JPH09263455A - Manufacture of ceramic turbine rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the manufacture by which the defective product generation rate can be reduced and the burst rotational speed of the product rotor can be enhanced, at the time of manufacturing a silicon nitride based ceramic turbine rotor with fitting and sintering. SOLUTION: In this manufacture, powdery Si3 N4 is subjected to wet mixing with powdery Y2 O3 , AlN and Al2 O3 and then, the powdery mixture is dried with a spray dryer. Thereafter, an organic binder is added to the dried powdery mixture and the resulting mixture is kneaded with a kneader and then, the kneaded mixture is subjected to injection molding with an injection molding machine into a blade molding and further, the blade molding is dewaxed in a non-oxidizing atmosphere to obtain a blade dewaxed body 1. On the other hand, in order to form a shaft of the rotor, the above kneaded mixture contg. the binder is dewaxed and thereafter, the dewaxed mixture is disintegrated and granulated into a granulated powder and then, the granulated powder is subjected to pressure compacting with a hydrostatic pressure to obtain a shaft dewaxed compact 3. The blade dewaxed body 1 and the shaft dewaxed compact 3 are engaged with each other and thereafter, the resulting engaged body is subjected to ordinary pressure sintering at 1,700 deg.C in a nitrogen atmosphere to obtain a ceramic sintered body used as the objective ceramic turbine rotor 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a silicon nitride ceramic turbine rotor used for heat engine parts such as a gas turbine rotor and a turbocharger rotor.

[0002]

2. Description of the Related Art Conventionally, silicon nitride is more stable at high temperatures than metals and is excellent in oxidation resistance and creep resistance, and therefore, research has been conducted for use in engine parts such as turbine rotors. ing.

Further, as a method of manufacturing a turbine rotor, a technique described in, for example, Japanese Patent Laid-Open No. 60-11276 is known. This is a technology that takes into consideration the fact that the thickness of the parts manufactured by injection molding is limited due to the problem of the degreasing process, and when manufacturing turbine rotors that are large in shape and cannot be injection-molded as a unit. Is a method in which a blade portion having a complicated shape is molded by injection molding, and a shaft portion having a simple shape is molded by hydrostatic pressure molding, and the degreased bodies of both are fitted and fired.

FIG. 3 shows a manufacturing process of manufacturing such a turbine rotor using silicon nitride as a material, that is, a manufacturing process of a silicon nitride fitting turbine rotor. First, in the case of forming the blade portion, the silicon nitride raw material and the auxiliary agent are mixed and dried, the organic binder component is added, and the mixture is kneaded by a kneader kneader and pelletized and then injection-molded to form the blade portion. Has obtained the shape of. Then, after the wing portion is molded, the degreasing is performed. In addition, degreasing is
Usually, it is performed by heating to a temperature at which the organic binder is thermally decomposed or disappears, and is sometimes called resin removal.

In the kneading step, crushing of silicon nitride particles occurs, the average particle diameter becomes smaller and the particle size distribution becomes narrower, and at the same time, the appearance of a new silicon nitride surface oxidizes the silicon nitride and the oxygen content in the matrix. (SiO ₂ amount) increases. Further, a slight amount of metal component is mixed due to abrasion of the kneading device during the kneading step, but this metal component promotes densification, although slightly. That is, by adopting this kneading step, the blade portion is likely to shrink when the wing is densified in the subsequent firing step.

On the other hand, when the shaft portion is formed, the base material obtained by mixing the silicon nitride raw material and the auxiliary agent, drying and granulating is subjected to hydrostatic pressure processing to obtain the shape of the shaft portion. Then, after molding the shaft portion, post-processing such as outer diameter correction is performed and then degreasing is performed. Since there is no kneading process like the blade in the manufacturing process of the shaft, the shaft tends to shrink less than the blade when it is sintered.

Next, the wing portion and the shaft portion are fitted to each other, and they are joined together by hydrostatic pressure and then fired and sintered. At this time, due to the tendency of shrinkage, the density relationship between the blade portion and the shaft portion at each firing temperature in the firing step is as follows: blade portion> shaft portion,
The difference is 3 to 10% in relative density. Then, post-processing such as finishing is performed to complete the silicon nitride fitting turbine rotor.

[0008]

The above-mentioned method can also produce a product of a certain quality, but when a turbine rotor having a large size, for example, a diameter of 100 mm or more is produced by this method. Due to the difference in relative density between the blade and the shaft during the sintering process, the mating surface is not sharp after firing (defects due to cracks on the mating surface).
There was a problem that many occur.

