Abstract:
A turbomachine rotor blade, said blade having, at the distal end thereof, a heel comprising: a platform ( 2 ) having a first edge ( 201 ) on the lower side and a second edge ( 202 ) on the upper side, at least one sealing member having a first end portion ( 301 ) on the lower side and a second end portion ( 302 ) on the upper side, said sealing member having a sealing top that extends radially outwards from said platform ( 2 ) between said first and second end portions ( 301, 302 ), characterised in that, for at least one sealing member, the heel ( 105 ) comprises, on at least at one of the edges ( 201, 202 ), a portion forming a bowl ( 5 ) extending along the end portion ( 301, 302 ) of the sealing member which corresponds to the edge ( 201, 202 ), the portion forming the bowl ( 5 ) being suitable for receiving a deposit of anti-wear material.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a rotor blade of a turbomachine. The invention also relates to a method for depositing anti-wear material on a rotor blade of the turbomachine. 
       PRIOR ART 
       [0002]    There exist rotor blades of turbomachines, comprising a lower side and an upper side, positioned on either side of a blade stacking axis. Such a blade is for example a blade of a turbine stage. Referring to  FIG. 1 , such blades have, at their distal end  103 , a heel  105 . 
         [0003]    Each heel  105  includes a platform  2  having a first edge  201  on the lower side and a second edge  202  on the upper side. Each heel  105  includes at least one seal lip  3  having a first end portion  301  on the lower side and a second end portion  302  on the upper side. The seal lip  3  is for example capable of cooperating with a stator lining, for example an abradable lining, so as to limit friction between the blade and a shroud concentric with the rotor. 
         [0004]    The seal lip  3  has a seal lip top extending radially outward from said platform  2  between said first  301  and second  302  end portions. By radial direction is meant a direction orthogonal to an axis of the turbomachine. 
         [0005]    At its proximal end  102 , the blade includes for example a root  104  by which it is attached to a disc of the rotor of the turbomachine. Several movable blades can be attached to a rotor disc, their heels  105  being then positioned edge to edge so as to form a circumferential ring. One such circumferential ring makes it possible to delimit on the outside a gas flow passage passing through the turbomachine and thus to limit possible gas leaks. 
         [0006]    In order to damp the vibrations to which the blades are subject in operation, the blades are mounted on their rotor disc with a torsional stress about their stacking axis. By stacking axis is meant the axis passing through the center of gravity of the lowest section of the blade, that is the one closest to the proximal end, and orthogonal to the axis of the turbomachine. 
         [0007]    Thus the platforms  2  of the heels  105  are designed so that each blade is given a torsional stress by pressing against its neighbors, mainly along said second portions of the lateral edges  201  and  202 . To improve the mutual support of the blades and, in particular, to avoid straddling of the heels  105  and to transmit as well as possible the stress from one blade to its neighbors, it is known to provide, along the first edge  201  and/or the second edge  202 , between the two end portions  301  and  302  of the two seal lips  3  and  4 , a profile having three portions forming a “Z,” the central part of the “Z” having a protruding edge. This edge is designed to receive a layer of anti-wear material to protect the heel  105  from friction with the adjacent blade. 
         [0008]    The deposit of the anti-wear material is done conventionally on the rough casting. However, the quantity to be deposited is relatively small and the surface to be deposited the smallest possible so as not to increase the mass of the blade and so as to limit the quantity of material used. It is thus common for overflows to occur during deposition of the anti-wear material, and that the overflows persist after machining the blade. It is then necessary to remove the overflows by manually retouching the blade. However, such a manual retouching step remains difficult, given the small dimensions of the edge and of the deposit. In addition, such a step is expensive, on the one hand, because it makes the manufacturing method of the blade more complex and prolongs it—additional checking steps being necessary—and on the other hand because it generates a considerable number of rejects. 
         [0009]    Moreover, such a heel  105  must have particular profile and a protruding edge, which also involves more complicated manufacturing for the rough part. 
       SUMMARY OF THE INVENTION 
       [0010]    One aim of the invention is to compensate these shortcomings. 
         [0011]    To this end, there is provided a rotor blade of a turbomachine, said blade having at its distal end a heel including:
       a platform having a first edge on the lower side and a second edge on the upper side,   at least one seal lip having a first end portion on the lower side and a second end portion on the upper side, said seal lip having a seal lip top extending radially outward from said platform between said first and second end portions,
 
for at least one seal lip, the heel including on at least one of its edges, a portion forming a cup extending along the end portion of the seal lip which corresponds to the edge, the portion forming a cup being designed to receive a deposit of anti-wear material.
       
 
         [0014]    The invention is advantageously complemented by the following features, alone or in any one of their technically possible combinations:
       a layer of anti-wear material deposited in each cup thus formed;   the heel includes, for at least one seal lip, at the first, respectively second edge, a first, respectively second portion forming a cup extending along the first, respectively second end portion of the seal lip, the first, respectively second, portion forming a cup being designed to receive a deposit of anti-wear material;   each portion forming a cup includes two walls extending on either side of the corresponding end portion of seal lip, the walls forming the lateral edges of the cup and the end portion of the seal lip forming the bottom of the cup;   an upstream seal lip and a downstream seal lip;   the anti-wear material is of the Stellite type;   the blade is a rough blade part before machining;   the blade is a machined blade.       
 
