JPH0374680A - Piston ring - Google Patents

Abstract

PURPOSE:To provide wear resistance and seizure resistance by a method wherein chrome oxide with an average grain size of 0.5-10 mum is dispersed in an area ratio of 5-40% in a base of an Ni-W alloy consisting of 50wt% W and a rest of Ni to form a composite plated layer. CONSTITUTION:In a piston ring, chrome oxide with an average grain size of 0.5-10 mum is dispersed in an area ratio of 5-40% in a base of an Ni-W alloy substantially consisting of 10-50wt% W and a rest of Ni to form a composite plated layer. By dispersing solid lubricant articles in the alloy base togetherwith chrome oxide, wear resistance and seizure resistance can be further improved. For example, molybdenum is used as the solid lubricant particles. The solid lubricant particles has capacity of 5-20 arear% and an average grain size of 0.5-10 mum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piston ring for an internal combustion engine, and particularly to a piston ring having a composite plating layer with excellent wear resistance.

[Prior art and problems to be solved by the invention] Piston rings, which are attached to the piston and slide at high speed in the cylinder pore of an engine, are first-class ones that are coated with hard chrome plating to increase wear resistance. It is used. However, chrome plating takes a considerable amount of time to process, and when used in engines that run on high-lead gasoline or under high loads, there are problems with wear resistance, seizure resistance, and corrosion resistance. .

In order to solve these problems, composite plating in which hard particles such as nitrides, oxides, or carbides are dispersed in an alloy matrix such as nickel-phosphorus has been attracting attention. This is called composite plating or dispersion plating, and shows excellent effects in improving wear resistance, seizure resistance, corrosion resistance, etc. by changing the type and size of dispersed particles and the amount of dispersion. However, in recent years, where the performance of engines has been significantly improved, it has been found that, depending on the engine model, it is not possible to obtain satisfactory results even when such composite plating is used.

Therefore, an object of the present invention is to eliminate the drawbacks of conventional hard chrome plating and composite plating, and to provide a piston ring that itself has excellent wear resistance.

[Means to solve the problem]

In view of the above problems, as a result of intensive research, the present inventor discovered that a piston ring with excellent wear resistance could be obtained by providing a composite plating layer in which hard particles were dispersed in a nickel-tungsten alloy base. , completed the invention.

That is, in the first piston ring of the present invention, chromium oxide with an average grain size of 0.5 to 10 μm is distributed over an area in a base of a nickel-tungsten alloy consisting of 10 to 50% by weight of tungsten and the remainder substantially nickel. It is characterized by having a composite plating layer that is dispersed in a ratio of 5 to 40%.

Further, the second piston ring of the present invention has an average grain size of 0.5% in a nickel-tungsten alloy matrix consisting of 10 to 50% by weight of tungsten and the remainder substantially nickel.
The area ratio of chromium oxide with a diameter of 5 to 10 μm is 5 to 40%, and the area ratio of solid lubricant particles with an average particle size of 0.5 to 10 μm is 5 to 40%.
It is characterized by having a composite plating layer that is dispersed by ~20%.

The present invention will be explained in detail below.

By adding tungsten as a component in the alloy base, heat resistance and corrosion resistance are improved, and the strength of the plating film is also improved. In addition, by performing thermohardness ratio treatment, the hardness of the base increases due to the action of tungsten, resulting in excellent wear resistance.

If the amount of tungsten in the alloy base is less than 10% by weight, the above effects cannot be obtained significantly, and even if it exceeds 50% by weight, there is no significant change in the effect. Therefore, the amount of tungsten is preferably 10 to 50% by weight.

Chromium oxide (CrsOs) dispersed in the alloy matrix exhibits an excellent effect on improving the wear resistance of the coating. The volume of chromium oxide to be dispersed is 5 to 40 area%, and the average particle size is 0.
．． 5 to 10 μm is good. If the capacity is less than 5% or the average particle size is less than 0.5 μm, the effect of improving wear resistance will be small.

Furthermore, if the capacity exceeds 40 area % or the average particle size exceeds 10 μm, the strength of the coating will decrease and furthermore, the wear of the mating material will increase.

When solid lubricant particles are dispersed together with chromium oxide in the alloy base, wear resistance and seizure resistance can be further improved. Preferred solid lubricant particles include molybdenum disulfide, tungsten disulfide, and boron nitride. It is preferable that the solid lubricant particles have a capacity of 5 to 20% by area and an average particle size of 0.5 to 10 μm. If the capacity is less than 5% or the average particle diameter is less than 0.5 μm, the effect of improving wear resistance and seizure resistance will be small. Moreover, if the capacity exceeds 20 area % or the average particle size exceeds 10 μm, the strength of the film decreases, and it becomes brittle and easily falls off.

