EP0436421A1 - Method for the removal of a coating from parts by use of a high-pressure waterjet - Google Patents

Method for the removal of a coating from parts by use of a high-pressure waterjet Download PDF

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Publication number
EP0436421A1
EP0436421A1 EP19900403664 EP90403664A EP0436421A1 EP 0436421 A1 EP0436421 A1 EP 0436421A1 EP 19900403664 EP19900403664 EP 19900403664 EP 90403664 A EP90403664 A EP 90403664A EP 0436421 A1 EP0436421 A1 EP 0436421A1
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Prior art keywords
coating
treated
speed
removal
jet
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EP19900403664
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German (de)
French (fr)
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EP0436421B1 (en
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Odile Marie Suzanne Bondoux
Jacques Lesgourgues
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Sochata Ste
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Sochata Ste
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
    • B08B3/02—Cleaning by the force of jets or sprays

Definitions

  • the present invention relates to a process for removing coatings from mechanical parts, in particular during the repackaging of aeronautical parts, in particular intended for aeronautical engines, comprising the use of a jet of water under high pressure, with or without the addition of 'additives or particles, possibly abrasive.
  • the object of the invention is to provide a process for removing coatings from mechanical parts which meet the imposed quality criteria which are frequently severe for the acceptance of parts intended for aeronautical engines which constitute a particular application directly targeted by the invention. .
  • the method according to the invention by adapting means, some of which are already known for other uses, makes it possible to combine numerous technical and economic advantages without incurring the drawbacks encountered in the implementation of the prior methods used for removal of coatings on mechanical parts.
  • the installation 1 schematically represented in FIG. 1 and used for implementing the coating removal process on mechanical parts according to the invention comprises for example several work stations each comprising a workpiece support such as a table 2 or a fixed position 3 or any type of positioner suitable for the parts and the areas to be treated and associated displacement means carrying at least one projection head 4.
  • These displacement means 5 associated with the table 2 can for example allow crossed movements or they can be constituted by a robot 6.
  • Said work stations are connected by a set of pipes and valves, symbolized at 7, to a set of power supply 8 including in particular a system of pumping 9 and distributing 10 water under high pressure p.
  • Each workstation is completed by a device for recovering the fluid jet, which it also provides for amortization after its action on the part to be treated. This device consists for example of a layer up to 1 m thick consisting of a stack of pebbles leading to fine sand.
  • a control cabinet 11 completes the installation.
  • a part 12 is for example placed on said table 2 on which it is fixed by any known means.
  • the area of the part 12 to be treated is placed at a distance d, generally less than 200 mm from the outlet orifice of said projection head 4.
  • Said projection head 4 orientably mounted on the displacement means 5 comprises, as shown in FIG. 2 in detail, a nozzle 4a provided with a calibrating element of the water jet which is for example made of sapphire and has a passage opening chosen according to each particular application and which is, for example, 0.25 mm, 0.35 mm, 0.4 mm or 0.5 mm.
  • the spray head 4 also includes a high pressure water inlet 4b, a supply 4c of possible additional particles, a chamber 4d with a venturi effect and a nozzle 4e for guiding the jet.
  • the second step (b) of said method consists in projecting onto said zone of the part 12 to be treated a jet of water under high pressure by means of said head 4, the adapted displacements making it possible to cover the entirety of said zone to be treated.
  • the high water pressure is adjusted to a value p greater than 108 Pa.
  • the speed v of the displacements is set between 0.025 m / min and 7 m / min.
  • the value of the parameters noted above is determined so as to obtain the complete removal of the coating while preserving the absence of attack at the level of the part surface forming the substrate of said coating.
  • the maximum speed of 7 m / min indicated above can in particular be increased depending on the capacities of the means used and the adaptation of the other parameters to particular applications.
  • a minimum speed limit can be determined depending on the type of coating to be removed. Thus for a deposit of thick and aged tungsten carbide, this limit can go down to 0.025 m / min.
  • additives can be added to the fluid jet sprayed with pure water, under high pressure.
  • Polymers are thus used which modify the physical properties of water, in particular wetting or surface tension, which makes it possible to act on the characteristics of the jet obtained, its shape, its compactness, its propensity for divergence, the characteristics impact with the material, for example.
  • particles can be added to the projected fluid so as to modify the mechanical action of the jet on the material.
  • a high pressure water jet in accordance with the invention, makes it possible to use more tender projectiles, balls plastic, or on the contrary abrasive grains of garnet, to activate the surface for a new deposit, for example.
  • the characteristics of the sprayed fluid are determined following tests, in particular the nature, morphology and quantity of the particles added to the water under high pressure. The same projection head allows these operations to be carried out successively if necessary.
  • FIG. 3 shows diagrammatically an example of a projection head 4 equipped with a nozzle, of which FIG. 4 shows a particular example of embodiment of the section 4f for calibrating the jet.
  • FIG. 5 shows diagrammatically a solution in which the projection head 4 combines several nozzles, which makes it possible to increase the yield.
  • FIG. 6 schematically shows an application in which several projection heads 4 with a single nozzle are associated allowing overlapping jets.
  • the angle of incidence of the jet can also be adjusted either according to a particular relief of the part. either to improve the yield or to modify a degree of selective aggression on the coating.
  • the types of coatings removed include deposits obtained by spraying on the arc plasma or oxyacetylene flame and various deposits obtained electrolytically, chemically or electrochemically.
  • the removal can take place during touch-ups or recoveries on new parts during manufacture or during the repair of degraded parts in operation.
  • An important advantage of the water jet removal process according to the invention and which has just been described is to allow reconditioning of the treated surface for a new deposition without requiring an additional cycle of surface preparation before coating.
  • the method according to the invention makes it possible to eliminate an external layer 13 without altering the base layer 14 adhering to the substrate 15, as schematically represented in the figure. 7. This result is made possible by a judicious choice of parameters.
  • FIG. 8 a reduction in nuisance can be obtained, in particular noise by applying the method according to the invention in a configuration of submerged jet such as an exemplary embodiment is shown diagrammatically in FIG. 8.
  • the fluid jet 16 for the part 12 is immersed in a surrounding liquid mass 17.