         [0022]    The invention further relates to a method for depositing anti-wear material on a rotor blade of a turbomachine, including the steps consisting of:
       supplying such a rough part of a rotor blade of a turbomachine,   depositing a layer of anti-wear material in each cup formed, and   machining the walls of the cup extending past the layer of anti wear material deposited,       
 
         [0026]    Furthermore, the method can include a step consisting of sanding the surface of the anti-wear layer and of the portion forming a machined cup, so as to make them smooth. 
     
    
     
       BRIEF DESCRIPTION OF FIGURES 
         [0027]    Other features and advantages of the invention will be revealed in the description hereafter of one embodiment. In the appended drawings: 
           [0028]      FIG. 1  shows a detail of a rotor blade of a turbomachine according to the prior art, 
           [0029]      FIG. 2  shows a rotor blade of a turbomachine according to an example of an embodiment of the invention, 
           [0030]      FIG. 3   a  shows a seal lip of the blade of  FIG. 2  without the deposit of anti-wear material, 
           [0031]      FIG. 3   b  shows the seal lip of  FIG. 3   a  with the deposit of anti-wear material, 
           [0032]      FIG. 4   a  shows a view along a radial axis of the heel of a rough rotor blade part according to an example of an embodiment of the invention, 
           [0033]      FIG. 4   b  shows a view along a radial axis of the heel of a rotor blade of a turbomachine after application to the rough part of  FIG. 5   a  of a method according to an example of an embodiment of the invention, 
           [0034]      FIG. 5   a  shows a perspective view of the heel of  FIG. 4   a,    
           [0035]      FIG. 5   b  shows a perspective view of the heel of  FIG. 5   a  after deposit of the anti-wear material. 
           [0036]      FIGS. 5   c  shows a perspective view of the heel of  FIG. 5   b  after machining and sanding, 
           [0037]      FIG. 6  shows in the form of a diagram of the method according to one example of an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0038]    Example of a Blade 
         [0039]    General Structure of the Blade 
         [0040]    Referring to  FIGS. 2 to 5   c , an example of a rotor blade of a turbomachine. Such a blade can for example be a blade of an airplane turbojet, for example at a low-pressure stage. 
         [0041]    The blade includes a lower side and an upper side positioned on either side of a stacking axis. The blade can thus include an airfoil  101  extending along a stacking axis of the blade. The airfoil  101  extends between a proximal end  102  and a distal end  103  of the blade. 
         [0042]    The blade includes a root  104  at its proximal end  102 , by which it is for example attached to a disc of the rotor of the turbomachine. The disc can drive the blade in rotation about an axis of the turbomachine. 
         [0043]    Heel 
         [0044]    The blade has at its distal end  103  a heel  105 . The heel  105  can be made in such a manner that, when several movable blades are attached to a rotor disc, their heels  105  are set edge to edge so as to form a rotating ring delimiting a surface of revolution about an axis of rotation of the blades. This ring has in particular the function of delimiting an outer surface of a passage for the gas flow circulating between the airfoils  101  and thus to limit possible gas leaks at the distal end  103  of the blades. 
         [0045]    The heel  105  includes a platform  2  having a first edge  201  on the lower side and a second edge  202  on the upper side. The first and second edges  201  and  202  are for example opposite lateral edges. The platform  2  can delimit on the outside the gas flow passage circulating between the blades  101 . 
         [0046]    Seal Lip 
         [0047]    The heel  105  includes at least one seal lip  3 . The seal lip  3  has a first end portion  301  on the lower side and a second end portion  302  on the upper side. The seal lip  3  has a seal lip top extending radially outward from said platform  2  between said first  301  and second  302  end portions. The heel  105  can include an upstream seal lip  3  and a downstream seal lip  4 , upstream and downstream being defined according to the direction of gas flow. The upstream  3  and downstream  4  seal lips can be made in such a manner that, when several movable blades are attached to a rotor disc, the seal lips  3  and  4  of the blades are set edge to edge so as to form a rotating ring along the axis of rotation of the blades, this ring being contained substantially within a radial plane. Such a ring makes it possible to limit the existing clearance between the blades and a stator, or a stator shroud, which surrounds them, so as to limit possible gas leaks at this location. 
         [0048]    The part of the platform  2  extending upstream of the upstream seal lip  3  constitutes an upstream portion  203  or upstream spoiler. The portion of the platform  2  extending downstream of the downstream seal lip  4  constitutes a downstream portion  205  or downstream spoiler. Between the upstream portion  203  and the downstream portion  205 , the platform  2  has a central part  204  extending between the upstream  3  and downstream  4  seal lips. 
         [0049]    For the purpose of damping vibrations to which the blades are subjected in operation, the blades can be mounted on their rotor disc with a torsional stress about their stacking axis. Thus, the platforms  2  can be dimensioned in such a manner that each blade is given a torsional stress by pressing against its neighbors at the heels  105 , mainly along the end portions of the seal lips  3  and  4 . 
