JPH0338329B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Applications The most effective way to increase the output and thermal efficiency of gas turbines used in jet engines and power generation equipment is to increase the temperature of the combustion gas. For this purpose, a blade material with high high-temperature creep rupture strength is required. The present invention relates to a nickel-based heat-resistant alloy dispersed in Yttriya particles and γ' phase precipitation strengthened, which can be effectively used in these applications and has excellent creep rupture strength at high temperatures. Prior Art As an existing alloy that has excellent fracture strength at high temperatures, there is MA-6000 (manufactured by INCO, USA, composition listed below) alloy. MA-6000 alloy is produced by mechanically mixing elemental powders, alloy powders, and Ittria described below, extrusion molding, and zone annealing heat treatment (the molded material is heated several times in a furnace with a maximum temperature of 1232°C and a temperature gradient). It is produced by heat treatment at a moving speed of cm/h. And the base alloy of the obtained alloy is γ
It is a Ni-based γ′ phase precipitation-strengthened alloy containing a γ′ phase and a γ′ phase, and is dispersion strengthened by fine particles of Ittriya. The creep rupture strength of this MA-6000 alloy in the high temperature range is superior to that of ordinary casting and single crystal alloys, but due to the alloy design, it is not sufficiently solid solution strengthened, especially with chromium and high melting point metals. There was a problem with the balance of the (W, Ta) contents. The present inventors first used a base alloy containing particularly less Cr and more W and Ta than the MA-6000 alloy, and after extrusion molding with Ittriya,
We have developed that heat treatment at 1260-1370℃ results in excellent creep rupture strength. (Special request 1986
-168761) As a result of further research using the same alloy base material, it was found that when zone annealing heat treatment is performed at the highest temperature within the range of hardness softening temperature to solidus temperature, it has excellent creep rupture strength with a coarse recrystallized structure. It was successfully developed that a nickel-based heat-resistant alloy with precipitation-strengthened γ′ phase dispersed with Ittria particles could be obtained. (Japanese Patent Application No. 60-238616) Purpose of the Invention The present invention uses the composition of the γ' phase and γ phase of the base alloy developed by the present inventors, and changes the quantitative ratio of the γ' phase and γ' phase. The object of the present invention is to provide a nickel-based heat-resistant alloy with Yttria particle-dispersed γ' phase precipitation strengthening which has even better creep rupture strength in a high temperature range by designing an alloy with Yttria particles dispersed therein by mechanical alloying. Structure of the Invention The present inventors used the composition of the γ′ phase and the γ phase of the base alloy developed by the present inventors, and determined the quantitative ratio of the γ′ phase.
We designed an alloy with 35 vol% and added grain boundary strengthening elements Zr, B, C and dispersed oxide yttriya (Y ₂ O ₃ ).
is added, oxides are dispersed using a mechanical alloying method, and zone annealing heat treatment is performed in a furnace with a maximum temperature between the hardness softening temperature and the solidus temperature. It has been found that it is possible to obtain a nickel-based heat-resistant alloy dispersed in Yttriya particles and strengthened by precipitation of the γ' phase. The present invention was completed based on this knowledge. The gist of the present invention is that in weight %, Al2.5-3.7,
Co10.3~11.1, Cr6.8~8.0, Ti0.5~0.7, Ta3.2~
4.3, W13.0~13.4, Zr0.02~0.2, Mo2.2~2.6,
C0.001~0.1, B0.001 _~ 0.02, Ittriya ( _Y2O3 )
0.5 to 1.7, with the balance being Ni, which is a precipitation-strengthened nickel-based heat-resistant alloy with yttria particle-dispersed γ' phase. In addition, the present invention provides elemental powders having this composition (carbonyl Ni, carbonyl Ni,
Co, Cr, Ta, W, Mo), alloy powder (Ni-Al, Ni
- Ti-Al, Ni-Zr, Ni-B) and Ittriya fine powder are mechanically mixed to form a composite powder, this composite powder is sealed in an extrusion can and extrusion molded, and the molded product is softened in hardness. Zone annealing heat treatment with maximum temperature within the range of temperature to solidus temperature reduces the GAR of the grains.
The present invention also provides a method for producing a nickel-based heat-resistant alloy having a coarse recrystallized structure with a diameter of 20 mm or more and a short axis diameter of 0.1 mm or more. The reasons for limiting the effects of the compositional components, compositional ratios, and processing conditions for obtaining a coarse recrystallized structure in the heat-resistant alloy of the present invention are as follows. Al is an element necessary to generate the γ′ phase,
In order to sufficiently precipitate the γ' phase, it is necessary to contain 2.5% by weight or more. However, in alloys that are sufficiently solid solution strengthened with W and Mo, such as the alloy of the present invention, if Al exceeds 3.7% by weight, the amount of γ' phase increases too much and the toughness decreases.
~3.7% by weight is required. Co dissolves in the γ phase and γ' phase and acts to strengthen these phases. If the amount of Co is less than 10.3% by weight, the reinforcement will not be sufficient, and the amount will be 11.1% by weight.
10.3 to 11.1, since its strength decreases when it exceeds
It needs to be in weight percent. Cr acts to improve sulfidation resistance. If the amount is less than 6.8% by weight, the above effects cannot be obtained when used at temperatures above 1000°C for a long time. If the amount exceeds 8.0% by weight, harmful phases such as α phase and μ phase will be generated and the creep rupture strength will decrease.
It is necessary that the content be 6.8 to 8.0% by weight. W forms a solid solution in the γ phase and γ' phase and significantly strengthens these phases. For this purpose, it is necessary that the content be 13.0% by weight or more. However, if it exceeds 13.4% by weight, the amount of γ' phase decreases, and the strength deteriorates on the contrary. Mo acts to precipitate carbides at grain boundaries. If the amount is less than 2.2% by weight, sufficient carbides cannot be precipitated at the grain boundaries, the grain boundaries become weak, and grain boundary fracture occurs before the base material exhibits sufficient ductility. If the amount exceeds 2.6% by weight, coarse carbides will accumulate at the grain boundaries during heat treatment, significantly weakening the grain boundary strength.
