Patent Application
20200172997
The invention relates to a high-temperature nickel-base alloy.
The material C263 (Nicrofer 5120 CoTi) is used as a material for heat shields in turbochargers or motor-vehicle engines, among other purposes. Within the turbocharger, the heat shield separates the compressor side from the turbine side and is impacted directly by the hot exhaust-gas flow. Since the exhaust-gas temperatures, especially in the internal-combustion engines, are becoming increasingly higher, failure of the structural parts may occur, for example in the form of deformations, which leads to a considerable power loss of the turbocharger.
The exhaust-gas temperatures may be as high as 1050° C., wherein the temperatures occurring at the heat shield range from approximately 900 to 950° C. At these temperatures, the C263 material is no longer creep-resistant. The general composition of the material C263 is given as follows (in wt %): Cr 19.0-21.00, Fe max. 0.7%, C 0.04-0.08%, Mn max. 0.6%, Si max. 0.4%, Cu max. 0.2%, Mo 5.6-6.1%, Co 19.0-21.0%, Al 0.3-0.6%, Ti 1.9-2.4%, P max. 0.015%, S max. 0.007%, B max. 0.005%.
DE 100 52 023 C1 discloses an austenitic nickel-chromium-cobalt-molybdenum-tungsten alloy containing (in mass %) C 0.05-0.10%, Cr 21-23%, Co 10-15%, Mo 10-11%, Al 1.0-1.5%, W 5.1-8.00, Y 0.01-0.1%, B 0.001-0.01%, Ti max. 0.5%, Si max. 0.5%, Fe max. 2%, Mn max. 0.5%, Ni the rest, including unavoidable smelting-related impurities. The material may be used for compressors and turbochargers of internal-combustion engines, structural parts of steam turbines, structural parts of gas-turbine and steam-turbine power plants.
EP 1 466 027 B1 discloses a high-temperature-resistant and corrosion-resistant Ni—Co—Cr-alloy containing (in wt %): Cr 23.5-25.5%, Co 15.0-22.0%, Al 0.2-2.0%, Ti 0.5-2.5%, Nb 0.5-2.5%, up to 2.0% Mo, up to 1.0% Mn, Si 0.3-1.0%, up to 3.0% Fe, up to 0.3% Ta, up to 0.3% W, C 0.005-0.08%, Zr 0.01-0.3%, B 0.001 up to 0.01%, up to 0.05% rare earths as mischmetal, Mg+Ca 0.005-0.025%, optionally up to 0.05% Y, the rest Ni and impurities. In the temperature range between 530 and 820° C., the material can be used as exhaust valves for diesel engines and also as pipes for steam boilers.
In U.S. Pat. No. 6,258,317 B1, an alloy is described that can be used for structural parts of gas turbines at temperatures up to 750° C. and that contains (in wt %): Co 10-24%, Cr 23.5-30%, Mo 2.4-6%, Fe 0-9%, Al 0.2-3.2%, Ti 0.2-2.8%, Nb 0.1-2.5%, Mn 0-2%, up to 0.1% Si, Zr 0.01-0.3%, B 0.001-0.01%, C 0.005-0.3%, W 0-0.8%, Ta 0-1%, the rest Ni and unavoidable impurities.
The task of the invention is to change a material on the basis of C263 with respect to its composition in such a way that the stability of the strength-increasing phase is shifted to higher temperatures. At the same time, attention is to be paid to shifting the stability limits of other phases (e.g. eta phase) to lower temperatures. Furthermore, it is to be endeavored to activate additional hardening mechanisms.
This task is accomplished by a high-temperature nickel-base alloy consisting of (in wt %):
Advantageous further developments of the alloy according to the invention can be inferred from the dependent claims.
The nickel-base alloy according to the invention is intended to be preferably usable for structural parts exposed to structural-part temperatures above 700° C., preferably >900° C., especially >950° C. The objective, namely of shifting the gamma prime phase to higher temperatures, is achieved, wherein simultaneously the stability of other phases may be realized lower than gamma prime and likewise at lower temperatures.
In the following, important cases of application of the alloy are addressed:
The said structural parts are used together and separately in hot and highly stressed atmospheres, wherein continuous structural-part temperatures, sometimes above 900° C., are encountered. Beyond that, oxygen-containing atmospheres are encountered, for example in passenger-car or heavy-truck engines, jet engines or gas turbines.
The alloy according to the invention has a high high-temperature strength and creep strength, wherein simultaneously a high thermal corrosion resistance (e.g. to exhaust gases) is also achieved.
Beyond this, the alloy according to the invention is fatigue-resistant at high temperatures, especially above 900° C.
Possible product forms are:
The following elements may be varied (in wt %) as indicated in the following, for optimization of the desire parameters:
It is of advantage when the sum of Ti+Al (in wt %) is at least 1%. In certain cases of use, it may be expedient when the sum of Ti+Al (in wt %) is at least 1.5%, especially at least 2%.
According to a further idea of the invention, the Ti/Al ratio should be at most 3.5, especially at most 2.0%.
By reduction of the Ti/Al ratio, no or only little eta-phase Ni3Ti is able to form.
The high-temperature nickel-base alloy according to the invention is preferably usable for industrial-scale production (>1 metric ton).
The advantages of the alloy according to the invention will be explained in more detail on the basis of examples:
In Table 1, the prior art (Nicrofer 5120 CoTi—produced on the industrial scale) is compared with an identical reference batch (laboratory) as well as with several alloy compositions according to the invention.
In Table 2, the prior art (Nicrofer 5120 CoTi—produced on the industrial scale) is compared with several batches produced on the industrial scale.
Table 1 (continued)
Respectively 8 kg per heat of starting materials were used (Table 1). After casting, spectral analyses of the samples were performed. The samples were then rolled to a thickness of 6 mm. By further rolling (with intermediate annealing) on a laboratory roll, the samples were rolled to a final thickness of 0.4 mm.
The solution annealing was carried out at 1150° C. for 30 minutes and followed by quenching in water.
A precipitation hardening was carried out at temperatures of 800, 850, 900 or 950° C. for 4/ 8/16 hours followed by quenching in water.
In the process, the variants 250575 to 250577 exhibited a very high hardness level compared with the prior art, as did respectively the variants 250573 and 250574. This means that the hardness-increasing phase (here gamma prime) is still stable.
For industrial-scale applications (Table 2), the material is produced in a medium-frequency induction furnace then cast as a continuous casting in slab form. Then the slabs are remelted in the electroslag remelting furnace to further slabs (or respectively bars). Thereafter the respective slab is hot rolled, for production of strip material in thicknesses of approximately 6 mm. This is followed by a process of cold-rolling of the strip material to a final thickness of approximately 0.4 mm.
In this way a starting material for deep-drawn or stamped products is now obtained. If necessary, a thermal process may still be applied, depending on the product.
For production of structural parts for aeronautics, the following manufacturing process is conceivable:
The product form after the VAR may be a slab or a bar.
The forming may be carried out by rolling or forging.
For production of structural parts for power plants or motor vehicles, the following manufacturing process is also conceivable:
Here also, forming by forging or rolling is conceivable.
In the case of the standard version, it is apparent that, at given temperature and load, the material fails after less than 100 hours.
The other two variants both exhibit endurance times of approximately 400 hours and respectively 550 hours.
Variants 76 and 77 exhibit improved endurance times, which in the operating condition lead to a greater creep resistance and thus to much smaller structural-part deformation.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2017 007 106.3 | Jul 2017 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/DE2018/100663 | 7/24/2018 | WO | 00 |
