JPH0286946A - Combination of sliding surface layers - Google Patents

Abstract

PURPOSE:To reduce the extent of abrasion between both sliding surface layers as well as to make their seizure or binding hard to occur by having two types of these surface layers, where silicon nitride grains are dispersed in an alloy base consisting of phosphorus, cobalt and nickel at different rates, slidden with each other. CONSTITUTION:In reference to a combination of sliding surface layers, for example, the combination between a surface layer 13 of a piston ring 11 and a surface layer 15 of a cylinder 14 in an internal combustion engine, there is provided with a first surface layer where silicon nitride grains of 0.5-10mum in mean grain size are dispersed as much as 5-40 volume percentage in an alloy base composed of 2-15wt.% phosphorus, 10-40wt.% cobalt, and the rest of nickel in substance. Also there is provided with a second surface layer where the silicon nitride grains of 0.5-10mum in mean grain size are dispersed as much as 5-30 volume percentage in the alloy base composed of 12-15wt.% phosphorus, 10-40wt.% cobalt, and the rest of nickel in substance. Then, both these surface layers are slidden with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a combination of sliding surface layers, for example, a combination of a piston ring surface layer and a cylinder surface layer of an internal combustion engine.

In recent years, internal combustion engines have been designed to have high compression ratios and high speed rotation in order to increase their output, and as a result, sliding parts such as piston rings and cylinder liners are exposed to high temperatures and develop a lubricating oil film. becomes thinner, increasing the chance of metal-to-metal contact, which may cause abnormal wear or even seizure. Therefore, these sliding parts are required to have even higher wear resistance and seizure resistance than ever before.

In order to impart wear resistance to these sliding parts, hard chrome plating has been practiced for a long time. The hard chrome plating layer has high hardness and its own wear,
Although it has excellent wear resistance with less wear on mating sliding parts, it has the problem of being susceptible to seizure during sliding due to lack of oil retention. In particular, the combination of hard chrome plating layers causes severe seizure.

As a surface layer with improved seizure resistance, a nickel plating layer may be used in place of the hard chromium plating layer, but the wear resistance of the nickel plating layer is not satisfactory.

Therefore, in recent years, a composite plating layer in which wear-resistant particles, such as silicon carbide particles, are dispersed in a nickel base has been attracting attention as a plating layer with improved wear resistance.

In an attempt to improve the abrasion resistance of the composite plating layer, the amount of dispersion of wear-resistant particles is increased (and this results in abrasion of the mating sliding member and weakens the mechanical strength of the plating layer.On the other hand, It is conceivable to incorporate phosphorus into the nickel base of the above composite plating layer and increase the hardness of the plating layer through heat treatment to improve wear resistance and corrosion resistance. As the amount increases,
The base becomes brittle and the mechanical strength of the plating layer, especially the impact strength, decreases. If the mechanical strength of the plating layer decreases as described above, the plating layer will locally peel off during operation of the internal combustion engine, and this peeled off portion will turn into an abrasive material, causing wear to progress.

Although cast iron is widely used as a material for cylinders, cylinders made of aluminum alloys have recently been attracting attention due to the demand for lighter internal combustion engines and the resulting reduction in fuel consumption. Since aluminum alloy wears more easily than cast iron, aluminum alloy cylinders are used that have cast iron cylinder sleeves fitted onto the sliding surfaces.

This method increases the cost, does not achieve sufficient weight reduction, and does not sufficiently reduce fuel consumption. Therefore, it has been proposed that a nickel composite plating layer in which silicon carbide particles are dispersed is formed on the inner circumferential surface of an aluminum alloy cylinder, similar to a piston ring.

In this nickel composite plating layer, the silicon carbide particles form hard spots (referred to as the first sliding surface), and the nickel base is slightly abraded and recessed (referred to as the second sliding surface).
This second sliding surface provides oil retention and improves wear resistance.

