JP3570607B2 - Sliding member - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sliding member, and more particularly, to a sliding member containing no Pb (lead). INDUSTRIAL APPLICABILITY The sliding member of the present invention can be suitably used, for example, for a slide bearing or a bush for an internal combustion engine.
[0002]
[Prior art]
With the increase in the output of automobile engines, sliding bearings used for crankshafts, connecting rods, etc., are made of low carbon steel backing metal with kelmet alloys (Cu and Cu) having initial conformability and high compression / fatigue strength. Bearings lined with an alloy mainly composed of Pb) are often used.
[0003]
In this bearing, usually, a thin overlay layer is formed by electroplating or the like on the sliding surface with the mating material on the surface of the kelmet alloy. This is performed for the purpose of further improving the conformability with the counterpart material, and an alloy mainly composed of soft Pb and Sn is used for the overlay layer.
For the purpose of improving the corrosion resistance of kelmet, preventing the Sn in the overlay layer from diffusing into the kelmet alloy and preventing the overlay layer from deteriorating, for example, Ni or the like having a thickness of about several μm is formed on the kelmet surface. A plating process is performed to form an overlay layer on the plating layer.
[0004]
Further, as the above-mentioned plain bearing, an aluminum alloy bearing in which Sn, Pb and the like are alloyed with an Al base (see Japanese Patent Application Laid-Open No. 4-219523) is also often used.
[0005]
[Problems to be solved by the invention]
By the way, as a trend of material development in recent years, Pb-free is progressing. This development trend is no exception for sliding members such as the above-mentioned plain bearings.
However, Pb is important for satisfying the sliding characteristics in a sliding member such as a sliding bearing. Pb is particularly important in a high-load condition section such as a high-output engine because high sliding characteristics are required. Therefore, it has been extremely difficult to provide a sliding member having sufficient sliding characteristics without containing Pb in the sliding surface.
[0006]
The present invention has been made in view of the above circumstances, and provides a sliding member that does not contain Pb at least on the sliding surface and that can exhibit sliding characteristics equivalent to those containing Pb on the sliding surface. It is a technical problem to be solved.
[0007]
[Means for Solving the Problems]
The sliding member according to claim 1, wherein solving the above SL problem is composed of a base material, and a coating layer formed on the sliding surface of the mating member on the surface of the substrate, a sliding member for an internal combustion engine in, the coating layer contains no Pb, and, Sn, contain Bi and I n, Ri is Na from a g and inevitable impurities balance, the amount of Sn, Bi and in contained in the coating layer Is characterized in that Sn is 2 to 20% by weight, Bi is 5 to 20% by weight, and In is 2 to 10% by weight .
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
The sliding member of the present invention is a sliding member for an internal combustion engine , and includes a base material and a coating layer formed on a surface of the base material on a sliding surface with a mating member.
The type of the base material is not particularly limited, and can be appropriately selected from steel, cast iron, an iron-based sintered alloy, an aluminum alloy, a copper alloy, and the like, depending on the member to which the sliding member of the present invention is applied. And a composite material of these materials. However, it is preferable that this substrate also does not contain Pb. For example, when the sliding member of the present invention is applied to a sliding bearing for an internal combustion engine, a substrate formed by lining a Cu-Sn-based alloy layer on a steel back metal, or a substrate formed by an Al-Sn-Si-based alloy layer Etc. can be used.
[0011]
The coating layer is preferably a plating film formed by plating the surface of a substrate. This is because if the coating layer is a plating film, it is advantageous in terms of adhesion and film strength. As the plating treatment, in addition to wet plating such as electroplating and chemical plating, dry plating by a PVD method such as ion plating and sputtering can be employed. In addition, as a method of forming a coating layer on a base material, thermal spraying or the like can be adopted in addition to plating.
[0012]
The coating layer may be formed directly on the surface of the base material, but from the viewpoint of improving the bondability between the base material and the coating layer and the corrosion resistance of the base material, the formation of the intermediate layer on the surface of the base material is preferred. preferable. As the intermediate layer, a Ni plating layer, a Co plating layer, a Zn plating layer, or the like can be employed.
