CHARACTERIZATION TEST DEVICE, CHARACTERIZATION TEST INSTALLATION, METHOD FOR MANUFACTURING SUCH A CHARACTERIZATION TEST DEVICE, AND METHOD FOR CHARACTERIZATION TEST USING SUCH A DEVICE

Abstract

The invention relates to a characterization test device (1) for a lost-wax casting manufacturing process for a turbomachine part (30). The test device (1) comprises: - a shell mold specimen (2) made of refractory material extending along a principal axis (A) and having an internal cavity (8) extending along the principal axis (A), and - a test core (3), representative of a foundry core, installed in the internal cavity (11) and fixed to the shell mold specimen (2) by means of anchoring means (12). The shell mold specimen (2) comprises at least one observation window (11) formed in a wall of the shell mold specimen (2) and opening into the internal cavity. Figure for the abstract: Fig. 10

Description

Title of the invention: CHARACTERIZATION TEST DEVICE, CHARACTERIZATION TEST FACILITY, METHOD FOR MANUFACTURING SUCH A CHARACTERIZATION TEST DEVICE AND METHOD FOR CHARACTERIZATION TEST FROM SUCH A CHARACTERIZATION TEST DEVICE Technical field of the invention

[0001] The present invention relates to the field of lost wax casting, in particular for producing turbomachine parts. More specifically, it relates to a characterization test device with a test core for testing the behavior of a foundry core during at least one of the stages of manufacturing the parts with the lost wax technique in which a temperature variation occurs. It also relates to the characterization test installation, the method for manufacturing the device and the method for characterization testing using such a device. Technological background

[0002] The lost wax casting technique or lost model casting technique is particularly known for the manufacture of parts with complex shapes such as metal parts for turbomachines. The technique consists of producing at least one wax model of the metal part to be manufactured and a mold called a shell mold which is formed around the wax model. The shell mold is obtained by successive deposits of several layers of slip of a refractory material which may have different compositions at each layer deposition operation. Each deposit of a slip layer is followed, for example, by draining, sandblasting, and drying. The wax model is then removed during an operation called dewaxing and carried out in an autoclave, thus leaving space inside the shell mold for an internal cavity of corresponding shape. The internal cavity obtained allows the conveyance and filling of the latter with a molten metallic material.Prior to casting the molten metal material, the shell mold undergoes a heat treatment known as sintering to consolidate the ceramic that makes up the shell mold. After filling the mold with the molten metal material, then cooling and solidifying the metal material, the shell mold is generally destroyed to reveal the metal part in the shape of the wax model.

[0003] When the metal part is a hollow part as is the case with a blade of turbomachine and in particular a high-pressure blade equipped with an internal cooling circuit, one or more casting cores is / are used to define the internal cooling circuit. The casting core(s) are made of a refractory material. The wax model is injected around the casting core(s). After removal of the wax model, the shell mold comprises the internal cavity intended to receive the molten metallic material and the casting core(s) arranged inside the internal cavity intended to subsequently form the internal cooling circuit after removal of the casting core(s).

[0004] The positioning of the core in the internal cavity of the shell mold is ensured by two connections, a fitting connection at one end and a sliding connection at the other end. For example, the fitting can be achieved by a connecting element such as a holding rod or pin at an anchoring point of the foundry core previously placed during the manufacture of the model. A clearance is provided between the different connections of the foundry core and the shell mold at the sliding connection. This clearance must be large enough to ensure the sliding of the foundry core in the sliding plane and small enough to contain out-of-plane displacements. This method makes it possible to make the anchoring isostatic, limiting the risk of deformation, or excessive stresses up to the breakage of the core, during thermal expansion of the core.This clearance is determined with extreme precision (to the nearest hundredth of a millimeter) because the shell mold and the foundry core undergo numerous temperature variations (sintering of the shell mold, preheating of the shell and the core, pouring of the molten metallic material, solidification of the metallic material, cooling of the part, etc.).

[0005] Each foundry core must be able to slide during the pouring of the molten metallic material because a differential expansion between the foundry core and the shell mold occurs during the sintering of the shell mold and during the melting process. If the embedding or anchoring is poorly designed, these temperature variations can cause damage to the shell mold during the manufacture of the metal part and lead to deformation and / or displacement of the foundry core causing dimensional non-conformity of the part (as-cast). In the worst case, the displacement of the foundry core can lead to piercing of the wall of the metal part.

[0006] One of the major difficulties is to ensure the positioning of the casting core in the internal cavity throughout the manufacturing process and in particular during the various temperature variations. However, there is no solution for observing the effects of temperature on the movement of the casting core, so that certain metal parts, in particular turbomachine parts, produced by a manufacturing process, are not always easy to observe. Lost wax castings do not meet specifications and are scrapped.

[0007] There is a need to resolve all or part of the aforementioned drawbacks. Summary of the invention

[0008] The objective of the present invention is to provide a solution making it possible to monitor and study the behavior of the core and the shell mold during a process for manufacturing a metal part by lost wax casting in order to limit manufacturing defects of these blades by such a process.

[0009] Another objective of the invention is to better characterize the phenomena resulting from the differential expansion between the two ceramics constituting the shell mold on the one hand and the core on the other hand.

