JP2001220636A - Nickel aluminide series superheat resistant alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart improved weldability required as a structural material to an Ni3Al series Ni base alloy used as a high temperature structural element while maintaining good mechanical various properties at high temperature and room temperature. SOLUTION: This Ni base superalloy is composed of, by weight, 6.0 to 9.0% Al, 2.0 to 15.0% Cr, 0.5 to 3.0% Zr, 3.0% or less Fe, and the balance substantial Ni and has a metallic structure composed of a Ni3Al series intermetallic compound as the main phase (volume ratio of 70% or more). The composition containing one or more than two kinds of elements selected from 0.5 to 5% W, 0.1% or less C and 0.003 to 0.03% N in addition to the above various elements is given at request.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel aluminide superalloy having excellent mechanical strength in high temperature and room temperature ranges, high temperature creep resistance, and the like, and having good weldability desired as a material for a structural part. .

[0002]

2. Description of the Related Art Ni ₃ Al (trinickel aluminide) is Ni 87 wt% in a Ni—Al binary phase diagram.
It is an intermetallic compound (melting point about 1390 ° C.) having a face-centered cubic crystal structure which appears in the region before and after (having a width of about ± 4 wt%). This shows a unique physical property that the yield strength indicating the strength of the material increases with increasing temperature over a wide temperature range. The ability of a Ni-based superalloy to maintain a high stress level up to a high temperature range depends on such properties of Ni ₃ Al which is abundantly dispersed and precipitated in a Ni solid solution.

However, the Ni ₃ Al intermetallic compound is extremely brittle not only at a low temperature but also at a high temperature, and hardly shows any elongation, which hinders the industrial application of this kind of Ni-base superalloy. Various attempts have been made to improve the properties of this alloy. For example, Japanese Patent Application Laid-Open No. 62-93334 discloses a Ni ₃ Al base material and a group IVB element (Zr, Hf) of 0.
2 to 1.5%, Al 17 to 20%, Cr 4.5 to 8%, B 0.05 to 0.2%, Fe 9 to 1
6%, rare earth elements (Ce, etc.) 0.001 to 0.004%, the balance Ni, high temperature strength, ductility, Ni-base alloy having improved hot workability and the like, in JP-B-63-66374, Ni ₃ Al Mo 0.01-2.0%, B0.05-3.0%, Zr0.5-
There is disclosed a nickel aluminide-based alloy in which room temperature ductility and strength are improved by adding 4.0% or the like.

Japanese Patent Application Laid-Open No. 63-266036 discloses that in atomic%, Ni is 75.4 to 79%, Al is 7 to 12%, B is 0.5% or less, and C is 0.9 or less.
%, Hf 0.5-4%, Fe 4.5-11%, Mo, W, Nb, Zr, etc. ≤ 3%, and the metal structure is mainly composed of Ni ₃ Al.
A Ni-based alloy having improved strength, disclosed in Japanese Patent Application Laid-Open No. 4-501440, has an atomic percentage of Al 15-18.5%, Cr 6-10%, Zr 0.05-0.35.
%, B 0.08 to 0.30%, nickel aluminide alloy with improved hot ductility, workability, strength, etc., Patent No. 2599
No. 236 discloses that, by weight%, Group IVb element (Hf, Zr) <1
%, Fe14.5 ~ 17.5%, rare earth elements (Ce, Y, La, etc.) ≤0.01%,
A nickel aluminide alloy that can be processed at high temperature and is composed of B 0.01 to 0.05%, Mo ≦ 4%, and the balance Ni ₃ Al is disclosed.

[0005]

The conventional nickel aluminide-based alloy exhibits excellent oxidation resistance even in a high temperature range exceeding 1050 ° C. However, the high temperature strength and the creep rupture strength sharply decrease. The present invention is excellent in not only oxidation resistance in such a high-temperature use environment, but also has excellent strength and creep resistance properties, and has good weldability, for example, a radiant tube disposed in a steel heating furnace. , A dry roll constituting a transport roll in a heating furnace,
An object of the present invention is to provide an improved nickel aluminide-based super heat-resistant alloy that enables industrial application as a structural material in various fields, such as a reaction tube installed in a reaction furnace in the petrochemical industry.

[0006]

DISCLOSURE OF THE INVENTION The nickel aluminum of the present invention
The weight of the nitride-based super heat-resistant alloy is Al: 6.0-9.
0%, Cr: 2.0-15.0%, Zr: 0.5-3.
0%, Fe: 3.0% or less, and the balance is substantially made of Ni.
, Ni_Three Metal structure with Al-based intermetallic compound as main phase
Have.

