FR3140888A1 - COATING DEPOSITION PROCESS - Google Patents

Abstract

PVD or PECVD deposition device comprising an enclosure (25) in which there is a part (22) to be coated movably mounted on a support (24), and a target (20) of a coating material to be evaporated and deposited on the part, the device comprising a mask (21) provided with a light (23) facing the part (22) to be coated and fixed with respect to the target (20), said mask being placed between the target and the part so that a movement of the part behind the light defines on the part a homogeneous coated zone with columnar deposit. Figure 3A

Description

COATING DEPOSITION PROCESS

The invention relates to the field of producing diamond-type carbon coatings with regular and progressive growth or graphite coatings on technical parts by PVD type deposition, physical vapor deposition in English or physical vapor deposition in French or type PECVD, Plasma-Enhanced Chemical Vapor Deposition in English or plasma-assisted chemical vapor deposition in French.

It is known to produce carbon PVD or PECVD deposits and, in the context of the development of diamond-like carbon coatings (DLC diamond like carbon in English), for example, a problem of different growth of deposits depending on the geometries of the parts of parts concerned, particularly in the context of parts with complex geometry exists. Depending on the position on the same part, the deposit can have a different microstructure, in particular the orientation of the columns of the deposited material can vary. This different orientation can lead to different properties. Thus, on the same part, the coating can have a different structure and thus different properties depending on its position on the part.

There represents for example a deposition by PVD process which results in the columnar growth of a coating 2 oriented at an angle θ between a substrate 1 and the columns of the coating 2.

In the case of tribological tests on coated parts with complex geometries, for example gears, it is extremely difficult to characterize the properties of the deposit directly on the final parts, especially on surfaces with a small surface area and/or a non-planar shape. these parts due to the fact that we do not control the orientation of the columns producing the covering.

It is therefore necessary to develop a deposition technique which can reproduce the different orientations of the columns forming a coating on a piece of chosen geometry in order to carry out classic tribological tests according to these orientations.

There are tribological tests making it possible to reproduce the rolling-sliding conditions at a point of contact between two parts and the samples used to do this are discs, balls and rollers. On the other hand, for a gear such as schematized in , at the level of the contact between two gear teeth 1a, 1b such that for example the tooth 1a is the tooth of a driving pinion and the tooth 1b the tooth of a driven pinion, the columns 12a, 12b of the coverings 11a, 11b are in opposition and the rolling-sliding kinetics between the surfaces is complex. In such a case, there is currently no tribological test to sort the coating solutions other than carrying out tests on the teeth. It is therefore necessary to find a way to carry out tests according to the different possible inclinations for the covering columns.

Technical problem

Known solutions do not make it possible to vary the deposition angle on samples and thus characterize the influence of this angle on the efficiency of deposition on parts in contact and moving.

In view of the prior art, the present disclosure proposes to produce, on samples representative of future surfaces in contact, a coating representative of that present on these surfaces and, to do this, to adapt the device and the spraying method.

To do this, the present disclosure firstly proposes a PVD or PECVD deposition device comprising an enclosure in which there is a part to be coated movably mounted on a support, and a target of a coating material to be evaporated and deposited on the part, which comprises a mask provided with a light facing the part to be coated and fixed relative to the target, said mask being placed between the target and the part, said movable mounted part, being positioned behind the mask in relation to the target such that a movement of the part behind the light gradually causes an area to be covered on the surface of the part behind the light. This makes it possible to create on the part an area coated with a columnar deposit of said material when the part moves under the light.

The light preferably defines an opening of size suitable for channeling a vapor deposition beam onto said area to be coated behind the light, a width of the light in a direction of movement, in particular of rotation of the part being defined between 1 and 7 cm.

A first axis perpendicular to said zone to be coated with said surface forms an angle greater than 0° and less than 90° relative to a second axis perpendicular to a plane of the target and directed towards the part.

The first axis perpendicular to said zone to be coated advantageously forms an angle greater than 10° and less than 80° relative to the second axis. Preferably, said angle can be defined between 20° and 70°.

