JPH0116793B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to sialon-based ceramics that exhibit outstanding wear resistance when used as cutting tools, wear-resistant tools, etc., and also have particularly good high-temperature strength and thermal shock resistance. . [Prior art and its problems] 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 tools. Since ₄ is a compound with strong covalent bonding properties, it has poor sintering properties, and therefore hot pressing is often used to manufacture it, and in this case it is difficult to manufacture products with complex shapes.
This results in low productivity. _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 containing β-sialon as a main component as cutting tools and wear-resistant tools, but although these sialon-based ceramics have high toughness, they have a hardness of 92 on the Rockwell A scale. Currently, the wear resistance is not as high as desired, so it does not exhibit the desired wear resistance. [Prior Art] Therefore, the applicant first proposed the following compositional formula: Si ₆ −zAlzOzN ₈ −z (where O<Z≦
β-sialon expressed by 4.3) and the composition formula:
Mx (Si, Al) ₁₂ (O, N) ₁₆ (O<x≦2,
M: α- represented by one or more of Li, Na, Ca, Mg, Y, and rare earth elements)
sialon as a main component, and one or more of carbides, nitrides, carbonitrides, and carbonitrides of Ti, Zr, and Hf as dispersed phase forming components: 1 to 40 Volume %, elements included in the above M as binder phase forming components, metal elements constituting the above dispersed phase, Si, and
One or two of Al oxides and nitrides
Sialon-based ceramics with excellent wear resistance, characterized by containing: 1 to 20% by volume, and having a volume ratio of α-sialon/β-sialon in the range of 25/75 to 95/5. proposed. In this proposed sialon-based ceramic, in addition to β-sialon, part of the Si in the α-Si ₃ N ₄ lattice is replaced with Al and part of the N is replaced with O, and in addition, Li, Na, Compounds with a structure in which one or more of Ca, Mg, Y, and rare earth elements (hereinafter these elements are collectively referred to as M) penetrate and form a solid solution, that is, the composition formula: Mx (Si , Al) ₁₂ (O, N)) ₁₆ (O<x≦2)
Since α-sialon expressed as coexists,
The hardness of the obtained ceramics is improved, and furthermore, in the ceramics in which α-sialon and β-sialon coexist, it is added as a dispersed phase forming component.
Since one or more of carbides such as Ti, nitrides, carbonitrides, and carbonitrides are contained, the grain growth of SiAlON during sintering is suppressed, and the sintering As a result, the hardness of the obtained ceramics is further improved, and the wear resistance is further improved. [Problems and findings to be solved by the invention] The present inventors conducted further test and research on the previously proposed sialon-based ceramics, and found that carbides and nitrides of Ti, which is the raw material powder, , carbonitride, and carbonitride (hereinafter, these compounds are collectively referred to as S ₁ ) depending on the particle size and blending ratio of the powder.
It was found that the high-temperature strength and thermal shock resistance of the resulting ceramics are greatly affected. Therefore, as a result of further investigation, we found that when the particle size of the raw material _S1 powder is fine and its blending ratio is not large, the resulting ceramics have particularly excellent high-temperature strength and thermal shock resistance. From microscopic observation of the structure of the obtained ceramics, it was found that the effect is that when the particle size of the raw material powder _S1 powder is fine,
As a result, the particle size of S ₁ as a dispersed phase forming component in the obtained ceramics becomes fine, and if the blending ratio of S ₁ is not large, the content of S ₁ as a dispersed phase forming component in the obtained ceramics becomes fine. Since the amount is not large, it is possible to take advantage of Sialon's inherent characteristic of having a small coefficient of thermal expansion.Thus, these two properties combine to create a ceramic with particularly excellent high-temperature strength and thermal shock resistance. When the particle size of S ₁ as a dispersed phase forming component in ceramics is below a specific particle size, and the content of S ₁ is below a specific content, particularly high temperature strength and thermal shock resistance can be achieved. It was discovered that it can be made into excellent ceramics. [Matters Essential to the Structure of the Invention] The present invention is a sialon-based ceramic having excellent wear resistance, high-temperature strength, and thermal shock resistance, which was invented based on the above knowledge, and has a composition formula: Si _6-z Al _z O _z N _8-z (However, O＜Z≦4.3)
β-Sialon represented by and compositional formula: Mx
(Si, Al) ₁₂ (O, N) ₁₆ (However, O<X≦2, M:
Li, Na, Ca, Mg, Y, one of rare earth elements
The main component is α-sialon represented by a species or two or more species), and in addition, an average particle size of 0.05 to 0.5μ as a dispersed phase forming component.