Abstract

The method for the removal of a coating from mechanical parts consists in treating the area concerned with a water jet (16) at a high pressure p greater than 10<8> Pa by means of a nozzle (4a) connected to a feed system (9, 10) and carried on a head (4) connected to a movement system (6), the value of the parameters being determined as a function of the condition and the type of the coating whilst observing the quality criteria for the results as regards the desired surface finish and complete removal of at least one layer of coating (13), the speed v of the movements being chosen in order in particular to achieve a maximum speed of coverage, or area treated per unit of time. <IMAGE>

Description

La présente invention concerne un procédé d'enlèvement de revêtements sur pièces mécaniques, notamment lors du reconditionnement de pièces aéronautiques, en particulier destinées aux moteurs aéronautiques, comportant l'utilisation d'un jet d'eau sous haute pression, avec ou sans adjonction d'additifs ou de particules, éventuellement abrasives.The present invention relates to a process for removing coatings from mechanical parts, in particular during the repackaging of aeronautical parts, in particular intended for aeronautical engines, comprising the use of a jet of water under high pressure, with or without the addition of 'additives or particles, possibly abrasive.

Le choix du matériau imposé pour les pièces mécaniques, notamment destinées aux moteurs aéronautiques dans des conditions sévères d'utilisation en niveau de contraintes ou dues à l'environnement, amène souvent à réaliser des revêtements adhérents sur ces pièces ou fréquemment sur certaines zones délimitées afin de remplir certaines fonctions particulières. On obtient ainsi des protections contre l'usure ou l'érosion au moyen de zones durcies ou une protection contre diverses corrosions ou encore des barrières thermiques ou des revêtements d'étanchéité par matériau abradable. Ces divers revêtements selon les applications, leur nature ou celle du substrat peuvent être obtenus par dépôts par voie électrolytique ou électrochimique ou par projection à la flamme oxyacétylénique ou au plasma d'arc notamment ou encore par traitement thermochimique.The choice of material imposed for mechanical parts, in particular intended for aeronautical engines under severe conditions of use in terms of constraints or due to the environment, often leads to producing adherent coatings on these parts or frequently on certain demarcated areas in order to to perform certain specific functions. Protections against wear or erosion are thus obtained by means of hardened zones or protection against various corrosions or alternatively thermal barriers or sealing coatings by abradable material. These various coatings depending on the applications, their nature or that of the substrate can be obtained by electrolytic or electrochemical deposition or by spraying with an oxyacetylene flame or with arc plasma in particular or also by thermochemical treatment.

Les retouches des pièces en cours de fabrication dans le cas de non-conformité ou leur reprise en vue du reconditionnement lors des réparations après fonctionnement imposent habituellement un enlèvement des revêtements. Les procédés connus d'enlèvement font appel notamment soit à des bains chimiques pour dissolution, soit à des moyens classiques d'usinage, soit à des projections d'abrasifs. Chacune de ces solutions connaît ses limitations propres et occasionne en outre des inconvénients notables, notamment des temps opératoires élevés pour la dissolution chimique et la projection d'abrasif et une attaque du métal de base lors d'un usinage ou d'une projection d'abrasif. Une préparation spécifique de surface est en outre imposée dans tous les cas avant d'effectuer un nouveau dépôt. On connaît par ailleurs divers exemples de mise en oeuvre dans l'utilisation d'un jet d'eau sous haute pression, notamment pour la découpe de divers matériaux et des machines sont proposées par divers constructeurs, adaptées pour ces applications connues.Touch-ups of parts during manufacture in the event of non-compliance or their resumption for reconditioning during repairs after operation usually require removal of the coatings. The known methods of removal use in particular either chemical baths for dissolution, or conventional means of machining, or projections of abrasives. Each of these solutions knows its own limitations and also causes significant drawbacks, in particular high operating times for chemical dissolution and projection of abrasive and attack of the base metal during machining or projection of abrasive. A specific surface preparation is also required in all cases before making a new deposit. We also know various examples of implementation in the use of a high pressure water jet, in particular for cutting various materials and machines are proposed by various manufacturers, adapted for these known applications.

