JP2651791B2 - Sliding member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding member, and more particularly to a sliding member provided with a base and a coating layer formed on the surface of the base.

[0002]

2. Description of the Related Art Conventionally, as a sliding member of this kind, a camshaft for an internal combustion engine having a coating layer made of an Fe plating layer formed on an outer peripheral surface of a journal portion of a cast iron base in order to improve seizure resistance is known. Are known.

However, under the current situation where the internal combustion engine tends to operate at high speed and high output, the conventional coating layer does not have sufficient oil retaining properties, that is, oil retaining properties, and has poor initial conformability, so that seizure resistance is low. There was a problem that the sex was poor.

In view of this, the present applicant has previously proposed a coating layer formed of a large number of columnar Fe crystals extending from the surface of the base and having a tip portion formed in a pyramidal shape and / or a truncated pyramid shape ( For example, see Japanese Patent Application No. 4-351333.

[0005] The coating layer having the above constitution has a sufficient oil retaining property and good initial conformability, and therefore has excellent seizure resistance.

[0006]

The present inventors have made various studies on the strength of the coating layer itself and the bonding strength with the substrate, and found that under more severe conditions, the coating layer has its own strength and the like. I clarified that there was some difficulty. This is because the columnar main portion of each columnar Fe crystal is grown so as to have substantially the same thickness between the substrate side and the coating layer surface side, so that the hardness of the coating layer, and hence the strength, is increased. It is substantially uniform in the thickness direction, and as a result,
When a crack is generated on the surface side of the coating layer, the crack immediately propagates to the substrate side of the coating layer.

In view of the above, the present invention provides a coating layer having an inclined structure in which the hardness is increased from the surface side to the substrate side, whereby the strength of the coating layer itself and the bonding strength with the substrate are reduced. It is an object of the present invention to provide the sliding member that can be improved.

[0008]

According to the present invention, there is provided a sliding member comprising a substrate and a coating layer formed on the surface of the substrate, wherein the coating layer has a large number of columnar metal crystals extending from the surface of the substrate. Then, the columnar metal crystal is grown by a large number of columnar crystals having a columnar main portion having a tapered shape so as to form at least a part of the surface of the coating layer, and a thick columnar main portion of the columnar crystal. And a large number of columnar crystals in which is suppressed.

[0009]

According to the above-mentioned structure, the amount of columnar metal crystals present on the substrate side of the coating layer is large and dense, so that its hardness is increased. On the other hand, on the surface side of the coating layer, the columnar metal crystals are columnar. Since the amount of the metal crystal is small and coarse, the hardness is low. The hardness on the surface side of the coating layer is substantially the same as when the columnar main portion grows to have substantially the same thickness from the substrate side to the surface side of the coating layer.
The abundance of the columnar crystals whose growth has been suppressed decreases almost gradually from the substrate side to the coating layer surface side.

Thus, the coating layer has a gradient structure in hardness. Therefore, an excessive load acting on the surface of the coating layer can be supported in the high-strength region on the substrate side while relaxing, so that the crack generation stress of the coating layer is increased and the height of the coating layer itself is increased. It is possible to increase the strength, and in turn, to improve the bonding strength with the base.

[0011]

1 and 2, a camshaft 1 for an internal combustion engine as a sliding member comprises a cast iron base 2 and a coating layer 4 formed on a peripheral surface of a journal 3 of the base 2 by plating. Have.

As shown in FIG. 3, the coating layer 4 has a large number of columnar metal crystals 5 extending from the outer peripheral surface of the journal portion 3.
The columnar metal crystal 5 forms at least a part of the sliding surface 4a with the surface of the coating layer 4, that is, the bearing member 6 (see FIG. 2), and in the illustrated example, the entire sliding surface 4a.
A large number of columnar crystals 7 (hereinafter, referred to as a columnar main body 7a) having a tapered shape.
A large number of columnar crystals 8 whose growth is suppressed by the thick columnar main body portion 7a of the completely grown columnar crystal 7 (hereinafter referred to as incompletely grown columnar crystal 8). And are included.

