EP3830314A1

EP3830314A1 - Method and device for improving the surface condition of a turbomachine component

Info

Publication number: EP3830314A1
Application number: EP19766296.8A
Authority: EP
Inventors: Romaric Jean-Marie PIETTE; Françoise Bertrand
Original assignee: Safran Aircraft Engines SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 2018-07-31
Filing date: 2019-07-31
Publication date: 2021-06-09
Anticipated expiration: 2039-07-31
Also published as: CN112313364B; FR3084601B1; US11655545B2; WO2020025902A1; FR3084601A1; EP3830314B1; US20210317585A1; CN112313364A

Abstract

The invention concerns a method for the surface treatment of a component (1), for example a turbomachine component, the component comprising a surface to be treated, the method comprising the following steps: loading a first dispenser (2) with a chemical etching solution and a second dispenser (3) with a rinsing solution, positioning the first dispenser and the second dispenser opposite the surface to be treated, moving the first dispenser and the second dispenser along the surface to be treated, such that the surface to be treated successively receives the chemical etching solution followed by the rinsing solution.

Description

METHOD AND DEVICE FOR IMPROVING THE SURFACE CONDITION

A TURBOMACHINE PART

TECHNICAL FIELD OF THE INVENTION AND STATE OF THE ART

The present invention relates to the surface treatment of parts of a turbomachine, preferably metallic, in order to improve the surface condition thereof.

The invention finds an advantageous application for the surface treatment of turbomachine blades after their machining.

10

Parts exposed to the flow of air in a turbomachine are subject to severe aerodynamic performance requirements. One of the determining parameters for optimizing the operating cycles of the turbomachine is the surface condition of the parts which are directly exposed to the air flow. The rotating elements of the turbomachine, in particular the blades of compressors and turbines, must be the subject of particular attention.

At the end of the standard machining operations of the turbomachine blades, blade surfaces are obtained having a roughness Ra of less than 1.6 micrometers. It is recalled that the roughness Ra designates the mean difference between successive microscopic peaks and troughs of a surface. However, a roughness Ra of 1.6 microns is still considered too high for certain applications.

To further reduce the roughness of the blade surfaces, it is known to use manual or automated polishing with an abrasive belt or with an abrasive paste, or an electrolytic polishing. These operations make it possible in particular to reduce the roughness of the surface of the blades, or even to deburr them, that is to say to remove a local excess of material which creates a surface irregularity.

It is also known to deburr the machined surface of a part by tribofinishing, by immersing the part in a matrix comprising an abrasive substance, and by putting the part in movement in said matrix. The movement of the part generates friction between the abrasive substance and the workpiece surface. Among the machines known for the automation of such a tribofinishing treatment, some comprise a tank filled with abrasive product and driven by an oscillatory or vibratory movement. Other known devices provide means for rotating the parts to be treated, within a fixed matrix comprising the abrasive substance.

The known methods however have the drawback of being very difficult to be adapted to treat only part of a part. In the case of turbomachine blades, certain applications require only localized treatment of the blades at the leading edge and / or the trailing edge, which are the most critical zones for the aerodynamic performance of the blade. Even if only a localized treatment of a part would be necessary, the known polishing or tribofinishing machines do not make it possible to reduce the duration of treatment and to exclusively target certain parts of the surface of a part.

In addition, for a machine providing for the immersion of the parts to be treated in an abrasive product matrix, said matrix must include a large quantity of abrasive product, and possibly a solid medium to communicate the movement of the machine to the matrix. Such a machine thus consumes more abrasive product than is necessary to treat the parts, and requires additional equipment to form the solid medium.

Finally, certain areas of the parts are inaccessible during a tribofinishing treatment.

GENERAL PRESENTATION OF THE INVENTION

There is therefore a need for a method of treating the surface of parts, in particular metal parts after machining, which is automated to guarantee the reliability and repeatability of the results, while allowing only localized treatment of the parts to be targeted. critical surfaces possibly inaccessible with known methods. We are also looking for a surface treatment method with increased speed compared to known methods.

There is an additional need for a process which consumes little abrasive product.