However, since silicon carbide is extremely hard and has sharp crystal edges, it has the disadvantage that the mating piston ring wears out due to sliding. For example, when used in combination with a piston ring provided with a hard chromium plating layer or a nitrided layer on the outer peripheral surface G, the piston ring will wear out. Also,
When used in combination with a piston ring coated with silicon carbide dispersed nickel plating similar to the cylinder, seizure is likely to occur.

Thus, there is a desire for a combination of surface layers that causes less wear on both the piston ring and the cylinder and is less likely to cause seizure, but to date no preferred combination of surface layers that meets this demand has been found.

C1 Purpose of the Invention The present invention provides a combination of sliding surface layers in which both of the sliding surface layers that slide against each other have less wear and are less likely to seize even under severe sliding conditions. It is an object.

20 Structure of the Invention The present invention is characterized in that silicon nitride particles with an average particle size of 0.5 to 10 μm are contained in an alloy matrix consisting of 2 to 15% by weight of phosphorus, 10 to 40% by weight of cobalt, and the remainder substantially nickel. 40 volume%
a dispersed first surface layer and 2 to 15 wt% phosphorus, 10 to 4
A second surface layer in which silicon nitride particles having an average particle size of 0.5 to 10 μm are dispersed in an alloy matrix of 5 to 30 volume % and having an average particle size of 0.5 to 10 μm in an alloy base consisting of 0 weight % cobalt and the remainder substantially nickel slide against each other. It concerns the combination of dynamic surface layers.

Water 1 Functions and Effects of the Invention Except for cast iron, which contains graphite in its structure that acts as a lubricant, if similar materials are combined and slid together, wear and seizure will generally be severe.

However, the combination of surface layers based on the present invention has extremely good wear resistance and seizure resistance, even though the surface layers have the same composition.

The base constituting the surface layer and the dispersed particles dispersed in the base will be explained below.

As described later, nickel is used together with silicon nitride particles.
It generates 3Si and further generates Ni1P together with phosphorus, contributing to wear resistance and seizure resistance.

Cobalt dissolves in nickel to increase hardness, improve wear resistance and seizure resistance, and improve the crushing strength and fatigue strength of the surface layer. The above effect becomes remarkable when the cobalt content in the base is 10% by weight or more. Furthermore, if the cobalt content exceeds 40% by weight, the nickel content will be relatively low, and the amount of Ni, Si, NL, and P produced, which will be described later, will be small, and the mechanical strength of the surface layer will not be sufficiently improved. ,
As a result, the effect of improving wear resistance and seizure resistance becomes insufficient. Therefore, the cobalt content in the base should be 40% by weight or less.

Phosphorus increases the hardness of the base through heat treatment and contributes to improving wear resistance and seizure resistance. In other words, nickel and phosphorus react to form a Ni3P phase in the base, increasing the hardness of the base through a mechanism similar to the mechanical strength improvement caused by the precipitated phase during age hardening, thereby improving wear resistance. Contribute. In this way, the hardness of the base increases to 650 to 800 HMV, and in addition to the improved wear resistance and seizure resistance due to the improved wear resistance due to silicon nitride particles and the mechanical strength improvement of silicon carbide fibers, which will be described later. is further improved.

However, the amount of silicon nitride dispersed in the mating sliding surface layer to be combined with this surface layer is 5 to 30% by volume. When the amount of silicon nitride particles dispersed in both surface layers exceeds 30% by volume, wear of both surface layers increases. The heat treatment may be performed by heating to 400°C.

If the phosphorus content in the base is less than 2% by weight, the above effects will not be noticeable, and if it exceeds 15% by weight, the base will become brittle and the impact strength of the surface layer and adhesion to the base material will be poor. As a result, wear resistance and seizure resistance also deteriorate.

The silicon nitride particles are dispersed in the matrix and form hard spots, contributing to improved wear resistance and seizure resistance.