With this configuration, the columnar metal crystals 5 are more abundant and dense on the journal portion 3 side of the coating layer 4, so that the hardness is increased.
On the sliding surface 4a side, the abundance of the columnar metal crystals 5 is small and coarse, so that the hardness is low. In this case, the abundance of the incompletely grown columnar crystals 8 is determined by the sliding surface 4a from the base 2 side.
Almost gradually decrease toward the side.

Thus, the coating layer 4 has a gradient structure with respect to hardness. Therefore, an excessive load acting on the sliding surface 4a side of the coating layer 4 can be supported in the high-strength region on the journal portion 3 side while reducing the stress. As a result, the strength of the coating layer 4 itself can be improved, and thus the bonding strength with the journal portion 3 can be improved.

As shown in FIG. 4, the columnar metal crystal 5 has, for example, a body-centered cubic structure (bcc structure) and a (hhh) orientation with the (hh) plane facing the sliding surface 4a side with Miller index. And the abundance S of the (hhh) oriented metal crystal is set to S ≧ 40%. When the abundance S is set in this way, complete and incompletely grown columnar crystals 7, 8
Can be sufficiently present, and the coating layer 4 can have a gradient structure with respect to hardness.

As shown in FIGS. 5 and 6, the tip 7a of the fully grown columnar crystal 7, which is a (hhh) oriented metal crystal, has a pyramidal or truncated pyramid shape on the sliding surface 4a, in the illustrated example, a triangular shape. It is cone-shaped. Thus, when the abundance S of the (hhh) -oriented metal crystal is set as described above, the adjacent perfect growth type columnar crystals 7 exhibit a state in which they are biting each other. Of the fine peaks a and those peaks a
Since it has an intricate appearance composed of a number of fine valleys b in between and a number of fine valleys c due to the interpenetration of the peaks a, the oil retention of the coating layer 4 is improved. In addition, since the triangular pyramid-shaped tip portion 7a is worn preferentially, the initial conformability of the coating layer 4 is also improved. The seizure resistance of the coating layer 4 can be improved by such good oil retaining properties and initial conformability.

As shown in FIG. 7, the inclination of the (hhh) plane with respect to the imaginary plane 9 along the sliding surface 4a appears as the inclination of a triangular pyramid, so that the oil retaining property and the initial conformability of the coating layer 4 are not affected. give. Therefore, the inclination angle θ formed by the (hhh) plane with respect to the virtual plane 9 is set to 0 ° ≦ θ ≦ 15 °. In this case, the inclination direction of the (hhh) plane is not limited. When the inclination angle θ becomes θ> 15 °, the oil retaining property and the initial conformability of the coating layer 4 decrease. Note that the tip 7a of the complete growth type columnar crystal 7 may have a hexagonal pyramid shape on the sliding surface 4a.

As a metal crystal having a bcc structure, F
e, Cr, Mo, W, Ta, Zr, Nb, V, etc., or a crystal of a simple substance or alloy.

Table 1 shows the basic conditions for forming the coating layer 4 by electro-Fe plating.

[0020]

[Table 1] For energization, a method of gradually increasing the cathode current density from a low value CDs at the start of plating to a high value CDf at the end of plating is adopted. Thereby, the completely grown columnar crystals 7 and the incompletely grown columnar crystals 8 can be precipitated.

When the cathode current density is kept constant from the start of plating to the end of plating, columnar Fe crystals of substantially the same thickness are precipitated from the side of the journal 3 to the side of the sliding surface 4a.

(Hhh) The abundance S of the oriented Fe crystal is
It is controlled by the concentration, pH, and cathode current density of ferrous sulfate, particularly, the cathode current density at the start of plating.

Hereinafter, specific examples will be described.

As shown in FIG. 8, assuming the journal portion 3 of the camshaft 1, electric power is applied to the outer peripheral surface of a plurality of round bar-shaped substrates 2 made of cast iron (JIS FC25, chilled) and having a diameter of 26 mm and a length of 180 mm. By performing Fe plating, a coating layer 4 composed of an aggregate of Fe crystals was formed to obtain a sliding member. Each coating layer 4 has a thickness of about 50 μm and a width in the axial direction of the substrate of 28 mm.

Table 2 shows the conditions for the electro-Fe plating in Examples 1 to 8 of each coating layer 4.