[0010] We achieve this objective in accordance with the invention by means of a characterization test device for a manufacturing process for lost wax casting of a turbomachine part, the test device comprising: a shell mold test piece made of refractory material extending along a main axis and comprising an internal cavity extending along the main axis, and - a test core, representative of a foundry core, installed in the internal cavity and fixed to the shell mold test piece by means of anchoring means, the shell mold test piece comprising at least one observation window which is formed in a wall of the shell mold test piece and which opens into the internal cavity.

[0011] Thus, this solution makes it possible to achieve the aforementioned objective. In particular, the observation window makes it possible, on the one hand, to observe any displacements of the test core relative to the shell mold specimen and to study the behavior of the materials (core and shell mold) in the event of differential thermal expansion thereof and, on the other hand, to study anchoring techniques used in a lost wax manufacturing process for a hollow metal part, in particular a turbomachine, during certain steps of the process which are, for example, the sintering of the shell mold and the preheating of the shell and the core. It should be noted that such a characterization test device is also simple and easy to implement, and also inexpensive to produce.

[0012] The characterization test device also comprises one or more of the following features, taken alone or in combination:

[0013] - the shell mold test piece has a generally cylindrical shape with an axis main and circular cross-section.

[0014] - the test core has a cylindrical body extending along an axis elongation and anchoring means projecting transversely from the cy- body lindric.

[0015] - a radial clearance is delimited in the internal cavity between a first end of the test core and a first end of the shell mold specimen, the anchoring means are located at a second end opposite the first end along the elongation axis of the test core.

[0016] - the test core is made of a refractory material different from the refractory material fractory of the shell mold test piece or in a metallic material.

[0017] —the core has a section along the elongation axis having a T shape.

[0018] The invention also relates to an installation for characterization tests. The installation comprises: - an enclosure comprising at least one heating zone, - at least one characterization test device, having any of the above-mentioned characteristics, arranged in the enclosure, and - an image acquisition device of the characterization test device carried by a transverse wall of the enclosure.

[0019] The installation also includes one or more of the following features, taken alone or in combination:

[0020] - several characterization test devices are arranged in a cluster around a central axis.

[0021] - the image acquisition device is included in the group comprising a camera, an optical sensor.

[0022] - the image acquisition device is equipped with a colored filter, preferably a blue filter, intended to allow the visualization of control markings made on a border delimiting the observation window.

[0023] The invention also relates to a method for manufacturing at least one characterization test device. The manufacturing method comprises the following steps: - manufacture of at least one test core representative of a foundry core and equipped with anchoring means, - injection of a consumable material around the test core so as to produce a model in consumable material, - production of a shell mold test piece in refractory material enveloping the model in consumable material and at least part of the test core, - removal of the consumable material model so as to obtain an internal cavity inside the shell mold specimen and fixing the test core to the shell mold specimen using anchoring means, and - cutting out at least one observation window for the test core in a wall of the shell mold specimen.

[0024] The manufacturing method also comprises one or more of the charac- characteristics and / or following steps, taken alone or in combination:

[0025] - the step of manufacturing at least one test core comprises a sub-step of shaping the test core by additive manufacturing or by injection of a mixture comprising a binder and a powdery material, the powdery material comprising at least one refractory material or a metallic material.

[0026] - the step of manufacturing at least one test core comprises the sub-steps following of: —debinding of the test core obtained during the shaping sub-step so as to eliminate all or part of the binder, —sintering of the test core after the debinding sub-step so as to consolidate the test core, — first check of the test core after the sintering sub-step, —impregnation of the test core from an impregnation material after the first control sub-step, and — second test core check after the impregnation sub-step.

[0027] - the step of producing the shell mold test piece comprises at least two sub-steps of successive deposition of slip layers comprising a refractory material, each sub-step of slip deposition being followed by sub-steps of draining, sanding, and drying of the slip layer.

[0028] The invention also relates to a method for characterization testing from a characterization testing device as mentioned above, the method comprising the steps of: - installation of control markings at least on part of a border delimiting the observation window, - installation of the characterization test device in a heating zone of an enclosure, - application of a predetermined temperature in the heating zone, and, - optical acquisition of the characterization test device during temperature application.

[0029] According to a characteristic of the characterization test method, the control markings are made from a coating of refractory and thermoluminescent material.

[0030] According to another advantageous characteristic or step of the characterization test method, the latter comprises a step of comparing the markings acquired during the acquisition step with reference markings. Brief description of the figures

[0031] The invention will be better understood, and other objects, details, characteristics and The advantages thereof will appear more clearly on reading the detailed explanatory description which follows, of embodiments of the invention given as purely illustrative and non-limiting examples, with reference to the appended schematic drawings in which:

[0032] - [Fig.l] represents an example of a characterization test device according to the invention;

[0033] - [Fig.2] represents, in a partial and longitudinal section, an example of a tur- machine according to the invention;

[0034] - [Fig.3] is a perspective view of an example of a turbomachine blade capable of being manufactured by a lost wax manufacturing process;

[0035] - [Fig.4] is a schematic view of an example of a character testing device risation comprising a test core in a shell mold specimen according to the invention;

[0036] - [Fig.5] is a schematic view of the characterization test device with a observation window of the test core made in the shell mold specimen according to [Fig.4];

