Material health monitoring method in a nickel-based superalloy part

Abstract

Method for monitoring the structural health of a nickel-based superalloy part, comprising the steps of: estimating (S101) a local strain distribution ε, temperature T, and strain rate within the part; estimating (S102) a local dislocation density ρ within the part based on the local strain distribution ε, temperature T, and strain rate; and determining (S103) the local presence of a structural anomaly when the local dislocation density ρ is outside a predetermined range of values. Fig. 1.

Description

Title of the invention: Method for monitoring the health of matter in a nickel-based superalloy part. Technical field

[0001] The present exposition relates to a method for monitoring the health of a nickel-based superalloy part, and a method for manufacturing a nickel-based superalloy part. Previous technique

[0002] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies both to new types of aircraft and to those already in service, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0003] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft engines. The Applicant takes into account the factors impacting all phases of design and development in order to obtain less energy-intensive and more environmentally friendly aeronautical components and products, whose integration and use in civil aviation have moderate environmental consequences, with the aim of improving the energy efficiency of aircraft engines.

[0004] Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, in particular through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and, as essential complements to technological progress, aviation biofuels.

[0006] This work notably involves the development of nickel-based superalloys for manufacturing aeronautical parts, in particular parts intended to be used at high temperatures.

[0007] It has been observed that these materials can sometimes exhibit anomalies related to their implementation, which can degrade their performance.

[0008] In particular, these materials are sensitive to the phenomenon of grain bursting, in which abnormally large grains are formed by abnormal growth mechanisms, having for example average equivalent circle diameters of about 60 pm against about 10 pm for grains of so-called normal sizes (Charpagne, M.-A., Franchet, J.-M. and Bozzolo, N. (2018) 'Overgrown grains appearing during sub-solvus heat treatment in a polycrystalline y-y' nickel-based superalloy', Materials & Design, 144, pp. 353-360. doi:10.1016 / j.matdes.2018.02.048).

[0009] This consequently leads to a significant degradation of the mechanical properties of parts comprising these superalloys, particularly their fatigue resistance and yield strength, potentially resulting in reduced performance, for example, a reduction in the yield strength of the parts of up to 15%, or a decrease in the lifespan of the parts, for example, a reduction in fatigue life by a factor of 10 (Flageolet, B., Yousfi, O., Dahan, Y., Villechaise, P. and Cormier, J. (2010). Characterization of Microstructures Containing Abnormal Grain Growth Zones in Alloy 718. In Superalloy 718 and Derivatives (eds EA Ott, JR Groh, A. Banik, I. Dempster, TP Gabb, R. Helmink, X. Liu, A. Mitchell, GP Sjöberg and A. Wusatowska-Sarnek). doi :10.1002 / 9781118495223.ch46). Such a degradation of performance can also lead to the scrapping of parts if such an anomaly is detected during manufacturing or production.

[0010] Such degradation has been observed in particular in forging processes followed by heat treatment. When a material is work-hardened, for example following forging, the grains composing it accumulate dislocations. This accumulation of dislocations is associated with an accumulation of energy stored in the microstructure. Subsequent heat treatment can induce recrystallization: nuclei, taking the form of crystallites, for example, appear at grain boundaries and grow by consuming neighboring work-hardened grains, that is, by consuming the significant stored energy of the work-hardened grains. Under certain heat treatment and work-hardening conditions, very large grains invade the microstructure. This phenomenon, known as "grain bursting," reduces its mechanical properties, thus compromising its performance and durability.

[0011] International patent application WO 2023 / 198995 Al, for example, proposes specific temperature conditions applied to the processing tools and the part intended to be processed. However, this solution implies an additional constraint that could complicate the manufacturing of the part.

[0012] European patent EP2510131 B1 proposes, for example, to maintain the level of deformation within the part beyond a critical value. However, although this generally implies a reduction in the number of burst grains, these may persist in certain manufacturing ranges, particularly under certain temperature or deformation rate conditions. Furthermore, it has been shown that temperature (R. Watson, M. Preuss, J. Quinta Da Fonseca, T. Witulski, G. Terlinde, The Effect of Strain and Temperature Profiles on Static Recrystallization during Solution Heat Treatment After Hot Deformation of Alloy 718, in: 8th Int. Symp. Superalloy 718 Deriv., TMS, 2014: pp. 873-884), strain rate (C. Aoki, T. Ueno, T. Ohno, K. Oikawa, Influence of hot-working conditions on grain growth of superalloy 718, J. Mater. Process. Technol. 267 (2019) 26-33), and heating rate during subsequent heat treatment (IMD Parr, TJ Jackson, MC Hardy, DJ Child, C. Argyrakis, K. Severs, V. Saraf, JMStumpf, Inhomogeneous Grain Coarsening Behavior In Supersolvus Heat Treated Nickel-Based Superalloy RrlOOO, in: Superalloys 2016, n.d.) influence the presence of burst grains.