[0026]

[Table 2] Table 3 shows the crystal morphology, the abundance S of each oriented Fe crystal, and the hardness in Examples 1 to 8, respectively.

[0027]

[Table 3] The abundance S was determined by the following method based on the X-ray diffraction diagrams of Examples 1 to 8 (the X-ray irradiation direction was perpendicular to the sliding surface). Describing Example 1 as an example, FIG. 9 is an X-ray diffraction diagram of Example 1, and the abundance S of each oriented Fe crystal was obtained from the following equation. For example, $ 1
The 10 ° oriented Fe crystal means an oriented Fe crystal in which the {110} plane faces the sliding surface. {110} oriented Fe crystal: S ₁₁₀ = {(I ₁₁₀ / IA)
₁₁₀ ) / T} × 100, {200} oriented Fe crystal: S ₂₀₀ = {(I ₂₀₀ / IA)
₂₀₀ ) / T} × 100, {211} oriented Fe crystal: S ₂₁₁ = {(I ₂₁₁ / IA)
₂₁₁ ) / T} × 100, {310} oriented Fe crystal: S ₃₁₀ = {(I ₃₁₀ / IA)
₃₁₀ ) / T} × 100, {222} oriented Fe crystal: S ₂₂₂ = {(I ₂₂₂ / IA)
₂₂₂ ) / T｝ × 100 where I ₁₁₀ , I ₂₀₀ , I ₂₁₁ , I ₃₁₀ , and I ₂₂₂ are the measured values (cps) of the X-ray reflection intensity of each crystal plane, and IA ₁₁₀ , IA ₂₀₀ , and IA ₂₁₁ , IA ₃₁₀ and IA ₂₂₂ are the X-ray reflection intensity ratios of each crystal plane in the ASTM card,
IA ₁₁₀ = 100, IA ₂₀₀ = 20, IA ₂₁₁ = 30,
IA ₃₁₀ = 12 and IA ₂₂₂ = 6. Further, T is T
_{= (I 110 / IA 110)} + (I 200 / IA 200) + (I
_{211 / IA 211) + (I} 310 / IA 310) + (I 222 /
IA ₂₂₂ ).

FIG. 10 is a micrograph showing the crystal structure of the cross section in Example 1, and (b) corresponds to an enlarged photograph of (a). In FIG. 10, many complete and incompletely grown columnar crystals are observed. These columnar crystals are (222) oriented Fe crystals in which the (hhh) plane, that is, the {222} plane faces the sliding surface. In this case, the abundance S of the {222} oriented Fe crystal is, as shown in Table 3 and FIG.
1%.

FIG. 11 is an X-ray diffraction diagram of Example 4, where
The abundance S of the 22 ° oriented Fe crystal is S = 40.1% as shown in Table 3 and FIG.

FIG. 12 shows the change in hardness in Examples 1 and 5. In the case of Example 1, the shorter the distance from the outer peripheral surface of the base 2, the higher the hardness. Therefore, it can be seen that Example 1 has an inclined structure with respect to hardness. In the case of Example 5, since it is composed of columnar crystals of substantially the same thickness, there is almost no change in hardness. Examples 2 to 4
As in Example 1, it has an inclined structure with respect to hardness.
8 has a uniform hardness as in Example 5.

FIG. 13 shows the results of a crack initiation test for Examples 1-8. In the figure, points (1) to (8) correspond to Examples 1 to 8, respectively. This test shows that the coating 4 has a diameter of 13
0mm, 18mm axial width steel (JIS SCM420,
A large roller made of a carburizing treatment) is brought into pressure contact with a load of 0 to 600 kgf to rotate the base 2 and the large roller in opposite directions at 2000 rpm.
Oil was supplied at a temperature of 50 ° C. at a supply rate of 100 ml / min.

As is apparent from FIG. 13, Examples 1 to 4
Since the abundance S of the {222} -oriented Fe crystal is set to S ≧ 40% and the columnar crystals 7 and 8 are completely and incompletely grown, the columnar crystals have a gradient structure with respect to hardness. 8 has a higher crack initiation stress. This effect is due to the existence rate S of {222} oriented Fe crystals as in Examples 1 to 3.
By setting S ≧ 50%.