[0037] - [Fig.6] illustrates an example of a test core according to the invention;

[0038] - [Fig.7] represents an example of a flowchart of a manufacturing process of a testing device according to the invention;

[0039] - [Fig.8] represents an example of a flowchart of a manufacturing step of a test core according to the invention;

[0040] - [Fig.9] is a schematic and axial sectional view of a ca testing device characterization after a step of injecting consumable material around a test core according to the invention;

[0041] - [Fig. 10] is a perspective and axial sectional view of a testing device for characterization after a step of producing an observation window in the shell mold according to [Fig.9];

[0042] - [Fig. 11] represents an example of a flowchart of a characterization testing method terization according to the invention;

[0043] - [Fig. 12] is a front view of an exemplary characterization test device with means for visualizing possible differential thermal expansion and applied to the shell mold test piece according to the invention;

[0044] - [Fig. 13] is a longitudinal sectional view of an example of an installation allowing the implementation of a characterization method according to [Fig.l 1]; and,

[0045] - [Fig. 14] represents an example of a characterization test device cluster according to the invention. Detailed description of the invention

[0046] [Fig.l] represents a characterization test device 1 comprising at least one shell mold specimen 2 and a test core 3 arranged in the shell mold specimen 2. This characterization test device 1, as its name indicates, will make it possible to carry out characterization tests to study the behavior and thermomechanical properties of a shell mold and a foundry core during different temperature variations which can lead to defects in a final metal part obtained from a lost wax or lost model manufacturing process. The temperature variations cause differential thermal expansions, in particular expansions which can be significant at the shell mold and involve a displacement of the foundry core.

[0047] The metal part is hollow and may be, for example, a turbomachine blade for an aircraft.

[0048] A turbomachine 20, shown for example in [Fig. 2], comprises in a known manner and from upstream to downstream relative to the direction of circulation of the gases in the turbomachine, along an axis of rotation X of the turbomachine, a fan 21, at least one compressor (such as a low-pressure compressor 22 and a high-pressure compressor 23), an annular combustion chamber 24, at least one turbine (such as a high-pressure turbine 25 and a low-pressure turbine 26), and a nozzle (not shown). The fan 21 is shrouded by a fan casing 27 but may be unshrouded. The compressor 22, 23 and the turbine 25, 26 each comprise at least one stage composed, along the axis of rotation X, of a rotor blade blading and a stator blade blading.

[0049] [Fig. 3] shows an example of a rotor blade 30 for a turbine 25, 26. This extends radially relative to the axis of rotation X. Each blade 30 comprises a root 31 mounted in a cell (not shown) of a disk (not shown) of the turbine engine and a blade 32 extending from the root 31. The blade 32 is connected to the root 31 via a platform 33. The blade 32 comprises a free end 34 opposite the root. The blade 32 has an aerodynamic shape and comprises a pressure face 32i and an extrados face 32e which are connected by a leading edge 32a and a trailing edge 32b.

[0050] The blade 30 is made of a metallic material. Advantageously, the metallic material is chosen from nickel-based alloys or superalloys which may be of equiaxed, columnar or monocrystalline structure. Such materials have the advantage of resisting high temperatures and therefore of allowing the implementation of this type of blade near the combustion chamber 24, in an environment subjected to high temperatures.

[0051] Advantageously, the blade 30 is hollow. In particular, the blade 30 is equipped with a cooling circuit 35 which is arranged inside the blade 32 and which is intended to cool the walls of the blade 32 subjected to the high temperatures of the primary air flow F1 (see [Fig.2]) passing through the compressor 22, 23, leaving the combustion chamber 24 then passing through the turbine 25, 26. This internal cooling circuit 35 makes it possible to improve resistance to high temperatures. The cooling circuit 35 comprises, for example, several channels (not shown) which communicate with each other so as to form a trombone-type duct. This trombone configuration (with passages or turns (of approximately 180°)) allows a cooling fluid to sweep the entire blade 32 and from top to bottom along the radial axis Z. The radial axis Z is perpendicular to the axis of rotation X. The cooling of the blade 32 is then optimized. The cooling fluid which circulates in each blade 30 is, for example, air taken from the low-pressure compressor 22.

[0052] Each blade 30 is manufactured for example using a lost wax casting manufacturing process or lost model. Advantageously, the manufacturing process is implemented in a lost wax casting installation (not shown). The manufacturing process of the hollow blade 30 (with for example the cooling circuit 35) generally comprises the manufacturing of a foundry core intended to form at least a portion of the cooling circuit, the injection of a consumable material around the foundry core to form a model of the blade, the production of a shell mold around the model, the removal of the model to form an internal cavity inside the shell mold, the heat treatment of the shell mold, the casting of the molten metallic material into the internal cavity of the shell mold, the cooling of the metallic material, the demolding of the blade, and the removal of the core.During the heat treatment and casting of the molten metallic material, the foundry core may move, which may impact the characteristics of the blade, in particular the thickness of the intrados 32i and / or extrados 32e surfaces or the section of the cooling circuit 35.

[0053] With reference to Figures 4 and 5, the shell mold test piece 2 is representative of a shell mold and extends along a main axis A. The shell mold test piece 2 has a generally cylindrical shape along the main axis A. Advantageously, the cylindrical shape has a circular section. This shape facilitates the manufacture of the shell mold test piece and subsequent characterization tests. The shell mold test piece 2 extends between a first end 4 and a second end 5.