[0013] The work of Charpagne (2016) shows a critical window of Geometrically Necessary Dislocations (GNDs) leading to grain bursting during subsequent heat treatment. These GNDs are deduced from intergranular misorientations measured by electron backscatter diffraction (EBSD). This purely experimental work requires destructive characterization of the material. It does not allow for predicting in advance whether a range presents a risk of grain bursting, nor does it provide information on its location. No numerical study has been carried out to date; this is the object of the present invention.

[0014] A need therefore exists for a material health monitoring method for a part made of a nickel-based superalloy, at least partially free from the aforementioned drawbacks. Description of the invention

[0015] To this end, the invention is the result of technological research aimed at significantly improving aircraft performance and, in this sense, contributes to reducing the environmental impact of aircraft.

[0016] During the forging process, the hot-forged part interacts significantly with the tooling and the environment. Heat exchange, combined with the friction produced between the forged part and the tooling used, leads to variations in temperature T, strain rate e, and strain velocity è between each point of the part. These differences result in different microstructure evolutions within the forged part. Certain forging conditions can cause large grain anomalies associated with the grain bursting phenomenon in certain areas of forged parts.

[0017] The invention relates to a method for monitoring the health of the structure of a part made of nickel-based superalloy, comprising the steps of: estimation of a local distribution of strain e, temperature T and strain rate £ within the part; estimation of a local dislocation density p within the part based on the local strain distribution e, temperature T and strain rate ε; and determination of the local presence of structural anomaly when the local dislocation density p is outside a range of predetermined values.

[0018] The term “mechanical part” means any part designed to perform a specific function, for example in the field of rail, maritime, automotive or air transport.

[0019] Such a structural health monitoring process makes it possible to effectively identify a risk of structural anomaly of a part, and in particular to identify and prevent this risk upstream of the manufacture of the part.

[0020] The term "material health monitoring" of a part's structure refers to the assessment of the presence of a structural anomaly in said part, for example, the qualitative and / or quantitative assessment of the past, present, and / or future presence of anomalies in said structure. Anomalies include, for example, structures that lead to a degradation of the part's performance and / or durability. For example, the anomaly could be the presence of "burst grains."

[0021] A structural anomaly is defined as any unwanted inhomogeneity (heterogeneity) in a material, which typically leads to structural weakness and / or degradation of mechanical or thermomechanical properties. Typically, a structural anomaly includes the presence of splintered grains.

[0022] Such a process is particularly effective for identifying the material health condition of the structure of a forged part.

[0023] Such a process has the advantage of better taking into account all the parameters of the part forming process as well as the metallurgical state of the part.

[0024] A complete forging process, for example of nickel-based alloys, may consist of several forging operations. It is generally followed by heat treatment. A complete forging operation includes, for example, a step of heating a billet in a furnace to a forging temperature, its transfer to forging presses, a waiting period before forging, the forging itself, another waiting period after forging, the transfer of the forged part to a cooling environment, until its final cooling.

[0025] In addition, such a method is compatible with numerical simulation methods, allowing non-destructive testing of a manufacturing process.

[0026] Such a method makes it possible to increase and optimize manufacturing capacity, production and, consequently, to significantly reduce associated greenhouse gas emissions and raw material consumption.

[0027] By determining the local presence of a structural anomaly, the process makes it possible to determine manufacturing conditions for parts with a reduced number of structural anomalies, thus extending the life of the components and, consequently, reducing the number of replacements with new parts; and significantly decreasing the number of parts scrapped during manufacturing.

[0028] Typically, the method includes defining a finite element mesh. The local strain distribution e, temperature T and strain rate É is estimated for the finite elements of the finite element mesh, for example in a macroscopic forging simulation; and the local dislocation density p within the part is estimated for the finite elements of the finite element mesh, for example in a microstructure simulation at the microscopic scale.

[0029] The term "macroscopic scale" is understood to be in comparison to a smaller "microscopic scale." For example, the macroscopic scale is the scale of the part and / or the microscopic scale is the scale of a grain.

[0030] Typically, the method includes determining the local presence of a structural anomaly when the local dislocation density p satisfies 1014 m 2 < p < 4.1014 m 2.

[0031] Typically, the structural anomaly includes the presence of burst grains.

