JPH0649930B2 - Method of manufacturing sliding contact member having self-lubricating property - Google Patents

Description

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

(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 base material, 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, Al with high lubricity
_It contains only a small amount of ₃ Ni ₂ . 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, the sliding contact member itself has extremely excellent properties in wear resistance and corrosion resistance. 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.

(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 present inventors have confirmed that Al ₃ Ni ₂ in the Al diffusion coating layer
It was found that the mixing ratio with AlNi greatly 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.

(Object of the invention) The present invention has been made based on the above findings, 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-mentioned object, a metal base material formed by forming a plating layer mainly containing Ni on the surface of a metal base material is used as Al powder, Al _It is embedded in an Al pack agent composed of a mixture of ₂ O ₃ powder, a halogen compound and a misch metal, and heat-treated at 570 to 680 ° C. in an inert gas atmosphere.

(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, and an Al diffusion coating layer in which Al ₃ Ni ₂ and AlNi are mixed is formed on the plating layer. Here, the halogen compound in the pack agent acts as an activator that promotes diffusion and penetration of Al. In the Al diffusion coating layer obtained by the Al pack treatment as described above, since Al ₃ Ni ₂ rich in self-lubricity and AlNi having high hardness are present in a suitable mixing ratio, the sliding contact member As a result, the sliding characteristics are significantly improved.

Further, the Al diffusion coating layer has a low friction coefficient, and when it is used as a cylinder for an automobile engine or the like, sliding resistance is reduced.

When the treatment temperature is less than 570 ° C, Al ₃ Ni ₂ is difficult to be generated and a sufficient Al diffusion coating layer cannot be obtained even if it takes time, and when it exceeds about 700 ° C, the plating layer peels off and it is used as a sliding contact member. Can not stand. Incidentally, preferably, 600 ~ 650 ℃
Is the range.

(Example) A metal base material made of flake graphite cast iron obtained by subjecting the surface of a metal base material to Ni plating is subjected to Al pack treatment under the following conditions,
An Al diffusion coating layer was formed on the surface of the metal substrate. FIG. 5 shows the cross-sectional structure. FIG. 5 is an image magnified 400 times with a microscope. In the figure, reference numeral A is a base material, B is a Ni plating layer, and C is an Al diffusion coating layer.

Packing agent composition 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 to 15 (wt%) The metal base material was embedded in the above-mentioned packing material, and this was heat-treated in an inert gas (for example, 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 2.0 hours in all cases. In FIG. 2, 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. 4 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 As is apparent from the results of the above test, it is understood that the Al diffusion coating layer obtained by the method of the present invention has extremely excellent wear resistance and corrosion wear resistance. If the Al pack treatment temperature is lower than 570 ° C., Al diffusion into the Ni plating layer is not sufficiently performed, and a desired Al diffusion coating layer cannot be obtained. Therefore, as shown in FIG.
It becomes inferior in wear resistance and the Al pack processing temperature is 700
When the temperature is higher than 0 ° C., the present example shows excellent wear resistance, but as shown in FIG. 3, the Ni plating layer may peel off from the base material, which is not desirable. This is considered to be due to the difference in the coefficient of thermal expansion between the base material and the Ni plating layer. FIG. 3 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.

(Effects of the Invention) As described above, according to the method of the present invention in which the Al pack treatment is performed at a low temperature of 570 to 680 ° C., the Al diffusion coating layer formed on the surface of the metal substrate has a self-lubricating Al ₃ Ni content. _{Since 2} is mixed appropriately, it is possible to obtain a sliding contact member having excellent peeling resistance, seizure resistance, and abrasion resistance.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing an X-ray intensity ratio of each component of the Al diffusion coating layer with respect to an Al pack treatment temperature, and FIG. 2 is a diagram showing results of a dry abrasion test of a sliding contact member according to an embodiment of the present invention, FIG. 3 is a characteristic diagram showing the change in the peeled area ratio of the Ni plating layer on the cast iron base material with respect to the pack treatment temperature, and FIG.
The figure is a side view showing the outline of the wear test device.
It is a figure which shows the metallographic structure which performed the Al pack process.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kimiaki Mori 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. An Al packing agent comprising a mixture of an Al powder, an Al ₂ O ₃ powder, a halogen compound and a misch metal, which is a metal base material formed by forming a plating layer mainly containing Ni on the surface of a metal base material. Embedded in an inert gas atmosphere at 520 to
A method for producing a sliding contact member having self-lubricating properties, which comprises heat treatment at 680 ° C.