According to a first embodiment, the part is rotated around said first axis.

According to a second embodiment, the part is rotated around a third axis perpendicular to the first axis and the second axis.

The part can have symmetry by rotation around a rotating axis, and said movement of the part relative to the support is a rotation around the rotating axis of the part. The light for its part is parallel to the surface to be coated and close to this surface, for example at a distance of a few millimeters, for example less than 15 mm, or even less than 7 mm or even 3 mm.

The mask may include a screen plate arranged on at least one edge of the light and parallel, at plus or minus 20°, to said second axis and in particular inclined at plus or minus 20° from said second axis. This screen plate is positioned and oriented to guide the beam coming from the target onto the surface.

The mask is advantageously made of steel.

1. - une pose de ladite pièce à revêtir, montée mobile par rapport au support, derrière le masque par rapport à la cible, avec la lumière du masque située en regard d’une zone de la surface de la pièce à revêtir,
2. - une mise en rotation de la pièce derrière ledit masque selon un mouvement de la pièce derrière la lumière adapté à faire défiler progressivement derrière la lumière ladite zone de la surface de la pièce à revêtir,
3. - une pulvérisation de matériau de revêtement en direction de la lumière et de ladite zone en sorte de réaliser sur la pièce une zone revêtue d’un dépôt colonnaire dudit matériau.

The present disclosure further relates to a deposition process using the device described above and comprising

1. - an installation of said part to be coated, mounted movably relative to the support, behind the mask relative to the target, with the light of the mask located opposite a zone of the surface of the part to be coated,
2. - rotating the part behind said mask according to a movement of the part behind the light adapted to gradually cause said area of the surface of the part to be coated to pass behind the light,
3. - a spraying of coating material in the direction of the light and of said zone so as to produce on the part a zone coated with a columnar deposit of said material.

The method can be such that, a first axis perpendicular to said zone to be coated under said light making an angle α with a second axis perpendicular to a plane of the target, the method comprises, before said spraying, an adjustment of said angle α, in function of an inclination of said columnar deposit to be produced.

Other characteristics, details and advantages of the invention will appear on reading the detailed description below of non-limiting examples of embodiment, and on analysis of the appended drawings, in which:

shows a microscope view of a coating deposited on a surface by a PVD process;

shows a schematic side view of gear teeth provided with a coating obtained by a PVD process;

shows a schematic top view of a first embodiment of the device of the present disclosure;

shows a schematic side sectional view of the device of the ;

shows a schematic side view of the device of the ;

shows a schematic top view of a second embodiment of the device of the present disclosure;

shows a schematic side view of the embodiment of the ;

shows a schematic top view of a third embodiment of the device of the present disclosure;

shows a schematic side view of the embodiment of the ;

shows a schematic top view of a variant of the embodiment of the ;

The drawings and the description below contain elements which may not only serve to better understand the present invention, but also contribute to its definition, where appropriate.

As described above, the represents a coating 2 formed in columns at an angle θ relative to the surface of a substrate 1. This angle θ will depend on the direction in which the coating particles are projected onto the surface of the part.

Depending on the position on the same part, the deposit can have a different microstructure and in particular the orientations of the columns can vary due to peaking and shading effects. This variable orientation can lead to different properties of the coating depending on its position on the part. Thus, the same deposit, on the same part, can have a different structure and thus different properties depending on its position.

It is also extremely difficult to characterize the properties of the deposit directly on the final part of complex geometry, especially when the surface concerned is of small surface area and/or of non-planar shape.

In the case of the for example we see that the orientation of the columns 12a, 12b of PVD coatings 11a, 11b in a contact zone between two teeth 10a, 10b of a gear will depend on the local curvature of these teeth when they are subjected to bombardment of particles intended to make the coating.

It is therefore desirable to be able to reproduce these orientations to better understand the behavior of the coatings according to the inclinations of the columns of said coatings and to be able to carry out tribological tests making it possible to reproduce the rolling-sliding conditions at a point of contact according to the inclinations of the coating columns. that we wish to test. To carry out tribological tests, the samples used are discs, balls and pebbles. The device of the present disclosure aims to produce coatings whose inclinations of the columns of material are controlled and known.

