JPS638074B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to sialon-based ceramics that exhibit outstanding wear resistance when used as cutting tools, wear-resistant tools, and the like. In recent years, silicon nitride (hereinafter referred to as Si ₃ N ₄ )-based ceramics have attracted attention as materials for cutting tools and wear-resistant tools.
Since Si ₃ N ₄ is a compound with strong covalent bonding properties, it has poor sintering properties, so hot pressing is often used to manufacture it, and in this case it is difficult to manufacture products with complex shapes. , and productivity is low. _Furthermore , _β-
A compound in which part of the Si in the Si ₃ N ₄ lattice is replaced with Al and part of the N is replaced with O, that is, the composition formula: Si _6-z Al _z O _z N _8-z (O<z≦4.3), Attempts have also been made to use sialon-based ceramics whose main component is β-sialon, expressed by At present, it does not exhibit the desired wear resistance because it is not very high at about 92. Therefore, from the above-mentioned viewpoint, the present inventors focused on the conventional sialon-based ceramics containing β-sialon as a main component, and added high-quality materials to this ceramic without impairing its good sinterability. As a result of research to add hardness and ensure excellent wear resistance, (a) In addition to the above β-SiAlON, a part of the Si in the α-Si ₃ N ₄ lattice was replaced with Al and N Replace part of with O,
Furthermore, one or more of Li, Na, Ca, Mg, Y, and rare earth elements (hereinafter collectively referred to as M) enters into the same lattice, resulting in a solid solution structure. Compound, that is, compositional formula: M _x (Si, Al) ₁₂ (O, N) ₁₆ (where O<x≦
2) When α-sialon expressed as coexists,
The resulting ceramics have improved hardness and excellent wear resistance. In this case, the ratio of α-sialon to β-sialon (α/β) is preferably set to more than 25/75 to 95/5 in terms of capacity ratio. This is based on the reason that the effect of improving hardness is small, and on the other hand, when the ratio exceeds 95, sinterability decreases. In addition, β-Sialon is represented by the composition formula: Si _6-z Al _z O _z N _8-z as described above, and O<z≦4.3
This is because there is no composition with a z value exceeding 4.3, but even within this range, if z becomes large, coarse cavities will form in the ceramic. It is preferable that O<z≦2.0 because this tends to occur and the strength also decreases. Furthermore, α-SiAlON, as mentioned above,
Compositional formula: M _x (Si, Al) ₁₂ (O, N) ₁₆ ,
It exists under the condition O<x≦2, which means that x is 2
This is based on the reason that if the composition exceeds the above, M cannot be completely dissolved in solid solution while penetrating the lattice gaps. In addition, α−
It is assumed that the ratio of Si, Al, O, and N in Sialon changes depending on the type of M and the value of x, and is determined so that the positive and negative valences are equal. (b) The ceramics in which α-sialon and β-sialon coexist in (a) above contain the elements contained in M above, Si, and Al as bonding phase forming components.
When one or more of the oxides and nitrides (hereinafter collectively referred to as metal oxides/nitrides) are contained, these binder phase forming components have a low melting point, Therefore, during sintering, a liquid phase is formed to promote sintering, and after sintering, it exists as a glassy or crystalline substance at the grain boundaries of Sialon, making the ceramic sufficiently dense. To have higher strength. In this case, the content of the binder phase forming component is preferably more than 10% by volume to 20% by volume,
This is because if the content is less than 10% by volume, the desired high density cannot be achieved;
This is because the strength of the ceramics will decrease if the content exceeds the above. The findings shown in (a) and (b) above were obtained. Therefore, the present invention has been made based on the above knowledge, and includes one or two of the elements contained in the following M, Si, and oxides and nitrides of Al, as a binder phase forming component. More than seeds: more than 10% to 20% by volume,
and the rest consists of α-sialon, β-sialon and inevitable impurities, and the β-sialon has the composition formula: Si _6-z Al _z O _z N _8-z (O<z≦4.3). The α-sialon has the composition represented by the formula: Mx (Si, Al) ₁₂ (O, N) ₁₆ (where O<x≦2, M: Li, Na, Ca, Mg,
Y, one or more rare earth elements), and the α-sialon/β-sialon capacity ratio is more than 25/75.
It is characterized by sialon-based ceramics with excellent wear resistance in the range of 95/5. Furthermore, the ceramics of the present invention includes, as raw material powder, Si ₃ N ₄ powder + Al ₂ O ₃ powder + AlN powder, Si ₃ N ₄ powder + SiO ₂ powder + AlN powder, Si ₂ ON ₂ powder + AlN powder, or any of the above. Combined α and β−
Prepare a sialon-forming compound powder (preferably Si ₃ N ₄ with a high α phase content), an M oxide and nitride powder that can be dissolved in α-sialon and also form a binder phase, and Raw material powders are blended to a predetermined composition, in this case so that Al and N are greater than those calculated from the composition formula of β-Sialon, mixed, and then this mixed powder is heated at 1550 to 1800°C. It can be produced by hot pressing at a temperature within this range or by sintering a green compact molded from the mixed powder at the above temperature. Note that the above sintering may be performed under normal conditions, but in this case, the thickness of the surface-altered layer of the ceramic after sintering becomes thicker, so it is preferable to embed the green compact in the Si ₃ N ₄ powder. Sintering is preferred. In addition, sintering must be performed in an atmosphere containing N ₂ to suppress the decomposition of Si ₃ N ₄ during sintering, and in this case, a mixture of N ₂ and H ₂ or N ₂ and Ar is used. Although gas may be used, it is preferable to use an atmosphere containing only N ₂ . Further, the atmospheric pressure may be about 0.9 atm, but preferably 1 atm, and more preferably 1 atm or more, but in this case a special sintering furnace is required. Also, the sintering temperature is as above
1550-1800℃, preferably 1650-1750℃
A temperature within the range of . Furthermore, if the ceramics after sintering are subjected to hot isostatic pressure sintering as necessary, densification will proceed further. Next, the ceramics of the present invention will be specifically explained using examples. Example As raw material powder, Si ₃ N ₄ (α
Phase content: 90% by volume) powder and CaO powder, same
0.6 μm α-Al ₂ O ₃ powder and MgO powder, 1.5 μm
m AlN powder, Li ₂ O powder, Na ₂ O powder, and Y ₂ O ₃ powder, all with a diameter of 1.1 μm.
Er ₂ O ₃ powder was prepared, these raw material powders were blended into the composition shown in Table 1, mixed in a wet ball mill for 72 hours, dried, and then this mixed powder was molded into a graphite mold for hot pressing. Fill it with
In air, pressure: 200Kg/cm ² , sintering temperature:

