JP2001124082A - Sliding member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sliding member with superior frictional wearing characteristic under various working conditions such as a dry frictional condition, in-oil or an oil lubricating condition. SOLUTION: This sliding member provided with the eutectoid plating including solid lubricant dispersed therein, such as the Ni-P composite plating including PTFE particles dispersed therein, is heated under an atmosphere not including oxygen to prevent a surface from being hardened by the production of an oxidation layer, and to inhibit the increase of the coefficient of friction caused by the oxidation layer, whereby a sliding member stable in the frictional wearing characteristic can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding member having excellent wear resistance and durability.

[0002]

2. Description of the Related Art A sliding member used under non-lubricated conditions particularly requires a reduction in a coefficient of friction on a sliding surface and an improvement in wear resistance. For this reason, conventionally, sliding members having a resin coating for reducing the coefficient of friction have been used as sliding members which are to be brought into sliding contact without lubrication.

[0003]

The above-mentioned conventional sliding members have not been sufficiently satisfactory in terms of reducing the coefficient of friction and improving the wear resistance.

[0004] Therefore, eutectoid plating in which a solid lubricant is dispersed on the sliding surface, for example, Ni-
A sliding member having a P composite plating layer is used.
Most of them are baked for the purpose of increasing the hardness of the plating layer. However, since calcination is usually performed in the atmosphere, a hard oxide layer is formed on the surface layer and the surface is discolored. When the oxide layer is worn by the initial wear due to sliding, hard wear powder is generated, and the wear powder (hard particles) generated with the increase in the number of times of sliding causes abrasive wear. Therefore, the wear of the non-oxidized layer having a lower hardness than the oxidized layer is promoted, and the durability of the sliding member is deteriorated.

The present invention has been made for the purpose of solving such a problem, and an object of the present invention is to provide a sliding member which has a low friction coefficient and is maintained in a stable state and has excellent wear resistance. To provide.

[0006]

According to the present invention, a sliding member in which a base material is subjected to eutectoid plating in which a solid lubricant is dispersed, such as PTFE-dispersed Ni-P composite plating, is applied to an atmosphere containing no oxygen. By baking underneath, curing of the surface due to formation of an oxide layer is suppressed.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, PTFE dispersed Ni-
Although an experimental example is shown with respect to P composite plating, the present invention is not limited to this and can be applied to other eutectoid plating, and the eutectoid method is not limited to electrolytic plating and electroless plating. As the solid lubricant, graphite, molybdenum disulfide and the like can be used in addition to PTFE.

[0008] PTFE dispersed Ni-P composite plating is
It can be formed by plating the base material with a Ni-P plating solution in which FE particles are appropriately dispersed. The plating may be performed by simple electroless chemical plating until a plating layer having an arbitrary thickness is obtained. It is desirable for the sliding member to have a thickness of about 20 μm in order to obtain sufficient hardness. The ratio of the PTFE particles in the composite plating layer is 10 to
25 vol%. This is because the effect of reducing the friction coefficient cannot be obtained at 10 vol% or less, and the strength decreases at 25 vol% or more.

After the plating treatment, the mechanical properties of the plated film are improved by heat-treating the PTFE-dispersed Ni-P composite plating. In this case, as a useful method of creating an oxygen-free atmosphere inside the firing furnace, firing in an atmosphere in which a hydrogen / nitrogen mixed gas containing several percent of hydrogen is introduced. After the firing, the state is gradually cooled to room temperature to prevent oxidation of Ni due to firing.

FIG. 1 is a schematic view of the formed composite plating. In the composite plating, as shown in FIG.
The i-P matrix 2 is formed on the base material 3 so as to be rolled up. PTFE dispersed in Ni-P matrix
Reduces the friction coefficient on the sliding surface stably for a long time. Further, the adhesion of the sliding surface can be suppressed by PTFE adhering to the surface.

Next, the measurement results of the friction coefficient of the sliding member thus formed will be described below.

FIG. 2 is a schematic view of the friction tester used. A test piece 4 of 50 mm × 50 mm × 5 mm with composite plating was fixed to the apparatus, and a steel ball of φ3 / 8 inch (JI
The test was carried out using an indenter 5 under an applied load 6 from above. The frictional force when the sample moves in the direction of the arrow is measured by the frictional force detector 7. Test load: 1 kgf, friction speed: 3 m / mi
n was measured without lubrication in the air.

