JP2588253B2 - Method of manufacturing wear-resistant sliding member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a sliding member requiring excellent sliding characteristics or wear resistance, for example, a sliding member such as a rocker arm used in a valve train of an engine. The present invention relates to a method for manufacturing a member.

[Prior Art] In various mechanisms having a sliding portion, for example, a valve operating mechanism of an engine, each sliding member such as a rocker arm and a rocker shaft is subjected to severe sliding conditions in order to sufficiently exhibit the performance of the engine. It is required to have wear resistance that can withstand. In a valve operating mechanism that employs a multi-valve mechanism or a variable valve timing mechanism to increase the output of the engine, the amount of valve lift increases and the force applied to the sliding member increases with this. In particular, a sliding member having high sliding characteristics or wear resistance is required.

Conventionally, such a sliding member is formed of a metal material such as a wear-resistant sintered alloy. However, since the metal material generally has a strong adhesive property, the sliding member made of the sintered metal is not used. In particular, there is a disadvantage that adhesion and wear easily occur in a low speed range. For example, when the tip of the sintered alloy sliding member on the rocker arm side is worn and deformed, a non-uniform force acts on the cam that comes into contact with the tip. However, there is a problem that the engine does not function sufficiently and the engine output may decrease.

Therefore, a sliding member made of ceramics mainly composed of, for example, Si ₃ N ₄ (silicon nitride), which has low adhesiveness and excellent mechanical properties and wear resistance, or a metal base material is used. A sliding member formed by bonding ceramics has been proposed (for example, see Japanese Patent Application Laid-Open No. Sho 59-3081).

However, the above-mentioned ceramic sliding member has good sliding characteristics or wear resistance in a normal state, but when oxides of wear powder of various members and hard foreign matter are mixed in engine oil. However, there is a problem in that the contaminants cause wear on the ceramic sliding member.

Therefore, there has been proposed a ceramic sliding member in which a high-strength whisker (fiber-type single crystal) such as Si whisker is blended with a ceramic base material containing Si ₃ N ₄ as a main component (see, for example, 59-54680). However,
Although the ceramic sliding member in which such SiC whiskers are dispersed has excellent sliding characteristics and abrasion resistance, the manufacturing conditions such as powder preparation, molding, and sintering are subject to various limitations, so processing is performed. There is a problem that the degree of freedom of the shape and characteristics of the product cannot be increased, and there is a problem that the material is expensive and disadvantageous in terms of cost.

Therefore, the base material of the sliding member is made of ceramics mainly composed of Si ₃ N ₄ to increase the degree of freedom in the shape of the sliding member, etc., while SiC whiskers are dispersed only in the sliding portion of the sliding member. There has been proposed a method of improving the sliding characteristics or abrasion resistance by using a ceramic formed in such a manner.

[Problems to be Solved by the Invention] As a method of manufacturing such a sliding member having a two-layer structure formed of a ceramic base material and a whisker-dispersed ceramic sliding layer, generally, FIG. As shown in FIG. 2A, a ceramic base material 3 is filled on a bottom plate 2 of a press molding machine 1, and then, as shown in FIG. After filling the sliding layer material 4, press molding is performed under a predetermined press pressure to produce a sintered compact P 'as shown in FIG. 2 (c). Sintering is performed under a predetermined sintering temperature condition (for example, at 1750 ° C. for 2 hours in flowing N ₂ ) to produce a sliding member Q ′ as shown in FIG. 2 (d). . However, in such a manufacturing method, when the sliding member Q 'has a flat sliding surface, it is relatively easy to make the thickness of the whisker dispersed ceramic sliding layer 4 uniform, but When the surface is a curved surface, it is difficult to make the thickness of the whisker dispersed ceramic sliding layer 4 uniform, and there is a problem that the thickness of the whisker dispersed ceramic sliding layer 4 becomes uneven. Therefore, if the whisker-dispersed ceramic sliding layer is to have a thickness equal to or greater than a predetermined value in all portions, the whisker-dispersed ceramic sliding layer 4 must be made extra thick in anticipation of an error. There was a problem.

