JPH02134468A - Piston ring - Google Patents

Abstract

PURPOSE:To enhance anti-wear property and seizure resistance and reduce the attacking property for a mating material by forming a molybdenum nitride film at least on the sliding peripheral surfaces of a piston ring. CONSTITUTION:A nitride layer is formed at least on the sliding peripheral surface of a piston ring, and a molybdenum nitride (MoXNY) layer is formed by ion plating process over the layer which has gotten rid of the facial oxide layer and a white layer, or the surface after having undergone chromium plating. This molybdenum nitride film has an anti-wear property equal to a TiC film and TiN film, while its seizure resistance is more excellent than them, and its attacking property for the mating material is low even though its own surface roughness remains large. This should prolong the life of the piston ring.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piston ring for an internal combustion engine, which has a coating formed thereon that has excellent wear resistance and seizure resistance, and is less likely to attack opponents.

[Conventional technology]

Conventionally, hard chrome plating has been mainly used as a surface treatment for the sliding outer peripheral surface of piston rings. Piston rings coated with hard chrome plating have long been the mainstream surface treatment for piston rings because they have excellent wear resistance and cause less wear on the mating cylinder.

However, as engines have become more powerful and rotated in recent years, the environment to which piston rings are exposed has become increasingly harsh, and conventional hard chrome plating is no longer able to cope with this environment. There is a growing demand for piston rings with excellent wear resistance and seizure resistance.

In order to cope with this situation, Fe-Cr based plasma sprayed piston rings, stainless steel nitrided piston rings, ceramic powder composite plated piston rings, etc. have been developed and are used in some engines.

[Problem to be solved by the invention]

According to these technologies, in terms of wear resistance and seizure resistance,
Although it is much improved compared to hard chrome plating using conventional technology, the following problems have been discovered.

Fe-Cr based plasma sprayed piston rings have excellent wear resistance and seizure resistance, but on the other hand, they have the disadvantage of causing a lot of wear on the mating cylinder material, and when exposed to a corrosive atmosphere, the sprayed layer deteriorates to the base material. The weak point is that it is easier to give up on publication.

Although ceramic powder composite plating piston rings have excellent seizure resistance, they have problems with the strength of the matrix, and the plating tends to crack and peel during engine operation.

Stainless steel nitrided piston rings have excellent wear resistance and less wear on the mating material, but they have the disadvantage that they cannot be used in engines with high seizure resistance. In order to deal with this situation, a technology has been disclosed for a stainless steel nitrided piston ring in which the outer peripheral sliding surface is further coated with a TiN film having a predetermined thickness by ion plating. However, it has been found that the TiN film has poor compatibility with the mating material, and when the surface roughness is greater than 0.6 μm, the aggressiveness of the TiN film to the mating material increases rapidly.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a piston ring that has sufficient wear resistance and seizure resistance, and is less likely to attack mating materials.

[Means to solve the problem]

The piston ring of the present invention is characterized in that a molybdenum nitride (MoxNv) film is formed on at least the sliding outer peripheral surface. It is preferable to form a nitrided layer on at least the outer circumferential surface of the sliding surface, and to form a molybdenum nitride film on the nitrided layer from which the surface oxidized layer and white layer have been removed. It is also preferable that at least the sliding outer circumferential surface is plated with chromium, and a molybdenum nitride film is formed on the chromium plating.

The molybdenum nitride film is preferably coated by ion plating.

When coating the piston ring surface with the coating of the present invention, the treatment is preferably carried out at a temperature below 600°C, preferably below 350°C. In Figure 1, which shows a characteristic curve diagram showing the change in hardness due to time retention, the nitrided layer is martensitic 17c. The chromium plating layer is chromium plating applied to the outer periphery of the 5WO3C-V piston ring base material.

From FIG. 1, the nitrided layer shows almost no decrease in hardness when heated to 500°C or lower, and the chromium plating layer shows almost no decrease in hardness when heated to 350°C or lower.

