JPH0649926B2 - Sliding contact member with excellent wear resistance - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sliding contact member having an excellent wear resistance, which is formed by forming an Al diffusion coating layer by an Al pack method on the surface of a metal base material.

(Prior Art) In recent years, in order to prevent abnormal wear, scuffing, corrosion wear, etc. of a cylinder system that occurs in an engine using a turbocharger, a supercharger, EGR that utilizes exhaust gas, etc., along with the increase in output of automobile engines, It has been a major problem to improve the sliding characteristics of the sliding contact member that constitutes the cylinder material, that is, to improve the wear resistance and the self-lubricating property.

Conventionally well-known wear resistance and corrosion resistance treatments include technologies such as gas nitrocarburizing, chromium plating, and wire explosion spraying. In the case of gas nitrocarburizing, cast iron (FCH alloy cast iron) bases are used. As it hardens, the edge of the graphite part becomes a blade, causing galling on the piston and piston ring, etc.
As a result, abrasion scuff occurs, and in the case of chrome plating, it is weak against sulfuric acid corrosion and causes corrosive wear.In addition, in the case of stainless steel wire explosion spray, compatibility with the piston ring is poor and scuff occurs, etc. However, it is difficult to satisfy the above problems.

On the other hand, a surface treatment method for forming an Al diffusion coating layer on the surface of a metal substrate, a so-called Al pack method, has been developed (see, for example, JP-A-56-81668).

However, in the conventional Al pack treatment, a metallic base material containing Ni is embedded in a pack agent (generally consisting of Al powder, alumina powder and halogenated activator) and subjected to high temperature treatment in an inert gas (about 800 ° C. or higher). Then, since the Al diffusion coating layer is formed on the surface of the metal substrate, the Al diffusion coating layer is dominated by high hardness AlNi having a body-centered cubic structure and has a hexagonal structure, It contains only a small amount of Al ₃ Ni ₂ which is rich in lubricity. When a sliding contact member such as a cylinder is formed of a material having an Al diffusion coating layer having such a structure, the sliding contact member itself has very excellent wear resistance and corrosion resistance, but it has a high hardness, so that the mating member is significantly It has a drawback of causing abrasion, and is not suitable as a sliding contact member.

In the above-mentioned known example, a small amount of misch metal (including rare earth element) is added to the pack agent in the Al pack treatment. However, the misch metal added in this case is effective for increasing the oxidation resistance and the corrosion resistance. Although it contributes, since AlNi is dominant in the obtained Al diffusion coating layer due to the high temperature (800 ° C or higher) pack treatment,
The effect of improving friction and wear characteristics by misch metal does not appear sufficiently.

(To be Solved by the Invention Problems) In order to reduce the wear of the mating member, it is conceivable to increase the mixing ratio of Al ₃ Ni ₂ having the self-lubricating properties, mixing of Al ₃ Ni ₂ If the ratio becomes too large, the properties of Al ₃ Ni ₂ which are mechanically brittle and thermally unstable dominate, and crack peeling easily occurs. Therefore, it is necessary to optimally control the mixing ratio of Al ₃ Ni ₂ and AlNi in the Al diffusion coating layer.

The inventors have found that Al ₃ Ni ₂ in the Al diffusion coating layer
It was found that the mixing ratio of AlNi and AlNi greatly depends on the processing temperature in the Al pack processing. However, by reducing the pack processing temperature to 700 ° C or lower, Al ₃ Ni
It was found that ₂ and AlNi can be mixed appropriately.

(Object of the Invention) The present invention has been made based on the above findings, and an appropriate mixing ratio of two compounds of Al ₃ Ni ₂ and AlNi precipitated on the surface of a metal substrate by Al pack treatment under low temperature conditions is suitable. In addition to the above, the purpose of the present invention is to obtain a sliding contact member excellent in wear resistance by preventing the peeling of the surface layer by appropriately dispersing the misch metal.

(Means for Achieving the Purpose) In the present invention, as means for achieving the above object, N
Al obtained by applying an aluminum pack treatment under a low temperature condition of less than 700 ° C. to the sliding contact surface of a metal base material containing i, using an Al pack agent containing misch metal
₃ Ni ₂ and AlNi are mixed and an Al diffusion coating layer containing 0.1 to 2.0% by weight of misch metal dispersed therein is formed.

(Operation) In the present invention, the following operations are obtained by the above means.

That is, the Al diffusion coating layer obtained by the Al pack treatment under the low temperature condition has a high self-lubricating property.
Since Al ₃ Ni ₂ and AlNi having high hardness are present in a suitable mixing ratio and the misch metal for preventing the peeling of the surface layer is dispersed, the wear resistance of the sliding contact member is significantly improved.

When the amount of misch metal dispersed is less than 0.1%, the effect of preventing surface peeling by misch metal does not appear, 2.
If it is 0% or more, the penetration of Al may be hindered and the wear resistance may be deteriorated.

(Example) A metal base material formed by forming a Ni plating layer on the surface of a metal base material made of flake graphite cast iron was subjected to Al pack treatment under the conditions of Table 1 below, and Al was applied to the surface of the metal base material. A diffusion coating layer was formed.

The metal base material is embedded in each of the pack agents described above, and the metal base material is embedded in an inert gas (eg, H ₂ , N ₂ , Ar, etc.) atmosphere.
It heat-processed at 600 degreeC for 1 hour.