As shown in FIG. 14, the columnar metal crystal 5 has a face-centered cubic structure (fcc structure), and the (3hh) plane is directed toward the sliding surface 4a by the Miller index (3hh).
h) Oriented metal crystals are also included, and the (3hhh) oriented metal crystal abundance S is set to S ≧ 40%. When the abundance S is set in this manner, the complete and incompletely grown columnar crystals 7 and 8 can be sufficiently present, and the coating layer 4 can have an inclined structure with respect to hardness.

As shown in FIG. 15, the tip 7a of the fully grown columnar crystal 7, which is a (3hhh) oriented metal crystal, has a pyramidal or truncated pyramid shape on the sliding surface 4a, in the illustrated example a quadrangular pyramid shape. Make Therefore, when the abundance S of the (3hhh) -oriented metal crystal is set as described above, the same sliding surface 4a as that shown in FIGS. Has oil retention and initial adaptability.

As shown in FIG. 16, the inclination of the (3hhh) plane with respect to the imaginary plane 9 along the sliding surface 4a appears as the inclination of a quadrangular pyramid, so that the oil retaining property and initial adaptability of the coating layer 4 are not affected. give. Therefore, the (3hhh) plane is a virtual plane 9
Is set to 0 ° ≦ θ ≦ 15 °. In this case, the inclination direction of the (3hhh) plane is not limited. When the inclination angle θ becomes θ> 15 °, the coating layer 4
Oil retention and initial conformability are reduced.

As a metal crystal having the fcc structure, P
b, Ni, Cu, Pt, Al, Ag, Au and the like, or a crystal of a simple substance or alloy.

For example, Tables 4 and 5 show the basic conditions for performing the electric Ni plating process.

[0038]

[Table 4]

[0039]

[Table 5] In this case, the abundance S of each oriented Ni crystal is determined by the X-ray diffraction pattern (the X-ray irradiation direction is perpendicular to the sliding surface) as described above.
Is obtained from the following equation based on Note that, for example, $ 11
1｝ oriented Ni crystal means an oriented Ni crystal with the {111} plane facing the sliding surface 4a side. {111} oriented Ni crystal: S ₁₁₁ = {(I ₁₁₁ / IA)
₁₁₁ ) / T} × 100, {200} oriented Ni crystal: S ₂₀₀ = {(I ₂₀₀ / IA)
₂₀₀ ) / T} × 100, {220} oriented Ni crystal: S ₂₂₀ = {(I ₂₂₀ / IA)
₂₂₀ ) / T} × 100, {311} oriented Ni crystal: S ₃₁₁ = {(I ₃₁₁ / IA)
₃₁₁ ) / T｝ × 100 where I ₁₁₁ , I ₂₀₀ , I ₂₂₀ , and I ₃₁₁ are measured values (cps) of the X-ray reflection intensity of each crystal plane.
A ₁₁₁ , IA ₂₀₀ , IA ₂₂₀ , and IA ₃₁₁ are X-ray reflection intensity ratios of each crystal plane in the ASTM card, and IA ₁₁₁ = 1
00, IA ₂₀₀ = 42, IA ₂₂₀ = 21, IA ₃₁₁ = 2
0. Further, T is T = (I ₁₁₁ / IA ₁₁₁ ) +
(I ₂₀₀ / IA ₂₀₀ ) + (I ₂₂₀ / IA ₂₂₀ ) + (I
₃₁₁ / IA ₃₁₁ ).

As the plating treatment, in addition to the electroplating treatment, for example, a PVD method, a CVD method, a sputtering method, and an ion plating method, which are vapor phase plating methods, can be mentioned. Conditions for performing W and Mo plating by the sputtering method include, for example, an Ar pressure of 0.2 to 1 Pa and an Ar accelerating power.
The direct current is 0.5 to 1.5 kW, and the base material temperature is 80 to 300 ° C. Conditions for performing Pt and Al plating by a sputtering method include, for example, an Ar pressure of 0.8 to 1 Pa, an Ar acceleration power of 200 to 1000 W DC, and a base material temperature of 80 to 30.
0 ° C. Conditions for performing W plating by the CVD method include, for example, a raw material WF ₆ , a gas flow rate of 2 to 15 cc / mi.
n, chamber pressure 50-300 Pa, base material temperature 3
00-600 ° C. Conditions for performing Al plating by the CVD method include, for example, the raw material Al (C
H ₃ ) ₃ , gas flow rate 1 to 10 cc / min, chamber pressure 50 to 300 Pa, and base material temperature 300 to 600 ° C.

