JPS6230152B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to sialon sintered materials and sialon-based sintered materials containing sialon as a main component (hereinafter referred to as This invention relates to a sintering method for sialon-based sintered materials. In recent years, various new ceramics, including silicon nitride (hereinafter referred to as Si ₃ N ₄ ) and those with a β-type crystal structure, have been used as structural materials for turbine blades and other materials.
A compound in which part of Si in Si ₃ N ₄ is replaced with Al and part of N is replaced with O, that is, the composition formula: Si _6-z Al _z O _z N _8-z (0<z≦4.3 ), and a part of the Si in the crystal lattice of Si ₃ N ₄ , which has an α-type crystal structure, is replaced with Al.
Then, a part of N is replaced with O, and one or more of Li, Na, Ca, Mg, Y, and rare earth elements with small atomic radius are placed in the interstitial position (in the composition formula below, A sintered compound composed of α-sialon represented by the composition formula: Mx (Si, Al) ₁₂ (O, N) ₁₆ (where 0<x≦2) materials, as well as Si ₃ N ₄ -based sintered materials and Sialon-based sintered materials that have these components as their main components, are attracting attention. However, when producing these sintered materials, especially sialon-based sintered materials, (a) if the compacted compact is directly sintered in a state embedded in Si ₃ N ₄ powder or sialon powder, the above-mentioned If the surface portion of the compacted compact reacts with the sintering atmosphere and the buried powder to form a surface-altered layer, and if there are holes or depressions on the surface of the compact, the buried powder may be buried in these areas. powder gets into the
During shrinkage during sintering, these powders are strongly entrapped and not only difficult to remove, but also cause deformation. (b) When the compacted compact is sintered in a graphite crucible, a reaction occurs between the surface of the compact and the sintering atmosphere, forming a surface-altered layer. Although this is not as pronounced as in graphite crucibles, it also occurs when sintering in Si ₃ N ₄ -based sintered material crucibles. Therefore, after sintering the sialon-based sintered material, it is necessary to remove the surface-altered layer and powder-incorporated layer formed on the surface. In addition to the fact that the sialon-based sintered material is difficult to grind, its removal requires time and effort. Therefore, from the above-mentioned viewpoint, the present inventors conducted research on the sintering mode of the sialon-based sintered material in order to obtain a sialon-based sintered material free from the formation of altered layers or powder-incorporated layers on the surface portion. As the embodiment is shown in a schematic longitudinal cross-sectional view in FIG. was coated with a mixed powder having the same or similar composition to the compacted compact.
A container 2 made of Si ₃ N _4- based sintered material (including Si ₃ N ₄ sintered material) is filled with Si ₃ N ₄ powder or a mixed powder mainly composed of Si ₃ N ₄ powder as an underlay 3. Then, place the container 2 in the graphite crucible 4,
When the graphite crucible in this state is charged in a buried state in the Si ₃ N ₄ powder 5 or the mixed powder 5 whose main component is Si ₃ N ₄ powder, and is sintered in a nitrogen-containing atmosphere, the sintering progresses. The atmosphere surrounding the compacted compact contains volatile components of the compact, such as Si ₃ N ₄
This gas is similar to SiO gas, etc., which is generated when a part of Since it is presumed that there will be no formation of layers, a sialon-based sintered material with good surface properties can be obtained.Moreover, since the compacted powder is not buried in the powder, They found that there was no formation of an embedded layer. This invention was made based on the above findings, and will be specifically explained below using Examples. Examples As raw material powders, Si ₃ N ₄ powder (α phase content: 90% by weight) with an average particle size of 0.8 μm and α-
Al ₂ O ₃ powder, 1.0μm Y ₂ O ₃ powder, both the same
1.5μm AlN powder, TiCN (TiC/TiN=2/
8. Weight ratio) powder and carbon black powder were prepared, and these raw material powders were blended into the composition shown in Table 1, and 4% by weight of paraffin as a binder was added to the blended powder. After wet mixing in a ball mill for 3 days, drying,
Then, after press-molding the resulting mixed powder,
Molded green compacts a to e were produced by holding the powder at a temperature of 800° C. for 1 hour in vacuum to volatilize paraffin as a binder. Next, using these compacted compacts a to e, the following conditions are established: (1) The compacted compact a is placed in a container made of a sialon sintered material having the same composition as the compact compact a. Inside,
Si ₃ N ₄ powder is laid out and placed, and the entire container is placed in a graphite crucible by immersing it in the Si ₃ N ₄ powder (hereinafter referred to as the method 1 of the present invention), (2) compacted powder body b and In a container made of Si ₃ N ₄ sintered material, whose inner surface was coated with a mixed powder with the same composition,
Place the compacted compact b on Si ₃ N ₄ powder and charge the entire container into a graphite crucible by immersing it in the Si ₃ N ₄ powder (hereinafter referred to as the method 2 of the present invention); (3) In a container made of Si ₃ N ₄ sintered material whose inner surface was coated with a mixed powder having the same composition as the compacted powder c,
Place the compacted compact c on a sheet of Si ₃ N ₄ powder, and charge the entire container into a graphite crucible by immersing it in the Si ₃ N ₄ powder (hereinafter referred to as the method 3 of the present invention); (4) In a container made of Si ₃ N ₄ sintered material whose inner surface is coated with a mixed powder having the same composition as the compacted compact a,
Place the compacted compact d on a sheet of Si ₃ N ₄ powder, and charge the entire container into a graphite crucible by immersing it in the Si ₃ N ₄ powder (hereinafter referred to as the method 4 of the present invention); (5) In a container made of Si ₃ N ₄ sintered material whose inner surface was coated with a mixed powder having the same composition as the compacted powder c,
Place the compacted compact e with Si ₃ N ₄ powder, and charge the entire container into a graphite crucible by immersing it in the Si ₃ N ₄ powder (hereinafter referred to as the method 5 of the present invention), (6) The compacted powder compact a is buried in Si ₃ N ₄ powder and charged into a graphite crucible (hereinafter referred to as Comparative Method 1). (7) Same as the method 1 of the present invention except that the container is made of graphite (8) Charge the compacted powder compact b under the same conditions as in method 1 of the present invention (hereinafter referred to as comparative method 2), except that the container is made of graphite (hereinafter referred to as comparative method 2). (referred to as comparative method 3), (9) The compacted compact d was charged under the same conditions as method 4 of the present invention, except that the container was made of graphite (therefore,
In this case, the inner surface of the container is coated with the same composition as the compacted compact a, hereinafter referred to as comparative method 4). (10) The compacted compact e is placed in a container made of Si ₃ N ₄ sintered material.
Si ₃ N ₄ powder is laid out and placed, and the entire container is immersed in the Si ₃ N ₄ powder and charged into a graphite crucible (hereinafter referred to as Comparative Method 5), among the above (1) to (10) Methods 1 to 5 of the present invention are performed by sintering in a nitrogen atmosphere of 1 atm at a temperature of 1700°C for 2 hours under any of the following conditions.

