JPH0657843B2 - Manufacturing method of sintered machine parts - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a mechanical component for sintering a metal powder, a ceramic powder, or a composite powder of these, and more specifically, using these powders for hot working. The present invention relates to an improvement in a method for producing a sintered machine part having a high density and a high dimensional accuracy by sintering while pressurizing with an isotropic press.

(Prior Art) A metal part, a ceramic powder, or a composite powder of these (hereinafter, these powders are referred to as raw material powder) is sintered to sinter a mechanical part. Since it is customary not to pressurize during sintering, the strength and reliability of the obtained sintered body were insufficient.

In order to improve this, a hot isostatic press is partially used to sinter the three-dimensional shaped body while applying isotropic pressure. However, this method is not yet technically well established, and in particular, the following problems remain. That is, it is difficult to preliminarily mold the raw material powder into a desired shape and then seal the fragile molded body in a container having good adhesion without damaging it. Further, there is a problem that it is difficult to obtain a material for the sealed container having appropriate deformation characteristics and stability at a required sintering temperature of the molded body.

On the other hand, a method of encapsulating these raw material powders in a thin metal tube or a glass tube, or a method of forming the raw material powders in advance and applying the glass powders thereon has been proposed, but each method has advantages and disadvantages. Therefore, the above problems have not been sufficiently solved.

The applicant has applied a slurry of refractory powder and silicate compound powder to a model made of a removable material to form a shell by a method similar to the known shell mold method, and then removes the model. After making a female mold, pouring a slurry of the desired raw material powder into it and solidifying and drying it, heating the female mold shell to a temperature below the sintering temperature to melt the silicate compound in the shell layer and thereby create pores. To make Ciel a sealed body,
We proposed a method of pressurizing this in a hot isostatic press to sinter the internal compact while applying isotropic pressure through the silicate compound layer in the molten state (Japanese Patent Application No. 57-16835).
No. 58-136702).

(Problems to be Solved by the Invention) According to this method, it becomes easy to seal in the above-mentioned container having good adhesion and to manufacture the container from a container material having an appropriate deformation characteristic, and the above-mentioned problems are solved. Can be resolved,
As a result of making the shell with a refractory and a silicate compound that melts below the sintering temperature, the shell may not be sufficiently airtight below the sintering temperature, or the molded body and the shell may react at the sintering temperature, etc. It turned out that there was a problem.

The present invention aims to provide a method for solving the above problems.

(Means for Solving the Problem) In order to achieve the above-mentioned object, the present invention mainly has a three-layer structure of a female shell for filling raw material powder, which comprises metal powder, ceramics. In the method for producing a sintered machine part by hot isostatic pressing using powder or metal / ceramic composite powder or powder mixed with ceramic fiber as raw material powder, the first step is a sintered machine part having a desired shape. Melt the model of
A step of manufacturing using a material that is easily melted or vaporized, (second step) a step of sequentially forming the following three types of coating layers on the model to form a shell, (a) a first refractory powder A layer, (b) a second layer made of a mixture of refractory powder and a glassy powder having a high viscosity which softens at a temperature lower than the sintering temperature, and (c) a softening and melting at a temperature lower than the sintering temperature and a viscosity Third layer made of high glassy powder, (third step) the model in the shell is dissolved or melted in a solvent, or vaporized and removed to make a female mold having the same cavity as the model in the shell Step (4th step) Mixing desired raw material powder with the dispersion to prepare a slip, (5th step) Pouring the raw material powder slip into the cavity of the female shell to remove the dispersion. A step of filling the cavity with raw material powder, ) After closing the slip injection port of the female shell and drying the shell, the shell is heated to a temperature equal to or lower than the sintering temperature to soften the silicon salt compound powder of the second layer of the shell and glass the third layer. A step of softening and melting to seal the pores and hermetically seal the female die. (Seventh step) The female die is pressed and heated to the sintering temperature in a hot isostatic press to heat the female shell molded body. And (8) a method of manufacturing a sintered machine part, which comprises a step of removing a female die and taking out a sintered body.

