JPH0649927B2 - Sliding contact member - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sliding contact member 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.

In addition, a technique of dispersing particles having a high self-lubricating property (for example, boron nitride) on a sliding surface for the purpose of reducing frictional resistance is generally well known. However, when the mother layer is made of a soft metal, improvement in wear resistance cannot be expected under frictional conditions under high surface pressure.

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 addition, when boron nitride (hereinafter referred to as BN) or the like is dispersed in the Al diffusion coating layer obtained by the high temperature Al pack treatment to improve the self-lubricating property, the self-lubrication of BN occurs because the treatment temperature is high. The sex will be lost.

(INVENTION It'll solve problems) Therefore, 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. Therefore, by reducing the pack processing temperature to a temperature below 700 ° C, Al ₃ Ni
It was found that ₂ and AlNi can be mixed appropriately. Moreover, the self-lubricating property of BN can be maintained in the case of low temperature treatment of less than 700 ° C.

(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. The object is to obtain a sliding contact member having excellent wear resistance and seizure resistance by appropriately selecting BN and dispersing BN.

(Means for Achieving the Purpose) In the present invention, as means for achieving the above object, N
It is obtained by subjecting the sliding contact surface of a metal base material containing i and BN to an Al pack treatment under a low temperature condition of less than 700 ° C., in which Al ₃ Ni ₂ and AlNi are mixed and 5 to 15% by weight.
BN is dispersedly contained in the Al diffusion coating layer.

(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 high-hardness AlNi exist in a suitable mixing ratio and BN having a high self-lubricating property is dispersed, the wear resistance and seizure resistance of the sliding contact member are significantly improved.

When the amount of BN dispersed is less than 4% by weight, the effect of improving self-lubricity by BN does not appear, and when it is 15% by weight or more, mechanical brittleness may occur and peeling may occur.

(Example) An Al pack treatment was applied to a metal base material obtained by forming a Ni-BN plating layer containing 10% by weight of BN fine particles on the surface of a metal base material made of flake graphite cast iron under the following conditions, An Al diffusion coating layer in which 10% by weight of BN was dispersed was formed on the surface of the metal substrate.

Composition of pack agent Al ₂ O ₃ powder (# 100 to 200): 67.5 (wt%) Al powder (# 100 to 200): 30.0 (wt%) Misch metal powder (# 80 to 200): 0.5 (wt%) NH ₄ Cl powder: 2.0 (wt%) The metal base material is embedded in each of the above-mentioned packing materials, and the metal base material is embedded in an inert gas (eg, H ₂ , N ₂ , Ar, etc.) atmosphere.
It heat-processed at 600 for 1.0 hour. The pack processing temperature is preferably in the range of 550 to 680 ° C, and the pack processing temperature is 55
When the temperature is lower than 0 ° C, Al diffusion into the Ni-BN plated layer is not sufficiently performed, and a desired Al diffusion coating layer cannot be obtained. Further, if the pack processing temperature is higher than 700 ° C., the Ni plating layer may peel off from the base material as shown in FIG. 1, which is not desirable. It is considered that this is due to the difference in thermal expansion coefficient between the base material and the Ni plating layer. First
In the figure, N on the cast iron base material with respect to the pack processing temperature
The change in the peeled area ratio of the i-plated layer is shown.

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.

Abnormal wear surface pressure limit of the mating member made of ductile cast iron that has been subjected to quenching and tempering treatment in the sliding contact member obtained in the above example,
As shown in FIG. ^2, it was 0.6 kg / mm ² . It should be noted that the abnormal wear surface pressure limit of the sliding contact member (comparative example) obtained by subjecting the metal base material formed only with Ni plating to the Al pack treatment (comparative example) and the counterpart member similar to the above embodiment is as shown in FIG. It was 0.4 Kg / mm ² . FIG. 2 shows a change in the amount of wear with respect to a change in the surface pressure P in a dry wear test performed using the wear test apparatus shown in FIG. Here, the solid line A and the dotted line B show changes in the wear amount of the sliding contact member and the mating member in the present embodiment, and the solid line A ′ and the dotted line B ′ represent the wear amount of the sliding contact member and the mating member in the comparative example. Shows changes.

A reciprocating sliding tester shown in FIG. 4 was used as the wear test device. That is, the mating member 13 was reciprocated while being pressed against the upper surface of the sliding contact member 12 fixed on the base 11 with a predetermined surface pressure P, and the wear weights of both members were measured. Here, reference numeral 14 is a motor, 15 is a crank that converts the rotational movement of the motor 14 into reciprocating movement, 16 is a holder that supports the mating member 13, 17 is a linking member that connects the holder 16 and the crank, and 18 is It is a support base.

The test conditions were as follows.

Speed: 700 cycles / minute, Distance N: 20000, Friction length: 10
mm, Friction method: Reciprocating friction in air, wear measurement: gravimetric method As is clear from the above results, a metal base material having a Ni plating layer in which BN is dispersed is treated with an Al pack at a low temperature treatment condition of 550 to 700 ° C. As a result, the Ni plating layer changes into an Al ₃ Ni ₂ -AlNi layer (Al diffusion coating layer) with excellent wear resistance, and the BN contained in the dispersed state exhibits self-lubricating properties without deteriorating, so The sliding contact member has excellent wear resistance and seizure resistance.

FIG. 3 shows the change in the friction coefficient of the sliding contact member with respect to the amount of dispersion of BN.
It can be seen that the amount of dispersion is necessary. In the above embodiment, N
Although the i-plated layer having BN dispersed therein is subjected to the Al pack treatment, even if the alloy-cast iron surface containing Ni containing BN dispersed therein is subjected to the Al pack treatment, the sliding contact of the present invention is achieved. The member can be obtained. The thickness of the Al diffusion coating layer may be in the range of 5 to 30 μ, but from the practical viewpoint, 1.0 to 20 μ is more preferable. (Effects of the Invention) As described above, according to the present invention, it is obtained by subjecting the sliding contact surface of the metal base material containing Ni and BN to the Al pack treatment under the low temperature temperature condition of less than 700 ° C. Al ₃ Ni ₂ and Al
Since an Al diffusion coating layer in which Ni is mixed and 5 to 15 wt% of BN is dispersedly contained is formed, the mixture of self-lubricating Al ₃ Ni ₂ and ductile AlNi causes The sliding property is remarkably improved, the adhesion to the metal base material and the durability are also remarkably improved, and the seizure resistance is remarkably improved due to the presence of BN which is rich in self-lubricating property. Therefore, 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 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, and FIG. 2 is a characteristic diagram showing the results of wear tests of this example and a comparative example. FIG. 3 is a characteristic diagram showing a change only in the friction coefficient with respect to the amount of BN dispersed in the Ni plating layer, and FIG. 4 is a side view showing the outline of the wear test device.

 ─────────────────────────────────────────────────── ─── Continuation of the 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-56 -81668 (JP, A) JP-A-60-103176 (JP, A)

Claims (1)

[Claims] 1. A metal base material containing Ni and BN, which is obtained by subjecting a sliding surface of a metal base material to an Al pack treatment under a low temperature condition of less than 700 ° C., in which Al ₃ Ni ₂ and AlNi are mixed and A sliding contact member, characterized in that an Al diffusion coating layer containing 5 to 15% by weight of BN dispersed therein is formed.