Therefore, in order to make the thickness of the whisker dispersed ceramic sliding layer uniform, for example, as shown in FIG. 3 (a), the ceramic base material 3 filled in the press molding machine 1 is
First, press molding is performed so that the upper surface thereof is substantially equal to the shape of a predetermined sliding surface, and then, as shown in FIG. After the whisker-dispersed ceramic sliding layer material 4 is filled, press molding is performed at a predetermined pressure, and the whisker-dispersed ceramic sliding layer 4 has a uniform thickness as shown in FIG. A method of manufacturing a molded body P ″ and sintering the molded body P ″ for sintering to manufacture a sliding member Q ″ is conceivable. According to such a manufacturing method, a whisker-dispersed ceramic slide is used. Since the coupling between the moving layer 4 and the ceramic base layer 3 is weakened, there is a problem that the sliding member Q ″ is easily separated at the boundary between the two layers as shown in FIG. 3 (d).

The present invention has been made in view of the above-described conventional problems, and in a method for manufacturing a wear-resistant sliding member in which a whisker-dispersed ceramic sliding layer in which whiskers are dispersed is formed on a ceramic substrate, Irrespective of the shape of the sliding surface of the sliding member, the thickness of the whisker-dispersed ceramic sliding layer can be made uniform, and the whisker-dispersed ceramic sliding layer and the ceramic base layer can be securely connected. Can be
An object of the present invention is to provide a method for manufacturing a wear-resistant sliding member that can improve the reliability of the sliding member.

Means for Solving the Problems To achieve the above object, the present invention provides a method for manufacturing a wear-resistant sliding member in which a whisker-dispersed ceramic sliding layer in which whiskers are dispersed is formed on a ceramic substrate. ,
A ceramic base material containing silicon nitride and a sintering aid, and a whisker-dispersed ceramic sliding layer material, either one of which is formed into granules and put into a molding machine. Is pressed at a low pressure such that the granules are not broken, and the other material is placed thereon, and then an assembly of these two materials is pressed at a predetermined high pressure to form a compact for sintering. And forming a sliding member by sintering the molded body for sintering to provide a method of manufacturing a wear-resistant sliding member.

According to the present invention, for example, in a case where a ceramic base material is granulated and put into a molding machine to perform pressure molding at a low pressure, the ceramic substrate material layer in the molding machine after the low pressure molding is used. While the upper surface is kept in the granular state, it is formed into a shape corresponding to the sliding surface of the sliding member. For this reason, many voids are formed between the granules on the surface of the ceramic base material layer. Next, the whisker-dispersed ceramic sliding layer material is filled on the upper surface of such a ceramic base material layer and then press-molded. Into the voids between the granules, and a boundary between the two layers forms a complex portion of both materials. Then, the molded body for sintering in which such intricate boundaries are formed is sintered to produce a sliding member. Such a sliding member has a structure in which both layers are entangled at the boundary between the whisker-dispersed ceramic sliding layer and the ceramic base material layer, so that both layers are strongly bonded. Therefore, the reliability of the sliding member can be improved. In addition, since the upper surface of the ceramic base material layer has a shape substantially equal to the sliding surface due to the low pressure molding as described above, the thickness of the whisker dispersed ceramic sliding layer is made uniform as described above. (See FIGS. 3A to 3D). Therefore, it is not necessary to additionally form an expensive whisker-dispersed ceramic sliding layer in order to guarantee a required thickness, and thus the manufacturing cost of the sliding member can be reduced.

The same applies to the case where the whisker-dispersed ceramic sliding layer material is granulated and put into a molding machine, which is press-formed at a low pressure, and then a ceramic base material is placed thereon and pressed at a high pressure.

[Examples] Examples of the present invention will be specifically described below.

<First Example> 5 wt% of Y ₂ O ₃ and ₃ wt% of Al ₂ O ₃ were contained (sintering aid).
After mixing and pulverizing sufficiently 2% of PVA as a binder to a ceramic base material having a balance of Si ₃ N ₄ , the mixture is pulverized and then dried by a spray drying method to obtain a homogeneous ceramic base having a particle size of 150 to 200 μm. Granules of the material were prepared. Then, as shown in FIG. 1 (a), on the bottom plate 2 of the press molding machine 1,
The above granular ceramic base material 3 is filled and pressed.
Temporary molding was performed at 20 kg / cm ² . At this time, the upper surface of the ceramic base material layer 3 is formed in a state substantially similar to a predetermined shape (shape of the compression surface of the piston) corresponding to the sliding surface of the sliding member. Granules were not crushed at all. Incidentally, in the case of performing various varied such preformed pressing pressure, indicated by the curve G ₁ in FIG. 6 the characteristics for the press pressure of the ceramic base material layer surface roughness.
From these characteristics, when preforming the ceramic base material, if the pressing pressure is set within a predetermined range of approximately 20 kg / cm ² or less, the molding surface is almost the same as the pressing surface without breaking the granules. It can be seen that it can be formed into the shape of.