(Operation) According to the above configuration, the shell is made of a mixture of the first layer made of refractory powder, the second layer made of refractory powder and glassy powder having a high viscosity and being softened at a temperature equal to or lower than the sintering temperature. Become third
The layer has a three-layer structure consisting of vitreous powder that softens and melts at a temperature below the sintering temperature and has a high viscosity, and the three-layer shell has a different composition ratio of refractory powder and vitreous powder. , The layers are easy to fit in and can be made into an integral shell. The third layer can completely seal the shell before hot isostatic pressing sintering, and the second layer of the intermediate layer has an appropriate softening property depending on hot isostatic pressing conditions. , Can impart pressure transfer characteristics and stability to the shell material, and the first layer is
Since the refractory powder alone is used, the shell is easily separated from the surface of the sintered body. Therefore, the sintered body obtained by heating and sintering by hot isostatic pressing is highly reliable and excellent in quality.

Next, the method of the present invention will be described with reference to the flow sheet shown in the accompanying drawings.

(First step, production of model) A model of a desired mechanical component is produced. Since this model needs to be removed after forming a female shell as described later, it is easily dissolved in a solvent that does not attack the shell material, or easily dissolved at a temperature lower than the temperature at which the shell material softens and deforms. It is necessary to make it from a material that can be discharged and then burned, or burned and vaporized. As a material satisfying such conditions, a low melting point wax, a wax soluble in water or an organic solvent, or a low melting point alloy is used.

The model may be manufactured by melting a desired material and casting it in a mold, or by a known method such as injection molding or machining. It is necessary to make the model size larger than the final product size by taking into account the shrinkage of the compact by the hot isostatic pressing which will be performed later.

(Second Step, Formation of Female Shell) One of the important constitutions of the present invention is to form a triple-structure shell by sequentially forming three types of coating layers on the model.

(A) Formation of first layer: shell The first layer is a layer that is in direct contact with the molded body, and serves as a release agent when separating the female mold and the sintered body after sintering. Therefore, the powder forming the first layer does not react with the raw material powder forming the molded body at the sintering temperature,
In addition, it is necessary that the refractory material does not form a low melting point compound with the softening material contained in the second layer and the third layer, does not cause eutectic, and is stable and hardly sintered. Is.

If the first layer is formed of such refractory powder, it is possible to avoid direct contact between the second layer and the compact or the sintered body at a later stage of pressure sintering, and the surface of the sintered body is damaged. In addition to being prevented from being deteriorated or deteriorated, it becomes easy to separate the sintered body from the female mold.

As a refractory powder satisfying such conditions, carbon, mica, pyroferrite, or silica, zirconia, alumina, magnesia, yttria, depending on the type of raw material powder,
Many refractory powders such as heat-resistant oxides such as titania, mullite, zircon or spinel, heat-resistant nitrides such as aluminum nitride, boron nitride and silicon nitride, and heat-resistant carbides such as silicon carbide can be used.

Particularly when the product sintered body is required to have a high degree of dimensional accuracy, the pressing force from the outside is sufficiently transmitted to the compact in the sintering stage of the present invention, and the sintering shrinkage is sufficiently followed to cause deformation. In addition, it is necessary that it be easily removed from the surface after sintering.In such a case, the crystal structure of the above refractory materials is a layered structure, and a property that easily causes shear deformation is required. It is desirable to have one.

Such refractory powders include carbon, mica, and pyrophyllite, among them reactivity with the desired raw material powder,
The optimum refractory powder is used by selecting it in consideration of the stability at the sintering temperature and the reactivity with the coating second layer material.

Refractory powder satisfying the above conditions is mixed with a dispersion liquid of water, ethanol or the like to form a slurry and then coated on a model to form a shell first layer. In order to increase the strength of the coating layer after coating in this slurry, it is necessary to mix a polymeric binder such as polyvinyl alcohol, phenol, or silicon, or an inorganic binder such as cement, aluminum phosphate, or colloidal silica. There is. The binder is completely removed by the stage of pressure sintering of the compact in the hot isostatic press, or even if it remains in the shell first layer, it does not react with the compact. It is desirable that it be converted to a refractory material that does not cause it.

