JPH0826365B2 - Method for forming solid lubricant film on metal member surface - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for forming a mechanical element using a sintered alloy used under a high surface pressure, and in particular, a dense and strong solid lubricant on the surface of the metal member. The present invention relates to a method for forming a coating layer.

《Prior art》 Conventionally, solid lubricants are used for sliding parts such as when parts cannot be oil-lubricated like those used in a vacuum, or under high surface pressure. It is also used as a combination.

Solid lubricants, graphite, there are _{M 0 S 2, WS 2,} M 0 Se 2, WSe 2 , etc., the lubrication method, the solid lubricant coating or rubbed methods common to the strategic points the surface of the metal member is there.

In addition, there is a method of forming a lubricant film on the surface of a metal member by vacuum evaporation, ion plating, sputtering, etc. This kind of film forming method is "Bearing Technology in Vacuum and Clean Environment" (MMB Edition). The 16th to the 24th
Page, "Lubrication Handbook" (edited by Japan Society of Lubrication) No. 1131
~ This is a well-known technique described in the literature such as page 1134.

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

<< Problems to be Solved by the Invention >> Generally, the sliding surface of the metal member has some irregularities, and unless it is sufficiently lubricated, the convex portions are rubbed against each other and rub and wear.

According to the method of applying an oil-dispersed solid lubricant paint or the like among the conventional techniques, a film can be easily formed on the surface of the metal member, but the amount of the solid lubricant film is small. However, it has the drawback that it cannot be applied to parts that are deficient in the presence of oil.

In this case, the one coated and dried using the paint of the volatile dispersion medium has a rough coating film and poor adhesion to the metal member, so that it is easily removed by friction, and is easily removed with lubricating oil. It will be leaked.

One of the rubbing methods that can obtain a dry film is to attach a lubricant at the unevenness level of a metal matrix, and it is difficult to form a thick film, and the adhesion to a member is better than that of application. The metal surface appears easily and the lubricating life cannot be expected very much.

In addition, vacuum deposition, ion plating, sputtering, etc. can form a durable dry film up to about 1 μm, and although it has the characteristic of excellent abrasion resistance that cannot be obtained by other methods, it is a cylindrical member. It is difficult to form in the inner portion of the inner diameter, and the cost is high.

On the other hand, a sintered alloy in which a solid lubricant is dispersed in a metal matrix is suitable for use in sliding parts such as under high surface pressure when oil lubrication cannot be performed as in the parts used in vacuum as described above. However, when a large amount of solid lubricant is added, the strength of the material is lowered, so that there is a problem that it is not possible to provide a sufficient amount of solid lubricant in the main part.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a dense and strong metal component on the surface of a metal part made by plastic working such as forging, extrusion, sizing, and coining. It is to provide a method of forming a coating layer at low cost.

<< Means for Solving the Problems >> In order to achieve the above object, the present invention applies a solid lubricant dispersion liquid to the surface of a metal member, forms a coating film by drying, and then presses the metal member with a die. Pressing and plastic working, compressing the coating film with a stamping wall, and densifying and strengthening the coating film by this compression to form a solid lubricant film having an average thickness of 2 to 10 μm. To do.

<< Operation >> The metal member used in the present invention is a metal material that can be plastically worked in cold and warm, and in the case of an ingot, it is subjected to processing such as roughening the cut surface or providing unevenness by blasting. And the film adhesion described later is improved.

Therefore, the preferred material is a sintered metal member, and the pores of the sintered metal member exhibit the same effect as the above-mentioned improvement of the coating adhesion.

When performing plastic working with a closed die such as forging or sizing die of powder metallurgy, the shape of the member before plastic working is smaller than the finished shape in cross section, that is, when the die and core are fed into the die cavity. It is necessary to design the size so that there is a clearance that does not come into strong contact with.

This is because if the thickness is larger than the cross section of the cavity, the coating film will be chipped off at the entrance of the die when the member is supplied.

The coating film of the solid lubricant is obtained by dipping, spraying or brushing in a paint of a volatile dispersion medium, followed by drying, but this coating film has voids and 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 finished coating thickness.

In addition, the coating film drips down to form a portion having an uneven thickness, but it becomes almost uniform in the compression step described later,
The paint is preferably a dispersion of about 20% by weight of solid lubricant powder in a volatile liquid such as an organic solvent, and a dispersant such as resin or cellulose is added to prevent the powder from settling or aggregating.

Then, when a metal member having a solid lubricant coating on the desired surface is put in a die and pressure is applied beyond the deformation resistance of the member, the member deforms until it fills the cavity, and finally on the inner wall of the die. While being closely adhered and molded, the lubricant coating film is compressed and densified to fill the recesses on the surface of the member and strongly adhere.

The pressurizing force in this case is determined by the material properties of the metal member and the size of the above-mentioned clearance, as in the case of normal forging and sizing. Set the dimension of the member including the coating to be the same as the die dimension or a difference of 10 μm or less.

That is, in the low pressure region, the deformation of the member is small and it does not reach the die wall or does not compress the solid lubricant coating, but when the pressure is high, the solid lubricant film when the member is in the die is However, when the pressure is removed and the die is removed from the die, the die and the member are largely deformed and restored, so that the lubricant film once formed is stressed and cracked or peeled.

In the case of a usual molten metal material, a pressing force above the elastic limit of the member is selected.

In the case of sintered metal with pores, the relationship between stress and strain is different from ingot materials, and it is advantageous because it deforms even at low pressure, and reducing the clearance makes it possible to reduce the amount of deformation, Can be less.