[0007] The nickel aluminide alloy of the present invention may contain 0.5 to 5% of W, 0.
A chemical composition is provided which contains one or more elements of 1% or less of C and 0.003 to 0.03% of N.

[0008] Ni ₃ which is the main phase of the metal structure of the alloy of the present invention
The Al-based intermetallic compound forms a so-called LI _2- type ordered lattice, and has a structure in which Al and Ni are arranged at regular positions in a face-centered cubic lattice.

Regarding the metal structure of the alloy of the present invention, "Ni₃
"The main phase is an Al-based intermetallic compound."₃Al-based
Structure consisting of a single phase of intermetallic compound, or Ni₃Al
Mixed phase of the base intermetallic compound and the Ni solid solution
Ni₅Zr crystallized phase may be mixed)
Means having an organization. Ni_Three Al-based metal
To sufficiently develop high-temperature properties based on the physical properties of compounds
In addition, Ni₃Al-based intermetallic compound
The ratio is 70% by volume or more.

The reasons for limiting the components of the alloy of the present invention are as follows. All indications of element content are based on weight. Al: 6.0 to 9.0% Al is a fundamental element for forming the _Ni 3 Al intermetallic compound with Ni. If the content is less than 6.0%, the formation of Ni ₃ Al phase is insufficient, and high temperature strength cannot be obtained. On the other hand, if the content exceeds 9.0%, creep rupture life is secured in relation to other elements. I cannot do it.

Cr: 2.0-15.0% Cr increases the tensile strength and proof stress at room temperature. This effect appears when the content is 2.0% or more. However, if the amount is excessively increased, the ductility at room temperature is impaired, so that it should not exceed 15.0%. Preferably it is 4.0-8.0%.

Zr: 0.5-3.0% Zr forms Ni ₅ Zr at the dendrite grain boundary, and has a strength (tensile strength, 0.2%) in a high temperature region (about 1100 ° C. or higher).
Strength) and contributes to the improvement of ductility. Also, about 1
It shows a remarkable effect of improving the creep rupture life in a high temperature range exceeding 100 ° C. In order to obtain these effects, 0.1.
Requires 5% or more. The effect is increased by increasing the dose.
If it exceeds 0%, the effect is almost saturated, so this is set as the upper limit.

The alloy of the present invention may optionally contain the following elements. W: 0.5 to 5.0% W is an element effective for increasing the high temperature creep rupture strength. This effect can be obtained by adding 0.5% or more.
The effect is increased by increasing the amount, but when added in a large amount exceeding 5.0%, the high-temperature tensile ductility is significantly reduced. Preferably,
1.0 to 4.0%.

N: 0.003 to 0.03% N contributes to an improvement in tensile ductility at room temperature. This effect is 0.
Appears when 003% or more is added. The effect increases with increasing amount, but a content of up to 0.03% is sufficient. Also,
In the smelting operation of the alloy, it is difficult to obtain an addition yield exceeding this, and the economics in the smelting operation of the alloy are impaired. Preferably it is 0.004 to 0.02%.

C: 0.1% or less C precipitates at grain boundaries, strengthens the grain boundaries, and increases tensile ductility at high temperatures. The amount required to achieve this effect is 0.1% or less. Exceeding this will impair ductility in the normal temperature range. Preferably, it is 0.01 to 0.05%.

Fe: 3.0% or less Fe is not an essential element in the present invention. This is because the high-temperature strength tends to decrease as the amount increases. 3.
If it exceeds 0%, the adverse effect cannot be ignored. Therefore, the upper limit is 3.0%. Preferably it is 1.0% or less.

The nickel aluminide alloy of the present invention is used as a cast alloy for manufacturing various structural members. For example,
Applying centrifugal casting, radiant tubes, hearth roll sleeves for heating furnaces (roll body members), petrochemical reaction tubes, etc., satisfy the mechanical properties required for these applications, and construct piping. It is possible to satisfy the requirements of weldability required for assembling members and the like. In addition, the powder of the alloy of the present invention can be used as a cladding material for forming a clad structure. The overlaying can be efficiently performed by applying, for example, a plasma powder welding method (ppw method).

[0018]

[Example] (1) Production of test material (1.1) Melting of alloy Alumina crucible (inner diameter 145 x height 2)
56, mm) and melt the alloy under an argon atmosphere. First, nickel is heated and melted, and aluminum is added at the burn-through stage to raise the temperature. A predetermined alloying element was added thereto, and the temperature was adjusted. The dissolution weight is 16 kg.