Le but de l'invention est de procurer un procédé d'enlèvement de revêtements sur pièces mécaniques répondant aux critères imposés de qualité qui sont fréquemment sévères pour l'acceptation de pièces destinées aux moteurs aéronautiques qui constituent une application particulière directement visée par l'invention. Le procédé selon l'invention par l'adaptation de moyens dont certains sont déjà connus pour d'autres utilisations permet de combiner de nombreux avantages tant techniques qu'économiques sans encourir les inconvénients rencontrés dans la mise en oeuvre des procédés antérieurs utilisés pour l'enlèvement de revêtements sur pièces mécaniques.The object of the invention is to provide a process for removing coatings from mechanical parts which meet the imposed quality criteria which are frequently severe for the acceptance of parts intended for aeronautical engines which constitute a particular application directly targeted by the invention. . The method according to the invention by adapting means, some of which are already known for other uses, makes it possible to combine numerous technical and economic advantages without incurring the drawbacks encountered in the implementation of the prior methods used for removal of coatings on mechanical parts.

Le procédé d'enlèvement de revêtements conforme à l'invention et répondant à ces conditions est caractérisé en ce qu'il comporte les étapes suivantes:

  • (a) mise en place de la pièce à traiter sur la machine et mise en place d'une tête de projection, à une distance d de la surface à traiter telle que d > 1 mm;
  • (b) traitement de la pièce par projection d'un jet d'eau dirigé par la buse de la machine sur la zone de la pièce à traiter, ladite buse étant alimentée sous une haute pression p telle que p > 10⁸ Pa et un déplacement relatif entre buse de projection et surface à traiter étant imposé à une vitesse v telle que 0,025 m/mn < v < V max, la valeur des paramètres à utiliser étant déterminée pour chaque application particulière en fonction de la nature du revêtement à enlever et notamment en fonction de son état de vieillissement et les critères de qualité des résultats à obtenir étant l'enlèvement recherché d'au moins une couche de revêtement et un état de surface déterminé au niveau de la surface de pièce découverte, la vitesse v étant notamment choisie dans la limite V max possible par les moyens utilisés de manière à obtenir une vitesse surfacique ou surface traitée par unité de temps maximale
The process for removing coatings in accordance with the invention and meeting these conditions is characterized in that it comprises the following stages:
  • (a) placing the part to be treated on the machine and placing a projection head, at a distance d from the surface to be treated such that d> 1 mm;
  • (b) treatment of the part by spraying a jet of water directed by the nozzle of the machine onto the zone of the part to be treated, said nozzle being supplied under a high pressure p such that p> 10⁸ Pa and a displacement relative between the spray nozzle and the surface to be treated being imposed at a speed v such as 0.025 m / min <v <V max, the value of the parameters to be used being determined for each particular application as a function of the nature of the coating to be removed and in particular according to its state of aging and the quality criteria of the results to be obtained being the desired removal of at least one coating layer and a surface condition determined at the level of the surface of the part discovered, the speed v being notably chosen within the limit V max possible by the means used so as to obtain a surface speed or surface treated per maximum time unit

D'autres caractéristiques et avantages de l'invention seront mieux compris à la lecture de la description qui va suivre d'un mode de réalisation de l'invention, en référence aux dessins annexés sur lesquels:

  • la figure 1 schématise les moyens de mise en oeuvre d'une opération de traitement d'une pièce selon le procédé d'enlèvement de revêtement conforme à l'invention;
  • la figure 2 montre un détail d'une tête de projection entrant dans l'installation représentée sur la figure 1;
  • la figure 3 montre un schéma de fonctionnement de ladite tête de projection représentée sur la figure 2;
  • la figure 4 montre une vue de la tête de projection représentée sur la figure 3 selon une direction F montrant une section de buse de projection;
  • la figure 5 montre, selon une vue analogue à celle de la figure 3, un schéma de fonctionnement d'une tête de projection à jets multiples;
  • la figure 6 montre, selon une vue analogue à celles des figures 3 et 5, un schéma de fonctionnement montrant l'association de plusieurs têtes de projection;
  • la figure 7 montre, selon une vue analogue à celles des figures 3, 5 et 6, un schéma de fonctionnement montrant un exemple de mise en oeuvre pour l'enlèvement d'une couche superficielle externe de revêtement;
  • la figure 8 montre, selon une vue analogue à celles des figures 3 et 5 à 7, un schéma de fonctionnement dans le cas d'un jet immergé.
Other characteristics and advantages of the invention will be better understood on reading the description which follows of an embodiment of the invention, with reference to the appended drawings in which:
  • Figure 1 shows schematically the means of implementing a part processing operation according to the coating removal process according to the invention;
  • Figure 2 shows a detail of a projection head entering the installation shown in Figure 1;
  • Figure 3 shows an operating diagram of said projection head shown in Figure 2;
  • Figure 4 shows a view of the projection head shown in Figure 3 in a direction F showing a projection nozzle section;
  • Figure 5 shows, in a view similar to that of Figure 3, an operating diagram of a projection head with multiple jets;
  • Figure 6 shows, in a view similar to those of Figures 3 and 5, an operating diagram showing the association of several projection heads;
  • Figure 7 shows, in a view similar to those of Figures 3, 5 and 6, an operating diagram showing an exemplary implementation for the removal of an outer surface coating layer;
  • Figure 8 shows, in a view similar to those of Figures 3 and 5 to 7, a working diagram in the case of a submerged jet.

L'installation 1 schématiquement représentée sur la figure 1 et utilisée pour la mise en oeuvre du procédé d'enlèvement de revêtement sur pièces mécaniques conforme à l'invention comporte par exemple plusieurs postes de travail comprenant chacun un support de pièce tel qu'une table 2 ou un poste fixe 3 ou tout type de positionneur adapté aux pièces et aux zones à traiter et des moyens de déplacement associés portant au moins une tête 4 de projection. Ces moyens de déplacement 5 associés à la table 2 peuvent par exemple permettre des déplacements croisés ou ils peuvent être constitués par un robot 6. Lesdits postes de travail sont reliés par un ensemble de canalisations et vannes, symbolisées en 7, à un ensemble d'alimentation 8 comportant notamment un système de pomperie 9 et de distribution 10 de l'eau sous une haute pression p. Chaque poste de travail est complété par un dispositif de récupération du jet fluide dont il assure également l'amortissement après son action sur la pièce à traiter. Ce dispositif est par exemple constitué d'une couche jusqu'à 1 m d'épaisseur constituée d'un empilement de galets aboutissant à du sable fin. Une armoire de commande 11 complète l'installation.The installation 1 schematically represented in FIG. 1 and used for implementing the coating removal process on mechanical parts according to the invention comprises for example several work stations each comprising a workpiece support such as a table 2 or a fixed position 3 or any type of positioner suitable for the parts and the areas to be treated and associated displacement means carrying at least one projection head 4. These displacement means 5 associated with the table 2 can for example allow crossed movements or they can be constituted by a robot 6. Said work stations are connected by a set of pipes and valves, symbolized at 7, to a set of power supply 8 including in particular a system of pumping 9 and distributing 10 water under high pressure p. Each workstation is completed by a device for recovering the fluid jet, which it also provides for amortization after its action on the part to be treated. This device consists for example of a layer up to 1 m thick consisting of a stack of pebbles leading to fine sand. A control cabinet 11 completes the installation.

Lors de la première étape (a) dudit procédé, une pièce 12 est par exemple placée sur ladite table 2 sur laquelle elle est fixée par tout moyen connu. La zone de la pièce 12 à traiter est placée à une distance d, généralement inférieure à 200 mm de l'orifice de sortie de ladite tête 4 de projection.During the first step (a) of said method, a part 12 is for example placed on said table 2 on which it is fixed by any known means. The area of the part 12 to be treated is placed at a distance d, generally less than 200 mm from the outlet orifice of said projection head 4.

Ladite tête 4 de projection montée de manière orientable sur les moyens de déplacement 5 comporte, comme indiqué sur la figure 2 de détail, une buse 4a munie d'un élément de calibrage du jet d'eau qui est par exemple en saphir et présente une ouverture de passage choisie en fonction de chaque application particulière et qui est, par exemple, de 0,25 mm, 0,35 mm, 0,4 mm ou 0,5 mm. La tête 4 de projection comporte également une arrivée 4b d'eau sous haute pression, une alimentation 4c en particules additionnelles éventuelles, une chambre 4d à effet venturi et une buse de guidage 4e du jet.Said projection head 4 orientably mounted on the displacement means 5 comprises, as shown in FIG. 2 in detail, a nozzle 4a provided with a calibrating element of the water jet which is for example made of sapphire and has a passage opening chosen according to each particular application and which is, for example, 0.25 mm, 0.35 mm, 0.4 mm or 0.5 mm. The spray head 4 also includes a high pressure water inlet 4b, a supply 4c of possible additional particles, a chamber 4d with a venturi effect and a nozzle 4e for guiding the jet.

La deuxième étape (b) dudit procédé consiste à projeter sur ladite zone de la pièce 12 à traiter un jet d'eau sous haute pression au moyen de ladite tête 4, les déplacements adaptés permettant de couvrir l'intégralité de ladite zone à traiter. La haute pression d'eau est réglée à une valeur p supérieure à 10⁸ Pa. La vitesse v des déplacements est réglée entre 0,025 m/mn et 7 m/mn. En fonction de la nature des revêtements à enlever et notamment de leur état de vieillissement, la valeur des paramètres notés ci-dessus (pression p du jet d'eau, distance d entre sortie de buse et pièce, vitesse v des déplacements, caractéristiques de la busede projection) est déterminée de manière à obtenir l'enlèvementcomplet du revêtement tout en préservant l'absence d'attaque au niveau de la surface de pièce formant le substrat dudit revêtement. La vitesse maximale de 7 m/mn indiquée ci-dessus peut notamment être augmentée en fonction des capacités des moyens utilisés et de l'adaptation des autres paramètres aux applications particulières.The second step (b) of said method consists in projecting onto said zone of the part 12 to be treated a jet of water under high pressure by means of said head 4, the adapted displacements making it possible to cover the entirety of said zone to be treated. The high water pressure is adjusted to a value p greater than 10⁸ Pa. The speed v of the displacements is set between 0.025 m / min and 7 m / min. Depending on the nature of the coatings to be removed and in particular their aging state, the value of the parameters noted above (pressure p of the water jet, distance d between nozzle outlet and part, speed v of movements, characteristics of the projection nozzle) is determined so as to obtain the complete removal of the coating while preserving the absence of attack at the level of the part surface forming the substrate of said coating. The maximum speed of 7 m / min indicated above can in particular be increased depending on the capacities of the means used and the adaptation of the other parameters to particular applications.

Notamment, de bons résultats ont été obtenus en réglant la pression p d'alimenttion vers 3.10⁸ Pa et des valeurs de pression jusqu'à 4,2.10⁸ Pa ont pu être testées. Le choix de la vitesse v des déplacements conditionne notamment le rendement et en conséquence la rentabilité du procédé. En fait le rendement est défini par la vitesse surfacique ou surface traitée par unité de temps, obtenue en fonction de ladite vitesse v de déplacement et de la surface de pièce balayée à chaque passe. Les exemples d'essais ci-après montrent le mode de détermination de ces paramètres.In particular, good results have been obtained by adjusting the supply pressure p towards 3.10⁸ Pa and pressure values up to 4.2.10⁸ Pa have been tested. The choice of the speed v of the displacements notably conditions the yield and consequently the profitability of the process. In fact, the yield is defined by the surface speed or surface treated per unit of time, obtained as a function of said speed of movement v and of the part surface swept at each pass. The following test examples show the method of determining these parameters.

EXEMPLE 1EXAMPLE 1

Lors de l'élimination d'un revêtement de carbure de tungstène d'épaisseur 0,2 mm sur un substrat en superalliage résistant à haute température, sans altération du substrat, en utilisant une pression p de 3.10⁸ Pa, une distance d de 70 mm, un diamètre de buse de 0,4 mm, le fluide projeté étant de l'eau pure, les résultats suivants ont été observés:

v en m/mn:
3; 4; 5; 6; 7
largeur décapée 1:
0,22; 0,225; 0,19; 0,17; 0,16
par passe en cm
vitesse surfacique:
66; 90; 95; 102; 112
vs en cm2/minute
When removing a coating of tungsten carbide 0.2 mm thick on a superalloy substrate resistant to high temperature, without alteration of the substrate, using a pressure p of 3.10⁸ Pa, a distance d of 70 mm, a nozzle diameter of 0.4 mm, the sprayed fluid being pure water, the following results have been observed:
v in m / min:
3; 4; 5; 6; 7
pickled width 1:
0.22; 0.225; 0.19; 0.17; 0.16
per pass in cm
surface speed:
66; 90; 95; 102; 112
v s in cm2 / minute

La meilleure valeur est obtenue pour une vitesse de déplacement de 7 m/mn qui est la vitesse maximale obtenue dans les essais réalisés.The best value is obtained for a displacement speed of 7 m / min which is the maximum speed obtained in the tests carried out.

EXEMPLE 2EXAMPLE 2

Les quatres paramètres de l'exemple 1 étant conservés, lors de l'enlèvement d'un dépôt Ni-Cr-Al d'épaisseur 0,1 mm sur le même substrat, les résultats suivant ont été observés:

v en m/mn:
3; 4; 5; 6; 7
1 en cm:
0,36; 0,28; 0,29; 0,3; 0,22
vs en cm2/mn:
108; 112; 145; 180; 154
The four parameters of Example 1 being retained, when removing a 0.1 mm thick Ni-Cr-Al deposit on the same substrate, the following results were observed:
v in m / min:
3; 4; 5; 6; 7
1 in cm:
0.36; 0.28; 0.29; 0.3; 0.22
v s in cm2 / min:
108; 112; 145; 180; 154

Dans cette application, le meilleur compromis donnant le meilleur rendement est obtenu pour une valeur optimale de vitesse de déplacement de 6 m/mn.In this application, the best compromise giving the best yield is obtained for an optimal value of displacement speed of 6 m / min.

EXEMPLE 3EXAMPLE 3

Lors des essais d'enlèvement d'un dépôt Ni-Cr-Al d'épaisseur 0,25 mm présentant un état de vieillissement correspondant à un fonctionnement, le substrat étant du type précédent, on utilise une pression p de 3.10⁸ pa, une distance d de 65 mm et un diamètre de buse de 0,25 mm, le fluide projeté étant de l'eau pure et on observe les résultats suivants:

v en m/mn:
0,25; 0,32; 0,50
1 en cm:
0,057; 0,048; 0
vs en cm2/mn:
1,43; 1,54; 0
During the removal tests of a 0.25 mm thick Ni-Cr-Al deposit having an aging state corresponding to operation, the substrate being of the above type, a pressure p of 3.10⁸ pa is used, a distance d of 65 mm and a nozzle diameter of 0.25 mm, the sprayed fluid being pure water and the following results are observed:
v in m / min:
0.25; 0.32; 0.50
1 in cm:
0.057; 0.048; 0
v s in cm2 / min:
1.43; 1.54; 0

Une vitesse optimale de déplacement est ainsi obtenue pour v: 0,32 m/mn. De même une vitesse limite minimale peut être déterminée en fonction du type de revêtement à enlever. Ainsi pour un dépôt de carbure de tungstène épais et vieilli, cette limite peut descendre jusqu'à 0,025 m/mn.An optimal speed of movement is thus obtained for v: 0.32 m / min. Similarly, a minimum speed limit can be determined depending on the type of coating to be removed. Thus for a deposit of thick and aged tungsten carbide, this limit can go down to 0.025 m / min.

En fonction des applications particulières, divers additifs peuvent être ajoutés au jet fluide projeté à base d'eau pure, sous haute pression. On utilise ainsi des polymères qui modifient les propriétés physiques de l'eau, notamment de mouillage ou de tensions superficielles, ce qui permet d'agir sur les caractéristiques du jet obtenu, sa forme, sa compacité, sa propension à la divergence, les caractéristiques du choc avec la matière, par exemple.Depending on the particular application, various additives can be added to the fluid jet sprayed with pure water, under high pressure. Polymers are thus used which modify the physical properties of water, in particular wetting or surface tension, which makes it possible to act on the characteristics of the jet obtained, its shape, its compactness, its propensity for divergence, the characteristics impact with the material, for example.

Dans certaines applications également, notamment lorsqu'un effet de mise sous contrainte superficielle des surfaces traitées du substrat est recherché, ou quand par exemple l'enlèvement du revêtement est combiné avec un reconditionnement de la surface traitée en vue d'un nouveau dépôt, des particules peuvent être ajoutées au fluide projeté de manière à modifier l'action mécanique du jet sur la matière. Au lieu des techniques habituelles de mise sous contrainte superficielles par grenaillage à la bille d'acier, de verre ou de céramique, l'utilisation d'un jet d'eau sous haute pression, conforme à l'invention, permet d'utiliser des projectiles plus tendres, billes en plastique, ou au contraire des grains abrasifs de grenat, pour activer la surface en vue d'un nouveau dépôt, par exemple. En fonction de chaque application et des résultats recherchés, les caractéristiques du fluide projeté sont déterminées à la suite d'essais, notamment la nature, la morphologie et la quantité des particules ajoutées à l'eau sous haute pression. La même tête de projection permet de réaliser successivement ces opérations si nécessaire.In certain applications also, in particular when a surface stressing effect on the treated surfaces of the substrate is sought, or when, for example, the removal of the coating is combined with reconditioning of the treated surface with a view to re-deposition, particles can be added to the projected fluid so as to modify the mechanical action of the jet on the material. Instead of the usual techniques of surface stress by shot blasting with a steel, glass or ceramic ball, the use of a high pressure water jet, in accordance with the invention, makes it possible to use more tender projectiles, balls plastic, or on the contrary abrasive grains of garnet, to activate the surface for a new deposit, for example. Depending on each application and the results sought, the characteristics of the sprayed fluid are determined following tests, in particular the nature, morphology and quantity of the particles added to the water under high pressure. The same projection head allows these operations to be carried out successively if necessary.

On notera que lors du traitement de matériaux sensibles (titane ou alliages légers par exemple), les risques de blessure de surface, de contaminations, d'incrustations sont éliminés lorsqu'un effet de mise sous contrainte superficielle est obtenu par traitement au jet sous haute pression, soit en utilisant uniquement de l'eau pure, soit en limitant les risques grâce au choix des particules ajoutées à l'eau.It will be noted that during the treatment of sensitive materials (titanium or light alloys for example), the risks of surface injury, contamination, encrustations are eliminated when a surface stressing effect is obtained by treatment with a high-pressure jet. pressure, either by using only pure water, or by limiting the risks thanks to the choice of particles added to the water.

La mise au point des paramètres précédemment notés (pression p, distance d, vitesse v, notamment) tient compte également pour chaque application de la morphologie du jet fluide, notamment en fonction du choix de la forme de la buse. La figure 3 schématise un exemple de tête 4 de projection équipée d'une buse dont la figure 4 montre un exemple particulier de réalisation de la section 4f de calibrage du jet. La figure 5 schématise une solution dans laquelle la tête 4 de projection associe plusieurs buses, ce qui permet d'augmenter le rendement. La figure 6 montre schématiquement une application dans laquelle plusieurs têtes 4 de projection à buse simple sont associées permettant des jets chevauchants. En outre, l'angle d'incidence du jet peut également être réglé soit en fonction d'un relief particulier de pièce soit pour améliorer le rendement ou modifier un degré d'agression sélective sur le revêtement.The development of the previously noted parameters (pressure p, distance d, speed v, in particular) also takes into account for each application the morphology of the fluid jet, in particular as a function of the choice of the shape of the nozzle. FIG. 3 shows diagrammatically an example of a projection head 4 equipped with a nozzle, of which FIG. 4 shows a particular example of embodiment of the section 4f for calibrating the jet. FIG. 5 shows diagrammatically a solution in which the projection head 4 combines several nozzles, which makes it possible to increase the yield. FIG. 6 schematically shows an application in which several projection heads 4 with a single nozzle are associated allowing overlapping jets. In addition, the angle of incidence of the jet can also be adjusted either according to a particular relief of the part. either to improve the yield or to modify a degree of selective aggression on the coating.

Les types de revêtements enlevés, notamment sur des pièces destinées aux moteurs aéronautiques et sur des substrats en aciers à haute résistance ou en superalliages, notamment à base de nickel ou à base de cobalt ou des alliages de titane, comprennent des dépôts obtenus par projection au plasma d'arc ou à la flamme oxyacétylénique et divers dépôts obtenus par voie électrolytique, chimique ou électrochimique.The types of coatings removed, in particular on parts intended for aeronautical engines and on substrates of high-strength steels or superalloys, in particular based on nickel or based on cobalt or titanium alloys, include deposits obtained by spraying on the arc plasma or oxyacetylene flame and various deposits obtained electrolytically, chemically or electrochemically.

L'enlèvement peut intervenir lors de retouches ou récupérations sur pièces neuves en cours de fabrication ou lors de la réparation de pièces dégradées en fonctionnement.The removal can take place during touch-ups or recoveries on new parts during manufacture or during the repair of degraded parts in operation.