[Effect]

A molybdenum nitride film has wear resistance equivalent to that of a TiC film and a TiN film, and has better seizure resistance than a TiC film and a TiN film. Furthermore, even if its own surface roughness is large, it has a characteristic of being low in its ability to attack other materials.

The reason why molybdenum nitride is coated by ion plating is that it must be treated at a temperature that prevents the piston ring base material from softening and does not impair the wear resistance of the base material, and also to prevent deformation. This is because it is desirable that the processing temperature be lower.

[Example-1] Figure 2 shows an outline of the reciprocating friction testing machine used in the test.

In Figure 2, the upper test piece l corresponding to the piston ring
is held by the upper test piece fixing block 2, and a downward load is applied from above by a hydraulic cylinder 3. On the other hand, a lower test piece 4, which is a mating member corresponding to a cylinder, is held by a movable block 5 and is reciprocated in the direction of the arrow by a crank mechanism 6 as shown. Further, 7 is a load cell. The friction tester shown in FIG. 2 is well known, and its configuration itself is not directly related to the present invention, so a detailed explanation will be omitted.

The wear of the upper test piece 1 is calculated by measuring the shape 8 before the test and the shape 9 after the test of the upper test piece 1 and measuring the difference, as shown in FIG. 3(A). The amount of wear of the lower test piece 4 was determined by measuring the amounts of dents at three separate locations a, b, and c, as shown in FIG. 3(B), and is expressed as the average value.

The test conditions are as follows.

1. Test sample A, lower test piece 4 Cast iron for cylinder block (FC25
Equivalent material) flat plate (dimensions: length 70mm, width 17mm, rg
- Puff polish the test surface of 14mm) and reduce the surface roughness to 0.1
Less than μm. Note that the hardness is HIB90.

B, upper test piece l: piston ring rod (dimensions: diameter 8 m
m, length 23mm) with a spherical finish of 18mmR, however, this steel bar is martensitic 17C.
A sample was prepared using this steel rod as a base material and subjected to the following surface treatment.

Sample 1. (Prior art) - Hard chromium plating is applied to the end face of one of the upper test pieces to a thickness of 80 μm. The plating hardness is Hv900, and the plate is finished by puff polishing after being processed into a spherical surface of 18 mm radius.

Trial 02. (Prior art) - Upper test piece 1 end face 18mm
After R spherical machining, gas nitriding treatment was performed, and the oxide layer and white layer on the surface were removed by spherical machining of 13 mmH, followed by puff polishing. Note that the thickness of the nitrided layer is 90 μm, and the hardness is HVI 200.

Sample 3. (Prior art) - A high-chromium, high-carbon iron-based powder was plasma sprayed on the end face of the upper test piece, and the end face was processed into a spherical surface of 18 mm radius and then finished with puff polishing. The thickness of the sprayed layer is about 70 μm, and the hardness is Hv++ts+600.

Sample 4. (Prior art) - The end face of the upper test piece was processed into a spherical surface of 18 mmR, then subjected to gas nitriding treatment, the oxide layer and white layer on the surface were removed by spherical processing of 18 mmR, and TiN was coated by ion plating after puff polishing. The thickness of the nitrided layer is 90 μm and the hardness is Hv1200, and the hardness of the TiN film is Hv2200 and the thickness is 2 μm.

Sample 5. (Prior art) - Upper test piece L end face 18mm
After H spherical processing, gas nitriding treatment was performed, the oxide layer and white layer on the surface were removed by spherical processing of 13 mmH, and TiC was coated by ion plating after puff polishing.The thickness of the nitrided layer was 90 um. , the hardness is Hv1200, and the hardness of the Tic film is Hv2800, and the thickness is 2 μm.

