JPS60171264A - Ceramic structural part and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to ceramic, gas structural parts, I-rings, and seals that can be reused under high temperature and high force conditions such as gas turbines and automobile engines. The present invention relates to ceramic structural parts that can be used for a single period under such conditions that require wear resistance and chemical resistance, and a method for producing the same.

[Background of the invention]

Silicon carbide, silicon nitride, Sialon (81, At.

For example, ceramics such as 0・N solid solution)
It is expected to find wide application as structural parts that require high strength at temperatures above 0°C. Furthermore, ceramics such as ZrO2 and At203 are expected to be used as structural parts that require wear resistance and chemical resistance.

However, these ceramics and clays have the disadvantage of being unreliable as structural materials due to large variations in strength, weakness in thermal shock and mechanical impact, etc.
This has hindered the practical application of these ceramic structural parts. These drawbacks are due to the fact that conventional ceramics are brittle materials and easily break due to stress concentration on surface and internal defects that are inevitable in the manufacturing process of ceramics.

[Purpose of the invention]

The entire purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art and provide a highly reliable ceramic structural component of this type with little variation in strength, high resistance to thermal shock and mechanical shock, and a method for manufacturing the same. .

[Summary of the invention]

The ceramic structural component of the present invention is a ceramic particle sintered body having a structure in which metal is dispersed in the grain boundaries of ceramic particles, and having a characteristic that deformation resistance at low strain is smaller than deformation resistance at high strain. It is characterized by being different. Here, deformation resistance means a differential coefficient obtained by differentiating stress with displacement due to strain.

The ceramic particles constituting all the ceramic structural parts of the present invention are silicon carbide, silicon nitride, SiAlON or Z
At least one of r02 and At2o5 is preferable.

One method for manufacturing the ceramic and glass structural parts of the present invention includes the steps of mixing at least one of silicon carbide, silicon nitride, or sialon powder with a metal and a sintering aid, molding, and firing. In the firing process, the heating rate is 15°C/min or higher at 100°C or higher, and the product is immediately cooled to at least 1000°C at a cooling rate of 15°C/min or higher without being held at the maximum temperature. It is something.

(Also, another manufacturing method for the ceramic structural parts of the present invention is Z
It consists of the steps of mixing metal or a compound that decomposes during sintering to produce metal particles with metal oxide powder such as rO2 or At2o3, molding, and firing.In the firing process, the heating rate is 800℃ or higher. is set at 7° C./min or more, and the special feature is that the temperature is immediately cooled to at least 800° C. at a cooling rate of 7° C./min or more without being held at the maximum temperature.

[Embodiments of the invention]

FIG. 1 is a characteristic curve showing the relationship between stress and displacement due to strain in a ceramic structural component, with curves A and C showing the conventional curve, and curve B illustrating the curve according to the present invention. The slope of the curve is the deformation resistance, which corresponds to Young's modulus in the elastic region.

As a result of various studies conducted by the present inventors, the deformation resistance of conventional ceramic and glass structural parts has a large value that is almost constant regardless of strain, as shown in the curve shown in Figure 1. It was found that when stress is applied, if there is a defect, the stress is concentrated on the defect and breaks at a relatively low stress, resulting in low 4N reliability. On the other hand, if a ceramic material having a relatively small deformation resistance at low strain and a large deformation resistance at high strain is used, as shown by curve B in FIG. The resistance effect causes a slight deformation to relieve stress concentration, and then the local deformation resistance effect allows the product to withstand large stresses, resulting in highly reliable ceramic/cushion structural parts with less variation in strength due to defects. I found out that I can get it. In addition, the small deformation resistance at low strain is effective in alleviating stress concentration during thermal shock and mechanical shock, and combined with the subsequent large deformation resistance at high strain, ceramic structural parts have a large resistance to thermal shock. It was found that this material has a significant effect on durability and mechanical impact resistance.

Such ceramic materials, which have a small deformation resistance at low strain and a large deformation resistance at high strain, are silicon compound particles with high heat resistance and high rigidity and Young's modulus, such as silicon carbide, silicon nitride, or sialon, or Zr02 or This can be achieved by dispersing metal at the grain boundaries of an aggregate of metal oxide particles such as At203. When stress is applied to a ceramic material with such a structure, the metal at the grain boundaries deforms, so the deformation resistance is low, but when deformed beyond a certain limit, silicon compound particles or metal oxides with large rigidity and Young's modulus Deformation resistance increases due to the influence of particles, and further deformation is prevented.

