JPH0780708B2 - High strength aluminum oxide based sintered body and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a cutting tool material, an abrasion resistant tool material, a corrosion resistant material, a high temperature machine part material, a precision machine part material, and a decorative material including a watch side. TECHNICAL FIELD The present invention relates to a high-strength aluminum oxide-based sintered body suitable for, and a manufacturing method thereof.

(Prior Art) Generally, a sintered body containing aluminum oxide as a main component is used in various industrial fields because it is excellent in oxidation resistance and resistance to welding to a metal and is low in price. .
Among the sintered bodies containing aluminum oxide as a main component, aluminum oxide is added to SiO ₂ , MgO, NiO, MnO ₂ , ZrO ₂ , TiC, SiC, TiN,
Aluminum oxide-based sintered bodies obtained by adding Si ₃ N ₄ , TiB ₂ , ZrB _{2 and the} like are used as cutting tool materials, wear resistant tool materials or electronic materials. Further, a carbon-containing aluminum oxide-based sintered body obtained by mainly adding carbon to aluminum oxide is used as a refractory material such as a casting nozzle or an inner wall of an iron / steel making furnace. Of these,
Typical examples of the latter carbon-containing aluminum oxide-based sintered body are disclosed in JP-A-57-123860 and JP-A-58-9916.
There is publication No. 4.

(Problems to be solved by the invention) Among aluminum oxide-based sintered bodies, aluminum oxide has a
The Al ₂ O ₃ -MgO based sintered body formed by adding 1 to ₃ wt% of MgO is
MgO in the sintering step is a grain growth inhibiting effect of the Al ₂ O _3, and becomes dense sintered body by forming the spinel MgO-Al ₂ O ₃ to Al ₂ O ₃ grain boundary after sintering It is a thing. However, the grain growth suppression effect of MgO is not so remarkable, and Na ₂
There is a problem that the strength is too low because the effect is further reduced by a trace amount of impurities such as O and K ₂ O. Further, an aluminum oxide-based sintered body obtained by adding ZrO ₂ , TiC, TiB ₂ , SiC or Si ₃ N ₄ to aluminum oxide is Al ₂ O ₃
-It has higher strength compared to MgO-based sintered bodies and has been applied even in the area requiring impact resistance. However, while these aluminum oxide-based sintered bodies have high strength, they have a problem that they are difficult to sinter.

A carbon-containing aluminum oxide-based sintered body is disclosed in JP-A-57-123.
No. 860 discloses alumina aggregate 80-97 wt% and carbon 3-2.
Alumina-carbon refractory made by adding metallic silicon powder and metallic aluminum powder to a mixture containing 0 wt% so that the weight ratio of Si / Al is 0.1 to 2 in a total amount of 0.5 to 15 wt%. . Further, Japanese Patent Application Laid-Open No. 58-99164 discloses high alumina material 65-95.5 wt%, carbonaceous material 3-15 wt%, silicon carbide, silicon nitride, boron carbide and boron nitride. A plate refractory for sliding nozzles, which is composed of two or more kinds of 1 to 10 wt% and aluminum powder of 0.5 to 10 wt%. JP-A-57-123860 and JP-A-58-99
Although the 164 publication has excellent strength, corrosion resistance and spalling resistance as a refractory material, it has a porosity of 15 to 18%.
Therefore, there is a problem that the strength is only 1/20 to 1/30 as compared with the above-mentioned aluminum oxide-based sintered body.

The present invention solves the above-mentioned problems, and specifically, by enclosing the crystal particles of aluminum oxide with a trace amount of carbon, the grain growth of aluminum oxide is suppressed, and moreover, the adhesion with carbon is suppressed. It is an object of the present invention to provide an aluminum oxide-based sintered body having high hardness and excellent fracture resistance by mixing a dispersed phase having excellent properties, and a method for producing the same.

(Means for Solving Problems) The present inventors suppress the grain growth of aluminum oxide,
Moreover, when the additive that contributes to the improvement of wear resistance and fracture resistance without degrading various values such as hardness, strength and fracture toughness of the aluminum oxide based sintered body was examined, By adding a specific amount of carbon, especially a trace amount of carbon with good dispersibility, and making it continuously go around the aluminum oxide grain boundaries, the grain growth of aluminum oxide is remarkably suppressed, resulting in high hardness, high strength and wear resistance. It has been found that an aluminum oxide-based sintered body having excellent properties and fracture resistance can be obtained. The present invention has been completed based on this finding.