Further, there is a problem that the burst rotational speed (rotational speed at which it breaks) of the turbine rotor is a value considerably lower than the value predicted from the material strength, for example, the stress ratio is as low as about 0.5. It was (However, stress ratio = stress value calculated from rotation speed / actual material strength) The present invention has been made to solve the above-mentioned problems, and a silicon nitride turbine rotor is manufactured by fitting and firing. If you do, while reducing the incidence of defective products,
An object of the present invention is to provide a method for manufacturing a ceramic turbine rotor capable of increasing the burst rotation speed.

[0010]

In order to achieve the above-mentioned object, the invention of claim 1 sinters after fitting the injection-molded blade degreased body and the hydrostatic pressure-molded shaft degreased body. In the method for manufacturing a silicon nitride turbine rotor according to claim 1, the density difference between the blade portion and the shaft portion at each temperature in the sintering process is set to within 1% in relative density. Is the gist.

According to a second aspect of the present invention, there is provided a method for manufacturing a silicon nitride turbine rotor in which a blade degreased body formed by injection molding and a shaft degreased body formed by hydrostatic pressure molding are fitted and then sintered. Fit the degreased blades that are degreased by injection-molding the mixture and the organic binder mixed into the siliceous base, and the degreased body that is hydrostatically pressure-molded after degreasing the mixture obtained by the same kneading. Then, the gist is a method for manufacturing a ceramic turbine rotor, which is characterized in that the sintering is performed.

A third aspect of the present invention is a method for manufacturing a silicon nitride turbine rotor in which an injection-molded blade degreased body and a hydrostatic pressure-molded shaft degreased body are fitted and then sintered. Using a degreased blade portion obtained by mixing an organic binder by kneading into a siliceous base material, injection molding the mixture, and degreasing the same, and a silicon nitride material having the same oxygen content, metal content, particle size, and particle size distribution as the above mixture. A method for manufacturing a ceramic turbine rotor is characterized in that a shaft degreased body formed by hydrostatic pressure molding is fitted and the sintering is performed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the density of the blade portion and the shaft portion at the temperature during firing (each temperature during the sintering process) The present inventors have completed the present invention by discovering that the difference affects the occurrence of defective snapping of the fitting portion and the reduction of the burst rotation speed.

Therefore, according to the first aspect of the invention, the density difference between the blade portion and the shaft portion at each temperature in the sintering process is 1 in relative density.
By setting the content to be within the range of%, it is possible to prevent the defective snapping of the fitting portion. That is, not only the final sintering temperature but also the temperature range of the sintering process, that is, if there is a large difference in the density between the blade and the shaft at any stage of the sintering process, there is a difference in the amount of shrinkage at that stage. Occurs and the fitting portion is sharpened. Further, even when the breakage does not occur, distortion occurs in the blade and the shaft due to the difference in the amount of contraction, and it is considered that this distortion affects the burst rotation speed.

Therefore, in the present invention, in all temperature regions of the sintering process, the difference between the relative densities of the blade portion and the shaft portion is set to be within 1%, so that the shrinkage amounts of both are almost equal and the occurrence of cracking occurs. It is considered that the occurrence of distortion can be suppressed and the burst rotation speed can be improved.

The invention of claim 2 specifically shows means for keeping the density difference between the blade portion and the shaft portion within 1% in relative density. Here, the blade degreased body is formed by mixing an organic binder by kneading into a silicon nitride base material and injection-molding and degreasing the mixture, while the shaft degreased body is kneaded for manufacturing the blade portion. The mixture thus obtained is used as a material, and after degreasing, isostatic pressing is performed.

That is, when manufacturing the wing portion and the shaft portion,
In the same kneading process, as described above, the crushing of silicon nitride particles reduces the average particle size, narrows the particle size distribution, and at the same time increases the oxygen content in the base material and densifies the metal powder. Is promoted. As a result, in all temperature regions during sintering, the shank densifies like the wings,
The relative density difference between the blade portion and the shaft portion can be set to be within 1%, thereby preventing the fitting portion from being defectively cracked and significantly improving the burst rotation speed.

Since the mixture for forming the shaft portion is used for hydrostatic pressure molding rather than injection molding, it is degreased before molding in order to remove unnecessary organic binder. Prior to the hydrostatic pressure molding, the mixture after degreasing is usually crushed and granulated.

The invention according to claim 3 also specifically shows means for keeping the density difference between the blade portion and the shaft portion within 1% in relative density. Here, the blade degreased body is formed by mixing the organic binder by kneading into the silicon nitride base material, injection-molding the mixture and degreasing the mixture. The mixture obtained by kneading the binder is not used as a material for the shaft portion as it is, but a material manufactured separately from it is used. That is, isostatic pressing is performed using a silicon nitride material having the same oxygen content, metal content, particle size, and particle size distribution as the mixture for the blade.

