EP2903763B1 - Method of manufacturing a component covered with an abradable coating - Google Patents

Description

FIELD OF THE INVENTION

The present disclosure relates to a method of manufacturing a part covered with an abradable coating.

STATE OF THE PRIOR ART

Many machines include moving parts that rub or otherwise rub against other parts. For example, some machines comprise a moving part rotated relative to an axis, a part of this moving part rubbing against another part. This is the case of turbomachines (terrestrial or aeronautical, such as turbojets or turbine engines) which comprise a rotor with moving blades which, in their rotational movement, rub against the inner face of the housing of the stator which surrounds them.

In the case of a turbomachine, it is usual to provide a space, or game, between the fixed parts and the moving parts, in particular between the casing and the blades, to take account, on the one hand, of the geometrical tolerances of the parts and on the other hand mechanisms of thermal expansion and creep materials over time. However, it is important to minimize the leakage of gas or air at this space. Indeed, these leaks reduce the flow rate of compressed air through the turbomachine, lose some of the useful mechanical work and, therefore, affect the efficiency of the turbomachine, increase fuel consumption and reduce the thrust produced .

To minimize these leaks, the solution currently used is to bring the blades as close as possible to the casing and to cover the casing with a coating of soft material in front of the blades. This material is abradable, which means that it has the property of being easily dug by the end of the blades in case of contact. Thus, a dawn is virtually undamaged when it rubs against this material abradable and optimizes the space between the end of the blade and the inner surface of the housing by adjusting this space to a minimum in time.

Currently, plasma deposited wear coatings are disclosed as disclosed in US Pat. FR 2 935 623 .

Alternatively, it is possible to manufacture plate portions of abradable material which are then each glued to the housing to form a complete plate. Such a process is long and expensive. In addition, bonding has many constraints: cleaning surfaces to stick, contamination problems of cleaned surfaces, poor adhesion, etc. Finally, the mechanical stresses generated during the manufacture of the plate portions of abradable material and during their bonding contribute, in operation, to the detachment of these plate portions from the surface of the casing and / or to the cracking and the premature deterioration of the plates. in use.

The present invention aims to remedy, at least in part, these disadvantages.

PRESENTATION OF THE INVENTION

• A - on fournit une ébauche de la pièce avec un logement, ce logement débouchant à la surface de l'ébauche via au moins une ouverture,
• B - on remplit ledit logement avec un matériau abradable sous forme pulvérulente, et
• C - on co-lamine à chaud l'ébauche et le matériau abradable de manière à fritter le matériau abradable et ainsi à le faire adhérer à l'ébauche pour obtenir un revêtement abradable, dans lequel, dans l'étape (C) de co-laminage, une pression est exercée sur le matériau abradable à travers l'ouverture.

The present invention relates to a method of manufacturing a part covered with an abradable coating according to claim 1, said method comprising the following steps:

• A - is provided a blank of the part with a housing, this housing opening on the surface of the blank via at least one opening,
• B - filling said housing with an abradable material in pulverulent form, and
• C - the blank and the abradable material are hot co-laminated so as to sinter the abradable material and thus to adhere it to the blank to obtain an abradable coating, in which, in the step (C) of co -laminage, a pressure is exerted on the abradable material through the opening.

The blank provided is advantageously rough hot forming (forging, rolling ...), that is to say that the blank has not yet been hot shaping. The housing can, meanwhile, be already formatted hot and / or machined.

The co-rolling achieved allows local application of hot compression on the abradable material. Typically, it is a unidirectional compression hot, normal to the inner surface of the blank. This hot compression makes it possible to sinter and compact the abradable material and to adhere it to the blank by welding-diffusion. Advantageously, the hot compression applied by the co-rolling is sufficient to sinter and compact the abradable material and adhere it to the blank, and the manufacturing method does not include any hot pressing step before or after the step of co-rolling.

Such a method makes it possible to obtain good compaction and good cohesion of the particles of the abradable material. In addition, with the temperatures and pressures engaged for co-rolling, the adhesion of the particles to the blank is good and the solder interface between the material and the blank has little or no porosity. The risk of subsequent detachment of the abradable coating is decreased.

