JP2006225683A - Magnesium sliding member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a sliding member composed of a magnesium base material provided with high wear resistance and low friction properties which sufficiently withstands practical use by a simpler process. <P>SOLUTION: On the sliding face of a magnesium base material, a coating layer composed of a resin obtained preferably by adding suitable amounts of silicone and fluorine to a polyamide-imide resin is formed by baking coating. The magnesium base material sliding member provided with wear resistance and low friction effect can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sliding member whose base material is a magnesium substrate.

  Magnesium is the lightest and most specific metal among practical metals, and magnesium or magnesium alloys are widely used in fields where weight reduction is required. However, magnesium has inferior sliding characteristics compared to iron and aluminum, and has a high replacement effect from iron or aluminum from the viewpoint of weight reduction, for example, sliding like a cam carrier or oil pan balancer. It was difficult to apply to the accompanying part.

  That is, in order to achieve high wear resistance and low friction, it is desirable to reduce the surface roughness (generally 1 μmRz or less). However, in the case of magnesium having low hardness, the surface roughness is reduced to 1 μmRz by polishing the surface. It is difficult to: FIG. 1 shows the average degree of achievement of the surface roughness of iron, aluminum and magnesium. In iron, the surface roughness after cutting is about 1 μmRz, and the surface roughness after polishing is about 0.1 μmRz. In addition, the sliding surface can be mirrored to such an extent that it can be practically used as a sliding member. Even in the case of aluminum which is a lightweight material, the surface roughness after cutting can be about 1.8 μmRz, and the surface roughness after polishing can be about 1 μmRz. However, in the case of magnesium, the surface roughness after cutting is as high as 2 μmRz, and the surface roughness after polishing is limited to about 1.2 μmRz. Even if it is light, magnesium or a magnesium alloy can slide as it is. Not suitable for parts.

  Furthermore, since magnesium is a low-potential metal and does not itself form a dense oxide film, it is practically necessary to provide a film with excellent corrosion resistance. Further, it has been conventionally proposed to use a magnesium base material as a sliding member by providing adhesion resistance and abrasion resistance to the film to be formed by some means (Patent Document 1, Patent). (See Document 2, Patent Document 3, etc.).

JP 2002-275687 A JP 2003-129158 A JP 2004-149622 A

  In Patent Document 1, an oxide film is formed on a magnesium base material, and a coating material in which an oxide or sulfide of a Group VIa element and a resin dissolved in a solvent are mixed is applied on the oxide layer. In this case, it is described that a polyamide-imide resin is used as the resin, and that the coating material may further contain fluorine, boron nitride, graphite or the like. By including fluorine as an additive, the wear resistance and seizure resistance of the coating layer surface are improved.

  In Patent Document 2, a magnesium alloy coated with a resin-based primer is coated with a resin in which resin fine powder containing tetrafluoroethylene as a main component is dispersed in a thermosetting resin, followed by baking, thereby providing corrosion resistance and wear resistance. A magnesium imide resin is mentioned as an example of a thermosetting resin.

  In patent document 3, the surface roughness of the base material which is an aluminum alloy or a magnesium alloy is 8 to 18 μm Rz, and there is a polyamideimide resin, an epoxy silane as a coating film modifier, and hard particles of silicon nitride or alumina. A coating layer made of a dry film lubricant made of is fired and cured to form a sliding member.

  As described above, in order to improve the wear resistance of the magnesium base material and obtain a stable sliding member, conventionally, as the coating layer, the adhesive layer has high adhesion, good wear resistance, and a friction coefficient. For example, low-stable and stable polyamide-imide resin is used in some form, and fluorine or the like is added to reduce the amount of wear or friction. However, in each case, a specific metal oxide or sulfide is used in combination, another resin such as ethylene tetrafluoride is used in combination, or a coating film modifier such as epoxy silane is used in combination. It is necessary to simultaneously use these materials in some way, and the manufacturing process until an effective sliding member is made is complicated.

  The present invention has been made in view of the circumstances as described above, and can be manufactured by a simpler process, but from a magnesium base material having high wear resistance and low friction properties that can withstand practical use. An object of the present invention is to provide a sliding member.

