JPS62258264A - Piston ring - Google Patents

Abstract

PURPOSE:To improve the abrasion resistance by nitriding a piston ring having a sliding face formed with a complex film layer where specific vol.% of hard particles having specific grain size are dispersed into an iron-chrome galvanization basic layer containing 2-20wt% of chrome. CONSTITUTION:Hard particles of silicon nitride, silicon carbide, cobalt oxide, etc. having the average grain size of 0.5-10mum are dispersed by 5-30vol.% into an iron-chrome alloy galvanization basic layer containing 2-20wt% of chrome. The sliding face of a piston ring 1 is galvanized by said complex film layer 2. Said piston ring is nitrided to form nitriding layers 3 on a galvanized layer 2 and the upper and lower layers of the piston cylinder 1 thus improving the abrasion resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a piston ring for an internal combustion engine that has a composite plating layer with excellent wear resistance on its sliding surface.

(Prior art and problems) Problems that occur in the function of piston rings include oil consumption and blow pie from the perspective of the engine as a whole, and issues such as wear resistance, heat resistance, oil retention, and cylinder material from the perspective of the piston ring itself. There are problems such as wear and tear. For this reason, current piston rings are coated with hard chrome plating,
Surface treatments such as molybdenum spraying or nitriding treatment such as tuftride are carried out on steel.

However, hard chrome plating has problems with wear resistance and seizure resistance when leaded gasoline is used, while molybdenum thermal spraying has good heat resistance and seizure resistance, but is inferior in wear resistance, and the mating cylinder material also wears out. let Further, although tuftride treatment has excellent wear resistance, when performing nitriding treatment on cast iron or ordinary steel, the treatment temperature is raised to a high temperature, which is undesirable as the ring deforms, and the seizure resistance is also poor.

The present invention aims to eliminate the drawbacks of conventional hard chrome plating, Mo spraying, nitriding, etc., and to provide a piston ring having a hard coating layer that itself has excellent wear resistance and a small coefficient of friction.

(Structure of the Invention) In order to achieve the above object, the present invention provides, as a first invention, a base layer of an iron-chromium alloy plating consisting of 2 to 20% by weight of chromium and the remainder iron. .5-10μm
Provided is a piston ring characterized in that the piston ring has a composite coating layer on its sliding surface in which hard particles of 5 to 30% by volume are dispersed, and the piston ring is nitrided. As an invention, hard particles with an average particle size of 0.5 to 10 μm are mixed in a volume ratio of 5 to 30% in a base layer of iron-chromium alloy plating consisting of 2 to 20% by weight of chromium and the remainder iron.
and lubricant particles with an average particle size of 0.5 to 20 μm are dispersed in a range of 5 to 20% by volume, - and the total of hard particles and lubricant particles are dispersed in a range of 10 to 45% by volume. The above-mentioned problems are solved by providing a piston ring characterized in that the piston ring has a composite coating layer on its sliding surface and is subjected to nitriding treatment.

Chromium has a strong affinity with nitrogen, and its hardness increases by nitriding. By using an iron-chromium alloy as the base of the composite coating layer, it becomes possible to perform nitriding treatment on the single dispersion plating layer itself, which exhibits an excellent effect in improving wear resistance. Further, the nitriding treatment is effective in improving the wear resistance not only of the dispersion plating layer but also of the upper and lower surfaces of the piston ring and the inner circumferential surface.

If the amount of chromium is less than 2%, even if nitriding is performed, the hardness will not increase and the effect on wear resistance will be small.

Further, even if the amount exceeds 20%, no significant change in the effect is observed. Therefore, the amount of chromium is preferably 2 to 20% by weight.

Hard particles, together with chromium, have an excellent effect on improving the wear resistance of coatings. Examples of hard particles include metal nitrides such as silicon nitride, silicon carbide, titanium carbide, zirconia, alumina, cobalt oxide, metal carbides, Metal oxides are suitable.

It is preferable that the capacity of the hard particles is 0.5 to 30% and the average particle size is 0.5 to 10 μm. If the capacity is 0.5% or less or the average particle size is 0.5 μm or less, the hard particles occupy a large proportion of the base surface. If the area is small and the abrasion resistance effect is low, and if the capacity exceeds 30% or the average particle size exceeds 10 μm, the abrasion of the mating material will increase and the strength of the film will also decrease.