During co-rolling, the blank and the abradable material can be shaped closer to the dimensions of the final piece, for example with straight mandrels or shaped mandrels.

In addition, since the co-rolling operation is carried out hot, recrystallization mechanisms can take place, which reduces the stresses in the abradable coating. The risks of cracking, deterioration and detachment of the coating are also reduced.

The housing opens on the surface of the blank via an opening (s). During co-rolling, pressure is exerted on the abradable material through this (these) opening (s). In certain embodiments, said housing is filled with the abradable material by this (these) opening (s) during the filling step (step B) and this (these) opening (s) is sealed with a sheath, before the co-rolling step (step C).

• D - on recouvre l'ouverture par laquelle le logement débouche à la surface de l'ébauche, avec une gaine qui présente au moins un orifice de vide et au moins un orifice de remplissage,
• E - on fait le vide dans ledit logement en utilisant ledit orifice de vide et on remplit ledit logement avec le matériau abradable (sous forme pulvérulente) en utilisant ledit orifice de remplissage, et
• F - on ferme de façon étanche ledit orifice de vide et ledit orifice de remplissage avant l'étape de co-laminage (étape C).

In some embodiments, the method comprises the following steps:

• D - covers the opening through which the housing opens on the surface of the blank, with a sheath having at least one vacuum port and at least one filling port,
• E - Vacuuming said housing using said vacuum port and filling said housing with the abradable material (in powder form) using said filling port, and
• F - sealing said vacuum port and said filling port before the co-rolling step (step C).

It will be noted that steps D to F are performed after step A and before step C above, step E returning to step B.

In certain embodiments, the co-rolling step C comprises a first preheating step C1 during which the blank is heated to a rolling temperature T, the sintering of the abradable material taking place, at least in part, during this first step, and a second step C2 during which the blank is co-laminated and the abradable material at the rolling temperature T. These steps lead to compaction of the abradable material.

Thus, initially, sintering of the particles of abradable material together, with a given porosity rate, is done during the preheating time of the blank at the rolling temperature. In a second step, during co-rolling in the strict sense, the abradable material is deformed due to the pressure exerted when hot (ie at the rolling temperature T). Thus, all the empty cavities of the housing are filled with abradable material, the dilution zones (related to welding-diffusion of the powder particles to each other) increase and the residual porosity after sintering and compacting decrease or even disappear. Recrystallization mechanisms in the abradable material can even be triggered, further improving the homogeneity of the abradable coating.

The rolling temperature (and, more generally, the thermomechanical cycle of the part) will be defined according to the smallest domain of forgeability taking into account the adiabatic warming and the domain leading to the desired microstructures of the considered materials. In particular, for forgeability, the maximum temperature will be the limit of overheating or burning of one of the shaped materials and the minimum temperature will be the limit of microstructural damage of one of the materials. For example, if the reference material is a steel, the rolling temperature T can be between 600 ° C and 1350 ° C. For a steel named EN X12CrNiMoV12 or a steel with the designation EN X4NiCoNb38, the rolling temperature T can be between 750 ° C and 1300 ° C. For a Maraging250 EN X2NiCoMo18-8 steel, the rolling temperature T can be between 850 ° C and 1250 ° C. If the material is a titanium alloy, the rolling temperature T may be between 700 ° C and 1150 ° C. For titanium alloys known as TA6V with a controlled alpha + beta structure, the rolling temperature T may be between 700 ° C. and 1050 ° C., and advantageously a temperature T of around 950 ° C. is used. For titanium alloys known as TA6V with a beta controlled structure, the rolling temperature T may be between 1050 ° C. and 1150 ° C., and advantageously a temperature T of about 1100 ° C. is used.

In some embodiments, during the step of filling the housing (ie steps B or E above), the abradable material is deposited in several layers of different types.

This makes it possible to vary the properties of the abradable coating according to the levels, the needs at the bottom of the housing not being the same as at the outer surface where the abradable coating interacts with moving parts.

