JPH0649929B2 - Method for manufacturing sliding contact member having excellent wear resistance - Google Patents

Description

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

(Prior Art) In recent years, in order to prevent abnormal wear of a cylinder system, scuffing, corrosion wear, etc. that occur in an engine using a turbocharger, a supercharger, an EGR that utilizes exhaust gas, etc., along with the increase in output of an automobile engine, A major issue is to improve the sliding characteristics of the sliding contact material that constitutes the cylinder material, that is, to improve wear resistance and self-lubrication.

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. As described above, when a sliding contact member such as a cylinder is formed of a material having an Al diffusion coating layer obtained by an Al pack treatment at a high temperature, it has very excellent properties in wear resistance and corrosion resistance of the sliding contact member itself. On the other hand, since it has a high hardness, it has a drawback that it significantly wears the mating member, which makes it unsuitable as a sliding contact member.

(INVENTION Problems to be Solved point) Therefore, 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 largely depends on the processing temperature in the Al pack processing as shown in FIG. FIG. 1 shows the change in the X-ray intensity ratio of each component in the Al diffusion coating layer with respect to the pack processing temperature. Therefore, the pack treatment temperature was variously changed, and the sliding characteristics (that is, the wear amount and the friction coefficient) of the obtained Al diffusion coating layer and the wear amount of the mating member (here, flake graphite cast iron was used) were examined. The results shown in FIGS. 2 and 3 were obtained. 2 and 3 show Al ₃
The changes in the amount of wear and the coefficient of friction between the sliding contact member and the mating member with respect to the Ni ₂ / AlNi ratio are shown. Where Al ₃
The Ni ₂ / AlNi ratio is X with respect to the Al diffusion coating layer.
It is represented by the X-ray intensity ratio by line analysis. As is clear from FIG. 3, Al ₃ N in the Al diffusion coating layer
When the i ₂ / AlNi ratio is 0.4 to 4 (in other words, the production ratio of Al ₃ Ni ₂ is 30 to 80%), it is found that the Al diffusion coating layer and the mating member both show excellent sliding characteristics. I did.

(Object of the invention) The present invention has been made based on the above findings, and by keeping the Al pack treatment temperature at a relatively low temperature, Al ₃ Ni ₂ and AlNi precipitated on the surface of the metal substrate are mixed, The object is to obtain a sliding contact member having excellent sliding characteristics.

(Means for Achieving the Purpose) In the present invention, as a means for achieving the above object, a metal base material formed by forming a Ni—P plating layer containing P on the surface of a metal base material is treated with Al powder. 520 to 680 in an inert gas atmosphere by embedding in an Al pack agent consisting of a mixture of Al, O ₂ O ₃ powder, a halogen compound and misch metal.
Heat treatment is performed at ℃.

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

That is, by the Al pack treatment as described above, Al diffuses and permeates into the plating layer, and an Al diffusion coating layer in which Al ₃ Ni ₂ and AlNi are mixed is formed on the plating layer. in Al diffusion coating layer, by P is contained in the plating layer, generation of Al ₃ Ni ₂ rich in self-lubricating property is promoted, it is a Al ₃ Ni ₂ by low-temperature packing and high hardness AlNi Since they are present in a suitable mixing ratio, it is possible to obtain a sliding contact member with significantly improved sliding characteristics as the sliding contact member.
Here, the halogen compound in the pack agent acts as an activator that promotes diffusion and penetration of Al. Although P can be contained in the range of 5 to 15%, preferably 5 to 10%.
Is.

Further, the Al diffusion coating layer has a low coefficient of friction,
When used as a cylinder for an automobile engine, sliding resistance is reduced.

When the treatment temperature is lower than 520 ° C, Al ₃ Ni ₂ is less likely to be generated, and a sufficient Al diffusion coating layer cannot be obtained even after taking a long time. It cannot be used as a member. In addition, P is 5
It can be contained in the range of 15%, but preferably 5 to 10%
Is.