[0032] Typically, the nickel-based superalloy comprises: 50% to 55% nickel by mass, 17% to 21% chromium by mass, 15% to 21% iron by mass, 4.75% to 5.5% niobium by mass, 2.8% to 3.3% by mass of molybdenum, 0.65% to 1.15% by mass of titanium, and 0.2% to 0.8% by mass of aluminum, the rest being unavoidable impurities.

[0033] Such an alloy is for example known under the trade name Inconel® 718.

[0034] Typically, the nickel-based superalloy comprises: 0.03% by mass of carbon, 16.0% chromium by mass, 13.0% cobalt by mass, 1.0% by mass of iron, 3.7% by mass of titanium, 2.1% by mass of aluminum, 0.7% by mass of niobium, 4.0% by mass of molybdenum, 4.0% by mass of tungsten, the remainder being nickel and unavoidable impurities.

[0035] Such an alloy is for example known under the trade name René 65 (Heaney, JA, Lasonde, ML, Powell, AM, Bond, BJ and O'Brien, CM (2014). Development of a New Cast and Wrought Alloy (René 65) for High Temperature Disk Applications. In 8th International Symposium on Superalloy 718 and Dérivatives (eds E. Ott, A. Banik, J. Andersson, I. Dempster, T. Gabb, J. Groh, K. Heck, R. Helmink, X. Liu and A. Wusatowska-Samek). doi: 10.1002 / 9781119016854.ch6).

[0036] Other alloys can be considered, for example the Nickel-based superalloys AD730™ or Udimet™ 720 (PER72®), or the austenitic iron-based alloy Incoloy® A-286.

[0037] The invention also relates to a method for manufacturing a part made of nickel-based superalloy, comprising a structural health monitoring step for the material of a nickel-based superalloy according to the invention, the method comprising: determining at least one manufacturing parameter of at least one manufacturing step of the part, simulating the manufacturing of the part according to at least one parameter of at least one manufacturing step of the part, determining the local presence of structural anomalies, and if the determination of the local presence of structural anomaly has determined that no structural anomaly is present in the part during at least one manufacturing step of the part, the manufacturing of the part according to at least one manufacturing parameter determined.

[0038] Such a manufacturing process makes it possible in particular to ensure the validation of manufacturing parameters of the part, and thus ensure the manufacture of conforming parts and presenting the aforementioned advantages.

[0039] Typically, the manufacturing step of the part includes a forging step prior to a heat treatment step.

[0040] The invention also relates to a nickel-based superalloy part directly obtained by the process according to the present invention.

[0041] The present invention further relates to a computer program comprising instructions executable by a processor, which, when executed by the processor, implement the method of monitoring the health of the structure of a part made of nickel-based superalloy according to the present invention or the method of manufacturing a part made of superalloy according to the present invention.

[0042] The computer program can be coded in any programming language and take the form of source code, object code, or an intermediate form between source code and object code, such as a partially compiled form or any other desired form.

[0043] The present invention also relates to a computer-readable data carrier on which the computer program as defined above is recorded.

[0044] Such a data carrier may be an internal or external hard drive, a USB flash drive, a CD-ROM, a memory card, or a cloud. Of course, this list is not exhaustive and may include any other data carrier known to a person skilled in the art and not mentioned in this patent application. Brief description of the drawings

[0045] [Fig-1] Fig. 1 is a flowchart of a method for estimating an anomaly of the structure of a part made of nickel-based superalloy according to an embodiment of the invention.

[0046] [Fig.2] The [Fig.2] is a flowchart of a manufacturing process for such a part according to an embodiment of the invention. Description of the implementation methods

[0047] The present invention will be described with reference to specific embodiments, and it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawing should be considered in an illustrative rather than restrictive sense.

[0048] The present invention relates to a method for monitoring the health of the structure of a part made of nickel-based superalloy, and will be described with respect to [Fig.1].

[0049] The material health monitoring process may, for example, involve the estimation of anomalies in an aeronautical part.

[0050] Material health monitoring can be carried out prior to the manufacture of the part, in order to determine the risk of anomaly occurring for certain manufacturing parameters, or to determine manufacturing parameters that reduce the risk of anomalies occurring.

[0051] Material health monitoring can be carried out before and after the manufacture of a part, in order to help validate a manufactured part without involving any destructive testing method for the part.

[0052] S101: The process includes a step of estimating a local distribution of strain e, temperature T and strain rate £ within the part, the strain rate £ being the first derivative with respect to time of the strain e.

[0053] The local strain distribution e, temperature T, and strain rate ε can be obtained from a finite element calculation method, comprising a finite element mesh of the part, the thermomechanical properties of the material, and a model including the thermomechanical properties of the nickel-based superalloy considered. The model may also include heat exchange between the part, the tooling, and / or the environment. The model may also include friction between the forged part and the tooling.

