JP2008208432A - METHOD FOR PRODUCING POWDER SINTERED COMPACT OF TiAl INTERMETALLIC COMPOUND BASED ALLOY - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing the powder sintered compact of a TiAl intermetallic compound based alloy which improves the cold machinability and ductility as the defects of a TiAl intermetallic compound based alloy, attains material properties excellent in a homogeneous and fine structure, and can obtain a perfectly dense metal sintered compact having a shape close to that of a final product with high reproducibility. <P>SOLUTION: An alloy essentially consisting of a TiAl intermetallic compound is melted, the droplets obtained by the melting are rapidly solidified, so as to obtain metal powder, the metal powder is charged to a can, and is thereafter vacuum-evacuated, and the whole of the can is heated and pressurized by hot isostatic pressing, thus the powder sintered compact is produced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a powder sintered body of a TiAl intermetallic compound base alloy.

An alloy mainly composed of a TiAl intermetallic compound, which is a lightweight heat-resistant material, is expected as a next-generation material, and is very promising as a material for parts used in high-temperature parts such as aerospace equipment and turbines. However, the application range of an alloy mainly composed of a TiAl intermetallic compound is limited to a block-shaped part by conventional casting or forging.
And as a manufacturing method of a TiAl intermetallic compound base alloy, the casting method which passed through the conventional melt | dissolution process and the synthesis method which mixes each metal powder of Ti and Al are known.
JP-A-7-197154 JP 2003-147475 A Japanese Patent Publication No.1-30898 JP-A-5-70859

  However, both of the casting method and the synthesis method have many restrictions for producing a defect-free arbitrary shape with a uniform microstructure. In particular, the metal structure of parts manufactured only by casting is usually coarsened, and in order to make it finer and give strength and ductility, processes such as hot forging and heat treatment are required. There is a problem that there is a limitation of material loss and shape.

  Therefore, the present invention has been made under the circumstances as described above, and the object of the present invention is to improve the machinability and ductility at room temperature, which is a defect of the TiAl intermetallic compound base alloy, and is excellent in a homogeneous and fine structure. It is an object of the present invention to provide a method for producing a sintered powder of TiAl intermetallic compound base alloy that can obtain a completely dense sintered metal having a shape close to the final product and good reproducibility.

  The present invention relates to a method for producing a powder sintered body of a TiAl intermetallic compound-based alloy, and the above object of the present invention is to dissolve an alloy containing a TiAl intermetallic compound as a main component and rapidly solidify droplets obtained by the melting. To obtain a metal powder, put the metal powder in a can and then evacuate, and heat and press the whole can by hot isostatic pressing to produce a powder sintered body .

  Further, the object of the present invention is that the metal powder is produced by a plasma rotating electrode method or a gas atomizing method, or the metal powder is produced by rapid solidification from a droplet using a centrifugal force or a gas jet. It is achieved more effectively by being a method or by carrying out sintering by the hot isostatic pressing while maintaining the fine structure while preventing coarsening of the fine structure of the metal powder.

  In the present invention, a finely structured metal powder obtained by melting a TiAl intermetallic compound-based alloy and rapidly solidifying from a droplet is sintered under an optimal isotropic pressure and heating atmosphere. It became possible to inhibit grain growth of the steel and to impart strength and ductility at room temperature.

  According to the manufacturing method of the present invention, the normal temperature tensile strength under the HIP treatment (hot isostatic pressing) condition indicated by symbol # 6 in FIG. , Improvement in ductility due to the improvement of strength by about 25% or more and refinement of the metal structure is seen compared to the original casting material, and the workability is also improved. In addition, the near net shape technology using a metal can applied to the manufacturing method of the present invention can be expected to be effective in reducing the manufacturing cost because the material can be saved and the residual stress inside the material is small. It produces an excellent effect that it can be manufactured with good reproducibility.

  Furthermore, according to the manufacturing method of the present invention, a metal sintered body having a relatively high degree of freedom can be accurately manufactured by a near net forming technique using a metal capsule, and there is an effect that there are few restrictions on material loss and shape.