The present invention responds to these needs by providing a method for treating the surface of a part, for example a turbomachine part, the part comprising a surface to be treated, the method comprising the following steps:

loading of a first distributor with a chemical attack solution and of a second distributor with a rinsing solution, positioning of the first distributor and of the second distributor opposite the surface to be treated,

displacement of the first distributor and of the second distributor along the surface to be treated, so that the surface to be treated successively receives the etching solution then the rinsing solution.

In the process of the invention, the surface to be treated is first chemically attacked to reduce the roughness, then rinsed. The rinsing immediately following the chemical attack makes it possible to recover the residues detached from the surface, as well as the excess of attack solution.

The method of the invention has the advantage of allowing localized treatment, targeting a specific area of a part to be treated. It suffices to control the movement of the two distributors so as to treat this precise area.

In addition, the treatment process can be very rapid when the surface to be treated is small.

Finally, the method consumes only the quantities of chemical attack solution and rinsing solution necessary for loading the two distributors, and does not require an additional solid medium in addition to the chemical attack solution. Other optional and non-limiting characteristics of a process of the invention are the following, taken alone or in any of their technically possible combinations:

- the first distributor and the second distributor are positioned and moved relative to the surface to be treated so that the second distributor is positioned in the wake of the first distributor to apply the rinsing solution to the areas of the surface to be treated having just received chemical attack solution;

the first distributor and the second distributor each comprise a roller, a paint brush or a brush, and the positioning step comprises bringing the first distributor and the second distributor into contact with the surface to be treated of the part;

- The first distributor and the second distributor are continuously charged respectively with chemical attack solution and with rinsing solution so as to remain impregnated during the application;

- the chemical attack solution is a solution with an acid pH of less than 5, or with a basic pH of more than 9;

- the application stage is between 1 and 10 seconds per square millimeter of surface to be treated.

The invention relates, according to a second aspect, to a device for a method as defined above for treating the surface of a part, in particular a part of a turbomachine, said part comprising a surface to be treated and the device comprising:

a first distributor configured to distribute a chemical attack solution,

a second dispenser configured to dispense a rinsing solution,

a support configured to hold the first distributor in position relative to the second distributor and allow their joint movement,

displacement means configured to allow simultaneous movement of the first distributor and the second distributor along the surface to be treated so that the surface to be treated receives first the etching solution then the rinsing solution,

and a sealed housing in which the first and second distributors are positioned and configured to seal between the surface to be treated and the rest of the zones of the part situated outside the surface to be treated.

Other optional and non-limiting characteristics of said device are the following, taken alone or in any of their technically possible combinations:

- The device further comprises means for supplying chemical attack solution at the first distributor, means for supplying rinsing solution at the second distributor, and means for controlling a flow rate of the solution chemical attack and a flow rate of the rinsing solution;

the first distributor and the second distributor each comprise a roller, and the device further comprises a recovery tank configured to recover an excess of chemical attack solution and an excess of rinsing solution at the outlet of the chemical attack roller and rinse roller.

GENERAL PRESENTATION OF THE FIGURES

Other characteristics, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and not limiting, accompanied by the appended drawings among which:

FIG. 1a schematically represents a device for implementing a method of the invention, seen from above, during the treatment of a surface to be treated of a part;

Figure 1b shows schematically the same device after the treatment of the surface to be treated;

Figure 2 shows schematically the device of Figures la and lb, in a perspective view; Figure 3 shows the steps of a surface treatment method according to an embodiment of the invention;

Figure 4 is a graph whose ordinate axis represents the height of the surface of a part, on a microscopic scale, identified with respect to a central line of the part, and whose abscissa axis represents the distance along a line passing through a treated area of the workpiece and an untreated area of the workpiece;

Figure 5a is a microscope view of the surface of a part before a surface treatment according to the invention;

Figure 5b is a microscope view of the same surface after a surface treatment according to the invention.

DETAILED DESCRIPTION

In the following, a method of surface treatment by chemical attack in accordance with the invention is described, applied to a metallic blade of a turbomachine, and a device configured to implement said method.

However, those skilled in the art will understand that the method of the invention applies with the same advantages for any type of part which can be the subject of a surface treatment by chemical attack, in particular in order to reduce the roughness of such a part, or deburring it. Furthermore, the case below is described where the first distributor dispensing a chemical attack solution is a chemical attack roller, and the second distributor dispensing the rinse solution is a rinse roller. However, it will be understood that the two said distributors can have any structure allowing contact with a surface to be treated of a part, and the application of a chemical attack or rinsing solution. A first distributor or a second distributor may in particular take the form of a paint brush or a brush.

