JPH04227688A - Dry lubricant for ceramic surface and method for lubrication - Google Patents

Abstract

PURPOSE: To obtain a dry lubricating material that reduces the friction between two materials one of which is a ceramic even at a high temperature under a high load.

CONSTITUTION: There are provided a dry lubricant containing the fluoride of cerium, lanthanum, neodymium, or gadolinium that lubricates the parts of two material surfaces that in contact with each other and a method for the lubrication thereof. A method wherein a rare each fluoride is compacted or a surface is covered using a plasma torch or a flame broad torch. The material contains an inorganic or organic compound that forms a binder and the compound is an organic resin, such as a polyquinoxyline, a polybenzimidazole, a polyimide, acryl, a polyvinyl, an acetate, a phenol, a silicone, an epoxy, a polyamide, or a urethane polymer, or an inorganic compound, such as a silicate or a phosphate. The first surface is made of a ceramic material selected from among a fire resistant type nickel- or cobalt-containing metal material, a non- oxide ceramic, i.e., SiC, Si₃N₄, and BN, and an oxide ceramic, i.e., mullite and zirconia.

COPYRIGHT: (C)1992,JPO

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to dry lubricants and lubrication methods for ceramic/ceramic and metal/ceramic friction pairs.

0002

BACKGROUND OF THE INVENTION Lubrication of moving parts is generally ensured by oils or greases that may or may not be filled with particles. However, the use of these lubricants is limited by the temperature of use.

[0003] Therefore, in high-temperature applications, lubrication of moving parts is generally ensured by heat-resistant inorganic materials such as graphite, calcium fluoride or molybdenum sulfide. This lubrication is dry surface lubrication as opposed to liquid lubrication used at low temperatures.

These solid lubricants are introduced in the form of deposits of varying thickness on the surfaces where friction occurs. They are deposited directly in powder form or in compositions with organic or inorganic binders.

However, solid lubricants that withstand these high temperatures and are introduced onto the friction surface are unable to provide adequate lubrication to this surface. Therefore, a graphite layer deposited between two ceramics moving relative to each other is removed very quickly. This phenomenon has been corrected by many known solid lubricants.

The object of the invention is, on the one hand, to form a stable layer between two surfaces to be lubricated, and on the other hand, especially under external conditions,
In particular, the object of the present invention is to overcome these drawbacks by providing a solid lubricant for surfaces made of ceramic materials, which provides an extremely low coefficient of friction under extremely high temperatures and high loads.

In summary, the present invention provides a material for dry lubricating a contact between a first surface made of a first material and a second surface made of a ceramic material. This lubricant contains at least one rare earth fluoride as a main component.

[0008] Rare earth refers to elements of the lanthanum series with atomic numbers ranging from 57 to 71, including yttrium with atomic number 39. Thus, for example, cerium, lanthanum, neodymium, gadolinium fluoride may be mentioned.

According to a preferred embodiment of the invention, the lubricant of the invention is arranged in a layer or film on one side of the surface to be lubricated. Advantageously, the lubricant is compacted (compacted).

According to another aspect of the invention, the lubricant of the invention also includes an inorganic or organic compound forming a binder in which the rare earth fluoride is dispersed. For example, polyquinoxylines, polybenzimidazoles, polyimides, acrylics, polyvinyls, acetates, phenols, silicones, epoxies, polyamides, urethanes, polyvinyl butyrals or similar polymers may be mentioned as organic binders.

Similarly, as mineral or inorganic binders suitable for the invention, mention may be made, for example, of silicates or phosphates, such as sodium silicates and sodium and/or potassium and/or aluminum silicates.

The lubricant of the present invention may also contain various additives to improve corrosion resistance or to enhance application such as lubricants, colorants, wetting agents, viscosity modifiers, and the like.

The concentrations of binder and rare earth fluoride are not critical. However, in accordance with a preferred embodiment of the invention, the weight concentration of rare earth fluorides in the lubricant is at least 50%, preferably from 80% to 95%.

[0014] The first surface may be made of any material, but
This material can be, for example, a refractory-type metallic material, such as a nickel- or cobalt-containing alloy, or a non-oxide material (SiC,
Advantageously, it is a material that can withstand high temperatures, such as a ceramic such as Si3N4, BN) or an oxide ceramic (mullite, zirconia, etc.).

In a preferred embodiment of the invention, the lubricant of the invention is advantageously made of a material that is particularly suitable for ensuring lubrication between two surfaces made of ceramic material.