FIG. 2 is a schematic diagram showing the microstructure of the ceramic structural component of the present invention. In the figure, 1 is a ceramic particle such as silicon carbide, silicon nitride, Sialon, ZrO2, At205, etc., and 2 is a metal particle precipitated at the grain boundary of an aggregate of these particles. As shown in the figure, when metal exists in some of the grain boundaries of a particle aggregate and does not surround all particles, it has a characteristic of having small deformation resistance especially at low strains and large deformation resistance at high strains. Since it is easy to realize
This structure is particularly desirable. As a result of experiments, the above characteristics are particularly easy to achieve when metal exists only in a part of the grain boundaries of a particle aggregate,
On the other hand, it has been confirmed that in a structure in which all particles are surrounded by metal, such as commercially available cermet, large deformation resistance is less likely to occur when the strain is high.

The content of silicon carbide, silicon nitride, sialon, ZrO2 or At203 in the ceramic structural material of the present invention is desirably 50 molar or more. If the content is lower than this, the strength of silicon carbide, silicon nitride, and sialon will decrease when used in air at temperatures above 1000°C, and the wear resistance of ZrO2 and At2o3 will decrease. Chemical resistance, etc. decreases, and the reliability of ceramic structural parts decreases.

The metal to be contained is preferably a high melting point metal element such as silicon carbide, silicon nitride, 111a in the case of Sialon, ①a or Va group element. If the melting point of the metal at the grain boundary is too low, the resultant ceramic or glass structure part will have a
This is undesirable because the strength at high temperatures of 0° C. or higher decreases. Note that it is particularly desirable to use T1%V or Cr as the metal element because a ceramic structural component having not only excellent heat resistance but also excellent oxidation resistance can be obtained. On the other hand, ZrO2, Az
In the case of 2o3, it is desirable to contain metals with high oxidation resistance such as pt and Cr.

In addition, when using a combination of a silicon compound such as silicon carbide, silicon nitride, or sialon and a metal of group II [a, Ma%Va group element, a part of the metal particle surface generally reacts with the silicon compound during sintering and forms a compound. Because of this, the adhesion between the silicon compound and the metal particles is very strong, and the strength of the resulting ceramic structure is particularly high.

The metal content in the ceramic structural component of the present invention is preferably in the range of 3 to 20 moles. If the gold dust content is less than this range, it will not be effective in reducing the deformation resistance at low strain, and if it is more than this range, the deformation resistance will not become large at high strain.

In this way, at least one of silicon carbide, silicon nitride, or Sialon is contained as a particle aggregate of 50 mol or more, and 1 liter of silicon carbide, silicon nitride, or sialon is contained in one grain boundary of the particle aggregate.
a, IVa or Va group metal in the form of an elemental metal, 3 to 2
Ceramic materials with a zero molar ratio structure provide ceramic structural components that can be used reliably under high stress and thermal shock conditions at high temperatures of about 1000° C. or higher, such as in gas turbines and automobile engines.

In order to obtain a material having the above structure, at least one of silicon carbide, silicon carbide, or sialon is mixed with a metal and a sintering aid, and after being formed into a predetermined shape, it is fired. Sintering aids include aluminum compounds, boron compounds, Y2O3
,'go s CeO2 and the like can be used.

During this firing, it is important not to hold the temperature at a temperature at which metal diffusion becomes active, that is, at a temperature of 1000° C. or higher, for a long period of time. If the holding time at 1000°C or higher is too long, the metals will progress to sinter and form large aggregates, or the metals will react with silicon carbide, silicon nitride, sialon, etc., causing the above structure to change. It can't be achieved. Therefore, the temperature increase rate at 10,000℃ or higher is set to 15℃/min or higher, and after the temperature is raised to the sintering temperature of silicon carbide, silicon nitride, or sialon, the temperature is immediately cooled to at least 1000℃ at a cooling rate of 15℃/minute or higher. It is necessary to use a fired glofill that undergoes rapid heating and cooling.

The ceramic structural parts of the present invention as described above can also be made in a similar process using metal oxides such as ZrO2 or m2O3 as the ceramic particles. In this case, it is possible to mix platinum powder or chromium powder as an additive metal, or to add, for example, chloroplatinic acid or chromium nitrate, which decomposes during sintering to produce platinum particles or chromium particles, followed by molding and firing. In the firing process, in order to obtain a grain boundary metal dispersion structure in the same manner as above, the temperature increase rate should be f near ℃/min or more at 800℃ or higher, and the temperature decrease rate should be 7C/min or higher immediately after reaching the maximum temperature. It is necessary to use a firing filler that is rapidly heated and cooled to at least 5 ooc. Ceramic structural parts obtained by this method can be used for parts that require heat resistance at temperatures below 1000°C, wear resistance, chemical resistance, thermal shock resistance, etc., such as pump materials, sealing materials, and cutting tools. A wide range of applications are possible.