Sample 6. (Present invention) - The end face of the upper test piece was processed into a spherical surface with a radius of 18 mm, gas nitriding was performed, the oxide layer and white layer on the surface were removed by spherical processing with a radius of 18 mm, and molybdenum nitride (Mo , N,) coating, the nitride layer has a thickness of 90 μm and a hardness of Hvl 200, and the molybdenum nitride film has a hardness of HVI 750 and a thickness of 3 μm.

2. Molybdenum nitride - ion plating film 1!
! How to send.

Equipment used: Ion plating v equipment Processing conditions: ■Vacuum power - I X 10-'Torr ■Heater heating ■Ion bomber - 15 minutes in Ar gas ■Vacuum power - I X 10-'Torr ■MO Melting (1) Introducing N and gas -- Evaporation 11 Furnace pressure 3 to 5 x 10-' Torr (2) Cooling (4) Bringing the vacuum chamber to atmospheric condition.

Take out the work.

3. Wear test conditions Test 2nd position: Reciprocating friction tester (see Figure 2) Test conditions:
Break-in 2 gf X 100cpm x 5m1n Main test 10Xgf ,
It exhibited wear resistance equivalent to that of the TiC film, and showed the least amount of wear on the mating material compared to conventional surface-treated films.

[Example-2] 1. Test sample A, lower test piece 4: A flat plate made of martensitic 17Cr stainless steel, which is the base material for piston rings, and the dimensions are as in Example-
It is the same as 1.

A sample was prepared using this flat plate as a base material and subjected to the following surface treatment. Note that the base material of the PVD-treated sample was adjusted to a predetermined surface roughness before treatment. For the others, the surface was treated and then adjusted to a predetermined surface roughness.

Sample 1. (Prior art) - 50 μm of hard chromium plating is applied to the surface of the lower test piece 4.

The plating hardness is HV900.

Sample 2. (Prior art) - After gas nitriding the lower test piece 4, the oxide layer and white layer on the surface were removed, and the surface roughness was adjusted to a predetermined level using emery paper. The thickness of the nitride layer is 7 (Jum) and the hardness is Hvl 220.

Sample 3. (Prior art) - After gas nitriding the lower test piece 4, the oxide layer and white layer on the surface were removed, the surface roughness was adjusted to a predetermined level with emery paper, and TiN was coated by ion blasting.

The thickness of the TiN film is 3 μm, and the hardness is It is Hv2480.

Sample 4. (Prior art) - After gas nitriding the lower test piece 4, the oxide layer and white layer on the surface were removed, the surface roughness was adjusted to a predetermined level with emery paper, and TiC was coated by ion blating.

The thickness of the TiC film is 3 μm, and the hardness is H, 2950.

Sample 5. (The present invention) - After gas nitriding the lower test piece 4, the oxide layer and white layer on the surface were removed, the surface roughness was adjusted to a predetermined level with emery paper, and a molybdenum nitride film was coated by ion blating, The thickness of the molybdenum nitride film is 3 μm and the hardness is Hvl 750.

B, Upper test piece 1: Cast iron material F which is the base material for cylinder litchi
A round bar with a diameter of 8 mm and a length of 23 mm is made from C25, and the end face is finished with a spherical surface of 18 mm radius and finished with puff polishing.

2. Method for producing molybdenum nitride-ion plating film.

Same as Example-1.

3. Wear test conditions Test equipment rt: Reciprocating friction tester (see Figure 2) Test conditions: (Unlubricated conditions) Main test 10Kgf XX100cp GF

Test results: As shown in Figures 5 and 6, TiN and '
``The wear of the iC film increases rapidly as the surface roughness increases.In contrast, the film of the present invention shows a gradual increase in wear even when the surface roughness increases, indicating good wear characteristics. There is.

[Example 3] Figures 7 and 8 show an outline of the bottle-disk type high surface pressure friction testing machine used for the seizure resistance test.

diameter 80 removably attached to stator 20
Lubricating oil is applied to the center of the mm-sized disc 21 (sliding partner member) from the back side through the oil filling hole 22. Further, the stator 20 is pressed against the rotor 23 at a predetermined pressure by a hydraulic system, so that a pressure P is applied thereto. A rotor 23 is arranged opposite to the stator 20, and the rotor 23
rotates at a predetermined speed depending on the drive position VT.