In this case, since the shaft portion is molded by hydrostatic pressing, the organic binder used for injection molding is not necessary, of course. With this method as well, an effect similar to that of claim 2 can be obtained. That is, in all temperature regions during sintering, the shaft portion is densified in the same manner as the blade portion, so that the relative density difference between the blade portion and the shaft portion can be kept within 1% in terms of relative density. It is possible to prevent a sharp defect in the portion and to significantly improve the burst rotation speed.

[0021]

EXAMPLES Examples of a method for manufacturing a ceramic turbine rotor according to the present invention will be described below. (Example) The manufacturing process of the ceramic turbine rotor of this example is shown in FIG.

S with an average grain size of 0.75 μm and an α ratio of 95%
i ₃ N ₄ powder, Y ₂ O ₃ having an average particle size of 1 to ₃ μm, AlN,
Al ₂ 0 ₈ (6: 3: 3) were wet-mixed in a ratio by weight of,
It was dried with a spray dryer. With respect to 100 parts by weight of the obtained powder, polyethylene resin (13 parts by weight) and microcrystalline wax (10 parts by weight) were used as an organic binder.
Parts by weight) and dibutyl phthalate (2 parts by weight) at a total ratio of 25 parts by weight (corresponding to 50% by volume), and kneading is carried out for 15 hours with a kneader. Then, using the mixture produced by this kneading, the blade portion was molded by an injection molding machine under predetermined injection conditions.

Next, the blade body was degreased in a non-oxidizing atmosphere (for example, in a nitrogen atmosphere). For example, heating up to 450 ° C. at a heating rate of 2.5 ° C./hr,
After that, the temperature rising rate was increased to 7.5 ° C / hr to 700 ° C.
Up to 700 ° C for 2 hours, cool down,
Degreasing is performed by heating in air to a temperature of 450 ° C. at a temperature rising rate of 100 ° C./hr and holding at 450 ° C. for 2 hours to obtain a blade degreased body having a diameter of 100 mm shown in FIG. Got 1.

Further, the same mixture was degreased in order to manufacture the shaft portion. The degreasing condition is, for example, heating in a nitrogen atmosphere up to 450 ° C. at a temperature rising rate of 10 ° C./hr, and thereafter increasing the temperature rising rate to 50 ° C./hr to 7 ° C.
After heating up to 00 ° C and cooling, 450 in the atmosphere
It is heated up to 100 ° C. at a temperature rising rate of 100 ° C./hr and kept at 450 ° C. for 2 hours.

Thereafter, the mixture was crushed and granulated, and the granulated powder (particle size of 500 μm or less) was used to hydrostatically press the shaft portion, and the shaft before processing shown in FIG. A partially defatted body 2 was obtained. The shaft degreased body 2 before this processing is replaced with the blade degreased body 1 described above.
The shaft degreased body 3 was obtained by processing into a predetermined shape shown in FIG. 2 (c) using a cemented carbide bit so as to be closely fitted into the fitting hole 1a.

Incidentally, the (degreasing) after the hydrostatic pressure molding of the shaft portion of FIG. 1 is appropriately carried out when the removal of the used organic binder and the like is not sufficient. Next, after fitting the blade degreased body 1 and the shaft degreased body 3,
Pressureless sintering was performed in a nitrogen atmosphere under the conditions of a temperature rising rate of 600 ° C./hr and a final firing temperature of 1700 ° C.
Finally, polishing was performed to obtain a sintered body of the ceramic turbine rotor 4 shown in FIG. 2 (c). (Comparative Example) Next, a method of manufacturing a ceramic turbine rotor of a comparative example used in an experiment described later will be briefly described.

Y ₂ O ₃ , AlN, and Al ₂ O ₈ were added to the same Si ₃ N ₄ powder as in the above-mentioned Examples in the same proportions, wet mixed, and dried by a spray dryer. In the obtained powder,
The organic binder was added at the same ratio, and the mixture was kneaded with a kneader kneader for 15 hours. The mixture was used to mold a blade with an injection molding machine. The blade formed body was degreased in a non-oxidizing atmosphere in the same manner as in the above-mentioned example to obtain a blade-shaped degreased body having the same shape.

Further, the average particle size is 0.75 μm and the α ratio is 95.
% Si ₃ N ₄ powder to Y ₂ O ₃ , A having an average particle size of 1 to ₃ μm.
1N and Al ₂ O ₃ were wet mixed at a weight ratio of (6: 3: 3), and granulated and dried with a spray dryer. Using the granulated powder, the shaft portion was hydrostatically pressure-molded and processed into a predetermined shape to obtain a shaft portion having the same shape as that of the example. Incidentally, in the case of this shaft portion, since no organic binder is added, degreasing is not performed.

