JPH0631164B2 - Joining method for sintered silicon nitride - Google Patents

Description

The present invention relates to a method for joining silicon nitride sintered bodies.

(Prior Art) Nitride-based or carbide-based ceramics have
Due to its excellent properties such as heat resistance and wear resistance, application as a high temperature structural material has been attempted in various fields in recent years, and some have entered the stage of practical application.

These ceramics have the essential drawback of ceramics that they have high hardness and are brittle. For this reason,
It is generally difficult to directly machine a complex and large-sized product by machining the above-mentioned ceramics, and the cost required for this machining also increases. Therefore, a method of manufacturing a product by dividing the product into several members and then integrating the members into a product has been studied.

As a method for joining ceramic members, conventionally, a method of hot pressing with an adhesive agent interposed between the members or a method of applying an inorganic adhesive agent to the joint surfaces and baking it is generally adopted.

The former method of joining by hot pressing is not suitable for mass production because it is difficult to apply the joining of complicated shaped members due to the structure of the mold and the joining processing cost becomes high.

As the inorganic adhesive used in the latter method, phosphate-based adhesives, halide-based adhesives, silica gel-based adhesives, and alkali silicate-based adhesives are commercially available. All of these adhesives are applied to the surface of the joining member, but it is difficult to obtain an adhesive layer having a uniform thickness, and as a result, the dimensional accuracy of the ceramic product after joining becomes insufficient. Furthermore, at present, there remains a problem to be solved that the strength of the joint is lower than the strength of the ceramic member.

There is a metallizing method as a joining method having a higher joining strength than a joining method using an inorganic adhesive. This method includes baking a paste of molybdenum or tungsten powder added with metal powder such as manganese on the ceramic surface, baking copper sulfide on the ceramic surface, or spraying silver carbonate on the ceramic surface and thermally decomposing it. It is a method of joining ceramic members through a metallized layer formed by the above method. In this metallizing method, the heat resistance of the joint portion is extremely lowered above the heat resistant temperature of the metallized material.

(Technical Means for Solving the Problems) The present invention provides a method for joining a silicon nitride sintered body having a high joint strength.

According to the present invention, a silicon nitride sintered body containing an oxide-based sintering aid is hydrothermally treated, and a surface erosion layer of the obtained sintered body is butted and heated. A method of joining the body is provided.

Specific examples of the oxide-based sintering aid in the present invention include M
Examples thereof include oxides of metals such as g, Al, Zr, Be, Ti, Sc and Y, and oxides of rare earth elements such as La, Ce, Pr, Sm and Dy. Among these oxide-based sintering aids, oxides of Y and Al are preferably used. The content of the oxide-based sintering aid is usually 1 to 15% by weight. The silicon nitride sintered body may contain a non-oxide type sintering aid such as YN or AlN in addition to the above oxide type sintering aid. The content of the non-oxide type sintering aid is usually 5% by weight or less.

In the present invention, the silicon nitride sintered body processed into a predetermined shape is subjected to hydrothermal treatment by heating in water to form an erosion layer on the surface of the silicon nitride sintered body. Heating temperature is usually 100-50
The temperature is 0 ° C, preferably 200 to 400 ° C. The heating time is usually 2 to 100 hours, preferably 10 to 50 hours. The hydrothermal treatment is preferably performed in an autoclave. The erosion layer formed on the surface of the silicon nitride sintered body by this treatment is made of, for example, a hydrate of aluminum silicate when containing alumina as an oxide-based sintering aid, When it contains magnesia, it consists of a hydrate of magnesium silicate.

The thickness of the erosion layer can be arbitrarily controlled by changing the hydrothermal treatment conditions. That is, the thickness of the erosion layer increases as the treatment temperature is increased and the treatment time is increased.

In the present invention, the silicon nitride sintered bodies having the erosion layer formed on their surfaces by hydrothermal treatment are temporarily joined together by a method such as fitting, fastening or inserting, and then heated and joined. The heating temperature is usually 600 to 1600 ° C, preferably 800 to 14
It is 00 ° C. If the heating temperature is excessively low, sufficient sintering of the erosion layers does not occur and the joint strength decreases. Further, if the heating temperature is excessively high, the erosion layer is melted and it becomes difficult to obtain a uniform bonding layer. The atmosphere during heating is preferably an oxygen-containing atmosphere. Usually, it is preferable to heat the hydrothermally treated silicon nitride sintered body in an air atmosphere.

(Example) An example is shown below.

Example 1 Y ₂ O ₃ , Al ₂ O ₃ and Al as oxide-based sintering aids
Test piece of silicon nitride sintered body containing N (3 x 4 x
20 mm) in an autoclave at a temperature of 1300 ° C,
It was hydrothermally treated for 5 days under a pressure of 8.6 MPa.

The 3 × 4 mm surfaces of the treated test pieces were brought into contact with each other and heated in an air atmosphere at 1350 ° C. for 1 hour to bond them. The average bending strength (three-point bending test) of the joined portion of the joined test pieces was 19 kg / mm ² .

Example 2 The same method as in Example 1 was repeated except that the hydrothermal treatment was carried out at 300 ° C. under a pressure of 8.6 MPa for 1 day. The average bending strength of the test piece joint (3-point bending test) is 23.
It was kg / mm ² .

Claims (1)

[Claims] 1. A silicon nitride sintered body, characterized in that a silicon nitride sintered body containing an oxide-based sintering aid is hydrothermally treated, and a surface erosion layer of the obtained sintered body is butted against and heated. Joining method.