JPH0122223B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing an aluminum oxide (Al ₂ O ₃ )-titanium carbide (TiC) ceramic sintered body having improved sinterability and excellent toughness. Ceramic sintered bodies have high hardness at room temperature,
In addition, it exhibits little hardness loss even at high temperatures and has high mechanical strength, making it an important material for sliding members that require wear resistance or for high-speed cutting tools. Hot press method and hot isostatic pressure sintering (hereinafter referred to as
The law (written as HIP) is considered to be effective. First of all, the HIP method has already reached the stage of practical application, but in order to apply this HIP method, it is necessary to prepare the ceramic powder compact into a pre-sintered compact with a theoretical density of 94% or more. this kind of
In the manufacturing process of Al ₂ O ₃ -TiC ceramic sintered bodies, one or more of MgO, NiO and Cr ₂ O ₃ is added as a means to improve the sintered bodies and suppress the growth of crystal grains. Measures have been taken to add approximately 1.5% by weight or less, but even with such measures, the sintering temperature during the above-mentioned preliminary sintering must be kept at 1850 to 1900°C.
If the density is not increased to a certain level, a pre-sintered body with the desired theoretical density cannot be obtained. Therefore, like this Al ₂ O ₃
-As TiC-based ceramics are exposed to high temperatures, mechanical strength decreases due to growth of Al ₂ O ₃ and TiC crystal particles despite the addition of the above-mentioned grain growth inhibitors. However, since it requires high temperatures, it has poor workability and also poses problems in terms of energy conservation. Next, in the hot press method, Al ₂ O ₃ −TiC
The raw material powder of the system is hot-press sintered at 1,600 to 1,800℃, and because the sintering temperature must be kept relatively high, the grain suppressor mentioned above is added. Nevertheless,
A considerable amount of growth of Al ₂ O ₃ -TiC crystal grains was observed, and there were still problems to be improved in terms of toughness. The present invention relates to a method for manufacturing a ceramic sintered body that solves the above-mentioned problems, and its gist consists of 15 to 60% by weight of titanium carbide, the balance being 100 parts by weight of aluminum oxide, and 0.05 to 0.05 to yttrium oxide. An element body formed from raw material powder having a composition of 2.00 parts by weight is pre-sintered in a reducing gas or inert gas atmosphere so that the theoretical density becomes 94% or more, and then the pre-sintered body is A method for producing a ceramic sintered body characterized by hot isostatic pressure sintering, and 15 to 60 weight percent of titanium carbide, the balance being 100 parts by weight of aluminum oxide, and 0.05 to 2.00 weight of yttrium oxide. This method of manufacturing a ceramic sintered body is characterized by hot-press sintering a raw material powder consisting of: The reason for using a reducing gas or inert gas (not including nitrogen gas) atmosphere during preliminary sintering in the HIP method described above is that an oxidizing atmosphere is not preferable because TiC will oxidize and become TiO ₂ . Also, under vacuum conditions, Al ₂ O ₃ decomposes and evaporates from about 1450°C, making it impossible to obtain a dense sintered body. Further, in a nitrogen gas atmosphere, the nitrogen reacts with the constituent components of the ceramic sintered body of the present invention, changing the composition of the final product, which is not preferable. In the method of the present invention, known grain growth inhibitors for aluminum oxide sintered bodies such as Ni, Mo, Cr,
It is more preferable to use one or more of oxides such as Co, Mg, Fe, and Mn in combination because the resulting sintered body will have finer crystals, resulting in greater toughness. The amount added is based on the total amount.
The optimum amount is 0.1-1.0 parts by weight. The experiments that led to the development of the present invention will be described below. <Experiment> (a) Experimental method and results α-Al ₂ O ₃ with a purity of 99.9% and an average particle size of 0.6μ,
TiC, _Y2O3 with a purity of 99% and an average particle size of _1μ ,