A sample holder 2 is provided on the end surface of the rotor 23 facing the disk 21.
4, and the sample holder 24 has four test pieces 2 having square sliding surfaces arranged at equal intervals on a concentric circle.
5 is attached, and the sliding surface slides against the disk (stator).

In such a device, the rotor 23 is rotated while a predetermined amount of oil is supplied to the sliding surface. The pressure applied to the stator 20 is increased stepwise at regular intervals, and +1tl1% generated by the sliding between the disk 21 and the test piece 25 is applied to the load cell 26 via the wire as a torque T. The change is read by the dynamic strain meter 27 and recorded by the recorder 28. When the seizure phenomenon occurs, the torque T increases rapidly. Therefore, the contact surface pressure acting on the sliding Oj contact surface when the torque T rapidly increases is defined as the seizure-generating surface pressure, and the quality of the seizure characteristics is determined based on the magnitude of this seizure-generating surface pressure.

The test conditions are as follows.

Sliding speed: 8mm/see Lubricating oil: SAE#30 motor oil Lubricating oil supply conditions: 300cc/min Lubricating oil temperature - 80°C Contact pressure: 10K every 3 minutes from 20Kg/cm
g/Cm”.

Mating sliding member (stator): Cast iron material FC25 Test sample: Sample 1. (Prior art) - 50 μm of hard chromium plating is applied to the surface of the test piece 25.

The plating hardness is Hv900.

Sample 2. (Prior art) - Test piece 25 was subjected to gas nitriding treatment, the oxide layer and white layer on the surface were removed, and the surface roughness was adjusted to a specified level with emery paper. The thickness of the nitrided layer was 70 μm% hardness. is Hvl 220.

Trial $43. (Prior art) - After gas nitriding the test piece 25, the oxide layer and white layer on the surface were removed, the surface roughness was adjusted to a predetermined level with emery paper, and TiN was coated by ion blasting.

The thickness of the TiN film is 3 μm, and the hardness is It is Hv2480.

Sample 4. (Present invention) - After gas nitriding the test piece 25, the oxide layer and white layer on the surface were removed, the surface roughness was adjusted to a predetermined level using emery paper, and a molybdenum nitride film was coated by ion blasting. The thickness of the molybdenum nitride film is 3 μm and the hardness is Hvl 750.

Example of manufacturing method of molybdenum nitride-ion plating film! is the same as

The test results are shown in Figure 9.

As shown in FIG. 9, the film of the present invention exhibited better seizure resistance than the surface-treated film of the prior art.

[Example 4] The outer peripheral sliding surface of the first pressure ring was subjected to the surface treatment shown below and subjected to an engine test. The material of the cylinder block is a material equivalent to FC25.

Sample 1. (Prior art) - Spring @ (SWO3C-V
) The outer peripheral sliding surface of the piston ring base material is plated with chrome.The thickness of the chrome plating is 150 IIm, and the hardness is Hv890.

Sample 2. (Prior technology) - Martensitic 17C "Stainless steel piston ring base material is subjected to gas nitriding treatment, and then the oxidized layer and white layer on the surface are removed. The thickness of the nitrided layer on the outer sliding surface is 90 μm. Yes, and the hardness is Hv1200.

Sample 3. (Prior art) - A piston ring base material made of martensitic 17Cr stainless steel is subjected to gas nitriding treatment, the oxide layer and white layer on the surface are removed, and TiN is coated by ion blating after puff polishing. The thickness of the nitrided layer on the moving surface is 90 μm, and the hardness is Hv1200. The thickness of the TiN film coated on the surface of this nitrided layer was 3 μm, and the hardness was ) Iv2200. (The present invention) - A piston ring base material made of martensitic 17cr stainless steel is subjected to gas nitriding treatment, the oxidized layer and white layer on the surface are removed, and a molybdenum nitride film is coated by ion blasting after puff polishing. The thickness of the nitrided layer on the outer peripheral sliding surface is 90 μm, and the hardness is HVI 200. The thickness of the molybdenum nitride film coated on the surface of this nitrided layer was 3 μm, and the hardness was Hv1700.