In some embodiments, during the step of filling the housing (ie steps B or E above), the abradable material, in its pulverulent form, comprises base particles which, after co-rolling (Step C) constitutes the matrix of the abradable coating, and secondary particles facilitating the fragmentation of the abradable coating.

The secondary particles facilitate the fragmentation of the abradable coating during friction with the moving part, and thus the adjustment of the clearance between the moving part and the coating.

Advantageously, organic secondary particles can be introduced into the mixture of particles. Such particles will decompose during the co-rolling operation by forming gas porosities. These porosities facilitate the fragmentation of the coating.

In some embodiments, the abradable material also includes hard, wearable particles, allowing, in operation, a slight polishing of the moving parts.

In some embodiments, the housing has concave side faces (towards the interior of the housing). This makes it possible to trap the abradable coating without generating residual stresses in it or at least to distribute the stresses at the interface between the abradable coating and the substrate, which makes it possible to limit the detachment.

In some embodiments, the housing is a groove defined by an inner wall, two side walls surrounding the inner wall, and two outer lips located in the extension of the side walls and bent toward the center of the groove, so that the groove presents, in cross section, a profile of general shape in "C". Such a housing makes it possible to well imprison the abradable coating, in particular because of the outer lips which partially cover the coating and retain it.

Of course, other forms of housing can be retained, the compression at the time of co-rolling to fill the entire housing, even if it is of complex shape. In addition, during co-rolling, the housing can be deformed so as to better trap the abradable coating.

In some embodiments, the blank is formed by hot co-rolling at least two sub-parts, this co-rolling step sub-parts and the co-rolling step of the blank and the abradable material (step C above) being performed simultaneously, in a single operation.

This makes it possible to pool the tools of manufacture and to produce, in one and the same co-rolling operation, the production of the blank and the deposition of the abradable coating. This saves time and money compared to conventional manufacturing processes.

In some embodiments, after co-rolling step C, the blank and / or the coating of abradable material is machined to obtain the final piece.

In certain embodiments, after step C of co-rolling, a quality heat treatment is applied to the part as a whole, that is to say a treatment intended to give the part the desired characteristics. for his job.

In some embodiments, the part manufactured is a turbomachine casing having a radially inner face, at least a portion of this face being covered by the abradable coating. In other words, said housing is formed in the radially inner face of the housing.

The invention will be better understood and its advantages will become more apparent on reading the following detailed description of exemplary embodiments. This detailed description refers to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are diagrammatic and are not to scale, they are primarily intended to illustrate the principles of the invention.

• La FIG 1 représente, en coupe transversale, une ébauche de pièce avec un logement, ce logement débouchant à la surface de l'ébauche;
• La FIG 2 représente l'ébauche de la FIG 1, sur laquelle une gaine a été mise en place.
• La FIG 3 illustre une étape de remplissage du logement avec un matériau abradable sous forme pulvérulente.
• La FIG 4 illustre une étape de co-laminage de l'ébauche et du matériau abradable.
• La FIG 5 illustre une étape d'usinage.
• La FIG 6 est une figure analogue à la FIG 3, illustrant une étape de remplissage du logement avec un autre matériau abradable.
• La FIG 7 est une figure analogue à la FIG 3, illustrant une étape de remplissage du logement avec un matériau abradable déposé en plusieurs couches.
• La FIG 8 est une figure analogue à la FIG 4, illustrant une étape de co-laminage.

In these drawings, from one figure (FIG) to another, elements (or parts of element) identical or having a similar function are identified by the same reference signs.

• The FIG 1 represents, in cross-section, a part blank with a housing, this housing opening on the surface of the blank;
• The FIG 2 represents the draft of the FIG 1 , on which a sheath has been put in place.
• The FIG 3 illustrates a step of filling the housing with an abradable material in powder form.
• The FIG 4 illustrates a co-rolling step of the blank and the abradable material.
• The FIG 5 illustrates a machining step.
• The FIG 6 is a figure similar to the FIG 3 , illustrating a step of filling the housing with another abradable material.
• The FIG 7 is a figure similar to the FIG 3 , illustrating a step of filling the housing with an abradable material deposited in several layers.
• The FIG 8 is a figure similar to the FIG 4 , illustrating a co-rolling step.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments are described in detail below, with reference to the accompanying drawings. These examples illustrate the features and advantages of the invention. However, it is recalled that the invention is not limited to these examples.

