JPH0524111B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for surface treatment of non-oxide ceramic structures.

[Conventional technology]

Conventionally, when manufacturing a ceramic structure, a grinding process is performed after firing in order to ensure a predetermined dimensional accuracy. At this time, machining scratches remain on the surface of the ceramic structure, causing a decrease in strength.
Therefore, after machining, annealing treatment is performed to dull the sharp surfaces of machining scratches and cracks caused by machining, thereby attempting to restore strength.

[Problem to be solved by the invention]

By the way, this annealing treatment takes advantage of the softening of the glass phase, so it is carried out at a relatively low temperature (1000 to 1300℃. Therefore, in the case of the conventional method, the crack at the tip of the machining scratch closes, and it is relatively small. Although it is effective against large machining scratches, it has not been able to significantly dull relatively large machining scratches or even completely remove them.

Therefore, it has been desired to develop a method for completely removing processing scratches from such ceramic structures.

The present invention has been made in order to solve the problems of the prior art described above. An object of the present invention is to provide a method for surface treatment of ceramic structures.

[Means to solve the problem]

According to the present invention, such object is a method for surface treatment of a non-oxide ceramic structure for removing finishing scratches on the non-oxide ceramic structure, the method comprising: inactivating the non-oxide ceramic structure; In a gas atmosphere, the temperature is raised at normal pressure to a temperature range above the temperature at which the non-oxide ceramic and the glass phase constituting the non-oxide ceramic structure soften and below the firing temperature, and then heated at 5 to 10 atm. This is achieved by a surface treatment method for non-oxide ceramic structures characterized by applying pressure and annealing.

In the present invention, silicon nitride, silicon carbide, boron nitride, etc. can be used as the main material of the non-oxide ceramic structure.

An inert gas atmosphere is used as the annealing atmosphere. This prevents corrosion such as oxidation on the surface of the non-oxide ceramic structure and also prevents decomposition of the non-oxide ceramic.
As the inert gas, nitrogen gas, argon gas, etc. can be used.

The annealing temperature must be above the temperature at which the glass phase and the non-oxide ceramic soften, and below the firing temperature of the non-oxide ceramic structure (however, not exceeding the firing temperature). be. For example, when the non-oxide ceramic is silicon nitride, a temperature of 1600°C to 1800°C is appropriate.

Further, the annealing pressure must be 5 to 10 atmospheres. This is to prevent the glass phase and non-oxide ceramics from melting and decomposing in the above temperature range.

A good pressure pattern is to use normal pressure (1 atm) up to the melt deposition temperature of non-oxide ceramics, and then apply pressure.

[Function and effect of the invention]

According to the surface treatment method for a non-oxide ceramic structure of the present invention, since the treatment is performed at a higher temperature than conventionally,
Not only glass phases but also non-oxide ceramics are deposited by melting. Because of this, the cracks are completely removed and
Strength is greatly improved.

Furthermore, since the pressure is applied at high temperatures, the glass phase and non-oxide ceramics do not decompose, and therefore, strength does not decrease due to high temperatures.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Silicon nitride is used as non-oxide ceramics, sintering aids such as yttrium oxide (Y ₂ O ₃ ) and aluminum oxide (A ₂ O ₃ ) are added, and after molding into a predetermined shape, it is heated at a temperature of approximately 1800°C. It was fired to obtain a silicon nitride structure. Next, the surface of this silicon nitride structure was ground to a predetermined size. The first sketch of the processed surface of the silicon nitride structure at this time is
It is a diagram. As can be seen from FIG. 1, after grinding, there are machining scratches 1 on the grindstone and cracks 2 formed at the tip of the machining scratches 1.

Using this silicon nitride structure, surface treatment was performed under the following conditions.

First, a test piece of a silicon nitride structure was placed in a processing furnace, and the inside was made into a nitrogen gas atmosphere. In this state, the inside of the processing furnace is heated to a predetermined temperature, and the inside of the furnace is
It was treated and annealed using the same pressure pattern.

At this time, the pressure pattern is as shown in Figure 2, A pattern: normal pressure (1 atm) up to 1600°C.
After that, the pressure was 10 atm, pattern B: 10 atm all the time from low temperature to high temperature, and pattern C: normal pressure (1 atm) all the time.