That is, the high-strength aluminum-based sintered body of the present invention includes silicon carbide, silicon nitride, aluminum nitride, partially stabilized zirconia, stabilized zirconia, periodic table 4a, 5a,
A hard phase containing 40 wt% or less of a dispersed phase of at least one kind of carbides, nitrides, oxides, borides, and mutual solid solutions of 6a group metals, 0.03 to 1 wt% of carbon, and the remaining aluminum oxide as a main component. And unavoidable impurities.

The dispersed phase in the high-strength aluminum oxide-based sintered body of the present invention is specifically, for example, α-SiC, β-SiC, γ-Si.
C, δ-SiC, α-Si ₃ N ₄ , β-Si ₃ N ₄ , AlN, Al (O, N) stabilizers MgO, Y ₂ O ₃ , CaO containing ZrO ₂ , ZrO ₂ containing of these monoclinic article traces containing tetragonal or tetragonal and cubic ZrO _2, TiC, which mixed-tetragonal were mainly of, ZrC, HfC, Tac, NbC , VC, W
C, Mo ₂ C, Cr ₃ C ₂ ,, TiN, ZrN, HfN, TaN, NbN, VN, CrN, TiO, Ti
O ₂ , HfO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , V ₂ O ₅ , Cr ₂ O ₃ , TiB ₂ , ZrB ₂ , H
fB ₂ , sialon, (W, Ti) C, Ti (C, N), Ti (C, O), Ti (N, O), Ti (C, N, O), (W, Ta, Ti) C And so on. These dispersed phases may be in the form of particles or whiskers. When the dispersed phase is granular, the average particle size is preferably 1 μm from the viewpoint of strength and fracture resistance, and when the dispersed phase is whisker-like, the average aspect ratio is determined from workability during production and fracture resistance.
Those of 10 to 50 are preferable. If this dispersed phase is contained in excess of 40 wt%, the hard phase becomes relatively small,
Since the effect of aluminum oxide, which is the main component of the hard phase, that is excellent in oxidation resistance and resistance to welding with metals and alloys is reduced, and the tendency of coarsening of the dispersed phase itself becomes remarkable, A decrease in the strength and fracture toughness of the knot occurs.
From this, the dispersed phase in the sintered body is determined to be 40 wt% or less.

Carbon in the high-strength aluminum oxide-based sintered body of the present invention, especially amorphous carbon, among them is said to be formed by heating the phenol resin to 1300 ~ 3000 ° C. glassy carbon, or high hardness and Carbon, which is equivalent to glassy carbon having characteristics such as high strength, is preferable because the sintered body has excellent strength, abrasion resistance, and fracture resistance. This carbon amount is 0.
If it is less than 03 wt%, the grain growth suppressing effect of the strengthened aluminum is low, and the strength and fracture resistance of the sintered body are reduced. On the other hand, if the amount of carbon exceeds 1 wt% and increases, the hardness and wear resistance of the sintered body decrease. For this reason, the amount of carbon is 0.
It is defined as 03 to 1 wt%. Especially, the amount of carbon is 0.5
When it is up to 1 wt%, it becomes a sintered body having a continuous structure of carbon, shows electrical conductivity, and has good machinability by electric discharge machining, so it is preferable as a sintered body for forming a complicated shape. It is a thing.

The hard phase in the high-strength aluminum oxide-based sintered body of the present invention is composed of α-Al ₂ O ₃ , β-Al ₂ O ₃ or a mixture thereof. In addition, MgO, CaO, NiO, Cr ₂ O ₃ , T
Oxides such as iO ₂ , MnO ₂ , Co ₃ O ₄ , and Y ₂ O ₃ are mainly composed of aluminum oxide in which solid solution or mixture of aluminum oxide is 5 wt% or less. It is desirable that this hard phase be as fine as possible. In particular, in order to improve the compactness, abrasion resistance and fracture resistance, it is preferable that the average particle diameter is 2.0 μm or less of aluminum oxide. Aluminum oxide having a thickness of μm or less is more preferable.

