JPH03170655A - Aluminum-base sliding member - Google Patents

Abstract

PURPOSE:To obtain an Al-base sliding member excellent in wear resistance and seizure resistance by forming an Al thermally sprayed layer in which fine graphite powder is dispersed and which has specific percentage of pores on the sliding surface of a sliding member made of Al alloy. CONSTITUTION:Plasma spraying is applied to the sliding surface of a sliding member made of Al-base alloy, such as Al-Si alloy, by using a pulverized powder mixture of Al alloy and graphite as a raw material, by which in Al alloy thermally sprayed layer which contains fine-grained graphite of 10-50mum average grain size by 0.4-1.0wt.% and in which porosity is regulated to 3-10% is formed on the sliding surface. Since graphite functions as a solid lubricant and also superior retentive property of lubricating oil is provided owing to the presence of many pores in the sliding surface in the above thermally sprayed layer, the sliding member made of Al-base alloy excellent in the wear resistance, seizure resistance, etc., of the sliding surface can be produced.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an aluminum-based sliding member, and particularly to an aluminum-based sliding member with improved wear resistance and seizure resistance. It is related to.

[Conventional technology]

Conventionally, A of aluminum-silicon (Aj!-St) alloy, etc.
In order to improve the wear resistance and seizure resistance of l-based materials, solid lubricants such as graphite and molybdenum disulfide (Host) are added and compounded. The first method is to plate it with graphite or the like and cast it, and the second method is to use A7! A method is known in which powder and graphite powder are mixed, compacted, sintered, and hot extruded (Journal of the Japan Institute of Metals, Vol. 52, No. 2 (1988)).
pl63-pl70).

[Problem to be solved by the invention]

In the first method described above, graphite particles are dispersed throughout the product, and it is particularly difficult to disperse graphite only on the necessary surface area. As a countermeasure to this problem, thermal spraying may be applied only to the necessary surface areas, but although this method improves wear resistance, there is a problem with seizure resistance. In addition, when compounding Al and graphite by hot extrusion using the second method, it is difficult to uniformly disperse fine graphite (the graphite pieces stick together), and it is difficult to retain oil. It is also quite difficult to distribute the pores uniformly even if the sintering conditions are changed.

An object of the present invention is to provide a /l-based sliding member with improved wear resistance and seizure resistance.

[Means to solve the problem]

According to the present invention, the above-mentioned problem is solved by having a sliding surface of a sliding member made of an aluminum base material having an average thread diameter of 10 to 50A=111 and 0. 4-1. The problem is solved by an aluminum-based sliding member characterized in that it is made of 0% by weight of graphite and the remainder is an aluminum-based material, and is provided with a sprayed layer having a porosity of 3 to 10%.

[For production]

According to the present invention, it is only necessary to provide a thermally sprayed layer only on the sliding part, and the matrix of the thermally sprayed layer is an AI. The adhesive is used as a base material to ensure adhesion, and the seizure resistance is improved by adding a specific amount of graphite with a predetermined fine particle size.

By forming the sliding portion of the sliding member into a thermally sprayed layer and providing predetermined pores in the thermally sprayed layer, the pores can enhance oil retention and ensure lubricity.

The argonium-based material used in the present invention is Al, Al
- Si alloys, etc. are effectively used.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

In order to improve the seizure resistance of AN-based automotive parts, we carried out thermal spraying, which is low cost and can treat only designated areas.
An ffi-based sliding member was manufactured.

First of all, since the material is Afg material, we took into account the adhesion of the sprayed layer (especially the wettability between graphite particles and Af and the coefficient of thermal expansion). A is a material! ! ．． -Si alloy and graphite were crushed and mixed, and the resulting powder was subjected to plasma spraying on an Af-based material, and the seizure resistance of the sprayed coating was evaluated. First, as raw material powder ingredients, combinations of ingredients as shown in Table 1 were used, and the combinations of these ingredients were mixed in a mixing machine for 30 minutes.

Table 1 Nao Aj! The average particle size of the -Si alloy powder was kept constant at 70 Jtm. Further, the mixing ratio of Al-S i and graphite was 7:3 (volume %). Table 2 shows the plasma spraying conditions for these mixed powders.

Table 2 Under these spraying conditions, the end face of a mechanical laboratory type cylindrical test bead was sprayed to a thickness of 1 layer, and then Emery Paver #100 was sprayed.
A seizure test was conducted in which a cylindrical test piece with the sprayed layer facing down was stood up, a load was applied from above, and the support of the test bead was rotated. Table 3 shows the conditions for the burn-in test. 3. Figure 1 shows the results of the surface burn-in test. Also, the distribution state of graphite, especially the graphite particle size of 30μ and 100μ,! The metal structure photographs of III1 are shown in FIGS. 2 and 3, respectively.