It needs to be in weight percent. Most of Ti dissolves in solid solution in the γ' phase and strengthens the γ' phase, and also increases the amount of the γ' phase to strengthen it. For this purpose, the content is required to be 0.5% by weight or more, but if it exceeds 0.7% by weight, a μ phase is formed and the creep rupture strength is reduced, so the content is required to be 0.5 to 0.7% by weight. Most of Ta dissolves in the γ' phase, significantly strengthening the solid solution and improving the toughness of the γ' phase. To obtain this effect, 3.2% by weight or more is required. However, if it exceeds 4.3% by weight, harmful precipitates such as σ phase will occur and the creep rupture life will decrease.
~4.3% by weight is required. C forms three types of carbides: MC type, M ₂₃ C ₆ type, and M ₆ C type, and mainly acts to strengthen the grain boundaries of the alloy crystals. To obtain this effect, C must be 0.001% by weight.
The above is necessary. However, if the amount exceeds 0.1% by weight, harmful carbides will precipitate in the form of a film at the grain boundaries during secondary recrystallization, so it is necessary to range from 0.001 to 0.1% by weight. B segregates at grain boundaries, improves grain boundary strength at high temperatures, and functions to increase creep rupture strength and fracture elongation. To achieve this effect, 0.001% by weight
The above is necessary. However, if the amount exceeds 0.02% by weight, harmful borides that inhibit grain growth will precipitate in the form of a film at grain boundaries during secondary recrystallization.
It is necessary that the amount is 0.001 to 0.02% by weight. Like B, Zr acts to strengthen grain boundaries. In order to obtain this effect, 0.02% by weight or more is required.
However, if the amount exceeds 0.2% by weight, intermetallic compounds will be generated at the grain boundaries, which will actually reduce the creep rupture strength, so the content should be 0.02 to 0.2% by weight. Ittriya improves high-temperature creep strength when uniformly dispersed in the base material. Its amount is 0.5% by weight
If it is less than that, the effect is not sufficient. If the amount exceeds 1.7% by weight, the strength will deteriorate, so
It is necessary that the content is 0.5 to 1.7% by weight. The remainder of the components is Ni. Carbonyl Ni, Co,
Elemental powders of Cr, Ta, W, Mo or Ni-Al,
A composite powder is made by mechanically mixing Ni-Ti-Al, Ni-Zr, Ni-B alloy powder and Ittriya fine powder. This composite powder is sealed in an extruded can, for example, a mild steel can, and molded. The GAR of the crystal grains (the ratio of the crystal grain size in the long axis (extrusion direction) and short axis direction of the crystal grains (referred to as "GAR") is 20
If the creep strength is above 20, the creep strength will be high, but in order to obtain a coarse recrystallized structure with a short axis diameter of 0.1 mm or more, it is necessary that the extrusion conditions and zone annealing conditions are appropriate. Extrusion conditions such as extrusion temperature and extrusion ratio affect the recrystallized structure after zone annealing. Extrusion processing is not possible when the extrusion temperature is less than 1000℃,
Extrusion jams occur. However, the extrusion temperature is 1080℃
When the GAR of the recrystallized structure after zone annealing exceeds
Since it becomes smaller than 20 and the creep strength becomes lower,
The extrusion temperature needs to be in the temperature range of 1000-1080°C. If the extrusion ratio is less than 12, the degree of extrusion is insufficient and a good recrystallized structure cannot be obtained, the GAR is less than 20, and the creep strength is reduced. When the extrusion ratio is 12 or more, the degree of workability is sufficient, the GAR of the recrystallized structure after zone annealing is also 20 or more, and the creep strength is high. In zone annealing heat treatment, conditions such as the maximum temperature of the furnace, the moving speed of the forming material, and the temperature gradient affect the recrystallized structure. If the maximum temperature of the molded material is lower than the hardness softening temperature (see Figure 1), recrystallization will not occur, an extrusion texture will remain, and the creep strength will be low. When the maximum temperature of the molded material exceeds the solidus temperature, partial melting occurs,
The structure becomes non-uniform and the creep strength decreases.
Therefore, if the maximum temperature of the molded material is within the range of hardness-softening to solidus temperature of the molded material, coarse recrystallized grains with a minor axis diameter of 0.1 mm or more can be obtained. The higher the temperature gradient of the molded material, the larger the GAR of the crystal grains.
When it is less than ℃/cm, the structure has a GAR smaller than 20 and the creep strength becomes low. Therefore,
It is necessary that the temperature gradient is 200°C/cm or more. If the moving speed of the molded material exceeds 200 mm/h, sufficient time will not be obtained for the structure at the center of the molded material to undergo recrystallization, resulting in a non-uniform structure and low creep strength. Moreover, when the speed becomes smaller than 20 mm/h, the minor axis diameter of the crystal grains increases, but the GAR
It becomes less than 20, and the creep strength becomes low. Therefore, the moving speed of the molding material must be in the range of 20 to 200 mm/h. Under the above conditions, extrusion processing and zone annealing heat treatment result in the precipitation of an Ittriya particle-dispersed γ' phase with a large GAR of 20 or more and a structure consisting of coarse recrystallized grains with a minor axis diameter of 0.1 mm or more. A reinforced nickel-based heat-resistant alloy is obtained. In addition, Figure 1 shows the annealing temperature and hardness (Hv) in which the molded material was annealed for 1 hour under the specified annealing temperature conditions, air-cooled, and then the micro-Vickers hardness (Hv) was measured.
FIG. Example 1 Carbonyl Ni powder of 3 to 7 μm, Cr powder of -200 mesh as elemental powder, W of -325 mesh,
Ta, Mo, Co powder as alloy powder, -200 mesh Ni-46% Al powder, Ni-28% Ti-15% Al powder,
Ni-30% Zr powder, Ni-14% B powder as oxides
Using Y ₂ O ₃ of 20 nm, the composition was prepared to have the composition of TMO-9 shown in Table 1.

