Patent Application
20240269743
The present disclosure relates to the technical field of turbomachine disks. The present disclosure relates more specifically to the field of methods for producing turbomachine disks.
Turbomachine disks are axially symmetric circular parts. These disks are subject to very high rotational speeds and large centrifugal forces. For performance reasons, the most stressed disks of the turboreactors subject to the highest temperatures are made of a nickel alloy. These alloys were first used in the manufacturing of military engines, and then also of latest generation civil engines, in particular high-power engines.
Today, the production method for this type of turbomachine disk is as follows:
As described in CN 102,615,284, it is possible to produce this type of turbomachine disk from a powder obtained by plasma atomization.
VIGA is shown by
The disks resulting from this method have ceramic inclusions. These ceramic inclusions are rupture-initiating sites in the material. The proportion of ceramic inclusions in the final disk is relatively low and for most mechanical properties, the presence of a ceramic inclusion, in particular of less than 53 μm within a very strong homogeneous metal structure, has no substantial impact. This is for example the case for the mechanical properties in traction, creep and for crack propagation.
In contrast, the presence of these ceramic inclusions, even when very rare, has a large impact on the properties in fatigue and in particular Low Cycle Fatigue (LCF).
It was observed that the minimum, dotted curve corresponds to the presence of ceramic inclusions at the surface of the disks S and that the average, solid curve corresponds to the presence of ceramic inclusions at the subsurface SS. Finally, it was also observed that the presence of ceramic inclusions in the core of the material of the disk C corresponds to an LCF curve close to the average curve.
The ceramic inclusions come from the step of manufacturing the raw powder and in particular from VIGA. In fact, in VIGA, the crucible Cr, the tundish T and the nozzle N are made of ceramic. The molten alloy MA is in more or less extended contact with the material of the crucible Cr, the tundish T and the nozzle N, interacts with them, and pulls loose ceramic particles therefrom by erosion. These ceramic particles are found in the raw powder. The composition of ceramic particles comprises for example mostly aluminium, magnesium, calcium, phosphorus, silicon and oxygen, in particular in the form of Al2O3—CaO or Al2O3—MgO ceramics.
Depending on their size and shape, the ceramic particles may pass through the sieve and be found in the final part. When these ceramic particles are found in the shaped, final powder, since they are refractory material, they are unimpacted by the hot operations of compacting, extruding, forging and heat treating during the manufacturing of disks. They are therefore found in the finished part and impact the mechanical properties thereof. Thus, it is important to be sure that there are no such particles in the disks put into operation.
Ultrasonic inspection makes it possible to identify the largest inclusions in the billets, and in particular the inclusions for which the largest dimension exceeds 200 μm and for which the length/width ratio is large, of about 4 to 5, which allows them to pass through the sieve used. If such a particle is identified, the affected section of the billet is eliminated.
An ultrasonic inspection is also preformed on the part after forging and heat treating in order to detect the presence of inclusions which led to initiation of clinks (thus cracks) during forging. The presence of these inclusions leads to discarding the part.
Further, for this type of material with ceramic inclusions, the minimum sizing curves used for sizing the parts must consider this point.
Additionally, the presence of a few but randomly distributed ceramic inclusions in the finished part requires a different sizing approach from the approach used for a conventional metal part, i.e. with a homogeneous structure: a probabilistic approach has to be used.
Indeed, for a conventional metal material, sizing is done by using sizing curves established from trials on test specimens sampled on the finished parts. The microstructure, which is homogeneous, is globally equivalent from one test specimen to another. Thus, the sampled test specimen is representative of the structure of the whole part.
For alloys obtained by VIGA, the results on test specimens (therefore the sizing curves) are only representative of areas of the part having a test volume equivalent to that of the test specimens due to the presence of ceramic inclusions randomly distributed in the finished part. This is the reason, for these alloys, why the fatigue tests are done on larger size test specimens, for example test specimens having a useful volume of about 5 to 10 times greater than that of the fatigue test specimens used.