  In order to solve the above-mentioned problems, the present inventors have conducted many experiments and researches to simply baked and apply a resin mainly composed of polyamideimide resin on the sliding surface of the magnesium base material. As a result, it is possible to make the sliding surface as mirror-finished as that of iron, and a sliding member with high wear resistance and low friction that can withstand practical use can be obtained. I found out the fact that it could be obtained. That is, as shown as “surface roughness after resin application” at the location of magnesium in FIG. 1, by providing the above-mentioned coating layer, the magnesium surface roughness that was limited to about 1.2 μm Rz in polishing was reduced to about 0.1 μm. It could be reduced to about 5 μm Rz.

  FIG. 2 is a graph comparing the wear depth of iron, aluminum, and magnesium and the coefficient of friction (μ) when a coating layer is formed by baking and applying a resin mainly composed of polyamideimide resin (PAI). As shown, the iron is hardly affected by such a coating layer, is advantageous in both wear and friction coefficient, and is a preferred material for the sliding member, but its weight is about four times that of magnesium, Inferior in terms of weight reduction. However, in the case of magnesium, although it is lightweight, by forming a coating layer composed of a resin composed mainly of the above-mentioned polyamideimide resin, the amount of wear is greatly improved to the same level as that of an iron substrate, and the friction coefficient is also increased. It is the same level as the iron material.

  The present invention is based on the above knowledge, and the sliding member according to the present invention basically has a layer made of a resin mainly composed of polyamideimide resin as a coating layer on the sliding surface of the magnesium base. It is characterized by being applied by baking.

  In the present invention, the “magnesium base material” includes alloy materials such as AM60, AM212, WE43 and AZ91 casting materials (high and low pressure casting materials, die casting materials, thixo mold materials, etc.) in addition to pure magnesium materials. ), A AZ31 or AZ80 wrought material, and a magnesium sintered material that is sintered after mixing magnesium powder and alloy element powder. In addition, each symbol which shows the kind of alloy is based on JIS Mg alloy 1 type or Mg alloy casting 2 types.

  In the present invention, as the polyamideimide resin, a known polyamideimide resin excellent in heat resistance and adhesion can be used. As such a polyamideimide resin, for example, a commercially available product used for coating a substrate can be used. The term “resin mainly composed of polyamideimide resin” may be a polyamideimide resin alone or a resin containing an appropriate amount of an appropriate additive (for example, epoxy resin or epoxysilane) as a modifier. I mean. If necessary, an appropriate amount of an appropriate solvent is also included.

  In the present invention, the “baking application” may be a firing / fixing process conventionally performed in this type of coating process, for example, 150 ° C. to 200 ° C. after the resin is applied to the sliding surface. It is the process of baking for about 60 to 90 minutes at the temperature of about.

  In this invention, Preferably, the surface roughness of the coating layer which consists of resin which has the said polyamidoimide resin as a main component is the range of 0.1-5 micrometers Rz. In the experiments by the present inventors, the lower the surface roughness, the lower the friction performance, but the friction coefficient (μ) increased greatly when it exceeded 5 μmRz. This is considered to be an influence of adhesion and unevenness due to roughness. Moreover, when it became smaller than 0.1 micrometer Rz, the friction coefficient rose again. This is probably because the oil film was cut and the contact area increased.

  In the present invention, preferably, the film thickness of the coating layer made of the resin mainly composed of the polyamideimide resin is in the range of 2 to 200 μm, and more preferably in the range of 5 to 100 μm. If the film thickness is less than 2 μm, the service life is shortened and it is not sufficient for use as an actual machine, and if it is 200 μm or more, it becomes overspec. In the experiments of the present inventors, the sliding member according to the present invention was used for the sliding part of the engine used in an automobile, and the film thickness remaining at the time of running 300,000 km was measured. Although the film thickness decreased due to initial wear and familiarity up to a traveling distance of about 100,000 km, the wear after that hardly progressed, and a film thickness of 2 μm was observed after traveling 300,000 km.