In the figures, similar elements correspond to identical reference numbers. Device for surface treatment of a part

There is shown schematically in Figures la and lb an automatic surface treatment machine according to the invention. In the view of FIG. La, a surface 1 of a turbomachine blade is being treated by passing a chemical attack roller 2 and a rinsing roller 3. During the treatment, the two rollers 2 and 3 are driven along the surface 1, by displacement means 4, in a direction of displacement X, in the direction from right to left (from the rinsing roller 3 to the chemical attack roller 2). Thus, the treated area of the surface 1 is on the right of the rollers 2 and 3 in the figures, and the area which remains to be treated is on the left of the rollers 2 and 3. In the view of FIG. 1b, the surface 1 has already been processed.

Advantageously, the surface 1 to be treated of the turbomachine blade borders the trailing edge or the leading edge of the blade. In general, the method which will be described below is of advantageous application for reducing the roughness of the surfaces most exposed to the primary or secondary flow of air in the turbomachine.

In this example, the rollers 2 and 3 are of cylindrical tubular shape, and both have a symmetry of revolution along axes parallel to the same axis Z. The rollers 2 and 3 are advantageously arranged within a sealed housing 7 and positioned side by side within said housing. The tightness of the housing 7 makes it possible to limit the area of the part which receives the chemical attack solution and the rinsing solution to the area to be treated, in particular if the area to be treated is of small area relative to the total area of the room. In addition, the sealed housing 7 contains possible projections of chemical attack solution which could otherwise reach operators. When the housing 7 is positioned against a surface of a part, an external part 20 of the roller 2 and an external part 30 of the roller 3 abut against said surface. Preferably, the rollers 2 and 3 are arranged so that they can be partially joined simultaneously against such a surface over substantially their entire length, to come into contact with said surface. By “external part” of the rollers is meant the part radially furthest from the axes of revolution of the rollers. The outer part 20 of the roller thus extends around an internal part 21 of the roller 2, and the external part 30 of the roller extends around an internal part 31 of the roller 3. The rollers 2 and 3 can advantageously be made up of several radially overlapping lamellae. In this example, the rollers 2 and 3 extend parallel to each other, along their axes of revolution, and are slightly spaced apart.

In this example, the edges of the rollers 2 and 3 (corresponding, in FIGS. 1a and 1b, to the upper part and the lower part of the said rollers) are aligned in an alignment direction X. In the present example, the direction d alignment X is orthogonal to the axes of revolution of the rollers; alternatively, the alignment direction could make an angle with respect to the direction X of the figures.

The material of the lamellae of the chemical attack roller 2 is chosen so that it can be soaked with a chemical attack solution. “Chemical attack solution” is understood to mean a solution having an abrasive character, capable of smoothing the surface of a part, in particular of a metallic part, during friction with said surface. Such a solution is suitable, when the roller 2 rubs against the surface 1, to locally attack the surface layers in order to flatten the surface. Preferably, the etching solution is acidic (pH less than 5) or basic (pH greater than 9).

The solution can include the following dosage for one liter: 500 milliliters of 95% ethyl alcohol, 500 milliliters of 35% hydrochloric acid, 20 grams of copper chloride, especially if the part to be treated is nickel-based.

Alternatively, the solution may include the following dosage for one liter: 700 milliliters of deionized water, 150 milliliters of hydrofluoric acid to 40%, 150 milliliters of 60% nitric acid, especially if the part to be treated is made of titanium.

In general, the chemical attack solution preferably comprises nitric acid and / or picric acid and / or hydrochloric acid.

The lamellae of the roller 2, in particular those of the external part 20 of the roller, are preferably made of spongy material. This type of material has the advantage of not being attacked and worn by an abrasive substance. The slats can be made of plastic, for example polypropylene. Alternatively, the slats of the roller 2 can be cotton.

The material of the blades of the rinsing roller 3 is chosen so that it can be soaked with a rinsing liquid. The roller 3 can for example be a rotary microfiber brush. The material of the roller 3 may have a spongy character.