In order to produce the high-strength aluminum oxide-based sintered body of the present invention, it is necessary to attach importance to dispersion of carbon in aluminum oxide. For this reason, it is preferable to use, as a starting material, a composite powder obtained by coating the surface of aluminum oxide powder with carbon.

That is, the method for producing a high-strength aluminum oxide-based sintered body according to the present invention includes silicon carbide, silicon nitride, aluminum nitride, partially stabilized zirconia, stabilized zirconia, carbides of metals of groups 4a, 5a and 6a of the periodic table, Mixing at least one powder and / or whisker among nitrides, oxides, borides and mutual solid solutions thereof with a composite powder obtained by coating the surface of a powder containing aluminum oxide as a main component with carbon, and After molding, heat-sinter in vacuum or non-oxidizing gas to obtain silicon carbide, silicon nitride, aluminum nitride,
Partially stabilized zirconia, stabilized zirconia, Periodic table 4
Dispersed phase of at least one of carbides, nitrides, oxides, borides and their mutual solid solutions of a, 5a, 6a metals 40
The present invention is characterized in that the sintered body is composed of a hard phase containing aluminum oxide as a main component and inevitable impurities in an amount of not more than wt% and 0.03 to 3 wt%.

The starting materials for forming the dispersed phase in the method for producing a high-strength aluminum-based sintered body of the present invention are powder and / or
Alternatively, whiskers can be used. When powder is used as the starting material, fine powder of submicron having an average particle size of 2 μm or less, particularly dispersibility and easy sinterability is preferable. When whisker is used as the starting material, the average aspect ratio of the starting material is sintered. It is preferable to use one having an average aspect ratio in the body of 1.5 to 3 times.

In the method for producing a high-strength aluminum oxide-based sintered body of the present invention, a composite powder obtained by coating carbon on the surface of a powder containing aluminum oxide as a main component is α-Al ₂ O ₃ , β-A.
l ₂ O ₃ , γ-Al ₂ O ₃ , amorphous aluminum oxide, aluminum oxide composed of a mixture of two or more thereof, or MgO, CaO, NiO, Cr ₂ O ₃ , TiO _{2 on} these aluminum oxides. ， M
Oxides such as nO ₂ , Co ₃ O ₄ , and Y ₂ O ₃ were mixed with aluminum oxide in an amount of 5 wt% or less in solid state or mixed with each other. The coated composite powder can be used as a starting material. In particular, it is preferable to use a fine powder of aluminum oxide, which has a submicron or amorphous state and has an average particle diameter of 0.5 μm or less because it is easily sinterable. Further, the carbon coating method, after mixing and drying powder containing aluminum oxide as a main component in a solution prepared by dissolving an organic compound, for example, a phenol resin, a vinyl resin, etc. in a solvent,
The heat treatment method is preferable because the process is easy. Further, the control of the contained carbon amount can be performed mainly by the kind of the organic compound and its content.

The starting materials and composite powders for forming these dispersed phases are mixed by a conventional powder metallurgical method, and especially when the starting materials for forming the dispersed phase contain whiskers, pulverization is performed as much as possible. Suppressing and mixing by a method that mainly disperses and mixes whiskers to each other, for example, a method such as V-blender, and if necessary, adding a molding lubricant such as paraffin, polyvinyl alcohol, or polystyrene,
After granulation and sieving, the powder may be molded by a conventional powder metallurgy method such as embossing, extrusion and injection molding, and then heat-sintered in vacuum or in a non-oxidizing gas.

Sintering is performed in vacuum or in a non-oxidizing gas such as Ar or N ₂ under normal pressure or 200 to 500 kgf / cm ² under pressure of 1300 to 1800 ℃.
It may be held for 1 to 4 hours by heating. After sintering in this way, if necessary, pressure of 1000 atm or more, 1300 ~ 1
Hot isostatic treatment (HIP treatment) at a temperature of 600 ° C. is preferable from the viewpoint of densification of the sintered body and improvement of strength.

(Function) The high-strength aluminum oxide-based sintered body of the present invention has carbon having excellent dispersibility dispersed in such a state as to surround a hard phase containing aluminum oxide as a main component,
Mutual diffusion of crystal grains of aluminum oxide is prevented, and therefore, an action of suppressing grain growth of aluminum oxide is working. Further, the carbon having excellent dispersibility also acts to relieve anisotropy of aluminum oxide.