Furthermore, after forming the composite film, heat curing treatment is performed at around 500°C to increase the hardness of the base, and then heat curing treatment is performed at around 550°C.
Nitriding at 600°C is effective in reducing piston ring side wear and increasing film strength. The nitriding treatment increases the crystallization of Nt4M in the film and increases the bond strength between the base material and the film.

In this way, if the nitriding treatment is performed after forming the composite film, there is an advantage that the adhesion between the base material and the composite film is improved and the fatigue strength of the base material is also increased. However, on the other hand,
If a composite film is formed after nitriding, even if the composite film wears away and disappears, the nitrided layer remains, improving wear resistance. Therefore, the order of these processes can be changed as appropriate.

[In examples]

The present invention will be explained in more detail by the following specific examples.

Example 1: Processed from steel material for piston rings, tip end surface weighs 5 g
As a first step, a nickel plating with a thickness of 5 μm was formed on the sliding surface of a rectangular parallelepiped test piece of 5 mm by the usual nickel strike plating method, and then as a second step, With the bath composition shown in and the plating conditions below, the thickness was obtained by dispersing chromium oxide with an average particle size of 1.2 μm.
A 120 μm nickel-tungsten composite plating was formed.

Plating conditions) Liquid temperature: 65°C, pH: 6.5, current density: 10^/dm2, plating time: 2 hours, and as a second step, heat curing treatment was performed by heating at 500°C for 1 hour.

Example 2 The same plating treatment and thermosetting treatment as in Example 1 were performed on the same test piece. However, as shown in Table 1, boron nitride with an average particle size of 2.0 μm was added to the plating bath components.

Micrograph of the metallographic structure of the obtained composite plating layer (X 4
00) is shown in FIG.

Example 3 The same test piece as in Example 1 was subjected to the same plating treatment and thermosetting treatment, and then gas nitriding treatment at 560°C.

Example 4 The same test piece as in Example 1 was subjected to the same plating treatment and thermosetting treatment, and then gas nitriding treatment at 560°C. However, as shown in Table 1, boron nitride with an average particle size of 2.0 μm was added to the plating bath components.

Table 1 Table 2 The composition of the plating film obtained in Examples 1 to 4 is shown in Table 2.
Shown in the table. In addition, as a result of measuring the hardness of the plating film with a micro Vickers hardness meter, the hardness of Example 1 was 950, and the hardness of Example 2 was 950.
is 920, and Example 3 is 1100. Example 4 was 1050.

Next, the piston ring material of the present invention was subjected to a wear resistance test, a seizure test, and an actual machine test.

(a) 11 Abrasion Test The abrasion test was conducted using a lidar one-type abrasion tester shown in FIGS. 2 and 3. Sliding surface 2 made of cast iron material FC251 & used as cylinder material etc. for stator holder 1
A disc 3 with a honed finish is removably attached to the disc 3, and lubricating oil is supplied to the center of the disc through an oil fill hole 4 from the back side. Further, a hydraulic device (not shown) applies a pressing force to the stator holder 1 rightward in the figure at a predetermined pressure.

A test piece 7 is attached to each of the four mounting holes carved at equal intervals on the circumference of a test piece holder 60 which is mounted on the rotor 5 facing the disk 3 and concentric with the rotating shaft. 5x of the test piece subjected to the surface treatment of Examples 1 to 4 above
The 5fl square tip end surface contacts the sliding surface 2 of the disc 3 and is rotated at a predetermined speed by a drive device (not shown). The test is conducted while lubricating oil at a constant temperature is supplied to the sliding surface from the oiling hole 4 on the stator side. Wear resistance is evaluated based on the amount of wear between 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, 0.2 g/i of dust (JIS type 2) was added to engine oil SAE & 30 after use in an actual machine test using leaded gasoline as a lubricant.
Using oil at 0°C, while applying a hydraulic pressure of 100 kg/L:II toward the rotor to the stator holder 1 supplied from the oil filling hole 4, the friction speed of the test piece 7 was adjusted to 3 to 5 m/L.
sec, and rotor 5 until the sliding distance reaches 1100k.
rotated.

In addition to the test pieces obtained in Examples 1 to 4, similar tests were conducted on hard chromium plating and molybdenum spraying, which are generally used for wear-resistant surface treatment, for comparison.