Further, it is necessary that the shell first layer after coating and drying has a porosity of 10 to 70%. If this exceeds 70%, the strength of the shell will decrease and it will be easily damaged.
% Or less, it is difficult to leach the dispersing liquid during pouring of the raw material powder slip, which is not preferable.

(B) Formation of the second layer: the second shell is formed outside the first shell layer.
Form the layers. The powder to be used for this is a material whose first component is refractory powder that does not melt or soften at the sintering temperature when the compact is subsequently sintered in a hot isostatic press, and which melts or softens at this temperature. Is mixed as a second component, and the latter is mixed in an amount of 15 to 90% by volume. This shell second layer plays an important role in transmitting the isotropic pressure onto the compact when it is pressurized and heated in the hot isostatic press, so that it is sufficient at the desired sintering temperature. It is necessary to cause isotropic viscoelastic-plastic deformation, and it is necessary not to have such a low viscosity that it penetrates the inner first layer and penetrates into the molded body.

It is important to determine the types of the refractory powder of the first component and the softening material powder of the second component according to the pressure and heating conditions of the hot isostatic press so as to satisfy such conditions. Especially for the mixing ratio of these two components, it is important to set the softening material to 15 to 90% for the above reason.

The above refractory powder is carbon, or silica, zirconia, alumina, magnesia, yttria, titania,
A heat-resistant oxide such as mullite, zircon, or spinel, a heat-resistant nitride such as aluminum nitride, boron nitride, or silicon nitride, a heat-resistant carbide such as silicon carbide, or the like is selected depending on conditions. As the softening material, a vitreous material having a high viscosity even when melted is desirable, and is selected from materials based on silica, aminosilicate compounds and borosilicate compounds according to the conditions.

The method of forming the shell second layer is performed by applying the slurry dispersion liquid as in the case of the first layer. In particular, when the second layer is made to have a certain thickness, it is desirable that the second layer is not applied to the desired thickness at one time but repeatedly applied several times to obtain the desired thickness.

It is necessary that the dispersion of the molding powder of the shell second layer does not redissolve the binder of the shell first layer that has already been formed and damage the first layer. Further, the shell second layer has a porosity of 10 to 10 after drying for the same reason as in the case of the first layer.
70%.

(C) Formation of third layer of shell: The role of the third layer is to completely seal the shell before pressurizing and heating with a hot isostatic press, so that the temperature is lower than the sintering temperature of the compact. A third layer is formed on the second layer using powder of a material that is melted and softened by. In this way, the shell having a three-layer structure in which the raw material powder slurry is poured is preheated in a vacuum at a temperature lower than the desired sintering temperature or under a sufficiently low inert gas atmosphere pressure to melt or melt the third layer. By softening and air-tightening, it becomes possible to perform pressure sintering without gas invading the shell in the subsequent hot isostatic pressing.

As such a melt-softening material, a softening material similar to the softening material used as the second component of the second layer can be used. In particular, a material having a high viscosity in a molten state is desirable, and therefore a silicate compound is used as a base. It is recommended to select from among the glassy materials to be used.

The formation of the third layer is carried out by applying a slurry-like dispersion liquid as in the case of the first and second layers. The third layer also has a porosity of 10 to 70% after drying for the same reason as the first and second layers.

(Third step, removal of model) The model in the female shell is melted, dissolved in a solvent, or burned and vaporized to be removed, and a cavity having the same shape as the model is made in the female shell. When it is dissolved in a solvent and removed, it is dried sufficiently.

(Fourth step, preparation of raw material powder slip) A desired raw material powder is prepared and mixed with the dispersion liquid to form a slip. When the raw material powder is a metal, the average particle diameter is several tens of μm to 100 μm, and spherical particles obtained by the atomizing method, the rotating electrode method or the like are preferable from the viewpoint of moldability. In the case of ceramic powder, the average particle size is at most 10 μm, and preferably 1 μm or less in order to obtain a high-density and high-strength sintered body,
From the viewpoint of moldability, it is desirable that the particles are spherical particles as much as possible.

