JPH10287484A - Ceramic part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ceramic part that has high stiffness and can be readily given its shape by coating a part or the whole of outermost surface of the ceramic with a brass layer mainly comprising the β-CuZn phase having a body- centered cubic lattice. SOLUTION: This ceramic part (for example, a square bar 1 or a cylinder 2) is coated with the brass layer 5 mainly comprising the β-CuZn phase having the body centered cubic lattice (6: the shape given face). This ceramic part is produced by forming a metallizing layer 4 on the ceramic surface 3 by the vapor phase layer-forming technique and the brass layer 5 is formed on the metallized layer 4 by the electroplating. On the ceramic surface, a metallizing layer 4 is formed in a thickness of <=5 μm and the brass layer 5 is formed on the metallizing layer 4 in a thickness of 5-500 μm. In a preferred embodiment, the metallizing layer is composed of two layers, the first later contacting with the ceramic is a metallic layer containing Cr, while the second latter contacting with the brass layer is a metallic later containing Cu.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machine structural part requiring high rigidity and high shape accuracy.

[0002]

2. Description of the Related Art As a material constituting a precision machine tool and a precision measuring device, deflection due to its own weight and external force is small.
A material having a small dimensional change with respect to a temperature change is required.
In addition, characteristics such as rusting under the use environment are required. Structural ceramics such as alumina, silicon nitride, sialon, and silicon carbide are lighter, have a higher Young's modulus, a lower coefficient of thermal expansion, and have less dimensional change over time than typical metal materials such as carbon steel. There are features. For this reason, ceramics are being used in particular for mechanical structural members that require high precision. However, these ceramics are difficult to process without exception, and in order to give the required shape as a mechanical structural member, long time processing with a diamond whetstone etc. is required, resulting in high cost of the product. It is. Also, if the processing accuracy is severe,
In some cases, the required shape cannot be provided.

To solve the above problems, machinable ceramics based on alumina have been developed. However, this material is easy to process, but cannot be applied to parts requiring a low Young's modulus and rigidity. The concept of providing a ceramic alloy with a copper alloy layer to produce a precision processed part is disclosed in Japanese Patent Application Laid-Open No. 8-91968, but leaves room for improvement in shape imparting properties and processing reliability. Was difficult to apply. That is, there is no suggestion of an alloy composition in consideration of workability. The metallization layer provided between the ceramic and alloy layers is also assumed to be metallized by powder application and baking. Considering the application variation over a large area, the minimum thickness required to obtain sufficient adhesion is set to 5 μm. doing.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a ceramic member which has high rigidity and can be easily provided with a shape.

[0005]

Means for Solving the Problems and Embodiments of the Invention According to the present invention, a part or all of the outermost surface of a ceramic is coated with a brass layer mainly composed of β-CuZn having a body-centered cubic lattice. A ceramic member. Heretofore, there has been no example in which β-CuZn having excellent workability is formed on a ceramic surface. The present invention can be realized by providing a metallized layer on a ceramic surface by a vapor deposition method and forming a brass layer thereon by electroplating.

The ceramics to which the present invention is directed are high-rigidity ceramics having a Young's modulus of 20,000 kgf / mm ² or more, such as alumina, silicon nitride, sialon, and silicon carbide. Alumina, a representative of high-rigidity ceramics, has a Young's modulus of 20
In contrast to 000 to 38000 kgf / mm ² , the Young's modulus of β-CuZn brass, which is a typical metal material, is 10500 kgf / mm ² . The thermal expansion coefficient near room sialon is representative of a low thermal expansion ceramic whereas a 1.5 × 10 ^-6 / ° C., the thermal expansion coefficient of beta-CuZn brass is 18 × 10 ^-6 / ° C.. These differences in physical properties are the reasons why ceramics are used for members that require a small dimensional change due to external force or temperature change.

On the other hand, with regard to workability, brass is remarkably superior to ceramics, and can be processed at high speed with ordinary tool steel. On the other hand, processing of ceramics requires long-time processing using a diamond grindstone. The present inventor has proposed a method of easily performing required processing without impairing the high rigidity and low thermal expansion characteristics of structural ceramics, by providing a brass layer having excellent workability on a surface to be processed of the ceramic, It has been devised to obtain the required shape by processing. That is, the mechanical properties are shared by ceramics, and the shape is designed by brass. Although the ceramic member of the present invention is conceptually shown in FIG. 1, the shape accuracy of the ceramic itself is not required, and the final shape is provided by a brass layer.

Hereinafter, details of the present invention will be described. The ceramic used in the present invention is obtained by densifying a powder compact by normal pressure sintering or pressure sintering, performing a roughing process as necessary, and finishing it into a shape close to a final product. The Young's modulus of the ceramics used in the present invention is set to 20000 kgf / mm ² or more because a material having a Young's modulus lower than that is low in rigidity and is not suitable as a structural material.

[0009] The surface of the above ceramics is metallized and electroplated. As a method of metallizing ceramics, for example, there is a method in which a slurry of a metal powder such as Ag-Cu-Ti is applied and baked, but this method is not suitable for applying thinly and uniformly over a large area. For the purpose of the present invention, metallization by a vapor phase film forming method such as sputtering or ion plating is suitable. In the case of alumina, silicon nitride, sialon, and silicon carbide, which are typically used as structural ceramics, a metal layer made of Cr or an alloy containing Cr is suitable as the metallized layer. The metallization layer may be a single layer of the above metal layer, but in order to facilitate subsequent brass plating, Cu
May be formed as the second layer. Each of them is formed by a vapor deposition method, but the sum of the thicknesses of the deposition layers is limited to 5 μm or less. In the vapor deposition method, the thickness is 5μ.
If it exceeds m, peeling is likely to occur due to accumulation of internal stress, and sufficient adhesion cannot be obtained.

