JP2002069557A - Ni BASED HIGH STRENGTH ALLOY - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonmagnetic alloy material having high strength exceeding 2,000 MPa at room temperature and high temperature stability, having high hardness and high corrosion resistance, also good in workability and high in versatile applicability in an Ni based alloy. SOLUTION: This Ni based high strength alloy has an alloy composition containing, by weight, <=0.1% C, <=2.0% Si, <=2.0% Mn, 30 to 45% Cr and 1.5 to 5% Al, and the balance Ni with inevitable impurities as a fundamental composition and strengthened by the composite precipitation of a γ' phase and an α phase. One or more kinds selected from the elements in the following groups may be added tehreto: (I) one or more kinds selected from Ti, Zr and Hf (in total in the case of two or more kinds): <=3.0%, (II) one or more kinds selected from Nb, Ta and V (in total in the case of two or more kinds): <=3.0%, (III) <=10% Co, <=10% Mo and/or <=10% W so as to satisfy Mo+0.5W: <=10% and (IV) one or more kinds selected from <=5% Cu, <=0.015% B, <=0.01% Mg, <=0.01% Ca and <=0.1% rare earth metals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a Ni-based high-strength alloy. According to the present invention, heat-resistant parts around engine exhaust systems and gas turbines that require high strength and high-temperature stability and high-temperature corrosion resistance, bearings that require high hardness and high corrosion resistance, parts that require high hardness and high corrosion resistance, N, which is suitable as a material for required parts such as shafts and bolts
An i-based alloy is provided.

[0002]

2. Description of the Related Art As a material for parts which are required to be able to maintain high strength and high-temperature corrosion resistance for a long period of time, for example, in parts exposed to high temperatures, such as parts for engine exhaust systems and gas turbines described above. Is the γ 'phase, ie, Ni
₃ (Al, Ti, Nb) or γ ″ phase, ie, Inconel X-750, which is a precipitation strengthened alloy of Ni ₃ Nb, Inc.
Ni-based superalloys such as onel-718 have been employed. However, the room-temperature hardness of this type of Ni-based alloy is at most about HRC40 and the tensile strength is at most 150.
It stops at 0 MPa.

[0003] Parts such as bearings that require high hardness and high corrosion resistance include HRC58 such as JIS SUS440C.
Stainless steel is used for applications requiring non-magnetism because it has low corrosion resistance and is not suitable for corrosive environments, and is naturally non-magnetic. Absent.

A work hardening type austenitic stainless steel disclosed in Japanese Patent Application Laid-Open No. 62-20855 is used for materials such as shafts and bolts that require high strength and non-magnetism. , The level of 1800 MPa is reached, but when the temperature rises, work hardening recovers and the strength decreases.

For this reason, at room temperature, 2000 MPa
Alloys that meet all of the requirements of high strength and high temperature stability, high hardness, high corrosion resistance and non-magnetic properties which have not been realized yet.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide not only the above-mentioned properties, that is, high strength exceeding 2000 MPa at room temperature, high temperature stability, high hardness, high corrosion resistance and non-magnetic properties, but also An object of the present invention is to provide an alloy material having good versatility and high versatility.

[0007]

The Ni-based high-strength alloy of the present invention, which can achieve this object, has a basic alloy composition in which, by weight%, C: 0.1% or less, Si: 2.% or less. 0
%, Mn: 2.0% or less, Cr: 30 to 45% and Al: 1.5 to 5%, the balance being an alloy composition consisting of unavoidable impurities and Ni, γ ′ phase and α It is a Ni-based high-strength alloy that is strengthened by complex precipitation of phases.

[0008] As described above, the γ 'phase is used for strengthening the precipitation of a Ni-based superalloy. In addition to this, a composite precipitation of an α phase mainly composed of Cr provides high strength and high temperature stability. , High hardness, high corrosion resistance and non-magnetic properties. This alloy can be hot-worked, and if it is subjected to a solution heat treatment, it is softened to an HRB of 95 or less. Therefore, it is excellent in cold workability, and is a material with good manufacturability and high versatility.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The Ni-based high-strength alloy of the present invention may contain one or more optional elements belonging to the following groups in addition to the above basic alloy components. I) One or more of Ti, Zr and Hf (in the case of two or more, in total): 3.0% or less; II) One or more of Nb, Ta and V (two or more) III) Co: 10% or less, Mo: 10% or less, and / or W: 10% or less, Mo + 0.5W: 10% or less, and IV) Cu: 5 %, B: 0.015% or less, Mg:
0.01% or less, REM: 0.1% or less, Ca: 0.0
1% or less and REM: one or more of 0.1% or less.

