JPS6134497B2 - - Google Patents

Description

[Detailed description of the invention]

This invention has excellent hot and cold workability,
The present invention relates to a solid solution strengthened Ni-based heat-resistant alloy that has high tensile strength and fatigue strength at high temperatures and excellent oxidation resistance. Ni-based heat-resistant alloys such as Hastelloy However, in recent years, there has been a demand for new materials that can be used under even harsher conditions, such as in the various high-temperature devices mentioned above. In order to meet these demands, various heat-resistant alloys have been developed and are put into practical use as superalloys. On the other hand, the various types of equipment mentioned above are currently becoming more and more efficient, and along with this, the properties required of materials, such as oxidation resistance, high temperature strength, high temperature and high cycle resistance, hot and cold workability, etc. We are in a situation where something sophisticated is required. Among these required properties, high temperature strength, high temperature high cycle fatigue strength, and hot and cold workability generally tend to conflict in terms of alloy design. For example, solid solution strengthened nickel-based heat-resistant alloy, which is one of the conventionally used Ni-based superalloys,
Ni-Cr-Mo-Fe alloys represented by Hastelloy X and other Ni-Cr-Mo-Co alloys have excellent hot and cold workability, and are fully satisfactory in this respect. However, there is a tendency that they do not necessarily satisfy the recent severe demands for high-temperature properties such as high-temperature strength and high-temperature high-cycle fatigue strength. From the above-mentioned viewpoints, the inventors of the present invention sought to obtain a heat-resistant alloy that is extremely excellent in hot and cold workability and oxidation resistance, and that is particularly satisfactory in tensile strength and fatigue strength at high temperatures. As a result of various studies, (a) the high-temperature strength of Ni-Cr alloys with excellent oxidation resistance and hot and cold workability, especially Ni-Cr alloys containing 20.0 to 26.0% Cr, was determined. Although Mo and W are included for the purpose of improving the strength, the strength at room temperature also increases, which impairs cold workability into complex shapes. However, this
Considering the combination of Mo and W and adjusting the content of each and the total amount of both, the Ni-Cr
It is possible to further improve the high temperature strength of the alloy without significantly impairing its cold workability. Moreover, this effect is enhanced more by the combined inclusion of Mo and W than by Mo alone. (b) The inclusion of Ca in Ni-Cr alloys improves high-temperature properties and hot workability, and also limits the upper limits of Mo and W contents, especially when constrained by cold workability. Being able to expand. (c) High-temperature strength can be increased without impairing cold workability by combining a Ni-Cr alloy containing Mo and W with a well-balanced content of Co. (d) When Al and Ti are further added to a Ni-Cr alloy containing Mo, W, and Ca, fine intermetallic compounds Ni ₃ (Al, Ti) are uniformly dispersed and precipitated in the matrix. This makes it possible to further increase high-temperature strength. (e) Add Y and rare earth elements such as Ce and La to (a) above.
When added to the Ni-Cr alloy shown in (d),
Further improvement in oxidation resistance and hot workability. (f) Nb,
When V and Ta are included, both interact with C to precipitate carbides, refine crystal grains after recrystallization, and improve high-cycle fatigue strength at high temperatures. We have come to the knowledge shown in (a) to (f) above. Therefore, this invention was made based on the above knowledge, and in weight% (hereinafter, % means weight%): C: 0.001 to 0.15%, Ca: 0.0005 to 0.05%, Cr: 20.0 ~26.0%, preferably 20.0~24.0
%, Co: 4.7 to 9.4%, preferably 6.5 to 9.4%, Mo: 5.0 to 16.0%, preferably 8.0 to 10.0%, W: 0.5 to 4.0%, (However, Mo + W: 9.0 to 16.5%, preferably 10.0 ~13.5%), Al: 0.3~1.5%, preferably 0.6~1.5%, Ti: 0.1~1.0%, and if necessary, Y: 0.001~
Contains one or two of 0.15% and rare earth elements: 0.001 to 0.15%, and if necessary,
Contains one or more of Nb, V, and Ta: 0.01 to 1.0%, with the remainder consisting of Ni and unavoidable impurities, and has high temperature strength, hot and cold workability It is characterized by being a Ni-based heat-resistant alloy with excellent both oxidation resistance and oxidation resistance. Then, in the alloy of this invention, C, Ca,
Cr, Co, Mo, W, Al, Ti, Y, rare earth elements,
The reason why the composition ranges of Nb, V, and Ta components are limited as described above will be explained. (a) The C component acts as a deoxidizing agent in the melting of the alloy, and therefore requires a minimum amount of at least 0.001% remaining in the alloy, but if it remains in excess of 0.15%, it will act as a solid solution strengthening element in the matrix. is
Mo and W together form carbides in excess, resulting in loss of high-temperature strength, so the content should be reduced.