[0054] As can be seen in [Fig. 4], the shell mold test piece 2 comprises two ears 6 which are located on either side of its longitudinal wall 7 (cylindrical in shape) and radially relative to the main axis thereof. The ears 6 are located towards the second end 5 of the shell mold test piece 2.

[0055] In [Fig. 5], we see that the shell mold test piece 2 is provided with an internal cavity 8. The latter is delimited by the longitudinal wall 7 of the shell mold test piece 2. The internal cavity 8 extends along the main axis A and advantageously opens at the first end 4 of the shell mold test piece 2. More precisely, the shell mold test piece comprises a closed bottom 9 (shown in dotted lines in [Fig. 5]) and an opening 10 delimited by a free edge of the first end 4. The internal cavity 8 opens through this opening 10

[0056] The shell mold test piece 2 is advantageously made of a first refractory material. The first refractory material is, advantageously, but not limited to, a ceramic.

[0057] With reference to Figures 1 and 5, the shell mold test piece 2 comprises at least one observation window 11 which is formed in its longitudinal wall 7. This observation window 11 makes it possible to monitor and / or control the behavior of the test core 3 inside the internal cavity 8 during one or more phases of variation of the temperature of the characterization test device. The observation window 11 passes transversely (in particular radially with respect to the main axis A) on both sides of the longitudinal wall 7. In other words, the observation window 11 opens into the internal cavity 8.

[0058] The observation window 11 is advantageously located above, along the main axis A, the ears 6. This extends along an angular sector around the main axis A of between 40° and 100°. The observation window 11 is advantageously located between the two ears 6 in the circumferential direction around the main axis A.

[0059] According to an exemplary embodiment, the observation window 11 has a height hl of between 40 mm and 60 mm along the main axis A. The height hl of course depends on the dimensions of the shell mold specimen 2 and possibly the test core 3.

[0060] [Fig. 6] more precisely represents an example of a test core 3 which is representative of a foundry core. The test core 3 is installed in the internal cavity 8 of the shell mold specimen 2 and is fixed to the shell mold specimen.

[0061] The test core 3 has a cylindrical body 13 extending along an elongation axis B. The body 13 advantageously has a circular cross-section. The body 13 extends between a first end 14 and a second end 15. The test core comprises anchoring means 12 which project transversely from the cylindrical body 13. The anchoring means 12 are configured so as to achieve the fixing of the test core 3 to the shell mold specimen 2. The anchoring means 12 are advantageously located at the second end 15 of the cylindrical body 13 and are fixed towards the second end 5 of the shell mold test piece 2. The anchoring means 12 are formed in this embodiment by two arms 16 which each extend on either side of the cylindrical body 13 and from the second end radially relative to the elongation axis B. Advantageously, each arm 16 has a circular section. The shape of the arms and of the cylindrical body facilitates the manufacture and implementation of the test core 3.

[0062] As can be seen in [Fig.6], the test core 3 has a section along the elongation axis B which has a T shape. Such a shape is very simple and quick to produce by an injection process for example.

[0063] Furthermore, the first end 14 of the test core 3 is connected to the shell mold specimen 2 by a sliding connection. For this purpose, the characterization test device comprises sliding means. Advantageously, the shell mold specimen 2 comprises protrusions 17 which extend from an inner surface 18 of the longitudinal wall of the shell mold specimen 2. The protrusions 17 extend radially from the inner surface and are diametrically opposed here. Each protrusion 17 has a bearing surface 17a (shown in particular in [Fig. 10]) which extends along the elongation axis B and which is solid. Each bearing surface 17a is opposite the cylindrical surface 13a of the cylindrical body 13. Advantageously, each bearing surface 17a is flush with the cylindrical surface 13a.A radial clearance J1 is delimited in the internal cavity 8 between the first end 4 of the shell mold test piece 2 and the first end 14 of the test core 3. This radial clearance J1 ensures the sliding of the test core along the main axis A of the shell mold test piece in the event of thermal expansion.

[0064] In order to control the radial clearance Jl, the cylindrical surface 13a may carry one or more layers of coating. Advantageously, this coating may be a paint or varnish applied manually using a brush or a spray. The layer(s) of coating is / are arranged opposite one or more protuberances 17. The coating and the protuberances define the sliding means.

[0065] Advantageously, still in [Fig. 6], the cylindrical body 13 has a height h2 which is between 60 and 150 mm. The height h2 is measured between the anchoring means 12 and the first end 14. Preferably, the height h2 is 100 mm. A core of at least 100 mm makes it possible to increase the amplitude of the displacement and to improve the measurement accuracy.

[0066] Advantageously, the test core 3 is made of a second refractory material. The first refractory material and the second refractory material are different. The second refractory material may also be a ceramic. Alternatively, the test core 3 is made of a metallic material. The metallic material may be a metal alloy. Advantageously, the metallic material comprises, for example, molybdenum and / or a molybdenum alloy. Since molybdenum (or its alloys) is metallic, it allows for the introduction of ductility when hot and also has better mechanical properties when hot than ceramics.

