JPH02213403A - Manufacture of sintered member - Google Patents

Abstract

PURPOSE:To obtain a heat resistant sintered member having excellent quality by heating surface of a presintered member to make this close and then, compacting this with high pressure isopropic heating. CONSTITUTION:The presintered material 1 manufactured with metal powder or ceramic powder is inserted into a vacuum chamber 2 and this surface is melted with irradiation of the electron beam 3 to form the close sintered body surface layer 4. After forming the close sintered body surface layer 4 on the whole surface of the presintered material 1, this is set into the HIP treating apparatus 5 and heated with a heater 6 and also compacted with isotropic gas pressure 7. By this method, even when the material having insufficient sintering ability is used, the sintered member having high density and high quality can be obtd. at a low cost. Then, as the metal powder, one or more kinds selected among W, Ta, Nb, Re and alloy powder containing them as the essential components, are used. Ceramic powder is selected among Al2O3, ZrO2, Y2O3, SiC, HfC, Si3N4, ZrN and TiN.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing heat-resistant sintered members such as high-melting point metals and ceramics.

(Prior Art) A sintering method is generally used to make a member using a material with a very high melting point, such as W, No, alloys thereof, and ceramics such as ZrO□, i, O, etc.

However, these high melting point materials generally have poor sinterability, requiring high temperature and long time for sintering, and it has been difficult to obtain a sintered member with a relative density close to the theoretical density.

In recent years, as a method to obtain high relative density at low sintering temperatures,
Attempts have been made to add powders of Ni, Cu, etc. with low melting points to these high melting point material powders.

In fact, according to this method, it is possible to easily obtain a sintered member having a high relative density, but the usable temperature is significantly lowered and the original properties of the material cannot be exhibited.

In addition, for materials such as cermet, high temperature isostatic pressing (HIP: t) is applied after sintering.
c.Press-ing) processing to achieve high density.

HIP processing is a process in which the object to be processed is placed in a pressure vessel with a built-in heater, and high-pressure gas is introduced into the container to heat and pressurize the object. Since the pores are crushed to increase the density, it is necessary to increase the density to some extent in advance in the preliminary sintering stage before the HIP treatment. In other words, when the density of the pre-sintered body is low, the pores in the sintered body become open pores that communicate with the outside world, and the gas that is the pressure source during HIP processing enters into these pores, causing the inside of the sintered body to become open. This is because the pressure inside the pores becomes equal to the gas pressure within the pressure vessel, making it impossible to crush the pores in the sintered body. Therefore, all the pores in the pre-sintered body need to be closed pores that do not communicate with the outside world, but since the high melting point metals and ceramics mentioned above have poor sintering properties, all the pores must be closed during the pre-sintering stage. It is impossible to make the pores closed. Conventionally, in order to densify such difficult-to-sinter materials by HIP processing, it has been necessary to perform an operation called "canning" in which the object to be processed is hermetically sealed and enclosed in a can (container) whose interior is evacuated.

That is, the can prevents gas from entering the workpiece, and the can is crushed by gas pressure, thereby molding the workpiece under heat and pressure.

The configuration of the can will be explained using FIG. Object to be processed 11
is covered with a barrier layer 13 to prevent it from reacting with the pressure medium 14 and the can 12, and then placed inside the can and heated (baked) to remove the air inside the can through the degassing pipe 15 with a vacuum pump. The air pipe is vacuum sealed by welding or the like and subjected to HIP treatment.

(Problems to be Solved by the Invention) In the above method, the can material has a melting point higher than the HIP treatment temperature and has sufficient ductility at high temperatures to withstand compressive deformation during the HIP treatment. There is a need. Glass and mild steel are generally used as materials that meet these requirements, but mild steel has a low melting point and cannot be used in the HIP treatment of the above-mentioned high melting point materials. Furthermore, if the HIP treatment temperature of glass is too high, the viscosity of the glass will decrease and the weight of the object to be treated will cause the glass to break and cause leakage. On the other hand, if the temperature is too low, the material will not soften and will be crushed by the gas pressure during the HIP process, so there is a problem that the temperature at which it can be used is very narrow.

The properties required for the pressure medium material and the barrier layer material are that they must not sinter even under high temperature and high pressure during HIP processing, as it is necessary to transmit the compressed gas pressure that acts from the outside of the can to the workpiece. is required. Also, Can,
Materials that cause the pressure medium, barrier layer, and workpiece to react with each other to form compounds with low melting points, or that cause embrittlement of the can or workpiece are unsuitable. However, currently 1
At present, there are almost no materials that completely satisfy these requirements at temperatures exceeding 500°C.