[Table] This was mechanically mixed in an Ar atmosphere for 50 hours. Note that C is contained in the carbonyl Ni powder. The weight ratio of the steel balls and raw material powder during mechanical mixing was 50 kg:3 kg. The obtained mixed powder was filled into a mild steel can and heated at 400℃ for 2 hours.
After being degassed for over 1 hour under a vacuum of ×10 ^-3 mmHg, it was sealed. After holding this at 1050° C. for 2 hours, it was extruded using an extruder at an extrusion ratio of 15:1 and a ram speed of 400 mm/sec. This molded material was moved at a speed of 100 mm/h in a high frequency heating furnace with a water-cooled jacket at a maximum temperature of 1300°C. The temperature gradient of the molded material at that time is 300
It was ℃/cm. The recrystallized grain size is 0.1mm×
It was several centimeters long and the GAR was over 20. In this way, a nickel-based heat-resistant alloy with Yttriya particle-dispersed γ' phase precipitation strengthened alloy was obtained. In addition, sample numbers 3 and 4 in Table 2 were further heated at 1300℃30
Heat treatment was performed for 4 hours at AC + 1080°C for 20 hours at AC + 870°C. The creep properties of these alloys were as shown in Table 2.

[Table] Table 3 shows the creep characteristics of the conventional MA-6000 alloy.

