Metal treatment – Process of modifying or maintaining internal physical... – Heating or cooling of solid metal
Reexamination Certificate
1999-02-19
2001-01-09
Yee, Deborah (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Heating or cooling of solid metal
Reexamination Certificate
active
06171417
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a property recovering method for a Ni-base heat resistant alloy whose properties such as strength and ductility have been deteriorated by use at a high temperature.
2. Description of the Related Art
A Ni-base heat resistant alloy which has a &ggr;′ intermetallic compound of Ni
3
(Al, Ta, Ti) as a main ingredient and also has a solid solution strengthening function given by precipitation hardening of the second phase and Mo, W, or the like has been used for a high-temperature member such as a moving blade of gas turbine and jet engine. Here, the second phase is a phase containing an intermetallic compound, carbide, and the like. The aforesaid Ni-base heat resistant alloys include a Ni-base heat resistant alloy disclosed in Japanese Patent Provisional Publication No. 6-57359 (No. 57359/1994) (hereinafter referred to as alloy A) and a Ni-base heat resistant alloy commercially available under the tradename Inconel 738 (hereinafter referred to as alloy B). The compositions of these alloys A and B are given in Table 1.
TABLE 1
Chemical composition of material subjected to property recovering treatment in
accordance with the present invention (wt %)
Element
Cr
Co
Mo
W
Ta
Al
Ti
C
B
Alloy A
13.1-15
8.5-10.5
1-3.5
3.5-4.5
3-5.5
3.5-4.5
2.2-3.2
0.06-
0.025 or
0.12
less
Alloy B
15.7-
8-9
1.5-2
2.4-2.8
1.5-2
3.2-3.7
3.2-3.7
0.09-
0.007-
16.3
0.13
0.012
Element
Zr
Mg/Ca
Hf
Nb
Fe
Mn
Si
S
Ni
Alloy A
0.01-
1-100
1.5 or
—
—
—
—
—
Balance
0.05
ppm
less
Alloy B
0.03-
—
—
0.6-1.1
0.05 or
0.02 or
0.3 or
0.015 or
Balance
0.08
less
less
less
less
Note)
Al + Ti: 6.5-7.2 (Alloy B)
For the Ni-base heat resistant alloy of this type, the second phase (intermetallic compound, carbide, etc.) is coarsened or the diffusion and condensation of impurity elements take place because of heat history due to the long-term use at a high temperature, by which the strength and ductility are decreased. Therefore, the member using such an alloy becomes incapable of being used, and finally must be scrapped because of the formation of cracks. Also, these Ni-base heat resistant alloys are generally very expensive.
SUMMARY OF THE INVENTION
The present invention has been made in view of the aforementioned situation of the prior art, and accordingly an object of the present invention is to provide a property recovering method which can be applied to a high-temperature member such as a blade member that must be scrapped due to the deterioration of properties such as strength and ductility caused by the long-term use at a high temperature to recover its properties to those before the use, enable its reuse, and contribute to the effective use of resources and the conservation of environment.
In order to solve the above problems, the inventors have earnestly studied a property recovering method for a Ni-base heat resistant alloy whose properties have been deteriorated by the long-term use at a high temperature. As a result, we found that the properties can be recovered by performing two-stage solution treatment at a predetermined temperature on the alloy having deteriorated properties and then by performing aging treatment thereon, and completed the present invention.
A first mode of the present invention is a property recovering method for a Ni-base heat resistant alloy, in which a Ni-base heat resistant alloy containing, in percent by weight, 13.1-15% Cr, 8.5-10.5% Co, 1-3.5% Mo, 3.5-4.5% W, 3-5.5% Ta, 3.5-4.5% Al, 2.2-3.2% Ti, 0.06-0.12% C, 0.025% or less B, 0.01-0.05% Zr, 1-100 ppm Mg and/or Ca, and 0-1.5% Hf, the balance being Ni and unavoidable impurities, whose properties have been deteriorated by heat history, is subjected to first-stage solution treatment, in which the alloy is held at a temperature of 1175 to 1225° C. for 1 to 5 hours and then furnace-cooled, then subjected to second-stage solution treatment, in which the alloy is held at a temperature of 1115 to 1165° C. for 1 to 5 hours and then air-cooled, and further subjected to aging treatment, in which the alloy is held at a temperature of 810 to 860° C. for 22 to 26 hours.
A second mode of the present invention is a property recovering method for a Ni-base heat resistant alloy, in which a Ni-base heat resistant alloy containing, in percent by weight, 15.7-16.3% Cr, 8-9% Co, 1.5-2% Mo, 2.4-2.8% W, 1.5-2% Ta, 3.2-3.7% Al, 3.2-3.7% Ti, 0.09-0.13% C, 0.007-0.012% B, 0.03-0.08% Zr, 0.6-1.1% Nb, 0.05% or less Fe, 0.02% or less Mn, 0.3% or less Si, and 0.015% or less S (where Al+Ti: 6.5-7.2%), the balance being Ni and unavoidable impurities, whose properties have been deteriorated by heat history, is subjected to first-stage solution treatment, in which the alloy is held at a temperature of 1175 to 1225° C. for 1 to 5 hours and then furnace-cooled, then subjected to second-stage solution treatment, in which the alloy is held at a temperature of 1115 to 1165° C. for 1 to 5 hours and then air-cooled, and further subjected to aging treatment, in which the alloy is held at a temperature of 810 to 860° C. for 22 to 26 hours.
By performing heat treatment in accordance with the method of the present invention, the properties of a Ni-base heat resistant alloy whose properties such as strength and ductility have been deteriorated by the second phase coarsened by heat history can be recovered to the state before being subjected to heat history.
Also, the present invention enables the reuse of a member that had to be scrapped conventionally, and can contribute to the saving and effective use of expensive metallic elements and further to the conservation of environment.
REFERENCES:
patent: 3898109 (1975-08-01), Shaw
patent: 4624716 (1986-11-01), Noel et al.
patent: 4753686 (1988-06-01), Company et al.
patent: 5900084 (1999-05-01), DeLuca et al.
patent: 119 618 (1976-05-01), None
patent: 0 184 949 (1986-06-01), None
patent: 6-057359 (1994-03-01), None
patent: 2066702 (1996-09-01), None
Rejuvenation of Turbine Blade Material by Thermal Treatment, M. D. Ross et al.; Chemical Abstracts, vol. 93, No. 6, Aug. 11, 1980.
European Search Report (with Annex) for EP 99 30 1222, completed May 11, 1999, by N. Gregg.
Hibaru Yoshinao
Imazu Takayuki
Kawai Hisataka
Okada Ikuo
Alston & Bird LLP
Mitsubishi Heavy Industries Ltd.
Yee Deborah
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