JPH0552262A - Piston ring - Google Patents

Abstract

PURPOSE:To provide a piston ring which possesses the superior seizure resistance and the superior initial fittingness at the same CONSTITUTION:A piston ring has a double structure layer consisting of a nitrified layer on the outer peripheral sliding surface and a composite dispersed plated layer which is formed on the nitrified layer and has a thickness of 0.5-20pmum. The composite dispered plated layer is made by dispersing the particles having a particle diameter of 0.3-1mum in 5-30% in area ratio, into a substrate made of the Co-Ni-P allay consisting of 2-10wt.% P, 10-40wt%. Ni, and 55-88 wt.% Co.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston ring for an internal combustion engine, and more particularly to a piston ring having excellent seizure resistance and good initial conformability with a cylinder.

[0002]

2. Description of the Related Art In recent years,
As the engine becomes smaller and lighter, and with higher performance such as higher output, the conditions required for piston rings are becoming more severe, and higher wear resistance, seizure resistance, initial familiarity, etc. are required. ing.

Hard chromium plating, which has been often used for surface treatment of piston rings for internal combustion engines, has a problem in wear resistance when a high lead fuel is used or when it is operated in a corrosive atmosphere. As an alternative, thermal spraying has come to be applied. However, although the thermal spray coating has excellent wear resistance, there are problems such as peeling and falling of the coating during operation, and abrasion of the mating material. Therefore, recently, a steel ring subjected to a nitriding treatment, which has excellent wear resistance, has been put into practical use.

However, while the nitrided layer is excellent in wear resistance, it is inferior in terms of seizure resistance to the hard chrome plated layer and the sprayed layer, and there are some cases where scuffing occurs. Therefore, the piston ring having a nitrided layer on the outer peripheral sliding surface has a problem in use under severe operating conditions.

As a piston ring that overcomes the above problems, Japanese Patent Laid-Open No. 12053/1991 discloses a piston ring in which a nitride layer is formed on the outer peripheral sliding surface and a composite dispersed plating layer is formed on the nitride layer. Is disclosed. In this piston ring, a composite dispersion plating layer in which hard particles or solid lubricant particles are dispersed in a matrix of nickel-based alloy containing cobalt and phosphorus is used. This piston ring not only has excellent wear resistance but also has improved seizure resistance, but when used in an internal combustion engine under severe conditions, seizure resistance and initial familiarity are not sufficient. It is difficult to say, and a piston ring having excellent seizure resistance and initial familiarity is desired.

Therefore, an object of the present invention is to provide a piston ring which is excellent in seizure resistance as well as in initial conformability.

[0007]

As a result of earnest research in view of the above problems, the present inventor has found that a nitride layer and cobalt-nickel-
In a piston ring having a double structure layer with a composite dispersion plating layer in which particles are dispersed in a matrix of phosphorus alloy, by using one having a specific metal composition ratio as the alloy matrix, excellent seizure resistance can be obtained. At the same time, we discovered that a piston ring with excellent initial familiarity can be obtained,
The present invention has been completed.

That is, the piston ring of the present invention has a double-layer structure comprising a nitride layer on at least the outer peripheral sliding surface thereof and a composite dispersion plating layer having a thickness of 0.5 to 20 μm formed on the nitride layer. In the piston ring having, the composite dispersed plating layer contains 2 to 10% by weight of phosphorus and 10 to 10% of nickel.
Characterized by a layer in which particles having a particle size of 0.3 to 10 μm are dispersed in an area ratio of 5 to 30% in a matrix of a cobalt-nickel-phosphorus alloy composed of 40% by weight and 55 to 88% by weight of cobalt. ..

The present invention is described in detail below. In the present invention, the nitride layer (first layer) is formed on the outer peripheral sliding surface of the piston ring.
Layer) and the cobalt-nickel-phosphorus alloy composite dispersed plating layer (second layer) are formed to have a double structure.

The substrate of the piston ring of the present invention is made of steel material, and is not particularly limited as long as it is a steel material suitable for obtaining a nitrided layer exhibiting good wear resistance. A particularly preferred example is C: 0.
It is a steel material containing 6 to 1.5% by weight and Cr: 12 to 19% by weight, or a chromium steel containing a small amount of Mo and / or V therein.

The first nitride layer can be obtained by nitriding with N ₂ gas. Preferably 550 to 590 ° C
Nitriding is performed in a N ₂ atmosphere at 1.0 to 1.1 atm for 3 to 10 hours. The preferred thickness of the nitrided layer is 80 to 130 μm. This nitride layer has a high hardness and a high wear resistance.

The nitrided layer has a high hardness, and therefore the piston ring subjected to the nitriding treatment shows good wear resistance, but it is inferior in seizure resistance and initial conformability.
A composite dispersed plating layer is formed as a second layer on the first layer.