In the present invention, as a second invention, lubricating particles are also dispersed in addition to hard particles. Lubricant particles have an excellent effect on improving the wear of the mating material. As lubricant particles, for example, a solid lubricant with a low coefficient of friction that has cleavability is suitable. Typical examples include particles of molybdenum disulfide, graphite fluoride, boron nitride, graphite, mica, Teflon, etc. .

The capacity of the lubricant particles is preferably 0.5 to 20% and the average particle size is 0.5 to 20 μm. If the capacity is 0.5% or the average particle size is less than 0.5 μm, the lubricant is less effective. Moreover, if the capacity exceeds 20% or the average particle size exceeds 20 μm, not only will the wear resistance of the plating layer itself decrease;
The strength of the film also decreases.

The total amount of hard particles and lubricant particles is suitably 10 to 45% by volume from the viewpoint of wear resistance and effectiveness as a lubricant.

(Example 1) Nominal diameter xl [x thickness 78m XL, 5mm x3
．． A 120 μm thick steel plate with silicon nitride dispersed in it was placed on a 3 m long steel first pressure ring using the bath composition and plating conditions shown in Table 1.
A chromium composite plating was formed.

The amount of chromium in the composite plating layer was 13% by weight, and the amount of silicon nitride was 25% by volume.

Next, the piston ring was subjected to a nitriding treatment at 580° C. for 1 hour to perform a thermosetting treatment to harden the base. Through this treatment, the micropicchus hardness was changed from 400 to 500 to 900 to 1000.

(Example 2) As an example of the second invention, as in Example 1, a steel first pressure ring with a nominal diameter x width x thickness of 78a * x 1.5m x 3.3 Using the bath composition and plating conditions described above, an iron-chromium composite plating with a thickness of 110 μm was formed in which silicon nitride was dispersed as hard particles and molybdenum disulfide was dispersed as lubricant particles.

The amount of chromium in the composite plating layer is 13% by weight.

The amount of silicon nitride was 15% by volume, and the amount of molybdenum disulfide was 10% by volume.

Next, the piston ring was subjected to nitriding treatment at 580° C. for 1 hour to harden the base.

(Actual machine test) The piston rings obtained in Example 1 and Example 2 were installed in a 4-cycle, 4-cylinder water-cooled engine with a cylinder bore diameter of 78cm, and the engine was operated for 6800 r using high lead gasoline as fuel.
A bench test was conducted for 100 hours at pm and full load, and the amount of wear on the outer peripheral sliding surface of the piston ring and the inner peripheral surface of the cylinder (made of cast iron Fe12) was measured.

For comparison, piston rings with hard chrome plating, molybdenum spraying, and Tuftride treatment were also tested in the same way.

The test results are shown in Figure 2.

(Effects) As is clear from FIG. 2, both the piston rings of the first invention and the second invention have less wear than the comparative piston rings, and have less wear on the mating cylinder.
Furthermore, since the piston ring of the second invention has lubricant particles dispersed therein, the wear of the mating member is less than that of the first invention.

If a material such as 5KD-61 is selected as the base material of the piston ring and subjected to nitriding treatment, the upper and lower surfaces of the piston ring and the inner peripheral surface base material are also nitrided at the same time as the composite plating layer, resulting in excellent wear resistance. You can get piston rings.

Thus, it can be seen that the piston ring of the present invention is particularly effective for engines using high lead gasoline as fuel, which requires high wear resistance.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the piston ring of the present invention.
Piston ring 2: Composite plating layer 3: Nitrided layer FIG. 2 is a graph showing the wear of the piston ring and the mating cylinder in an actual machine test. Figure 1 Figure 2

Claims (2)

[Claims] (1) Iron - consisting of 2 to 20% by weight of chromium and the rest iron.
In the base layer of chromium alloy plating, the average grain size is 0.5 to 10.
A piston ring characterized in that the piston ring has a composite film layer on the sliding surface in which hard particles of μm are dispersed in a range of 5 to 30% by volume, and the piston ring is nitrided. (2) Iron - consisting of 2 to 20% by weight of chromium and the rest iron.
In the base layer of chromium alloy plating, the average grain size is 0.5 to 10.
The volume ratio of hard particles of μm is 5 to 30%, and the average particle size is 0.
The lubricant particles with a diameter of 5 to 20 μm are in the range of 5 to 20% by volume, and the total of hard particles and lubricant particles is in the range of 10 to 20% by volume.
A piston ring characterized in that the piston ring has a composite film layer dispersed in a range of 45% on its sliding surface and is nitrided.