JPH0337028B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field of the Invention) The present invention relates to a piston ring for internal combustion engines having a composite plated layer with excellent wear resistance on its sliding surface, and an Al-
Regarding the combination technology of Si cylinders. (Conventional technology and problems) In recent years, with the reduction in weight of internal combustion engines, hypereutectic Al-
Cylinders made of Si alloy or hypoeutectic Al-Si alloy have been put into practical use in some cases. Although this Al-Si alloy cylinder exhibits good wear resistance, it is somewhat inferior to a cast iron cylinder. Conventionally, piston rings used in combination with this type of cylinder have been proposed with nickel composite plating with silicon carbide dispersed on the sliding surface or iron composite plating with silicon carbide dispersed. ing. By dispersing hard particles such as silicon carbide,
Wear resistance is improved by the oil retaining effect between the first sliding surface by the hard particles and the second sliding surface by the base portion. However, in nickel or iron composite plating in which silicon carbide is dispersed, the silicon carbide particles of the dispersed material are hard and the edges of the crystals are sharp, so the mating cylinder material is likely to wear out. Furthermore, if the base of the composite plating layer is nickel or iron alone, the hardness is insufficient, and conversely, it is susceptible to wear due to the primary silicon of the cylinder material. In addition, hard chrome plating, which is commonly used for piston ring surface treatment,
Due to its poor wettability with lubricating oil, it has little oil retention effect and is prone to seizing. As described above, in the conventional combination of a plated piston ring and an Al-Si cylinder, abnormal wear may occur in the piston ring or cylinder when leaded gasoline is used or under severe operating conditions. (Structure of the Invention) In order to achieve the above object, the present invention provides, as a first invention, a base layer of nickel-phosphorus alloy plating containing 0.2 to 10% by weight of phosphorus and the remainder being nickel. 10μm silicon nitride 5-30% by volume
A second invention provides a combination of a piston ring having a sliding surface with a composite film layer dispersed in a range of
Silicon nitride with an average grain size of 0.5 to 10 μm is added in a volume ratio of 5 to 30% in the base layer of a nickel-cobalt-phosphorus alloy plating consisting of 0.2 to 10% by weight, 10 to 40% by weight of cobalt, and the remainder of nickel. The above-mentioned problems are solved by providing a combination of a piston ring having a composite film layer dispersed over a wide range on its sliding surface and a cylinder made of hypereutectic Al--Si. The composite film layer will be described below. When the phosphorus contained in the alloy base is subjected to a thermosetting treatment, its hardness increases and it exhibits an excellent effect on wear resistance, and is also effective in improving the corrosion resistance of the base. If the amount of phosphorus is less than 0.2%, the hardness will not increase even if heat hardening treatment is performed, and the effect of wear resistance will be small.
If it exceeds 10%, the hardness increases, but the film becomes brittle, the impact strength becomes weaker, and the adhesion to the piston ring base material deteriorates. Therefore, the amount of phosphorus is
0.2-10% is good. The silicon nitride particles dispersed in the film, together with phosphorus, have an excellent effect on improving the wear resistance of the film. In addition, since the crystals are less sharp than silicon carbide particles, they are less likely to wear out the mating cylinder material. moreover,
Among ceramics, silicon nitride particles have poor wettability with metals and are difficult to melt with metals, so they also have better scuff resistance than silicon carbide particles. The capacity of silicon nitride is preferably 0.5 to 30%, and the average particle size is preferably 0.5 to 10 μm. If the capacity is less than 0.5% or the particle size is less than 0.5 μm, the area occupied by silicon nitride on the base surface is small and the wear resistance effect is small.
Furthermore, if the capacity exceeds 30% or the particle size exceeds 10 μm, the wear of the mating material will increase, and the strength of the film will also decrease. In the present invention, cobalt is added to the alloy base as the second invention. Cobalt improves the heat resistance and corrosion resistance of the alloy base, as well as the crush fatigue strength of the coating. If the amount of cobalt in the alloy base is less than 10% by weight, the above effects cannot be obtained significantly, and even if it exceeds 40% by weight, there is no significant change in the effect. Therefore, the amount of cobalt is preferably 10 to 40% by weight. (Example 1) As a first step, a steel first pressure ring with a nominal diameter x width x thickness of 78 mm x 1.5 mm x 3.2 mm was coated with a thickness by the usual nickel strike plating method on the sliding surface.
A nickel plating of 10 μm was formed. Next, as a second step, a nickel-phosphorus composite plating having a thickness of 120 μm in which silicon nitride was dispersed was formed on the sliding surface of the ring using the bath composition and plating conditions shown in Table 1.

[Table] The amount of phosphorus in the composite plating layer was 5% by weight, and the amount of silicon nitride was 25% by volume. As the third step, the piston ring is heated to 400℃.
A thermosetting treatment was performed by heating for a period of time to harden the base. This treatment reduces the microbits hardness.
It became 800-900. (Example 2) As an example of the second invention, similarly to Example 1, a first pressure ring made of steel with a nominal diameter x width x thickness of 78 mm x 1.5 mm x 3.2 mm was plated with nickel strike. After the formation, as a second step, a nickel-cobalt-phosphorus composite plating having a thickness of 110 μm in which silicon nitride was dispersed was formed on the sliding surface of the ring using the bath composition and plating conditions shown in Table 2.

【table】

[Table] The amount of phosphorus in the composite plating layer was 5% by weight, the amount of cobalt was 35% by weight, and the amount of silicon nitride was 15% by volume. As the third step, the piston ring is heated to 400℃.
The base was cured by heating for a period of time. This treatment resulted in a microbits hardness of 800-900. (Experimental Test) The piston rings obtained in Example 1 and Example 2 were installed in a 4-cycle, water-cooled 4-cylinder engine with a cylinder bore diameter of 78 mm, and a bench test was conducted at 6800 rpm, full load, for 100 hours using high lead gasoline as fuel. The amount of wear on the outer circumferential sliding surface of the piston ring and the inner circumferential surface of the aluminum alloy cylinder (made of A390 alloy) was measured. For comparison, piston rings with hard chrome plating, nickel composite plating with silicon carbide dispersed therein, and iron composite plating with silicon carbide dispersed therein were similarly tested. The test results are shown in Figure 2. (Effects) The combination of the piston ring and Al-Si alloy cylinder of the first example and the second example is as follows:
Compared to the conventional combination with hard chrome plating, piston ring wear is reduced to about 1/5, and cylinder wear is reduced to about 1/2. It can also be seen that the wear resistance is superior to any combination with any comparison piston ring. From the above, it can be seen that the combination of the piston ring and cylinder according to the present invention has excellent wear resistance for engines using high lead gasoline as fuel.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a piston ring of the present invention. In the figure, 1: piston ring, 2: composite plating layer. FIG. 2 is a graph showing wear of piston rings and cylinders in actual machine tests.

Claims (1)

[Scope of Claims] 1. Silicon nitride with an average particle size of 0.5 to 10 μm is in the range of 5 to 30% by volume in the base layer of nickel-phosphorus alloy plating consisting of 0.2 to 10% by weight of phosphorus and the rest being nickel. A combination of a piston ring with a composite film layer dispersed in the sliding surface on its sliding surface and a cylinder made of hypereutectic Al-Si. 2. In the base layer of a nickel-cobalt-phosphorus alloy plating consisting of 0.2 to 10% by weight of phosphorus, 10 to 40% by weight of cobalt, and the remainder nickel, an average grain size of 0.5 to
A combination of a piston ring whose sliding surface has a composite film layer in which 10 μm silicon nitride is dispersed in a range of 5 to 30% by volume, and a cylinder made of hypereutectic Al-Si.