However, in real parts, some areas are relatively massive and therefore involve significantly larger volumes than that of the test specimens, even the largest used. These part areas are therefore not covered by this sizing network on large test specimens; it is necessary to use a complex probabilistic sizing technique.
This technique takes into account the massiveness of the considered zone, the cleanliness curve of the alloy (meaning, in the case of alloys prepared by VIGA, the number of ceramic particles per kilogram), the size of the critical defect represented by a ceramic inclusion, the probability of the presence of the critical defect. More concretely, the size of the critical defect is determined for each characteristic area of the disk based on the desired lifetime, information about the presence of cracks in the finished parts and measurements done on fatigue test specimens. With the size of the critical defect and the cleanliness curve, the probability of the presence of the critical defect can be calculated for finally determining the minimum dimensions of the part.
According to this manufacturing method, the only parameter which the manufacturer can work with for optimizing the lifetime under fatigue of such alloys is the size of the ceramic inclusions. Thus, in the 2000s, sifting with a <53 μm granulometric cut-off replaced the conventional sifting of the time which used a <75 μm granulometric cut-off. The lifetime of the parts was extended with an improvement of a factor of 3 as shown in
Thus, in the method currently used for manufacturing disks, the step of sifting is important because it makes it possible to reduce the quantity and size of ceramic particles in the powder which will be shaped and in the end, it makes it possible to increase the lifetime.
Further, a <53 μm granulometric cut-off leads to a ceramic particle frequency of between 5 and 40 particles per kilogram of powder.
However, the use of a granulometric cut-off that low also leads to discarding a substantial quantity of powder produced by VIGA (between 30 and 50% by weight).
An objective of the present disclosure is to remedy at least one drawback of the prior art described above. In particular, an objective of the present disclosure is to improve the lifetime of turbomachine disks exposed to the highest temperatures.
To this aim, the present disclosure provides a method for manufacturing turbomachine disks. The method comprises:
CN 110,586,948 and US 2020/131604 describe a method for manufacturing a turbomachine disk from a powder obtained by EIGA.
The inventors, however, observed that obtaining the nickel alloy powder by EIGA was not sufficient for eliminating the presence of ceramic inclusions in this powder. Indeed, as taught in “Innovative technology for powder metallurgy-based disk superalloys: Progress and proposal” Chin. Phys. B, vol. 25, No. 2 (2016), EIGA may prevent, but not eliminate, the presence of ceramic inclusions in this powder.
Now, as indicated above, the presence of these ceramic inclusions, even when very rare, has a large impact on the fatigue properties.
Advantageously, the combination of the manufacturing the nickel alloy electrode by PAM-CHR and atomizing the nickel alloy by EIGA makes it possible to eliminate the presence of the ceramic inclusions in the resulting nickel alloy powder.
Further optional and nonlimiting features are as follows.
During PAM-CHR refining, the nickel alloy may be melted in a water-cooled copper crucible before being melted in a copper molder ring crucible.
EIGA may comprise:
The inert gas may be argon.
Sifting may be carried out with a granulometric cut-off of between 140 μm and 60 μm or between 130 μm and 70 μm.
Shaping may comprise:
Densifying may comprise:
The foregoing aspects and many of the attendant advantages of the claimed subject matter will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
The detailed description set forth above in connection with the appended drawings, where like numerals reference like elements, are intended as a description of various embodiments of the present disclosure and are not intended to represent the only embodiments. Each embodiment described in this disclosure is provided merely as an example or illustration and should not be construed as preferred or advantageous over other embodiments. The illustrative examples provided herein are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed.
A method for manufacturing turbomachine disks according to the present disclosure is described below with reference to
Such a method comprises providing S100 a powder of nickel alloy and shaping S200 the powder into a disk (
Obtaining S100 the powder comprises atomizing S120 a nickel alloy through Electrode Induction-Melting Gas Atomization (also called EIGA) and sifting S130 the raw powder under vacuum or under neutral atmosphere with a granulometric cut-off of between 150 μm and 50 μm (
EIGA (
Contactlessly heating S122 may be carried out through induction. Heating S122 is performed until the electrode material melts and a thin stream of molten alloy flows from the lower end of the electrode.