The properties of the ceramic are not critical;
Ceramics based on iC, BN, Si3 N4, zirconia, mullite, etc. may be mentioned.

[0017] The lubricant arranged between the surfaces made of ceramic material therefore ensures effective lubrication, especially at high temperatures and under high loads. Furthermore, the lubricant is not removed, thus allowing adequate lubrication for long periods of time (tens of hours).

Furthermore, because rare earth fluorides are stable at high temperatures, good levels of lubrication are maintained even after long-term use.

Another object of the invention is a method for lubricating a contact between two surfaces, at least one of which is made of ceramic material. This method consists of inserting between two surfaces to be lubricated a layer or film of a lubricant containing at least one rare earth fluoride.

[0020] Rare earth elements are listed above as preferred rare earth elements for the present invention.

According to a preferred embodiment of the invention, the lubricant includes an organic or inorganic binder in which rare earth fluorides are dispersed.

These organic or inorganic binders are listed above as having the preferred binder and rare earth composition of the present invention.

The rare earth fluoride used is advantageously a powder having an average particle size of preferably 50 μm or less.

A layer or film of lubricant is deposited on one or both sides of the materials to be lubricated before placing those materials.

The part may be heat treated to evaporate any solvent that the binder may contain. Heat treatment may also be performed prior to mounting the component to at least partially pyrolyze the binder of the lubricant.

It may be advantageous to compress the film or layer of lubricant before putting the part into service.

According to another embodiment of the method of the invention, the lubricant is formed into the desired shape, such as a ring, washer, etc., by molding the composition using any conventional method. It is possible.

According to yet another embodiment of the method of the invention, the lubricant is applied to one side of the material using either a plasma torch or a flame blow torch. Therefore, no binder is required in this case.

Further objects, advantages and details of the invention will become more apparent from the detailed description, the examples given below by way of example only, and the accompanying drawings, in which: FIG.

A test on two ceramic parts 1, 2, one of which is in rotational motion in a particular direction, as shown in FIG. This is done by spreading the word to

In the assembly shown, the rings 4 and 5 are arranged so that they rest against the surface of the ceramic part 1. These rings allow powder to be filled and compressed to a defined volume. Advantageously, these rings are removed after the lubricant has been deposited and after the material has been compressed.

[0032] Therefore, before the part enters into service, 10
A load of 0 to 300 kg is applied to stretch and spread the lubricant.

The part is then run. For example, part 2
It is operated by rotating at a speed of 0.1 m/s.

To determine the effectiveness of the lubricant, part 2
The operating torque required to rotate the
20°C to 1000°C). By measuring this torque, the coefficient of friction (K) can be determined. These measurements are carried out for various loads applied to the ceramic parts 1 and 2.

The results of tests carried out with various lubricants are listed in the table below.

[0036]

[Table 1] Example Temperature (℃) Lubricant
Time (minutes) Friction coefficient

1
graphite fiber
10 0.95

30
0.75

60
0.75 2 20
KS75 (Lonza) 5
0.80
Graphite +
30 0.8
0
binder 60
0.80 3 20
CeF3 +
5 0.50
binder 30
0.30

60 0.32
4 1000 CeF3 +
5
0.18
binder 30
0.12

60
0.06 Experimental conditions: Sliding speed is 0.06.
1m/s Standard load is 1000N

Tests 1 and 2 clearly show that the material introduced into the contact zone is not "trapped" since the values of the coefficient of friction are high after short-term operation. This phenomenon is represented by the curve in Figure 2, and the value of the friction coefficient (
The sharp rise in K) is due to lubricant withdrawal (Examples 1 and 2).

In contrast, the lubricant according to the invention (Example 3
and 4), the trapping is permanent and results in stable operating conditions (FIG. 3) even as the applied load increases (FIG. 4) and as the temperature increases (FIG. 5).

[0039] Lubricant trapping at the contact area can be improved by increasing the self-adhesion of the particles to each other and to the first material. In Examples 3 and 4, CeF3
The powder was treated with an organic binder (Monsanto B74 polyvinyl resin) at a rate of 5% by weight.

Similar results were observed with 10% and 20% binder concentrations and higher molecular weight polyvinyl resins.

Further tests were carried out by depositing a layer of CeF3 on the surface of a metal part by spraying a powder with a particle size of 25-40 μm using a plasma torch. The coefficient of friction between this metal part and the SiC ceramic part was measured at various temperatures and under various loads.