Various blends of TiC 10-70% by weight and Y ₂ O ₃ 0.025-2.500% by weight were wet mixed and pulverized for 20 hours using a ball mill mixer, then wax was added and granulated to produce 1.3 ton/cm. After sintering, mold the chip into a cutting tool chip body with dimensions of 13.0 square and 5.0 mm thick at a pressure of ² . In this case, it was known from experience that the pressure during compression molding at room temperature should be 0.5 ton/cm ² or more, so the compression molding was carried out under these conditions. The element body compressed at room temperature is pre-sintered in an argon gas atmosphere furnace at a temperature in the range of 1650°C to 1950°C and held for 1 hour so that the density of the pre-sintered body becomes 94% or more of the theoretical density. I went there.
The relationship _between the temperature _and the blending ratio of TiC and Y ₂ O ₃ in this case is shown in the graph in Figure 1-1.
Figure 2 shows an electron micrograph of the structure containing 0.5 parts by weight of Y ₂ O ₃ , and for comparison.
70Al ₂ O ₃ -30TiC (contains no Y ₂ O ₃ ) is pre-sintered (at a temperature of approx.
Fig. 3 shows an electron micrograph of the structure of the product (which required a temperature of 1900°C). Also, the results shown in Figure 1-1 are the same as those obtained when MgO, which is an example of a grain growth inhibitor, is used as a blended raw material.
Figure 1-2 shows the change in pre-sintering temperature when 0.25 parts by weight is added. Next, the pre-sintered body with a theoretical density of 94% to 95% obtained in this way is placed in a HIP consisting of a high-pressure container containing a Mo heating element.
Put into the furnace, 1400℃×1hr, high pressure of 1000Kg/ ^cm2
A final sintered body was obtained by applying isostatic pressure to the pre-sintered part of the bite chip under Ar gas pressure. Next, after grinding the various final sintered bodies using a diamond grindstone, the hardness (Rockwell A scale) of the various sintered bodies was measured. The results are shown graphically in FIG. Furthermore, an electron micrograph of the structure of the final sintered body after HIP is shown in FIG. In this sample, Y ₂ O ₃ was added to 100 parts by weight of (70Al ₂ O ₃ −30TiC).
0.5 part by weight was added. In addition, for comparison, a composition of 70Al ₂ O ₃ −30TiC (which does not contain any Y ₂ O ₃ ) has a theoretical density.
Figure 6 shows an electron micrograph of the structure of the product which was pre-sintered to 94% or higher and then subjected to HIP treatment. Similarly, 0.5 parts by weight of Y ₂ O ₃ was added to 100 parts by weight of (70Al ₂ O ₃ -30TiC), and
The X-ray diffraction patterns of 70Al ₂ O ₃ -30TiC (which does not contain any Y ₂ O ₃ ) are shown in FIGS. 7 and 8, respectively. In addition, in order to find the effective conditions for HIP sintering, a material with a density of 94% to 95% of theoretical density (70Al ₂ O ₃ −
A pre-sintered body containing 0.5 parts by weight of Y ₂ O ₃ per 100 parts by weight of 30TiC was placed in a HIP furnace at 1300°C and 1350°C.
℃, 1375℃, 1400℃, 1435℃, 1470℃, 1500
350Kg/cm ² , 400 at each temperature of ℃, 1600℃, 1700℃
High pressure of Kg/cm ² , 1000Kg/cm ² and 2000Kg/cm ²
Maintained under Ar gas pressure for 1 hour, then depressurized.
The furnace was cooled and the changes in theoretical density of the final sintered body under each HIP condition were determined. The results are shown graphically in FIG. Next, various blended pre-sintered bodies having a density of 94 to 95% of the theoretical density were placed in a HIP furnace, and
Sintered under high-pressure Ar gas pressure of 1000Kg/ ^cm2 at ℃×1hr to produce a final sintered body with a density of 99% or more relative to the theoretical density of the final sintered body into a cutting tool shape.
SNGN432 was processed into thread surface dimensions of 0.1 x 30°, each was subjected to a cutting test, and the performance was evaluated. The test conditions at that time were as follows. That is, <Continuous cutting test> Cutting material: High hardness material SNCM-8 (hardness Hs85) Cutting conditions: V x d x f = 50 m/min x 0.5 mm x 0.2 mm/rev Life judgment: Flank wear width 0.3 mm The results of this continuous cutting test are shown in Figures 10 and 11.
Shown in the graph of Figure. <Fraction resistance cutting test> Work material: Cast iron FC25 Cutting conditions: V x d = 245 m/min x 1.5 mm Life judgment: Milling was performed under the above conditions, and 1
Feed per tooth f (mm/tooth) 0.4, 0.5,
Increase it to 0.6, 0.7, 0.8, 0.9, 1.0,
The time when a chip appeared on the cutting edge of the cutting tool was defined as the tool life. The results of this chipping resistance cutting test are shown in Table 1 below. In Table 1, the 〇 mark means that no chipping occurred on both occasions, the △ mark means that chipping occurred only once out of 2 times, and the × mark means that chipping occurred on both occasions. show.