m, one or more of Ti carbides, nitrides, carbonitrides, and carbonitrides: 1 to 20
% by volume, and one or more of the elements contained in M above as binder phase forming components, oxides and oxynitrides of Ti, Si, and Al: 1 to 20% by volume; It is characterized in that the α-sialon/β-sialon capacity ratio is in the range of 25/75 to 95/5. [Constitutional Requirements of the Invention and Reasons for Limitation] The structure of the sialon-based ceramic of the present invention will be explained in detail below. (i) Particle size and content of Si The average particle size of _S1 in ceramics is 0.05 to 0.5μ
m, and the content needs to be 1 to 20% by volume. This is because the coefficient of thermal expansion of Sialon is 3.4 ~
3.8×10 ^-6 /℃, while that of S ₁ is 8
It is large at ~10×10 ^-6 /℃. Therefore, as the content of S ₁ increases, the overall coefficient of thermal expansion increases, and the material becomes weaker against thermal changes and thermal shock. In other words, the content of S ₁ mentioned above is
If it exceeds 20% by volume, the high-temperature strength decreases significantly, and furthermore, the strength decreases too much when subjected to thermal shock. Conversely, if it exceeds 1% by volume, the grain growth suppressing effect on sialon is insufficient and the sialon grains deteriorate. The content is determined to be 1 to 20% by volume because the content becomes rough and causes a decrease in hardness and strength. The average particle size of S ₁ in ceramics is actually
It is difficult to make it less than 0.05μm, and conversely,
If the average particle diameter exceeds 0.5 μm, the strength will be significantly lowered when subjected to thermal shock, and the high-temperature strength will also be lowered, so it was set at 0.05 μm to 0.5 μm. The average particle size of S ₁ in the ceramics is preferably 0.3 μm or less. (ii) Effect and content of binder phase-forming component One or more of the elements included in M above, oxides and oxynitrides of Ti, Si, and Al are contained as a binder phase-forming component. These binder phase-forming components have a low melting point and therefore form a liquid phase during sintering to promote sintering, and after sintering, they form a glassy or crystalline phase at the grain boundaries of Sialon. As a result, ceramics become sufficiently dense and have higher strength. In this case, the content of the binder phase forming component is:
If the content is less than 1% by volume, the desired high density cannot be achieved, while if it exceeds 20% by volume, the strength of the ceramic will decrease. This is because they become more likely to do so. (iii) Capacity ratio of α-sialon/β-sialon The ratio of α-sialon and β-sialon (α/β) needs to be 25/75 to 95/5 in terms of capacity ratio, which is This is based on the reason that if the proportion of α-SiAlON is less than 25% by volume, the desired effect of improving hardness cannot be obtained, whereas if the proportion exceeds 95% by volume, sinterability will decrease. . [Additional Matters to the Invention] The ceramics of the present invention includes, as raw material powders, 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, α and β− in combination with any of the above
Sialon-forming compound powder, one or more M oxide and oxynitride powders that can be solid dissolved in α-sialon and also form a binder phase, Si powder that forms a dispersed phase, and As a bonded phase forming component if necessary,
One of Ti oxide powder and oxynitride powder
A seed or two types are prepared, and these raw material powders are blended to a predetermined composition, in this case, the amount of Al and N is greater than that calculated from the composition formula of β-Sialon, and mixed. When producing the mixed powder by hot pressing at a temperature within the range of 1550 to 1800°C or by sintering a green compact molded from the mixed powder at the above temperature, the powder of _S1 above As a raw material powder with an average particle size of 0.1 to 1.1 μm, depending on the conditions of the subsequent mixing step,
It can be produced by using a blending ratio of approximately 1 to 20% by volume. Examples of the powder (raw material powder) having an average particle size S ₁ as described above include the following. In other words, it is made by grinding commercially available _S1 powder using a ball mill using sialon balls or alumina balls (in this case, foreign components may be mixed in from the balls), or made by plasma arc method, CVD method, etc. Ivy ultrafine powder (e.g. Si ₃ N ₄ which is a raw material for forming Sialon)
