JPH0337478A - Rubbing member - Google Patents

Abstract

PURPOSE:To improve the durability by forming a nitride layer and a plating layer in order on the basic material of an iron base compound to compose a rubbing surface layer, and dispersing hard quality particles of a chromium oxide in a nickel base including cobalt and phosphorus of the plating layer. CONSTITUTION:On the surface of a square pillar test piece 5 which consists of a martensite type stainless steel (SUS304B), for example, a nitride layer 5b is formed, over which a nickel alloy comprex plating layer 5c is further formed at the thickness 1-20mum to compose a rubbing surface layer 5a. In this plating layer 5c, hard quality particles of the particle diameter less than 5mum which consists of a chromium oxide (Cr2O3) are dispersed at 5-30 vol.% in a nickel compound base including 10-50 wt.% of cobalt and 2-10wt.% of phospho rus. In such a way, a rubbing member with a good initial fitting property, generating a seizure scarcely, and with an excellent antiabrasive property and durability can be obtained.

Description

[Detailed description of the invention] B. Industrial application fields The present invention relates to sliding members, such as piston rings.

Prior Art In recent years, internal combustion engines have been made lighter, with higher compression ratios and faster rotation speeds required to increase output, and this has led to increased demands on sliding parts such as piston rings. Quality is becoming higher.

Conventionally, as a means to improve the durability of piston rings for internal combustion engines, a method of forming a hard chromium plating layer, a thermally sprayed surface layer, or a nitrided layer on the outer peripheral sliding surface has been adopted. Among these surface layers, the nitride layer in particular has been attracting attention as a surface layer of piston rings used under severe operating conditions because it exhibits excellent wear resistance. However, although the nitrided layer has excellent wear resistance, it does not have good initial conformability, and new piston rings may not have satisfactory seizure resistance at the initial stage of operation under severe operating conditions. However, as a result, there remains the problem that abnormal wear may occur.

C.1 Purpose of the Invention The object of the present invention is to provide a sliding member that has good initial fit, is less likely to seize, has excellent wear resistance, and exhibits excellent durability.

21 Structure of the Invention The present invention comprises a base material made of an iron-based alloy, a nitrided layer and a thickness of 1.
A plating layer of ~20 μm is formed in this order from the base material side to constitute a sliding surface layer, and the plating layer contains 10 to 50% by weight of cobal and 2 to 10% of phosphorus.
The present invention relates to a sliding member which is a plating layer having a structure in which hard particles made of chromium oxide and having a particle size of 5 μm or less are dispersed in an amount of 5 to 30% by volume in a nickel alloy matrix containing chromium oxide.

As the base material, it is desirable to use a material that has a nitrided layer on its surface that exhibits excellent wear resistance, such as 0.16 to 1.30% by weight carbon, 12 to 19% by weight
Steel materials containing chromium and steel materials containing a small amount of molybdenum and/or vanadium in addition to the above alloying elements are suitable.

Effects of the Invention In the present invention, in order to solve the above-mentioned problems of the nitrided layer, a plating layer having good initial conformability is formed on the nitrided layer.

In the sliding member based on the present invention, a thin plating layer with good initial conformability is formed on the nitrided layer with excellent wear resistance, and the good initial conformability of this plating layer prevents the occurrence of damage during the initial operation. Easy seizure is effectively prevented. If the thickness of the plating layer is less than 1 μm, the plating layer will disappear due to abrasion before the initial familiarity state is reached, and the above effects cannot be expected. On the other hand, when the plating layer becomes thicker than 20 μm, not only does the plating process cost increase, but the plating layer is likely to peel off during operation, and the wear resistance due to the underlying nitride layer cannot be exerted. By this time, wear has increased, and the piston ring in particular has a large blind spot and the airtightness of the piston ring has deteriorated. Therefore, the thickness of the plating layer is preferably in the range of 1 to 20 μm, particularly 1 to 10 μm.

The plating layer is a so-called composite dispersion plating layer in which hard particles made of chromium carbide are dispersed in a nickel alloy base containing cobalt and phosphorus. The base of the plating layer and the dispersed particles dispersed in the base will be explained below.

As will be described later, nickel produces Ni3P together with phosphorus and contributes to improving wear resistance and seizure resistance.

Cobalt dissolves in nickel to increase the hardness of the base, 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 50% by weight, the cost will increase, and the nickel content will be relatively low, resulting in a small amount of Ni3P, which will be described later, 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 is 10 to 50% by weight.

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 to Thus, the hardness of the base is 650-800 H,v
The wear resistance is further improved. Heat treatment is 400
Heat treatment by heating to 'C' 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 10 times the base will become weak and the impact strength of the surface layer and adhesion to the base material will deteriorate. As a result, wear resistance and seizure resistance also deteriorate.

The hard particles of chromium oxide are dispersed throughout 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.

When the particle size exceeds 5 .mu.m, the particles act as an abrasive material, and the abrasion of the sliding mating material progresses. Furthermore, if the amount of particles dispersed is less than 5% by volume, the effect of improving wear resistance and seizure resistance will not be significant, and if it exceeds 30% by volume, the mechanical strength of the plating layer will decrease and the wear resistance will deteriorate. At the same time, the mating sliding member also wears out. Therefore, 5 to 30 volume % of hard particles of chromium oxide having a particle size of 5 μm or less, preferably 0.3 to 5 μm are dispersed in the matrix.

Cr2O3 particles are suitable for the chromium oxide particles.

Since the sliding surface layer has the above-described layer structure, troubles such as seizure will not occur during the initial stage of operation due to the plating layer having good initial conformability on the surface. In addition, such a plating layer has excellent wear resistance close to that of a nitrided layer, so even if the surface plating layer disappears due to wear after sheet metal steady-state operation, the nitrided layer exposed on the surface due to this disappearance (layer with excellent abrasion resistance) shows excellent durability even under severe operating conditions.

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

Martensitic stainless steel 5US440B (0,7
5-0.95%C1≦1.0%Si1≦1.0%Mn,
≦0.040%P1≦0.030%S1≦0.60%N
i.

A nitrided layer is formed by a nitriding method, and a nickel alloy composite dispersion plating layer is formed on it under the following conditions,
A test piece was prepared by subjecting C to heat treatment for 1 hour. The thickness of the nitrided layer is 100 μm, and the thickness of the plating layer is 10 μm.

As a plating bath, a plating bath was used in which CrzOs powder was suspended in an aqueous solution (plating solution) consisting of nickel sulfate, nickel chloride, cobalt sulfate, sodium hypophosphite, and boric acid, and the proportions of these and the grains of Cr2O3 powder were By changing the diameter, the composition and structure of the plating layer were changed.

The temperature of the plating bath is 50-53°C, the current density is 8A/d
ml, plating time was 2.5 hours, and p)T of the plating bath was set to a predetermined value between 2.0 and 3.0 according to the bath specifications.

(Margin below) No. table No. table As a mating material that slides relative to these test pieces, Using cast iron FC25 for cylinder liner, the following I conducted a test like this.

The drag force 11 test device is schematically shown in FIG. 8 and FIG. 9, which is a side view taken along the line IX-IX in FIG. 8, and is removably attached to the stator holder 1. Lubricating oil is applied to the center of the mating disk test piece 2 from the back side through the 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 a square end face as a sliding surface, and four prismatic test pieces 5 are removable at equal intervals on a concentric circle. It is attached slidably with respect to 2.

In such a device, a predetermined pressing force P is applied to the stator 1.
The disk test piece 2 and the surface layer 5a of the prismatic test piece 5 are brought into contact with each other with a predetermined surface pressure, and the rotor 4 is oiled while lubricating the sliding surface from the oil fill hole 3 at a predetermined lubricating speed. Rotate. The pressure acting on the stator 1 is increased stepwise at regular intervals, and the rotation of the rotor 4 causes the prismatic test piece 5 to be
The torque Tq generated on the stator 1 due to the friction between the disk test piece 2 and the disk test piece 2 (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 and recorded on the recorder 9. let It is assumed that seizure has occurred when the torque Tq rapidly increases, and the quality of the seizure resistance is determined based on the magnitude.

The test conditions are as follows.

Friction speed: 8m/sec Lubricating oil: Motor oil #30 (temperature 80°C) at 40°C
Using the test equipment shown in Figures 8 and 9, the pressure was increased to 40 kg/CIfl at the start of the 0 mf/min refueling contact pressure test, and then increased by 10 kg/c every 3 minutes. A wear test was conducted under the test conditions.

Friction speed is 5m/5eC1 contact pressure is 100kg/Cf
The lubricating oil is motor oil #30 and dust (JI).
S2 type) was added at 0.2 g/l, and the 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. For the disk test piece, the depth of an annular wear scar caused by wear was measured.

The test results were as shown in FIGS. 2 to 5. Second
From Figures to Figure 5, the base of the surface layer 5a is 2 to 10% by weight.
The Crz03 particles, which are made of a nickel alloy of phosphorus and 10 to 50% by weight cobalt and dispersed in these bases, have an average particle size of 5 μm or less (particularly 0.3 to 5 μm) and a dispersion amount of 5 to 3 μm.
It can be seen that good results can be obtained by setting the amount to 0% by volume. In these figures, the test time for the wear test is 50
It is a minute.

Among the above prismatic test pieces, the base composition of the plating layer was 30% by weight cobalt, 5% by weight phosphorus, and the balance was nickel, and the surface layer had 10% by volume of Cr2O+ particles of 0.3 to 3 μm dispersed in this base. A micrograph (400x magnification) is shown in Figure 1. In the plating layer, gray Cr20i particles are observed to be uniformly dispersed in the nickel alloy base. In addition, Ni precipitated in the base by heat treatment,
The P phase is extremely fine and is not visible in the photograph, but
The existence of this phase has been confirmed by X-ray diffraction tests.