Next, after fitting the blade degreasing body and the shaft portion,
Atmospheric pressure sintering was performed in a nitrogen atmosphere at 1700 ° C., and finally polishing was performed to obtain a sintered body of a ceramic turbine rotor having the same shape as that of the example. (Experimental Example) Next, an experimental example performed to confirm the effect of the present embodiment will be described.

When the ceramic turbine rotor was manufactured by the method of the above-mentioned embodiment, the relative density at each temperature during the sintering process was measured separately for the blade portion and the shaft portion. Then, the density difference between the relative densities (= the density of the blade portion-the density of the shaft portion) was also obtained. For the density measurement at each temperature, the firing was stopped when the temperature reached an arbitrary temperature on the sintering schedule, and the density was measured by the Archimedes method.

However, relative density = {actual density (g / cm
³ ) / calculated density in mixed composition (g / cm ³ )} × 10
0 (%) Further, the failure rate of the failure of the fitting portion between the blade portion and the shaft portion after firing was observed, and the failure rate was determined.

However, the defective rate of scratches = the rate of occurrence of 30 prototypes, the completed ceramic turbine rotor was rotated, and the burst rotational speed thereof was measured. The experimental results are shown in Table 1 below. Also, a ceramic turbine rotor was manufactured by the manufacturing method of the comparative example, and the same experiment was conducted. The results are also shown in Table 1.

[0033]

[Table 1]

As can be seen from Table 1, in the manufacturing method of this embodiment, in which the same kneaded mixture is used as the material for the blade and the shaft, the blade and the shaft are formed at each temperature in the sintering process. Since the difference in relative density was less than 1.0% and the difference in density was small, the rate of occurrence of crack failure in the fitting portion of the sintered ceramic turbine rotor was 0%, which was preferable. Further, the burst rotation speed was as high as 147,000 rpm, which was also suitable from this point.

On the other hand, in the manufacturing method of the comparative example (without using the similarly kneaded mixture), the difference in relative density between the blade and the shaft at each temperature in the sintering process is 1.0.
%, And there is a large difference in density, and the occurrence rate of defective cracking at the fitting portion of the sintered ceramic turbine rotor is as large as 50%, which is not preferable. The burst rotation speed is also low at 121,000 rpm, which is also not preferable.

Needless to say, the present invention is not limited to the above-mentioned embodiments, and can be carried out in various modes without departing from the gist of the present invention.

[0037]

As described in detail above, according to the method for manufacturing a ceramic turbine rotor manufactured by fitting and sintering silicon nitride based on the inventions of claims 1 to 3, the sintered ceramic turbine rotor The remarkable effect that the occurrence rate of the breakage defect in the fitting portion is lowered and the burst rotation speed is increased.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a manufacturing process of a ceramic turbine rotor of an embodiment.

FIG. 2 shows an example ceramic turbine rotor,
(A) is a front view showing a part of the blade portion thereof cut away, (b) is a front view showing a shaft portion thereof, and (c) is a front view showing a turbine rotor partly cut away.

FIG. 3 is an explanatory view showing a manufacturing process of a conventional ceramic turbine rotor.

[Explanation of symbols]

 1 ... Blade degreasing body 2 ... Shaft degreasing body before processing 3 ... Shafting degreasing body 4 ... Ceramic turbine rotor

Claims (3)

[Claims] 1. A method for manufacturing a silicon nitride turbine rotor, which comprises sintering an injection-molded blade degreased body and a hydrostatic pressure-molded shaft degreased body and then sintering the same. A method for manufacturing a ceramic turbine rotor, characterized in that the relative density of the density difference between the blade portion and the shaft portion at each temperature is within 1%. 2. A method for manufacturing a silicon nitride turbine rotor in which an injection-molded blade degreased body and a hydrostatic pressure-molded shaft degreased body are fitted together and then sintered, in a silicon nitride matrix. By mixing the organic binder by injection molding and degreasing the mixture, the blade degreased body and the shaft degreased body obtained by degreasing the mixture obtained by the same kneading and then isostatic pressing are fitted, and the sintering is performed. A method for manufacturing a ceramic turbine rotor, comprising: 3. A method for manufacturing a silicon nitride turbine rotor in which an injection-molded blade degreased body and a hydrostatically pressure-molded shaft degreased body are fitted and then sintered, in which a silicon nitride matrix is kneaded. Hydrostatic pressure is applied by using a degreased blade portion obtained by mixing the organic binder with the above and injection-molding the mixture and degreasing it, and a silicon nitride material having the same oxygen content, metal content, particle size, and particle size distribution as the above mixture. A method for manufacturing a ceramic turbine rotor, comprising fitting the molded degreased shaft portion and performing the sintering.