Injecting S123 the inert gas towards the thin stream of molten alloy cuts the thin stream of molten alloy into molten alloy particles Pm. The injected inert gas may be argon.
Atomizing S120 may comprise cooling S124 the molten alloy particles Pm to obtain solid particles Ps. Cooling S124 may be performed passively, meaning by contacting the molten alloy particles Pm with the surrounding atmosphere, the molten alloy particles Pm exchanging heat with this atmosphere. Cooling S124 may also be active, for example by injecting an inert gas with a temperature lower than the melting temperature of the alloy. Active cooling S124 may also be performed by cooling the atomization tower in which particles are produced, for example using a cooling circuit surrounding the atomization tower.
EIGA requires an electrode 2 of the desired nickel alloy, a contactless heater, for example an induction heater 3, and an inert gas injector 4. The contactless heater comprises a space for receiving the lower end of the electrode 2. In the case of an induction heater 3, this latter comprises coils around a receiving space. The injector 4 comprises a central orifice 41 serving as a nozzle with an inlet at its upper part and an outlet at its lower part. The injector 4 also comprises an injection crown 42 and a convergence crown 43 for bringing the gas towards the outlet of the injector 4. Further, the injector 4 may be conFIGUREd to generate a swirling flow of the inert gas. During contactless heating, the lower end of the electrode 2 is induction heated by the coils of the induction heater 3 until the electrode material melts. From this moment (see
Replacement of VIGA by EIGA is not an obvious choice. In fact, VIGA allows a very precise control of the temperature to which the alloy is heated and in particular allows overheating this alloy because this latter is contained in a crucible during heating. The overheating of the alloy has the advantage of allowing production of powders that are very fine compared to a heating temperature equal to the melting temperature. This overheating is not as easily controllable with EIGA because the alloy flows in the form of a thin stream as soon as it reaches its melting temperature. Further, VIGA makes it possible to control the thickness of the stream flowing from the crucible by controlling the opening of the crucible nozzle. This control is not possible with EIGA.
Also, EIGA uses an electrode which must be fabricated. This then adds an additional step in the manufacturing process of the powder, whereas VIGA simply makes it possible to gather the ingredients in the crucible before heating.
The electrode used in EIGA is made by plasma arc melting with cold hearth refining(also known under the acronym PAM-CHR).
PAM-CHR may be carried out in a cold-crucible refining furnace. In that kind of furnace, the metal is first melted in a water-cooled copper crucible before flowing into a copper molder ring. Copper is not reactive with nickel alloys; this eliminates any contamination of the electrode by ceramic inclusions.
Thus, providing S100 the powder comprises manufacturing S110 an electrode 2 such as described above (
The granulometric cut-off may be comprised between 140 μm and 60 μm or even between 130 μm 70 μm, for example 125 μm, 75 μm or 53 μm. Sifting S130 results in a nickel alloy powder which will be used for shaping S200.
The use of a <53 μm granulometric cut-off in VIGA was due to the intent to improve the mechanical properties of the manufactured parts which were reduced by the presence of ceramic inclusions in the material. The present authors, when looking for a solution for even further improving the mechanical properties, identified the combination of PAM-CHR and EIGA as a solution for manufacturing the nickel alloy powder with a greatly reduced or even nonexistent ceramic inclusion contamination level compared to VIGA. They next had the idea of raising the granulometric cut-off up to 75 μm, even 125 μm or even 150 μm. The use of a higher granulometric cut-off leads to an improvement in the atomization yield; indeed, less raw powder needs to be discarded, or otherwise expressed, a larger portion of raw powder may be used for manufacturing the disks.