Further, in the case of ceramics such as silicon nitride or silicon carbide whose sinterability is insufficient by itself, a sintering accelerator may be added. As the sintering accelerator, for example, in the case of silicon nitride, Al may be added.
₂ O ₃ , AlN, Y ₂ O ₃ , MgO, CeO _{2 and the} like are suitable, and in the case of silicon carbide, a combination of B, Al and C is suitable.

In addition to the above, a cermet such as WC-Co or TiN-Ni or a dispersion-strengthening alloy in which a ceramic powder such as Y ₂ O ₃ is dispersed in a metal such as an Ni alloy or fibers such as C, B or SiC are Al. It is also possible to use a raw material powder of a fiber reinforced alloy dispersed in a metal such as Ti, Ti or the like. Similarly, a composite material powder in which other ceramic particles such as ZrO ₂ or fibers such as SiC are dispersed in a ceramic such as Si ₃ N ₄ can also be used as the raw material powder.

It is generally desirable to use water as a dispersion liquid for slipping these raw material powders, but when a chemical reaction occurs with the raw material powder or when they are aggregated, ethanol, propanol or other organic materials is used. It is better to use a solvent. If necessary, a peptizer is added or pH is adjusted to stabilize the slip.

(Fifth Step, Pouring of Raw Material Powder Slip) The raw material powder slip prepared as described above is poured into the female shell having the cavity of the required shape. At this time, it is desirable to keep the female mold in the powder-packed bed in order to retain the thin-walled female mold shell and absorb the dispersion liquid leaching from the female mold. In this way, the slip dispersion liquid poured into the female mold is leached through the pores of the shell and absorbed by the surrounding powder-packed bed, facilitating the leaching.

(Sixth step, airtight sealing of female shell) The slip was poured and left for a while, and when the dispersion liquid stopped leaching, the shell inlet was used to form the second and third layers. Close with, and remove the female mold from the powder packed bed and air dry or slowly heat to dry. If necessary, heat at low temperature to remove mixed organic binder.

The female shell filled with the raw material powder in the cavity is heated to a temperature not lower than the melting point or softening point of the softening material forming the third layer (outer layer) and not higher than the sintering temperature of the compact, and the pores of the third layer To seal the female mold. It is desirable to perform this heating in a vacuum, but unless the gas remaining in the shell exerts an adverse effect on the subsequent pressure sintering by a hot isostatic press, the pressure is sufficiently lower than the sintering pressure. You may perform in an inert gas atmosphere. If the material of the molded body or female shell contains an organic binder or water, it should be heated to a temperature lower than the temperature at which the third layer of the shell becomes airtight, and then removed to make it airtight. It is important to heat to temperature.

(Seventh Step, Hot Isostatic Pressing) Following the above steps, an airtight female die containing a compact is placed in the hot isostatic pressing machine under the desired sintering temperature and pressure. . Ciel second
The softening material of the second component of the layer melts or softens, the mixed layer of this and refractory powder undergoes appropriate viscoelastic-plastic deformation, and the compact in the shell is pressure-sintered under isotropic pressure. A sintered body with high density is obtained.

(Eighth step, removal of female shell) Next, the female shell is cooled. In addition to mechanical methods such as vibration and sandblasting, the shells can be removed by chemical methods such as treatment with an alkaline solution in an autoclave.

Since the melted and solidified second layer and the first layer between the third layer and the sintered body serve as a release agent, the shell can be easily removed and the surface of the sintered body is damaged. It is possible to obtain a good and high quality product sintered body that is free from deterioration.

Next, examples will be described.

(Example 1) Using a wax having a melting point of about 70 ° C, a male model of a turbocharger impeller was manufactured by injection molding. Boron nitride powder is dispersed in water, slips with colloidal silica added as a binder are applied on a model, dried and solidified to form a shell first layer, and then 55% by volume of silicon carbide powder as refractory powder,
As a softening material, a powder mixed with 45% by volume of borosilicate glass powder is applied on the shell first layer by the same method and dried to form a shell second layer, and the softening material boron is further formed thereon. Only silicate glass powder was applied in the same manner and dried to form a shell third layer.