The FIGS 1-5 illustrate different steps of an exemplary method of manufacturing a part 1 with an abradable coating 50. This part 1 is represented on the FIG 5 . Part of the abradable coating 50 forms a layer 55 on the surface of the part 1. In the example, this layer 55 projects slightly outwardly with respect to the remainder of the part 1.

In this example, the part 1 is a turbomachine casing, eg a turbojet compressor casing. This housing has an abradable coating 55 against which moving parts 60 (see FIG 5 ) come rub. These moving parts 60 are blades. The free surface 35 on which the abradable coating 55 is located is the radially inner face of the casing. This is a generally cylindrical surface, centered on the axis of rotation of the rotor of the turbomachine.

Of course, the invention could be applied to other parts than to a turbomachine casing.

To manufacture part 1, a blank 10 of this part is first provided. This sketch 10, shown on the Fig. 1 has a housing 20. The housing 20 opens out to the surface 15 of the blank 10 via an opening 25. This opening 25 is continuous. It can also be discontinuous, that is to say composed of several sub-openings.

In the example, the housing 20 is a groove that extends in a direction perpendicular to the sectional plane of the figures. Preferably, the shape of the housing 20 is chosen to trap the abradable coating 50 described hereinafter.

Advantageously, the maximum section of the housing 20 in a plane parallel to the surface 15 is at a non-zero distance from this surface. Thus, the housing 20 has at least one convergent portion approximating the opening 25. In this way, the abradable material 50 which fills the housing 20 (see below), once it forms a block of one piece, is mechanically held in the housing 20.

In the example, the housing 20 is a groove defined by a bottom wall 21, two side walls 22 surrounding the inner wall, and two outer lips 23 located in the extension of the side walls and folded towards the center of the groove. This groove thus has, in cross section, a profile of general shape in "C". The opening 25 is defined between the outer lips 23. In cross section, the side surfaces of the groove, defined by the side walls 22, are concave towards the inside of the groove. Of course, other forms of housing 20 may be retained.

The housing 20 is, for example, made by machining in the blank 10. The blank 10 may already, before machining, have a depression at the place where the housing 20 will be machined. This depression can be achieved at the time of the formatting of the sketch 10.

After completion, the housing 20 is cleaned.

The opening 25 of the housing 20 is then covered with a sheath 30 which has empty openings 31 and filling openings 32. over the entire periphery of the opening 25, on the edge of the lips 23 of the housing. This fixing is, for example, performed by welding. The size of the sheath 30 and the position of the welds can be optimized to avoid leakage.

The sheath 30 is made of a sufficiently flexible and ductile material and of sufficiently small thickness to deform under the effect of the pressure P which will be applied during co-rolling (see below). The sheath 30 closes the opening 25 in a sealed manner with the exception of the orifices 31, 32.

The housing 20 is then evacuated (i.e. in the closed space delimited by the housing 20 and the sheath 30) while filling the housing 20 with an abradable material 50 in pulverulent form. The fact that the abradable material 50 is in the form of a set of disjoint particles allows this filling.

The abradable material 50 consists of a set of particles. By particle is meant a small element which may, in particular, have a grain shape, substantially spherical, or a more elongated one-dimensional (fiber-type) or two-dimensional (platelet-type). These particles are in whole or in majority in a sinterable material, that is to say which is able to diffuse a particle to an adjacent particle when the particles are compacted at high temperature, so that links are created between the particles: the material is then sintered. During sintering, it does not necessarily occur melting of the material constituting the particles. In a sintered material, there may therefore remain porosities. If the material is compacted at even higher temperatures, deformation of the particles occurs followed by diffusion bonding and thus a gradual disappearance of the empty porosities.