         [0050]    Portion Forming a Cup 
         [0051]    For at least one seal lip  3 , for example for each seal lip  3 , the heel  105  includes, at one of its edges  201  and  202  at least, a portion forming a cup  5  extending along the end portions  301  or  302  of the seal lip  3  which corresponds to the edge  201  or  202 , the portion forming the cup  5  being designed to receive a deposit of anti-wear material  7 . Thus, the heel  105  can include, for at least one seal lip  3 , for example for all seal lips  3 , at the first  201 , respectively second  202  edge, a first, respectively second portion forming a cup  5  extending along the first  301 , respectively second  302  end portion of the seal lip  3 , the first, respectively second portion forming a cup  5  being designed to receive a deposit of an anti-wear material  7 . Compared to the prior art, the portion forming the cup  5 , along an end portion  301  or  302  of the seal lip  3 , allows stiffening of this seal lip  3  and therefore to better withstand the loads caused by contact with adjacent heels  105 . The referred figures represent portions forming a cup  5  at the upstream seal lip  3 , but such portions forming cups  5  can be present, alternatively or complementarily, at the downstream seal lip  4 . 
         [0052]    Each portion forming a cup  5  can include two walls  501  and  502  extending on either side of the end portion of the corresponding seal lip  3 . These walls thus form two faces  501  and  502  forming lateral walls of the cup  5  and the end portion of the seal lip  3  forms the bottom of the cup  5 . These walls  501  and  502  can be reworked during subsequent machining. 
         [0053]    Deposit of Anti-wear Material 
         [0054]    Thus the blade can include a layer of anti-wear material  7  deposited in each cup  5  thus formed. The [material] constituting the blade generally has poor resistance to wear and the anti-wear material makes it possible to extend its lifetime by protecting the parts subjected to wear. 
         [0055]    The layer of anti-wear material  7  can be obtained by brazing plates of a specific alloy with high hardness to the cups  5 . 
         [0056]    The layer of anti-wear material  7  can be obtained by loading this lateral face with a melted alloy. The necessary heat can for example come from an electric arc sheathed with neutral gas or even from a laser beam. The anti-wear material  7  can be a cobalt-based alloy, for example an alloy of cobalt, chromium tungsten and carbon, for example such an alloy of the type of those marketed under the brand name “Stellite,” having good anti-wear properties. The anti-wear material  7  can also be made on a rough blade from the foundry prior to machining, by Stelliting. The presence of the cup  5  in the seal lip  3  makes it possible to deposit a small quantity and without any risk of overflowing. Indeed, the portion forming the cup  5  acts like a “gutter” during deposit of the melted material, overflow being limited by the edges of the cup  5 . The edges of the walls of the cup  5  extending past the anti-wear material deposited can then be removed during subsequent machining allowing the machined blade of being obtained. 
         [0057]    The walls  501  and  502  of the cup portion  5  must thus have sufficient thickness to not melt completely during depositing of the melted anti-wear material. Their condition after depositing can however be modified during machining. Thus a thickness of 1.5 mm for the walls  501  and  502 , for example, is sufficient. Likewise, the deposit of anti-wear material  7  does not need to have imperfections because the form of the layer can be modified during subsequent machining and possible subsequent sanding. 
         [0058]    Such a blade also allows depositing of Stellite along the seal lip  3 , which provides a greater lifetime for the blade because the areas protected by the anti-wear material  7  are supported on the seal lip  3 . Moreover, such a blade allows automated depositing of anti-wear material and no longer requires any manual operation. As the material distributes itself along the cup  5 , it is thus easier to accomplish a deposit of a small quantity of material. It is thus possible to obtain, after machining, a layer of anti-wear material  7 . The layer of anti-wear material  7  has for example a thickness of 1 mm or a greater thickness. 
         [0059]    Moreover, such a blade does not require a subsequent checking stage, the portion forming a cup  5  avoiding any overflow and the final form of the portion being obtained after machining. The result is a simplification of the method for depositing the anti-wear material, and more generally of the method of manufacture of rotor blades for a turbomachine. 
         [0060]    Example Method 
         [0061]    Referring to  FIG. 6 , a method for depositing anti-wear material on a rotor blade of a turbomachine is described there. The method includes a first step  601  consisting of supplying a rough rotor blade for a turbomachine as describe above and as shown in  FIG. 5   a . The method includes a second step consisting of depositing a layer of anti-wear material  7  as described above in each cup  5  formed, to obtain a heel  105  as shown in  FIG. 5   b . The method includes a third step  603  consisting of machining the edges of the walls  501  and  502  of the cup  5  extending past the layer of anti-wear material  7  deposited, so as to obtain a machined blade as shown in  FIG. 5   c.    
         [0062]    The method can include a fourth step  604  consisting of sanding the surface of the layer of the anti-wear material  7  and of the portion forming a cup  5  after machining, so as to make them smooth.