Sample 5. (The present invention) - Spring steel (SWO3C-ν) type piston ring base material whose outer peripheral sliding surface is plated with chromium, and the surface is coated with a molybdenum nitride film by ion blasting. The thickness of the chrome plating is 150 μm, and the hardness is HV890. The thickness of the molypun nitride film coated on the surface of this chromium plating is 3 μm, and the hardness is OVI700.

Sample 6. (The present invention) - A molybdenum nitride film is coated on the outer peripheral sliding surface of a martensitic 17cf stainless steel piston ring base material by ion plating, the thickness of this molybdenum nitride film is 3 pm, and the hardness is Hvl. It is 700.

The method for producing the molybdenum nitride-ion plating film was the same as in Example 1.

The surface roughness of the outer sliding surface of each sample 1 to 6 is all 0°8 μR.
It is z.

The above piston ring has a displacement of 2000cc.

Built into a water-cooled 6-cylinder 4-stroke gasoline engine,
A 10-hour bench test was conducted three times using leaded gasoline as fuel under the conditions of rotation speed 520 Qrpm, water temperature 110°C, oil temperature 130°C or higher, and full load. Table 1 shows the state of scuffing on the outer peripheral sliding surface of the piston ring and the state of scuffing on the inner peripheral surface of the cylinder after the test.

(Margins below) Table 1 ■: No scratches or scuffing at all, and the sliding surface is in good condition.

O: No scuffing occurred, but one or two sharp scratches were observed.

Δ: No scuffing occurred, but 3 or more and 10 or less sharp scratches were observed.

×: Scuffing occurred or 10 or more sharp scratches were observed.

As shown in Table 1, the most severe scuffing occurred on the piston ring outer sliding surface and the cylinder inner circumferential surface. It was a chrome-plated piston ring. Although no scuffing occurred on the surface of the TiN film of sample 3, many scratches occurred on the inner peripheral surface of the cylinder. Compared to these conventional products, the products of the present invention (Samples 4 to 6) exhibited good sliding characteristics, with no scuffing observed on the piston ring surface or the inner peripheral surface of the cylinder, and almost no scratches. .

〔Effect of the invention〕

As explained above, the piston ring of the present invention has the excellent effects of being excellent in wear resistance and seizure resistance, and having low attackability on mating materials.

[Brief explanation of the drawing]

Figure 1 is a diagram showing changes in hardness due to temperature of the nitrided layer and chromium plating layer, Figure 2 is an explanatory diagram of the reciprocating friction tester,
Figure 3 (A) is an explanatory diagram for calculating the wear amount of the upper test piece;
B) is an explanatory diagram of the wear it
2 shows the test results (Figure 5 shows the results without lubrication, Figure 6 shows the results with lubrication), Figures 7 and 8 are explanatory diagrams of the pin-disk type high surface pressure friction tester, FIG. 9 is a diagram showing the test results of Example 3. Patent applicant Teikoku Piston Ring Co., Ltd.

Claims (4)

[Claims] (1) A piston ring characterized in that a molybdenum nitride film is formed on at least the outer sliding surface. (2) A piston ring characterized in that a nitrided layer is formed on at least the sliding outer circumferential surface, and a molybdenum nitride film is formed on the layer obtained by removing the surface oxidized layer and white layer of the nitrided layer. (3) A piston ring characterized in that at least the sliding outer peripheral surface is chromium plated, and a molybdenum nitride film is formed on the chrome plating. (4) The method for manufacturing a piston ring according to claim 1, 2 or 3, wherein the molybdenum nitride film is coated by an ion plating method.