Hereinafter, specific examples of the present invention will be described together with comparative examples.

[Example 1] Si3N4 powder with an average grain size of 0.5 μm was mixed with Y2O54 morch and At2054 morch with an average grain size of 1 μm as sintering aids. Next, add this to the average particle size of 0
605 μm Cr powder was mixed in the proportions shown in Table 1, 51 PVA (polyvinyl alcohol) water bath liquid was added as a binder at 10% by weight based on the total powder, and 60φ×5t (unit part) was prepared using the horn 4-press method. It was molded into. Next, this was sintered using a temperature profile in which the temperature was raised at a temperature increase rate of 15 C/min in a nitrogen gas atmosphere of 4 atm, and immediately after reaching the maximum temperature of 1850 °C, it was cooled down to 1000 °C at a cooling rate of 15 °C/min. 0 The obtained sample was cut into 3 x 4 x 35 pieces, the surface was polished with diamond paste, and the bending strength and strength variation were measured using the 4-point bending method (Tsuchibe Sunoyan 30 m, Lower Sunoman 1O■). The Weibull coefficient was measured. In addition, after exposing the sample to hot air at 1000℃ for 10 minutes,
fr: Thermal shock test (e) of 10 minutes of application was repeated for 100 cycles, and the bending strength and wipe coefficient a were measured. The measurement results are shown in Table 1. As a result of the analysis, about half of the added Cr remained as metal Cr, and the rest was Cr5.
It turns out that it has changed to 12. C shown in Table 1
The amount r is the amount of Cr present as a simple metal.

In Table 1, sample points 3 to A6 are examples of the present invention, A1,
2 and 7 are comparative examples.

As seen in Table 1, the initial characteristics of the A3 to flat 6 samples with a Cr content of 3 to 20 moles, which are examples of the present invention,
It can be seen that both the bending strength and the Weibull coefficient are large in the properties after thermal shock, and the reliability as a structural component is high. The displacement (strain)-stress characteristics of sample point 4 are shown in FIG. 1B. As described above, this sample has a characteristic that the deformation resistance is small when the strain is low, and the deformation resistance is large when the strain is high. Similar trends were also observed in samples A3, 5, and 6.

On the other hand, A in FIG. 1 shows the characteristics of sample Al, which is a comparative example.
C in the figure similarly shows the characteristics of sample A7, and it can be seen that the deformation resistance of these comparative examples is constant regardless of strain.

Furthermore, when the structure of the sample of the above-mentioned example of the present invention was observed, as shown in FIG. It was done.

Incidentally, litchi cylinders and pistons for automobile engines were produced in the same manner using the compositions of Samples A3°4.5 and 6 of Examples of the present invention. Using the obtained automobile engine, we performed start-stop cycles and continuous operation, but no problems such as breakage were observed.

[Example 2] In the same manner as in Example 1, 5i5N4 was treated with I shown in Table 2.
Add Va, Va, Ma group elements and apply pressure 300
kg/crn2, heating rate 20℃/min, maximum temperature 180
Hot press sintering was carried out using a temperature profile in which the temperature was set at 0C and immediately after the maximum temperature was reached, the material was cooled down to 1000C at a cooling rate of 15C/min. Table 2 also shows the characteristics of the samples measured in the same manner as in Example 1. In Table 2, sample point 9~
12 and A15-18 are examples of the present invention, Jf
6.8.13, 14, and 19 are comparative examples.◎ The ratio of the amount added and the amount present in the form of metal changes depending on the type of metal added, but the amount present as a metal is 3 to 2.
It can be seen that the bending strength and the Weisol coefficient are large in the samples of the examples of the present invention, which are within the range of 0 mol. Also,
In these samples, similar to FIG. 1B, it was observed that the deformation resistance was small when the strain was low, and large when the strain was high.

[Example 3] Average particle size 0.7 μm 05L5N4 powder with average particle size 0.5
μm of At203, average grain size of 2 μm of AtN, and average grain size of 1 μm of st, o2 are expressed by the general formula 'S i
6-, Az, o, Na-, were weighed so that 2 was 0.5 to 2.0, and 15 weights of the metal powder and low polymerized polyethylene shown in Table 3 were added to this, and 1500 kl/ c.
Injection molding was carried out at a pressure of m2. The molded body was then heated in nitrogen gas at a heating rate of 20°C/min to a maximum temperature of 1700'C.
Immediately after reaching the temperature, sintering was carried out by cooling at a temperature rate of 20 l/min. Table 3 shows the relationship between the metal content and properties of the obtained samples.