(1.2) Casting A tubular specimen (outer diameter 137 × wall thickness 19 × length 270, mm) was obtained by centrifugal force casting (atmospheric atmosphere). In the tubular test material (as cast), a macrostructure composed of columnar crystals by directional solidification and partially granular crystals on the inner surface side is observed from the outer surface.

Table 1 shows the chemical composition of each test material. A test piece was prepared from each test material and each physical property was measured. Table 2 shows Vickers hardness Hv (load 98N) and room temperature tensile properties, Table 3 shows high temperature tensile properties (test temperature: 1100 ° C), creep test results (test temperature: 1100 ° C, load: 30 MPa) and weldability test results. Shown respectively.

The results of the weldability test in Table 4 were performed by a bead-on-plate method (welding current: 120 A) in which a plate cut out from the test material was used as a test material and TIG welding was performed on the plate surface. The weldability was evaluated based on the presence or absence of cracks (die check) after welding. The symbols in the column of “Weldability” in Table 4 mean the following evaluations. 〇: Good weldability (no crack) ×: Notable crack generation

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

[Table 3]

In the table, Comparative Examples Nos. 101 to 107 have compositions similar to the present invention, but the content of any element (underlined) deviates from the definition of the present invention, or It is an example containing a certain element. No.108 (0.5% C-0.25% S
i-0.4% Mn-30% Cr-48% Ni-13% W-0.% 2Al-Fe) uses precipitation strengthening and solid solution strengthening, and is widely used as a material for various heating furnaces at a temperature of about 1200 ° C. It is a conventional representative heat-resistant alloy that is practically used. The material of the present invention has a hardness at room temperature and a high temperature range,
It has excellent strength, ductility, and high temperature creep properties and good weldability. The weldability is equivalent to that of a typical high Ni-Cr heat resistant alloy (No. 108).

On the other hand, in the comparative examples, none of the materials had the mechanical properties at room temperature and high temperature of the inventive examples, and the weldability was inferior, because they did not satisfy the component constitution specified in the present invention. ing. In addition, although No.108 (high Ni-Cr heat-resistant alloy) has good weldability, it is inferior in strength, creep rupture life and the like in a high temperature range, and does not reach the physical properties of the alloy of the present invention.

[0027]

The nickel aluminide superalloy of the present invention has good mechanical strength and ductility at room temperature and high temperature, high temperature creep resistance, etc., and also has improved weldability. Therefore, it can be applied, for example, as a constituent material of a radiant tube disposed in a steel heating furnace, a transport roll in the heating furnace, or a reaction tube in the petrochemical industry, and the engineering application of nickel aluminide alloy is expanded. It allows for diversification.

Claims (4)

[Claims] 1. In weight%, Al: 6.0-9.0%, Cr: 2.0-15.0%, Zr: 0.5-3.0%, Fe: 3.0% or less, The balance consists essentially of Ni, Ni_Three Al-based intermetallic compound
-Temperature strength and high-temperature creep with a metal structure containing
Aluminide superb with excellent loop characteristics and weldability
Heat resistant alloy. 2. In weight%, Al: 6.0 to 9.0%, Cr: 2.0 to 15.0%, Zr: 0.5 to 3.0%, W: 0.5 to 5% Fe: 3.0% or less, with the balance substantially consisting of Ni_Three Al-based intermetallic compound
-Temperature strength and high-temperature creep with a metal structure containing
Aluminide superb with excellent loop characteristics and weldability
Heat resistant alloy. 3. In weight%, Al: 6.0-9.0%, Cr: 2.0-15.0%, Zr: 0.5-3.0%, C: 0.1% or less and / Or N: 0.003 to 0.0
3%, Fe: 3.0% or less, the balance being substantially composed of Ni_Three Al-based intermetallic compound
-Temperature strength and high-temperature creep with a metal structure containing
Aluminide superb with excellent loop characteristics and weldability
Heat resistant alloy. 4. Al: 6.0 to 9.0%, Cr: 2.0 to 15.0%, Zr: 0.5 to 3.0%, W: 0.5 to 5% by weight. , C: 0.1% or less and / or N: 0.003 to 0.0
3%, Fe: 3.0% or less, the balance being substantially composed of Ni_Three Al-based intermetallic compound
-Temperature strength and high-temperature creep with a metal structure containing
Aluminide superb with excellent loop characteristics and weldability
Heat resistant alloy.