JPH0243838B2 - - Google Patents

Description

[Detailed description of the invention]

B. Technical Field of the Invention The present invention relates to a piston ring having a dispersed plating layer. B. Prior art and problems For example, piston rings that slide at high speed are widely used with hard chrome plating to increase wear resistance, but this plating takes a considerable amount of time to process. In addition, there were problems with wear resistance, seizure resistance, corrosion resistance, etc. when used in engines using high lead gasoline as fuel or engines with high negative liquid. In order to solve the above problems, nitrides, carbides,
Composite plating methods that disperse wear-resistant particles such as oxides are attracting attention. This is called composite plating or dispersion plating, and by appropriately selecting the type, size, and amount of dispersed particles, a coating with excellent wear resistance, seizure resistance, and corrosion resistance can be created. It has already begun to be used in cylinders and sliding members such as piston rings. However, although the material itself has excellent wear resistance, there was a need to improve the wear resistance of the opposing material. C. Purpose of the invention The present invention solves the problems of conventional composite plating,
The present invention provides a piston ring having a coating phase on its sliding surface that has excellent wear resistance, seizure resistance, and corrosion resistance. D. Structure of the Invention The present invention provides a piston ring 1 as shown in FIG.
5 to 30 wear-resistant particles 4 with a particle size of 10 μm or less are added to the sliding surface of the alloy base 3, which has a composition of 10 to 40% by weight of cobalt, 2 to 15% by weight of phosphorus, and 50 to 88% by weight of nickel. The present invention relates to a piston ring having a composite plated layer in which 5 to 35% by volume of lubricating particles 5 having a particle size of 20 μm or less are dispersed. E. Functions and Effects Phosphorus contained in the alloy base increases the hardness of the alloy base when subjected to thermosetting treatment, and exhibits excellent effects in improving wear resistance and corrosion resistance. If the phosphorus content in the alloy matrix is less than 2%, the effect will be small;
Moreover, if it exceeds 15%, the base becomes brittle and the impact strength and adhesion of the film deteriorate. The phosphorus content is preferably 2 to 15% by weight. Addition of cobalt improves the seizure resistance and corrosion resistance of the alloy matrix, as well as the crushing fatigue strength. The amount of cobalt contained in the alloy matrix is 10% by weight
If the amount is less, the above effect will not be obtained significantly, and
There is no significant change in the effect beyond 40% by weight.
Therefore, the amount of cobalt is preferably 10 to 40% by weight. Wear-resistant particles dispersed in the alloy matrix include alumina, silicon nitride, silicon carbide zirconia,
Metal nitrides, metal carbides, metal oxides, etc. such as titanium carbide are used. The particle size of wear-resistant particles dispersed in the base is 0.3μ
If the amount of dispersion is less than m or less than 5% by volume, the effect of improving wear resistance will be small. On the other hand, the particle size resistance is 10μm, and the amount of dispersion is
If it exceeds 30% by volume, the strength of the film will decrease. Therefore, the average particle size of wear-resistant particles is 0.3 to 10μ.
m, the amount of dispersion is preferably 5 to 30% by volume, preferably the average particle diameter is 0.5 to 5 μm, and the amount of dispersion is preferably 15 to 25% by volume. By dispersing hard particles as described above as wear-resistant particles, the wear resistance of piston rings can be improved.
Seizure resistance is improved. In the present invention, in addition to the wear-resistant particles described above, lubricating particles are also dispersed in the alloy matrix. Here, as the lubricant particles, for example, a solid lubricant having a cleavage property and a low coefficient of friction is used. As typical examples, particles of molybdenum disulfide, graphite fluoride, boron nitride, graphite, mica, Teflon, etc. are used, and the piston ring according to the present invention reduces wear of the mating material by dispersing these lubricating particles. is also extremely small. The particle size of the lubricating particles dispersed in the base is 0.5 μm or less, depending on the lubricant used, and the amount of dispersion is 5% by volume.
Below that, the effect as a lubricant is low. If the particle size exceeds 20 μm and the amount of dispersion exceeds 35% by volume, the strength of the base will decrease, causing the film to peel off during operation. Therefore, the particle size of the lubricating particles is preferably 0.5 to 20 μm, and the dispersion amount is preferably 5 to 35% by volume, and preferably the particle size is 1 to 10 μm.
m, the amount of dispersion is preferably 10 to 30% by volume. The total amount of wear-resistant particles and lubricating particles dispersed in the alloy base is preferably 40% by volume or less in view of the strength of the coating. Example: As a first step, a steel specimen made of piston ring steel material (SKD-61) with a tip end surface of 5 mm x 5 mm was plated with a nickel strike plating method to a thickness of 5 μm on the sliding surface side of the tip using the usual nickel strike plating method. As a second step, a 120 μm thick nickel-cobalt phosphorus plating layer containing dispersed silicon nitride and boron nitride was formed using the electroplating conditions shown in Table 1. Ta. Separately, the thickness was measured using the electroless plating conditions shown in Table 1 on a test piece made of the same material as in the electroplating method above.
A nickel-cobalt-phosphorus plating layer containing 100 μm of silicon nitride and boron nitride was formed.
In addition, in electroless nickel plating, the adhesion of the plating layer is good, so the nickel strike plating step was omitted. In the third step, each test piece obtained by each of the above methods was heat-cured at 370° C. for 1 hour. Table 2 shows the composition of the plating layer of the obtained test piece and the results measured with a micro-Vickers hardness meter.

