JPH0377147B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing a high-density, high-toughness ceramic material, and in particular to a method for producing A ₂ O ₃ -TiC-based high-toughness ceramic material useful as a material for cutting tools. It is. [Prior Art] Among tool materials, the following material properties are required for cutting tools that are subjected to severe force and heat, particularly at the cutting edge. 1 High temperature hardness. 2. Must have toughness, especially toughness at high temperatures. 3. It is chemically stable and does not react with the material to be cut at the cutting edge. Alumina tools used as cutting tool materials are satisfactory in 1 and 3 of these required properties, but have a problem with 2. A ₂ O ₃ -TiC ceramic was developed to overcome this limitation. This type of ceramic is A
This is an epoch-making improvement in ₂ O ₃ based materials and a typical success example of composite ceramics. However, since it is a composite of oxide and carbide, it is difficult to make it dense by simply applying heat. Therefore, A ₂ O ₃ particles and dispersed particles (TiC)
It is necessary to devise measures to suppress the gas generation between the parts as much as possible, but industrial manufacturing techniques include the application of hot pressing, which applies mechanical force in addition to heat, and furthermore, the application of even and large force from all directions. The application of hot isostatic pressing is used to produce products with stable and high performance. Such A ₂ O ₃ −
TiC-based ceramics have excellent wear resistance and low affinity with iron, so they are widely used in precision finishing and high-speed cutting of cast iron. [Problem that the problem is trying to solve] Cutting speeds are becoming extremely fast in various industries, such as the automobile and aircraft industries, to improve productivity, and on the other hand, the development of machine tools that can withstand such high-speed cutting. There is also. Furthermore, as production sites become increasingly unmanned, it has become necessary to improve the reliability of cutting tools, especially ceramic tools. In order to improve high-speed cutting and reliability of cutting tools, it is necessary to further improve the performance of current A ₂ O ₃ --TiC ceramics, especially in terms of toughness. As a means of improving this toughness, TiC grains are
Strengthening of the interface between ₂ O ₃ grains or between TiC grains and A ₂ O ₃ grains is considered, and in the past TiO ₂ (Special Publication No. 51-569)
Attempts have been made to add Ti (Japanese Patent Publication No. 50-20963 and Japanese Patent Publication No. 50-39445), but sufficient results have not been obtained. The present invention was made in order to solve the above problems, and an object of the present invention is to provide a method for manufacturing A ₂ O ₃ -TiC ceramic having greater toughness. [Structure of the Invention] The present invention comprises 20 to 50% by weight of titanium carbide represented by the general formula TiCx (where x is 0.65 to 0.93), MgO, CaO,
0.1 to 2% by weight of one or more sintering aids selected from SiO ₂ , ZrO ₂ , NiO and rare earth oxides
and 48 to 79.9% by weight of A ₂ O ₃ is molded and then sintered by hot pressing to have a theoretical density of 99% or more. do. In the present invention, TiCx (x is 0.65 to 0.93)
is required to be used in an amount of 20 to 50% by weight. The above TiCx is a non-stoichiometric titanium carbide containing excess Ti, and has an incomplete and unstable crystal structure compared to the stoichiometric titanium carbide represented by TiC. Therefore, sintering reactions such as solid phase reactions become easier, and the interfaces between the A ₂ O ₃ grains, the TiCx grains, and between the TiCx grains are strengthened compared to the interfaces between the A ₂ O ₃ grains, the TiC grains, and between the TiC grains. In addition, the bonding form between TiCx atoms is such that the covalent bond has metallic bonding characteristics, improving toughness. If x in TiCx is less than 0.65,
The performance of the sintered body, especially the wear resistance, decreased, and x was 0.93.
If it becomes larger, the non-stoichiometric effect in TiCx becomes weaker and sufficient toughness cannot be obtained. It is necessary to use 20 to 50% by weight of the above TiCx, but if TiCx is less than 20% by weight, TiCx
If the amount exceeds 50% by weight, the sinterability will deteriorate and sufficient toughness will not be obtained. Additionally, one or more sintering aids such as
It is necessary to use 0.1 to 2% by weight of MgO, CaO, etc. The sintering aid forms a compound with A ₂ O ₃ , which assists the sintering of the ceramic and improves the sinterability. Furthermore, grain growth of A ₂ O ₃ during sintering can be suppressed by adding a sintering aid. In the present invention, sintering aids include MgO,
CaO, SiO ₂ , ZrO ₂ , NiO, Y ₂ O ₃ , Dy ₂ O ₃ , Er ₂
Ordinary A ₂ O ₃ such as rare earth oxides such as O _{3 and Ho 2 O 3}
Refers to those used for sintering A ₂ O _{3 -based} ceramics such as A ₂ O ₃ -TiC series, A ₂ O ₃ -ZrO ₂ series, etc. In the present invention, the sintering aid is used in an amount of 0.1% by weight to 2% by weight.
If the amount is less than 0.1% by weight, the above-mentioned effect will not be sufficiently exhibited, whereas if it is more than 2% by weight, a large amount of the above-mentioned compound will deteriorate the high-temperature properties of the ceramic material. The ceramic obtained by the method of the present invention as described above has excellent wear resistance and toughness.
The reason is that the adhesive strength between A ₂ O ₃ and TiCx is high.
And it is presumed that this is because the crystal grains of A ₂ O ₃ are fine. [Example] An example of the present invention will be described. α-A ₂ O ₃ with a purity of 99.9% and an average particle size of 0.4 μm, 1st
TiCx adjusted to the contents shown in the table and sintering aids were variously blended as shown in Table 2, wet mixed in a ball mill for 40 hours, and then dried to obtain a mixed powder. This mixed powder was sintered by the hot press method in a graphite mold under the conditions of a pressure of 200 kg/cm ² , a time of 15 minutes, and a temperature shown in Table 2. The obtained sintered body is 13×13×5mm
Then, using a diamond grindstone,
Finished in the shape of SNGN432 (JIS). The chamfer was set to 0.1 mm x 25°. When a cutting test was conducted on this material under the following conditions, the second
The results shown in the table were obtained. Cutting test conditions I Work material: FC20 (HB190~220) Cutting conditions: Cutting speed (V) = 800 m/min, depth of cut (t) = 0.5 mm, feed rate (f) = 0.25 mm/rev, life judgment: Measure the wear width V _B (mm) after cutting the outer circumference of 120 mmφ x I5 mm 100 times Work material: SKD11 (HRC62) Cutting conditions: Cutting speed (V) = 150 m/min, depth of cut (t) = 0.5 mm , Feed rate (f) = 0.17mm/rev Life judgment: Measure the wear width V _B (mm) after cutting a 120φmm bar for 15 minutes.