(Example) A metal base material obtained by performing Ni-P plating containing 8% P on the surface of a metal base material is subjected to an Al pack treatment under the following conditions to form an Al diffusion coating layer on the surface of the metal base material. Formed. The cross-sectional structure is shown in FIGS. 8 (a) and 8 (b), and FIG. 8 (a) is a magnified 100 times with a microscope, and FIG.
Is a magnified 400 times, and in the figure, symbol A is the base metal, B
Indicates a Ni-P plating layer, and C indicates an Al diffusion coating layer. The rectangular marks in the figure are indentations for the hardness test.

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 was embedded in the above-mentioned pack agent, and this was heat-treated in an inert gas (eg, H ₂ , N ₂ , Ar, etc.) atmosphere.

Then, the heat treatment temperature was variously changed in the range of 500 to 750 ° C., and the sliding contact member (cylinder) and the mating member (piston ring) obtained at each treatment temperature were subjected to the dry abrasion test. The results shown in the figure were obtained. In addition,
The pack processing time was 1 hour in all cases. In FIG. 4, those at 500 ° C., 700 ° C. and 750 ° C. are comparative examples for showing a comparison with this example.

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.

As the test device, the reciprocating sliding tester shown in FIG. 7 was used. That is, the mating member (piston ring piece) 13 is reciprocated while being pressed with a predetermined surface pressure P on the upper surface of the sliding contact member (cylinder piece) 12 fixed on the base 11.
Both wear weights 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, 1
Reference numeral 7 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 For comparison with this example, FIG. 5 shows the result of dry abrasion test performed on the Ni plating layer subjected to Al pack treatment.

As is apparent from the results of the above test, the Al diffusion coating layer obtained by the method of the present invention has extremely excellent wear resistance. In addition, when the temperature of the Al pack treatment is 500 ° C. or lower, the Al on the Ni-P plating layer is
As the desired Al diffusion coating layer cannot be obtained due to insufficient diffusion, wear resistance becomes poor as shown in FIG. 4, and when the Al pack treatment temperature reaches a high temperature of 700 ° C or higher, The examples show excellent wear resistance, but as shown in FIG. 6, the Ni-P plated layer may peel off from the base material, 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-P layer. FIG. 6 shows the change in the peeled area ratio of the Ni-P plated layer with respect to the pack processing temperature.

(Effects of the Invention) As described above, the Ni-P plating layer is exposed to A at a low temperature of 520 to 680 ° C.
According to the method of the present invention in which the l-pack treatment is performed, the presence of P promotes the production of Al ₃ Ni ₂ which is rich in self-lubricating property in the Al diffusion coating layer formed on the surface of the metal substrate, and Al ₃ Ni ₂ is mixed. As a result, a sliding contact member having excellent seizure resistance and wear resistance can be obtained.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing the X-ray intensity ratio of each component of the Al diffusion coating layer with respect to the Al pack treatment temperature, and FIG. 2 is Al ₃ Ni ₂ / A in the Al diffusion coating layer.
FIG. 3 is a characteristic diagram showing changes in wear of the sliding contact member (solid line A) and the mating member (solid line B) with respect to the 1Ni ratio.
l Al ₃ Ni ₂ / AlNi in the diffusion coating layer
FIG. 4 is a characteristic diagram showing a change in friction coefficient of the sliding contact member with respect to the ratio, FIG. 4 is a diagram showing a result of a dry abrasion test of the sliding contact member according to the embodiment of the present invention, and FIG. FIG. 6 is a diagram showing the results of a dry abrasion test performed on the product subjected to the pack treatment, FIG. 6 is a characteristic diagram showing changes in the peeled area ratio of the plating layer with respect to the Al pack treatment temperature, and FIG. A schematic side view, FIGS. 8 (a) and 8 (b) are Al
It is a figure which shows the metal structure | tissue which performed the pack process.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masafumi Yoriko 3-3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (56) References JP-A-56-81668 (JP, A) JP-A-56 -87661 (JP, A)

Claims (1)

[Claims] 1. A metal base material obtained by forming a Ni-P plating layer containing P on the surface of a metal base material, and using Al powder, Al ₂ O.
₃ Manufacture of a sliding contact member having excellent wear resistance, which is embedded in an Al pack agent composed of a mixture of powder, a halogen compound and misch metal and heat-treated at 520 to 680 ° C. in an inert gas atmosphere. Method.