It was limited to 0.001-0.15%. (b) Ca Ca component is necessary for improving hot and cold workability, tensile properties at high temperatures, and fatigue strength at high temperatures, and if its content is less than 0.0005%, it will not be effective. On the other hand, if the content exceeds 0.05%, hot workability will be significantly impaired, so the content was limited to 0.0005 to 0.05%. (c) Cr The Cr component has the effect of forming a strong oxide film at high temperatures and improving oxidation resistance.
If the content is less than 20.0%, the desired effect cannot be obtained, while if the content exceeds 26.0%, the high-temperature strength will be particularly reduced. Limited. Note that in order to maintain high-temperature strength at a higher level, it is desirable to set the upper limit of Cr to 24.0%. (d) Co The Co component has the effect of improving high-temperature strength, but if its content is less than 4.7%, the desired effect cannot be obtained, while if it is contained in excess of 9.4%, the room-temperature strength is increased. becomes significantly higher,
Therefore, since cold workability deteriorates significantly, its content was limited to 4.7 to 9.4%. Note that the best high-temperature strength is obtained when the Co content is 6.5 to 9.4%. (e) Mo and W Both Mo and W components are major elements for improving high-temperature strength. In particular, W has a remarkable effect on improving high-cycle fatigue strength, but Mo and W components are When W is less than 5.0% and less than 0.5%, respectively, no remarkable effect is exhibited in improving high-temperature strength. In particular, when W is less than 0.5%, no remarkable effect is observed on improving high-cycle fatigue strength. On the other hand, Mo and W components are each 16.0%.
If the content exceeds 4.0%, cold workability will be significantly impaired. However, within a certain limited range of these contents, the combination of Mo and W can maintain higher high-temperature strength and a certain level of cold workability than each of them alone. . That is, Mo is 5.0 to 16%, W is 0.5%
Even if the content of ~4.0% is satisfied, (Mo + W)
If it is less than 9.0, the desired effect of improving high-temperature strength will not be obtained. On the other hand, if (Mo + W) exceeds 16.5%, cold workability will be significantly reduced. %, W content
After setting it as 0.5 to 4.0%, the total amount of (Mo + W): 9.0
~16.5% must be satisfied. In addition,
The best high temperature strength is obtained when Mo: 8.0 to 10.0% and W: 0.5 to 4.0% are contained, and (Mo+W): 10.0 to 13.5% is satisfied. (f) Al and Ti Al and Ti combine with Ni to form fine Ni ₃
As an intermetallic compound of (Al, Ti), it is uniformly dispersed in the matrix and has the effect of further improving high-temperature strength, but when the Al and Ti components are less than 0.3% and less than 0.1%, respectively, they have a remarkable effect on improving high-temperature strength. On the other hand, if Al and Ti components exceed 1.5% and 1.0%, respectively, cold workability will be significantly impaired and embrittlement will occur. Al content: 0.3~1.5%, Ti: 0.1~1.0%
limited to. In addition, Al: 0.6-1.5% and Tf:
The best high temperature strength is obtained when the content is 0.1 to 1.0%. (g) Y and rare earth elements Y and rare earth components such as Ce and La have the uniform effect of further improving oxidation resistance and hot workability, but their contents vary depending on their content.
If the content is less than 0.001%, the desired effect cannot be obtained. On the other hand, if the content exceeds 0.15%, the hot workability is particularly reduced. 0.15
%. (h) Nb, V and Ta Nb, V and Ta components all interact with C to precipitate carbides and make crystal grains finer after recrystallization, further improving high cycle fatigue strength especially at high temperatures. Although it has an even effect of improving
If its content is less than 0.01%, the desired effect cannot be obtained;
If it exceeds 1.0%, there is a significant decrease in oxidation resistance, so the content should be reduced to 0.01 to 1.0%.
%. Next, the Ni-based heat-resistant alloy of the present invention will be explained using examples. Using an ordinary vacuum melting furnace, prepare molten metals having the compositions shown in Table 1, diameter: approx.
Cast into an ingot with dimensions of 60mm x height: 200mm, and hot forged and hot rolled to a plate thickness: 4
mm, then cold-rolled to a plate thickness of 2 mm, and finally held at a temperature of 1150-1200°C for 20 minutes and then subjected to solution treatment under water quenching conditions to adjust the grain size to ASTM grain size number: approximately 6. By doing this, the present invention alloys 1 to 23, comparative alloys 1 to 16, and Hastelloy
was manufactured. Next, for the purpose of evaluating the cold workability of the various alloys mentioned above, thickness: 2 mm x width: 20 mm x length:
Using a test piece with a size of approximately 150 mm, a close bending test was conducted at room temperature, bending factor = 0, and bending angle: 180°, and the presence or absence of cracks was observed after the test. In addition, for those that did not cause cracking in the close contact bending test, we conducted a high temperature tensile test at 800°C, an oxidation resistance test at 950°C, and
A high cycle fatigue test was conducted at 600°C, and the oxidation weight gain was measured in the oxidation resistance test, and the number of repetitions until breakage was measured at a load of 38 Kg/mm ² in the high temperature high cycle fatigue test. These measurement results are also shown in Table 1.