The abradable material 50, in its powder form, may be a base powder 51. It may be a single powder or a mixture of powders. After co-rolling, this base powder 51 constitutes the matrix of the abradable coating 55.

In this example, the abradable material 50 is, for example, a mixture based on metal powders, such as powders made of Ni-based or Fe-based special alloy. The abradable material is chosen according to the properties required, in particular thermal properties. .

According to another exemplary embodiment represented on the Fig. 6 , in addition to the base powder 51, the abradable material 50 consists of secondary particles 52 mixed with the base powder, which facilitate the fragmentation of the abradable coating 55 in operation. These secondary particles 52 may be organic, inorganic, metallic, intermetallic particles, etc., whose chemical interaction with the base of the abradable material is weak. For example, as secondary particles 52, it is possible to use oxides, carbon-based particles such as, for example, pure carbon powders, carbon fibers or carbides (SiC, TiC, WC, etc.), particles with boron base such as borides or borates (TiB2, SiB2, lava phases, etc.), nitrides, micro-beads organic resin vaporization point slightly lower than the rolling temperature. These secondary particles 52 facilitate the stalling of pieces of abradable coating 55 to the passage of the moving part 60 with which the part 1 interacts. The secondary particles 52 may have two modes of action. Either these particles 52 resist co-rolling and remain in solid form in the matrix of the abradable coating 55, thus creating irregularities that weaken the structure of the matrix. To this end, it is possible to use mineral, metal or intermetallic particles and, for example, oxides, carbon-based particles, boron-based particles, nitrides. Either these secondary particles 52 are hollow and / or decompose by releasing a gas during co-rolling, thereby creating porosities that weaken the matrix structure. To this end, it is possible to use metal micro-beads and / or organic resin, having a vaporization point slightly lower than the rolling temperature. These micro-beads may, for example, be hollow resin balls or metal balls hollow, with vacuum or gas inside, or hollow metal balls with resin inside.

The secondary particles 52 may also be "weary", i.e. selected for their wear resistance properties. These particles then allow, in operation, to slightly polish the moving parts. For this purpose, it is possible to use inorganic, metallic or intermetallic particles and, for example, oxides, carbon-based particles (eg carbon powder, carbon fibers, carbides), boron-based particles. (eg borides or borates), nitrides.

According to another exemplary embodiment represented on the Fig. 7 the abradable material (in pulverulent form) is deposited in several layers 56, 57, these layers being of different natures. By two layers of different natures, we mean two layers made of different materials, or a layer consisting of a mixture of materials and another layer consisting of a mixture of the same materials but in different proportions.

In other words, the housing 20 is filled by a stack of layers 56, 57, each layer having a specific composition. The composition of each layer will depend on the desired functions for this layer. In the example of the Fig. 7 , the first layer 56, which is closest to the bottom wall 21 of the housing 20, is, for example, made of an alloy having a high diffusion bonding and high tenacity in contact with the substrate, so as to accommodate the constraints at the interface with the substrate as much as possible. Furthermore, the second layer 57, which is intended to come into contact with the moving part 60, is, for example, made of an alloy with a high refractory content, and possibly secondary particles, so as to promote adaptability and the thermal stability of the surface over time. For example, if the crankcase material is a steel of EN X12CrNiMoV12 name, the fact of depositing a first layer 56 of Fe-based powder makes it possible to obtain a better diffusion bonding of the powder particles on the substrate. This welding improves the behavior of the abradable. In addition, the fact of adding a final layer 57 based on Ni powders brings to the surface of the abradable coating a better heat resistance.

Of course, more than two layers could be deposited. To successively deposit layers of different compositions, several methods are possible. For example, a first method consists in modifying the mixture of particles deposited as filling of the housing (the filling can be optimized with the number of filling orifices) before evacuating. A second method consists in filling the sub-layers one by one by depositing an interlayer sheet (e.g. a metal foil) between two sub-layers, and ending with the deposition of the sheath 30 before evacuating. A third method is to project cold or hot abradable material 50 in the housing 20 via the opening 25 to have a mechanical cohesion by successive layer before welding the sheath 30 and evacuate.