The test results are shown in Table 3 below.

113 table b) Seizure test A seizure test was conducted using the same testing machine as used in the above wear test.

When the rotor 5 is rotated, the friction between the test piece 7 and the disk 3 generates a torque F in the stator holder l as shown in the figure, so this torque F is applied to the load cell 9 via the spindle 8 to reduce the pressing force. The change in torque F caused by the change was read with a dynamic strain meter 10, and when the torque F suddenly increased, it was assumed that seizure had occurred, and the seizure resistance was evaluated based on the pressing force at that time.

The same lubricating oil as that used in the wear test was used, and the oil pressure of 40 kg/cd was first applied to the stator holder 1 toward the rotor.
The rotor 5 was rotated for 3 minutes with a pressing force of 50 kg/cd and a friction speed of 8 m/sec, and then rotated for 3 minutes with a pressing force of 50 kg/cd. In this way, the pressing force was increased to 10 kg/d.
increase stepwise and hold for 3 minutes each time, load cell 9
Changes in the torque F were recorded with a dynamic strain meter 10 via a dynamic strain meter 10, and the contact surface pressure was determined from the pressing force when the torque suddenly increased and was used as the surface pressure at which seizure occurred.

The test results are shown in Table 4 below.

Table 4 C) Actual machine test The composite plating of the present invention was applied to the outer circumferential sliding surface of the first steel pressure ring with nominal diameter x width x thickness of 86 x 1.5 x 3.3 mm, and a bore diameter of 86 m, 4 cylinders was applied. It was installed in a diesel engine with a water-cooled supercharger. Fueled by light oil, 520
A high-speed durability test was conducted for 100 hours at 0 rpm and full load.
The amount of wear on the inner circumferential surface of the litchi cylinder manufactured by e12) was measured.

In addition, as the composite plating of the present invention, tungsten 35
2% by weight, in a nickel-tungsten alloy base of essentially nickel, chromium oxide with an average particle size of 1.2 μm was added.
0 area% dispersed (Example 5), average particle size 1.2
Example 6
), Example 5 was heat-cured at 520°C for 1 hour and then gas nitrided at 520°C for 3 hours (Example 7), and Example 6 was heat-cured as above. The one subjected to treatment and nitriding treatment (Example 8) was used.

In addition, as a comparative example, the first pressure ring whose sliding surface was coated with hard chrome plating and molybdenum spraying,
A similar test was conducted. The test results are shown in Tables 5 and 6.

Table 1 [Effects of the Invention] As detailed above, the nickel-tungsten composite plating layer in which chromium oxide is dispersed according to the present invention has excellent wear resistance and seizure resistance compared to conventional plating layers. In addition, it is understood that it is suitable as a surface treatment layer for piston rings and the like because it causes less wear on the mating material. In addition, as can be seen from the results in Table 6, it was found that nitriding the composite plating layer was effective in reducing side wear, and was also effective in improving the toughness of the composite plating layer. It has been confirmed that it is effective. Furthermore, by forming a composite plating layer on the nitrided layer, even if the plating film disappears, the nitrided layer remains and durability can be improved.

Therefore, it can be seen that the piston ring having the composite plating film of the present invention exhibits excellent effects when used in an engine fueled by high lead gasoline, which particularly requires wear resistance.

[Brief explanation of drawings]

Fig. 1 is a micrograph (x 400) showing the metal structure of the composite plating layer according to the present invention, Fig. 2 is a partial cross-sectional view showing the main parts of the abrasion tester, and Fig. 3 is a FIG. 2 is a view taken along the line xx in FIG. 2;・・Stator holder・・Sliding surface・Disc・・Oil filling hole・・Rotor・・Test piece

Claims (4)

[Claims] (1) Chromium oxide with an average grain size of 0.5 to 10 μm is dispersed in an area ratio of 5 to 40% in a nickel-tungsten alloy matrix consisting of 10 to 50% by weight of tungsten and the remainder substantially nickel. A piston ring characterized by having a composite plating layer. (2) The piston ring according to claim 1, further comprising a nitriding treatment. (3) In the base of a nickel-tungsten alloy consisting of 10 to 50% by weight of tungsten and the remainder substantially nickel, chromium oxide with an average grain size of 0.5 to 10 μm is present in an area ratio of 5 to 40%. A piston ring characterized by having a composite plating layer in which solid lubricant particles having a particle size of 0.5 to 10 μm are dispersed in an area ratio of 5 to 20%. (4) The piston ring according to claim 3, further comprising a nitriding treatment.