The thickness of the coating layer is preferably 1.0 to 30 μm. When the thickness of the coating layer is less than 1.0 μm, it is difficult to exhibit sufficient sliding characteristics. On the other hand, when the thickness is more than 30 μm, the adhesion decreases and the coating layer is easily peeled off from the substrate surface. More preferably, the thickness of the coating layer is 10 to 30 μm. When the thickness of the coating layer is 10 μm or more, it is advantageous in terms of securing necessary conformability and abrasion life.
[0013]
The coating layer contains Sn (tin), Bi (bismuth) and In (indium ), and the balance substantially consists of Ag (silver) and unavoidable impurities. The coating layer contains Pb. Not.
The coating layer made of such an Ag alloy has good fatigue resistance and abrasion resistance owing to its Ag-based properties of high ductility and high melting point, and is not too high in hardness due to the action of Sn, Bi or In, and has good conformability. And good lubricity and good seizure resistance.
[0014]
Therefore, the sliding member according to the present invention, in which the coating layer made of the Ag alloy is formed on the sliding surface with the mating material on the surface of the base material, is familiar even though at least the sliding surface does not contain Pb. The sliding properties of resistance, seizure resistance, wear resistance and fatigue resistance are improved.
Here, Sn contributes to the improvement of the initial conformability and wear resistance of the Ag alloy. If the content of Sn in the coating layer is less than 2% by weight, the hardness is high and the initial conformability is not sufficient. On the other hand, when the content of Sn exceeds 50% by weight, the melting point of the alloy is significantly reduced and softened at a high temperature, and the wear resistance becomes insufficient . Na us, the lower limit of the content of Sn in view of galling resistance is arbitrarily favored especially be 9 wt%.
[0015]
Bi contributes to the improvement of the initial conformability and fatigue resistance of the Ag alloy. If the content of Bi in the coating layer is less than 5% by weight, the hardness is high and the initial conformability is not sufficient. On the other hand, if the Bi content exceeds 50% by weight, the properties (ductility) possessed by Ag deteriorate, leading to a reduction in fatigue resistance . Na us, initial conformability of the lower limit of the content of Bi is in terms arbitrarily favored particularly be 10 wt%.
[0016]
In has the same effect as Sn, and in the above-mentioned coating layer, when the content of In is less than 2% by weight, the hardness is high and the initial conformability is not sufficient. It decreases and softens at high temperatures, resulting in insufficient wear resistance . Na us, the lower limit in terms of the initial conformability of the content of In is arbitrary it is particularly preferred to 7 wt%.
[0017]
To here, the content of Ag in the Ag alloy is preferable to ensure at least 50 wt% in order to ensure high ductility and high melting point characteristics by Ag group, Sn, Bi content and In in total If it exceeds 50% by weight, ductility and abrasion resistance decrease. Therefore, the total content of Sn, Bi and In is set to 50% by weight or less, Sn is set to 2 to 20% by weight, Bi is set to 5 to 20% by weight, and In is set to 2 to 10% by weight.
[0018]
Therefore, the sliding member of the present invention can be suitably used for a slide bearing or a bush for an internal combustion engine.
[0019]
【Example】
Hereinafter, the present invention will be specifically described with reference to examples.
[First embodiment]
A Cu-Sn alloy (Cu: 94.5% by weight, Sn: 5% by weight) test piece with a steel backing was prepared, and the surface of the Cu-Sn alloy of this test piece was prepared as shown below in Table 1. A coating layer having the chemical composition shown and having a thickness of 10 to 30 μm was formed by electroplating.
[0020]
[Table 1]
[0021]
( Reference Examples 1 to 3)
Using a plating bath having the composition shown in Table 2, electroplating was performed under the plating conditions shown in Table 3, thereby forming a coating layer made of an Ag-Sn alloy.
[0022]
[Table 2]
[0023]
[Table 3]
( Reference Examples 4 to 6)
Using a plating bath having a composition shown in Table 4, using a plating coating member as a cathode, and performing electroplating under the plating conditions shown in Table 5, a coating layer made of Ag was formed. Then, after Bi plating is further performed on this plating film, Bi is diffused into the plating film by a heat treatment (150 to 170 ° C., 30 to 60 minutes) to be treated to have a composition shown in Table 1. Thus, a coating layer made of an Ag—Bi alloy was formed.