Once the housing 20 is completely filled with abradable material 50, the vacuum port 31 and the filling port 32 are closed, so that the housing 20 is sealed. The FIG 3 illustrates this step.

The volume defined by the wall of the housing 20 and the sheath 30, called initial volume, is strictly greater than the volume of the housing 20, the volume of the housing 20 being defined by the wall of the housing 20 and a plane which is located in the extension of the surface 15 on which opens the opening 25.

Then, the blank 10 and the abradable material 50 are co-laminated under heat so as to sinter and compact the abradable material and to adhere it to the blank, in order to obtain an abradable coating 55. Co-rolling makes it possible to apply a pressure P greater than the atmospheric pressure on the outer face of the sheath 30. Thus the sheath 30 is deformed under the effect of a stress (unidirectional and normal to its surface 15 in the example). This stress subjects the abradable material 50 to compression in the housing 20 (the abradable material 50 being also constrained by the walls of the housing 20), the abradable material 50 being also subjected to a temperature T, generally greater than 150 ° C, so that sintering occurs between the particles of the abradable material 50 and a compaction of this material. material in the dwelling 20. The figure 4 illustrates this step.

For hot co-rolling, a hot circular rolling technique or the like can be used. An example of a hot circular rolling technique is described in the publication entitled " A summary of ring rolling technology. I - Recent Trends in Machines, Processes and Production Lines Mach. Tools 14, Vol 32, n [deg.] 3, 1992, pp. 379-398 , made by the authors Eru E. and Shivpuri R. In particular, it is possible to use two rotary mandrels which compress the blank 10 and the abradable material 50, one of these mandrels following the surface of the blank at which it is located the opening 25 of the housing 20 so as to exert pressure on the abradable material 50 via the opening 25. In the example of the FIG 4 , two rotary chucks (with vertical axes on the figure 4 ) 71, 72 compress the blank 10 and the coating 50 and reduce the thickness of the blank 10 by increasing its diameter. One of the mandrels 72 is in contact with the surface 15 and the sheath 30 and exerts a pressure P thereon. Two cones (not shown and horizontal axes in the figure) can be used to limit the increase in the height of the blank 10 may result from the action of the mandrels 71, 72. It can then proceed to a heat treatment of income. Thus, a piece of circular revolution is obtained with an abradable coating 55.

The co-rolling is carried out hot at a temperature T greater than the temperature at which all the porosities of the abradable material 50 are resorbed. Typically, this temperature T is between 700 ° C and 1300 ° C. The sintering and compacting of the abradable material 50, and therefore its densification, begin during the heating during which the blank is maintained at the temperature T during a holding time, and without pressure. Compaction ends during the co-rolling step proper. During co-rolling, the pressure P exerted by the roller 72 on the abradable material 50 via the opening 25 is a function of the own flow stress of the abradable material at the rolling temperature. The flow stress of the abradable material is significantly lower than that of the substrate, which therefore allows better deformation of the layer of abradable material.

In this example, there is little or no porosity within the abradable coating 55 after co-rolling. As a result, the resilience of the abradable coating 55 is improved.

In addition, in the housing 20, the adhesion of the particles of abradable material 50 to the surface of the wall of the housing 20 is improved. The risk of subsequent detachment of the abradable coating 55, in operation, is decreased.

After co-rolling, the abradable material 50 is sintered and compacted and occupies a volume (called the final volume) which is smaller than the initial volume, due to the compaction and sintering that took place between the particles of the material.

The temperature and pressure are then lowered to room temperature and ambient pressure respectively. The assembly is then machined to remove the sheath 30 and to give the piece 1 its final shape, as shown in FIG. FIG 5 .

In the example, the surface of the blank (especially at the lips 23) and the side edges of the abradable coating 55 are machined so as to obtain an abradable coating strip 55, slightly protruding from the rest of the free surface 15 of the workpiece 10. The moving part 60 rubs against this abradable coating strip 55 in operation, until the clearance between the coating 55 and the workpiece 60 (shown in phantom) is optimized, as shown in FIG. the FIG 5 .

