JPH0552263A - Piston ring - Google Patents

Abstract

PURPOSE:To provide a piston ring which possesses the superior seizure resistance and abrasion resistance. CONSTITUTION:A piston ring has an outer peripheral sliding surface consisting of a composite plated layer which is formed by dispersing the chrome oxide particles having an average particle diameter of 0.5-10mum in 5-40% in area ratio, into a substrate made of the Co-Ni-p alloy consisting of 1-10wt.% P, 10-40wt.% Ni, and 55-80wt.% cobalt.

Description

Detailed Description of the Invention

[0001]

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 a composite plating layer having excellent seizure resistance and wear resistance.

[0002]

2. Description of the Related Art A piston ring, which is mounted on a piston in a cylinder bore of an engine and slides at a high speed, is generally plated with hard chrome to improve wear resistance. However, chrome plating takes a considerable amount of time to process, and when used in high-lead gasoline fueled engines and high-load engines, there were problems with wear resistance, seizure resistance, and corrosion resistance. ..

In order to solve such problems, nitrides and oxides are contained in an alloy matrix such as nickel-phosphorus,
Alternatively, composite plating in which hard particles such as carbide are dispersed has been receiving attention. This is called composite plating or dispersion plating, and exhibits excellent effects in improving wear resistance, seizure resistance, corrosion resistance and the like by changing the type and size of particles to be dispersed and the amount of dispersion.

[0004]

However, it has been found that, under the recent circumstances in which engine performance is remarkably improved, even if such composite plating is used, satisfactory results cannot be obtained depending on the engine model.

Therefore, an object of the present invention is to solve the drawbacks of the conventional hard chrome plating and to provide a piston ring having excellent seizure resistance and wear resistance.

[0006]

As a result of earnest research in view of the above problems, the present inventors have established a composite plating layer in which particles are dispersed in a base of a cobalt-nickel-phosphorus alloy having a specific alloy composition ratio. It was discovered that a piston ring excellent in seizure resistance and wear resistance can be obtained by doing so, and completed the present invention.

That is, the first piston ring of the present invention has 1 to 10% by weight of phosphorus and 10 to 40% by weight on the outer peripheral sliding surface.
In a matrix of cobalt-nickel-phosphorus alloy consisting of nickel and 55-80% by weight of cobalt, the average particle size is 0.5-10 μm.
It is characterized by having a composite plating layer in which the chromium oxide particles of m are dispersed in an area ratio of 5 to 40%.

The second piston ring of the present invention is
Cobalt composed of 1 to 10 wt% phosphorus, 10 to 40 wt% nickel and 55 to 80 wt% cobalt on the outer peripheral sliding surface.
Chromium oxide particles having an average particle size of 0.5 to 10 μm in an area ratio of 5 to 40% and an average particle size of 0.5 to
It is characterized by having a composite plating layer in which solid lubricant particles of 10 μm are dispersed in an area ratio of 5 to 20%.

The present invention is described in detail below. The composite plating layer provided on the sliding surface of the piston ring of the present invention is one in which particles are dispersed in a matrix composed of a cobalt-nickel-phosphorus alloy.

When phosphorus is contained in the alloy matrix and the heat treatment is performed, the hardness of the matrix is increased, the effect of excellent wear resistance is exhibited, and the effect of improving the corrosion resistance of the matrix is also exhibited. When the amount of phosphorus is less than 1% by weight, the hardness does not increase even if the heat curing treatment is performed, and the effect of improving wear resistance is small. On the other hand, if it exceeds 10% by weight, the hardness increases, but the plating film becomes rather brittle and the impact strength becomes weak, and the adhesion of the film also deteriorates. Therefore, the amount of phosphorus is 1 to 10% by weight. The preferred phosphorus content is 1.5 to 6% by weight.

Further, the inclusion of nickel in the alloy matrix improves the heat resistance, corrosion resistance and toughness of the coating, and further enhances the strength of the coating. 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 15 to 35% by weight.

Further, by containing cobalt in the alloy matrix, the heat resistance and corrosion resistance of the alloy matrix are improved, and the crush fatigue strength of the coating is also improved. 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. If the amount of cobalt in the alloy matrix of this composite plating film is less than 55% by weight, the above effect cannot be obtained remarkably, and even if it exceeds 80% by weight, there is no significant change in the effect. And The preferable cobalt content is 60 to 80% by weight.