The challenge of the invention is thus to produce, on the surfaces of such samples, to be brought into contact, a coating representative of that present on areas of complex parts such as gear teeth in order to study their behavior (and with a possibility of controlling the angle of inclination of the columns, to be able to test the influence of this inclination).

The PVD or PECVD deposition device of the present disclosure comprises, according to the embodiment of the an enclosure 25 in which there is a part 22 to be coated, here an annular part of which one face must be coated, a target 20 which will provide the material to be evaporated to carry out the coating and a mask 21. The mask 21 placed between the target and the part 22 is provided with a light or opening 23. The part is movably mounted on a support 24, here a rotating support while the mask is stationary relative to the target.

The light is parallel to the surface to be coated and close to this surface, for example at a distance of a few millimeters, for example less than 15 mm, or even less than 7 mm or even 3 mm.

In this embodiment, the part 22 to be coated is an annular washer, the mask 21 is a disc and the light 23 is constituted here by a notch along an angular sector of the mask.

Still according to this embodiment, an axis X normal to the area to be coated is identical to an axis A of rotation of the part 22 on its support 24. The axis the target and the light 23 discover a small sector of one face of the annular part, the fixed disc of the mask being placed above the rotating part. The light thus forms on the part a zone to be coated with a normal axis , which makes it possible to coat the face of the part moving under said light 23 with a homogeneous deposit provided with columns of constant inclination θ such that θ=90°-α, α being the angle between the Y axis normal to the target and the X axis normal to the area of the part to be coated.

There view from the side of the light 23 makes it possible to better distinguish the positioning of the light 23 relative to the part 22 and the inclination α of the axis of rotation of the part relative to the normal to the plane of the target. The coating is deposited through the opening 23 on the surface of the part 22 gradually during the rotation of the latter, for example at a speed of 1 revolution/min to 50 revolutions/min depending on the application.

The dimensions of the light 23 are such that it defines an opening of size suitable for channeling a beam of vapor deposition onto a part of the part behind the light and orienting the deposit along parallel columns.

1. que l’ouverture ne soit pas trop petite, car sinon, du fait d’effets de pointe, on risque de tout déposer sur le masque, sans que le matériau n’atteigne la pièce,
2. Que l’ouverture ne soit pas trop grande non plus, pour rester assez directif angulairement,

To define the dimensions of the light, it is desirable:

1. that the opening is not too small, because otherwise, due to peak effects, there is a risk of everything being deposited on the mask, without the material reaching the part,
2. The opening should not be too large either, to remain sufficiently angularly directive,

In particular, a width of the light in a direction of rotation of the part defined between 1 and 7 cm makes it possible to obtain great homogeneity of the orientation of the columns.

The angle α between the first axis at 80° to obtain columns making respectively an angle with the surface of the part between 80° and 10°. In a particular embodiment, the angle α is chosen so that the columns make an angle of 40° to 60° with the surface of the part.

Figures 4A and 4B correspond to a second embodiment for which the mask 21a is made so as to mask part of a spherical part 22a. In this example, the part is movable in rotation around its axis of rotation A which coincides with an axis Z called the third axis perpendicular to the second axis Y normal to the plane of the target, the mask is conical with axis of revolution according to Z axis and includes a slot 23a made by an opening on a sector of the cone. Alternatively, the mask could be a spherical cap, for example a shell in the shape of a half-sphere, with a localized light corresponding to an angular sector, a circular light or a rectangular light. However, the conical mask as shown has the advantage of allowing the mask and the light to be very close to the part in the area to be coated, which is favorable for deposition.

As in the first embodiment, the light is offset by an angle α relative to the Y axis, that is to say that its angular position around the Z axis is offset relative to the Y axis by an angle α, so that the deposition under the light is done with a given inclination on the part. In the present case, the deposition is also carried out on the lower part of the spherical part not covered by the mask without this being problematic, the active part for the tests being the strip 26 located between two parallels at the level of the light.