In addition, the maximum heating temperature is 1300℃, 1500℃, 1600℃ for each pressure pattern above.
Five different temperatures were tested: ℃, 1700℃, and 1800℃.

When the bending strength (Kg/mm) of the silicon nitride structure test piece obtained as a result was examined, the results shown in FIG. 3 were obtained.

From FIG. 3, it can be seen that the pressure pattern is A pattern and heating to 1600°C to 1800°C is most excellent in improving strength.

The reason for this is that, first of all, regarding the processing (heating) temperature, up to about 1500°C, only the melt precipitation of the glass phase occurs, but the melt precipitation of silicon nitride does not occur.
Therefore, as shown in FIG. 4, the crack 2 caused by the machining scratch and the tip 3 of the machining scratch 1 are filled with this glass phase. In this case, although the strength is improved compared to the case without treatment, the strength of the glass phase is weaker than that of silicon nitride, so the improvement in strength is not sufficient and most of the processing scratches remain. Therefore, the treatment temperature needs to be 1600° C. or higher, at which silicon nitride is dissolved and deposited, and 1800° C. or lower, which is lower than the decomposition temperature of silicon nitride.

Furthermore, in the case of pattern C, when the pressure pattern is 1600° C. or higher, it is not possible to prevent the decomposition that starts at the same time as the dissolution and precipitation of silicon nitride. Therefore, C
For patterns, 1700 as shown in Figure 3.
As the temperature rises to 1800°C, the decomposition of silicon nitride becomes more intense, the surface becomes rough, and the strength improvement effect is halved.

In the case of pattern B, although the strength is slightly improved compared to the case where no pressure is applied, it is understood that the force that tends to dissolve and diffuse silicon nitride is suppressed, and therefore the strength improvement effect is small.

On the other hand, in the case of pattern A according to the present invention, the third
As shown in the figure, since the pressurization is started at the melt precipitation and decomposition start temperature of silicon nitride, the most desirable surface condition is achieved without inhibiting the precipitation and diffusion of silicon nitride as in pattern B.

FIG. 5 shows the processed surface of the test piece treated with this A pattern. As is clear from FIG. 5, not only the glass phase but also silicon nitride itself is precipitated, and not only the cracks but also the machining scratches are completely eliminated.

Therefore, according to the surface treatment method for a non-oxide ceramic structure of the present invention, the machining scratches are almost completely filled, the polar radius of the machining scratches increases, and the machining scratches are filled mainly with silicon nitride. This greatly improves the strength. This result is also clear from FIG.

Although specific embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and includes various embodiments within the scope of the claims. .

For example, since silicon nitride was used as the non-oxide ceramic in the example, the treatment temperature was set at 1600°C.
~1800°C, but this processing temperature will vary depending on the material. The treatment temperature may be set to be higher than the temperature at which the non-oxide ceramic starts dissolution precipitation, and lower than the temperature at which the non-oxide ceramic decomposes.

Further, in the examples, 10 atmospheres was used as the pressing force, but this pressing force can be set to an appropriate value in consideration of the material, the size of the non-oxide ceramic structure, etc.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a processed surface of a silicon nitride structure in an untreated state, FIG. 2 is a graph showing pressure patterns according to an embodiment of the present invention, and FIG. 3 is a graph showing three types of pressure patterns according to an embodiment of the present invention. FIG. 4 is a schematic diagram showing the processed surface of a silicon nitride structure when conventional surface treatment is applied, and FIG. 5 is an example of the present invention. FIG. 2 is a schematic diagram showing a processed surface of a silicon nitride structure when surface treatment according to the above is performed. 1...Processing scratches, 2...Cracks, 3...
...The tip of the machining scratch.

Claims (1)

[Scope of Claims] 1. A method for surface treatment of a non-oxide ceramic structure for removing finishing scratches on the non-oxide ceramic structure, comprising: placing the non-oxide ceramic structure in an inert gas atmosphere. After raising the temperature under normal pressure to a temperature range above the temperature at which the non-oxide ceramic and the glass phase constituting the non-oxide ceramic structure soften and below the firing temperature, a pressure of 5 to 10 atmospheres is applied. 1. A method for surface treatment of a non-oxide ceramic structure, which comprises annealing the structure.