For comparison, a prismatic test piece with a 100 μm thick hard chromium plating layer formed on the same base material (Comparative Example 1), and a prismatic test piece with a 100 μm thick nitride layer formed on the same base material (Comparative Example 2)
and grain size 0.3~ in the base of the nickel alloy plating layer.
5 μm silicon nitride (Si: +N.

A similar test was conducted on a prismatic test piece (Comparative Example 3) in which particles were dispersed at 10% by volume. The test results of these comparative examples are shown in FIGS. 6 and 7 in comparison with the prismatic test piece shown in FIG. 1. In addition, in Fig. 6, the surface pressure at which seizure occurs is 10 kg/c.
The position between the +f1 scale marks indicates that seizure occurred while the contact surface pressure was increasing.

There is no significant difference in wear amount except for Comparative Example 1, but Example 1
．． In both cases, the burning resistance was significantly improved compared to each comparative example. In Comparative Example 3, the nickel alloy composite dispersion plating layer improves the seizure resistance compared to Comparative Example 1.2, but in the example, the seizure resistance is further improved compared to Comparative Example 3. This is because chromium oxide has higher hardness than silicon nitride, has a rounded particle shape, can be obtained with a uniform particle size, and has a low coefficient of friction.
The slope of the curve becomes smaller when exceeding
This is because the 10-am thick plating layer disappeared and a nitrided layer with better wear resistance was exposed on the sliding surface.

Next, the same sliding surface layer as described above (the same sliding surface layer as in the above embodiment) was formed on the outer peripheral sliding surface of the piston ring, and this piston ring was assembled into the engine. An example of an actual machine test (bench test) will be explained.

Figure 11 is a plan view of the piston ring in its free state;
2 is a right side view, and FIG. 10 is an enlarged sectional view taken along the line X--X of FIG. 11. In FIGS. 11 and 12, the perfect circular screw ring in the used state is shown by imaginary lines.

This piston ring has a nominal diameter of 86 mm and a width B of 1
．． 5nun, thickness T is 3.3mm, and eyesight C is 0.
It is a barrel face type pressure ring with a diameter of 25 mm and a free meeting distance of 10 mm, and the outer sliding surface has a base material 5 of martensitic stainless steel with a thickness of 100 μm as described above.
The sliding surface layer 5a is composed of a nitrided layer 5b having a thickness of m and a nickel alloy composite dispersion plating layer 5c having a thickness of 10 μm.

This piston ring is used as the second pressure ring, and the bore diameter is 8.
It was installed in a 6mm, 4-stroke, 6-cylinder gasoline engine and tested on a real machine for 200 hours at a rotational speed of 560 rpm and full load. As a result, it was my first time driving! From the initial stage to the end of the test, there was hardly any seizure or decrease in output, demonstrating extremely excellent durability. This good test result is due to the good initial conformability of the nickel alloy composite dispersion plating layer 5c and the nitrided layer
The excellent wear resistance of b prevents seizure, and the wear on the outer circumferential surface is small, resulting in an extremely small increase in blindness C.

On the other hand, in the piston ring of Comparative Example 1.2 in which the sliding surface layer was provided on the outer peripheral surface, seizure occurred during the initial stage of operation, making it impossible to continue the test.

Although the present invention has been described in detail above, the present invention can be applied to cylinder litchi and other sliding parts other than piston rings, and sliding parts other than internal combustion engines used under severe sliding conditions. It can be expected to exhibit good wear resistance and seizure resistance.

[Brief explanation of drawings]

The drawings all show examples of the present invention, and FIG. 1 is a micrograph showing the metal structure of a prismatic test piece, and FIGS. A graph showing the relationship between composition and wear resistance or seizure resistance. Figure 6 is a graph showing the results of the seizure test in comparison with a comparative example. Figure 7 is a graph showing the results of the wear test in comparison with the comparative example. Figure 8 is a partially fragmented front view showing the main parts of the seizure test and wear test equipment, Figure 9 is a side view taken along the line IX-IX in Figure 8, and Figure 10 is a diagram of the piston ring. FIG. 11 is a plan view of the piston ring, and FIG. 12 is a right side view thereof. In addition, in the symbols shown in the drawings, 2...... Disc test piece (opposite sliding test piece) 5
......Prismatic test piece 5a...Sliding surface layer 5b...Nitrided layer 5c...Plating layer It is.

Claims (1)

[Claims] 1. On the base material made of iron-based alloy, a nitrided layer and a thickness of 1 to 20
A plating layer of μm is formed in this order from the base material side, and these layers constitute a sliding surface layer, and the plating layer is
A sliding plated layer with a structure in which 5 to 30 volume % of hard particles made of chromium oxide and having a particle size of 5 μm or less are dispersed in a nickel alloy base containing 10 to 50 weight % of cobalt and 2 to 10 weight % of phosphorus. Element.