However, unlike silicon carbide, it does not have sharp end faces and has little effect on abrading the mating sliding surface. If the particle size is less than 0.5 μm, it is too fine and the effect of improving wear resistance and seizure resistance is not significant. If it exceeds 10.17 m, the particles act as an abrasive material and instead slide against each other. Wear of the mating material progresses. Furthermore, if the dispersion amount of particles is less than 5% by volume, the effect of improving wear resistance and seizure resistance will not be significant, and if it exceeds 40% by volume, the mechanical strength of the surface layer will decrease and the wear resistance will deteriorate. I come to do it. Therefore, 5 to 40 volume % of silicon nitride particles having a particle size of 0.5 to 10 μm are dispersed in the matrix. When silicon nitride particles are dispersed in the base, Ni and Si are generated on the particle surface by heat treatment at 400"C, which creates an adhesive effect between the base and the particles, further increasing the mechanical strength of the surface layer. If the heating temperature is too high, the above-mentioned adhesion effect will be reduced.For example, if heated to 600°C for 4 minutes, almost all of the silicon nitride particles will become NL3Si.Also, the above-mentioned wear resistance due to the silicon nitride particles will be improved. , the effect of improving seizure resistance is also lost.

To, Example The present invention will be explained in detail below.

A prismatic sample with a cross section of 5 M x 5 + u was taken from alloy tool steel 5KD61, which is used as a material for piston rings, and a 100 μm thick plating layer was formed on the square end surface of the sample via a nickel strike plating layer. After heat treatment at 400° C. for 5 hours, the surface of the plating layer was polished to obtain a test piece.

As a plating bath, a plating bath in which silicon nitride powder is suspended in an aqueous solution (plating solution) consisting of nickel sulfate, nickel chloride, cobalt sulfate, sodium hypophosphite, and boric acid is used, and the proportions of these and the silicon nitride powder are The composition and structure of the plating layer were changed by changing the particle size of the plating layer.

The temperature of the plating bath is 50-53℃, the current density is 8A/dt
J, the plating time was 2.5 hours, and the pH of the plating bath was set to a predetermined value between 2.0 and 3.0 depending on the bath composition.

As a sliding partner material for these test pieces, a circular plate of aluminum alloy A390 for cylinders (diameter 80n, thickness 1
The following plating layer was formed on the surface of 0fi) in the same manner as described above, and a polishing finish was applied.

This plating layer is formed in a base consisting of 30% by weight cobalt, 5% by weight phosphorus, and the remainder substantially nickel, with an average grain size of 0.
The plating layer has a structure in which 20% by volume of silicon nitride particles of 8 μm are dispersed.

The above-mentioned prismatic test piece and disc test piece were slid against each other, and a seizure test and a wear test were conducted. The test method is as follows.

The lump-wiping plating test device is schematically shown in FIG. 9 and FIG. 10, which is a side view taken along the line X-X in FIG.
Lubricating oil is applied to the center of the disk test piece 2, which is removably attached to the stator holder 1, from the back side through an oil filling hole 3. A pressing force P is applied to the stator holder 1 by a hydraulic device (not shown) at a predetermined pressure toward the right in the figure. A rotor 4 is disposed opposite to the disk test piece 2, and is rotated at a predetermined speed by a drive device (not shown). A test piece holder 4a attached to the end face of the rotor 4 with respect to the disc test piece 2 has four prismatic test pieces 5 concentrically arranged at equal intervals with the square end face as a sliding surface.
It is attached so that it can be removed individually and slidably relative to the disk test piece 2.