Hereinafter, the operation of each alloy component constituting the basic embodiment of the Ni-based high-strength alloy of the present invention and the reason for limiting the composition range will be described.

C: 0.1% or less, preferably 0.08%
In the following, C acts as a deoxidizing agent at the time of melting, and when there is an element belonging to the group of Ti, Zr and Hf, or an element belonging to the group of Nb, Ta and V, forms a carbide with them. This prevents crystal grain coarsening during solution heat treatment and contributes to strengthening of grain boundaries. 0.1%
The addition exceeding the above lowers the strength and toughness. The upper limit of the preferred content is 0.08%.

Si: 2.0% or less Si is necessary as a deoxidizing agent, but a large amount of Si causes a decrease in strength and toughness. Its limit is 2.0%.
1.0% or less is preferable.

Mn: 2.0% or less Mn, like Si, is also useful as a deoxidizing agent, but excessive addition again causes a decrease in strength and toughness. 2.0% was set as the upper limit. This is also preferably 1.0% or less.

Cr: 30 to 45% Cr is a main element that forms the α phase, and is an important element in that high strength and high hardness can be obtained by complex precipitation of the α phase with the γ ′ phase. is there. Of course, it also contributes to corrosion resistance. These effects cannot be sufficiently obtained with an amount of less than 30%, while an addition of more than 45% causes a reduction in workability. A more preferred range is 32-42%.

Al: 1.5 to 5.0% Al is an important element for forming the γ 'phase, and is also useful for improving high-temperature corrosion resistance. This effect cannot be obtained when the addition does not reach 1.5%, and when the addition amount exceeds 5.0%, the workability deteriorates. The preferred range is 2.0-4.
5%.

In the modified embodiment of the Ni-based high-strength alloy of the present invention, the action of the alloy components of each group arbitrarily added and the reason for limiting the composition range are as follows.

One or more of Ti, Zr and Hf (in the case of two or more, in total): not more than 3.0% These elements are replaced by Al which forms the γ 'phase to form γ'. Since it contributes to solid solution strengthening of the phase and has a function of further increasing the strength of the alloy, it is preferable to add it in combination with Al. However, if the total amount with Al exceeds 7%, the workability deteriorates. Of the three elements, the one that is most effective in improving the strength is Ti.
% Or less. Zr and Hf also have the effect of segregating at crystal grain boundaries and strengthening the grain boundaries. There is an optimum range of the addition amount of Zr and Hf at 0.1% or less.

One or more of Nb, Ta and V (total of two or more): 3.0% or less Nb, Ta and V also have the same mechanism as Ti, Zr and Hf. In other words, by substituting Al for forming the γ 'phase, it contributes to solid solution strengthening of the γ' phase, and has the effect of further increasing the strength of the alloy. However, addition exceeding 3% deteriorates processability. Among these three elements, Nb and Ta have the highest addition effects, and the optimum range of the addition amount is 2% or less. The optimal addition amount of V is 0.
5% or less.

Co: 10% or less, Mo: 10% or less and / or W: 10% or less, Mo + 0.5W: 10
% Or less Co enhances the strength of the alloy by solid solution strengthening. It is also present to increase the precipitation amount of the γ 'phase. However, since Co is an expensive material, it is not advisable to add a large amount of Co, and the practical upper limit is 10%. Mo and W also increase the strength of the alloy by solid solution strengthening. Mo also has a function of improving corrosion resistance. When Mo + 0.5W exceeds 10%,
Impairs workability and hot corrosion resistance. Since both Mo and W are expensive materials, adding a large amount is disadvantageous because it increases the cost of the alloy.

Cu: 5% or less, B: 0.015% or less,
Mg: 0.01% or less, Ca: 0.01% or less and R
EM: One or more of 0.1% or less Cu improves cold workability. In addition, there is a cost that significantly improves the sulfuric acid corrosion resistance. Large additions are undesirable for hot workability and should be limited to no more than 5%. B, Mg and Ca all improve hot workability. B additionally segregates at crystal grain boundaries to strengthen the grain boundaries and also serves to increase creep strength. Mg
And Ca may be added for the purpose of deoxidation and desulfurization during dissolution. In any case, excessive addition lowers the hot workability. Therefore, as a limit of the addition amount, 0.015% for B, and 0.1% for Mg and Ca.
01%. REM increases the oxidation resistance of components used at high temperatures. This effect is mainly obtained through a mechanism of suppressing peeling of the scale that has been in close contact. However, since it is unfavorable for hot workability, the addition is limited to 0.1% or less.

