KR100302232B1 - Production process of titanium-aluminum intermetallic compound parts by powder injection molding - Google Patents

Abstract

PURPOSE: Provided is a production process of titanium-aluminum intermetallic compound parts by powder injection molding which simplifies molding of TiAl and Ti3Al intermetallic compound parts so that it lowers manufacturing cost. CONSTITUTION: The production process of titanium-aluminum intermetallic compound parts by powder injection molding comprises the steps of: (i) putting an alloy powder into a fused binder to mix for more than 10 minutes; (ii) molding the mixture as wanted form; (iii) mitigating internal stress left in a molded body in injection molding to keep current state and eliminate the binder; (iv) eliminating the binder left in the molded body in extracting powder; and (v) giving physical property to the molded body and keeping vacuum state to hold shape.

Description

Manufacturing Method of Titanium-Aluminium Intermetallic Compound Part by Powder Injection Molding Method

The present invention relates to a method for producing a titanium-aluminum-based intermetallic compound component by powder injection molding, and more particularly, to a heat injection TiAl and Ti ₃ Al-based intermetallic compound component having high specific strength in powder injection molding. The present invention relates to a method for producing an intermetallic compound component which makes it possible to reduce the manufacturing cost by simplifying the process when molding.

In general, manufacturing techniques that can precisely manufacture parts with complex shapes and difficult processing include cutting, precision casting, die casting, and powder metallurgy.

Cutting process is problematic in terms of manufacturing cost as well as mass production in that it is a machining process, the manufacturing method by the precision casting method is capable of forming a complex shape, but in the case of small precision parts are expensive and unsuitable for mass production.

The die casting method is limited to low melting point alloys such as Al, Zn, etc., and powder metallurgy has a low production cost in two-dimensional simple shapes, but the manufacturing cost increases due to the increase in the amount of post processing.

However, unlike conventional processing technology, the powder injection molding method is known as a processing technology capable of mass-producing high-performance complex precision parts at a low production cost (about 20-80%).

TiAl or Ti ₃ Al intermetallic compounds are almost impossible to manufacture due to the extreme oxidation reaction during atmospheric dissolution, and the vacuum induction dissolution method is relatively easy to react with the crucible, thus making it difficult to produce a healthy ingot.

For example, it is known that significant inclusions are also incorporated in vacuum induction melting using a CaO crucible, which is known to have a relatively low degree of reaction with Ti.

On the other hand, the vacuum arc melting method has the advantage of producing very healthy ingots, but due to its high manufacturing cost, there is no economic feasibility, and the post-processing process of Ti-Al-based intermetallic compounds is also meticulous due to their hard workability. There is a need for additional high temperature machining processes such as expensive extrusion (or forging), heat treatment, precision machining, etc., to produce the part.

An example of a manufacturing process for lowering the component manufacturing cost of TiAl or Ti ₃ Al intermetallic compound is shown in US Patent 4,707,332. They choose the method of lowering the manufacturing cost of the post-processing process by using CIP (Cold Isostatic Pressing) or powder injection molding using alloy powder.

However, the cited patent has a disadvantage in that it does not properly reflect the process characteristics of a specific alloy because it includes the manufacturing of parts by powder injection molding of all the intermetallic compounds.

And the heat treatment up to 600 ℃ performed to remove the binder after powder injection has a disadvantage that the shape is easily broken by generating a rapid binder removal.

In addition, this method also has a problem that it is not possible to lower the powder manufacturing cost by using the alloy powder prepared by the grinding or atomization of the vacuum arc melted ingot.

The present invention has been made in view of the above-mentioned conventional problems, and its object is to prepare an alloy powder using a high temperature autosynthesis method, and then to prepare a titanium-aluminum-based intermetallic compound component that can be manufactured by powder injection molding. To provide a way.

In order to achieve the above object, the present invention is to put the alloy powder prepared by the autothermal synthesis method in a molten binder which is bonded to each other to maintain the shape of the component and mixed for 10 minutes or more, and the powder is molded into a desired shape The binder was removed while maintaining the shape by relieving the stress remaining in the molded body during the powder injection, and the pyrolysis process was performed to remove the binder remaining in the molded body during the solvent extraction. It characterized in that the sintering process in a vacuum state to maintain.