In such a device, a predetermined pressing force P is applied to the stator 1.
The surface layer (plating layer) 2a of the disk test piece 2 and the surface layer (plating layer) 5a of the prismatic test piece 5 are brought into contact with each other with a predetermined surface pressure, and the oil is slid from the oiling hole 3. The rotor 4 is rotated while lubricating the surface at a predetermined lubricating speed. The pressure applied to the stator 1 is increased stepwise at regular intervals, and the rotation of the rotor 4 causes the prismatic test piece 5 and the disc test piece 2 to be separated.
Torque T generated on the stator 1 due to friction with the stator (torque generated by frictional force) is applied to the rotor self via the spindle 6, and the change is read by the dynamic strain meter 8,
Record it on recorder 9. It is assumed that seizure has occurred when the torque T increases rapidly, and the quality of the seizure resistance is determined based on the magnitude of the increase.

The test conditions are as follows.

Friction speed = 8 m/sec Lubricating oil: 400a+j of dust (0.2 g/I! of type 3132 added (temperature 80°C)) to motor oil 5AE30, which was used in an actual machine test using leaded gasoline as fuel. ! / Win refueling contact pressure Crab test: 40kg/cIK at the start, then increased by 10kg/cJ every 3 minutes We conducted a test.

Friction speed is 5 n'L / 3B (, contact pressure is 100
kg/cd constant, the friction distance is 1100k, and the lubricating oil is engine oil S A E N130, which has been used in actual machine tests using leaded gasoline as fuel, and dust (type 3132) is added at 0.2 g/1. The temperature was 80° C. and the other test conditions were the same as in the above-mentioned baking test.

The amount of wear was measured as follows. Regarding the prismatic test piece, the test piece was removed after the test and the reduction in height due to wear was measured. Regarding the disk test piece, the depth of the annular wear scar caused by wear was measured.

The test results were as shown in FIGS. 4 to 7.

In the same manner as above, the surface layer of the prismatic specimen was reduced to 4.5% by weight.
It is assumed that 39% by volume of silicon nitride particles with an average particle size of 0.8 μm are dispersed in a nickel alloy base of phosphorus and 27% by weight cobalt, and the surface layer of the disk specimen is 5% by weight phosphorus and 30% by weight.
Dispersion amount of silicon nitride particles with an average particle size of 0.8 μm in a nickel alloy base of cobalt and balance nickel is 5 to 30% by volume.
A similar test was conducted by changing the value within the range of . The test results were as shown in FIG.

From Figures 4 to 8, the bases of the surface layers that slide against each other are
A nickel alloy containing 2 to 15% by weight of phosphorus and 10 to 40% by weight of cobalt is used, and the silicon nitride particles dispersed in these bases have an average particle size of 0.5 to 10 μm and a dispersion amount of 5 to 10 μm in one surface layer. It can be seen that good results can be obtained by setting the average particle diameter to 0.5 to 10 μm and dispersing amount to 5 to 30 volume % in the other surface layer.

Next, the results of an actual machine test in which a surface layer based on the present invention was formed on the outer circumferential surface of a piston ring and the inner circumferential surface of a cylinder litchi were assembled into an internal combustion engine will be described.

The first steel pressure ring has a nominal diameter of 78 m, a width of 1.5 m, and a thickness of 3.2 m. As a first step, the outer circumferential surface is subjected to conventional nickel strike plating to form a 108 m thick nickel plating layer. Next, as a second step, a nickel-cobalt-phosphorus composite plating layer having a thickness of 110 μm in which silicon nitride particles were dispersed was formed on the nickel plating layer using the bath composition and plating conditions shown in Table 1 below.

Table 1 Cylinder liner is aluminum alloy A3 with bore diameter 78M
90, and silicon nitride particles were dispersed on the inner peripheral surface of the bore according to the bath composition and plating conditions shown in Table 2 below, and the thickness was 120 μm.
A nickel-cobalt-phosphorus composite plating layer was formed.

Table 2 The amount of phosphorus in the matrix of this composite plating layer is 445% by weight, the amount of cobalt is 30% by weight, and the amount of silicon nitride particles dispersed is 15% by weight.
It was % by volume.

In the third step, the piston ring was heated to 400° C. for 1 hour to harden the base. As a result of this treatment, the hardness of the composite plating layer became 800 to 900 on the micro Vickers hardness.

