JP3069580B2 - Remaining life extension method of single crystal material by reheat treatment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for extending the remaining life of a single crystal material. More specifically, the present invention relates to a method of extending the remaining life of a single crystal material such as a Ni-based super heat-resistant single crystal alloy used as a turbine blade material of a jet engine or a gas turbine with respect to strength deterioration.

[0002]

2. Description of the Related Art Conventionally, components such as a jet engine and a turbine blade of a gas turbine which are used under high temperature and high stress are damaged at a grain boundary or the like when used for a certain period of time. Since the strength starts to deteriorate, it is replaced with a new part for safety. Various studies have been made to extend the remaining life of the turbine blade material for the purpose of improving the economic efficiency by reducing the frequency of such component replacement and increasing the reliability of the component. For example,
In the case of polycrystalline materials, the creep damage generation behavior of austenitic heat-resistant steel is examined in detail and used as an index for predicting the remaining life. Has been performed to examine the effect of extending the remaining life. In the case of a Ni-based super heat-resistant polycrystalline alloy having a grain boundary in the alloy, the creep test was interrupted and HIP (hot issostatic
Pressing) treatments to eliminate the cavities or to further polish the cavities have been considered, and in fact, it has been reported that these treatments have improved the life.
However, high-pressure processing such as HIP is not always practically used because it increases costs economically. In addition, studies on such life extension have been limited to polycrystalline materials, and no reports have been made on single crystal materials such as Ni-based super heat resistant single crystal alloys. Is the actual situation.

[0003] In the case of a polycrystalline material having a grain boundary and a single crystal material, the mechanism leading to destruction is different. Therefore, a method different from that of the polycrystalline material is required for extending the life. Moreover, although single crystal materials are increasingly expected to be used as high-temperature, high-strength materials such as turbine blade materials for jet engines and gas turbines, practically no measures have been found for extending their life. It is.

Accordingly, the present invention is useful as a material for a turbine blade of a jet engine or gas turbine or the like.
It is an object of the present invention to provide a method for extending the remaining life of a single crystal material that can extend the remaining life of a single crystal material made of a base super heat-resistant single crystal alloy and improve mechanical properties such as creep characteristics.

[0005]

Means for Solving the Problems The present invention solves the above-mentioned problems by providing a single crystal material made of a Ni-based super heat-resistant single crystal alloy whose strength has been deteriorated by use at a high temperature by performing a heat treatment. It is a method of extending the remaining life of crystalline materials.
The time required for complete solution treatment and aging treatment of single crystal material in the steady creep region or the initial stage of accelerated creep
A method for extending the remaining life of a single crystal material, characterized by performing a treatment .

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the method for extending the remaining life of a single crystal material according to the present invention is essentially characterized by heat-treating a single crystal material whose strength has deteriorated.
In principle, this can be explained for example in FIGS. That is, as illustrated in FIG. 1, for example, in the conventional polycrystalline material, coarsening and disorder of the structure occur at an early stage of creep, and defects such as voids and grain boundary oxidation occur at the grain boundaries. In such a polycrystalline material, even if the heat treatment is performed again, the structure in the crystal grains is refined and the precipitates are refined and recovered, but voids at the grain boundaries and grain boundary oxidation remain, so the overall recovery of the structure is incomplete. It is. On the other hand, as illustrated in FIG. 2, in a single crystal alloy, the raft (plate-like γ ′ phase perpendicular to the stress axis) is coarsened and disordered when used under a high temperature and a high pressure. Will recover completely.

Due to such a phenomenon, a single crystal material whose strength is deteriorated when used for a long time under high temperature and high stress as a turbine blade of a jet engine or a gas turbine, for example, a member of a Ni-based super heat resistant single crystal alloy is being used. Suspend the use in the steady creep range or the early stage of the acceleration creep range.
By performing the reheat treatment, the creep characteristics of the virgin material can be obtained, and the remaining life, particularly the creep characteristics, of these members can be extended. For this reason, the turbine blade material and the like can be reused repeatedly. Therefore,
Cost performance of single crystal turbine blades and the like is improved. Further, in the present invention, the reheat treatment can be a solution treatment and an aging treatment, and there is no special temperature condition. It can be implemented using.