The composite dispersed plating layer of the present invention is one in which particles are dispersed in a matrix of cobalt-nickel-phosphorus alloy.

Cobalt in the alloy matrix improves the heat resistance and corrosion resistance of the matrix as well as the crush fatigue strength of the coating. Also, under the operating conditions where the piston ring temperature exceeds 300 ° C such as in diesel engines, the cobalt on the surface is oxidized to form tricobalt tetroxide. As a result, an oxide layer having a low coefficient of friction suitable for sliding friction is formed. The amount of cobalt in the alloy matrix of this composite coating is
If it is less than 55% by weight, the above-mentioned effect cannot be remarkably obtained.
Since there is no significant change in the effect even if it exceeds the weight%, 55
~ 88% by weight. The preferred cobalt content is 60-80
% By weight.

Further, the inclusion of nickel in the alloy matrix improves the heat resistance, corrosion resistance and toughness of the matrix, and further enhances the strength of the film. If the amount of nickel is less than 10% by weight, the above effect cannot be remarkably obtained, and if it exceeds 40% by weight, the effect is not significantly changed. Therefore, the amount of nickel is 10-40% by weight. The preferable nickel content is 25 to 35% by weight.

Furthermore, the inclusion of phosphorus in the alloy matrix increases the hardness of the matrix and exhibits an excellent effect of abrasion resistance. If the amount of phosphorus is less than 2% by weight, the hardness does not increase,
It has little effect of improving wear resistance. On the other hand, if it exceeds 10% by weight, the hardness increases, but the plating layer becomes rather brittle and the impact strength becomes weak, and the adhesion of the plating layer also deteriorates. Therefore, the amount of phosphorus is 2 to 10% by weight. A preferable phosphorus content is 3 to 8% by weight.

By dispersing the particles in the alloy matrix, the wear resistance of the plating layer is improved. It is preferable to use hard particles and / or solid lubricant particles as the particles. The hard particles include metal carbides such as TiC, SiC and Cr ₃ C ₂ , metal nitrides such as TiN, Si ₃ N ₄ and Cr ₂ N,
Alternatively, a metal oxide such as Al ₂ O ₃ , TiO ₂ , or Cr ₂ O ₃ can be used. As the solid lubricant particles, molybdenum disulfide, tungsten disulfide, boron nitride, etc. can be used.

The amount of particles dispersed and the particle size are also related to the thickness of the plating to be formed, but if they are excessively large or large, the coating becomes brittle and the wear of the sliding mating material increases, which is not preferable. .. If the amount of dispersion is small or the particle size is small, the effect is small. Therefore, the amount of dispersed particles is in the range of 5 to 30% in area ratio, and the particle size is 0.3 to 10 μm. Preferably, the amount of dispersed particles is in the range of 10 to 20% in area ratio, and the particle size is 0.5 to 5.0 μm.

With respect to the thickness of the composite dispersed plating layer, if it is too thin, the composite dispersed plating layer will disappear before a sufficient initial running-in state is achieved, and the expected effect cannot be obtained. Thickness is required to be 0.5 μm or more. On the other hand, if the composite dispersed plating layer is too thick, peeling of the plating layer is likely to occur, and the outer peripheral wear increases until the good wear resistance of the nitrided layer is utilized, resulting in a ring abutment. The increase in the gap progresses early, and the phenomenon of deterioration of the airtightness of the piston ring occurs early. Therefore, the thickness of the plating layer should be 20 μm or less. Therefore, the thickness of the composite dispersed plating layer is 0.5 to 20 μm, preferably 5 to 10 μm.

[0020]

The present invention will be described in more detail by the following examples. Example 1 Alloy steel SUS440B (C: 0.75 to 0.95% by weight, Si: 1.0% or less, Mn: 1.0% or less, P: 0.04% or less, Ni: 0.60% or less,
Cr: 16.0 to 18.0%, Mo: 0.75% or less), after forming a nitride layer, 5% by weight of phosphorus, 30% by weight of nickel and 65% of cobalt.
A composite dispersed plating layer was formed by dispersing silicon nitride (Si ₃ N ₄ ) particles having a particle size of 0.3 to 5 μm in an area ratio of 10% in an alloy matrix containing 10% by weight (test piece A).

Example 2 After forming a nitride layer on the same alloy steel as in Example 1, phosphorus 5% by weight was used.
And 30% by weight of nickel and 65% by weight of cobalt to form a composite dispersion plating layer in which 10% by area ratio of molybdenum disulfide having a particle size of 0.3 to 5 μm was formed in an alloy matrix (test piece B).

Comparative Example 1 The same alloy steel as in Example 1 was subjected only to conventional hard chrome plating (test piece C).