The dispersed phase in the sintered body prevents the carbons surrounding the hard phase from contacting each other, and promotes densification while causing minute surface diffusion between the dispersed phase and carbon. Is. Further, the dispersed phase serves to reduce the thickness of carbon existing at the grain boundary between the hard phase and the dispersed phase as much as possible to enhance the strength and the fracture resistance.

According to the method for producing a high-strength aluminum oxide-based sintered body of the present invention, since the composite powder in which the surface of the powder mainly containing aluminum oxide is coated with carbon is used as a starting material, the dispersibility of carbon is remarkably excellent. It has an action and also has an action of promoting sinter without inhibiting it.

(Example) Example 1 99 wt% Al ₂ O ₃ -1 wt% MgO was compounded with starting materials of commercially available Al ₂ O ₃ powder and MgO powder having an average particle size of 0.1 μm. The balls and distilled water were placed in an alumina pot and wet-mixed and ground. The slurry thus obtained was mixed with polovinylpyrrolidone dissolved in distilled water, and then dried in an alumina container while stirring to obtain a mixed powder. A graphite board was filled with this mixed powder, and the temperature was raised to 900 ° C. at a constant rate of 3 ° C./min in nitrogen to prepare a composite powder in which the surface of the Al ₂ O ₃ powder was coated with carbon. Three types of composite powders were prepared: a composite powder having a carbon content of 0.5 wt%, a composite powder having a carbon content of 1.0 wt%, and a composite powder having a carbon content of 4.0 wt%. Using these composite powders and commercially available powders of TiC, TaC, Ti (N, C) (TiN / TiC = 7/3) with an average particle size of 1 μm, and the Al ₂ O ₃ powder and MgO powder described above Formulated as in the table.

Each compounded powder shown in Table 1 was wet-mixed and pulverized again using an alumina ball, an alumina pot and methanol, and paraffin was added as a molding lubricant. Next, after molding these mixed powders into a predetermined shape at a pressure of 1 ton / cm ² , after sintering under the conditions described in Table 1,
Under argon atmosphere, 1500 atmosphere, 1450 ℃ for 30 minutes
HIP treated. The hardness, segregation force and fracture toughness of each of the thus obtained sintered bodies were investigated, and the results are shown in Table 2. Further, the average grain size of Al ₂ O ₃ crystals in each sintered body was examined by a scanning electron microscope, and the results are shown in Table 2. Further, using each sintered body of Table 2, a cutting test was performed under the following turning conditions and milling cutting conditions to compare wear resistance and fracture resistance,
The results are also shown in Table 2.

Turning test conditions Work material FC 35 (HB 230) Chip shape SNGN 120804 Cutting speed 300 m / min Feed rate 0.2 mm / rev Depth of cut 1.5 mm Cutting time 20 min Dry continuous cutting Milling cutting test conditions Work material FCD 60 (HB 330) Insert shape SNGN 120804 Cutting speed 200 m / min Depth of cut 1.5 mm Life judgment 0.18 mm / Dry intermittent cutting was performed from the feed speed of the blade, the feed was increased every 200 mm cutting, and the feed speed was shown when the insert was broken. .

Example 2 A sintered body was obtained in the same manner as in Example 1 except that the starting raw material powders used in Example 1 were blended as shown in Table 3 and the sintering conditions also shown in Table 3 were combined. . Each sintered body thus obtained was examined in the same manner as in Example 1, and various characteristics and performance results thereof are shown in Table 4.

Example 3 Each powder used in Example 1 and 3 mol% Y ₂ O having an average particle size of 0.1 μm
_{3 A} solid solution ZrO ₂ powder was used as a starting material, compounded as shown in Table 5, and a sintered body was obtained in the same manner as in Example 1 except for the sintering conditions also shown in Table 5. Each sintered body thus obtained was used in Example 1.
The characteristics and performance results are shown in Table 6.

Example 4 Using each powder used in Example 1 and SiC whiskers having an average particle size of 1 μm as starting materials, compounded as shown in Table 7, and sintered by hot pressing at a pressure of 500 kg / cm ² described in Table 7 together. Average aspect ratio of SiC whiskers by controlling conditions and crushing 1
Mixing was completed at time 0, and a sintered body was obtained in the same manner as in Example 1 except that HIP was not treated. Each sintered body thus obtained was processed in the same manner as in Example 1, and various characteristics and performance results are shown in Table 8.