【table】

[Table] Next, the wear resistance test and seizure test of the sliding surface according to the present invention will be explained. The test was conducted using a lidar type abrasion tester shown in FIGS. 3 and 4. The outline is that the stator holder 1 is made of cast iron FC25, which is used as a cylinder material, etc., and the sliding surface 2 is
A disc 3 with a honed finish is removably attached, and lubricating oil is supplied to the center of the disc through an oil fill hole 4 from the back side. In the figure, a predetermined pressing force is applied toward the right side. 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, The 5 x 5 mm square tip ends of the test pieces each having been subjected to a predetermined surface treatment come into contact with the sliding surface 2 of the disk 3, and are 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 amount of wear between the test piece 7 and the stator disk 3 is measured when the test piece 7 slides on the disk 3 by a predetermined sliding distance. Evaluate wear resistance. Also, when the rotor 5 is rotated, the test piece 7 and the disk 3
Torque F is generated in the stator holder 1 as shown in the figure due to wear between the stator holder 1 and the load cell 9. This torque F is applied to the load cell 9 through the spindle 8, and the change in torque F due to the change in pressing force is measured by the dynamic strain meter 10. Assuming that seizure occurred when the reading torque F suddenly increased, the seizure resistance was evaluated using the pressing force at that time. In addition to the test piece obtained in the above example, test piece 7 also included hard chrome plating, which is generally used for abrasion-resistant surface treatment, molybdenum spraying, which has excellent abrasion resistance and scuff resistance, and this material. Similar tests were conducted on silicon nitride-dispersed nickel-cobalt phosphorus plating in which the lubricating particles were removed from the electroplating bath composition of the example. a Wear test Using engine oil SAE No. 30 after use in an actual machine test using leaded gasoline as a lubricant and adding 0.2 g/l of dust (JIS type 2) to oil at a temperature of 80°C, While applying a hydraulic pressure of 100 kg/cm ² to the stator holder 1 toward the rotor, the friction speed of the test piece 7 was increased from 3 to 5 m/cm2.
sec, and the rotor 5 was rotated until the sliding distance reached 100 km. The test results are shown in Table 3 below.

[Table] b Seizure test Use the same lubricant as that for the wear test.
Stator holder 1 has hydraulic pressure first toward the rotor side.
Apply a pressing force of 40 kg/cm ² and rotate the rotor 5 for 3 minutes at a friction speed of 8 m/sec, then increase the pressing force to 50 kg/cm ²
In this way, the pressing force was increased in steps of 10 kg/cm ² and held for 33 minutes each, and the change in torque F was recorded with the dynamic strain meter 10 via the load cell 9. The contact surface pressure was determined from the pressing force when the torque increased and was used as the surface pressure at which seizure occurred. The test results are shown in Table 4 below.

[Table] Actual machine test Next, the composite plating of the present invention was applied to the steel first pressure ring with a nominal diameter x width x 3.3 mm, and it was assembled into a 4-cylinder water-cooled engine with a bore diameter of 86 mm. A high-speed durability test was conducted for 100 hours at 6200 rpm and full load using high-lead gasoline as fuel, and the wear on the first pressure ring sliding surface and the inner peripheral surface of the cast iron (FC25) cylinder liner was measured. The composition of the composite plating layer applied to this first pressure ring is 25% by weight of cobalt, 7.5% by weight of phosphorus, and 20% by volume of silicon nitride with an average grain size of 0.8 μm in a base of nickel-cobalt-phosphorus alloy with the remainder being nickel.
A dispersion of 15% by volume of boron nitride with an average particle size of 3 μm was used. As a comparative example, the same hard chromium plating, molybdenum thermal spraying, and silicon nitride dispersed nickel-cobalt-phosphorus plating layer excluding lubricating particles as used in the above examples were formed on the sliding surface at the first pressure. Rings were also tested. The test results are shown in Figure 2. Table 3, Table 4, and Figure 2 show that the Nikkei-cobalt-phosphorus composite plating layer of the present invention has superior abrasion resistance and seizure resistance compared to conventional plating layers, and also does not wear the mating material. It is understood that it is suitable as a surface treatment layer for piston rings.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the plating layer of a first pressure ring showing an example of the present invention obtained by electroplating, in which 2 is a nickel strike plating layer, 4 is a hard particle, and 5 is a lubricant particle. shows. Figure 2 is a diagram showing the wear results of the actual machine test, Figures 3 and 4 are the lidar wear test machine, where 1 is the stator holder, 2 is the sliding surface, and 3 is the lidar wear test machine.
is a disc, 4 is a lubrication hole, 5 is a rotor, 6 is a
The figure shows a test piece holder, 7 is a test piece, 8 is a spindle, 9 is a load cell, and 10 is a dynamic strain meter.

Claims (1)

[Claims] 1 A piston ring with a composite plating layer formed on the sliding surface, the composite plating layer containing cobalt 10 to 40
Weight%, Phosphorus 2-15% by weight, Nickel 50-88% by weight
5 to 30 wear-resistant particles such as metal nitride, metal carbide, metal oxide, etc. with a particle size of 0.3 to 10 μm are added to the alloy matrix.
Volume % and 5 to 35 volume % of lubricating particles with a particle size of 0.5 to 20 μm of solid lubricants such as molybdenum disulfide, graphite fluoride, boron nitride, graphite, Teflon, etc.
Dispersed piston rings.