JPH0266104A - Method for forming solid lubricator film on metal member surface - Google Patents

Abstract

PURPOSE:To form a dense and firm coated layer on a surface of a metallic member at a low cost by pressurizing the metallic member in a die to execute plastic working as well as compressing the coated film after forming dry coated film of solid lubricant on the necessary surface of the metallic member. CONSTITUTION:On the necessary surface of the metallic material, which can be subjected to a cold and hot plastic-working, the solid lubricant dispersant liquid dispersed into a volatile dispersion medium is coated and dried, to form the coated film having thickness of about two or three times of the aimed coated film thickness. Then, the preferable metal material is a sintered metal member, and the void of which exhibits the same adhesion enhancement action of the above coated film. Further, as the solid lubricant coating material, for example, a material in which MoS2 powder and the dispersant are added in a thinner and mixed, is exemplified. Successively, the metal material with the coated film is pressurized with the die, to execute the plastic working, and by compressing the above coated film with the die wall, the coated layer of the dense and firm coated layer is formed on the surface of the above metal member. In this case, the average thickness of the compressed coated film is 2 - 10mum.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method of forming a mechanical element using a sintered alloy that is used under high surface pressure. The present invention relates to a method of forming a coating layer.

(Prior art) Solid lubricants have traditionally been used for parts that cannot be lubricated with oil, such as parts used in a vacuum, or for sliding parts that are under high surface pressure. It is also used in combination.

Solid lubricants include graphite, MOS 2, WS 21
M.

Se2. There are WSe2 and the like, and the general method of lubrication thereof is to apply or rub a solid lubricant on the important surfaces of the metal member.

There are other methods of forming a lubricant film on the surface of a metal member by vacuum evaporation, ion blasting, sputtering, etc. This type of film formation method is described in [Bearing Technology in Vacuum and Clean Environments] (MMB Edition). It is a conventionally well-known technique, and is described in documents such as pages 16 to 24 of ``Lubricant Handbook'' (published by Japan Society of Lubrication), pages 1131 to 1134.

On the other hand, there are sintered composite materials in which a solid lubricant is dispersed in an iron-based or copper-based metal matrix, and these materials are used in sliding bearings, retainers, and the like.

(Problems to be Solved by the Invention) Generally, the sliding surface of a metal member has some unevenness, and if sufficient lubrication is not provided, the protrusions will rub against each other, resulting in friction and wear.

Among the conventional techniques, the method of applying oil-dispersed solid lubricant paint can easily form a film on the surface of the metal member, but on the other hand, the amount of solid lubricant film is small, so it cannot be used on sliding parts under high blood pressure. Moreover, it has the disadvantage that it is often insufficient as a solvent, and it cannot be applied to parts where the presence of oil is problematic.

In this case, paints coated and dried using a volatile dispersion medium have a rough coating film and poor adhesion to metal parts, so they easily fall off due to friction, and if lubricating oil is involved, it can easily fall off. It will leak out.

One of the methods for obtaining a dry film is the rubbing method, in which the lubricant is applied to the uneven level of the metal base, but it is difficult to form a thick film, and the adhesion to the component is better than coating. Although it is good, the metal surface is easily exposed and the lubrication life is not very promising.

Additionally, vacuum evaporation, ion blating, sputtering, etc. can produce a durable dry film down to about 1 μm, and although they have the characteristic of exhibiting excellent abrasion resistance that cannot be obtained with other methods, The drawback is that it is difficult to form deep within the inner diameter of the tube and is expensive.

On the other hand, sintered alloys with solid lubricants dispersed in the metal matrix are
As mentioned above, when oil lubrication is not possible, such as parts used in a vacuum, it is suitable for use in sliding parts such as under high blood pressure, but adding a large amount of solid lubricant will reduce the strength of the material. Therefore, there were problems such as not being able to provide a sufficient amount of solid lubrication in the main parts.

The present invention was made in view of the above-mentioned problems, and its purpose is to forge.

The object of the present invention is to provide a method for forming a dense and strong coating layer at low cost on the surface of metal parts made by plastic working such as extrusion, sizing, and coining.

(Means for Solving the Problems) That is, in order to achieve the above object, the forming method according to the present invention prepares a metal member for plastic working, and applies a dry solid lubricant to the surface of the main part. The target film thickness is 2~
After being formed to about 3 times the size, the metal member is pressurized in a mold and plastically worked, and the coating film is compressed to form a dense and strong solid lubricant layer with an average thickness of 2 to 10 μm. .