【table】

[Table] In addition, in order to investigate the influence of the pre-sintering atmosphere,
30TiC−70Al ₂ O ₃ 100 parts by weight, 0.5 Y ₂ O ₃
Preliminary sintering was performed by changing the sintering atmosphere so that the theoretical density was 94 to 95%, and then the product was obtained by the HIP method at 1400℃ x 1 hour under 1000Kg/ ^cm2 argon gas pressure. The theoretical density and hardness of the final sintered body are shown in Table 2 below.

[Table] (b) Discussion The temperature required to obtain a pre _- sintered body with the theoretical density required for applying the HIP method is higher than that of a pre-sintered body that does not contain any _{Y 2} O ₃ . As the temperature increases, the temperature gradually shifts to lower temperatures (as can be seen from Figure 1-1 and the fact that 70Al ₂ O ₃ -30TiC required about 1900°C). In more detail, Y ₂ O ₃
When the amount added is 0.025 parts by weight, there is still not much of a temperature drop, but when it exceeds 0.05 parts by weight, a large temperature drop phenomenon is observed depending on the amount added. From the electron micrographs shown in FIGS. 2 and 3, it can be seen that the lower the pre-sintering temperature, the finer the crystal grains can be obtained. In addition, in an example in which 0.25 parts by weight of MgO, a grain growth inhibitor, was added, the results of microscopic observation of the sintered body were as follows.
It was clearly discernible that the crystal grains were finer than those that did not contain MgO, but the pre-sintering temperature shown in Figure 1-2 was slightly lower. The difference is slight;
It was found that the addition of MgO had little effect on lowering the pre-sintering temperature. Also, from the graph shown in Figure 4, when the amount of Y ₂ O ₃ added is 0.025 parts by weight, a slight increase in hardness is observed compared to the case where no addition is made. As is clear from No. 1, the sinterability during preliminary sintering was still poor, and as a result, the constituent crystal grains grew to some extent, resulting in insufficient hardness of H _to A93.0 or less. On the other hand, when 0.05 parts by weight or more of Y ₂ O ₃ is added, the constituent particles become finer (see Figure 5). For TiC/Al ₂ O ₃ + TiC x 100 of 15 to 60, the hardness It shows H _to A93.0 or higher. According to Figure 9, which shows the relationship between HIP conditions and the theoretical density of the final sintered body, under high pressure conditions,
For example, 1350℃ for 2000Kg/cm ² or 1000Kg/cm ²
Although theoretical densities of 98.75% and 98.55% can be obtained at relatively low pressures of 400Kg/cm ² and 350Kg/cm ²
In this case, in order to obtain a theoretical density of 98.5% or higher, high temperatures of 1450℃ and 1550℃ or higher are required, respectively, so normally 1000 to 2000Kg/cm ²
It is preferable to perform HIP treatment under the pressure of It should be noted that as the temperature approaches the high temperature of 1700°C, the holding time can be shortened to about 20 minutes, and it has been confirmed that the growth of the constituent crystal grains can be suppressed. From the results shown in Figure 10, when the amount of TiC in (Al ₂ O ₃ + TiC) is as small as 10% by weight,
When the amount of Y ₂ O ₃ was in the range of 0.25 to 2.0 parts by weight, the H _to A hardness was 93.0 or more (see Figure ₄ ), but _the tool life was short; )
If the amount of TiC inside is too large (70% by weight), the hardness at room temperature is sufficient (see Figure 4), but since TiC has a characteristic of low high temperature hardness, the tool life will be shortened. It has the disadvantage that it becomes shorter, and considering the results in Table 1, (Al ₂ O ₃ +
TiC in TiC) is 15-60% by weight, and the amount of Y ₂ O ₃ is
It turns out that 0.05 to 2.00 parts by weight is preferable. Next, as shown in FIG. 11, which shows the relationship between hardness and tool life, when H _~ A hardness is 93.0 or less, tool life rapidly decreases. The cutting test method adopted here uses extremely harsh conditions for ceramic tool materials, and is designed to allow life to be determined in a short period of time, so a value of 4 minutes or more is suitable for general use. This can be said to have excellent cutting performance. Regarding the atmosphere during preliminary sintering, it is clear from Table 2 that there is no significant change in any gas as long as it is an inert gas or a reducing gas, so argon gas is usually used from the standpoint of safety and economy. Make it. <Experiment> (a) Experimental method and results α-Al ₂ O ₃ with a purity of 99.9% and an average particle size of 0.6μ,
TiC and _Y2O3 with a purity of 99% and an average particle size of 1μ were used, respectively, and _Al2O3 with a TiC content of 10% to 70% by weight _was used _.
A mixture of 100 parts by weight of TiC and various amounts of Y ₂ O ₃ in the range of 0.025 parts by weight to 2.500 parts by weight was wet mixed and pulverized for 20 hours using a ball mill mixer, and then thoroughly dried. As raw materials for sintering, fill a graphite mold of 50 x 50 mm square and 60 mm in height with the above various sintering raw materials, insert it into a high frequency coil, and heat it at each specified temperature within the temperature range of 1350 to 1900 ° C. By applying a pressure of 200Kg/ ^cm2 , holding it for 60 minutes, and then releasing the pressure and leaving it to cool,
A desired sintered body of ×50 × 5.5 mm was obtained. As described above, the hot press temperature for sintering to a theoretical density of at least 98.5% by the hot press method is shown in Table 3 below. However, the pressure in that case was 200 Kg/cm ² and the holding time was 60 minutes.