A male model with a three-layer shell is heated in an autoclave to 120 ° C, the model in the shell is melted and flown away, and heated to 500 ° C to incinerate the remaining wax, A female shell having a porosity of about 50% was used for all three layers.

6% by weight of silicon nitride powder with an average particle size of 0.7 μm as raw material powder
Aluminum nitride powder was added, mixed with a dispersion liquid containing ethanol as the main component, treated with a ball mill to make a slip, and poured into a female shell held in a bed filled with silica sand to leach the dispersion liquid, and the cavity of the female shell was cavitated. The raw material powder was filled inside. Next, the slurry for each layer of the shell was sequentially applied to the inlet of the female shell and dried to seal the inlet.

This was thoroughly dried, further heated to 500 ° C. in a dry air stream, then placed in a hot isostatic press, and heated to 1500 ° C. in a vacuum atmosphere. At this temperature, the shell borosilicate glass of the third layer was melted and the female mold was completely hermetically sealed. After that, the pressure in the press was raised to 1750 ° C. while being pressurized to 2000 atm with argon gas. The borosilicate glass in the shell second layer is melted, and the molded body inside the female shell is sintered while being pressed under isotropic pressure by viscoelastic-plastic deformation of the mixed layer of this and the solid silicon carbide powder. It was

After the completion of sintering, the mixture was cooled, the shell was removed, and the sintered body was taken out. The shell boron nitride powder layer of the first layer did not react with the silicon nitride sintered body at all, and the penetration of the molten borosilicate glass of the second layer into the first layer was slight, and the first layer itself was also sintered. Since it was not present, the shell was easily removed, and the surface of the sintered body was neither denatured nor damaged. It was confirmed that the sintered body was sintered to a theoretical density and the dimensional accuracy was high.

For comparison, each of the following shells was formed on the same model as in the above example, and then the same batch of silicon nitride powder slip was poured into the cavity from which the model was removed in the same manner as described above, the injection port was sealed, and isotropic pressure was applied. After heating to 1500 ° C. in the press, it was pressurized to 2000 atm at 1750 ° C. to perform hot isostatic pressing. (% Is volume%) Comparative example 1: Only the second layer (silicon carbide powder 55%, borosilicate glass powder 45%) is formed, comparative example 2: second layer (same as comparative example 1), third layer (Borosilicate glass powder) formed, first layer not formed, Comparative Example 3: First layer (boron nitride powder), second layer (same as Comparative Example 1) formed, third layer not formed, Comparative Example 4 : First layer (same as Comparative Example 3), third layer (same as Comparative Example 2) formed, second layer not formed, Comparative Example 5: first layer (same as Comparative Example 3), second layer ( Silicon carbide powder 90%, borosilicate glass powder 10%), third layer (same as Comparative Example 2) formed, Comparative Example 6: first layer (same as Comparative Example 3), second layer (silicon carbide powder 5%) , Borosilicate glass powder 95%), third layer (Comparative Example 2)
Same).

The inspection results of the sintered body and the shell for each of the comparative examples were as follows. Comparative Examples 1 and 2: Reaction occurred between the silicon nitride sintered body and the shell, and the shell was not easily removed, Moreover, the surface of the sintered body was altered.

Comparative Examples 1 and 3: Since the shell was not completely hermetically sealed, high-pressure gas penetrated into the shell, pressurization was not performed well, and the density of the sintered body was insufficient.

Comparative Examples 4 and 6: Due to the low viscosity of the molten borosilicate glass, the molten borosilicate glass reached the surface of the sintered body through the boron nitride powder layer, some reaction with the sintered body was observed, and the shell was not easily removed.

Comparative Example 5: The softening deformation of the second layer as the isotropic pressure transmission layer was insufficient, and deformation was observed in the sintered body.