(Function) The metal part used in the present invention is a metal material that can be plastically worked in cold and warm conditions, and in the case of ingot material, it can be processed by roughening the cut surface or creating unevenness with plasting. By applying this, the film adhesion, which will be described later, will be improved.

Therefore, a preferred material is a sintered metal member, in which the pores exhibit the same effect of improving film adhesion as described above.

When plastic forming is performed in a closed die such as a sizing die in forging or powder metallurgy, the part shape before plastic forming has a cross section smaller than the finished shape, which means that when the part is fed into the die cavity, the die and core It is necessary to design the product to a size that provides a clearance to prevent it from coming into strong contact with the material.

This is because if it is thicker than the cavity cross section, the coating film will be chipped and scraped by the force of the die when supplying the member.

A solid lubricant coating film is obtained by dipping, spraying, or brushing a volatile dispersion medium coating and then drying it, but this coating film has voids and depends on the powder particle size of the solid lubricant used and Depending on the dispersion concentration, the thickness of the coating film is set to about 2 to 3 times the thickness of the finished film.

Note that the coating film will have areas with uneven thickness due to dripping of the liquid, but it will become almost uniform in the compression process described later, and the coating will be coated with a volatile liquid such as an organic solvent and a solid lubricant of approximately 20% by weight. Preferably, the agent powder is dispersed in a resin to prevent the powder from settling or agglomerating.

A dispersant such as cellulose is added.

When a metal member with a solid lubricant coating on the desired surface is placed in a mold and pressure is applied beyond the deformation resistance of the member,
The part is deformed until it fills the cavity, and finally it is molded in close contact with the inner wall of the mold, and the lubricant coating is compressed and becomes dense, filling all four parts of the part's surface and adhering strongly.

In this case, as in normal forging and sizing, the optimum conditions for the pressing force are determined by the material properties of the metal member and the above-mentioned tolerance size, but in the present invention, The dimensions of the member including the coating are set so that they are the same as the dimensions of the mold or have a difference of 10 μm or less.

In other words, in areas where the pressure is low, the part deforms so little that it does not reach the mold wall or compresses the solid lubricant film, but in high pressure areas, the solid lubricant film deforms when the part is inside the mold. Although the material is firmly fixed, when the pressure is removed and the material is removed from the mold, the mold and the member undergo a large degree of deformation recovery, which causes stress to be applied to the previously formed lubricating film, causing it to crack or peel off.

In the case of ordinary molten metal materials, a pressure greater than the elastic limit of the member is selected.

In the case of sintered metals that have pores, the relationship between stress and strain is different from that of molten metals, and it is advantageous because it deforms even at low pressures, and reducing the clearance reduces the amount of deformation, so the pressure It's good to have less.

The average thickness of the compressed film is generally set at an upper limit of 10 μm because if it is too thick, it will deform during use, wear out, increase the gap with the mating member, and waste material.

On the other hand, since a thin film has a short lubrication life under high surface pressure and the present invention aims at forming a thick film, the lower limit was limited to 2 μm.

A thick coating can be used for parts that make thrust sliding contact under low speed loads, and a coating thickness of 2 to 4 μm is selected for ordinary external or internal sliding parts.

Note that the average thickness of the coating is the distance from the coating surface to the average surface that does not include large irregularities such as holes in the metal member, and is determined by observing the cut surface with an electron microscope.

The above-mentioned plastic working is a method of compressing the film in the vertical direction using a sealed mold with a clearance, but a film can also be formed in the same way by reducing the cross section in the right angle direction by extrusion. .

In this case, a small die angle is desirable, and the state of the solid lubricant coating is controlled by the area reduction rate.

When applying a coating only to the inner diameter of a metal member, a good coating can be obtained if the core is not tapered and a clearance is provided in the same manner as in a closed mold, and the outer diameter is compressed and extruded.

According to the method for forming a solid lubricant coating on a metal surface according to the present invention, a thick, strong, and economical solid lubricant coating can be formed by the same plastic working operations as normal sizing and extrusion.

(Example) Hereinafter, the present invention will be explained in detail with reference to Examples.

In this example, a molybdenum disulfide coating is applied to the inner and outer diameters of a sintered metal having a cylindrical shape, and plastic working is performed using a mold similar to that used for normal sizing.

The sintered metal member used has a density of 6.88/cm' (
Iron-based material with density ratio of 86%, surface hardness of HRF30,
The radial crushing strength is 45Kg/III12, and the dimensions are φ6×
It is φ13×20mm.