Figure 1 is an enlarged sectional view of the piston ring, showing the steel base material 11.
A composite plating layer 13 is formed on the outer peripheral surface of the nickel plating layer 12 with a nickel plating layer 12 interposed therebetween. FIG. 2 is a sectional view of the cylinder liner, in which a composite plating layer 15 is formed on a base material 14 of aluminum alloy in the bore.

Figure 3 shows the composite plating layer of the piston ring (13 in Figure 1).
) is a micrograph (magnification: 400 times) showing the structure of. Gray silicon nitride particles are observed to be uniformly dispersed in the nickel alloy matrix. Note that the Nis P phase and Ni3St phase precipitated on the base by the heat treatment are extremely fine and are not visible in the photograph, but the existence of these phases has been confirmed by an X-ray diffraction test. The composite plating layer (15 in FIG. 2) of the cylinder liner also had substantially the same structure as that in FIG. 3.

4 cycles of the above piston ring and cylinder liner,
Assembled into a water-cooled 4-cylinder gasoline engine, a bench test was performed at 860 rpm, full load, and 100 hours using high-lead gasoline as fuel, and the amount of wear on the outer circumferential surface of the piston ring and the inner circumferential surface of the cylinder liner at top dead center was measured. did.

For comparison, the same cylinder liner as above was used, and the piston ring surface layer was a hard chromium plating layer, a nitrided layer formed on 17 chromium steel, or a nickel composite similar to the above with silicon carbide particles dispersed. A similar test was conducted on a combination of piston rings on which a plating layer was formed.

The test results were as shown in FIG. The amount of wear is expressed as a percentage of the amount of wear when using a piston ring with a hard chromium plating layer formed thereon. From the same figure,
The combination of the piston ring and cylinder liner of the example has significantly improved wear resistance compared to the comparative combination. When piston rings made of 17 chrome steel were used, the amount of wear was considerably reduced, but slight scuffing (seizure) occurred. On the other hand, in Examples, no trace of scuffing was observed.

From the above results, it can be seen that when the present invention is applied to a combination of a piston ring and a cylinder liner of an internal combustion engine, a compressor, etc., the durability is significantly improved. Further, the base material of the cylinder liner can be made of any material, and by using an aluminum alloy as the base material, it is possible to reduce the weight of the internal combustion engine. In this case, it is effective to make the cylinder block also made of aluminum alloy.

[Brief explanation of drawings]

The drawings all show embodiments of the present invention - Fig. 1 is an enlarged sectional view of a piston ring, Fig. 2 is a sectional view of a cylinder liner, and Fig. 3 shows a metallographic structure of the surface layer of the piston ring. 4, 5, 6, 7, and 8 are graphs showing the relationship between the composition of the surface layer and wear resistance or seizure resistance. FIG. 9 is a seizure test. FIG. 10 is a partially fragmented front view showing the main parts of the wear test device, FIG. 10 is a side view taken along the line X--X in FIG. 9, and FIG. 11 is a graph showing the results of the actual machine test. In addition, in the symbols shown in the drawings, 2...Disc test piece 5...Prismatic test piece 11...Piston ring base material 14...Cylinder liner base material 2a, 5a, 13 .15...Surface layer.

Claims (1)

[Claims] 1.2 to 15% by weight phosphorus, 10 to 40% by weight cobalt, and the balance substantially nickel in an alloy matrix with an average grain size of 0.
．． A first surface layer in which silicon nitride particles of 5 to 10 μm are dispersed in an amount of 5 to 40% by volume, and an alloy base consisting of 2 to 15% by weight of phosphorus, 10 to 40% by weight of cobalt, and the remainder substantially nickel with average particles dispersed therein. 5 to 3 silicon nitride particles with a diameter of 0.5 to 10 μm
A combination of sliding surface layers in which a second surface layer with 0 volume % dispersion slides on each other.