From the results of the above Examples and Comparative Examples, according to the method of using the female shell of the three-layer structure of the present invention, it is possible to obtain a sintered body with high density and high quality, high dimensional accuracy, and excellent surface condition. It became clear that you can do it.

(Example 2) A water-soluble soluble wax was injection-molded to fabricate a static blade male model of a small gas turbine, and a slurry containing colloidal graphite and an organic binder was applied and dried, and then boron nitride was used. A slurry in which powder and colloidal silica as a binder were dispersed was applied and dried to form a shell first layer. A slurry in which 55% by weight of boron nitride powder as a refractory powder and 45% by weight of mullite powder as a softening material and alumina cement as a binder are dispersed is applied onto this to form a second shell layer. A dispersion liquid slurry of silica powder as a softening material and colloidal silica as a binder was applied to the above to form a shell third layer. After the shell is dried and solidified, it is immersed in water to dissolve and remove the soluble wax model inside the shell, and then dried to
A female shell having a porosity of approximately 45% was obtained in the third layer.

Next, powders each containing 1% by weight of boron carbide and carbon in silicon carbide were used as raw material powders, and the powders were dispersed in a dispersion liquid containing water as a main component to form a slip, and the female shell was placed in zircon sand. It was held and poured, and the dispersed liquid was leached through the shell wall to fill the raw material powder into the female cavity.

Then, the slip inlet was sealed with the slurry for the shell 1st to 3rd layers, dried sufficiently, further heated to 600 ° C. in a nitrogen stream and then placed in a hot isostatic press at 1 atm. Heated to 1800 ° C. in argon gas.
At this temperature, the silica powder of the shell 3rd layer was melted and the pores of the shell were sealed and completely sealed.

Subsequently, the pressure of argon gas in the press was raised to 1500 atm and the temperature was raised to 2150 ° C. to melt the mullite in the shell second layer. The shell second layer in the mixed state of the boron nitride powder and the mullite in the molten state was appropriately viscoelastically deformed, and the internal silicon carbide compact was sintered while being subjected to isotropic pressure.

When the shell and the sintered body were separated by cooling after the completion of sintering, the graphite / boron nitride layer of the shell first layer could be easily removed from the surface of the sintered body, and the surface was not altered at all. It was confirmed that the sintered body itself had a theoretical density and high dimensional accuracy.

(Example 3) A male model having a jet engine blade shape is manufactured by injection-molding wax, and a slurry in which spinel powder and colloidal silica as a binder are dispersed is applied to form a shell first layer. Similarly, a slurry of powder obtained by mixing zircon powder and Pyrex glass in an equivalent amount was applied thereon to form a shell second layer, and further a slurry of soft glass powder was applied thereon to form a shell third layer. .

After this is dried and solidified, the model wax in the shell cavity is melted and removed in an autoclave.
A female shell having a porosity of 45% was obtained in the third layer. Nickel alloy IN100 with an average particle size of 100 μm as raw material powder
(Ni-14Co-9Cr-5.5Al-4.7Ti-3M
The slips obtained by dispersing the spherical powder of o) in a propanol solution were poured into the female shell cavity described above, and the dispersed liquid was leached to fill the raw material powder into the cavity. Thereafter, female slip inlets were sequentially coated with the slurries for the first to third layers in the same manner as described above, hermetically sealed, sufficiently dried, and then placed in a hot isostatic press, and vacuumed at 800 ℃
Heated to. At this temperature, the soft glass of the shell third layer was melted and the pores were sealed and completely sealed.

Then, the pressure was raised to 1200 ° C. while applying a pressure of 1500 atm with argon gas, and the Pyrex glass of the shell second layer was melted. The compact in the female shell was sintered while being subjected to isotropic pressure due to appropriate viscoelastic deformation of the mixed layer of zircon powder and molten Pyrex glass.

After the completion of sintering, it was cooled, and the shell and the sintered body were separated and inspected. As a result, the spinel powder layer of the shell first layer did not react with the surface of the sintered body, and itself was almost sintered. Since it was not present, it could be easily removed, and no alteration or damage was observed on the surface of the sintered body. It was also confirmed that the sintered body itself had good density, surface quality, and dimensional accuracy.