【table】

【table】

[Table] From the results shown in Table 2, it was found that in the following cases (1) to (6), the wear width of the ceramic tool increases, and in some cases, the ceramic tool breaks. (1) When TiCx is blended in an amount greater than 50% by weight as in No.17. (2) When less than 20% by weight of TiCx is blended as in No.18. (3) When the value of x in TiCx exceeds 0.93 as in No.19. (4) When the value of x in TiCx is smaller than 0.65 as in No.20. (5) When the sintering aid is less than 0.1% by weight like No.21. (6) When the sintering aid is more than 2% by weight as in No.22. It has been found that in order to obtain highly tough ceramics from these, it is absolutely necessary to set the value of x in TiCx, the amount of TiCx, and the amount of sintering aid to be specified as in the present invention. [Effects of the Invention] By using the ceramic manufacturing method of the present invention, A ₂ O ₃ -TiC ceramics with high toughness can be manufactured, and the manufactured ceramics can be used for cast iron, steel, high nickel, aluminum, and titanium. It is useful as a non-metallic cutting tool, as well as for mechanical parts that are subject to intense vibration or high heat.

Claims (1)

[Claims] 1. 20 to 50% by weight of titanium carbide represented by the general formula TiCx (where x is 0.65 to 0.93), and 1 selected from MgO, CaO, SiO ₂ , ZrO ₂ , NiO, and rare earth oxides. species or two or more sintering aids
0.1 to 2% by weight of A ₂ O _{3 and 48 to 79.9% by weight of A 2 O 3} A high toughness ceramic characterized in that it is molded and then sintered by a hot press method to have a theoretical density of 99% or more. manufacturing method.