Therefore, the present invention is suitable for manufacturing parts of Ti-Al-based intermetallic compounds including TiAl, Ti ₃ Al and TiAl ₃ compounds which are difficult to be processed, and the alloy powder is ductile, toughness and strength of Ti-Al-based intermetallic compounds. TiAl is contained in an amount of 0.5-15% (at least one or more elements of Cr, Mn, V, Mo, W, Nb, B, C, and N) added to increase the ratio, wherein TiAl is Cr, Mn, V Ductility is improved by the addition of alloying elements such as), and elements such as Nb, Mo, and W are added to improve oxidation resistance, and intrusion type such as B, C, N, etc. to increase strength through grain refinement and reinforcing material formation. The element was added.

1a and 1b is a photograph showing the appearance of the powder injection molded parts according to the powder injection preheating temperature, the injection molded parts at preheating temperature 70 ℃ and the injection molding parts at preheating temperature 90 ℃,

Figure 2a and Figure 2b is a picture showing the appearance of the molded body according to the pyrolysis temperature, the parts pyrolyzed at 600 ℃ and the components pyrolyzed at 450 ℃.

Figure 3a and Figure 3b is a picture showing the appearance of the molded body according to the sintering atmosphere, it is a part molded in a vacuum atmosphere using an air or rotary pump and a vacuum or argon atmosphere using a diffusion pump.

Hereinafter, the manufacturing method of the titanium-aluminum-based intermetallic compound component by the powder injection molding method of the present invention will be described in detail.

First, in the present invention, after melting the binder in order to bond the alloy powder to each other, the alloy powder is put and mixed for 10 minutes or more. In particular, since the raw material powder is very expensive when the powder is manufactured by vacuum arc melting and atomization by gas spraying, it is economical to use the alloy powder prepared by the autothermal synthesis method.

The binder serves to bond the alloy powder to each other to maintain the shape of the part.

Molding conditions by powder injection should be preheated and injected at 75-105 ℃. The reason for this limitation is that when the preheating temperature is less than 75 ° C., the fluidity is lowered, so that a crack occurs in the molded body after powder injection, and when the temperature is 105 ° C. or more, the fluidity is excessively increased and the shape of the molded body is distorted.

In particular, the present invention is characterized in that it is deposited in a solvent capable of dissolving the binder and maintained for at least 0.5 hours at 20-70 ℃ conditions. This process is a process step for preventing the breakage or severe warping of the molded body due to the rapid binder removal generated during the heat treatment of the vacuum or inert gas atmosphere layer up to 600 ℃.

This solvent extraction is a very important process in the production of powder injection moldings to provide an outpost step that can effectively remove the binder while maintaining the shape and to relieve the stress remaining in the molding at the time of injection.

If you work directly with the pyrolysis process without going through the solvent extraction process, severe warping and shape destruction are inevitable.

The reason for limiting the solvent extraction temperature under the above conditions is that if the solvent is extracted at a temperature below 20 ° C, the temperature becomes too low, and the binder is further removed and the contamination caused by the binder in the post-process is increased. Shape is destroyed. On the other hand, if it exceeds 70 ℃, the binder is severely removed during the solvent extraction process, the shape is severely warped or cracking occurs.

Pyrolysis conditions are preferably in the temperature range of 350-550 ℃, the pyrolysis process is carried out to remove the residual binder not removed at the time of solvent extraction.

The reason for limiting the pyrolysis temperature in the above range is a problem in productivity because the reaction rate is too slow at less than 350 ℃, the reaction rate is too rapid to exceed the 550 ℃ to form a crack or deform the molded body.

In the setting of the sintering process conditions, the sintering atmosphere has a significant influence not only on the physical properties of the Ti-Al intermetallic molded body but also on the shape retention.