A wear test was performed on the sliding contact member having the Al diffusion coating layer obtained as described above, and the results shown in FIG. 1 were obtained. FIG. 1 shows changes in the wear amount (solid line A) and the friction coefficient (dotted line B) of the sliding contact member and the mating member with respect to the added amount of the misch metal made of a rare earth element. According to this, it can be seen that the Al diffusion coating layer obtained by using the NO 2 to 6 pack agent in which the amount of misch metal added is in the range of 0.1 to 2.0 exhibits excellent wear resistance. Where Mishmetal is
It serves to improve the surface gloss of the Al diffusion coating layer and reduce the friction coefficient.

Next, the sliding contact member obtained by changing the pack processing temperature in the range of 500 to 750 ° C. by using the packing agent of NO1 (without misch metal) and NO3 (adding 0.5% of misch metal) (see Table-1). When a wear test was conducted on the above, the results shown in FIGS. 2 and 3 were obtained. FIG. 2 shows changes in the wear amount with respect to the pack processing temperature when the sliding member is a movable piece in the wear test. Here, the solid line C indicates the case of the NO3 pack agent,
The dotted line C'indicates the case of the NO1 pack agent. FIG. 3 shows the change of the wear amount with respect to the pack processing temperature when the sliding contact member is a fixed piece in the wear test. Here, the solid line D shows the case of the NO3 pack agent, and the dotted line D'shows the case of the NO1 pack agent. When the pack treatment temperature is lower than 500 ° C., Al diffusion into the Ni plating layer is not sufficiently performed, and a desired Al diffusion coating layer cannot be obtained. Also, the pack processing temperature is 70
When the temperature is higher than 0 ° C., the Ni plating layer may peel off from the base material as shown in FIG. 4, which is not desirable. FIG. 4 shows the change of the peeled area ratio of the Ni plating layer on the cast iron base material with respect to the pack processing temperature.

However, the thickness of the Al diffusion coating layer depends on the pack processing time, and it is necessary to determine the pack processing time as desired. The Al diffusion coating layer may have a thickness in the range of 5 to 30 μ, and more preferably in the range of 10 to 20 μ in terms of practical use.

As the wear test device used for the above wear test,
The reciprocating sliding tester shown in FIG. 5 was used. That is, the movable piece 13 was reciprocated while being pressed against the upper surface of the fixed piece 12 fixed on the base 11 with a predetermined surface pressure P, and the weight of wear of both was measured. Here, reference numeral 14 is a motor, 15 is a crank for converting rotational movement of the motor 14 into reciprocating movement, and 1
6 is a holder that supports the movable piece 13, 17 is a linking member that connects the holder 16 and the crank, and 18 is a support base.

The test conditions were as follows.

Surface pressure P: 0.4 Kg / mm ² , speed: 700 cycles / min, distance N:
20000, Friction length: 10 mm, Friction method: Reciprocating friction in the atmosphere,
Abrasion measurement: gravimetric method As is clear from the above results, in a pack agent in which a trace amount (0.1 to 2.0%) of misch metal is added to a metal base material having a Ni plating layer, Al is treated under a low temperature treatment condition of 550 to 700 ° C.
By the pack treatment, the Ni plating layer changes into an Al ₃ Ni ₂ -AlNi layer (Al diffusion coating layer) with rich surface gloss in which misch metal is dispersed, low friction coefficient, and excellent wear resistance, Thus, a sliding contact member having excellent wear resistance can be obtained.

In the above embodiment, the metal base material having the Ni plating layer is coated with Al.
Although the desired sliding contact member is obtained by performing the pack process, it is needless to say that the same Al pack process as that described above may be applied to a metal base material containing Ni.

(Effects of the Invention) As described above, according to the present invention, an aluminum pack agent in which a misch metal is added to the sliding contact surface of a metal base material containing Ni is used under low temperature conditions of less than 700 ° C. Since Al ₃ Ni ₂ and AlNi obtained by performing the aluminum pack treatment are mixed and an Al diffusion coating layer containing 0.1 to 2.0% by weight of misch metal dispersedly contained is formed, By mixing Al ₃ Ni ₂ which is rich in surface gloss, has a low friction coefficient, and is rich in self-lubricating property and AlNi which is rich in ductility, wear resistance is improved and a sliding contact member having excellent sliding characteristics is obtained. Further, since the adhesion and durability to the metal base material are remarkably improved, it is possible to obtain the optimum sliding contact member as a material for cylinders for automobile engines.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing changes in wear amount (sliding member and mating member) and friction coefficient with respect to the amount of misch metal added to the pack agent, and FIG. 2 is a movable piece (sliding member) with respect to Al pack processing temperature. ) Is a characteristic diagram showing the wear amount, and FIG.
Fig. 4 is a characteristic diagram showing the amount of wear of the fixed piece (sliding contact member) with respect to the pack treatment temperature, Fig. 4 is a characteristic diagram showing the change of the peeled area ratio of the Ni plating layer on the cast iron base material with respect to the pack treatment temperature, The figure is a side view showing the outline of the wear test apparatus.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masafumi Yoriko 3-3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (56) References JP-A-56-87661 (JP, A) JP-A-SHO 60 -103176 (JP, A)

Claims (1)

[Claims] 1. An Al ₃ obtained by subjecting a sliding contact surface of a metal base material containing Ni to an aluminum pack treatment under a low temperature condition of less than 700 ° C. using an Al pack agent containing misch metal. Ni ₂ and AlNi are mixed and 0.1-2.
A sliding contact member having excellent wear resistance, characterized in that an Al diffusion coating layer containing 0% by weight of misch metal is formed.