In this embodiment, the mask is always fixed and the part 22a is rotated around the third axis Z perpendicular to the first axis angle dependent on the angle α is produced by the rotation of the spherical part 22a under the mask and the spraying of material on the unmasked zone 26 under the light 23a.

Figures 5A and 5B correspond to an embodiment for which the part 22b to be covered is cylindrical (it is a roller) and mounted on a support 24 provided with an axis of rotation A along an axis Z perpendicular to a Y axis normal to target 20 and for which the coating must be deposited on the cylindrical external wall of the part.

In this embodiment, the mask 21b is in the form of a cylindrical ring fixed relative to the target 20, surrounding said external wall and provided with a slot 23b in the form of a slot parallel to the axis of Z rotation.

In this embodiment, the inclination according to the angle θ of the columns is obtained by an angular offset α between the position of the window (angular position around the Z axis), and the Y axis perpendicular to the target 20 .

In the example of the , the mask comprises on at least one side of the light a screen plate 23c which will help to direct the particles and force unidirectional growth of the columns constituting the coating. This screen plate can, in the case of the embodiment of the be made by an edge raised by a notch formed in the disc constituting the mask 21, raising this edge precisely allows the window 23b to be opened.

The mask is advantageously made of steel which makes it a lightweight mask, easy to use, can be sanded for cleaning and inexpensive.

The parts to be covered can be metal, ceramic or polymer parts such as plastics.

Claims (11)

PVD or PECVD deposition device comprising an enclosure (25) in which there is a part (22) to be coated movably mounted on a support (24), and a target (20) of a coating material to be evaporated and deposited on the part, characterized in that it comprises a mask (21) provided with a light (23) facing the part (22) to be coated and fixed with respect to the target (20), said mask being arranged between the target and the part, said movable mounted part, being positioned behind the mask relative to the target such that a movement of the part behind the light gradually causes an area to be coated on the surface of the part behind the light . PVD or PECVD deposition device according to claim 1 for which the light (23) defines an opening of dimension adapted to channel a vapor deposition beam onto said zone to be coated behind the light, a width of the light in a direction of movement of the piece being defined between 1 and 7 cm. PVD or PECVD deposition device according to claim 1 or 2 for which a first axis (X) perpendicular to said zone to be coated with said surface forms an angle (α) greater than 0° and less than 90° relative to a second axis (Y) perpendicular to a plane of the target and directed towards the part. PVD or PECVD deposition device according to claim 3 for which the first axis (X) perpendicular to said zone to be coated forms an angle (α) greater than 10° and less than 80° relative to the second axis (Y) and preferably between 20° and 70°. PVD or PECVD deposition device according to claim 3 or 4 for which the part is rotated around said first axis (X). PVD or PECVD deposition device according to claim 3 or 4 for which the part is rotated around a third axis (Z) perpendicular to the first axis (X) and the second axis (Y). PVD or PECVD deposition device according to any one of the preceding claims for which the part has symmetry by rotation around a rotary axis (A), and for which said movement of the part relative to the support is a rotation around the rotating axis (A) of the part. PVD or PECVD deposition device according to any one of the preceding claims for which the mask comprises a screen plate (23c) arranged on at least one edge of the light and parallel, at plus or minus 20°, to said second axis (Y). . PVD or PECVD deposition device according to any one of the preceding claims for which the mask is made of steel. Deposition process using the device according to any one of the preceding claims comprising:

1. - a placement of said part to be coated, mounted movably relative to the support, behind the mask relative to the target, with the light (23) of the mask located facing an area of the surface of the part (22) to put on,
2. - rotating the part behind said mask according to a movement of the part behind the light adapted to gradually cause said area of the surface of the part to be coated to pass behind the light,
3. - a spraying of coating material in the direction of the light and of said zone so as to produce on the part a zone coated with a columnar deposit of said material.

Deposition method according to claim 10, for which, a first axis (X) perpendicular to said zone to be coated under said light making an angle α with a second axis (Y) perpendicular to a plane of the target, the method comprises, before said spraying, an adjustment of said angle α, as a function of an inclination of said columnar deposit to be produced.