【table】

[Table] From the results shown in Table 1, Comparative Alloys 1 to 16 in which one of the constituent components (indicated with an asterisk in Table 1) is outside the scope of this invention.
All of these alloys are inferior in at least one of the properties of high-temperature altitude and high-temperature high-cycle fatigue strength, whereas all of the invention alloys 1 to 23 have excellent cold fatigue strength equivalent to Hastelloy X. It is clear that it has workability and exhibits properties that are far superior to Hastelloy X in terms of cold workability, high-temperature tensile properties, oxidation resistance, and high-temperature high-cycle fatigue strength. As mentioned above, the Ni-based heat-resistant alloy of the present invention is
It has excellent high-temperature strength, hot and cold workability, and oxidation resistance, so it can be processed into complex shapes such as gas turbine combustors and other high-temperature equipment for prime movers. Furthermore, it is suitable for manufacturing parts that require strength at high temperatures, high cycle fatigue strength, and excellent oxidation resistance.

Claims (1)

[Claims] 1 C: 0.001-0.15%, Ca: 0.0005-0.05%, Cr: 20.0-26.0%, Co: 4.7-9.4%, Mo: 5.0-16.0%, W: 0.5-4.0%, Al : 0.3 to 1.5%, Ti: 0.1 to 1.0%, (however, Mo+W: 9.0 to 16.5%), Ni and unavoidable impurities: the remainder (more than % by weight). . 2 C: 0.001-0.15%, Ca: 0.0005-0.05%, Cr: 20.0-26.0%, Co: 4.7-9.4%, Mo: 5.0-16.0%, W: 0.5-4.0%, Al: 0.3-1.5%, Ti: 0.1~1.0%, (Mo+W: 9.0~16.5%), Y: 0.001~0.15% and rare earth elements: 0.001~
1. A Ni-based heat-resistant alloy characterized by having a composition consisting of 0.15% of one or two types of porosity, the remainder of Ni and unavoidable impurities (at least % by weight). 3 C: 0.001-0.15% Ca: 0.0005-0.05%, Cr: 20.0-26.0%, Co: 4.7-9.4%, Mo: 5.0-16.0%, W: 0.5-4.0%, Al: 0.3-1.5%, Ti : 0.1 to 1.0%, (Mo+W: 9.0 to 16.5%), One or more of Nb, V, and Ta: 0.01 to 10%, Ni and unavoidable impurities: Remaining, (More than % by weight) A Ni-based heat-resistant alloy characterized by having a composition consisting of: 4 C: 0.001-0.15%, Ca: 0.0005-0.05%, Cr: 20.0-26.0%, Co: 4.7-9.4%, Mo: 5.0-16.0%, W: 0.5-4.0%, Al: 0.3-1.5%, Ti: 0.1~1.0%, (Mo+W: 9.0~16.5%), Y: 0.001~0.15% and rare earth elements: 0.001~
Must have a composition consisting of one or two of 0.15%, one or more of Nb, V, and Ta: 0.01 to 1.0%, and the remainder of Ni and unavoidable impurities (not less than % by weight). A Ni-based heat-resistant alloy characterized by: