface of the substrate. After forming a predetermined film thickness, the temperature inside the chamber was cooled to 150 ° C. or lower, and then the film-coated substrate was taken out of the chamber. For comparison, a Cr—N-based coating that does not introduce oxygen, which has been conventionally used, was also prepared under the same conditions.

These films were subjected to a scuff test using a gray cast iron (FC25) as a mating material with a pin-on-disc type friction tester to evaluate the seizure resistance by baking load. The scuff test conditions were as follows. Lubrication method: Motor oil # 30, oil temperature 80 ° C, oil amount 4
cc / sec Friction speed: 8 m / sec Contact load: Increased from 2 MPa in the initial stage in steps of 1 MPa,
Friction time until baking: Holds for 180 seconds at each load

The results obtained by the above method are shown in FIG. The Cr-N based film in which oxygen was not introduced showed a scuff value of about 22 MPa, but the oxygen atomic% ratio was 0.5%.
The r-N-O-based film has a pressure of 30 MPa and an oxygen atom% ratio of 1.
The Cr—N—O based coating of No. 2 showed a scuff value of 36 MPa, and it was found that the introduction of oxygen improves the seizure resistance. Further, a wear test was conducted by using a pin-drum type wear tester and using gray cast iron (FC25) for the drum. The wear test conditions were as follows. Lubrication method: Motor oil # 30, oil temperature 80 ° C, oil amount 8
cc / sec Drum rotation speed: 5 m / sec Contact load: 1.5 MPa Test time: 30 ksec

The amount of wear of the pin coated with the coating and the amount of wear of the drum are shown together in FIG. Here, the wear amount of the pin was obtained from the width of the worn contact surface in the drum rotation direction, and the wear amount of the drum was obtained from the wear depth of the drum. Focusing on the amount of wear of the drum, the amount of wear was almost the same in the Cr—N—O based coating as compared with the Cr—N based coating. On the other hand, focusing on the wear amount of the pin, the wear amount decreased as the oxygen atomic% ratio was increased.

From the results of the above scuffing test and abrasion test, the Cr-N-O based film in which oxygen is introduced is superior to the Cr-N based film in seizure resistance, good initial familiarity, and film hardness. Since it is high, it was found that the wear of the coating itself was suppressed. Further, the color tone of these films was silver in the Cr-N-based film in which oxygen was not introduced, whereas it was black gray and oxygen in the Cr-N-O-based film having an oxygen atomic ratio of 0.5. The Cr-N-O based film having an atomic% ratio of 1.2 was black, and became blacker as the oxygen atomic% ratio increased. The Cr-N-O type coating causes a large difference in color tone between the underlying metal and the coating.

Example 2 Piston ring made of stainless steel (JIS standard SUS440C) Nominal diameter × width × thickness = 86 mm × 2 mm
A non-treated material having a size of 3 mm was used to perform a Cr-NO hard coating by the arc ion plating method in the same manner as in Example 1. In addition, the characteristics of the film were evaluated by the same test method as in the examples.

FIG. 4 shows seizure resistance and FIG. 5 shows wear resistance. These results were similar to those in FIGS.

[0031]

As described above, by coating the sliding surface with the Cr--N--O type coating, the conventional Cr treatment has been performed.
Initial familiarity is better than coating with -N-based film,
A sliding material having excellent wear resistance and seizure resistance can be obtained.
Further, since the color tone difference between the coating and the base metal is large, it is possible to automatically inspect the coating after polishing, and a sliding material having a superior performance guarantee and economical advantages can be obtained.

Further, by coating at least the outer peripheral sliding surface of the piston ring with a Cr--N--O type coating, the sliding characteristics such as wear resistance and seizure resistance are superior to those of the conventional Cr--N type coating. In addition, a piston ring with good initial familiarity can be obtained without wearing the cylinder liner. Further, the piston ring coated with the Cr—N—O type coating has a small rate of decrease in coating hardness in the high temperature region, and can prevent deterioration of sliding characteristics due to temperature rise of the sliding surface. Furthermore, since the color tone difference between the coating and the base metal is large, automatic inspection of the coating is possible, and a piston ring with a superior performance guarantee can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a result of a scuff test in Example 1.

FIG. 2 is a diagram showing a result of a wear test of Example 1.

FIG. 3 is a diagram showing a relationship between a heat treatment temperature and a film hardness of a Cr—N—O based film produced by cathodic arc plasma type ion plating.

FIG. 4 is a diagram showing a result of a scuff test in Example 1.

5 is a diagram showing the results of an abrasion test of Example 1. FIG.

Claims (5)

[Claims] 1. A Cr-N composed of chromium, nitrogen and oxygen and having a Vickers hardness of 1000 or more and 2000 or less.
A sliding material having an -O-based coating on a substrate. 2. The atomic% ratio of chromium, nitrogen and oxygen is Cr: N: O = 1: 0.9 to 0.1: 0.1 to 1.
The sliding material according to claim 1, wherein the sliding material has a range of 2. 3. A Vickers hardness of 1000 or more 2 made of chromium, nitrogen and oxygen on at least the outer peripheral sliding surface.
Ion plating film of 000 or less is 1 to 50
A piston ring having a thickness of μm. 4. The atomic% ratio of chromium, nitrogen and oxygen is Cr: N: O = 1: 0.9 to 0.1: 0.1 to 1.
The piston ring according to claim 3, wherein the piston ring has a range of 2. 5. The slide according to claim 1 or 2, wherein a vapor phase of chromium and a gas phase in which nitrogen gas and oxygen gas or a gas containing at least nitrogen and oxygen are mixed are brought into contact with the substrate by the PVD method. Method of manufacturing moving materials.