For example, in a low vacuum condition, the injection molded body reacts badly and the shape thereof is destroyed. Therefore, the sintering of the powder injection molded body should be carried out at a vacuum degree of 5 × 10 ⁻³ torr or more that can be obtained by a diffusion pump. The sintering temperature is performed at a temperature of 1000-1450 ° C. where sufficient strength can be obtained.

If the sintering temperature is less than 1000 ℃, a large amount of pores are formed in the molded body or the bond strength is lowered easily breakage problem occurs, whereas at a temperature above 1450 ℃ the molded body melts and can not maintain its shape .

The sintered molded body may be subjected to a hot isostatic pressing process to increase the density of the part.

Example 1

In the present invention, after mixing the Ti-46.6-Al-2.OMo-1.4Mn alloy powder and the binder having an average particle size of 19㎛ prepared by the autothermal synthesis method was pressed by injection molding at 60-100 ℃.

Table 1 is a graph showing the appearance observation results according to the powder injection preheating temperature, Figure 1 is a photograph showing the appearance of the molded body according to the injection temperature.

That is, FIG. 1A is injection molded at 70 ° C., showing that a large crack is generated on the side. On the other hand, the molded product injected at 90 ° C as shown in Figure 1b shows a very sound appearance.

TABLE 1

Changes in Crack Initiation and Surface Deformation by Injection Preheating Temperature

Example 2

The molded article injected at 75-105 ° C. was solvent-extracted by dipping in a solvent capable of raising the binder in the state of suppressing the shape change at the maximum temperature. Solvent extraction was performed for 1 hour at 20-70 ℃. The next step is to pyrolyze at a rather high temperature for more efficient binder removal. As a result of examining the shape change of the molded body according to the thermal decomposition conditions, it was observed as Table 2.

For example, when pyrolyzed at 600 ° C., severe cracks occur throughout the parts as shown in FIG. 2A, but parts that are pyrolyzed under optimum conditions (see FIG. 2B) show very healthy surface conditions.

TABLE 2

Appearance Change of Molded Body due to Pyrolysis Error

Example 3

The pyrolyzed molded body was sintered to give strength and rigidity to the part. Sintering was sensitively dependent on the atmosphere of the heat treatment furnace and the results are shown in Table 3. When the degree of vacuum of the sintering furnace is low as shown in FIG. 3a, the shape is completely disintegrated due to the extreme reaction, whereas the component in the case of Ar atmosphere or high degree of vacuum shows a very sound state as in FIG. 3b.

TABLE 3

Change of Shape and Surface State of Molded Body by Sintering Conditions

(However, ++: very good, × ×: very bad, RP: Rotary Pump, DP: Diffusion Pump)

Such a method of manufacturing a titanium-aluminum-based intermetallic compound part by the powder injection molding method of the present invention can mass-produce precision parts having high functions and complex shapes at a low price, and various kinds of materials and difficult materials can be used. It can be effective.

Claims (5)

Adding an alloy powder prepared by a self-heating synthesis method to a binder in a molten state to maintain the shape of a component by mutually bonding the alloy powder and mixing the powder for at least 10 minutes; A powder injection molding process for molding the mixture into a desired shape; Solvent extraction process to remove the binder while maintaining the shape by relieving the stress remaining in the molded body during the powder injection; A pyrolysis process performed to remove the binder remaining in the molded body during the solvent extraction; And a sintering step performed in a vacuum state to impart physical properties to the molded body and maintain the shape. The method of manufacturing a titanium-aluminum-based intermetallic compound component according to claim 1, wherein the molding condition of the powder injection is a preheating temperature range of 75-105 ° C. The titanium-aluminum-based intermetallic compound component according to the powder injection molding method according to claim 1, wherein the solvent is in an atmosphere of 20-70 ° C. during the solvent extraction process for dissolving the binder while safely maintaining the shape of the component. Manufacturing method. The method of claim 1, wherein the temperature of the heat treatment during the pyrolysis process is in the range of 350-550 ° C. The titanium-aluminium-based intermetallic compound component according to claim 1, wherein the small diameter process is sintered at 1000-1450 ° C. in a vacuum or Ar atmosphere of 5 × 10 ⁻³ torr or more. Way

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