Example 5 A commercially available Al ₂ O ₃ powder having an average particle size of 0.2 μm and 2.5 μm was prepared in the same manner as in Example 1 to prepare a slurry. Resol-type phenol resin dissolved in methanol was mixed with this slurry in an amount of 2 wt% with respect to the Al ₂ O ₃ powder, and dried in an alumina container with stirring to obtain a mixed powder. This mixed powder was filled in a graphite boat, heated to 700 ° C. at a constant rate of 5 ° C./min in Ar gas, and then kept at 700 ° C. for 30 minutes.
A composite powder was prepared in which the surface of the Al ₂ O ₃ powder was coated with carbon. The residual carbon content is 0.68wt for 0.2μm Al ₂ O ₃ raw material powder.
% Or 0.53 wt% in the case of 2.5 μm Al ₂ O ₃ raw material powder. Using these composite powders and a commercially available TiC powder having an average particle size of 1 μm, the compounded powders shown in Table 9 were wet mixed and pulverized in the same manner as in Example 1, and the results are shown in Table 9 together.
Sintering conditions and HIP by hot pressing with a pressure of 0 kg / cm ²
A sintered body was obtained in the same manner as in Example 1 except that it was not treated. Each sintered body thus obtained was examined in the same manner as in Example 1, and various characteristics and performance results are shown in Table 10.

(Effects of the Invention) From the above results, the high-strength aluminum oxide-based sintered body of the present invention has high hardness and excellent wear resistance, and also has a fracture resistance of 1 to 3 ranks during intermittent cutting accompanied by impact. Since it is an improved high toughness ceramic sintered body, it is a remarkable improvement in reliability as a cutting tool. Further, since it is a fine-grained alumina-based ceramics sintered body, it has excellent blade sharpness when processed into a sharp edge and excellent wear resistance, and therefore exhibits excellent properties when used as a wear resistant tool. Furthermore, since it is mainly made of alumina, it has excellent oxidation resistance and corrosion resistance, and for this reason it can be used for mechanical seals, valves, valve seats, balls, etc., and because it is a material with a blackish color tone, it is an exterior part for watches, fishing gear. It is an industrially useful material that can be applied to decorative parts such as parts and golf club heads.

Claims (6)

[Claims] Claims: 1. Silicon carbide, silicon nitride, aluminum nitride, partially stabilized zirconia, stabilized zirconia, carbides, nitrides, oxides, borides of metals of groups 4a, 5a and 6a of the Periodic Table and mutual solid solutions thereof. At least one dispersed phase in
A high-strength aluminum oxide-based sintered body comprising 40 wt% or less, 0.03 to 1 wt% carbon, and a hard phase containing aluminum oxide as a main component and unavoidable impurities. 2. The high-strength aluminum oxide-based sintered body according to claim 1, wherein the carbon is amorphous carbon. 3. The high-strength aluminum oxide-based sintered body according to claim 1 or 2, wherein the hard phase is made of aluminum oxide having an average particle size of 2.0 μm or less. 4. Silicon carbide, silicon nitride, aluminum nitride, partially stabilized zirconia, stabilized zirconia, carbides, nitrides, oxides, borides of metals of groups 4a, 5a and 6a of the Periodic Table and mutual solid solutions thereof. At least one powder and / or whisker in the above and a composite powder obtained by coating the surface of the powder containing aluminum oxide as a main component with carbon are mixed and molded, and then heated and sintered in a vacuum or a non-oxidizing gas. Then, silicon carbide, silicon nitride, aluminum nitride, partially stabilized zirconia, stabilized zirconia, periodic table 4a, 5a,
A hard phase containing 40 wt% or less of a dispersed phase of at least one kind of carbides, nitrides, oxides, borides, and mutual solid solutions of 6a group metals, 0.03 to 1 wt% of carbon, and the remaining aluminum oxide as a main component. A method for producing a high-strength aluminum oxide-based sintered body, which comprises: 5. The method for producing a high-strength aluminum oxide-based sintered body according to claim 4, wherein the carbon is amorphous carbon. 6. The aluminum oxide has an average particle size of 2.0.
The method for producing a high-strength aluminum oxide-based sintered body according to claim 4 or 5, wherein the aluminum oxide-based sintered body has a thickness of at most μm.