[0054] For example, the estimation of the local strain distribution e, temperature T, and strain rate ε within the part can be performed using a finite element method. Such a simulation method can, for example, be implemented using FORGE® or DEFORM® software. For example, the estimation of the local strain distribution e, temperature T, and strain rate ε within the part can be performed at the macroscopic scale.

[0055] The local calculation of T, e, and e during a forging step can be validated by a correct prediction of the forged geometry, the evolution of the press force during forging, and the temperature of the forged parts before, during, and after forging. These validations are based, for example, on correct identifications of the heat transfer coefficients between the hot billet, the environment, and the dies, the friction coefficients between the billet and the dies, and / or the mechanical properties of the forged material.

[0056] S102: The method further includes estimating a local dislocation density p within the part based on the local strain distribution e, temperature T and strain rate Σ.

[0057] The estimation of the local density of dislocations p within the part can for example be carried out at the microscopic scale.

[0058] The local dislocation density p can notably be established from a predetermined recrystallization model taking as input the local strain distribution e, temperature T and strain rate ε. In addition or Alternatively, the recrystallization model can also take the initial metallurgical state of the part as input.

[0059] The recrystallization model may, for example, include a hardening model allowing estimation of the local density of p dislocations.

[0060] In addition or as a replacement, the recrystallization model may for example include a model of grain germination and growth during recrystallization.

[0061] In addition or as a replacement, the recrystallization model may, for example, include a static restoration model of the nickel-based superalloy considered.

[0062] The work hardening model makes it possible, in particular, to describe the increase in dislocation density of the material undergoing external hot deformation. When the density of these dislocations becomes significant, it can lead to the nucleation of new grains lacking dislocations, characterizing the phenomenon of recrystallization. These newly recrystallized grains can then grow, resulting in an increase in grain size and, simultaneously, a decrease in the interfacial energy between them. When the external deformation ceases, the dislocation density in the material continues to decrease through a rearrangement of dislocations via a static restoration phenomenon.

[0063] The inhomogeneity of the local distribution of strain e, temperature T and strain rate £ within the part can generate an inhomogeneous evolution of dislocation density and associated microstructure within the part.

[0064] The recrystallization model can, for example, be implemented with a full-field approach, where the microstructure is explicitly defined in a finite element mesh, making it possible in particular to consider the interactions between grains of the y phase and particles of secondary phases

[0065] A recrystallization model is integrated into a computational code with a full-field approach in which the microstructure, or the interaction between grains, is explicitly described. For example, the level-set method, integrated into the DIGIMU® software, could be used. Alternatively, a mean-field approach could be considered, in which the interaction between grains is homogenized within a homogeneous equivalent medium. The local dislocation density p can thus be estimated and its monitoring carried out by such a recrystallization model.

[0066] Typically the S102 step of estimating a local density of dislocations p within the part can be carried out using the DIGIMU® software.

[0067] S103: When the local dislocation density p takes a value in one or more predetermined ranges of values, it is determined that a structural anomaly is locally present.

[0068] The local density of dislocations allows us to group together the influence of temperature, level of deformation, rate of deformation, time of holding at temperature, heating and cooling rates of the forging stage as well as the initial microstructures.

[0069] This implies a simplified criterion allowing reliably and sensitively taking into account the influence of the different manufacturing parameters.

[0070] For example, it is determined that a structural anomaly is present when the local dislocation density p satisfies 10 m < p < 4.10 m.

[0071] The criterion 1014 m2< p < 4.1014 m 2 is particularly suitable for determining the presence of grain bursting.

[0072] In particular, this criterion was tested and was verified for two nickel-based superalloys under the following conditions.

[0073] On the one hand, Inconel® 718, comprising: 50% to 55% nickel by mass, 17% to 21% chromium by mass, 15% to 21% iron by mass, 4.75% to 5.5% niobium by mass, 2.8% to 3.3% by mass of molybdenum, 0.65% to 1.15% by mass of titanium, and 0.2% to 0.8% by mass of aluminum, the rest being unavoidable impurities.

[0074] This criterion has notably been verified for compression and torsion tests on Inconel® 718 samples under temperature conditions T ranging from 900°C to 990°C and for strain rates É ranging from 0.01 s 1 to 0.2 s '.

[0075] This criterion was also verified for industrial parts forged from Inconel® 718, after sub-solvus forging at a nominal temperature of 985°C followed by heating at 985°C for 2 hours.