The brass used in the present invention is a brass having a β-CuZn phase as a main phase. Main phase means that the phase accounts for 50 vol% or more. For Cu-Zn binary alloys, 35 ~
Β-CuZn phase is obtained in the range of 60wt% Zn. If the composition is 35wt% Zn or less, α-CuZn becomes the main phase, and the alloy is inferior in workability. β-CuZn has a crystal structure of a body-centered cubic lattice, and has excellent workability due to a work hardening phenomenon.

Electroplating is suitable for forming the brass layer. By using electroplating, it is possible to coat the brass layer even in places where coating is difficult, such as the inner peripheral surface of a cylinder. As a plating bath, a pyrophosphoric acid bath or a cyanide bath can be used. The thickness of the plated brass layer of the present invention is 5 μm or more and 500 μm or more.
m or less. The reason for this is that the minimum thickness of the brass layer that can withstand machining is 5 μm, and plating exceeding 500 μm is usually difficult to avoid problems such as peeling due to accumulation of internal stress. Also, for ceramic members
If the brass layer is provided in excess of 500 μm, the low rigidity or high thermal expansion properties of brass cannot be ignored depending on the member, which is contrary to the gist of the present invention.

Examples of the shaping process for the brass layer include, but are not limited to, shaping by a machining center, flattening by a surface grinder, and rounding by a cylindrical grinder. Less than,
The present invention will be described by way of examples.

[0013]

EXAMPLE A ceramic member conceptually shown in FIG. 1 was produced. A ceramic square 1 and a ceramic cylinder 2 were prepared from alumina having a Young's modulus of 38000 kgf / mm ² by a normal pressure sintering method. The size of the timber is 50x50mm in cross section and 200mm in length, and the size of the cylinder is 120mm in outside diameter and 100mm in inside diameter
And the height is 40mm. These ceramics are processed using a diamond grindstone to obtain parallelism or roundness.
The finished state was about 30 μm. Next, a metallized layer 4 having a thickness of 5 μm or less was provided on the ceramic surface 3 by an ion plating method. The acceleration voltage during ion plating was 1 kV. Subsequently, the metallized layer is energized in a plating bath containing cuprous cyanide and zinc cyanide,
A brass layer 5 having a thickness of 100 μm was provided. The conditions for the electroplating were 8 hours at a current density of 1 A / dm ² . This brass layer was subjected to a finishing process to obtain a final shape-imparting surface 6. As for the finishing process, in the case of a square bar, a process of finishing the parallelism of the side surface to 1 μm or less is imposed, and in the case of a cylinder, the roundness of the inner peripheral surface is set to 1.
Processing to finish to μm or less was imposed.

Table 1 shows the metallizing conditions, the composition of the brass layer, and the finishing accuracy when the brass layer was processed for a certain period of time. The composition of the brass layer is Cu
The composition was -30 wt% Zn and Cu-45 wt% Zn from which a β phase was obtained. Metallization by ion plating (IP) is 0.
The case of a single Cr layer of 5 μm and the case of providing a 0.1 μm thick Cr layer on the first layer and forming a 2 μm thick Cu layer thereon are shown. As a comparative example of metallization, a case where a paste of an Ag-Cu-Ti alloy powder was applied to a ceramic surface and fired in a vacuum was shown. The processing accuracy was compared with that when the ceramic itself was processed (square material E and cylinder B).

As shown in the table, when metallization is performed by ion plating, a brass layer made of β phase of Cu-45wt% Zn is provided on the metallization, and when the brass layer is processed, a ceramic having a specified dimensional accuracy is obtained. A member was obtained.

[0016]

[Table 1]

[0017]

By applying the brass-coated ceramic of the present invention, it is possible to provide a highly rigid ceramic member having high shape accuracy. Also, since the shaping of the brass surface can be performed in a shorter time than the shaping of ceramics,
The productivity of the members is improved.

[Brief description of the drawings]

1 (a) shows a conceptual diagram of a brass-coated ceramic square, FIG. 1 (b) shows a conceptual diagram of a brass-coated ceramic cylinder, and FIG. 1 (c) shows an enlarged explanatory view of a brass-coated surface. Show.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ceramic square material 2 ... Ceramic cylinder 3 ... Ceramic surface 4 ... Metallized layer 5 ... Brass layer 6 ... Shape imparting surface

Claims (4)

[Claims] 1. A ceramic member characterized in that part or all of the outermost surface of the ceramic is coated with a brass layer having β-CuZn as a main phase and having a body-centered cubic lattice. 2. A metallized layer having a thickness of 5 μm or less is formed on a ceramic surface, and a thickness of 5 μm is formed on the metallized layer.
The ceramic member according to claim 1, wherein a brass layer having a thickness of not less than μm and not more than 500 μm is formed. 3. The method according to claim 1, wherein the metallized layer in contact with the ceramic is Cr.
The ceramic member according to claim 2, wherein the ceramic member is a metal layer containing: 4. The metallized layer comprises two layers, the first metallized layer in contact with the ceramics comprises a metal layer containing Cr, and the second metallized layer in contact with the brass layer comprises a metal layer containing Cu. The ceramic member according to claim 2, wherein: