JPH0413897A - Piston ring - Google Patents

Abstract

PURPOSE:To produce a piston ring having superior wear resistance by forming a composite coating layer obtd. by dispersing chromium oxide particles and silicon nitride particles under specified conditions in an Ni-Co-P alloy plating layer having a specified compsn. as a matrix layer on a piston ring. CONSTITUTION:A composite coating layer obtd. by dispersing 5-40% by area of chromium oxide particles of 0.5-10mum average particle size and 5-20% by area of silicon nitride particles of 0.5-10mum average particle size in an Ni-Co-P alloy plating layer consisting of 1-15wt.% P, 10-50 wt.% Co, and the balance Ni as a matrix layer, is formed on a piston ring. A piston ring with a composite plating layer having superior wear resistance is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention particularly relates to a piston ring having a composite plating layer with excellent wear resistance.

(Prior Art) Piston rings that slide at high speed are generally coated with hard chrome plating to improve wear resistance. Chrome plating takes a considerable amount of time to process and has problems with wear resistance, seizure resistance, and corrosion resistance when used in engines that run on high-lead gasoline or under heavy loads. .

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, is attracting attention. This is called composite plating or dispersion plating.
By changing the type and size of particles to be dispersed, as well as the amount of dispersion, excellent effects are shown in improving wear resistance, seizure resistance, and corrosion resistance.

(Problems to be Solved by the Present Invention) The technical object of the present invention is to solve the above-mentioned problems of piston rings coated with hard chrome coating, etc., and to further improve wear resistance in particular.

[Configuration of the present invention]

(Technical solution) First, as a first means, in the base layer of a nickel-cobalt-phosphorus alloy plating consisting of 1 to 15% by weight of phosphorus, 10 to 50% by weight of cobalt, and the remainder nickel, the average particle size is 0.5
~10μm of chromium oxide with an area ratio of 5~40% and 0.
It has a composite film layer in which silicon nitride particles of 5 to 10 μm are dispersed in an area of 5 to 20%.

Next, as a second means, in addition to the first means, nitriding treatment is performed.

(Function) First, according to the first means, the phosphorus contained in the alloy base increases the hardness of the base through thermosetting treatment, exhibiting an excellent effect on wear resistance, and also improves the corrosion resistance of the base. effective.

If the amount of phosphorus is less than 1%, the hardness will be high (
However, the effect of wear resistance is small. If it exceeds 15%, the hardness increases, but the coating becomes brittle, the impact strength becomes weaker, and the adhesion of the coating deteriorates. Therefore, the amount of phosphorus is 1
~15% is good.

By adding cobalt to the alloy matrix, heat resistance and corrosion resistance are improved, and the strength of the film is also improved.

If the amount of cobalt in the alloy matrix 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 cobalt is preferably 10 to 50% by weight.

Chromium oxide (Cr20□) dispersed in the alloy base exhibits an excellent effect on improving the wear resistance of the coating. The volume of dispersed chromium oxide is 5 to 40% by area, and the average particle size is 0.
5 to 10 μm is good. If the capacity is 5% or less or the average particle size is 0.5 μm or less, the effect of improving wear resistance is small. Moreover, if the capacity exceeds 40 area % or the average particle size exceeds 10 μm, the strength of the film will be reduced, and furthermore, the wear of the mating material will be increased.

Solid lubricant particles dispersed together with chromium oxide in the alloy fabric improve wear resistance and seizure resistance.

The silicon nitride particles preferably have a capacity of 5 to 20 area % and an average particle diameter of 0.5 to 10 μm. If the capacity is 5% or less or the average particle size is 0.5 μm or less, the effect of improving wear resistance and seizure resistance is small. Moreover, if the capacity exceeds 20 area % or the average particle size exceeds 10 μm, the strength of the film will be rather reduced, and furthermore, it will become brittle and easily fall off.

According to the second means, this is effective in improving piston ring side wear and increasing film strength. Conventional composite plating films containing phosphorus are heat-cured at around 400°C to increase the hardness of the base. When this film is further subjected to nitriding treatment at 550 to 600°C, the hardness of the base is reduced, but the toughness of the film is increased, and the interlayer strength of the film, which causes peeling, is improved.

In addition, the method of applying nitriding treatment after forming the composite film layer not only improves the adhesion between the base material and the composite film layer but also increases the fatigue strength of the base material than the method of forming the composite film after nitriding treatment. It has the advantage of being

(Example 1) The tip end surface of the steel material for piston rings is 5 mm x 5
As a first step, a nickel plating with a thickness of 5 μm was formed on the sliding surface of a test piece of 5 μm in thickness using the usual nickel strike plating method, and then as a second step,
A nickel-cobalt-phosphorus composite plating with a thickness of 120 μm in which chromium oxide was dispersed was formed using the following bath composition and plating conditions.

stomach, In the second invention, gas nitriding treatment was performed at 560°C.

Table 2 shows the composition of the plating film and the results of measuring its hardness using a micro Vickers hardness meter.

As the third step, the first invention provides 40 parts of the piston ring.
A thermosetting treatment was performed by heating at 0° C. for 1 hour. Next, a wear resistance test and a seizure test of the sliding surface according to the present invention will be explained. The test was conducted using a lidar one-type abrasion tester shown in FIGS. 2 and 3. The outline is that a disc 3 made of cast iron FC25, which is used as a cylinder material, etc., and whose sliding surface 2 has been honed is removably attached to a stator holder 1, and in the center there is a lubrication hole 4 from the back side.
Lubricating oil is supplied through the stator holder 1, and a predetermined pressing force is applied to the stator holder 1 toward the right in the figure by a hydraulic device (not shown).