(Embodiment 4) A male model of a gas turbine blade shape was manufactured by using a soluble wax, on which a first layer was a spinel powder layer, a second layer was a refractory material containing 55% by volume of alumina, and a softening material containing boron. A mixed powder layer with 45% silicate glass, and a third layer are soda lime glass powder layers, each of which is applied as a dispersion liquid to the model in the same manner as above to form shells, and then the model wax is dissolved in water to be removed and dried. Then, a female shell having a porosity of about 40% was obtained for each layer.

Oxide dispersion strengthening alloy MA753 (Ni-2
Using powder of _{0Cr-2.3Ti-1.5Al-1.3Y 2} O 3 , etc.), a slip dispersed in ethanol solution is poured into the female mold, the raw powder was filled in a cavity, then the slip inlet first The slurry for the 1st to 3rd layers was used and sealed in the same manner as above. After sufficiently drying this, it was placed in a hot isostatic press and heated to 850 ° C. in vacuum to melt the third layer of the shell and seal the pores to make it airtight. The borosilicate glass in the shell second layer is melted by heating to ℃, and isotropic pressure is applied to the compact in the female shell by viscoelastic-plastic deformation of the mixed layer of alumina powder and molten borosilicate glass. Sintered while applied.

Although the shell and the sintered body were separated after cooling, the shell could be easily removed, and a gas turbine blade of oxide dispersion strengthened alloy sintered body of high quality, high density and high dimensional accuracy could be obtained. .

(Embodiment 5) A turbine disk model is made of soluble wax, and a shell having a three-layer structure of a first layer yttria, a second layer zirconia and Pyrex glass, and a third layer low melting point glass is formed in the same manner as above. After that, the wax was dissolved in water to produce a female mold having a model-shaped cavity. The mold was filled by pouring a slurry prepared by mixing a mixture of spherical powder of Ti-6Al-4V alloy having an average particle size of 150 μm with 20 vol% of silicon nitride whiskers in ethanol, and filling the inlets with the first to third holes. The materials for the layers are sequentially applied, sealed, sufficiently dried, and then placed in a hot isostatic press, heated to 800 ° C. in a vacuum to melt the low melting glass of the shell third layer and seal the pores. The female mold was made airtight, then heated to 1200 ° C. while being pressurized to 2000 atm with argon gas, and sintered while applying isostatic pressure to the molded body in the female mold.

After the completion of sintering, it was cooled, and the shell and the sintered body were separated and inspected, but the yttria powder of the shell first layer did not react with the sintered body at all and had a good surface without chemical polishing. A sintered body made of the material could be obtained.

Although the above examples show the silicon nitride ceramics, the silicon carbide ceramics, the nickel alloy, the nickel base oxide dispersion strengthened alloy, and the titanium / silicon nitride whisker fiber reinforced metal, the present invention is limited to these materials. It will be easily understood that the present invention can be applied to other ceramics, metals and / ceramics composite materials as well.

(Effects of the Invention) According to the present invention, a shell having a three-layer structure is formed on a removable model, the model is removed to produce a female mold having a model-shaped cavity, and a slip of desired raw material powder is poured into the mold. It is a method of filling a cavity, sealing the pores of the shell third layer to make it airtight, and then heating and sintering to the sintering temperature while applying pressure in a hot isostatic press. The sintered body can be manufactured with high productivity, and it is not necessary to directly handle the fragile raw material powder compact.

Further, since the layer made of only the softening material is formed on the outer layer of the female shell, the shell can be completely hermetically sealed before hot isostatic pressing and sintering. The female shell has a three-layer structure,
Since the intermediate layer is a mixed layer of the refractory powder solid and the softening material melt at the sintering temperature, the shell material should have appropriate softening characteristics, pressure transfer characteristics and stability according to the desired hot isostatic pressing conditions. Can be given to. Since a layer of releasable refractory powder is formed on the first layer of the female shell, that is, the inner layer, the shell is easily separated from the surface of the sintered body after sintering, and the surface of the product is not damaged or altered.