Among the substances that are mixed as impurities, the most likely substance is Fe. Since Fe tends to lower the strength of the alloy and the corrosion resistance at high and normal temperatures, the amount of Fe is reduced as much as possible by examining the raw materials. The acceptable limit is 5%, but we would like to keep it below 3% if possible.

[0022]

EXAMPLES Ni-base alloys having the alloy compositions shown in Table 1 (Example) and Table 2 (Comparative Example) were each melted in a vacuum induction furnace in an amount of 50 kg and cast into ingots.

Table 1 (Part 1) Alloy composition (Example, balance Ni) No. C Si Mn Cr Al Cu, Co Mo, W Ti, Zr, Hf Nb, Ta, V Other 1 0.01 0.12 0.22 37.7 3.9-- ---2 0.02 0.20 0.18 39.6 3.1--Ti: 1.2--Zr: 0.01 3 0.08 0.15 0.23 31.5 4.5--Ti: 0.2 Nb: 0.2-Hf: 0.06 4 0.05 0.04 0.06 38.2 3.7-Mo: 3.8 Ti: 0.6 Nb: 0.2-Ta: 0.1 V: 0.2 5 0.02 1.61 0.32 36.8 3.6-Mo: 2.4 Zr: 0.02 V: 0.1 B: 0.003 W: 2.6 6 0.03 0.17 0.15 42.9 2.1--Ti: 0.1-B: 0.003 Mg: 0.002 7 0.01 0.14 1.50 37.6 4.0 Cu: 2.1-Ti: 0.2-B: 0.003 Hf: 0.05 8 0.01 0.06 0.04 33.4 3.4 Co: 2.1 Mo: 1.1 Ti: 0.8 Nb: 0.4 Mg: 0.002 Ta: 0.2 Ca: 0.001 9 0.06 0.09 0.11 34.6 3.4 Cu: 1.9 Mo: 2.0-Nb: 0.8 B: 0.005 W: 2.2 REM: 0.013 10 0.02 0.13 0.21 35.1 3.8-W: 2.2 Zr: 0.02 Fe: 1.2 B: 0.002 Hf: 0.01 Mg: 0.001 Ca: 0.001 11 0.01 0.12 0.11 36.9 3.5 Cu: 1.6 Mo: 1.9 V: 0.3 Ca: 0.002 Co: 1.2

Table 1 (Part 2) Alloy composition (Example, balance Ni) No. C Si Mn Cr Al Cu, Co Mo, W Ti, Zr, Hf Nb, Ta, V Others 12 0.03 0.25 0.19 32.0 2.3-Mo : 3.2-Nb: 1.8 Fe: 2.1 Ta: 0.3 Ca: 0.002 13 0.02 0.33 0.29 31.8 2.5 Co: 2.5-Ti: 1.5 V: 0.1 B: 0.003 Zr: 0.01 Ca: 0.002 14 0.01 0.18 0.15 34.3 3.1 Cu: 1.2- Ti: 0.7 Nb: 0.1 Mg: 0.002 15 0.01 0.08 0.07 38.1 3.2-Mo: 1.5 Ti: 0.6 Nb: 0.2 Fe: 1.6 W: 1.0 B: 0.002 16 0.05 0.21 0.19 35.6 3.6--Ti: 0.2 B: 0.001 Ca: 0.001 Zr: 0.02 Hf: 0.01 REM: 0.013 17 0.02 0.11 0.12 36.0 3.5-Mo: 2.8 Ti: 0.2 B: 0.003 Hf: 0.01 Mg: 0.001 18 0.03 0.20 0.19 32.5 4.1 Cu: 3.6-Fe: 0.5 19 0.01 0.45 0.36 38.2 3.8 Co: 0.9-Zr: 0.01 Nb: 0.3 Fe: 0.6 V: 0.1 B: 0.002 20 0.01 0.04 0.06 39.3 3.4-Mo: 3.3 Ti: 0.5 Ta: 0.2 B: 0.004 W: 1.7 Mg: 0.002 REM: 0.02 21 0.02 0.06 0.13 34.7 3.4-Mo: 2.9 Ti: 0.6 Nb: 0.4 B: 0.002 Mg: 0.001 Ca0.003