[0067] The characterization test device 1 is produced by a lost wax casting manufacturing method 40, the steps of which are shown in [Fig. 7]. This method comprises steps similar to that of the manufacturing of the hollow metal part (blade 30 of the turbomachine) described above.

[0068] The method comprises a manufacturing step a) of at least one test core 3 representative of a foundry core. The test core 3 can be made in two parts (the body 13 and the anchoring means 12) or be made in a single piece (made in one piece). The manufacturing step a) comprises sub-steps which are shown in [Fig.8],

[0069] With reference to [Fig.8], the manufacturing step a) comprises a sub-step a1) of shaping the test core 3. In the case where the test core 3 is formed in a single piece, the test core is advantageously shaped by the additive manufacturing technique. Additive manufacturing makes it possible to produce parts of different shapes, in particular very complex shapes.

[0070] Alternatively, the test core 3 may be shaped by a lost wax manufacturing process separate from the manufacturing process of the characterization test device.

[0071] According to yet another alternative, the test core 3 is shaped by injecting a powdery material. In particular, the injection takes place from a mixture of the powdery material and a binder. The powdery material may comprise a powder of ceramic material or a powder of metallic material. The metallic powder may comprise molybdenum, titanium, and / or aluminum. The binder allows shaping of the powders and holding of the powder to form the test core 3. The binder may advantageously comprise a polymer. The injection is advantageously carried out in a mold (not shown).

[0072] The technique for injecting the powdered material, in particular ceramic powder, may be low pressure ceramic powder injection molding (LP-CIM in English for Low Pressure Ceramic Injection Molding), medium pressure ceramic powder injection molding (HP-CIM in English for Medium Pressure Ceramic Injection Molding), or low pressure ceramic powder injection molding (HP-CIM in English for High Pressure Ceramic Injection Molding). At low pressure, the pressure is less than, for example, 10 bars, at medium pressure, the pressure is between 10 and 50 bars for example, and at high pressure, the pressure is between 10 and 50 bars for example, and at high pressure, the pressure is between 10 and 50 bars for example. pressure, the pressure is higher for example than 50 bars.

[0073] In the case where the anchoring means are added, the body 13 and the anchoring means 12 are produced separately by additive manufacturing, by the lost wax technique or by injection of powdered material.

[0074] Regardless of the technique used in the shaping sub-step a1), the manufacturing method comprises a debinding sub-step a2). During this sub-step a2), all or part of the binder is extracted. The debinding sub-step a2) can be carried out by a heat treatment in which the test core 3 is heated to a temperature allowing the compounds of the binder to be degraded. The temperature depends on the polymer used and can be, for example, between 80°C and 600°C. The test core 3 at the end of the debinding is in a “brown” test core state.

[0075] Manufacturing step a) also comprises a sintering sub-step a3). During this sub-step a3), the test core is heated to a sintering temperature of the powder material (melting point temperature of the powder material (metal powder or ceramic powder)) so as to consolidate the core. Any binder residues are removed. Sub-step a3 is carried out after sub-step a2). The test core 3 at the end of the sintering sub-step a3) is in a “grey” test core state.

[0076] The manufacturing step a) further comprises a first control sub-step a4) of the test core 3. This control sub-step a4) advantageously occurs after the sintering sub-step a3) so as to check the condition of the test core because the latter may have manufacturing defects such as cracks, shrinkage, lack of materials, opening porosities, etc. Advantageously, this sub-step a4) is carried out visually by an operator.

[0077] The manufacturing step a) comprises an impregnation sub-step a5) with an impregnation material making it possible to improve the consolidation of the test core. Advantageously, the impregnation material is a polymer material. This makes it possible in particular to increase the resistance of the test core 3 to breaking stresses at room temperature (Tamb).

[0078] The manufacturing step a) further comprises a second control sub-step a6) of the test core. This second control is intended to verify whether the dimensions of the test core 3 are consistent with the test core or theoretical model of the test core obtained by computer-aided design or drawing (CAD / CAM) using software provided for this purpose. The second control is advantageously a three-dimensional control. The latter can be carried out using a control device (not shown) which can be of the type of a Three-Dimensional Measuring Machine (CMM) or by tomography. The control can also be carried out without contact on the surface of the test core.

[0079] The method 40 for manufacturing the characterization test device comprises a step b) of injecting at least one model made of consumable material. This step b) occurs after the step a) of manufacturing the test core 3. In the present invention, the expression "consumable material" means a material that is consumed, disappears or melts at a predetermined temperature. Advantageously, the consumable material is wax or a resin. However, the consumable material may be a material equivalent to wax or resin. The consumable material is injected around the test core 3. Advantageously, the injection takes place in a mold having the shape of the model to be obtained. The consumable material is injected in particular around the cylindrical body 13 and at least partly around the anchoring means 12.

[0080] [Fig. 9] schematically illustrates an example of a model 19 made of consumable material at least partially enveloping the test core 3 after the production step b). The model 19 has a parallelepiped or cylindrical shape around the elongation axis B of the test core 3. As can be seen in [Fig. 9], each end 16a of the arms 16 of the anchoring means 12 is free of consumable material. This will allow the subsequent fixing of the core to the shell mold test piece during the production of the shell mold test piece.