Next, 10 wt% of MgO was contained as a sintering aid, and the rest was Si ₃ N ₄
5% by weight of SiC whisker (fiber type single crystal)
In addition, the mixture was mixed well to prepare a whisker-dispersed ceramic sliding layer material, which was formed into granules having a particle size of 50 to 200 μm.
Then, as shown in FIG. 1 (b), the granular whisker-dispersed ceramic sliding layer material 4 is filled on the ceramic base material layer 3 temporarily molded at a low pressure in the molding machine 1,
Press molding was performed using a piston (not shown) at a press pressure of 0.5 ton / cm ² to obtain a molded body P for sintering as shown in FIG. 1 (c).

In this case, a pressed body of the ceramic base layer 3 and the whisker-dispersed ceramic sliding layer 4 is formed as shown in FIG. As described above, the boundary portion 5 between the ceramic base layer 3 and the whisker-dispersed ceramic sliding layer 4 has slight irregularities, and such irregularities are formed after press molding in FIG. 4 (c).
As shown in FIG. Since such a boundary portion 5 is formed, the contact area between the whisker-dispersed ceramic sliding layer 4 and the ceramic base layer 3 increases, and
4,3 connectivity is enhanced. In addition, FIG.
In the manufacturing method as shown in (c), a pressed body of the ceramic base layer 3 and the whisker-dispersed ceramic sliding layer 4 as shown in FIG. 5 (a) is formed. As shown in FIGS. 4B and 4C, the boundary 6 between the ceramic base layer 3 and the whisker-dispersed ceramic sliding layer 4 is completely flattened. Since the area is small and a gap is formed between the two layers 4 and 3 to a small extent, the bonding between the two layers 4 and 3 becomes very poor.

Then, the sintering compact P was sintered at 1800 ° C. for 3 hours under a 1 atm N ₂ gas atmosphere, and a sliding member Q (sintered body) as shown in FIG. Made.

As described above, in the sliding member Q, a portion having a structure in which the two layers 4, 3 are entangled is formed at the boundary between the whisker-dispersed ceramic sliding layer 4 and the ceramic base material layer 3 as described above. 4,3 were strongly bonded and had sufficient strength. The thickness of the whisker-dispersed ceramic sliding layer 4 was uniform.

In addition, the low pressure pressing pressure of the ceramic base material 3 is set to 50 kg / c.
It performed preformed as m ^2, sliding member and other conditions were made in the same as described above, was easily destroyed by slight impact.

<Second Embodiment> Hereinafter, a second embodiment of the present invention will be described, although not particularly shown.

Prepared by adding 10 wt% of SiC whiskers to a material containing 5 wt% of Y ₂ O ₃ , ₃ wt% of Al ₂ O _3, and 3 wt% of AlN (these are sintering aids) and the balance being Si ₃ N ₄ The whisker-dispersed ceramic sliding layer material was formed into granules having a particle size of 50 to 350 μm using paraffin.

One method, granules having a particle size of 50 to 200 μm containing a ceramic base material containing 5 wt% of Y ₂ O ₃ and 5 wt% of Al ₂ O ₃ (hereinafter referred to as sintering aid) and the balance being Si ₃ N ₄ Molded.

Then, contrary to the case of the first embodiment, first, the above-mentioned granular whisker-dispersed ceramic sliding layer material was filled in a press molding machine and preliminarily molded at a press pressure of 5 kg / cm ² . Incidentally, in the case of performing various varied such preformed the pressing pressure, showing the characteristics for press pressure of whiskers dispersed ceramic sliding layer surface roughness curve G ₂ in FIG. 6. From such characteristics, in the case of preformed whiskers dispersed ceramic sliding layer material is set within approximately 10 kg / cm ² or less in a predetermined range of the press pressure, substantially the molding surface without breaking the granules Press It can be seen that it can be formed into the same shape as the surface.

