KR20020075958A - High temperature Anti-wearing Grease Composition Containing Solid Lubricant - Google Patents

Abstract

PURPOSE: Provided is a grease composition having wearing resistance under severe temperature condition, particularly ultra high or ultra low temperature and containing a solid lubricant. CONSTITUTION: The grease composition contains 60 to 99 wt.% of grease and 0.1 to 40 wt.% of solid lubricant having a diameter of 1 to 50 micrometer, which is particularly a dichalcogenide solid lubricant and is produced by mixing at least a transition metal selected from the group consisting of tungsten(W), molybdenum(Mo), niobium(Nb), thallium(Ta), titanium(Ti), vanadium(V) and chromium(Cr) with at least a group 6A metal selected from the group consisting of sulfur(S), selenium(Se) and tellurium (Te) in a mole ratio of 1:2.2 to 1:3.0, and heating the mixture at 800 to 1000 deg. C for 2 hours or less.

Description

High temperature Anti-wearing Grease Composition Containing Solid Lubricant

The present invention relates to a grease composition for improving the lubricity and wear resistance of various sliding part surfaces, in particular, by adding and mixing a solid lubricant having excellent lubricity and wear resistance to the grease under harsh temperature conditions, even at low temperatures, high temperatures and high loads. A high temperature wear resistant grease composition containing a solid lubricant that reduces friction and wear on sliding surfaces.

Friction means resistance to sliding of sliding solid contact parts, and lubricant is a medium to reduce the resistance, which prevents heat generation, damage and abrasion of the active surface material and improves mechanical efficiency. Lubricants form a thin film of oil between two solids to support the charge and simultaneously separate the two surfaces to perform gamma action. Generally, lubricants injected and applied between sliding surfaces include liquid lubricants, greases, and solid lubricants.

Among the lubricants described above, grease is a sticky glue of mineral oil mixed with soap. It has less leakage than liquid lubricating oil, has a high adsorption power, and has a self-sealing function. it's difficult. Because of these characteristics, it is frequently used when there is a risk of loss due to leakage, or when there is a risk of contact with dust or corrosive gas. In particular, it is widely used as a lubricant for various friction parts that may be contaminated by oil, and is used in all fields such as transportation machinery such as automobiles, aircrafts, and ships, and equipment machinery such as steel and paper, construction machinery, and electrical equipment. Is being applied. In addition, according to the high performance and high efficiency of various mechanical devices and facilities, the use environment of grease requires operation in harsh environments such as high temperature and high load, and accordingly, the type and required characteristics of grease are further refined.

However, greases have a high torque at low temperatures and a low torque at high temperatures (above 200 ℃), which reduces the load bearing capacity of the oil film. There is a problem that the effect drops sharply. In addition, under high loads, there is a problem in that direct contact between sliding members occurs due to grease leakage between friction surface layers, causing high friction and wear due to fusion and the like.

The present invention has been made to solve the above problems, and an object thereof is to mix and add a solid lubricant to provide a grease composition applicable at high temperature and high load operating conditions.

That is, an object of the present invention is to provide a grease composition having high temperature and low temperature lubrication, abrasion resistance, and extreme pressure by appropriately mixing a solid lubricant having excellent lubrication characteristics and excellent wear resistance in grease at harsh temperature conditions compared to grease.

1 is a view schematically showing a state of a grease composition in which a solid lubricant is added and mixed according to the present invention.

2 is a view schematically showing the state of the grease composition and the solid lubricant layer formed on the surface of the sliding site after a certain time when the grease composition according to the present invention is applied to various sliding sites.

3 is an enlarged cross-sectional view of the solid lubricant layer formed in FIG. 2.

4A and 4B are optical micrographs showing wear traces after a four-hole wear test of a conventional grease and a grease composition containing a WS ₂ solid lubricant according to the present invention, respectively.

<Explanation of symbols for the main parts of the drawings>

10: grease 20: solid lubricant powder

25: solid lubricant layer 27: WS ₂ coating layer

30: sliding member surface

In order to realize the above object, in the present invention

A high temperature wear resistant grease composition containing a solid lubricant comprising 60 to 99.9 weight percent grease and 0.1 to 40 weight percent solid lubricant is added.

In particular, it is preferable that the solid lubricant is a dichalcogenide-based solid lubricant, and specifically, a solid lubricant prepared according to the method disclosed in Korean Patent No. 287971, registered on November 13, 2000, may be used. . That is, at least one transition metal element selected from the group consisting of tungsten (W), molybdenum (Mo), niobium (Nb), thallium (Ta), titanium (Ti), vanadium (V) and chromium (Cr) and sulfur ( S), selenium (Se), and at least one group 6A element selected from the group consisting of (te) (Te) of about 800 to 1000 ℃ while stirring uniformly in a high pressure atmosphere in a molar ratio of 1: 2.2 to 3.0 What is obtained by heat-treating for 2 hours or less in a temperature range can be used. As the solid lubricant, tungsten sulfide (WS ₂ ), molybdenum sulfide (MoS ₂ ) or a mixture thereof may be particularly preferably applied.

Such solid lubricants should be added in the range of 0.1 to 40% by weight, which is not preferable if the amount of addition thereof is less than 0.1% by weight, which is not desirable to form a sufficient solid lubricant layer on the surface of the friction substrate. This is because it is difficult to apply grease. In addition, the particle size of the solid lubricant may be preferably applied in the range of 1 to 50㎛.

As the grease applicable to the present invention, almost all greases such as general grease, rolling bearing grease, automotive grease, concentrated oil grease, heavy duty grease, high temperature grease, gear compound grease, mixtures thereof, etc. can be applied without exception. .

Solid lubricants form a thin layer on the rubbing landmarks to improve shearing properties and prevent direct contact between surface sublayers to enhance abrasion resistance, as well as environments where liquid lubricants cannot be used. It has the advantage of lubricating effect under the conditions of cryogenic or high temperature.

Materials that can be used as solid lubricants include graphite having a layered or lamellar structure, MoS ₂ and WS ₂ . WS ₂ is more resistant to oxidation and graphite than MoS ₂ , and has excellent lubricating properties in harsh environments. WS ₂ has a lower coefficient of friction than graphite from the lowest temperature of -273 ℃ to the highest temperature of 650 ℃. The present invention can be more preferably applied to the present invention because it can be used without modification of the treatment surface.

The dichalcogenide-based inorganic material preferably applied in the present invention refers to a compound in which a Group 4B or Group 5B transition metal and a Group 6A element are bonded, as disclosed in Korean Patent No. 287971. It has a layered structure similar to graphite. In the layer, group 4B or 5B transition metal and group 6A elements have strong covalent bonds, and weak van der Waals bonds between group 6A elements between layers. Therefore, when a shear force is applied, a slip occurs between the layers having weak van der Waals bonds and the lubricating effect is exhibited.

1 schematically shows a state of a grease composition obtained by adding and mixing a solid lubricant to grease according to the present invention. It can be seen that the solid lubricant powder 20 is uniformly distributed in the grease 10.

Figure 2 schematically shows the state of the grease composition and the solid lubricant layer formed on the surface of the sliding site after a certain time when the grease composition according to the present invention is applied to various sliding sites. The grease 10 and the solid lubricant powder 20 are uniformly mixed on the sliding member surface 30, and the solid lubricant layer 25 is formed in contact with the sliding member surface 30. have.

3 is an enlarged view of a cross section in which the WS ₂ solid lubricant layer is formed, and it can be seen that the WS ₂ coating layer 27 has a layered crystal structure.

When the solid lubricant having such a layered crystal structure forms the solid lubricant layer 25 on the surface of the sliding portion and is subjected to shearing force, it is easily slid by weak van der Waals bonds between layers in the crystal to exhibit lubricating properties. In addition, the solid lubricant layer 25 improves durability by preventing direct contact with the sliding portions in contact with each other, and also has a lubricating effect under cryogenic and high temperature conditions.

Hereinafter, the present invention will be described in more detail with reference to specific examples. The tungsten disulfide used in the examples was prepared according to the method disclosed in Example 1 of Korean Patent No. 287971, registered November 13, 2000.