Un avantage important du procédé d'enlèvement par jet d'eau conforme à l'invention et qui vient d'être décrit est de permettre un reconditionnement de la surface traitée en vue d'un nouveau dépôt sans nécessiter un cycle supplémentaire de préparation de surface avant revêtement.An important advantage of the water jet removal process according to the invention and which has just been described is to allow reconditioning of the treated surface for a new deposition without requiring an additional cycle of surface preparation before coating.

Dans certaines applications également, notamment dans le cas de retouches locales sur des dépôts multicouches, le procédé conforme à l'invention permet d'éliminer une couche externe 13 sans altérer la couche de base 14 adhérente au substrat 15, comme schématiquement représenté sur la figure 7. Ce résultat est rendu possible grâce à un choix judicieux des paramètres.In certain applications also, in particular in the case of local retouching on multilayer deposits, the method according to the invention makes it possible to eliminate an external layer 13 without altering the base layer 14 adhering to the substrate 15, as schematically represented in the figure. 7. This result is made possible by a judicious choice of parameters.

EXEMPLE 4EXAMPLE 4

Un exemple supplémentaire illustre une détermination des paramètres dans une application concernant l'élimination d'un revêtement de zirconate de magnésium sur une sous-couche Ni-Cr-Al-Y d'une épaisseur totale de 0,35 mm, une légère attaque de l'ordre de 0,015 mm du substrat en superalliage à haute résistance étant recherchée en vue d'un reconditionnement. Les résultats suivants ont été obtenus, le fluide projeté étant l'eau pure avec le jet sous incidence normale;

  • essai 1 avec p = 3,3.10⁸ Pa, d = 200 mm, buse = 0,35 mm;
    v = 3 m/mn; 1 = 0,5 cm; et vs = 150 cm2/mn
  • essai 2 avec p = 3.10⁸ Pa, d = 70 mm, buse = 0,5 mm;
    v = 3 m/mn; 1 = 0,46 cm et vs= 138 cm2/mn
  • essai 3 avec p = 3.10⁸ Pa, d = 70 mm, buse = 0,5 mm;
    v = 7 m/mn; 1 = 0,45 cm et vs = 315 cm2/mn
An additional example illustrates a determination of the parameters in an application relating to the elimination of a coating of magnesium zirconate on a Ni-Cr-Al-Y undercoat with a total thickness of 0.35 mm, a slight attack of the order of 0.015 mm of the high-resistance superalloy substrate being sought for reconditioning. The following results were obtained, the projected fluid being pure water with the jet at normal incidence;
  • test 1 with p = 3.3.10⁸ Pa, d = 200 mm, nozzle = 0.35 mm;
    v = 3 m / min; 1 = 0.5 cm; and v s = 150 cm2 / min
  • test 2 with p = 3.10⁸ Pa, d = 70 mm, nozzle = 0.5 mm;
    v = 3 m / min; 1 = 0.46 cm and v s = 138 cm2 / min
  • test 3 with p = 3.10⁸ Pa, d = 70 mm, nozzle = 0.5 mm;
    v = 7 m / min; 1 = 0.45 cm and v s = 315 cm2 / min

Par ailleurs, une réduction des nuisances peut être obtenue, notamment le bruit en appliquant le procédé conforme à l'invention dans une configuration de jet immergé tel qu'un exemple de réalisation est schématisé sur la figure 8. Le jet fluide 16 de traitement de la pièce 12 est immergé dans une masse liquide 17 environnante.Furthermore, a reduction in nuisance can be obtained, in particular noise by applying the method according to the invention in a configuration of submerged jet such as an exemplary embodiment is shown diagrammatically in FIG. 8. The fluid jet 16 for the part 12 is immersed in a surrounding liquid mass 17.

Claims (9)