The prepared composite plating specimens are as follows:
Is a point. (Example 1) PTF having a thickness of 20 μm was placed on the sliding surface of a test piece.
An E25 vol% dispersed Ni-P composite plating layer was formed and baked at 350 ° C. for 45 minutes in an oxygen-free atmosphere. (Example 2) PTF having a thickness of 20 μm was formed on the sliding surface of a test piece.
An E10 vol% dispersed Ni—P composite plating layer was formed, and baked at 350 ° C. for 45 minutes in an oxygen-free atmosphere. (Comparative Example 1) PTF having a thickness of 20 µm was placed on the sliding surface of a test piece.
An E10 vol% dispersed Ni—P composite plating layer was formed, and baked at 350 ° C. for 45 minutes in an oxygen atmosphere. (Example 3) An electroless Ni-P layer having a thickness of 20 µm was formed on the sliding surface of a test piece, and baked at 350 ° C for 45 minutes in an oxygen-free atmosphere. (Comparative Example 2) An electroless Ni-P layer having a thickness of 20 µm was formed on the sliding surface of a test piece, and baked at 350 ° C for 45 minutes in an oxygen atmosphere.

[0014] In Example 3 and Comparative Example 2, a measurement was attempted in order to more accurately evaluate the change in frictional characteristics due to the formation of an oxide layer, although it did not contain PTFE.

The coefficient of static friction of the sliding surface of each test piece,
The measurement results of the dynamic friction coefficient are as follows. In Example 1, the static friction coefficient was 0.17 and the dynamic friction coefficient was 0.05.
It is. In Example 2, the coefficient of static friction is 0.20 and the coefficient of dynamic friction is 0.08. In Comparative Example 1, the static friction coefficient is 0.24 and the dynamic friction coefficient is 0.11. In Example 3, the static friction coefficient was 0.28 and the dynamic friction coefficient was 0.12.
It is. In Comparative Example 2, the static friction coefficient was 0.61 and the dynamic friction coefficient was 0.24.

The coefficient of friction of Example 1 in which firing was performed in an oxygen-free atmosphere with the highest PTFE content was the smallest for both the static friction coefficient and the dynamic friction coefficient. Further, by comparing Example 2 with Comparative Example 1 in which the PTFE content was 10 vol% but different firing atmospheres, it was confirmed that the friction coefficient was increased by the oxide layer formed during firing. In the comparison between Example 3 in which only the electroless Ni-P coating containing no PTFE and Comparative Example 2, the difference in the friction coefficient is more clearly shown. It is apparent from this that firing in an oxygen-free atmosphere has the effect of reducing the coefficient of friction.

The test pieces of Example 2 and Comparative Example 1 were subjected to 10,000 reciprocal sliding tests with carburized and hardened steel (load: 3 k).
gf, moving speed: 3 m / min, moving distance: 20 mm), and the specimen after sliding was observed with a scanning electron microscope.
As a result, in Comparative Example 1 in which an oxide layer was formed, it was confirmed that wear progressed more rapidly than in Example 2 due to the state of wear marks. When the respective Vickers hardnesses (Hv) were measured, Comparative Example 1 was Hv650 in Example 2, whereas Hv650 was in Example 2.
Is Hv710. It can be said that the surface layer portion of the plating is hardened by the formation of the oxide layer. It is known that degradation due to oxidation limits the intended use of the material. In use as a sliding member, hard abrasion powder generated when the oxidized layer is worn causes abrasive wear, promotes wear of the non-oxidized layer, and reduces the durability of the sliding member. According to the present invention, it is possible to provide a sliding member having a low friction coefficient and excellent wear resistance by suppressing the formation of an oxide layer of the composite plating.

[0018]

As described above, according to the present invention, PTF
The sliding member subjected to the Ni-P composite plating in which the E particles are dispersed is subjected to a heat treatment in an atmosphere in which a hydrogen / nitrogen mixed gas containing several percent of hydrogen flows, thereby forming an oxide layer. A sliding member that prevents deterioration can be provided.
By using this sliding member on the sliding surface of machine tools, etc.,
A highly reliable device with reduced friction coefficient and improved wear resistance can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic partial sectional view of a sliding member of the present invention.

FIG. 2 is a schematic view of a friction test device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 PTFE particle 2 Composite plating layer 3 Base material 4 PTFE dispersed Ni-P composite plating test piece 5 SUJ steel ball indenter 6 Weight 7 Friction force detector

Claims (3)

[Claims] 1. A sliding member having eutectoid plating in which a solid lubricant is dispersed on a sliding surface, wherein the eutectoid plating is
A sliding member characterized by firing in an oxygen-free atmosphere. 2. The sliding member according to claim 1, wherein the eutectoid plating layer is a Ni—P composite plating in which polytetrafluoroethylene (PTFE) particles are dispersed. 3. The method according to claim 1, wherein the firing in the oxygen-free atmosphere is an atmosphere in which a hydrogen / nitrogen gas containing several percent of hydrogen flows into the firing furnace. Sliding member.