<Example 1>

In order to prepare a grease composition containing a tungsten disulfide (WS ₂ ) solid lubricant, lithium mineral oil-based grease (grease for general rolling bearings, manufactured by River River Korea) and tungsten disulfide (average particle size 12㎛) Using nano), 10 wt% tungsten disulfide based on grease and grease was weighed into a plastic container, and then mixed with a stirrer for 2 hours to prepare a grease composition containing a solid lubricant.

<Example 2>

The grease composition was prepared in the same manner as in Example 1 except that tungsten disulfide was added in an amount of 20% by weight instead of 10% by weight.

<4-ball wear test method>

In order to evaluate the grease composition and the wear resistance characteristics of the grease on the sliding part, a lithium mineral oil-based grease containing no solid lubricant, the grease composition according to Examples 1 and 2 were applied, and the three fixtures into which the grease was injected ( 1/2 inch steel ball) was rotated under a 40kg load under a condition of 1,200 rpm and 1 hour, and the wear diameter of the fastener was measured.

<4 ball wear test result>

The results of the four ball wear test (standard: ASTM D 2266) for the grease composition containing the conventional grease and the solid lubricant are shown in Table 1. Table 1 shows that the average wear diameter of the conventional grease when 20 wt% of the WS ₂ solid lubricant is added is 0.4 mm, and the wear resistance is improved by 20% compared to 0.51 mm, which is the average wear diameter when lubricated by grease alone. You can check it.

Four ball wear test results for grease compositions containing conventional grease and WS ₂ solid lubricant ingredient Average wear diameter (mm) Lithium mineral oil grease 0.51 Lithium mineral oil grease + 20 wt% WS ₂ solid lubricant 0.40 Lithium mineral oil grease + 10 wt% WS ₂ solid lubricant 0.44

4A and 4B are optical micrographs of wear traces after a four-hole wear test, FIG. 4A shows a case where a conventional grease is applied, and FIG. 4B shows a grease having 20 wt% of a WS ₂ solid lubricant according to Example 2 It is about the case where a composition is applied. From the figure it can be seen that the wear diameter of Figure 4b is much smaller, which demonstrates that the wear resistance of the present invention is improved.

As described above, according to the present invention, a grease composition having improved lubricity, abrasion resistance, and extreme pressure resistance in harsh temperature conditions can be prepared by adding and mixing a solid lubricant with grease. This is because the solid lubricant serves to prevent direct contact of the sliding parts in contact with each other, thereby improving durability and also having a lubricating effect under cryogenic and high temperature conditions, thereby enabling application of the grease composition under severe lubricating conditions.

Although the present invention has been described above according to the embodiments, it will be apparent to those skilled in the art that modifications and adaptations of various solid lubricants are possible without departing from the spirit of the present invention.

Claims (6)

A wear-resistant grease composition comprising a solid lubricant comprising 60 to 99.9 weight percent grease and 0.1 to 40 weight percent solid lubricant. The grease composition of claim 1, wherein the solid lubricant is a dichalcogenide-based solid lubricant. The group of claim 1 or 2, wherein the solid lubricant comprises tungsten (W), molybdenum (Mo), niobium (Nb), thallium (Ta), titanium (Ti), vanadium (V), and chromium (Cr). A raw powder in which at least one transition metal element selected from and at least one 6A element selected from the group consisting of sulfur (S), selenium (Se) and tellurium (Te) is uniformly mixed in a molar ratio of 1: 2.2 to 3.0. Grease composition, characterized in that obtained by heat treatment for 2 hours or less in the temperature range of about 800 ~ 1000 ℃ while stirring under high pressure atmosphere. The grease composition of claim 3, wherein the solid lubricant is tungsten sulfide (WS ₂ ), molybdenum sulfide (MoS ₂ ), or a mixture thereof. The grease composition according to claim 1, wherein the solid lubricant has a particle size in the range of 1 to 50 µm. The grease of claim 1, wherein the grease is at least one selected from the group consisting of a general grease, a rolling bearing grease, an automotive grease, a concentrated oil grease, a high load grease, a high temperature grease, and a gear compound grease. Grease composition.