  The present invention has developed a sintered material by pressure sintering method by pulverization and HIP treatment (hot isostatic pressing) for the purpose of expanding the application range of TiAl intermetallic compound base alloy, and pressure sintering By optimizing the manufacturing process of the sintered material in the construction method, it is possible to obtain excellent material property results. The near net shape technology, which is a feature of the present invention, has a possibility of a new application that compensates for the disadvantages of the sintered material in the pressure sintering method with poor machinability because the material saving and the residual stress inside the material are small. I can expect. In addition, by minimizing the influence of oxidation or the like in the powdering and sintering techniques, it is possible to manufacture parts having a uniform metal structure that is defect-free and cannot be obtained by other methods.

  Hereinafter, the manufacturing method of the powder sintered compact using the TiAl intermetallic compound base alloy of this invention is demonstrated with reference to drawings.

  FIG. 1 is a schematic diagram showing an example of a plasma rotating electrode method (PREP method) apparatus 10 used in the present invention, and FIG. 2 is a schematic diagram showing an example of a gas atomization apparatus 20. As shown in the apparatus 10 of the plasma rotating electrode method in FIG. 1, a raw material base material (rotating electrode) 12 and a plasma torch 13 are disposed facing each other in a chamber 11, and the raw material base material 12 is rotated at the tip thereof. Metal droplets and solidified metal powder can be obtained by irradiating with plasma and then rapidly cooling. 2 is heated by an induction heating coil 22 disposed at the tip of the raw material base 21 to melt the raw material base 21, and the molten metal droplets fall midway. Is provided with a donut-shaped nozzle member 23 that irradiates an inert gas from a nozzle, and the metal droplets from the induction heating coil 22 are irradiated with an inert gas and rapidly cooled to thereby cool the metal droplets and the solidified metal. Powder can be obtained.

  In the present invention, as described above, the metal powder generated by the plasma rotating electrode method (PREP method) apparatus 10 or the gas atomization apparatus 20 is used. However, other powder manufacturing methods can directly solidify from droplets. Other methods may be selected as long as the metal powder is manufactured. However, it is a necessary condition that the metal powder produced by the method has little change from the components of the raw material base material and little contamination such as oxidation and nitridation.

  In the present invention, the metal powder obtained by these methods is filled in a metal can 30 as shown in FIG. 3 in an inert gas such as Ar, and then the gas in the can 30 is exhausted from the exhaust port 31. To do. The degree of vacuum in the can 30 must be exhausted to a degree of vacuum of at least 0.013 Pa so that the remaining gas does not generate pores after sintering. Further, in order to completely remove impurities adhering to the surface of the metal powder and moisture adhering to the surface, it is desirable to heat to 100 ° C. or more from the outside of the can 30 simultaneously with evacuation. For the final sealing of the can 30, a pipe (not shown) connected to the exhaust port 31 is crushed by a press or the like while being evacuated to a vacuum, cut and welded.

  The conditions for sintering the entire can 30 by the HIP process need to select an optimum condition depending on the composition of the filled metal powder. However, since the microstructure refined by rapid solidification is not coarsened, generally 1250 is used. It is desirable to select a combination having a relatively short holding time under the condition of not more than ° C. and not less than 118 MPa.

  Here, the HIP treatment means that in a high-temperature inert gas atmosphere, by applying a high pressure from the outside of the can, the space existing inside the can is extinguished, and the surfaces of the metal powders are forcibly combined, This is a typical process in the powder sintering process that is metallurgically integrated.

  The metal can 30 to be used is made of a material such as Ti that does not cause a reaction or diffusion to the metal powder to be filled and that does not crack or melt during the shrinkage process in the HIP process. The design of the can 30 is such that the near net shape having a finishing allowance in the shape of the final product is obtained when the can 30 is completely contracted, so that the packing density, plastic flow, and material characteristics of the metal powder are obtained. And based on parameters, such as a material characteristic and shape of the can 30 to be used, it determines through an analysis and trial manufacture.

  Examples of the present invention will be described below.

  In the production method of the present invention, first, a Ti-A1 intermetallic compound base alloy was prepared as a raw material base material, and a metal powder was produced using a plasma rotating electrode method (PREP method). The particle diameter of the obtained metal powder is about 50 to 300 μm, and there is no significant change in the comparison of the components of the raw material base metal and the metal powder. The electron probe microanalyzer, the non-dispersive infrared absorption method and the thermal conductivity method are used. Used to confirm. An example of the obtained metal powder is shown in FIG.