The device further comprises a displacement means 4 configured to drive the rollers 2 and 3 in rotation around their respective axes of revolution. The displacement means 4 is also configured to drive the rollers 2 and 3 in translation. Alternatively, the device may include means separate from the displacement means 4 for driving the rollers 2 and 3 in translation. Mechanical drive means for the rollers are well known to those skilled in the art and will not be detailed here.

The device further comprises a support, not shown in the figures, for holding the roller 2 in position relative to the roller 3 and allowing the joint movement of the two rollers.

The device also advantageously includes a recovery tank 6 advantageously located in the sealed housing 7. The tank 6 is arranged near the rollers 2 and 3 so as to recover the chemical attack residues generated by the passage of the roller 2, and any excess chemical attack solution and / or rinsing solution. In the present example, the recovery tank 6 is arranged against a face of the sealed housing 7 perpendicular to the contact face. parts 20 and 30 with a part, and covers all of said face. A space is provided between the aligned flat faces of the two rollers 2 and 3 and one face of the sealed housing 7, in which the tank 6 is arranged. The tank 6 is thus positioned at the outlet of the rollers 2 and 3.

The dimensions of the rollers 2 and 3 (and possibly of the sealed casing 7) can be chosen as a function of the parts which it is intended to treat. For localized treatment of turbine engine blade surfaces, the rollers 2 and 3 advantageously have a length of between 5 and 500 millimeters, preferably between 10 and 100 millimeters. The rollers are then suitable for treating surfaces with dimensions of between 1 mm ² and 100 mm ² , preferably between 5 mm ² and 15 mm ² . Preferably, the rollers 2 and 3 are of the same shape and the same dimensions. They are smaller than one dimension of the part to be treated.

There is shown in Figure 2 a schematic perspective view from above of the machine comprising the sealed housing 7 and the rollers 2 and 3, after treatment of the part 1. For clarity, the displacement means 4 is not shown in Figure 2; however, means 5 have been shown here for controlling a system 22 for feeding chemical attack solution, a system 32 for supplying rinsing liquid, and a system 62 for evacuating accumulated waste. in the recovery tank 6 - the elements 5, 22, 32 and 62 not being shown in Figures la and 1b for more readability.

The system 22 may include a tank of chemical attack solution, a pipe one end of which opens into the tank and the other end of which opens in the vicinity of the chemical attack roller 2, and a pump for supplying the attack solution chemical from the tank to the roller 2. The system 32 may comprise a tank for rinsing solution, a pipe one end of which opens into the tank and the other end of which opens in the vicinity of the roller 3 for rinsing, and a pump for bringing the solution for rinsing from the reservoir to the roller 2. The control means 5 may advantageously include a treatment unit configured for receive electronic instructions, and configured to control valves associated with pumps in systems 22 and 32.

'Advantageously, the system 32 also includes a second branch for supplying rinsing liquid to the roller 2. This latter configuration has the advantage of facilitating the simultaneous cleaning of the two rollers 2 and 3 after a treatment cycle. In addition, this configuration makes it possible to inject a well-chosen flow rate of rinsing liquid at the level of the roller 2 during the treatment, so as to unclog the roller 2. Too much fouling of the roller 2 caused by the chemical attack solution a to damage the surface layers of roller 2.

The waste evacuation system 62 can be connected to the recovery tank 6 by means of a pipe, one end of which opens into the tank 6. The system 62 can be provided with an air pump to allow the suction of the contents of tray 6, in order to empty the tray 6.

Surface treatment method by chemical attack

FIG. 3 shows the steps of a method 10 for treating the surface of a part of a turbomachine according to an embodiment of the invention.

The part includes one (or more) surface (s) to be treated. Preferably, it is a surface of a metal part, for example steel, nickel or titanium. Said surface may have been previously machined, for example milled and / or rectified. Indeed, these usual operations are likely to produce localized excess of metallic material (for example burrs) on the surface of the parts. In the case of turbine engine blades, the surface of the blades should be smoothed and the burrs removed so as to optimize the aerodynamic efficiency of the blade set. We can also try to polish the surfaces to be treated.

