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TiAl-BASED ALLOY, PROCESS FOR PRODUCING SAME, AND ROTOR BLADE USING SAME

a technology of tial-based alloys and rotor blades, which is applied in the manufacture of engines, mechanical equipment, machines/engines, etc., can solve the problems of poor product quality, minimal industrial application, and low creep strength of tial-based alloys, and achieve excellent forgeability, and the effect of high-temperature strength and oxidation resistan

Inactive Publication Date: 2010-12-16
MITSUBISHI HEAVY IND LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009]On the other hand, the hot forging disclosed in patent citation 2 enables forge working to be performed using general-purpose equipment in substantially the same manner as typical steel materials, and therefore offers a high degree of productivity and excellent practical applicability.
[0028]The present invention is able to provide a TiAl-based alloy that exhibits high levels of high-temperature strength and oxidation resistance, as well as excellent forgeability. A rotor blade that uses the TiAl-based alloy of the present invention exhibits excellent high-temperature strength and oxidation resistance, and can therefore be used in operating environments of 650° C. or higher. Further, because the TiAl-based alloy of the present invention exhibits favorable forgeability, it is able to be molded within a comparatively short time period.

Problems solved by technology

The superplastic working disclosed in patent citation 1 involves performing plastic working at a low strain speed while maintaining a high temperature, and therefore suffers from poor productivity and has minimal industrial applicability.
However, although the TiAl-based alloy disclosed in patent citation 2 provides improved high-temperature strength by using hot forging to precipitate lamellar grains, the creep strength is lower than that of cast TiAl-based alloys, and the oxidation resistance also tends to be unsatisfactory.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0048]TiAl-based alloy ingots comprising the components listed for example 1-1 to example 1-4 in Table 1 were produced by casting. Each ingot was cut to predetermined dimensions and subjected to surface machining, yielding a columnar TiAl-based alloy material having a diameter of 80 mm and a height of 60 mm.

[0049]Each TiAl-based alloy material was heated and held at 1300° C. inside a heavy oil furnace. Following holding at this temperature, the TiAl-based alloy material was removed from the heavy oil furnace, and subjected to upset forging at a forging ratio of 3 s, using a general-purpose 300-ton hydraulic press. The operation from removal of the TiAl-based alloy material from the furnace until completion of the forging was completed within 10 seconds. Following forging, the alloy material was cooled by atmospheric cooling on top of a steel trestle. A post-forging heat treatment was performed by subjecting the forged material to stress removal annealing for 24 hours at 800° C. usin...

examples 2 to 5

[0051]TiAl-based alloy ingots comprising the components listed for example 2 to example 5 in Table 1 were produced by casting. Each ingot was cut and subjected to surface machining, yielding a columnar TiAl-based alloy material having a diameter of 80 mm and a height of 60 mm. Using the same procedure as that described for example 1, the TiAl-based alloy material of example 2 was subjected to forging and post-forging stress removal annealing.

[0052]Each TiAl-based alloy was evaluated for forgeability, and tested for creep strength and oxidation resistance.

[0053]The forgeability evaluation was conducted by visually checking the forged ingot for the presence of cracks. If no cracks were observed, the forgeability was evaluated as good (o), whereas if cracks were visible, the forgeability was evaluated as poor (×).

[0054]The creep strength test was performed by cutting a test specimen from the annealed ingot, and then testing the specimen at a test temperature of 760° C. and a load stres...

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Abstract

A hot-forged TiAl-based alloy having excellent oxidation resistance and high strength at high temperatures, and a process for producing such an alloy. A TiAl-based alloy comprising Al: (40+a) atomic % and Nb: b atomic %, with the remainder being Ti and unavoidable impurities, wherein a and b satisfy formulas (1) and (2) below.0≦a≦2  (1)3+a≦b≦7+a  (2)Also, a TiAl-based alloy comprising Al: (40+a) atomic % and Nb: b atomic %, and further comprising one or more elements selected from the group consisting of V: c atomic %, Cr: d atomic % and Mo: e atomic %, with the remainder being Ti and unavoidable impurities, wherein a to e satisfy formulas (3) to (9) shown below.0≦a≦2  (3)3+a≦b+1.0c+1.8d+3.8e≦7+a  (4)b≧2  (5)c≧0  (6)d≧0  (7)e≧0  (8)c+d+e>0  (9)

Description

TECHNICAL FIELD[0001]The present invention relates to a TiAl-based alloy, a process for producing the alloy, and a rotor blade that uses the alloy.BACKGROUND ART[0002]TiAl-based alloys, which are lightweight (with a specific gravity of approximately 4) and exhibit excellent heat resistance, are attracting considerable attention as potential materials for the rotor blades used within gas turbines and Turbo-chargers. Particularly in the case of very large rotor blades, the lighter the weight of the members that constitute the rotor blade, the smaller the centrifugal stress becomes, which enables an increase in the maximum rate of revolution, an increase in the surface area of the rotor blade, and a reduction in the load stress applied to the disc portion.[0003]TiAl-based alloys are alloys that are composed mainly of intermetallic compounds such as TiAl and Ti3Al, which exhibit excellent high-temperature strength, and these alloys therefore have excellent heat resistance. However, TiAl...

Claims

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Application Information

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IPC IPC(8): C22C14/00C22F1/18B21J5/00
CPCB21J5/00B21K3/04C22C14/00C22F1/183F05B2220/40F05B2230/25F05C2201/0412
Inventor SHINDO, KENTAROTETSUI, TOSHIMITSUTAKEYAMA, MASAO
Owner MITSUBISHI HEAVY IND LTD
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