【table】

【table】

[Table] Comparative Methods 1 to 5 were carried out, the cross section of the resulting sialon-based sintered material was polished, and the average thickness of the surface altered layer was measured. These results are shown in Table 2. From the results shown in Table 2, in the sialon-based sintered materials obtained by methods 1 to 5 of the present invention, no surface deterioration layer was observed at all, whereas in the comparative methods 1 to 5, no surface deterioration layer was observed. In all cases, the formation of a surface-altered layer was observed. As described above, according to the method of the present invention, the sialon-based sintered material after sintering does not have a surface altered layer or a powder-incorporated layer, and therefore can be sintered without grinding or the like. This brings about practical effects such as being able to put it to practical use in its original state.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical sectional view showing an embodiment of the present invention. In the drawings, 1... Molded compact, 2... Container, 3... Underlay, 4... Graphite crucible, 5... Powder for burial.

Claims (1)

[Claims] 1. When sintering the sialon-based sintered material,
The compacted powder body is first coated with a container made of a sialon-based sintered material having the same or similar composition as the compacted compact, or the inner surface is coated with a mixed powder having the same or similar composition as the compacted compact. Silicon nitride powder or a mixed powder containing silicon nitride powder as a main component is placed in a container made of a silicon nitride-based sintered material, and then the container is placed in a graphite crucible, and silicon nitride powder, silicon nitride powder, Alternatively, a method for sintering a sialon-based sintered material, which is characterized in that it is charged in a mixed powder containing silicon nitride powder as a main component, and the graphite crucible in this state is sintered in a nitrogen-containing atmosphere. .