[0081] The manufacturing method 40 comprises a step c) of producing the shell mold test piece 2 in refractory material enveloping at least the model 19 in consumable material. The production step c) comprises at least two sub-steps of successive deposits of a slip layer comprising the refractory material. Each sub-step of slip deposition is followed by sub-steps of draining, sandblasting (or stuccoing), and drying of the slip layer. Each slip layer may have a chemical composition, density, and / or particle size, etc. different from those of the other layers. Similarly, each slip layer may be of a thickness different from those of the others. In this way, the longitudinal wall of the shell mold test piece has layers of different thicknesses and physicochemical properties.

[0082] Advantageously, step c) comprises between 2 and 10 sub-steps of slip deposition. The different layers of slip are applied to a portion of the arms 16 and the ends 16a of the arms of the anchoring means, which secures the test core 3 to the shell mold specimen.

[0083] Concerning each sub-step of stuccoing, this is carried out from grains of sand which are applied on the layer of slip using a sprinkler or a fluidized bed. Sprinkling the sand gains makes it possible to guarantee the integrity of the layer of slip and to create a thin contact layer.

[0084] The shell mold test piece 2, once produced, has a general cy shape lindrique of main axis A. The refractory material further coats or traps each end 16 of the arms so as to fix the test core, at its second end 15, in the shell mold specimen. The coating at least of the ends of the arms 16 forms the ears 6 of the shell mold specimen 2.

[0085] The manufacturing method 40 comprises a step d) of removing the model 19 made of consumable material so as to form the internal cavity 8 inside the shell mold specimen. The removal of the consumable material model is carried out for example by a heat treatment at a temperature between 50°C and 200°C. After the removal of the model 19, the test core 3 remains fixed to the shell mold specimen 2. [Fig. 10] represents the shell mold specimen 2 free of the model which is replaced by the void forming the internal cavity 8.

[0086] The manufacturing method 40 comprises a step e) of cutting out at least one observation window 11 in the wall of the shell mold test piece. The observation window 11 is made so as to open into the interior of the internal cavity 8 and so as to observe the test core 3 fixed inside the shell mold test piece 2. This cutting step e) is carried out using a tool such as a grinder or a milling machine. [Fig. 10] represents the shell mold test piece provided with the observation window 11 obtained after step e).

[0087] The manufacturing method optionally comprises a step of producing the sliding connection between the test core 13 and the shell mold specimen. For this purpose, a removal of material is carried out in the model made of consumable material and towards the first end of the test core 3. These removals of material create a depression. In this way, during the step of producing the shell mold specimen, the slip deposits fill the depressions so as to form the protuberances 17 described previously.

[0088] The characterization test device 1 is then implemented in a characterization test method 50, the steps of which are shown in [Fig. 11].

[0089] The characterization test method 50 comprises a step f) of placing control markings 60 at least on a portion of a border 11a delimiting the observation window 11 as illustrated in [Fig. 12]. Advantageously, the markings 60 or speckles (shown schematically in the form of small squares in this example) are made with a coating of refractory material. The coating is advantageously resistant and visible at high temperatures, in particular those applied during the characterization tests. The markings will allow in situ measurement of the differential deformations / displacements between the test core and the shell mold specimen using image analysis methods. For this, the markings comprise thermoluminescent materials. An example of a thermoluminescent material is an alkali oxide with a radiation that differs from that of the shell components to provide contrast.

[0090] The characterization test method 50 comprises arranging at least one characterization test device 1 in a characterization installation 70. More specifically, the method 50 comprises a step g) of placing the characterization test device 1 in a heating zone of an enclosure.

[0091] Advantageously, several characterization test devices 1 are arranged in a cluster around a central axis D as shown in [Fig. 14].

[0092] With reference to [Fig. 14], the cluster comprises a central barrel 90 extending along the central axis D between a cup 91 and a plate 92 which are centered on the central axis D. The characterization test devices 1 are distributed around the central barrel 90 and connected to the latter by fixing arms 93. The first end of the devices is connected to the fixing arm 93 while the second end is connected to the plate 92 by means of a chicane selector 94. Each internal cavity 8 is connected to the cup 91 by means of a supply channel 95. Each internal cavity extends parallel to the central axis D. In the process for producing a cluster, the latter is molded according to the standard technique in order to form several shell mold test pieces 2.

[0093] [Fig. 13] shows partially and in a longitudinal sectional view a example of installation 70 for implementing the characterization test method. The installation 70 comprises a heating device 71 comprising an enclosure 72. Advantageously, the heating device 71 is here a furnace with a thermal gradient. The furnace can be of the Bridgman type. The enclosure 72 comprises a bottom 73 from which a side wall 74 rises along an axis of revolution C. The side wall 74 delimits the enclosure. The latter comprises a hot zone 75 and a cold zone 76 which extend along the axis of revolution and which are opposite along the axis of revolution C. Advantageously, the hot zone 75 is located in the upper part of the enclosure while the cold zone 76 is located in the lower part of the enclosure along the axis of revolution. The hot zone 75 and the cold zone 76 are partially separated by an intermediate wall 77 defined in a plane perpendicular to the axis of revolution C.The intermediate wall 77 is defined in a plane parallel to the bottom 73.