Furthermore, in addition to the technical problems mentioned above, this kind of canning work not only requires various equipment, but also
This requires an extremely large amount of time and cost. Moreover, by canning, the volume of the object to be processed becomes 5 to 20 times that before canning.

The HIP processing equipment used also needs to be quite large. Therefore, the conventional Canning HIP processing method is fully applicable when making lightweight, small parts in small quantities and without considering production costs, such as in the case of parts prototyping. It has been impossible to mass-produce treated products due to cost considerations. In addition, the HIP treatment temperature for high melting point metals and ceramics as mentioned above is usually 1
Since the temperature is 500°C or higher, the formation of a reaction product layer on the surface of the workpiece due to the reaction between the barrier layer or pressure medium and the workpiece cannot be avoided, and the reaction acid formed on the surface of the workpiece cannot be avoided. The properties of the object to be processed may deteriorate due to the material layer, or the object to be processed and the barrier layer may become fused, making it impossible to release the mold.

The present invention has been made to solve the above problems,
It is possible to increase the density of large and large quantities of materials with poor sinterability, such as high-melting point metals or ceramics, at low cost, and
It is an object of the present invention to provide a manufacturing method that allows high-quality sintered members to be obtained.

[Invention Φ configuration]

(Means for Solving Problem 8) The present invention eliminates pores near the surface by heating and densifying the surface of a temporarily sintered member manufactured by sintering high-melting point metal powder or ceramic powder, It is characterized in that this surface layer is given the role of the can, and all the pores remaining in the sintered member are converted into closed pores that do not communicate with the outside world, followed by HIP treatment.

(Function) Immediately after sintering, a large number of pores 10 remain in the pre-sintered member 1 as shown in FIG. 2(b), but the relative density at this stage is low and the remaining pores are Most of the stomata in the body are open pores that communicate with the outside world. Therefore, in order to eliminate pores in the pre-sintered member 1 and increase its density, H
Even if the IP treatment is performed, gas 9, which is the pressure medium during the HIP treatment, enters the pores in the pre-sintered member 1, and the pressure inside the pores in the pre-sintered body becomes equal to the gas pressure in the pressure vessel, causing the pre-sintering to take place. The pores IO in the aggregate cannot be crushed.

However, as shown in FIG. 2(a), the pores in the surface layer 4 of the sintered body can be eliminated by heating the surface of the temporary sintered body 1 to a temperature at which the material is sufficiently densified or melted. As a result, the pores 8 remaining in the pre-sintered body can be made into closed pores that do not communicate with the outside world. H in this state
When the IP treatment is performed, this sintered body surface layer 4 has a can effect, so that the gas 9 in the pressure vessel enters into the pores 8 in the temporary sintered body, with the dense sintered body surface layer 4 serving as a barrier. Therefore, the pre-sintered member 1 is pressurized and heated by the gas pressure in the pressure vessel, and the pores 8 in the sintered body are crushed, making it possible to obtain a high-density sintered member.

In addition, this method not only eliminates the need for expensive canning operations, but also eliminates the need for barrier layers or pressure media, which are essential for canning, so there are concerns about reactions between the pre-sintered body and these materials. No need (no deterioration in the quality of the sintered body).

(Example) Hereinafter, an example of a sintered member according to the present invention will be described with reference to FIG.

First, as shown in FIG. 1(a), a tungsten pre-sintered material 1 sintered in a hydrogen furnace such as Shimezu was used. The relative density of the tungsten pre-sintered material 1 at this stage varies depending on the particle size of the tungsten powder used, the sintering temperature, etc., but is approximately 85 to 90% for large tungsten members. After placing the tungsten pre-sintered material 1 in a vacuum chamber 2 and creating a high vacuum, an electron beam 3 is applied to the surface of the tungsten pre-sintered material 1 to melt it, thereby forming a dense sintered body surface layer 4. ((b) in the same figure) After forming a dense sintered body surface layer 4 on the entire surface of the pre-sintered tungsten material ((c) in the same figure), it is set in the HIP processing device 5. Then, it is heated by a heater 6 and is heated and pressurized by an isotropic gas pressure cuff.

((d) in the same figure). At this time, if the thickness of the dense layer 4 formed on the surface of the tungsten pre-sintered material is made too thick, cracks will occur within the layer, so it is desirable to keep it as thin as possible. In this embodiment, the output of the electron beam is adjusted, The thickness of this dense layer is 500 to 700. I made it so that In addition, the atmosphere for forming a dense surface layer on the surface of the pre-sintered material may include metals such as tungsten and molybdenum, and 5iCt 5IGN4.
Ceramics such as ZrO, Al1,
0. When heating oxide ceramics in a vacuum, # elements dissociate, so it is preferable to conduct the heating in the atmosphere.
On the other hand, the method depends on the heating atmosphere, but when heating in vacuum or inert gas, high frequency heating, electrical heating, and electron beam heating are suitable.
Laser heating is used when heating in the atmosphere.