  In the present invention, preferably, a resin in which at least one selected from silicone and fluorine is added to a polyamide-imide resin is used as the resin forming the resin layer. As shown in the examples below, the addition of such substances further improves the wear resistance and low friction performance as compared with the case of the polyamide resin alone. Examples of silicone include a polysiloxane structure and polydimethylsiloxane, and examples of fluorine include tetrafluoroethylene.

  In the experiments of the present inventors, in the case of silicone, the amount added is 10 wt% or less, preferably 0.01 wt% to 10 wt%, and if it is less than 0.01 wt%, a sufficient reduction in friction does not occur, If it exceeds 10 wt%, the low friction effect is reduced. In the case of fluorine, the addition amount is 30 wt% or less, preferably in the range of 1 wt% to 30 wt%. In the case of fluorine, if the amount is less than 1 wt%, a sufficient reduction in friction does not occur. The friction effect is reduced. The reason why the amount of addition increases and the low friction effect is lost is presumed to be that the adhesion between the substrate and the resin is lowered and peeling easily occurs.

  In the present invention, both silicone and fluorine can be added, and as shown in a later example, a further friction reduction effect can be obtained by the synergistic effect of silicone and fluorine.

Hereinafter, the present invention will be described by way of examples.
A base material prepared by grinding and polishing the surface of a magnesium alloy (JISAZ91D) by a conventional method was prepared.
As the resin for forming the coating layer on the surface of the substrate, those having the ingredients shown in Table 1 were used.

[Example 1]
A friction test was performed. A plurality of magnesium bases having a surface roughness in the range of 0.1 to 6.0 μmRz were prepared. As an example product, a resin having a component composition shown in Table 1 having a polyamideimide resin of 80 wt% and an additive silicone resin of 1 wt% is prepared on the surface of the substrate, and the resin is applied to the surface of each substrate at 180 ° C. for 60 minutes. The coating layer was baked and applied under conditions. The average thickness of the coating film was 20 μm. The surface roughness of the coating layer was almost the same as the surface roughness of the substrate.

  The friction coefficient (μ) was measured as shown in FIG. 3 for the base material on which each coating layer was not formed and the example product W. The number of rotations of the standard ring was 50 rpm, and the weight was 12 N · m, and Toyota Castle SL 5W-20 was used as the engine oil for the oil tank. The result is shown in FIG.

  As shown in FIG. 4, the example product has a layer made of a resin composed mainly of polyamide-imide resin as a coating layer rather than magnesium alone, so that friction is achieved in the entire surface roughness range. The coefficient (μ) is greatly reduced. Further, in the case of magnesium alone, adhesion was observed at about 2 μm Rz or less, and about 4 μm Rz or more, and an increase in the friction coefficient was observed, but in the case of Example products, until the surface roughness reached about 1.0 μm Rz, The lower the value, the lower the friction performance. Moreover, although the coefficient of friction increased somewhat when it became lower than 1.0 micrometer Rz, this was presumed to be caused by the oil film breakage at the boundary surface, and no adhesion was observed in all ranges.

[Example 2]
Adhesion was tested. Adhesive wear proceeds when the coating film is peeled off, and thus sufficiently high adhesion is required as an actual machine. The coating film of the example product used in Example 1 was sprayed with high-pressure water whose pressure was changed from the surface, and peeling of the film was visually observed. In any case, peeling did not occur up to a water pressure of 20 MPa. The start of peeling at a water pressure of 20 Mpa is a value that can be sufficiently put into practical use as an actual sliding member, and it was confirmed that the sliding member according to the present invention has satisfactory coating film adhesion.

[Example 3]
The amount of wear was tested. Three types of sliding members having the same coating layer as used in Example 1 and having a film thickness of 5 μm, 11 μm, and 50 μm were prepared. However, the surface roughness of the coating layer was adjusted to approximately 1.0 μm Rz. Each sliding member was incorporated into an actual engine and tested, and the film thickness up to 300,000 km travel was measured. The result is shown in FIG. As shown in FIG. 5, the film thickness decreased due to initial wear and familiarity up to a traveling distance of about 100,000 km, and wear after that hardly proceeded. Even if the film thickness is 5 μm, a film thickness of 2 μm remains after traveling 300,000 km. When the present invention product is applied to a sliding part used in an actual automobile, the film thickness should be 5 μm or more. I know it ’s good.