[0042] Thus, the coefficient of friction is high at room temperature, but decreases rapidly when the temperature rises, even at temperatures above 500°C, for example under high loads of 200 to 1000 daN, and at temperatures of 800°C. , Fig. 6a showing the variation of the coefficient of friction as a function of time and the applied load F(da
N) becomes very low as shown in Figure 6b as a function of time.

[Brief explanation of the drawing]

1 shows a cross-sectional view of two ceramic parts lubricated according to the method of the invention; FIG.

FIG. 2 shows the variation of the coefficient of friction (K) between two SiC ceramic rings with graphite lubricant in Example 2 as a function of time.

FIG. 3: Friction coefficient (K) between two SiC ceramic rings with CeF3 lubricant + binder in Example 3.
shows the change in as a function of time.

4a and 4b show the variation of load (F) and coefficient of friction (K) between ceramic (SiC) and metal rings with CeF3 lubricant + binder as a function of time in Example 4; FIG. .

5a and 5b show the variation of load (F) and coefficient of friction (K) between ceramic (SiC) and metal rings with CeF3 lubricant + binder as a function of time in Example 5. .

Figure 6: Using a plasma torch to apply C on the surface of a metal part.
When tested by depositing a layer of eF3 at a temperature of 800 °C, Fig. 6(a) shows the variation of the coefficient of friction as a function of time, and Fig. 6(b) shows the variation of the coefficient of friction as a function of the applied load F(daN). is shown as a function of time.

Claims (19)

[Claims] 1. A solid material for dry lubrication of a contact between a first surface made of a first material and a second surface made of a ceramic, the solid material comprising at least one rare earth fluoride. The above solid material characterized by: 2. The material of claim 1 comprising cerium, lanthanum, neodymium or gadolinium fluoride. 3. The material of claim 1 or 2, wherein the rare earth fluoride is compressed. 4. The method of claim 1 or 2, wherein the rare earth fluoride is applied to the surface using a plasma torch or a flame blow torch. 5. Material according to claim 1, comprising an inorganic or organic compound forming a binder. 6. The compound forming the binder is polyquinoxyline, polybenzimidazole, polyimide,
6. The material of claim 5 which is an organic resin selected from the group consisting of resins such as acrylics, polyvinyls, acetates, phenols, silicones, epoxies, polyamides or urethane polymers. 7. The material of claim 5, wherein the compound forming the binder is an inorganic compound selected from the group consisting of silicate- or phosphate-containing compounds. 8. A group consisting of a nickel- or cobalt-containing metal material whose first surface is a refractory type, and a ceramic material selected from non-oxide ceramics such as SiC, Si3 N4, and BN, and oxide ceramics such as mullite and zirconia. Claims 1 to 7 made of a material selected from
any one of the materials. 9. Material according to claim 1, wherein the two surfaces are made of ceramic material. 10. The ceramic material is SiC, BN,
10. A material according to any preceding claim, selected from the group consisting of ceramics comprising Si3 N4, zirconia and mullite. 11. A method for dry lubrication of a contact between two surfaces, one of which is made of a ceramic material, comprising: applying a layer of a lubricant containing at least one rare earth fluoride between the two surfaces to be lubricated; The above method characterized by inserting. 12. The method of claim 11, wherein the lubricant comprises an inorganic or organic binder in which at least one rare earth fluoride is dispersed. 13. The method of claim 12, wherein the rare earth fluoride represents at least 50% of the lubricant by weight. 14. The organic binder is polyquinoxyline, polybenzimidazole, polyimide, acrylic,
14. The method of claim 12 or 13, wherein the resin is selected from the group consisting of resins such as polyvinyl, acetate, phenolic, silicone, epoxy, polyamide and urethane polymers. 15. The method of claim 12, wherein the inorganic binder is selected from the group consisting of silicate or phosphate containing compounds. 16. The method of claim 11, wherein the lubricant is deposited on one of the surfaces to be lubricated using a plasma torch or a flame blow torch. 17. The method according to claim 11, wherein the rare earth fluoride is one selected from the group consisting of cerium fluoride, lanthanum fluoride, neodymium fluoride, and gadolinium fluoride. 18. A method as claimed in any one of claims 11 to 15 and 17, characterized in that a layer of lubricant is compressed between two surfaces to be lubricated. 19. The layer of lubricant is compressed into the desired shape before being placed between the surfaces to be lubricated.
5 and the method of any one of 17-18.