and an ultra-fine powder mixture made by simultaneously using an electric arc in the same furnace with Ti nitride). In addition, by using composite metal nitrides, carbonitrides, and carbonitride powders of Ti and other metals as raw materials and decomposing them during sintering, Ti nitrides, carbonitrides, and carbonitrides can be produced in ceramics. There is also a method of producing a fine powder of oxide and thus containing this fine powder. For example, there is a method in which Ti ₂ AlN is used as a compounding raw material and TiN is precipitated during sintering. In some cases, it is preferable to perform sintering at high nitrogen pressure by autoclaving or by hot isostatic pressing sintering to prevent formation of Ti ₂ N and the like. [Example] Hereinafter, the configuration and effects of the present invention will be described in detail using Examples as well as Comparative Examples. Examples and Comparative Examples As raw material powder, Si ₃ N ₄ powder with an average particle size of 0.8 μm,
0.6 μm α-Al ₂ O ₃ powder and MgO powder,
1.5 μm AlN powder, 1.0 μm Y ₂ O ₃ powder and
LiO ₂ powder, 0.5μm TiC powder and TiN powder,
1.1μm TiCN powder, 0.4μm TiCNO powder,
2.5μm Ti ₂ AlN powder, 3.5μm for comparison
Prepare TiN powder, mix these raw material powders to the composition shown in Table 1, and use a wet ball mill.
After mixing and pulverizing for 72 hours, it was dried and press-molded at a pressure of 1.5 t/cm ² to form a compact, and the obtained compact was sintered at 1700°C for 2 hours in a nitrogen atmosphere at normal pressure. , further in nitrogen at 1700℃ and pressure 1500Kg/ ^cm2 .
Ceramics 1 to 6 of the present invention and comparative ceramics 1 to 2 were prepared by sintering under hot isostatic pressure for a period of time.
was manufactured. In Comparative Ceramics 1 and 2, the particle size or component content (marked with * in Table 1) of S ₁ as a dispersed phase forming component is outside the scope of the present invention. Regarding the resulting Ceramics 1 to 6 of the present invention and Comparative Ceramics 1 to 2, the composition was investigated by microscopic observation and X-ray diffraction, and the hardness (Rockwell hardness A scale) was measured. A transverse rupture strength test piece of × 4 mm × 40 mm (distance between spans: 30 mm) was cut out and heated to 1000℃.
The high temperature transverse rupture strength was measured and the results are shown in Table 1. Furthermore, cutting chips conforming to SNG432 were cut from Ceramics 1 to 6 of the present invention and Comparative Ceramics 1 to 2. Work material: FCD45 (Brinell hardness: 290) Cutting speed: 300 m/min Feed per tooth: 0.28 mm /Blade A wet milling test was conducted under the conditions of depth of cut: 2 mm and cutting time: 15 minutes, and the flank wear width of the cutting edge, chipping, cracking, etc. were measured or observed. The results are also shown in Table 1. From the results shown in Table 1, ceramics 1 to 6 of the present invention all have high hardness and a hardness of about 110 kg/cm ²

〔Effect of the invention〕

As can be seen from the examples, the sialon-based ceramics of the present invention have high hardness, high wear resistance, and particularly excellent high temperature strength and thermal shock resistance, so they can be used as cutting tools as described in the examples. It is also a useful material that can be used as a wear-resistant tool.

Claims (1)

[Claims] 1. Compositional formula: Si _6-z Al _z O _z N _8-z (where O<Z≦
β-sialon expressed by 4.3) and the composition formula:
M _x (Si, Al) ₁₂ (O, N) ₁₆ (O<X≦2,
M: α- represented by one or more of Li, Na, Ca, Mg, Y, and rare earth elements)
Sialon is the main component, and in addition, as a dispersed phase forming component, the average particle size is 0.05 to 0.5μ.
m, one or more of Ti carbides, nitrides, carbonitrides, and carbonitrides: 1 to 20
% by volume, and one or more of the elements contained in M above as binder phase forming components, oxides and oxynitrides of Ti, Si, and Al: 1 to 20% by volume; A sialon-based ceramic having excellent wear resistance, high-temperature strength, and thermal shock resistance, characterized in that the α-sialon/β-sialon capacity ratio is in the range of 25/75 to 95/5.