Alternatively, since pressure sintering is performed by hot isostatic pressing, a highly reliable and excellent quality sintered body can be obtained, and the practical effects of the present invention are extremely large.

[Brief description of drawings]

 The accompanying drawings are flow sheets illustrating the method of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenji Matsuda, Kenji Matsuda, 3-1-1-15 Toyosu, Koto-ku, Tokyo Ishikawajima Harima Heavy Industries Ltd. Technical Research Institute (56) Reference Japanese Patent Laid-Open No. 58-136702 (JP, A) Kaisho 57-126903 (JP, A)

Claims (10)

[Claims] 1. A method for producing a sintered machine part by hot isostatic pressing using metal powder, ceramic powder, metal-ceramic composite powder, or powder obtained by mixing ceramic powder as a raw material powder, the method comprising: ) Melting a model of a sintered machine part with the desired shape,
A step of manufacturing using a material that is easily melted or vaporized, (second step) a step of sequentially forming the following three types of coating layers on the model to form a shell, (a) a first refractory powder A layer, (b) a second layer made of a mixture of refractory powder and a glassy powder having a high viscosity which softens at a temperature lower than the sintering temperature, and (c) a softening and melting at a temperature lower than the sintering temperature and a viscosity Third layer made of high glassy powder, (third step) the model in the shell is dissolved or melted in a solvent, or vaporized and removed to make a female mold having the same cavity as the model in the shell Step (4th step) Mixing desired raw material powder with the dispersion to prepare a slip, (5th step) Pouring the raw material powder slip into the cavity of the female shell to remove the dispersion. A step of filling the cavity with raw material powder, ) After closing the slip injection port of the female shell and drying the shell, the shell is heated to a temperature equal to or lower than the sintering temperature to soften the silicon salt compound powder of the second layer of the shell and glass the third layer. A step of softening and melting to seal the pores and hermetically seal the female die. (Seventh step) The female die is pressed and heated to the sintering temperature in a hot isostatic press to heat the female shell molded body. And (8) a method of manufacturing a sintered machine part, which comprises a step of removing a female die and taking out a sintered body. 2. The method for producing a sintered machine component according to claim 1, wherein the raw material powder is a metal whose main component is any one of aluminum, titanium, cobalt and iron. 3. The method for producing a sintered machine part according to claim 1, wherein the raw material powder is a ceramic containing at least one of silicon nitride, silicon carbide, alumina and zirconia as a main component. 4. The raw material powder is a composite material containing any one of aluminum, titanium, nickel, cobalt or iron as a main component, and a ceramic powder or ceramic fiber dispersed and strengthened. A method for manufacturing a sintered machine part as described. 5. The first female shell layer comprises carbon, boron nitride, aluminum nitride, silicon nitride, mica, pyroferrite,
The method for producing a sintered machine component according to claim 1, which is one of silica, zirconia, alumina, magnesia, yttria, titania, mullite, zircon, or spinel. 6. The refractory powder of the second layer of the female shell is carbon, silicon carbide, aluminum nitride, silicon nitride, boron nitride, silica, zirconia, alumina, magnesia, yttria,
The method for producing a sintered mechanical component according to claim 1, wherein the sintered mechanical component is any one of titania, mullite, zircon, and spinel. 7. The production of a sintered machine part according to claim 1, wherein the vitreous powder of the second layer of the female shell is any of silicate glass, borosilicate glass and aluminosilicate glass. Method. 8. A sintered machine part according to claim 1, wherein the vitreous powder of the third layer of the female shell is any of silicate glass, borosilicate glass and aluminosilicate glass. Method. 9. The method for forming a coating layer for a female shell is a method in which desired powder is dispersed in a liquid to form a slurry, and the slurry is successively applied on a model or spray-coated. A method for manufacturing a sintered machine part according to the item. 10. The method for producing a sintered machine part according to claim 1, wherein the method for closing the injection port of the female shell is a method for forming the same three-layer structure by using the same material as the shell.