The press mold is a normal mold consisting of a die, a core, and an upper and lower punch, and the goo at the entrance of the cavity and the core are tapered to allow the metal member to enter easily.

Further, the dimensions of the goo and the core were such that the gap between the goo and the sintered metal member was 45 μm, so that the gap between the goo and the sintered member was not too large and a sufficient coating thickness could be provided.

The solid lubricant paint was a mixture of thinner, 20% by weight of molybdenum disulfide powder, and a dispersant, and a metal member was immersed in this paint and dried to give a coating film thickness of approximately 15 μm.

The thickness of the coating film near the end face was partially thick due to the paint dripping down, but it was used as a sample.

Figure 1 shows the relationship between pressing force and sample size.
The vertical axis represents 1/2 of the difference between the dimensions of the sample taken out from the mold and the dimensions of the mold (corresponding to the distance between the mold and the sample), where the plus sign indicates a state larger than the dimension of the die or core, and the minus sign indicates a state larger than the die or core dimension. It represents a small state.

In addition, as a result of observing the cross section of the sample taken out from the mold with an electron microscope to examine the state of the solid lubricant coating, we found that the dotted line indicates the pressurized area where compression is insufficient and poor adhesion, and the area where the adhesion is uniform and strong is indicated. The solid line shows the area where cracks and peeling are observed, and the dashed line shows the area.

Therefore, in terms of the outer diameter of the sample, the distance between the coating film and the inner surface of the die when no pressure is applied is 30 μm.

As the pressure increases, the distance decreases to 2t/cJ.
When the pressure was increased, it became almost the same as the die size, and when the pressure was increased further, it became thicker than the die size.

It/c♂ indicates that the coating film is not compressed, and above 3t/cJ, the die and sintered metal member return to deformation.

The pressure at which a good coating can be obtained is 2 to 4 t/c♂; anything less than that is insufficient, and more than that, a peeling phenomenon is observed.

On the inner diameter of the sample, the interval when no pressure is applied is 3, similar to the outer diameter.
The distance was 0 μm, and as the pressing force was increased, the interval became smaller and became the same as the die size at about 5t/c+#.

The plastic deformation of the member indicates that the outer radial direction has priority.

The pressure at which a good coating can be obtained is 2t/c♂ or higher, and anything less than that is insufficient.

In the case of this example, the pressing force to obtain a film with good inner and outer diameters was 2 to 4 t/cd, and the average thickness of the film was 6 μm.
Met.

If you enlarge the cross section of a good coating, you will see that the solid lubricant fills the pores on the surface of the base material, and the area around it will not peel off even if you scratch it with a pencil.

In addition, in order to evaluate the bonding state of the coating, a sample plastically worked at 3t/cJ and the above-mentioned coated dried sample were immersed in an organic solvent, subjected to ultrasonic vibration, and then dried to determine the weight of the solid lubricant that had fallen off. As a result, 82% of the latter sample fell off after 2 hours of immersion, but the sample of this example did not lose weight even after 8 hours.

Furthermore, the wear resistance of the same samples as above was compared.

The test method was to fix the sample on a shaft and place a width of 10 m on the outer diameter surface of the sample.
m S 40 by touching the fixed piece made of CM415 material
The wear condition of the sample was examined by applying a load of Kg and sliding at a circumferential speed of 15 m/min. As a result, the 15 μm coating sample was
．． After 5 hours, the wear suddenly became severe and the test was stopped, but the sample of this example did not suffer from abnormal wear even after 30 hours.

(Effects) As described above, according to the method for forming a solid lubricant film according to the present invention, after a solid lubricant dispersion is applied to the surface of a metal member and dried to form a coating film, the metal member is pressed into a mold. The coating is pressurized and plastically processed, and the coating film is compressed using the mold wall, so it is possible to create a dense and strong coating that cannot be obtained with normal coating, and it also produces a uniformly thick coating even on the inner diameter, which is difficult to achieve with sputtering, etc. It has the advantage that it can be formed efficiently and at low cost by a plastic working method using an ordinary press machine.

[Brief explanation of the drawing]

The drawing is a graph showing the relationship between plastic working pressure, member dimensional behavior, and coating condition. Patent applicant Hitachi Powder Metallurgy Co., Ltd.

Claims (1)

[Claims] 1. After applying a solid lubricant dispersion to the surface of a metal member and drying it to form a coating film, the metal member is pressurized with a press mold to be plastically worked, and the coating film is compressed with the wall of the press mold. A method for forming a solid lubricant film on the surface of a metal member.