[0076] On the other hand, this criterion was verified for compression tests on samples in René® 65 under compression conditions of 1000°C to 1070°C for a strain rate Σ = 0.01 s'1, after heat treatment at 1065°C for 1h.

[0077] Health monitoring of the structure of a nickel-based superalloy can be integrated into a manufacturing process for a part made of a nickel-based superalloy, which will be described with respect to [Fig.2].

[0078] S201: The manufacturing process includes a step of determining at least a manufacturing parameter of at least one manufacturing step of the part.

[0079] Typically, the nickel-based superalloy is a y / y' superalloy or a y / y' superalloy”.

[0080] The manufacturing step may include a forging step, for example at a temperature below the solvus (“sub-solvus”) of phase y' for a superalloy y / y', or at a temperature below the solvus of phase ô for a superalloy y / y”.

[0081] S202: The manufacturing process includes a manufacturing simulation step of the part according to the parameter(s) of at least one manufacturing step of the part.

[0082] This simulation step makes it possible in particular to obtain a local distribution of strain e, temperature T and strain rate É within the part, as well as its evolution during the manufacturing step of the part, in accordance with step S101 above.

[0083] The local density of dislocations p within the part can then be estimated, in accordance with step S102 above, and the presence of a structural anomaly determined in accordance with step S103 above.

[0084] S203: If it is determined that a structural anomaly is present, the process The manufacturing process can restart at step S201, taking into account new manufacturing parameters. If it is determined that no structural anomalies are present, the manufacturing process can proceed to step S204, manufacturing the part according to the part's manufacturing parameter(s).

[0085] It is evident that all the characteristics described with reference to the process are transferable, alone or in combination, to a device and vice versa. For example, this process can be carried out by a device or a plurality of devices combined with each other and / or connected to a computer. A person skilled in the art is able to decide on the material means to be used to enable the implementation of the various steps of the process.

Claims

Demands

1. A method for monitoring the structural health of a nickel-based superalloy part, comprising the steps of: estimating (S 101) a local strain distribution e, temperature T and strain rate ε within the part; estimating (S 102) a local dislocation density p within the part based on the local strain distribution e, temperature T and strain rate ε; and determining (S 103) the local presence of a structural anomaly when the local dislocation density p is outside a predetermined range of values; the method comprising defining a finite element mesh, estimating the local strain distribution e, temperature T and strain rate ε for the finite elements of the finite element mesh; and estimating the local dislocation density p within the part for the finite elements of the finite element mesh.

2. Method according to claim 1, comprising the determination (S 103) of the local presence of a structural anomaly when the local dislocation density p satisfies 1014 m 2 < p < 4.1014 m 2.

3. A method according to claim 1 or 2, wherein the structural anomaly includes the presence of burst grains.

4. A process according to any one of claims 1 to 3, wherein the nickel-based superalloy comprises 50% to 55% by mass of nickel, 17% to 21% by mass of chromium, 15% to 21% by mass of iron, 4.75% to 5.5% by mass of niobium, 2.8% to 3.3% by mass of molybdenum, 0.65% to 1.15% by mass of titanium, and 0.2% to 0.8% by mass of aluminum, the remainder being unavoidable impurities.

5. A process according to any one of claims 1 to 3, wherein the nickel-based superalloy comprises: 0.03% by mass of carbon, 16.0% by mass of chromium, 13.0% by mass of cobalt, 1.0% by mass of iron, 3.7% by mass of titanium, 2.1% by mass of aluminum, 0.7% by mass of niobium, 4.0% by mass of molybdenum, 4.0% by mass of tungsten, the remainder being nickel and unavoidable impurities.

6. A method for manufacturing a part from a nickel-based superalloy comprising a material health monitoring step of a nickel-based superalloy according to any one of claims 1 to 5, the method comprising: the determination (S201) of at least one manufacturing parameter of at least one manufacturing step of the part, the simulation (S202) of the manufacturing of the part according to at least one parameter of at least one manufacturing step of the part, the determination (S203) of the local presence of structural anomalies, and if the determination of the local presence of structural anomalies has determined that no structural anomalies are present in the part during at least one manufacturing step of the part, the manufacturing (S204) of the part according to the determined at least one manufacturing parameter.

7. A method according to claim 6, wherein the part manufacturing step includes a forging step prior to a heat treatment step.

8. Nickel-based superalloy part directly obtained by the process according to claim 6 or 7.

9. A computer program comprising instructions executable by a processor, which, when executed by the processor, implement the method for monitoring the material health structure of a nickel-based superalloy part according to claims 1 to 5 or the method for manufacturing a superalloy part according to claim 6 or 7.

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