The average thickness of the compressed coating film is generally 10 μm, because if it is too thick, it will be deformed during use, it will be worn and the gap between it and the mating member will increase, and the material will be wasted.

On the other hand, the thin film has a short lubrication life when the surface pressure is high, and the present invention aims to form a thick film. Therefore, the lower limit is limited to 2 μm.

A thick coating can be used for parts that make thrust sliding contact with a low-speed load, and a coating thickness of 2 to 4 μm is selected for ordinary externally or internally contacted sliding parts.

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 obtained by observing the cut surface with an electron microscope.

The above-mentioned plastic working is a method of compressing in the vertical direction by using a sealing die having a clearance, but in addition to this, the coating can be similarly formed by a method of reducing the cross section in the perpendicular direction by extrusion. .

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

When the coating is applied only to the inner diameter of the metal member, a good coating can be obtained by a method in which the core is not tapered and a clearance is provided as in the closed die, and the outer member is compressed and extruded.

According to the method for forming a solid lubricant film on a metal surface according to the present invention, a solid lubricant film can be formed thickly, firmly and economically by the same plastic working operation as usual sizing, extrusion and the like.

<Example> Hereinafter, the present invention will be described in detail with reference to Examples.

In this embodiment, the inner and outer diameters of a cylindrical sintered metal are coated with molybdenum disulfide, and plastic working is performed using a die similar to ordinary sizing.

The sintered metal member used has a density of 6.8 g / cm ³ (density ratio
86%) ferrous material, surface hardness H _R F30, radial crushing strength 45k
In g / mm ² , the dimensions are φ6 × φ13 × 20 mm.

The pressing die is a normal die including a die, a core, and upper and lower punches, and the die and the core at the cavity entrance are tapered so that a metal member can be easily inserted therein.

The size of the die and the core was set to 45 μm between the sintered metal member and each of the sintered metal members so that a sufficient coating film thickness can be provided without too large a gap between the sintered member and the sintered member.

The solid lubricant paint was prepared by adding 20% by weight of molybdenum disulfide powder to thinner and mixing it with a dispersant. A metal member was dipped and dried in this paint to have a coating film thickness of about 15 μm.

The thickness of the coating film in the vicinity of the end face portion was partially thick because the coating material dripped, but it was used as a sample.

Fig. 1 shows the relationship between the pressing force and the sample size, where the vertical axis represents 1/2 of the difference between the sample size taken out from the mold and the mold size (corresponding to the interval between the mold and the sample). Where the + sign is larger than the die or core size,-
The symbol represents a small state.

Also, as a result of observing the cross section of the sample taken out from the die with an electron microscope and examining the state of the solid lubricant coating, the pressing force area with insufficient compression and poor adhesion is indicated by the dotted line, and the area where uniform and strong adhesion is observed. The solid line and the region where cracking and peeling are observed are indicated by the alternate long and short dash line.

In 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 was increased, the gap became smaller and became almost the same as the die size at ² t / cm ² , and when the pressure was further increased, it became larger than the die size.

At 1 t / cm ² , the coating film is not compressed, and at 3 t / cm ² or more, the die and the sintered metal member are deformed and restored.

The pressure at which a good film is obtained is ² to 4 t / cm ² , and if it is lower than that, the peeling phenomenon is observed.

In the inner diameter of the sample, the interval without pressure is the same as the outer diameter.
It was 30 μm, and as the pressure was increased, the gap became smaller and became the same as the die size at about 5 t / cm ² .

The plastic deformation of the member represents that the outer diameter direction is prioritized.

The pressure at which a good film is obtained is 2 t / cm ² or more, and lower than that is insufficient.

In the case of this example, the applied pressure at which a film having good inner diameter and outer diameter was obtained was ² to 4 t / cm ² , and the average film thickness was 6 μm.

When the cross section of a good coating is enlarged, the solid lubricant fills the pores on the surface of the base material, and the periphery thereof does not peel off even when scratched with an iron brush.

In addition, in order to evaluate the bonding state of the coating, the sample plastically processed at 3 t / cm ² and the above-mentioned coated dried sample were immersed in an organic solvent, dried by applying ultrasonic vibration, and dried to remove the solid lubricant. As a result, the latter sample lost 82% by immersion for 2 hours, but the sample of this example did not lose weight even after 8 hours.

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

The test method is that the sample is fixed to the shaft, and the outer diameter surface is 10 mm wide.
Of the SCM415 material was abutted against the fixed piece and a load of 40 kg was applied, and the wear condition of the sample slid at a peripheral speed of 15 m / min was examined. At that time, the wear abruptly increased and the test was stopped, but the sample of this example did not cause abnormal wear even after 30 hours.

<< Effects >> As described above, according to the method for forming a solid lubricant film of the present invention, the solid lubricant dispersion is applied to the surface of the metal member and dried to form a film, and then the metal member is pressed. Since it is to press and plastically process with a mold wall and compress the above coating film with a stamping wall, it is a dense and strong coating that cannot be obtained by ordinary coating, and even a thick film with an inner diameter that is difficult by sputtering etc. In addition to being able to be formed, it has an effect that it can be formed efficiently and at low cost by a plastic working method using an ordinary press machine.

[Brief description of drawings]

The drawing is a graph showing the relationship between the plastic working pressure and the dimensional behavior of the member and the state of the coating.

Claims (1)

[Claims] 1. A solid lubricant dispersion is applied to the surface of a metal member and dried to form a coating film, and the metal member is pressed with a die to perform plastic working, and the coating film is compressed with a die wall. A method for forming a solid lubricant film on the surface of a metal member, comprising densifying and strengthening the coating film by this compression to form a solid lubricant film having an average thickness of 2 to 10 μm.