[0094] The installation 70 comprises a heating system 78 which is installed inside the enclosure and advantageously in the hot zone 75. More precisely still, the heating system 78 delimits a heating zone 79 in which the device 1 or the characterization test cluster shown schematically in [Fig. 13] is received. The variation of the thermal gradient occurs in the heating zone 79. The heating system 78 may comprise susceptors 80 which are arranged in a wall of the heating system 78 along an axis parallel to the axis of revolution C.

[0095] The installation 70 comprises a cooling system 81 which is installed inside the enclosure and advantageously in the cold zone 76. The cooling system 81 comprises for example a cooling circuit which is arranged in a portion of the wall of the enclosure.

[0096] Still with reference to [Fig. 13], the installation 70 comprises a base 82 known as the “floor” which is movable in translation along the axis of revolution C. In particular, the floor 82 moves between the hot zone 75 and the cold zone 76 of the enclosure. In particular, the floor 82 is configured so as to move the characterization test device 1 or the cluster between the hot zone and the cold zone. For this purpose, the intermediate wall 77 comprises an orifice 83 passing through it on either side along the axis of revolution. The floor 82 is intended to pass through this orifice 83. Advantageously, a movement system 84 comprises, for example, a jack making it possible to move the floor 82.

[0097] According to an exemplary embodiment, the heating system 78 has an axis coincident with the axis of movement of the floor and moves to the heating zone where the latter forms a bottom wall of the heating system 78 when the characterization test device 1 is inside the heating zone. In other words, the heating zone 79 is open at the bottom and opens into the hot zone 75 of the enclosure. Advantageously, but not limitingly, the characterization test device is placed in this heating zone 79.

[0098] Advantageously, the sole 82 is cold (approximately 20°C). The sole makes it possible to easily receive and position the characterization test device relative to the different hot and cold zones.

[0099] The installation 70 may comprise a crucible 85 installed in the hot zone and which makes it possible to melt a metallic material at a specific temperature before being poured to fill an internal cavity of a shell mold. In the context of this example, a pour is not provided to fill the internal cavity 8 of the shell mold test piece.

[0100] The enclosure comprises a transverse wall 86 which is connected to the side wall thereof. The transverse wall 86 is defined in a plane which is perpendicular to the bottom 73 of the enclosure. The transverse wall 86 comprises an opening 87 which passes through it on either side. The opening 87 has an axis coincident with the axis of the heating zone. The opening 87 opens into the enclosure.

[0101] The installation 70 comprises an image acquisition device 88 of the characterization test device during the characterization test method. In a manner Advantageously, the device 88 is fixed to the transverse wall using removable fixing means. Advantageously, the device 88 is arranged outside the enclosure. As illustrated in [Fig. 13], the installation 70 comprises a support 89 which is arranged at the location of the opening 87 and makes it possible to close the enclosure. The acquisition device 88 is located above this support and at a distance from it. The support 89 is advantageously, but not limited to, the support is made of quartz.

[0102] The acquisition device 88 is connected to a processing unit (not shown) for processing the data from the received images. The processing unit may be a computer. An example of a technique used for data analysis is digital image correlation (DIC). This technique makes it possible to track markings made in the surface of the shell mold specimen and the test core from the images taken during the temperature rise in order to estimate their displacement by expansion.

[0103] The image acquisition device 88 is advantageously equipped with a colored filter (not shown) allowing optical acquisition of the control markings 60 on the shell mold specimen 2 arranged in the enclosure. In the present example, the coating of the control markings 60 is made in a black color, the colored filter is blue. Indeed, the enclosure not being illuminated by visible light, the optical capture will take advantage of the black body radiation, the characterization test device being blank at casting temperature for example. The blue filter makes it possible to reduce the radiative power of the black body radiation and keep only frequencies in the visible range. In other words, the filter is blue in order to contrast the brightness emitted by the ceramic materials (shell, core, interior of the furnace) at very high temperatures.

[0104] Advantageously, the image acquisition device 88 comprises, for example, an optical sensor or a camera. The camera has, for example, a high resolution of the order of 64 MegaPixels. Such a configuration makes it possible to measure thermal expansions with an accuracy of approximately 5%. In other words, the camera is able to have a resolution of, for example, 50 pm in the field of observation. Advantageously, the field of observation is of the order of 6.25 per pixel.

[0105] In the exemplary embodiment, the image acquisition device 88 has a focal length f of approximately 400 mm. For such a focal length, the characterization device 1 is arranged at a distance d from the acquisition device of approximately 1000 mm. With an optical width !<= 20 mm and a field of observation of 400 mm /

[0106] f = d^=400mm-

[0107] The characterization test method 50 comprises a heat treatment step h) in the installation. The heat treatment is carried out at a predetermined temperature which is used for example when heating a shell mold before casting the molten metallic material and during which expansions occur. The predetermined temperature is for example 1500°C. The temperature is advantageously applied in the heating zone 79. Of course, the characterization test device 1 makes it possible to study the behavior of the different materials during temperature variations occurring for example during the step of casting the metallic material into the shell mold, during directed solidification or even during cooling of the shell mold.