[Table] In addition, 0.25 parts by weight of MgO was added to each of the raw materials shown in Table 3 above, and hot press sintering was performed in the same way as the results shown in Table 3 above. Although the temperature was slightly lower (5 to 10°C) than in the case without MgO, there was no significant change. In addition, for the material in which 0.5 parts by weight of Y ₂ O ₃ was added to 100 parts by weight of (70Al ₂ O ₃ −30TiC),
The relationship between hot press temperature, pressure, and theoretical density when the holding time is 60 minutes is shown in the 12th table.
Shown in the graph of figure. Furthermore, this (70Al ₂ O ₃ −
Figures 13 and 13 show the electron micrographs of the structure of 70Al ₂ O _{3 -30TiC} (containing no Y ₂ O ₃ at all) and 100 parts by weight of 30TiC) with 0.5 parts by weight of Y ₂ O 3 added. The X-ray diffraction pattern is shown in FIG. 14, and the X-ray diffraction pattern is shown in FIG. 15 and FIG. 16, respectively. The hot press conditions are those containing Y ₂ O ₃ .
1580°C x 60 minutes, 200Kg/cm ² , and the one without Y ₂ O ₃ is 1750°C x 60 minutes, 200Kg/cm ² . Next, the sintered body obtained in this way was cut with a diamond whetstone, and then cut with a No. 220 diamond whetstone using a cutting tool model number SNGN432 and a thread surface dimension of 0.1×.
30° tools were made, and the hardness (Rockwell A scale) of these various tools was measured and the results are shown in the graph of Figure 17. Next, in order to judge the cutting performance of these various tools, a high-hardness material was used as a workpiece using a lathe.
Using SNCM-8 (Hs85), V×d×f=50
Continuous cutting tests were conducted under cutting conditions of m/min x 0.5 mm x 0.2 mm/rev. The tool life criterion at this time was that the tool life was reached when the flank wear width reached 0.3 mm. The results are shown in the graphs of FIGS. 18 and 19. In addition, in order to check the fracture resistance of these various tools,
Cast iron (FC25) V×d=245m/min×1.5mm,
Table 4 shows the results of milling at a feed rate of 0.4 to 1.0 mm/tooth. In this Table 4, the ○ mark indicates that no chipping occurred on both occasions, the △ mark indicates that chipping occurred only once out of 2 times, and the × mark indicates that chipping occurred on both occasions. .