Examples of the sliding member to which the present invention is applied include the following components for internal combustion engines.

Piston (skirt, land, ring groove), piston ring, piston pin, connecting rod, crankshaft, bearing metal, oil pump rotor, oil pump rotor housing, spring (end face), spring seat, spring retainer, cotter , Rocker arm, roller bearing outer case, roller bearing inner case, valve stem, valve face, hydraulic tappet, water pump rotor shaft, pulley,
Gears, transmission shafts, clutch plates, washers, bolts (seats, screws).

[0043]

According to the present invention, by forming the coating layer as described above, the coating layer can have a gradient structure with respect to the hardness, whereby the strength of the coating layer itself and the strength with respect to the substrate can be improved. A sliding member with improved bonding strength can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of a camshaft.

FIG. 2 is a cross-sectional view of a main part of a journal section in a camshaft.

FIG. 3 is an enlarged sectional view of a main part of a coating layer.

FIG. 4 is a perspective view showing a body-centered cubic structure and its (hhh) plane.

FIG. 5 is a perspective view of a main part of a coating layer.

FIG. 6 is a sectional view taken along line 6-6 in FIG. 5;

FIG. 7 is an explanatory diagram showing an inclination of a (hhh) plane in a body-centered cubic structure.

FIG. 8 is a front view showing an embodiment of the sliding member.

FIG. 9 is an X-ray diffraction diagram of an example of a coating layer.

10A is a micrograph showing a crystal structure of a cross section of an example of a coating layer, and FIG. 10B is an enlarged photograph of FIG.

FIG. 11 is an X-ray diffraction diagram of another example of the coating layer.

FIG. 12 is a graph showing the relationship between the distance from the outer peripheral surface of the base in the coating layer and the hardness.

FIG. 13 is a graph showing the relationship between the abundance of {222} oriented Fe crystals in the coating layer and the crack initiation stress.

FIG. 14 is a perspective view showing a face-centered cubic structure and its (3hhh) plane.

FIG. 15 is a plan view of a main part of a coating layer.

FIG. 16 is an explanatory diagram showing the inclination of the (3hhh) plane in the face-centered cubic structure.

[Explanation of symbols]

 2 Base 4 Coating layer 5 Columnar metal crystal 7 Columnar crystal (complete growth type columnar crystal) 7a Columnar main part 8 Columnar crystal (incomplete growth type columnar crystal)

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kenji Hirose 1-4-1, Chuo, Wako-shi, Saitama Pref. Honda Technical Research Institute Co., Ltd. (56) References JP-A-6-248490 (JP, A) JP-A Heisei JP-A-5-25684 (JP, A) JP-A-5-25684 (JP, A) JP-A-5-17897 (JP, A) JP-A-5-9789 (JP, A) JP-A-61-31734 (JP, A) A) JP-A-54-28233 (JP, A)

Claims (3)

(57) [Claims] 1. A sliding member comprising a substrate (2) and a coating layer (4) formed on the surface of the substrate (2), wherein the coating layer (4) extends from the surface of the substrate (2). It has a large number of columnar metal crystals (5), and the main columnar portion (7a) has a tapered shape in the columnar metal crystals (5) so as to form at least a part of the surface of the coating layer (4). A large number of columnar crystals (7) and a thick columnar main body (7) of the columnar crystals (7);
A sliding member comprising: a large number of columnar crystals (8) whose growth has been suppressed by a). 2. The columnar metal crystal (5) is a (hh) oriented metal crystal having a body-centered cubic structure and a (hhh) plane facing the surface of the coating layer (4) with a Miller index. The abundance S of the (hhh) oriented metal crystal is S ≧ 4
The sliding member according to claim 1, which is 0%. 3. The columnar metal crystal (5) is a (3hhh) oriented metal crystal having a face-centered cubic structure and a (3hhh) plane facing the surface of the coating layer (4) with a Miller index. The abundance S of the (3hhh) oriented metal crystal is S ≧
The sliding member according to claim 1, which is 40%.