Table 2 Alloy composition (comparative example, balance Fe) No. C Si Mn NiCrAlMoFeTi, Zr, HfNb, Ta, V Other 1 0.03 0.15 0.16 42.3 19.1 0.5 2.9 Balance Ti: 0.8 Nb: 4.9 -Ta: 0.3 2 0.05 0.23 0.56 remaining 16.1 0.9-7.9 Ti: 2.7 Nb: 0.9 B: 0.003 3 0.06 0.51 0.48 remaining 20.2 1.4-Ti: 0.2 Nb: 0.2-Hf: 0.06 4 0.36 0.54 0.60-13.3--remaining- --5 1.11 0.42 0.56-17.4--Remain---6 0.09 0.29 1.41 12.2 18.3--Remain-V: 0.1 N: 0.24 7 0.08 0.38 18.5 2.4 17.8--Remain-N: 0.35 , A known alloy. No.1: Inconel 718 No.2: Inconel X-750 No.3: Nimonic 80A No.4: JIS SUS420J2 No.5: JIS SUS440C

Each ingot was forged and rolled at a temperature in the range of 1200 to 950 ° C. to form a round bar having a diameter of 18 mm. However, Comparative Examples Nos. 6 and 7 were round bars having a diameter of 30 mm. Subsequently, each round bar was subjected to heat treatment or heat treatment + plastic working under the conditions shown in Table 3.

Table 3 Category No. Heat treatment or heat treatment + plastic working Examples 1 to 21 Solution heat treatment (1150 ° C x 1 hour-water cooling) -aging heat treatment (700 ° C x 16 hours-air cooling) Comparative Example 1 Heat treatment (1000 ℃ ℃ 0.5 hours-air cooling)-(720 ℃ x 8 hours-furnace cooling)-(620 ℃ x 8 hours-air cooling) 2 Heat treatment (1050 ℃ x 0.5 hours-water cooling)-(750 ℃ x 16 hours-air cooling) 3 Heat treatment (1050 ° C x 0.5 hours-water cooling)-(750 ° C x 16 hours-air cooling) 4 Heat treatment (950 ° C x 0.5 hours-oil cooling)-(200 ° C x 1 hour-air cooling) 5 Heat treatment (1000 ° C x 0.5 hours) -Oil cooling)-Subzero treatment-(200 ° C x 1 hour-Air cooling) 6 Heat treatment (1050 ° C x 1 hour-Water cooling)-Cold swaging with 80% reduction in area 7 Heat treatment (1050 ° C x 1 hour-Water cooling) -Cold swaging with 80% reduction in area

The alloy of Example No. 2 was subjected to X-ray diffraction analysis. The obtained chart is shown in FIG. In this chart, in addition to the peak of the γ phase, the peaks of the γ ′ phase and the α phase were recognized, confirming that the reinforcement by the composite precipitation was performed.

For each alloy sample, room temperature and 70
Tensile test at 0 ° C., measurement of hardness, measurement of magnetic permeability at room temperature, evaluation of corrosion resistance by spraying with salt water, and continuous oxidation test at 900 ° C. were performed. The test conditions are as follows. [Temperature test at room temperature] Diameter of parallel part of test piece 8mm, distance between evaluation points 3
0mm Conforms to JIS Z2201 [High temperature tensile test] Diameter of parallel part of test piece 8mm, distance between evaluation points 4
0mm Conforms to JIS Z0567 [Hardness] Vickers hardness tester used, Measurement load 5kgf [Permeability] Test specimen size 5 × 5 × 5mm, Vibration sample type magnetometer External magnetic field 100Oe [Salt spray] Specimen width 15mm × Length 25mm x 2m thick
m, the surface is polished with # 320 sandpaper, sprayed with salt water for 100 hours in accordance with JIS Z2371, and evaluated for rusting. [High-temperature continuous oxidation] The test piece is 15 mm wide x 25 mm long x 2 mm thick. , Polish the surface with # 320 sandpaper, JIS Z228
After holding at 900 ° C. for 100 hours in accordance with 1 and the results of evaluation test by weight increase by oxidation are shown in Tables 4 and 5.