Then, the ceramic base material is filled on the whisker-dispersed ceramic sliding layer material, and the pressing pressure is 0.3 ton / c.
press molding was carried out in m ^2. Next, a sliding member (sintered body) was manufactured by sintering at 1750 ° C. for 2 hours in an N ₂ atmosphere at 8 atm.

In the sliding member manufactured in this manner, the whisker-dispersed ceramic sliding layer and the ceramic base material layer were firmly bonded as in the case of the first embodiment.

The sliding member manufactured by temporarily forming the whisker-dispersed ceramic sliding layer material at a press pressure of 20 kg / cm ² and under the same conditions as the above under other conditions was broken by a slight impact.

<Comparative Example> A mixed material was prepared by mixing the whisker-dispersed ceramic sliding layer material used in the first example and the ceramic base material by 50 wt%. Then, the above-mentioned ceramic base material is filled into a press molding machine and preliminarily molded at a press pressure of 50 kg / cm ² , then a predetermined amount of the above-mentioned mixed material is added, and temporarily molded again at a press pressure of 50 kg / cm ^2. Fill the whisker-dispersed ceramic sliding layer material, press-mold at 0.5 ton / cm ² to produce a compact for sintering, and sinter the compact for sintering under the same conditions as in the first embodiment. Then, a sliding member was manufactured. However, this sliding member was broken by a slight impact before the strength test was performed. From this, it can be seen that the effect of the present invention cannot be obtained simply by sintering a mixture of both materials between the whisker-dispersed ceramic sliding layer material and the ceramic base material. .

[Brief description of the drawings]

FIGS. 1 (a) to 1 (d) show steps of manufacturing a sliding member having a two-layer structure composed of a whisker-dispersed ceramic sliding layer and a ceramic base material layer by the manufacturing method according to the present invention. FIG. 2 (a) to 2 (d) are process diagrams showing respective steps of manufacturing a sliding member having a two-layer structure by a conventional manufacturing method. FIGS. 3 (a) to 3 (d) respectively show that a ceramic base material is first press-molded in a press molding machine, and a whisker-dispersed ceramic sliding layer material is filled thereon and press-molded. It is process drawing which shows each process at the time of forming the molded object for sintering and manufacturing a sliding member of a two-layer structure. FIGS. 4 (a) to (c) are FIGS. 1 (a) to (c), respectively.
FIG. 3 is a view showing a shape of a boundary portion between a whisker-dispersed ceramic sliding layer and a ceramic base layer when a molded body for sintering is manufactured by the manufacturing method according to the present invention as shown in FIG. FIGS. 5 (a) to (c) show FIGS. 3 (a) to (c), respectively.
FIG. 3 is a view showing a shape of a boundary portion between a whisker-dispersed ceramic sliding layer and a ceramic base material layer when a molded body for sintering is manufactured by the manufacturing method shown in FIG. FIG. 6 is a diagram showing characteristics of surface roughness with respect to pressing pressure during tentative molding of a whisker-dispersed ceramic sliding layer material and a ceramic base material. P, P ', P "... Sintered compact, Q, Q', Q" ... Sliding member,
1 ... press molding machine, 2 ... bottom plate, 3 ... ceramic base material, 4 ... whisker dispersed ceramic sliding layer, 5, 6 ... boundary area.

Claims (1)

(57) [Claims] 1. A method for manufacturing a wear-resistant sliding member in which a whisker-dispersed ceramic sliding layer in which whiskers are dispersed is formed on a ceramic substrate, comprising: a ceramic substrate containing silicon nitride and a sintering aid. One of the two materials, the material and the whisker-dispersed ceramic sliding layer material, is formed into a granule and put into a molding machine, and this material is pressed under a low pressure so that the granules are not broken. After placing the other material thereon, an assembly of these two types of materials is pressed and formed at a predetermined high pressure to form a molded body for sintering, and the molded body for sintering is sintered. A method for producing a wear-resistant sliding member, characterized by producing a sliding member by performing the following steps.