Comparative Example 2 Only the nitride layer was formed on the same alloy steel as in Example 1 (test piece D). (1) Seizure resistance test With respect to the above test pieces A to D, a seizure resistance test was conducted by the following apparatus and method. FIG. 1 is a partial cross-sectional view showing a main part of the test apparatus, and FIG. 2 is a view taken along the line XX in FIG. The stator holder 1 is made of cast iron material FC25 used as a cylinder material, and the sliding surface 2 is honing-finished.
Is removably attached, and lubricating oil is applied to the center of the central part through the oil injection hole 4 from the back side. Here, a hydraulic device (not shown) is provided in the stator holder 1.
Thus, the pressing force (P) is applied at a predetermined pressure in the right direction in FIG. The test piece holder 6 mounted on the rotor 5 facing the disk 3 is provided with four mounting holes at equal intervals on a circle concentric with the rotating shaft, and the test piece 7 is attached to each of them. Can be installed. The tip surface of 5 mm × 5 mm of the test piece 7 each subjected to a predetermined surface treatment comes into contact with the sliding surface 2 of the disk 3, and is rotated at a predetermined speed by a driving device (not shown).

Using the above apparatus, a test was conducted while supplying lubricating oil at a constant temperature from the oil injection hole 4 on the stator side to the sliding surface. When the rotor 5 is rotated, the torque F (FIG. 2) is applied to the stator holder 1 due to the friction between the test piece 5 and the disk 3.
The torque F is detected by the load cell 9 via the spindle 8 and the change of the torque F due to the change of the pressing force is read by the dynamic strain gauge 10. When seizure occurs, the torque F rises sharply, so the pressing force at that time is taken as the seizure resistance of the test piece.

The test conditions were as follows: . Friction Speed: 8m / Sec lubricant: no additives motor oil # 30 oil temperature: 80 ° C. oil absorption: 400 cc / min contact pressure; 40 kg / cm ² than to baking generator 10 kg / cm
Figure 3 shows the test results of increasing the pressure by ^{2 and} holding each surface pressure for 3 minutes.

As is apparent from FIG. 3, the test pieces A and B on which the composite dispersed plating layer of the present invention was formed were the test piece C on which the hard chromium plating layer was formed and the test piece D on which only the nitride layer was formed. In comparison, seizure resistance is greatly improved.

(2) Actual machine test Nominal diameter × width × thickness made of steel (86.0 mm × 2.0 mm × 3.6 mm (SUS
440B) piston rings were subjected to the same surface treatment as the test pieces A to D used in the seizure resistance test, and test pieces A'to D'corresponding to the test pieces A to D, respectively. These are the bore diameters
86mm, 4-cycle water-cooled 4-cylinder 2600cc cast iron (F
The above-mentioned piston ring was incorporated into a C-25) engine cylinder, light oil was used as a fuel, and a bench test was performed for 100 hours at 6500 rpm and a full load to measure the oil consumption. The test results are shown in FIG.

As is apparent from FIG. 4, the piston rings [test pieces A ', B'] of the present invention having the composite dispersed plating layer formed on the upper layer thereof have reduced oil consumption from the initial stage. I understand.

No scuffing was observed in the piston rings [test pieces A ', B'] of the present invention. However, light scuffing was observed in the test piece D '.

[0030]

As described in detail above, the piston ring of the present invention, which has the nitrided layer and the cobalt-nickel-phosphorus alloy composite dispersion plating layer having a specific metal composition ratio on the outer peripheral sliding surface, is the composite dispersion plating. Due to the layer, it has excellent seizure resistance and excellent initial conformability.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a main part of a test apparatus for a seizure resistance test.

FIG. 2 is a view on arrow XX in FIG.

FIG. 3 is a graph showing the results of a seizure resistance test.

FIG. 4 is a graph showing a relationship between a test time and an oil consumption amount, which is obtained from an actual machine test.

[Explanation of symbols]

 1 ... Stator holder 2 ... Sliding surface 3 ... Disc 4 ... Lubrication hole 5 ... Rotor 6 ... Test piece holder 7 ... Test piece 8 ... Spindle 9 ... Load cell 10 ... Dynamic strain gauge

Claims (2)

[Claims] 1. A nitride layer on at least an outer peripheral sliding surface thereof,
In a piston ring having a double structure layer formed on the nitrided layer and having a composite dispersion plating layer having a thickness of 0.5 to 20 μm, the composite dispersion plating layer comprises 2 to 10% by weight of phosphorus and 10% by weight of nickel. Particle size in a matrix of cobalt-nickel-phosphorus alloy consisting of ~ 40 wt% and 55-88 wt% cobalt.
A piston ring, which is a layer in which particles of 0.3 to 10 μm are dispersed in an area ratio of 5 to 30%. 2. The piston ring according to claim 1, wherein the particles are hard particles selected from metal nitrides, carbides and oxides, and / or tungsten disulfide, molybdenum disulfide and boron nitride. A piston ring characterized by being selected solid lubricant particles. [0001]