  After filling the can 30 as shown in FIG. 3 using the metal powder obtained as described above and exhausting the inside of the can to 0.013 Pa or less, it is shown by symbols # 1 to # 6 in FIG. HIP treatment was performed under various conditions, and the normal temperature tensile strength and the structure observation were confirmed by a backscattered electron image of an electron probe microanalyzer.

  As a result, by optimizing the HIP processing conditions, it was discovered that the tensile strength at room temperature under the HIP processing conditions of symbol # 6 is 25% higher than that of the casting material of symbol # 7. Even in the metal structure of the sintered body, it was possible to obtain a material having a finer and more uniform structure than the original casting material.

  Moreover, also in the HIP processing of symbols # 2 to # 5, a result higher than the normal temperature tensile strength of the casting material of symbol # 7 was obtained, and the refinement and uniformity of the metal structure could be confirmed from the reflected electron image.

  These examples are the results obtained by the HIP treatment conditions in the used TiAl intermetallic compound-based alloy, but depending on the speed of grain growth in the sintering process of HIP treatment, the metallurgical change of the structure, and the high temperature strength of the alloy. Further, it is possible to further optimize the processing temperature, pressure and holding time, and the present invention is not limited to the indicated condition range. That is, the effectiveness of the HIP treatment is shown as a means for sintering while maintaining the fine structure while preventing coarsening of the fine structure of the metal powder.

It is a schematic diagram which shows the apparatus example of the plasma rotating electrode method in the manufacturing method which concerns on this invention. It is a schematic diagram which shows the apparatus example of the gas atomizing method in the manufacturing method which concerns on this invention. It is a typical structure figure showing an example of a metal can used for the manufacturing method of the present invention. It is a structure | tissue chart which shows an example of the metal powder manufactured by the plasma rotating electrode method in the Example of this invention. It is a figure which shows the list of normal temperature tensile strength and a reflected-electron image of the sintered compact manufactured on the HIP process conditions in each Example of this invention. It is a structure | tissue chart of the reflected-electron image of a sintered compact in the HIP processing conditions of code | symbol # 1. It is a structure | tissue chart of the reflected-electron image of a sintered compact in the HIP processing conditions of code | symbol # 2. It is a structure | tissue chart of the backscattered electron image of the sintered compact in the HIP processing conditions of the symbol # 3. It is a structure | tissue chart of the reflected-electron image of a sintered compact in the HIP processing conditions of code | symbol # 4. It is a structure | tissue chart of the reflected-electron image of the sintered compact in the HIP processing conditions of the symbol # 5. It is a structure | tissue chart of the reflected-electron image of a sintered compact in the HIP processing conditions of the symbol # 6. It is a structure | tissue chart of the reflected-electron image as a cast material in the raw material before pulverization of the symbol # 7.

Explanation of symbols

10 Apparatus for Plasma Rotating Electrode Method (PREP Method) 11 Chamber 12 Rotating Base Material (Rotating Electrode)
13 Plasma torch 20 Gas atomizing apparatus 21 Raw material base material 22 Induction heating coil 23 Nozzle member 30 Metal can 31 Exhaust port

Claims (4)

An alloy containing a TiAl intermetallic compound as a main component is dissolved, and droplets obtained by the dissolution are rapidly solidified to obtain a metal powder. The metal powder is put into a can and then evacuated to heat the entire can. A method for producing a powder sintered body of a TiAl intermetallic compound-based alloy, wherein a powder sintered body is produced by heating and pressing with an isostatic pressing treatment. The method for producing a sintered powder of a TiAl intermetallic compound based alloy according to claim 1, wherein the metal powder is produced by a plasma rotating electrode method or a gas atomizing method. The method for producing a powder sintered body of a TiAl intermetallic compound based alloy according to claim 1, wherein the production of the metal powder is a method of rapidly solidifying from droplets using a centrifugal force or a gas jet. The TiAl intermetallic compound group according to any one of claims 1 to 3, wherein sintering is performed by the hot isostatic pressing while the microstructure is maintained while preventing the coarsening of the microstructure of the metal powder. A method for producing a powder sintered body of an alloy.