From this result, it was found that seizure resistance was improved only when graphite having an average particle size of 10p to 50ta was combined with 1M. The porosity of the sprayed layer at this time was about 5%. Here, graphite with an average particle size of less than 10 m was burnt by the high heat of the plasma during thermal spraying, and almost no effect remained in the sprayed layer, so it seems that the effect did not appear. is 5o
When the distance exceeds n, especially 100 m, the following phenomenon occurs. In other words, the role of graphite in seizure is as follows:
Destruction of the generated adhesive layer and self-lubricating properties of graphite itself are mentioned. Here, the surface condition of the sprayed layer after the seizure test is shown in FIGS. 4(a) and 4(b). Figure 4 (a
) shows the adhesion state when the graphite particles are large, and FIG. 4(b) shows the adhesion state when the graphite particles are fine. It can be seen that no adhesive layer is coated on the graphite, regardless of the size of the graphite particles. However, it can be seen that the area of the adhesive layer around large graphite particles is larger than that of small graphite particles. This adhesive layer will eventually fall off, but the larger the adhesive layer that falls off from the graphite part, the more aggressive the wear will be if it gets between it and the mating material, which will eventually lead to seizure. Conceivable. That is, when compounding graphite into A1, it is necessary to reduce the graphite particle size and make the adhesive layer fine. However, as mentioned above, if the particle size of graphite is too small, it will burn during thermal spraying and become CO2 gas, which will not remain in the thermal spray layer.

Next, we investigated the amount of graphite contained in the sprayed layer. For graphite with an average particle size of 10 -, the blending ratio (volume %) with /112Si was varied as shown in Table 4, and thermal spraying tests were conducted. The thermal spraying conditions are the same as in Table 2 above.

Table 4 (Blending ratio: Volume %) * Large variation A: Amount of graphite in the sprayed layer (% by weight) The results of measuring the amount of graphite in each sprayed layer are shown in the bottom column of Table 4.

In this test, when the blending ratio of graphite exceeded 70% by volume, the fluidity of the mixed powder deteriorated and a sprayed layer with evenly dispersed graphite could not be obtained (also, in the case of 90% graphite, most of the sprayed material flowed (Thermal spraying became impossible.) The reason for this is thought to be that the fine graphite particles get between the Al particles and suppress the flow of AN, or that the difference in specific gravity is large and they separate when the powder is supplied. Next, a seizure test was conducted for each sprayed layer. The results are shown in FIG. Fifth
From the figure, it was found that if the amount of graphite was less than 0.4 (wt%), no effect was observed, and that 0.4 (wt%) or more was required. However, considering the above-mentioned meltability, when melting or spraying a mixed powder of Af and fine graphite particles, the
) graphite content is appropriate.

Furthermore, if the Al alloy is changed to pure Al, Af
Due to its ease of shearing (softness), ,11-
The seizure resistance was higher than that of 12Si. In this case as well, the influence of graphite particle size had the same tendency (Figure 1).

On the other hand, in Af alloys with Siii exceeding 12%, hard S
Since the T-grain promotes aggressive wear, the seizure resistance decreases.

Furthermore, the porosity of the sprayed layer was also investigated.

Generally, there are many pores in the sprayed layer, which are said to improve lubricity. Therefore, we also clarified the influence of pores on the sprayed layer of Af + graphite. That is,
Seizure tests were conducted on sprayed layers with varying porosity depending on spraying conditions such as gas flow rate and spraying distance. The results are shown in FIG. From Figure 6, with a porosity of 3 to 10%,
It was found that seizure resistance could be improved. Porosity is 3%
If it is less than 10%, the effect of the oil pool is not exhibited, and if it exceeds 10%, the bonds between the 11 particles become weak and fall off during sliding, resulting in aggressive wear and a decrease in seizure load.

An AN alloy shift fork was selected as a component requiring seizure resistance, and the material shown in Table 5 was applied to the pawl portion, and a synchro durability evaluation (number of cycles until seizure occurred) was performed.

Table 5 The results of the synchro durability evaluation obtained are shown in FIG.

It is clear from FIG. 7 that the product of the present invention has superior seizure resistance to the untreated material, the resin material (nylon) with low μ (coefficient of friction), or the conventional hot extruded product as comparative materials. was confirmed. Moreover, no peeling of the sprayed layer was observed. Note that the graphite distributed in the hot extruded product was in the form of large lumps, and the surface porosity was as low as about 1%.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to significantly improve the seizure resistance of sliding members with high circumferential speeds and high surface pressures, and to improve the adhesion between the base material and the sprayed material and the oil retention. The properties were also good.

[Brief explanation of the drawing]

Figure 1 shows pure A1 and /! 1/! -12Si material is used to show the relationship between graphite particle size and seizure resistance, respectively. Figures 2 and 3 are photographs of metal Mi weave with graphite particle sizes of 30μ and 100μ in Figure 1, respectively. , and Fig. 4 (
a) and (b) are metallographic photographs showing the adhesion state when the graphite grains are large and fine, respectively, and Figure 5 shows the graphite ffi (wt%) in the sprayed layer and the seizure load (kg). FIG. 6 is a diagram showing the relationship between the porosity (%) of the sprayed layer and the seizure load (kg), and FIG. 7 is a diagram showing the relationship between the porosity (%) of the sprayed layer and the seizure load (kg). FIG. 3 is a diagram showing the results of an investigation using wood and comparative material.

Claims (1)

[Claims] 1. On the sliding surface of a sliding member made of aluminum-based material,
It is characterized by having a thermal sprayed layer having an average particle size of 10 to 50 μm, consisting of 0.4 to 1.0% by weight of graphite, and the balance being an aluminum-based material, and having a porosity of 3 to 10%. Aluminum-based sliding member.