By dispersing chromium oxide (Cr ₂ O ₃ ) particles in the alloy matrix, the wear resistance of the coating is improved. The volume of chromium oxide particles dispersed is 5 to 40% by area,
And the average particle size is 0.5 to 10 μm. If the capacity is less than 5% by area or the average particle size is less than 0.5 μm, the effect of improving wear resistance is small. On the other hand, when the capacity is 40% by area or the average particle size exceeds 10 μm, the strength of the film is lowered and the wear of the mating material is increased. The preferred volume of chromium oxide particles is 10 to 20 area%, and the preferred average particle size is 1 to 2 μm.

Further, when the solid lubricant particles are dispersed together with the chromium oxide particles in the alloy matrix, the wear resistance and seizure resistance of the coating can be further improved. As the solid lubricant particles, molybdenum disulfide, tungsten disulfide, boron nitride and the like are preferable. The volume of solid lubricant particles is 5
.About.20 area%, and the average particle size is 0.5 to 10 .mu.m. If the capacity is less than 5% by area or the average particle size is less than 0.5 μm, the effect of improving wear resistance and seizure resistance is small. Further, when the capacity is 20 area% or the average particle size exceeds 10 μm, the strength of the film is reduced, and the film becomes brittle and easily comes off. The volume of the preferred solid lubricant particles is 5 to 15 area%, and the preferred average particle size is 1 to 2 μm.

After the composite plating film is formed, it is exposed to 30
If heat-treated at a high temperature of 0 to 500 ° C for 1 to 2 hours,
The cobalt on the surface of the composite plating film is oxidized to form a tricobalt tetroxide layer, and the phosphorus in the film is more solidly dissolved by nickel and cobalt to increase the hardness of the film. The cobalt oxide layer formed on the surface of the composite plating film has a low coefficient of friction that is favorable for sliding friction.

In addition, after forming a composite plating film and subjecting it to the above-mentioned thermosetting treatment, if necessary, in the atmosphere, 300 to 500
If the finish surface of the composite plating film is subjected to oxidation treatment at a high temperature of ℃ for 1 to 3 hours, more cobalt elements on the surface of the composite plating film will change to tricobalt tetraoxide, and the tricobalt tetraoxide layer (thickness 2 to 3 μm), the seizure resistance of the piston ring is improved, and the side surface wear of the piston ring and the wear of the mating material (cylinder liner wear amount) are further reduced.

[0017]

The present invention will be described in more detail by the following specific examples. Example 1 The tip end surface processed with a steel material for a piston ring is 5 mm × 5
First, as a first step, a 5 mm thick nickel plating is formed on the sliding surface of a rectangular parallelepiped test piece by a conventional nickel strike plating method, and then, as a second step,
Under the bath composition shown in Table 1 and the following plating conditions, a cobalt-nickel-phosphorus composite plating having a thickness of 120 μm in which chromium oxide having an average particle diameter of 1 μm was dispersed was formed.

(Plating conditions) Liquid temperature 50 to 53 ° C pH 4.5 Current density 8 A / dm ² Plating time 2 hours

Further, as the third step, heat curing treatment was carried out by heating in air at 400 ° C. for 1 hour.

Example 2 The same test piece as in Example 1 was subjected to plating treatment and thermosetting treatment as in Example 1. However, as shown in Table 1, boron nitride having an average particle size of 1.2 μm was added to the plating bath components. A micrograph (× 400) of the metal structure of the obtained composite plating layer is shown in FIG.

Example 3 The same test piece as in Example 1 was subjected to the plating treatment and the thermosetting treatment in the same manner as in Example 1, and then the finished surface of the composite plating layer was subjected to oxidation treatment in the air at 400 ° C. for 3 hours. gave.

Example 4 The same test piece as in Example 1 was subjected to the plating treatment and the thermosetting treatment in the same manner as in Example 1, and then the finished surface of the composite plating layer was subjected to oxidation treatment in the air at 400 ° C. for 3 hours. gave. However, as shown in Table 1, some plating bath components have an average particle size of 1.2 μm.
Boron Night Ride was added.