[0024]
[Table 4]
[0025]
[Table 5]
( Reference Examples 7 and 8)
First, a coating layer made of Ag was formed by performing electroplating under the plating conditions shown in Table 4 using a plating bath having a composition shown in Table 3 as in Reference Examples 4 to 6, using the plating coating member as a cathode, and plating conditions shown in Table 4. did. Then, after further performing In plating on the plating film, In is diffused into the plating film by a heat treatment (150 to 170 ° C., 30 to 60 minutes) to be treated to have a composition shown in Table 1. Thus, a coating layer made of an Ag-In alloy was formed.
[0026]
( Reference Example 9)
First, a coating layer made of an Ag-Sn alloy was formed by performing electroplating under the plating conditions shown in Table 3 using a plating bath having the composition shown in Table 2 as in Reference Examples 1 to 3. Then, after further performing In plating on the plating film, In is diffused into the plating film by a heat treatment (150 to 170 ° C., 30 to 60 minutes) to be treated to have a composition shown in Table 1. Thus, a coating layer made of an Ag—Sn—In alloy was formed.
[0027]
( Reference Example 10)
First, a coating layer made of an Ag-Sn alloy was formed by performing electroplating under the plating conditions shown in Table 3 using a plating bath having the composition shown in Table 2 as in Reference Examples 1 to 3. Then, after Bi plating is further performed on this plating film, Bi is diffused into the plating film by a heat treatment (150 to 170 ° C., 30 to 60 minutes) to be treated to have a composition shown in Table 1. Thus, a coating layer made of an Ag—Sn—Bi alloy was formed.
[0028]
(Examples 11 and 12)
First, a coating layer made of an Ag—Sn—Bi alloy was formed in the same manner as in Reference Example 10.
Then, after further In plating is performed on the plating film, In is diffused into the plating film by heat treatment to be treated to have a composition shown in Table 1, thereby obtaining an Ag-Sn-Bi-In alloy. Was formed.
[0029]
(Comparative Example 1)
A coating layer made of a Pb-Sn alloy was formed by plating using a plating solution made of a borofluoride bath under conditions of a plating solution temperature of 20 to 30 ° C and a current density of ^{2 to} 5 A / dm ² .
(Comparative Example 2)
First, a Pb-Sn alloy plating treatment is performed using a plating solution composed of a borofluoride bath under the conditions of a plating solution temperature of 20 to 30 ° C. and a current density of ^{2 to} 5 A / dm ² , followed by In plating and heat treatment. Thus, a coating layer made of a Pb-Sn-In alloy was formed.
[0030]
(Comparative Example 3)
Using a plating bath having the composition shown in Table 4, using a plating coating member as a cathode, and performing electroplating under the plating conditions shown in Table 5, a coating layer made of pure Ag was formed.
(Comparative Example 4)
Using a plating solution composed of a fluorinated bath, plating was performed at a plating solution temperature of 20 to 30 ° C. and a current density of ^{2 to} 5 A / dm ² to form a coating layer composed of Sn.
[0031]
The coating layer according to Comparative Example 4 is an alloy layer that is currently used as an overlay layer for some slide bearings.
(Evaluation of hardness)
The hardness of the coating layers of Reference Examples 1 to 10, Examples 11 and 12, and Comparative Examples 1 to 4 was measured with a micro Vickers hardness tester. The results are shown in Table 6 and FIG.
[0032]
(Evaluation of friction and wear characteristics)
A friction and wear test was performed on test pieces composed of φ7 mm × L12 mm pins having the coating layers of Reference Examples 1 to 10, Examples 11 and 12, and Comparative Examples 1 to 4 formed on the sliding surfaces. The results are shown in Table 6 and FIGS. The test conditions are as follows.
(Evaluation of seizure resistance)
About the test piece which consists of a 30 mm x 30 mm, 2 mm thick plate (sliding surface 30 mm x 30 mm) in which the coating layers of Reference Examples 1 to 10, Examples 11 and 12, and Comparative Examples 1 to 4 are formed on the sliding surface. And a seizure test. The results are shown in Table 6 and FIG. The test conditions are as follows.
[0033]
[0034]
[Table 6]
[0035]
As is clear from Table 6 and FIGS. 1 to 4, the hardness of Comparative Examples 1 to 10 and Examples 11 and 12 was higher than Comparative Examples 1, 2 and 4, but Comparative Example 3 ( (Pure Ag plating). Reference Examples 1 to 10 and Examples 11 and 12 have a low coefficient of friction in spite of high hardness, and the friction coefficients of Reference Examples 1 to 10 and Examples 11 and 12 show values close to those of the comparative example. ing.