The method comprises a first step 100 of loading the rollers 2 and 3. In this example, the loading is carried out by partial or total impregnation of the chemical attack roller 2 with a chemical attack solution as defined above, and (simultaneously or deferred) of partial or total impregnation of the rinsing roller 3 with rinsing solution . It can be provided that only the radially external parts of the rollers 2 and 3 are impregnated, or alternatively, that all of the rollers are impregnated.

Then, during a step 200, the rollers 2 and 3 are positioned opposite the part to be treated. The external parts of the rollers 2 and 3 are positioned against the surface 1a without the rotation of the rollers being hindered. Advantageously, the rollers 2 and 3 can be positioned directly in the vicinity of the surface to be treated.

Advantageously, the lateral faces of the rollers 2 and 3 are aligned, as in Figures la and lb. There are then two roll alignment planes, each of these planes comprising a lateral face of the roller 2 and a lateral face of the roller 3.

Then, during a step 300, the rollers 2 and 3 move to successively apply the etching solution and the rinsing solution to the surface to be treated. In the present example, step 300 comprises a simultaneous movement of rotation and translation of the rollers 2 and 3. For example, a first sub-step 301 can be provided for the simultaneous rotation of the rollers 2 and 3 around their axes of respective revolution, followed by a second substep 302 for translational drive of the two rollers (during rotation) in a direction of movement X. The translational and rotational movements are communicated to the rollers 2 and 3 by the displacement means 4 as described above.

The direction of movement X of the rollers is chosen so that the rollers 2 and 3, impregnated respectively with etching solution and rinsing solution, pass through the surface to be treated during their movement. For effective surface treatment, roller 2 first crosses the surface, then roller 3, located behind roller 2, crosses the surface immediately after roller 2 of so as to rinse the surface. An advantage of this configuration is that any excess of etching solution, as well as the material removed from the surface to be treated by the etching, are immediately removed from the surface of the part, and advantageously brought to the recovery tank 6.

Advantageously, the roller 3 is located in the wake of the roller 2, to ensure that the rinsing solution is applied in areas of the surface to be treated which have just received the chemical attack solution. The trajectory of the rollers 2 and 3 during their displacement can be controlled by the displacement means 4, according to instructions received from a processing unit. The instructions may have been previously selected by a user.

Advantageously, the rollers are continuously supplied respectively with chemical attack solution and with rinsing solution, so as to remain impregnated during the simultaneous movement of rotation and translation.

Step 300 preferably has a duration which depends on the surface of the part to be treated. For example, step 300 can have a duration of 1 to 10 seconds per square millimeter of surface to be treated. Step 300 can have a duration of between 10 and 300 seconds, preferably between 20 and 60 seconds (at the end of this duration, the rollers 2 and 3 can be repositioned in the vicinity of another surface to be treated during of a new step 200, and put back into motion during a new step 300). Such a duration is particularly advantageous in the context of deburring or polishing an edge or a small surface of a part. In general, the duration of the treatment can be selected according to the size of the area to be treated. Conversely, with the treatments known from the prior art such as tribofinishing, the duration of the treatment cannot be reduced, even if it is not necessary to treat the entire part.

As an alternative to moving the rollers 2 and 3 in translation, the rollers 2 and 3 can be driven in rotation without being driven in translation during step 300, and the part can be brought into contact with rollers 2 and 3 at the surface to be treated and translated in a direction transverse to the rollers.

Finally, in the case where the chemical attack machine implementing the method 10 comprises a recovery tank 6, provision may be made in step 400 for emptying the tank 6.

FIG. 4 shows a height profile of a test piece surface representative of a turbomachine blade, deburred using the method 10. The height of the surface on a microscopic scale is indicated on l axis of ordinates, the height 0 corresponding to an average of the height of the surface of the part. The test piece is made of nickel base, made of Inconel 718 material. For this test, the duration of the chemical attack is close to 35 seconds.

Two separate test-tube zones were delimited along a direction corresponding to the direction of movement of the rollers 2 and 3 during step 300. The two test-tube zones were separated from each other by a strip of single-sided adhesive, glued to the surface of the test piece transversely to the direction of movement of the rollers. During the implementation of method 10, the rollers pass over only one of the two zones (part C on the right in FIG. 4), and stop at the level of the strip of adhesive (part B ). Thus, the other zone (part A) does not receive a chemical attack solution. Part A therefore plays the role of witness.