Table 1 Component amount (g / liter) Bath composition Example 1 Example 2 Example 3 Example 4 Cobalt sulfate 200 200 200 200 Nickel sulfate 30 30 30 30 Nickel chloride 30 30 30 30 Sodium hypophosphite 2 2 2 2 Boric acid 30 30 30 30 Chromium oxide 40 40 40 40 Boron nitride 0 10 0 10

Table 2 shows the composition of the obtained composite plating films of Examples 1 to 4. Further, the hardness of the plating film was measured with a micro Vickers hardness meter. As a result, the first embodiment is 87
0, Example 2 is 860, Example 3 is 900, and Example 4 is 790.
Met.

Table 2 Plating Film Composition Example 1 Example 2 Example 3 Example 4 Cobalt (wt%) 67 67 67 67 Nickel (wt%) 20 20 20 20 Phosphorus (wt%) 3 3 3 3 Chromium oxide ( Area%) 25 25 25 25 Boron nitride (area%) 0 10 0 10

Next, abrasion tests and seizure tests were carried out on the obtained piston ring materials of Examples 1 to 4. The outline of the test method and the test results are shown below.

A) Abrasion test The abrasion test was carried out by a rider type abrasion tester shown in FIGS. 2 and 3. A disk 3 made of cast iron material FC25, which is used as a cylinder material, etc., and whose sliding surface 2 is honing-finished, is detachably attached to the stator holder 1, and lubricating oil is passed through the oiling hole 4 from the back side in the center thereof. Is supplied. Further, a pressing force is applied to the stator holder 1 by a hydraulic device (not shown) at a predetermined pressure toward the right in the drawing.

In the first embodiment described above, four mounting holes are formed at equal intervals on a circle concentric with the rotation axis of the test piece holder 6 mounted on the rotor 5 so as to face the disk 3. The test piece 7 which has been subjected to the surface treatment of ~ 4 is attached. The 5 mm × 5 mm square tip surface of the test piece comes into contact with the sliding surface 2 of the disc 3 and is rotated at a predetermined speed by a driving device (not shown).

The test is carried out while supplying lubricating oil having a constant oil temperature to the sliding surface from the oil injection hole 4 on the stator side. The wear resistance is evaluated by the wear amount of the test piece 7 and the stator disk 3 when the test piece 7 slides on the disk 3 by a predetermined sliding distance.

Specifically, as a lubricating oil, engine oil SA after being used in an actual machine test using leaded gasoline as a fuel
Dust (JIS class 2) 0.2 g / liter was added to ENo.30, and oil at a temperature of 80 ° C was supplied from the oiling hole 4 to the stator holder 1 toward the rotor 5 and the oil pressure was 100 kg / cm ²
The friction speed of the test piece 7 is 3 to 5 m while applying the pressing force of
/ Sec and the rotor 5 was rotated until the sliding distance became 100 km.

In addition to the test pieces obtained in Examples 1 to 4, the same tests were conducted for hard chrome plating and molybdenum spraying, which are generally used for abrasion-resistant surface treatment, for comparison. The test results are shown in Table 3 below.

[0032]

B) Seizure test A seizure test was conducted using the same tester as the above abrasion test.
When the rotor 5 is rotated, friction between the test piece 7 and the disc 3 causes the torque F on the stator holder 1 as shown in FIG.
Occurs. This torque F was applied to the load cell 9 via the spindle 8, and the change in the torque F due to the change in the pressing force was read by the dynamic strain gauge 10. It was considered that seizure occurred when the torque F rapidly increased, and the seizure resistance was evaluated by the pressing force at that time.

The same lubricating oil as that used in the wear test was used, and the stator holder 1 had a hydraulic pressure of 40% toward the rotor side.
Apply a pressing force of kg / cm ² and rotate the rotor 5 for 3 minutes at a friction speed of 8 m / sec, then set the pressing force to 50 kg / cm ² and
Spin for minutes. In this way, the pressing force is sequentially increased to 10 kg / cm.
Gradually increase by ^{2 and} hold for 3 minutes each, record the change of the torque F with the dynamic strain gauge 10 through the load cell 9, and obtain the contact surface pressure from the pressing force when the torque suddenly increases to print. The generated surface pressure was used. The test results are shown in Table 4 below.