In Table 3, the samples of the embodiments of the present invention are 20.21
．． 22, 24, 25, 26. 27, animal restaurant '23
and 28 are comparative examples. It can be seen that the sample according to the example of the present invention has a large bending strength and a large wipe coefficient. Furthermore, in these samples, similar to FIG. 1B, it was observed that the deformation resistance was small when the strain was low, and large when the strain was high. Furthermore, a 40φ turbocharger rotor was made from the same material as these samples, and a rotation test was conducted by intermittently blowing air at 1100°C, but there were no problems such as damage.

[Example 4] For α-type SIC powder of 8,000 mm, an average particle size of 2 m
2 mol of AtN and 30 mol of W powder having an average particle size of 2 μm were added, and after molding, hot press sintering was performed in vacuum at a maximum temperature of 2100°C. In this sintering, the temperature was raised at a temperature increase rate of 20° C./min, and after reaching the maximum temperature, it was immediately cooled at a temperature decreasing rate of 20° C./min without holding time. In this sample, when the amount of W present in the form of a single metal in the sample was 4 mol, it was observed that the deformation resistance was small at low strain and large at high strain.

[Example 5] ZrO2 with an average particle size of 0.5 μm has an average particle size of 0
．． 5 μm of Y2O3 and an aqueous solution of chloroplatinic acid (5 mol% in terms of pt) and 10% of a 5% i% PVA aqueous solution were added and mixed well. This was then molded and sintered in air at a maximum temperature of 1550°C. In addition, during firing, the temperature increase rate at 800°C or higher is 10°C/min, and the temperature is increased immediately by 10°C to 800°C without being held at the maximum temperature above.
A temperature glofil that cools at a cooling rate of /min was used.

The obtained sample had a structure in which PT was precipitated in the form of metal with a grain size of about 0.1 to 0.5 μm at some places at the grain boundaries of ZrO2. As a result of the bending test of this sample, it was found that the deformation resistance was small when the strain was low, and it was large when the strain was high.

A similar tendency was also observed when platinum particles with an average particle size of 0.1 μm were used instead of chloroplatinic acid.

Furthermore, as a result of a study on the rising and falling rate, it was found that it is desirable that the temperature rising and falling rate is 7°C/min or more; if the rising and falling rate is too slow, the metal particles will aggregate and the dispersibility in the sintered body will deteriorate. I knew it would get worse.

Similar results were obtained when A4203 was used in place of ZrO2, and chromium powder or chromium nitrate was used in place of platinum.

〔Effect of the invention〕

According to the present invention, there is little variation in strength, thermal shock resistance and
It is possible to obtain a highly reliable ceramic structural component with high mechanical impact resistance.

[Brief explanation of drawings]

Fig. 1 is a characteristic curve diagram showing the relationship between six forces and strain for samples of examples of the present invention and comparative examples, and Fig. 2 is a diagram showing the microstructure of the ceramic sintered body of the present invention. Particle 2...Precipitated metal Figure 1 Figure 2

Claims (1)

[Claims] 1. Ceramic particle sintered body having a structure in which metal is dispersed in the grain boundaries of ceramic particles, and having a characteristic metal in which deformation resistance at low strain is smaller than deformation resistance at island strain. Ceramic structural parts with all the characteristics. 2. The ceramic structural component according to claim 1, wherein the ceramic particles are at least one of silicon carbide, silicon nitride, sialon, ZrO2, and At203. 3. The content of at least one of silicon carbide, silicon nitride, Sialon, ZrO2, or At2o3 is 50 moles or more, and the content of elemental metals is 3 to 20 moles! A ceramic structural component according to claim 2 within the scope of the present invention. 4. Consists of each process of mixing at least one of silicon carbide, silicon nitride, or sialon powder with a metal and a sintering aid, molding, and firing, and in the firing process, 1
Ceramic structural parts characterized in that the heating rate at 15°C/min or higher at 000°C or higher is immediately cooled to at least 1000°C at a cooling rate of 15°C/min or higher without being held at the maximum temperature. Manufacturing method. 5. In the wide-area forming step, which includes the steps of mixing a metal or a compound that decomposes during sintering to produce metal particles with metal oxide powder such as ZrO2'E or At2o3, molding, and firing, the temperature is 800°C. A method for manufacturing a ceramic structural component, characterized in that the temperature increase rate is 7° C./min or more, and immediately the temperature is cooled to at least 800° C. at a temperature decreasing rate of 7 C/min or more without being held at the maximum temperature.