[Example 4]
The friction reducing effect by adding silicone or fluorine was tested. A plurality of types of resins having the component compositions shown in Table 1 were prepared by changing the addition amount of silicone in the range of 0 to 20 wt% and changing the addition amount of fluorine in the range of 0 to 40 wt%. It was baked and applied to the surface of the substrate in the same manner as in Example 1, and the friction coefficient (μ) was measured in the same manner as in Example 1. The result is shown in FIG.

  As shown in FIG. 6, with silicone, a significant reduction in friction is seen when the addition amount is about 0.01 wt% or more, and the effect disappears at about 10 wt%. Further, with fluorine, a significant reduction in friction is observed when the addition amount is 1 wt% or more, and the effect disappears at about 30 wt%. As described above, in the present invention, by adding an appropriate amount of silicone (preferably 0.01 to 10 wt%) or fluorine (preferably 1 to 30 wt%) to the polyamide-imide resin, sliding with further reduced friction is performed. It turns out that a member is obtained. The reason why the amount of addition is increased and the effect of reducing the friction is lost is because the adhesion between the substrate and the coating film is lowered and peeling occurs.

[Example 5]
The effect of reducing the amount of wear by adding silicone or fluorine was tested. The resins shown in Table 1, which are polyamideimide resin (PAI) alone (− ◇ −), those obtained by adding 1 wt% fluorine to polyamideimide resin (−Δ−), and those containing 20 wt% fluorine added to polyamideimide resin. A product (-♦-), a polyamideimide resin added with 0.01 wt% silicone (-▲-), and a polyamideimide resin added with 5 wt% silicone (-●-) were prepared. Each resin was baked and applied to a substrate with a thickness of 12 μm in the same manner as in Example 3, and the change in the amount of wear during traveling at 300,000 km was examined in the same manner as in Example 3. The result is shown in FIG.

  As shown in FIG. 7, it can be seen that the amount of wear is reduced in all resin types and at all distances as compared with the case of the polyamideimide resin alone (− ◇ −).

[Example 6]
The friction reduction effect by the synergistic effect of silicone and fluorine was tested. It is resin shown in Table 1, Comprising: The addition amount of fluorine was changed between 0 to 40 wt%, and silicone was 0.01 wt%, 0.1 wt%, 1 wt%, 3 wt%, 5 wt% with respect to each. A resin added with 10 wt% was prepared. For each resin, test pieces were prepared in the same manner as in Example 1, and the friction coefficient (μ) was measured in the same manner as in Example 1. However, the surface roughness was approximately 2.0 μm Rz, and the coating film thickness was approximately 12 μm. The result is shown in FIG. FIG. 8 shows that the friction with the resin added with an appropriate amount of silicone is lower than the case of adding fluorine alone, and that the low friction effect has a synergistic effect.

A graph comparing the surface roughness of iron, aluminum, and magnesium. A graph comparing the wear amount (μm) and the friction coefficient (μ) of iron, aluminum, and magnesium. The figure explaining the apparatus which performs a friction test. The graph which shows the relationship between surface roughness and a friction coefficient (micro). The graph which shows the relationship between a travel distance and the film thickness remainder. The graph which shows the change of a friction coefficient (micro) when silicone and fluorine are added. The graph which shows the change of the amount of wear when silicone and fluorine are added. The graph which shows the synergistic effect when adding a silicone and fluorine.

Claims (6)

  A sliding member characterized in that a layer made of a resin mainly composed of polyamideimide resin is baked and applied as a coating layer on a sliding surface of a magnesium base.   2. The sliding member according to claim 1, wherein the surface roughness of the coating layer is in the range of 5 [mu] mRz.   The sliding member according to claim 1, wherein the coating layer has a thickness in the range of 2 to 200 μm.   The sliding member according to any one of claims 1 to 3, wherein the resin forming the resin layer contains at least one selected from silicone and fluorine as an additive.   The sliding member according to claim 4, wherein the amount of silicone added is 10 wt% or less.   The sliding member according to claim 4, wherein fluorine is 30 wt% or less.

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