Further, in the case of the bases based on Pb of Comparative Examples 1 and 2, the coating layer was worn out during the seizure test and the seizure was caused with a low load, whereas Reference Examples 1 to 10 and Examples 11 and 12 were all It showed better seizure resistance than Comparative Examples 1 and 2, and also had much better wear resistance.
[0036]
In Comparative Example 3 of pure Ag plating, the overlay was very hard and excellent in abrasion resistance, but the conformability was insufficient and the seizure load was low . In Examples 11 and 12, both conformability and abrasion resistance were extremely high, and both compatibility and abrasion resistance were achieved.
[Second embodiment]
In this embodiment, the sliding member of the present invention is applied to a slide bearing for an internal combustion engine.
[0037]
As shown in FIG. 5, a steel back metal 1 is lined with a Cu—Sn alloy layer (Cu: 94.5% by weight, Sn: 5% by weight) 2 having an outer diameter of 48 mm and a thickness of 1.5 mm. Materials were prepared. A 1.5 μm thick Ni plating layer 2 ′ was formed on the surface of the Cu—Sn alloy layer 2 of the base material, that is, on the sliding surface with the counterpart material. The plating conditions at this time are: plating solution: watt bath, plating solution temperature: 50 ° C., current density: 6 A / dm ² .
[0038]
Then, the coating layer 3 was formed on the surface of the Ni plating layer 2 'in the same manner as in the first embodiment to produce a plain bearing.
A bearing unit test was performed on the case where the coating layers of Reference Examples 1 to 10, Examples 11 and 12, and Comparative Examples 1 to 4 shown in the first example were applied to the coating layer 3 of the above-mentioned plain bearing. FIG. 6 shows the result. The test conditions are as follows.
[0039]
Test equipment: Static load bearing tester Revolution: 5000 rpm (peripheral speed: 12.5 m / s)
Lubricating oil: SAE10W-30
Refueling amount: 0.1 liter / min Refueling temperature: 100 ° C
Counterpart material: carbon steel (S50C, Hv: 600, surface roughness: 0.8 μm Rz)
As is clear from FIG. 6, by forming the coating layer according to the present invention on the sliding surface of the plain bearing with the mating material on the surface of the plain bearing, Comparative Examples 1 and 2 based on Pb and Comparative Example 3 of pure Ag were performed. In addition, bearing performance (seizure characteristics) superior to pure Sn 4 could be exhibited.
[0040]
Further, in Comparative Example 3 of pure Ag, the conformability was poor, and seizure occurred before reaching the predetermined test conditions, and some of the samples could not be tested (FIG. 6 shows data of those successfully tested). On the other hand, in this example, there was no burn-in at the beginning of the test.
In addition, although the result in the case where the coating layer was formed by electroplating was shown in the above example, it was confirmed that the same result was obtained when the coating layer was formed by a vapor phase plating method such as PVD.
[0041]
【The invention's effect】
As described in detail above, the sliding member of the present invention does not contain Pb on the sliding surface, but can exhibit sliding characteristics equal to or higher than those containing Pb on the sliding surface.
[Brief description of the drawings]
FIG. 1 is a bar graph showing measurement results of hardness of a coating layer according to a first example.
FIG. 2 is a bar graph showing an evaluation result of a friction coefficient of a coating layer according to the first embodiment.
FIG. 3 is a bar graph showing an evaluation result of seizure resistance of a coating layer according to the first example.
FIG. 4 is a bar graph showing an evaluation result of abrasion resistance of a coating layer according to the first example.
FIG. 5 is a partial sectional view of a sliding bearing according to a second embodiment.
FIG. 6 is a bar graph showing evaluation results of seizure resistance of a coating layer according to a second example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Steel back metal, 2 ... Cu-Sn alloy layer, 2 '... Ni plating layer, 3 ... Coating layer

Claims (1)

A sliding member for an internal combustion engine, comprising a base material and a coating layer formed on a sliding surface of a mating material on the surface of the base material,
The coating layer contains no Pb, and, Sn, contain Bi and I n, Ri is Na from A g and inevitable impurities balance,
A sliding member comprising Sn, Bi and In in the coating layer, wherein Sn is 2 to 20% by weight, Bi is 5 to 20% by weight, and In is 2 to 10% by weight .