It is observed that the chemical attack treatment makes it possible to significantly reduce the roughness of the surface of the nickel-based test piece, and to improve the surface condition thereof. Indeed, the portion of curve corresponding to part C (treated area) has a roughness Ra of 0.20 micrometers, while the portion of curve corresponding to part A (untreated area) has a roughness Ra of 0.64 micrometers.

Furthermore, the amplitude between the maximum height point and the minimum height point along the measurement direction is much less for part C (approximately 1.5 micrometers) compared to part A (and approximately 4.5 micrometers).

Figures Sa and 5b are top views under a microscope of a surface of the nickel-based test piece, said surface corresponding to part C of Figure 4 (area treated using method 10). Figure 5a corresponds to the surface before treatment, and Figure 5b corresponds to the surface after treatment.

It is observed that, following the passage of the rollers 2 and 3 (Figure 5b), the variations in height are much less marked than before the passage of the rollers. The surface condition of the test piece is much more satisfactory.

The method of the invention therefore provides an effective solution for improving the surface condition of a part, in particular a metal part, and for reducing its roughness, without requiring a large quantity of abrasive product and / or solid medium, quick way.

Although a treatment method and device has been described comprising only two distributors, it will be noted that the machine can be adapted to include several series of distributors. This can in particular make it possible to treat several parts surfaces at the same time. Provision may be made for having several pairs comprising a distributor for chemical attack and a distributor for rinsing, in series, for carrying out several consecutive passages on the same surface to be treated.

Claims

1. Method for treating the surface of a part (1), for example a part of a turbomachine, the part comprising a surface (la) to be treated,

the method being characterized in that it comprises the following steps:

- loading (100) of a first distributor (2) with a chemical attack solution and of a second distributor (3) with a rinsing solution,

- positioning (200) of the first distributor (2) and the second distributor (3) opposite the surface to be treated,

displacement of the first distributor and of the second distributor along the surface to be treated, so that the surface to be treated successively receives the chemical attack solution and then the rinsing solution.

2. Method according to claim 1, in which the first distributor (2) and the second distributor (3) are positioned and moved relative to the surface to be treated so that the second distributor (3) is positioned in the wake of the first distributor (2) for applying the rinsing solution to the areas of the surface to be treated having just received the chemical attack solution.

3. Method according to one of claims 1 or 2, wherein the first distributor (2) and the second distributor (3) each comprise a roller, a brush or a brush, and wherein the step of positioning includes bringing the first distributor and the second distributor into contact with the surface to be treated of the part.

4. Treatment process according to claim 3, in which the first distributor (2) and the second distributor are continuously charged respectively with etching solution and with rinsing solution so as to remain impregnated during the application (300).

5. Treatment process according to one of claims 1 to 4, in which the etching solution is a solution with an acid pH of less than 5, or with a basic pH of more than 9.

6. Treatment method according to one of claims 1 to 5, wherein the displacement step is of a duration between 1 and 10 seconds per square millimeter of surface to be treated.

7. Device for the surface treatment of a part according to a method of one of claims 1 to 6, in particular for the surface treatment of a part of a turbomachine, said part comprising a surface to be treated (la) and the device comprising:

- a first distributor (2) configured to distribute a chemical attack solution,

- a second distributor (3) configured to distribute a rinsing solution,

- a support configured to hold the first distributor in position relative to the second distributor and allow their joint movement,

- displacement means (4) configured to allow simultaneous movement of the first distributor (2) and the second distributor (3) along the surface to be treated so that the surface to be treated first receives the etching solution chemical then the rinsing solution, and - a sealed housing (7) in which the first (2) and second (3) distributors are positioned and configured to ensure the seal between the surface to be treated (la) and areas of the part located outside the surface to be treated .

8. Surface treatment device according to claim 7, further comprising:

means (22) for supplying chemical attack solution at the level of the first distributor (2),

means (32) for supplying rinsing solution to the second distributor (3),

- Control means (5) for a flow of the chemical attack solution and a flow of the rinsing solution.

9. Treatment device according to one of claims 7 or 8, wherein the first distributor and the second distributor each comprise a roller, and the device further comprises a recovery tank (6) configured to recover an excess of solution d etching and an excess of rinsing solution at the outlet of the etching roller (2) and the rinsing roller (2).