Procédé d'enlèvement de revêtements sur pièces mécaniques, notamment lors du reconditionnement de pièces de moteurs aéronautiques, caractérisé en ce qu'il comporte les étapes suivantes: (a) ― mise en place de la pièce à traiter sur la machine et mise en place d'au moins une tête (4) de projection munie au moins d'une buse (4a), à une distance d de la surface à traiter telle que d > 1 mm; (b) ― traitement de la pièce par projection d'un jet d'eau dirigé par ladite buse de la machine sur la zone de pièce à traiter, ladite buse étant alimentée sous une haute pression p telle que p > 10⁸ Pa et un déplacement relatif entre buse de projection et surface à traiter étant imposé à une vitesse v telle que 0,025 m/mn < v < V max, la valeur des paramètres à utiliser étant déterminée en fonction de la nature du revêtement à enlever et notamment en fonction de son état de vieillissement et les critères de qualité des résultats à obtenir étant l'enlèvement recherché d'au moins une couche de revêtement et un état de surface déterminé au niveau de la surface de pièce découverte, la vitesse v étant notamment choisie dans la limite V max possible par les moyens utilisés de manière à obtenir une vitesse surfacique ou surface traitée par unité de temps maximale. Process for removing coatings from mechanical parts, in particular when reconditioning parts of aeronautical engines, characterized in that it comprises the following steps: (a) - placing the part to be treated on the machine and placing at least one projection head (4) provided with at least one nozzle (4a), at a distance d from the surface to be treated such that d> 1 mm; (b) - treatment of the part by projection of a water jet directed by said nozzle of the machine on the part area to be treated, said nozzle being supplied under a high pressure p such that p> 10⁸ Pa and a displacement relative between the spray nozzle and the surface to be treated being imposed at a speed v such as 0.025 m / min <v <V max, the value of the parameters to be used being determined as a function of the nature of the coating to be removed and in particular as a function of its state of aging and the quality criteria of the results to be obtained being the desired removal of at least one coating layer and a surface condition determined at the level of the surface of the part discovered, the speed v being notably chosen within the limit V max possible by the means used so as to obtain a surface speed or surface treated per maximum time unit. Procédé d'enlèvement de revêtements selon la revendication 1 dans lequel les valeurs de paramètres d'opération, distance d, pression p et vitesse v sont déterminées de manière à obtenir un enlèvement complet du revêtement et une absence d'attaque au niveau de la surface de la pièce formant le substrat.Method for removing coatings according to claim 1, in which the values of operating parameters, distance d, pressure p and speed v are determined so as to obtain complete removal of the coating and no attack on the surface. of the part forming the substrate. Procédé d'enlèvement de revêtements selon la revendication 2 dans lequel un effet de mise sous contrainte superficielle des surfaces de pièce traitées de manière à ce que ledit procédé constitue une opération de préparation de surface en vue d'un nouveau dépôt.A method of removing coatings according to claim 2, in which a surface stressing effect on the treated work surfaces so that said method constitutes a surface preparation operation for re-deposition. Procédé d'enlèvement de revêtement selon l'une des revendications 2 ou 3 dans lequel ledit procédé constitue une opération de préparation de surface en vue d'un nouveau dépôt.Coating removal method according to one of claims 2 or 3 wherein said method constitutes a surface preparation operation for a new deposition. Procédé d'enlèvement de revêtements selon la revendication 1 dans lequel les valeurs de paramètres d'opération, distance d, pression p et vitesse v sont déterminées de manière à obtenir l'enlèvement d'une couche superficielle (13) du revêtement sans altérer une sous-couche (14) de base adhérente au substrat (15).Method for removing coatings according to Claim 1, in which the values of operating parameters, distance d, pressure p and speed v are determined so as to obtain the removal of a surface layer (13) from the coating without altering a base sublayer (14) adhering to the substrate (15). Procédé d'enlèvement de revêtements selon l'une quelconque des revendications 1 à 5 dans lequel ledit jet d'eau projeté sous haute pression comporte des additifs.Method for removing coatings according to any one of claims 1 to 5, in which said jet of water sprayed under high pressure comprises additives. Procédé d'enlèvement de revêtements selon la revendication 6 dans lequel des particules à caractère abrasif sont mélangés audit jet d'eau projeté sous haute pression.A method of removing coatings according to claim 6 in which abrasive particles are mixed with said jet of water sprayed under high pressure. Procédé d'enlèvement de revêtements selon l'une quelconque des revendications 1 à 7 dans lequel une tête (4) de projection de jets d'eau sous haute pression à plusieurs buses (4a) est utilisée.Method for removing coatings according to any one of Claims 1 to 7, in which a head (4) for spraying jets of water under high pressure with several nozzles (4a) is used. Procédé d'enlèvement de revêtements selon l'une quelconque des revendications 1 à 8 dans lequel un paramètre de réglage complémentaire constitué par l'angle d'incidence du jet sur la surface à traiter est utilisé.Method for removing coatings according to any one of Claims 1 to 8, in which an additional adjustment parameter constituted by the angle of incidence of the jet on the surface to be treated is used.
EP19900403664 1989-12-20 1990-12-19 Method for the removal of a coating from parts by use of a high-pressure waterjet Expired - Lifetime EP0436421B1 (en)

Applications Claiming Priority (2)

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FR8916871A FR2655887B1 (en) 1989-12-20 1989-12-20 PROCESS FOR REMOVING A COATING ON PARTS BY SPRAYING A JET OF WATER AT HIGH VOLTAGE.
FR8916871 1989-12-20

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EP0436421A1 true EP0436421A1 (en) 1991-07-10
EP0436421B1 EP0436421B1 (en) 1994-05-04

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WO1999019087A1 (en) * 1997-10-10 1999-04-22 Norsk Hydro Asa Process for removing a plastic coating from metal products
WO2000029187A1 (en) * 1998-11-12 2000-05-25 Manfred Detterbeck Method and device for cleaning plastic components

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DE19549628B4 (en) * 1995-05-26 2006-08-17 Ryoden Semiconductor System Engineering Corp., Itami Washing appts. for cleaning of semiconductor substrate surface - has jet nozzle with mixer to mix fluid and gas before guiding droplets toward substrate surface
EP0764500B1 (en) * 1995-09-25 2001-08-22 ECO-SNOW SYSTEMS, Inc. Polishing system and method for soft metal surfaces using CO2 snow
DE10255213B4 (en) * 2002-11-27 2006-01-26 Daimlerchrysler Ag Process for the pretreatment of surfaces for thermally sprayed coatings
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CA2032218A1 (en) 1991-06-21
DE69008695D1 (en) 1994-06-09
FR2655887A1 (en) 1991-06-21
FR2655887B1 (en) 1992-03-06
EP0436421B1 (en) 1994-05-04
JPH04210279A (en) 1992-07-31
DE69008695T2 (en) 1994-09-08

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