[0108] The characterization test method also comprises a step of optical acquisition i) of the characterization test device(s) and in particular of the control marks 60. The heating zone 79 is closed by a cover 100 which prevents any visualization and which makes it possible to contain the temperature in the heating zone. The cover is opposite the floor. The cover 100 is made of an opaque material. To carry out this acquisition, the cover 100 is removed from the heating zone so as to obtain images of the control markings. During the acquisition, the blue filter allows wavelengths between 425-495 nm to pass. The markings shine with the heat (different emissivity at the shell and at the core) which makes it possible to distinguish them and to follow them in the shell and core mold test piece.More specifically, the markings will allow in situ measurement of differential deformations / displacements between the test core and the shell mold specimen. For this, a comparison of the markings is carried out with reference markings. The reference markings can be images / data of markings taken before the temperature rise, during the temperature rise, etc. The marking data is recorded in the processing unit.

[0109] In this way, with such a characterization test device and such an installation, the phenomenon of displacement of the core relative to the shell mold test piece will be studied to obtain optimized manufacturing processes and hollow metal parts with improved performance.

Claims

Claims

1. Characterization test device (1) for a manufacturing process for lost wax casting of a turbomachine part (30), the test device (1) comprising: - a shell mold specimen (2) made of refractory material extending along a main axis (A) and comprising an internal cavity (8) extending along the main axis (A), and - a test core (3), representative of a foundry core, installed in the internal cavity (11) and fixed to the shell mold specimen (2) by means of anchoring means (12), the shell mold specimen (2) comprising at least one observation window (11) which is formed in a wall of the shell mold specimen (2) and which opens into the internal cavity.

2. Characterization test device (1) according to claim 1, characterized in that the shell mold test piece (2) has a generally cylindrical shape with a main axis (A) and a circular cross-section.

3. Characterization test device (1) according to claim 1 or 2, characterized in that the test core (3) has a cylindrical body (13) extending along an elongation axis (B) and anchoring means (12) projecting transversely from the cylindrical body (13).

4. Characterization test device according to claim 3, characterized in that a radial clearance (J1) is delimited in the internal cavity (11) between a first end (14) of the test core (3) and a first end (4) of the shell mold specimen (2), the anchoring means (12) are located at a second end (15) opposite the first end (14) along the elongation axis (B) of the test core.

5. Characterization test device according to one of claims 1 to 4, characterized in that the test core is made of a refractory material different from the refractory material of the shell mold test piece or of a metallic material.

6. Installation (70) for characterization tests, the installation comprising: - an enclosure comprising at least one heating zone (79), - at least one characterization test device (1) according to any one of claims 1 to 5 arranged in the enclosure, and - an image acquisition device (88) of the characterization test device (1) carried by a transverse wall of the enclosure.

7. Installation (70) according to claim 6, in which several characterization test devices (1) are arranged in a cluster around a central axis.

8. Installation (70) according to claim 6 or 7, characterized in that the image acquisition device is included in the group comprising a camera, an optical sensor.

9. Installation (70) according to one of claims 6 to 8, characterized in that the image acquisition device is equipped with a colored filter, preferably a blue filter, intended to allow the visualization of control markings (60) made on a border (11a) delimiting the observation window (11).

10. Method (40) for manufacturing at least one characterization test device (1), the manufacturing method (40) comprising the following steps of: - manufacturing a) at least one test core (3) representative of a foundry core and equipped with anchoring means (12), - injecting b) a consumable material around the test core (3) so as to produce a model of consumable material, - producing c) a shell mold specimen (2) of refractory material enveloping the model of consumable material and at least a portion of the test core (3), - removing d) the model of consumable material so as to obtain an internal cavity (8) inside the shell mold specimen and fixing the test core (3) to the shell mold specimen by means of the anchoring means (12), and - cutting e) at least one window observation (11) of the test core in a wall of the shell mold specimen (2).

11. Manufacturing method (40) according to the preceding claim, characterized in that the manufacturing step a) comprises a sub-step al) of shaping the test core by additive manufacturing or by injection of a mixture comprising a binder and a powdery material, the powdery material comprising at least one refractory material or a metallic material.

12. Manufacturing method (40) according to the preceding claim, characterized in that the manufacturing step a) comprises the following sub-steps of: - debinding a2) of the test core obtained during the shaping sub-step so as to eliminate all of the binder, - sintering a3) of the test core after the debinding sub-step so as to consolidate the test core, - first inspection a4) of the test core after the sintering sub-step, - impregnation a5) of the test core from an impregnation material after the first inspection sub-step, and - second inspection a6) of the test core after the impregnation sub-step.

13. Manufacturing method (40) according to one of claims 10 to 12, characterized in that the step c) of producing the shell mold test piece comprises at least two sub-steps of successive deposition of slip layers comprising a refractory material, each sub-step of slip deposition being followed by sub-steps of draining, sanding, and drying of the slip layer.

14. Method (50) for characterization testing from a characterization testing device according to any one of claims 1 to 5, the method comprises the steps of: - placing f) control markings (60) at least on a part of a border (11a) delimiting the observation window (11), - placing g) the characterization device (1) in a heating zone (79) of an enclosure, - applying h) a predetermined temperature in the heating zone (79); and, - optical acquisition i) of the characterization testing device during the application of the temperature.

15. Method (50) for characterization testing according to the preceding claim, characterized in that the control markings (60) are made from a coating of refractory and thermoluminescent material.

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