Another indirect advantage relates to the grain size of the finished parts. Now, it is well known that the creep properties increase with the grain size. During the manufacturing of the disks, the nickel alloy is treated at temperatures over γ′ solvus. At these temperatures, the primary γ′ grains, the role of which is to block the grain joints, are dissolved and the grains grow. However, in the case of powders, the growth of the grain remains limited to the size of the particles of the initial powder. In fact, the growth of the grains is blocked by the prior particle boundaries of the particles (also known as PPB) which are thin oxide layers at the surface of the powder particles and which limit the grain size to the initial size of the powder particles.
By increasing the granulometric cut-off, the powder particle size is increased which makes it possible to increase the grain size in the finished part thereby improving the creep properties thereof.
The absence of ceramic inclusions makes it possible to dispense with the probabilistic approach to the sizing of the parts and return to a conventional approach in which the sampled test specimen is representative of the material of the entire part.
Shaping S200 may comprise hot densifying S210 the sifted powder into a forging blank and manufacturing S220 the disk (
Densifying S210 may comprise placing S211 the sifted powder under vacuum in a hermetically sealed container, hot compacting S212 the container, extruding S213 the compacted container resulting in a cylindrical bar having an outer layer made of the material of the container and a cylindrical core made of nickel alloy, and eliminating S214 the outer layer, for example by machining, and cutting S215 the cylindrical core into forging blanks (
Manufacturing S220 the disk may comprise isothermally forging S221 the blank, heat treating S222 and machining S223 the disk (
Heat treating may comprise solution annealing at high temperature followed by controlled cooling and a tempering treatment at a lower temperature for a longer time. With a combination of temperature, time and cooling speeds, these treatments make it possible to guide the microstructure in terms of grain size and size distribution of the hardening γ′ phase to obtain the required mechanical properties.
Machining provides the part with its final geometry according to the plan.
In the foregoing description, specific details are set forth to provide a thorough understanding of exemplary embodiments of the present disclosure. It will be apparent to one skilled in the art, however, that the embodiments disclosed herein may be practiced without embodying all of the specific details. In some instances, well-known process steps have not been described in detail in order not to unnecessarily obscure various aspects of the present disclosure. Further, it will be appreciated that embodiments of the present disclosure may employ any combination of features described herein.
The present application may reference quantities and numbers. Unless specifically stated, such quantities and numbers are not to be considered restrictive, but exemplary of the possible quantities or numbers associated with the present application. Also in this regard, the present application may use the term “plurality” to reference a quantity or number. In this regard, the term “plurality” is meant to be any number that is more than one, for example, two, three, four, five, etc. The terms “about,” “approximately,” “near,” etc., mean plus or minus 10% of the stated value. For the purposes of the present disclosure, the phrase “at least one of A and B” is equivalent to “A and/or B” or vice versa, namely “A” alone, “B” alone or “A and B.”. Similarly, the phrase “at least one of A, B, and C,” for example, means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C), including all further possible permutations when greater than three elements are listed.
It should be noted that for purposes of this disclosure, terminology such as “upper,” “lower,” “vertical,” “horizontal,” “fore,” “aft,” “inner,” “outer,” “front,” “rear,” etc., should be construed as descriptive and not limiting the scope of the claimed subject matter. Further, the use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings.
Throughout this specification, terms of art may be used. These terms are to take on their ordinary meaning in the art from which they come, unless specifically defined herein or the context of their use would clearly suggest otherwise.
The principles, representative embodiments, and modes of operation of the present disclosure have been described in the foregoing description. However, aspects of the present disclosure, which are intended to be protected, are not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. It will be appreciated that variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present disclosure. Accordingly, it is expressly intended that all such variations, changes, and equivalents fall within the spirit and scope of the present disclosure as claimed.
| Number | Date | Country | Kind |
|---|---|---|---|
| FR2106100 | Jun 2021 | FR | national |
This application is a National Stage of International Application No. PCT/FR2022/051104, filed Jun. 9, 2022, which claims priority to French Patent Application No. 2106100, filed Jun. 9, 2021, the entire disclosures of which are hereby incorporated by reference in their entirety for all purposes.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2022/051104 | 6/9/2022 | WO |