[Table] Comparing Tables 2 and 3, 1050℃×16Kgf/mm ²
It can be seen that the alloy of the present invention has a rupture life approximately 4 times that of MA-6000 under the creep conditions of , which is an improvement. Effects of the Invention According to the heat-resistant alloy of the present invention, by setting the γ phase and γ′ phase in a specific ratio according to its component composition, and in particular using specific zone annealing conditions, the GAR of coarse grains can be reduced.
This has an excellent effect that the creep rupture life and elongation are extremely superior to those of conventional materials.

[Brief explanation of drawings]

The drawing is a diagram showing the relationship between annealing temperature and hardness (Hv), in which the micro-Vickers hardness (Hv) was measured after an extruded material of the present invention was annealed at a predetermined temperature for 1 hour and cooled in air.

Claims (1)

[Claims] 1% by weight: Al: 2.5-3.7 Co: 10.3-11.1 Cr: 6.8-8.0 Ti: 0.5-0.7 Ta: 3.2-4.3 W: 13.0-13.4 Zr: 0.02-0.2 Mo: 2.2- 2.6 C: 0.001 to 0.1 B: 0.001 to 0.02 Ittria (Y ₂ O ₃ ): 0.5 to 1.7 Balance: Ni A nickel-based heat-resistant alloy dispersed in Ittria particles and strengthened by γ' phase precipitation. 2 Carbonyl Ni, Co, Cr, Ta, W and Mo
Single element powder, Ni-Al, Ni-Ti-Al, Ni-Zr
and Ni-B alloy powder, and further ittria (Y ₂ O ₃ ) fine powder are mechanically mixed to form a composite powder, this composite powder is sealed in an extrusion can and extruded, and the molded product is adjusted to hardness and softening temperature. Zone annealing heat treatment with the highest temperature within the range of ~solidus temperature and grain
GAR is 20 or more, has a coarse recrystallized structure with a minor axis diameter of 0.1 mm or more, and in weight%, Al: 2.5 to 3.7 Co: 10.3 to 11.1 Cr: 6.8 to 8.0 Ti: 0.5 to 0.7 Ta: 3.2 to 4.3 W: 13.0 to 13.4 Zr: 0.02 to 0.2 Mo: 2.2 to 2.6 C: 0.001 to 0.1 B: 0.001 to 0.02 Ittria (Y ₂ O ₃ ): 0.5 to 1.7 Balance: Forms an alloy with a composition of Ni A method for producing a nickel-based heat-resistant alloy with yttria particle-dispersed γ' phase precipitation strengthened alloy.