Burner heating and electric furnace heating are suitable.

As shown in Fig. 2 Ca), a dense sintered body surface layer 4 formed by heating the surface of the tungsten pre-sintered material 1 by this method is formed by pre-sintering of the high-pressure gas 9 during HIP treatment. Since it acts as a barrier against intrusion into the pores 8 inside the material, the same effect as canning and HIP treatment can be obtained. Therefore, the tungsten pre-sintered material 1 is
It is heated and press-formed through processing, and can produce a high-density sintered tungsten material. Furthermore, unlike the conventional Canning HIP process, this method does not require a barrier layer or pressure medium, so there is no need to worry about the reaction between the barrier layer or pressure medium and the tungsten sintered material, and the resulting tungsten sintered material The quality is also excellent.

A dense surface layer was formed on the surface of the sintered tungsten material using this method, and the relative density of tungsten (specimen A) was HIPed at various temperatures. (Test piece B) and a case of HIP treatment without canning (Test piece C) are shown in FIG. 3 in comparison. The figure shows that the relative density of the tungsten sintered material used in this example was about 91%.
The relative density of specimen A) was approximately 98.0-99.8%, depending on the HIP treatment temperature. Moreover, the relative density of tungsten (test piece B) obtained by canning and HIPing a tungsten sintered material having the same relative density of about 91% in the conventional manner was about 96.7 to 99.2%. The reason why the relative density of the tungsten produced according to the present invention (specimen A) is higher than that of the tungsten produced by conventional canning and HIP treatment (specimen B) is that the barrier layer and pressure medium inside the can are damaged during the HIP treatment process. This is because a large amount of gas is released, which lowers the degree of vacuum inside the can. On the other hand, it can be seen that the relative density of as-sintered tungsten subjected to ZHIP treatment (specimen C) hardly changes.

Figure 4 shows tungsten (test piece A) manufactured according to the present invention.
) and conventionally canned tungsten (test piece B) subjected to HIP treatment at 2000° C. The bending strength of the surface and center portions is shown. From the same figure, there is almost no difference in the bending strength of the tungsten manufactured according to the present invention (test piece A) between the center and the surface, but the bending strength of the surface of the canned tungsten (test piece B) is the same at the center. It can be seen that it is only about 1/4 to 175 of that.

This is because the barrier layer (boron nitride in this example) and tungsten reacted to form brittle tungsten nitride and tungsten boride on the tungsten surface.

〔Effect of the invention〕

According to the present invention, even materials with poor sinterability such as high-melting point metals and ceramics can be densified at low cost.
A method for manufacturing a heat-resistant sintered member with excellent quality can be provided.

[Brief explanation of the drawing]

FIGS. 1(a) to (d) are process diagrams showing an example of the method for manufacturing a sintered member according to the present invention, and FIG. 2(a) is a surface of a sintered body obtained according to the present invention before HIP treatment. Schematic cross-sectional diagram of
Fig. 2(b) is a schematic cross-sectional view immediately after pre-sintering, Fig. 3 is a characteristic diagram showing the change in relative density after HIP treatment between the present invention and the conventional example, and Fig. 4 is the present invention and the conventional example. Figure 5 shows the bending test results showing the uniformity after HIP treatment with conventional HI
FIG. 3 is a schematic cross-sectional view showing the configuration of a can used in P processing. 1...Tungsten pre-sintered body 2...Empty chamber 3...Electron beam 4...Dense layer formed on the surface of the sintered body 5...HIP
Processing equipment 6...Heater 7...Gas pressure
8...Closed pore 9...High pressure gas
10...Open pores (α) <b) Figures 1 to 9

Claims (3)

[Claims] (1) A pre-sintered body is produced using metal powder or ceramic powder, and then a high-density layer is formed on the surface of the pre-sintered body by heating the surface of the pre-sintered body, and then a high-pressure isostatic layer is formed on the surface of the pre-sintered body. A method for manufacturing a sintered member, characterized by molding by heating. (2) The metal powders include W, Ta, Mo, Nb, and R.
2. The method for manufacturing a sintered member according to claim 1, wherein the sintered member is made of at least one selected from e and alloy powders containing these as main components. (3) As the ceramic powder, Al_2O_3,
ZrO_2, Y_2O_3, SiC, TaC, HfC,
Claim 1, characterized in that the material is made of at least one selected from Si_3N_4, ZrN, and TiN.
A method of manufacturing the described sintered member.