According to another exemplary embodiment represented on the FIG 8 the blank 10 is formed by hot co-rolling at least two sub-portions 11, 12.

For example, in the case of a turbomachine casing, the first portion 11 may be of titanium alloy and the second portion 12 of steel or nickel base alloy. These two parts 11, 12 may be separated by an anti-diffusion intermediate film 13. The first part 11, which constitutes the titanium alloy bearing structure, is protected from the risks of titanium fire by the second part 12. The housing 20 receiving the abradable coating 55 is formed in this second part 12.

To produce the blank 10, the parts 11, 12, 13 are co-laminated and, advantageously, they are co-laminated at the same time as the part 12 and the abradable coating 55, in one and the same operation.

This reduces the manufacturing time and pool equipment.

Finally, a quality heat treatment can be applied to room 1.

Claims (11)

1. A method of fabricating a part (1) covered in an abradable coating (55), the method comprising the following steps:

   (A) providing a blank (10) for the part, the blank having a housing (20) opening out into the surface (15) of the blank (10) through at least one opening (25);

   (B) filling the housing (20) with an abradable material (50) in powder form; and

   (C) hot-rolling the blank (10) and the abradable material (50) together so as to sinter the abradable material and cause it to adhere to the blank, in order to obtain an abradable coating (55),

   wherein, during the rolling step (C), pressure is exerted on the abradable material (50) through the opening (25).
2. A fabrication method according to claim 1, wherein said housing (20) is filled with the abradable material (50) through the opening (25), and wherein the opening (25) is closed hermetically with a sheath (30) before the rolling step (C).
3. A fabrication method according to claim 1 or claim 2, wherein:

   (D) the opening (25) is covered with a sheath (30) that presents at least one vacuum orifice (31) and at least one filling orifice (32);

   (E) a vacuum is established inside said housing (20) by using said vacuum orifice (31), and said housing (20) is filled with the abradable material (50) by using said filling orifice (32); and

   (F) said vacuum orifice (31) and said filling orifice (32) are closed in leaktight manner before the rolling step (C).
4. A fabrication method according to any one of claims 1 to 3, wherein the rolling step (C) comprises a preheating first step (C1) during which the blank (10) is heated to a rolling temperature (T), with the sintering of the abradable material (50) taking place, at least in part, during this first step, and a second step (C2) during which the blank (10) and the abradable material (50) are rolled together at the rolling temperature (T).
5. A fabrication method according to any one of claims 1 to 4, wherein during the step (B, E) of filling the housing (20), the abradable material (50) is deposited as a plurality of layers (56, 57) of different kinds.
6. A fabrication method according to any one of claims 1 to 5, wherein the abradable material (50) in powder form comprises a base powder (51) that, after sintering, constitutes the matrix of the abradable coating (55), together with secondary particles (52) mixed with the base powder and facilitating fragmentation of the abradable coating (55).
7. A fabrication method according to any one of claims 1 to 6, wherein said housing (20) is a groove defined by a bottom wall (21), two side walls (22) surrounding the bottom wall, and two outer lips (23) situated extending the side walls (22) towards the center of the groove in such a manner that the groove presents a generally C-shaped profile in cross-section.
8. A fabrication method according to any one of claims 1 to 7, wherein the blank (10) is formed by hot rolling together at least two sub-portions (11, 12), and wherein the step of rolling together the sub-portions and the step (C) of rolling together the blank (10) and the abradable material (50) are performed simultaneously as a single operation.
9. A fabrication method according to any one of claims 1 to 8, wherein after the rolling step (C), the blank (10) and/or the coating (55) of abradable material is/are machined.
10. A fabrication method according to any one of claims 1 to 9, wherein, during the rolling step (C), one of the rolling mandrels (72) is in contact with the surface (15) into which the housing (20) opens out and exerts a pressure (P) thereon.
11. A fabrication method according to any one of claims 1 to 10, wherein the fabricated part is a turbomachine casing having a radially inner face, at least a portion of the radially inner face being covered by the abradable coating.

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