Table 4 Test results (Examples) No. Tensile strength Hardness Permeability μ-1 Salt water spray Oxidation weight increase Room temperature 700 ° C Room temperature 700 ° C (emu) After appearance (mg / cm2) 1 2153 1842 647 542 542 Less than 0.001 No rust 0.2 2 2213 1922 663 568 Less than 0.001 No rust 0.23 2198 1823 650 538 Less than 0.001 No rust 0.1 4 2251 1906 672 566 Less than 0.001 No rust 0.5 5 2170 1891 654 551 Less than 0.001 No rust 0.4 6 2148 1814 642 523 Less than 0.001 No rust 0.3 7 2166 1882 653 549 Less than 0.001 No rust 0.18 2125 1817 635 538 Less than 0.001 No rust 0.29 2164 1875 646 547 Less than 0.001 No rust 0.2 10 2137 1838 641 542 Less than 0.001 No rust 0.3 11 2202 1889 658 550 Less than 0.001 No rust 0.3 12 2076 1743 615 505 Less than 0.001 No rust 0.6 13 2081 1755 619 511 Less than 0.001 No rust 0.4 14 2103 1801 624 522 Less than 0.001 No rust 0.2 15 2179 1908 657 556 Less than 0.001 No rust 0.5 16 2130 1810 639 532 Less than 0.001 No rust 0.2 17 2142 1346 642 544 Less than 0.001 No rust 0.3 18 2159 1817 651 533 Less than 0.001 No rust 0.1 19 2185 1898 658 557 Less than 0.001 No rust 0.2 20 2198 1905 660 565 Less than 0.001 No rust 0.5 21 2173 1886 648 551 Less than 0.001 No rust 0.4

Table 5 Test Results (Comparative Example) No. Tensile Strength Hardness Permeability μ-1 Salt Spray Oxidation Weight Increase Room Temperature 700 ° C. Room Temperature 700 ° C. (emu) Appearance (mg / cm2) 1 1368 1101 443 342 Less than 0.001 No rust 1.5 2 1224 966 385 297 Less than 0.001 No rust 1.2 3 1087 790 342 248 Less than 0.001 No rust 0.7 4 2152 609 607 197 197 3.47 Rust on entire surface 38.2 5 2246 693 687 226 3.32 Rust on entire surface 40.8 6 1811 456 512 158 0.004 No rust 6.3 7 1924 468 529 169 0.003 Slight rust 26.4

[0032]

As described above, the Ni-based high-strength alloy of the present invention has a strength of 20% at room temperature by utilizing the strengthening by the composite precipitation of the γ ′ phase and the α phase.
While ensuring high strength exceeding 00 MPa, it is stably maintained even at high temperatures, and there is little decrease in strength with increasing temperature. The hardness is high enough to exceed HV600 at room temperature, and does not decrease much even at high temperatures. It also has excellent corrosion resistance at normal and high temperatures, and withstands particularly high-temperature oxidizing atmospheres. Moreover, this alloy is non-magnetic.

Therefore, the Ni-based high-strength alloy of the present invention
Various parts required to have some or all of these characteristics, typically parts for the engine exhaust system and gas turbine, parts for bearings, shafts and bolts, etc. There are uses.

[Brief description of the drawings]

FIG. 1 is a chart obtained by performing an X-ray diffraction analysis on an alloy of Example No. 2 of the present invention.

Claims (5)

[Claims] C .: 0.1% by weight or less, Si:
2.0% or less, Mn: 2.0% or less, Cr: 30 to 45
% And Al: Ni-based high-strength alloy containing 1.5 to 5%, the balance having an alloy composition consisting of unavoidable impurities and Ni, and strengthened by composite precipitation of γ ′ phase and α phase. 2. In addition to the alloy component specified in claim 1,
One, two or more of Ti, Zr and Hf (in the case of two or more, in total): has an alloy composition containing 3.0% or less, and is strengthened by the composite precipitation of γ ′ phase and α phase. Ni-based high-strength alloy. 3. In addition to the alloy components as defined in claim 1 or 2, one or more of Nb, Ta and V (in the case of two or more, in total): not more than 3.0%. A Ni-based high-strength alloy having an alloy composition and strengthened by composite precipitation of a γ 'phase and an α phase. 4. In addition to the alloy components defined in any one of claims 1 to 3, Co: 10% or less, Mo: 10% or less and / or W: 10% or less, Mo + 0.5
W: has an alloy composition containing 10%, and γ ′
Ni-base high-strength alloy strengthened by combined precipitation of α and α phases. 5. In addition to the alloy components defined in any one of claims 1 to 4, Cu: 5% or less, B: 0.015%
Hereinafter, it has an alloy composition containing one or more of Mg: 0.01% or less, Ca: 0.01% or less, and REM: 0.1% or less, and composite precipitation of γ ′ phase and α phase Ni-based high-strength alloy reinforced by