[0035]

C) Actual machine test Nominal diameter x width x thickness 86 mm x 1.5 mm x 3.3 mm SUS440
The outer peripheral sliding surface of the B17 chrome steel first pressure ring was subjected to various kinds of composite plating of the present invention described later, and assembled on a 4-cylinder water-cooled supercharged diesel engine with a bore diameter of 86 mm.
Using light oil as a fuel, a high-speed durability test was conducted at 5200 rpm for 100 hours at full load, and the wear amount of the outer peripheral sliding surface, the upper and lower side surfaces of the first pressure ring and the inner peripheral surface of the cast iron (FC25) cylinder liner was measured.

The composite plating of the present invention has a mean grain size of 1.8 μm in a cobalt-nickel-phosphorus alloy matrix containing 3% by weight of phosphorus, 20% by weight of nickel and 67% by weight of cobalt.
m chromium oxide was dispersed in 20 area% to form a composite plating, and then heat-cured at 400 ° C. for 1 hour (Example 5). The same alloy matrix as in Example 5 had an average particle size of 1.8 μm. 20% by area of chromium oxide and 15% by volume of boron nitride having an average particle size of 3 μm are dispersed to form a composite plating.
What was subjected to a heat curing treatment at ℃ × 1 hour (Example 6), that of Example 5 was further subjected to atmospheric oxidation treatment at 400 ℃ × 3 hours (Example 7), and of Example 6. The thing which was further subjected to the oxidation treatment in the air at 400 ° C. for 3 hours (Example 8) was used.

Further, as a comparative example, the same test was carried out on the first pressure ring whose hard chrome plating and molybdenum thermal spray were applied to the sliding surfaces. The test results are shown in Tables 5 and 6.

Table 5 Piston Ring Cylinder Liner Outer Wear Amount Wear Amount Hard chrome plating 25 μm 10 μm Molybdenum spraying 20 μm 20 μm Example 5 5 μm 2 μm Example 6 4 μm 2 μm Example 7 6 μm 1 μm Example 8 5 μm 1 μm

[0040]

[0041]

As described above in detail, the cobalt-nickel-phosphorus alloy composite plating layer in which the particles according to the present invention are dispersed has wear resistance as compared with the conventional plating layers (hard chrome plating and molybdenum spraying), It is understood that, in addition to being excellent in seizure resistance, it hardly wears the mating material and is suitable as a surface treatment layer of a piston ring. Further, as can be seen from the results of Table 4, Table 5 and Table 6, the piston ring having the composite plating layer which has been subjected to the oxidation treatment in particular has a side surface wear and a wear of the mating material (cylinder It can be seen that it is effective in reducing the liner wear amount) and that it has excellent seizure resistance.

Therefore, it can be understood that the piston ring having the composite plating layer of the present invention exhibits an excellent effect particularly when used in an engine using high lead gasoline, which requires abrasion resistance and seizure resistance. ..

[Brief description of drawings]

FIG. 1 is a micrograph (× 400) showing a metal structure of a composite plating layer (Example 2) according to the present invention.

FIG. 2 is a partial cross-sectional view showing a main part of an abrasion tester.

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

[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 (4)

[Claims] 1. The outer peripheral sliding surface contains 1 to 10% by weight of phosphorus, and
Average particle size in a matrix of cobalt-nickel-phosphorus alloy consisting of ~ 40 wt% nickel and 55-80 wt% cobalt.
A piston ring comprising a composite plating layer in which chromium oxide particles of 0.5 to 10 μm are dispersed in an area ratio of 5 to 40%. 2. The piston ring according to claim 1, wherein the surface of the composite plating layer is subjected to an oxidation treatment to form an oxide layer mainly containing cobalt oxide. 3. The outer peripheral sliding surface contains 1 to 10% by weight of phosphorus,
Average particle size in a matrix of cobalt-nickel-phosphorus alloy consisting of ~ 40 wt% nickel and 55-80 wt% cobalt.
Chromium oxide particles of 0.5 to 10 μm with an area ratio of 5 to 40%,
Area ratio of solid lubricant particles with an average particle size of 0.5-10 μm is 5
A piston ring having a composite plating layer having a dispersion of up to 20%. 4. The piston ring according to claim 3, wherein the surface of the composite plating layer is subjected to an oxidation treatment to form an oxide layer mainly containing cobalt oxide.