JPH0390583A - Combination of sliding surface layers - Google Patents

Abstract

PURPOSE:To provide a combination of surface layers minimizing wear in both sliding surfaces and practically causing no seizure by using surface layers in which specific amounts of chromium oxide grains are dispersed in an Ni alloy matrix containing P and Co as respective sliding surfaces. CONSTITUTION:A primary surface layer of sliding parts has a structure in which chromium oxide grains of 0.5-10mum average grain size are dispersed by 5-40vol.% into an alloy matrix consisting of, by weight, 2-15% P, 10-40% Co, and the balance essentially Ni. A secondary surface layer has a structure in which chromium oxide grains of 0.5-10mu average grain size are dispersed by 5-30vol.% into an alloy matrix consisting of, by weight, 2-15% P, 10-40% Co, and the balance essentially Ni. A combination in which the primary surface layer and the secondary surface layer mentioned above are allowed to slide mutually. By applying the above combination, e.g., to a combination of a piston ring and a cylinder liner in internal combustion engine, compressor, etc., the durability of the combination can be improved.

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.

B. Prior art 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 have 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.

If the amount of dispersed wear-resistant particles is increased in an attempt to improve the abrasion resistance of the composite plating layer, the mating sliding member will be abraded and the mechanical strength of the plating layer will become weaker. On the other hand, it is conceivable to incorporate phosphorus into the nickel base of the composite plating layer and increase the hardness of the plating layer through heat treatment to improve wear resistance and corrosion resistance. As the phosphorus content 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 9M alloy have recently been attracting attention due to the need to reduce the weight of internal combustion engines and thereby reduce 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 worn to form concave portions (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 having a hard chromium plating layer or a nitrided layer on the outer circumferential surface, the piston ring will wear out. Furthermore, 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.

C.6 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 chromium oxide 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. a first surface layer dispersed at 40% by volume and 2 to 15% by weight, % by weight phosphorus, 10
A second surface layer in which 5 to 30 volume % of chromium oxide particles having an average particle size of 0.5 to 10 μm are dispersed in an alloy matrix consisting of ~40 weight % cobalt and the remainder substantially nickel slides on each other. It concerns the combination of sliding surface layers.

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, in the combination of surface layers based on the present invention, although the surface layers have the same composition, wear resistance,
Extremely good seizure resistance.

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

Nickel produces Ni and P together with phosphorus, and contributes 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, the amount of Ni and P produced will be small, and the mechanical strength of the surface layer will not be sufficiently improved. abrasive,
The effect of improving 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 N1zP phase in the matrix, which increases the hardness of the matrix through a mechanism similar to the mechanical strength improvement caused by the precipitated phase during age hardening, thereby contributing to improved wear resistance. do. In this way, the hardness of the base increases to 650 to 800 H□, and the wear resistance and seizure resistance are further improved in addition to the improvements in wear resistance and seizure resistance due to the chromium oxide particles described later. However, the amount of chromium oxide particles dispersed in the mating sliding surface layer to be combined with this surface layer is 5 to 30% by volume.

When the amount of chromium oxide particles dispersed in both surface layers exceeds 30% by volume, wear of both surface layers increases. Heat treatment is 400
``C heat treatment is sufficient.

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, resulting in poor impact strength of the surface layer and poor adhesion to the base material. As a result, wear resistance and seizure resistance also deteriorate.

The chromium oxide 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.
When the particle size exceeds 10 um, the particles act as an abrasive material, and the wear of the sliding mating materials progresses. In addition, the amount of particles dispersed is 5% by volume.
If it is less than 40% 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 actually deteriorate. Therefore,
5 to 5 chromium oxide particles with a particle size of 0.5 to 10 μm are added to the base.
Disperse at 40% by volume. Chromium oxide particles include Crz
03 particles are preferred.

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

A prismatic sample with a cross section of 5 mm x 5 mm 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 was performed at 0'C for 5 hours, the surface of the plating layer was polished to obtain a test piece.

The plating bath is an aqueous solution (plating solution) consisting of nickel sulfate, nickel chloride, cobalt sulfate, sodium hypophosphite, and boric acid, containing Cr, 0. A plating bath in which powders were suspended was used, and the composition and structure of the plating layer were changed by changing the blending amount and the particle size of the Cr2O3 powder.

The temperature of the plating bath is 50-53°C, the current density is 8A/d
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 ξ alloy A390 for cylinders (diameter 80 mm, thickness 1
The following plating layer was formed on the surface of 0mm) in the same manner as above, and polished.