[0008] Incidentally, it is not limited to Ni-based alloy as a single crystal material, also with the present invention with respect to Co group, W group, Mo group, various different monocrystalline material such as ceramics
Is considered to be applied. Conditions such as the temperature of the heat treatment are selected according to the types of these materials. Hereinafter, examples will be shown, and embodiments of the present invention will be described in more detail by way of example.

[0009]

Example: Cr: 6.0 wt%, W: 10.2 wt%,
Al: 5.0 wt%, Ta: 11.0 wt%, Ni: Ni-Cr-W-Al-Ta based Ni-based super heat-resistant single crystal alloy consisting of the remainder, creeped using a test piece with a parallel portion φ4 × 20 mm. A creep test was performed at a test temperature of 1080 ° C. and a stress of 137 MPa. The test results are shown in FIG. In FIG. 3 , a curve A shows a creep curve of the virgin material tested up to the fracture. (A) and (b) show the virgin material A in FIG.
Fig. 3 shows a region interrupted in a steady creep region and an accelerated creep region. At this time, (a) is the creep life ratio: t / tr =
0.5, (b) is the creep life ratio: t / tr = 0.9
It is.

Therefore, in (a) and (b), the reheat treatment of the present invention was performed. In this reheat treatment,
In the case of the above alloy, the solution is heat-treated at 1345 ° C. for 0.5 hour, air-cooled, and kept at 1080 ° C. for 5 hours as an aging treatment.
After air cooling, the resultant was further kept at 870 ° C. for 20 hours, and then subjected to air cooling two-stage aging treatment. After this reheat treatment, a creep test was performed again at a creep test temperature of 1080 ° C. and a stress of 137 MPa. As a result, these test pieces exhibited almost the creep characteristics of a virgin material, and as a result, the rupture life was extended to points B and C in FIG. 1, respectively.

[0011]

As described above, according to the present invention,
A single crystal material whose strength is deteriorated when used for a long time under high temperature and high stress as a turbine blade of a jet engine or gas turbine, for example, a member such as a Ni super heat resistant single crystal alloy, is used in a steady creep region or an early stage of an accelerated creep region during use. By suspending the use of the virgin material and performing the heat treatment again, the creep characteristics of the virgin material can be obtained, and the remaining life of these members, especially the creep characteristics, can be extended. Therefore, the turbine blade material and the like can be reused repeatedly, and the cost performance of the single crystal turbine blade material and the like is improved. Furthermore, since the reheat treatment is a solution treatment and an aging treatment, there is no special temperature condition, so that the present invention can be performed using a normal heat treatment furnace without preparing a special heat treatment furnace used for the reheat treatment. It can be implemented, and from this point, it has excellent effects such as good cost performance.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a structural change of a polycrystalline alloy due to a reheat treatment.

FIG. 2 is a schematic diagram of a change in structure of a single crystal alloy due to reheat treatment.

FIG. 3 is a diagram showing a creep test result of a Ni-based super heat-resistant single crystal alloy as a single crystal material.

Continuing from the front page Judge Satoru Satoru Miura Judge Toshio Kanazawa Judge Shun Toshibe 26343 (JP, A) JP-A-63-118037 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22F 1/10

Claims (1)

(57) [Claims] 1. Ni whose strength has been deteriorated by use at a high temperature.
This is a method of extending the remaining life by subjecting a single crystal material composed of a base super heat-resistant single crystal alloy to heat treatment, in which the working time is reduced to a single crystal material in a steady creep region or in an early stage of accelerated creep by complete solution treatment and aging treatment. Heat treatment
A method for extending the remaining life of a single-crystal material, characterized by performing the following .