[Table] (b) Consideration 70Al ₂ O ₃ −30TiC containing no Y ₂ O ₃ to obtain a sintered body with a theoretical density of at least 98.5%
Compared to that which requires 1750℃,
As can be seen from Table 3, the sintering temperature of the materials to which Y ₂ O ₃ was added was considerably lower. However, when the amount added is 0.025 parts by weight, the temperature does not decrease much, and when the amount exceeds 0.05 parts by weight, the temperature gradually decreases considerably as the amount added increases. Also, from the graph shown in Figure 12, it can be seen that the higher the temperature and pressure during hot press sintering, the higher the theoretical density of a sintered body can be obtained. Compare Figures 13 and 14. As can be seen, the lower the hot pressing temperature, the finer the crystal grains of the sintered body obtained. According to Fig. 17, which shows the amount of Y ₂ O ₃ added and the hardness of the obtained sintered body, when the amount of Y ₂ O ₃ added is 0.025 parts by weight, it is slightly harder than when no addition is made. Although the hardness increases, as mentioned above, due to the poor hot press sintering conditions (high temperature), the constituent crystal grains grow somewhat, so the hardness is still insufficient at 92.9 at most. On the other hand, when 0.05 parts by weight or more of Y ₂ O ₃ is added, the constituent particles become finer, resulting in TiC/
When Al ₂ O ₃ +TiC×100 is 15 to 60, all values are 93.0 or higher. From the results shown in Figure 18, the amount of TiC in (Al ₂ O ₃ + TiC) is as low as 10% by weight and 70% by weight.
If there is too much, the tool life will be significantly inferior to something in between (Al ₂ O ₃ +TiC).
The amount of TiC inside is considered to be appropriate15,
Even if it is 30 or 60% by weight, the tool life is greatly affected by the amount of Y ₂ O ₃ , and the value required for a cutting tool material (4 minutes is enough) is met when Y ₂ O ₃ is 0.05 It can be seen that it is 2.0 parts by weight. Moreover, it is clear from the results shown in FIG. 19 that the hardness of the sintered body required is H _to A93 or higher. As described above, the ceramic sintered body according to the present invention is highly hard and dense, and exhibits excellent properties when used as a cutting tool, for example. These characteristics increase the hardness from H _to A93.0 or higher,
It is even better when the theoretical density is 98.5% or more. Furthermore, the ceramic sintered body having a constituent particle diameter of 10 μm or less is even more excellent. Next, in the method for manufacturing a ceramic sintered body according to the present invention, the sintering temperature can be significantly lowered, so that the constituent particles can be made finer.

[Brief explanation of drawings]

Figure 1-1 shows the experimental temperature and TiC, TiO ₂ ,
The graph showing the relationship of Y ₂ O ₃ , Figure 1-2 is similarly
Temperature and TiC when 0.25 parts by weight of MgO is included,
A graph showing the relationship between TiO ₂ and Y ₂ O _3. Figure 2 is an electron micrograph of the experimental material after preliminary sintering of 100 parts by weight of (70Al ₂ O ₃ - 30TiC) - 0.5 parts by weight of Y ₂ O ₃ . , Figure 3 is an electron micrograph of the experimental material 70Al ₂ O ₃ -30TiC after preliminary sintering, Figure 4 is a graph showing the hardness of various sintered bodies in the experiment, and Figure 5 is the ( 70Al ₂ O ₃ −30TiC) 100 parts by weight −
Figure 6 is an electron micrograph of the experimental material 70Al ₂ O _{3 -30TiC} after HIP, and Figure 7 is _the experimental (70Al ₂ O ₃ −30TiC) 100 parts by weight −Y ₂ O ₃ 0.5
The X-ray diffraction pattern after HIP of the material (weight part), Figure 8 is the X-ray diffraction pattern after HIP of the experimental material 70Al ₂ O ₃ -30TiC, and Figure 9 shows the change in theoretical density depending on the experimental HIP conditions. Figures 10 and 11 are graphs showing the experimental continuous cutting test results, Figure 12 is a graph showing the change in theoretical density depending on the experimental hot press conditions, and Figure 13 is the experimental (70Al ₂ O ₃ −30TiC) 100 parts by weight−
Electron micrograph of the material consisting of 0.5 parts by weight of Y ₂ O ₃ ,
Fig. 14 is an electron micrograph of the experimental material 70Al ₂ O ₃ -30TiC, and Fig. 15 is an X-ray of the experimental material 100 parts by weight (70Al ₂ O ₃ -30TiC) - 0.5 parts by weight Y ₂ O ₃ Diffraction pattern, Figure 16 is the experimental one.
X-ray diffraction pattern of material 70Al ₂ O ₃ -30TiC, 1st
Figure 7 is a graph showing the hardness of various sintered bodies in the experiment.
FIG. 18 and FIG. 19 are graphs showing the results of continuous cutting tests, respectively. In the figures, the magnification of all electron micrographs is 3000x.

Claims (1)

[Scope of Claims] 1. An element body molded from a raw material powder having a composition of 15 to 60 weight percent titanium carbide, the balance 100 parts by weight of aluminum oxide, and 0.05 to 2.00 parts by weight of yttrium oxide is exposed to a reducing gas. Or a ceramic sintered body characterized by pre-sintering in an inert gas atmosphere so that the theoretical density becomes 94% or more, and then sintering the pre-sintered body under hot isostatic pressure. Production method. 2 15 to 60% by weight of titanium carbide, 100 parts by weight of aluminum oxide and yttrium oxide
1. A method for producing a ceramic sintered body, comprising hot press sintering raw material powder containing 0.05 to 2.00 parts by weight.