This plating layer is formed in a matrix consisting of 30% by weight cobalt, 5% by weight phosphorus, and the remainder substantially nickel, with an average particle size of 2.5% by weight.
This is a plating layer with a structure in which 20% by volume of Oam Cr, O, and particles 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 outline of the scouring 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 load cell 7 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: Dust (0.2 g/l of JIS type 2 added (temperature 80°C)) to motor oil 5AE30, which was used in an actual machine test using leaded gasoline as fuel, at 400 m/min. Refueling contact pressure 40kg/cIII at the start of the crab test, increasing rate 1 by 10kg/ctfl every 3 minutes thereafter.Using the test equipment shown in Figures 9 and 10, wear tests were conducted under the following test conditions. I did it.

Friction speed is 5 m/sec, contact pressure is 100 kg/C
The IJ is constant, the friction distance is 100 kin, and the lubricating oil is engine oil S A E Na30, which has been used in an actual machine test with leaded gasoline as fuel, and dust (JIS2+f).
f1) to 0.2 g//! The temperature of the added material is 80°C.
1. Other test conditions were the same as in the seizure test described above.

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 volume % of Cr, 03 particles with an average particle size of 0.8 μm are dispersed in a nickel alloy base of phosphorus and 27 weight % cobalt, and the surface layer of the disk test piece is 5 weight % phosphorus and 30 weight % cobalt. , Cr2O with an average grain size of 2.0 μm in a nickel alloy matrix with the balance being nickel.

A similar test was conducted by varying the amount of particles dispersed in the range of 5 to 30% by volume. 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 weight percent phosphorus and 10 to 40 weight percent cobalt is used, and the Cr, O, and particles dispersed in these bases have an average particle size of 0.5 to 10 μm in one surface layer.
It can be seen that good results can be obtained by setting the amount of dispersion to 5 to 40% by volume, and in the other surface layer, setting the average particle size to 0.5 to 10 μm and the amount of dispersion to 5 to 30% by volume.

Next, a description will be given of the results of an actual machine test in which a surface layer according to the present invention was formed on the outer peripheral surface of a piston ring and the inner peripheral surface of a cylinder liner, and these were assembled into an internal combustion engine.

As a first step, the outer circumferential surface of the first pressure ring made of steel with a nominal diameter of 78 mm, width of 1.5 am, and thickness of 3.2 mm is subjected to regular nickel strike plating to form a 10 μm thick nickel plating layer. did. Next, as the second step, the following
A 110 μm thick nickel-cobalt-phosphorus composite plating layer in which CrzO+ particles were dispersed was formed on the nickel plating layer using the bath composition and plating conditions shown in the table.

Table 1 The amount of phosphorus in the matrix of this composite plating layer is 4.5% by weight, the amount of cobalt is 30% by weight, the amount of Cr2O, and the amount of particles dispersed is 1.
It was 5% 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.

The cylinder liner is aluminum alloy A with a bore diameter of 78 mm.
390 and had a thickness of 12 mm with CrzO3 particles dispersed on the inner peripheral surface of the bore according to the bath composition and plating conditions shown in Table 2 below.
A 0 am nickel-cobalt-phosphorus composite plating layer was formed.

(Left below) Figure 1 of Table 1 is an enlarged cross-sectional view of a piston ring.
Composite plating J via nickel plating layer 12 on the outer peripheral surface of
ii13 is formed. 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 colored CrzOz particles are observed to be uniformly dispersed in the nickel alloy matrix. Although the Ni3 phase precipitated on the base by heat treatment is extremely fine and not visible in the photograph, the existence of these phases was 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 8,600 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 the same Nirakel composite as 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. In contrast, no trace of scuffing was observed in the examples.

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 metal 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...... Square column test piece 11... Piston ring mother Material 4...
...Cylinder liner base material 2a. 5a, 3, 5... surface layer.

Claims (1)

[Claims] 1. 2-15% by weight phosphorus, 10-40% by weight cobalt,
A first surface layer in which chromium oxide particles having an average particle size of 0.5 to 10 μm are dispersed in an alloy matrix whose balance is substantially nickel in an amount of 5 to 40% by volume, and 2 to 15% by weight of phosphorus, 10 to 40% by weight
A second surface layer in which 5 to 30 volume % of chromium oxide particles having an average particle size of 0.5 to 10 μm are dispersed in an alloy matrix consisting of % by weight cobalt and the remainder substantially nickel slides against each other. Combination of surface layers.