【table】

[Table] (*marked: outside the scope of the present invention)
Ceramics 1 of the present invention was prepared by hot press sintering at 1700°C for 1 hour.
-10 and Comparative Ceramics 1 and 2 were produced, respectively. Note that Comparative Ceramics 1 and 2 both have compositions in which the content of one of the constituent components (those marked with * in Table 1) is outside the scope of the present invention. Regarding the resulting Ceramics 1 to 10 of the present invention and Comparative Ceramics 1 and 2, the composition was investigated by microscopic observation and X-ray diffraction, and the hardness (Rockwell hardness A scale) was measured. A cutting chip was cut according to the following conditions, and a cast iron high-speed cutting test was conducted under the following conditions: Work material: FC30 round bar, Cutting speed: 400 m/min, Depth of cut: 2.5 mm, Feed: 0.5 mm/rev., Cutting time: 5 min. Work material: SKD61 round bar (Rockwell hardness A scale: 60), Cutting speed: 100 m/min, Depth of cut: 0.5 mm, Feed: 0.20 mm/rev., Cutting time: 15 min. A cutting test was conducted on the loaded steel, and the flank wear width of the cutting edge was measured. These results are shown in Table 1. Table 1 also includes commercially available
Test results for Al ₂ O _3- based ceramics under the same conditions are also shown. From the results shown in Table 1, ceramics 1 to 10 of the present invention all exhibit high hardness and excellent wear resistance, whereas comparative ceramic 1, which does not contain α-sialon, has poor wear resistance. Comparative Ceramics 2, in which the content of binder phase-forming components is higher than the range of the present invention, and commercially available Al ₂ O ₃ -based Ceramics 1 and 2, both have poor toughness and cannot be cut satisfactorily. It was impossible to do so. As mentioned above, the ceramic of the present invention has high hardness and exhibits excellent wear resistance in practical use, so when used as a cutting tool or a wear-resistant tool, it will last for an extremely long time. It consistently demonstrates excellent performance.

Claims (1)

[Claims] 1. As a binder phase forming component, one or more of the elements included in the following M, Si, and oxides and nitrides of Al: more than 10% by volume to 20% by volume,
and the remainder consists of α-sialon, β-sialon and inevitable impurities, and the β-sialon has the composition formula: Si _6-z Al _z O _z N _8-z (0<z≦4.3). The α-sialon has the composition represented by the formula: Mx (Si, Al) ₁₂ (O, N) ₁₆ (where 0<x≦2, M: Li, Na, Ca, Mg,
Y, one or more rare earth elements), and the α-sialon/β-sialon capacity ratio is more than 25/75.
Sialon-based ceramics with excellent wear resistance characterized by a 95/5 range.