A test piece 7 is attached to each of four attachment holes carved at equal intervals on a circumference concentric with the rotation axis of a test piece holder 6 attached to the rotor 5 facing the disk 3, A 5 x 5 mm square tip end face of each test piece, which has been subjected to a predetermined surface treatment, contacts the sliding surface 2 of the disk 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.

In the wear test, the rotor 5 is rotated under a constant pressing force, and the wear resistance is determined by the amount of wear of the test piece 7 and the stator disk 3 when the test piece 7 slides on the circle Fi3 by a predetermined sliding distance. Evaluate.

Furthermore, when the rotor 5 is rotated, a torque F is generated in the stator holder 1 as shown in the figure due to the friction between the test piece 7 and the disk 3, so this torque F is applied to the load cell 9 via the spindle 8, and the pressing force is The change in the torque F due to the change in is read by the dynamic strain meter 10, and it is assumed that seizure occurs when the torque F suddenly increases, and the seizure resistance is evaluated based on the pressing force at that time.

For test piece 7, in addition to the test piece obtained in the above example, similar tests were conducted on hard chromium plating and molybdenum spraying, which are generally used for wear-resistant surface treatment, for comparison.

a) Engine oil SAE No. 30 with dust (
Using oil at a temperature of 80'C to which 0.2 g/l of JIS Class 2) was added, it was supplied from the oil filling hole 4, and while applying a pressing force of hydraulic pressure of 100 kg/cm2 to the stator holder 1 toward the rotor side, the test piece was The friction speed of 7 is 3 to 5 m/sec,
The rotor 5 was rotated until the sliding distance reached 1100K.

The test results are shown in Table 3 below.

Each test was held for 3 minutes, and the change in torque F was recorded by the dynamic strain meter 10 via the load cell 9, and the contact surface pressure was determined from the pressing force when the torque increased sharply and was used as the surface pressure at which seizure occurred.

The test results are shown in Table 4 below.

b) Use the same lubricant for the seizure test as that for the wear test, and first apply a hydraulic pressure of 40 kg/cm to the stator holder 1 toward the rotor.
Apply a pressing force of 2 and rotate the rotor 5 for 3 minutes at a friction speed of 3 m/sec, then apply a pressing force of 50 kg/cm 2
Rotate for 3 minutes and increase the pressing force to 1 in this way.
C) Actual machine test Next, the composite plating of the present invention was applied to the outer peripheral sliding surface of the first pressure ring made of steel with a nominal diameter x width x thickness of 86 x 1.5 x 3.3 mm, It is installed in a 4-cylinder diesel engine with a bore diameter of 86 mm and a water-cooled supercharger, and uses light oil as fuel to generate 5200 yen.
A high-speed durability test was conducted for 100 hours at rpm and full load.
The wear on the inner circumferential surface of the cylinder liner manufactured by No. 12) was measured.

This first pressure ring is made of a nickel-cobalt-phosphorus alloy base containing 25% by weight of cobalt, 4% by weight of phosphorus, and the balance of nickel.
20 area % of chromium oxide with an average particle size of 0.8 μm and 15 volume % of silicon nitride with an average particle size of 1.2 μm were dispersed, each of which was subjected to heat curing treatment at 400 ° C for 1 hour, A material that had been subjected to gas nitriding treatment at 560°C for 3 hours was used.

As a comparative example, a test was also conducted on a first pressure ring whose sliding surface was coated with hard chromium plating and molybdenum spraying similar to those used in the above embodiments. The test results are shown in Tables 5 and 6.

[Table 5] (Effects) Tables 3, 4, 5, and 6 show that the nickel-covered iron in which chromium oxide and silicon nitride of the present invention are mixed and dispersed has wear resistance,
It is understood that it is suitable as a surface treatment layer for piston rings and the like because it has excellent seizure resistance and causes less wear on the mating material. In addition, as can be seen from the results in Table 6, the second invention, which was subjected to nitriding treatment, was found to be more effective in reducing side surface wear, and in addition,
It has been confirmed that it is also effective in improving the toughness of composite matte layers.

Therefore, it can be seen that the composite coating of the present invention exhibits excellent effects particularly on engines using high lead gasoline as fuel, which requires high wear resistance.

[Brief explanation of drawings]

Fig. 1 is a micrograph (X400) showing the metal structure of a composite plating layer showing an example of the second invention, Fig. 2 is a partially exploded view showing the main parts of the wear tester, and Fig. 3 is X- in Figure 2
It is an X arrow view. In the diagram: 1... Stator holder, 2... Sliding surface, 3...
...Disk, 4...Oil filling hole, 5...Rotor, 7...
Test piece agent Patent attorney Hideaki Kuwahara

Claims (2)

[Claims] (1) Chromium oxide particles with an average particle size of 0.5 to 10 μm are added to the base layer of a nickel-cobalt-phosphorus alloy plating consisting of 1 to 15% by weight of phosphorus, 10 to 50% by weight of cobalt, and the remainder nickel. 5-40% in area ratio and 0.5-10μ
A piston ring characterized by having a composite film layer in which silicon nitride particles of m are dispersed in an area ratio of 5 to 20%. (2) Chromium oxide particles with an average particle size of 0.5 to 10 μm are added to the base layer of a nickel-cobalt-phosphorus alloy plating consisting of 1 to 15% by weight of phosphorus, 10 to 50% by weight of cobalt, and the remainder nickel. 5-40% in area ratio and 0.5-10μ
1. A piston ring characterized in that the piston ring has a composite film layer in which silicon nitride particles of m are dispersed in an area ratio of 5 to 20%, and is subjected to a nitriding treatment.