GB2517436A

GB2517436A - Coating or sealing an internal surface of a workpiece

Info

Publication number: GB2517436A
Application number: GB1314811.9A
Authority: GB
Inventors: Marsel Arie Laor; Inbar Dag-Hartman; Eran Macover; Avinoam Tamir
Original assignee: PCT PROTECTIVE COATING TECHNOLOGIES Ltd
Current assignee: PCT PROTECTIVE COATING TECHNOLOGIES Ltd
Priority date: 2013-08-19
Filing date: 2013-08-19
Publication date: 2015-02-25
Also published as: GB201314811D0

Abstract

An apparatus for providing a vapour deposition coating to a cavity surface has at least one sealing element 1a to seal the cavity 7 and a vacuum port 9a for connection with a vacuum pump 9. Preferably, the cavity 7 takes the form of a tubular member 2, which is also sealed at its other end by a further sealing element 1. The apparatus also includes a vapour deposition reactor 20 which is positioned within the cavity 7, the reactor having a vaporizer 5 to provide a deposition vapour from a precursor. In some embodiments, the apparatus includes a reactor transporting mechanism to move the reactor 20 within the workpiece cavity 7. This mechanism may include a motor 8, which may operate a spool 6a for a cable 6 to move the reactor 20 along the cavity 7. In an alternative arrangement, the cable can be replaced by a rigid shaft. In some embodiments the reactor includes a pyrolysis chamber 4. A method for coating the cavity surface is also disclosed.

Description

COATING OR SEALING AN INTERNAL SURFACE OF A WORKPIECE

FIELD OF THE INVENTION

The present invention relates to surface coatings, in particular using vapor deposition.

BACKGROUND OF THE INVENTION

Vapor deposition processes such as physical vapor deposition (PVD) or chemical vapor deposition (CVD) and the like are used to improve characteristics such as hardness, wear resistance, oxidation and corrosion resistance; as well as other characteristics such as friction coefficient and adhesion of a workpiece's surface.

In the PVD process, a vacuum evaporation or mechanical sputtering of a precursor is followed by condensation of such vapors on a substrate surface to form thin film coating layers.

In a chemical vacuum deposition, a substrate is exposed to one or more volatile precursors that reacts, e.g. with other vapors or co-deposited species or decomposes on the substrate surface or polymerizes on the surface to produce desired deposit, for example an oxide, a nitride, a carbide or a carbon itride or a polymer.

One problem with the above processes is shadowing. If the workpiece has not been designed or positioned properly in a coating chamber, lack of vapor exposure will cause improper coating or sealing. Some solutions to those problems include using a rotating mechanism around one or more axes to reduce shadowing effects. Coating issues, such as shadowing, arise particularly when the workpiece or specimen has a cavity, and thus at least one aperture leading to that cavity.

Specimen geometry, size and internal cavity structure may further increase shadowing effects and create un-reachable cavities that cannot be effectively coated. Particularly when CVD is used, maintaining the vapors and the co-deposited species chemically available for further reactions is a big challenge.

Limited active vapor availability to such internal deposition targets inside a specimen cavity may sharply limit coating abilities.

SUMMARY OF THE INVENTION

The present invention relates to an apparatus and method for mitigating coating and/or surface sealing issues when coating a workpiece or specimen via CVD, PVD or the like (which may be referred to generically hereinafter in the specification and claims as "vapor deposition", "vapor coating", "vapor deposition coating", or derivatives thereof).

The terms "workpiece" and "specimen" may be used interchangeably herein

the specification and claims.

In accordance with embodiments of the present invention there is provided an apparatus for providing a vapor deposition coating to a cavity surface of a workpiece, the workpiece having a workpiece cavity defining a cavity surface, the cavity having at least one aperture. The apparatus includes: at least one sealing element adapted to respectively seal the at least one aperture of the cavity and having at least one vacuum pod configured for connection with a vacuum pump; and a vapor deposition reactor positionable within the cavity, the reactor having a vaporizer to provide a deposition vapor from a precursor, and the reactor having a vapor deposition outlet, whereby a vacuum can be achieved in the cavity and the vapor deposition reactor can be operated to produce a coating on the cavity surface.

In some embodiments, the apparatus's vapor deposition reactor further includes a pyrolysis chamber.

In some embodiments, the apparatus further includes a reactor transporting mechanism operably connected to the vapor deposition reactor and adapted to move the reactor within the workpiece cavity.

In some embodiments, the reactor transporting mechanism includes a motor; in some embodiments the reactor transporting mechanism includes a flexible cable; in some embodiments, the reactor transporting mechanism includes a rigid shaft; in some embodiments, the reactor transporting mechanism includes a magnetic element.

In some embodiments, the at least one sealing element further includes an electrical connection port. In some embodiments, the apparatus further includes a heating module associated with the reactor and having a temperature sensor and a controller therefor.

In accordance with embodiments of the present invention there is provided a method of coating a cavity surface of a workpiece cavity of a workpiece with a vapor deposition coating. The method includes: disposing a vapor deposition reactor within the cavity of the workpiece, the reactor being configured to provide a vapor deposition coating and having a reactor transporting mechanism adapted to move the reactor within the cavity; sealing the workpiece cavity; providing a vacuum to the workpiece cavity; and operating the vapor deposition reactor to produce a vapor deposition within the cavity, whereby a coating can be formed on the cavity surface.

In some embodiments, the method further includes moving the vapor deposition reactor within the cavity.

The at least one vacuum tight seal is configured to close (be seated on) at least one aperture of the cavity. The at least one vacuum tight seal is configured to seal the workpiece's cavity so that fluid (vapor) flow through the aperture is blocked. The at least one vacuum tight seal is configured to allow a connection from the sealed specimen's internal cavity to an external vacuum pump, to enable producing a suitable vacuum inside the specimen cavity. As will be described below, the at least one internal surface may then be vacuum coated or sealed.

The at least one vacuum tight seal has at least one feed through or connection port configured to be connected to an external vacuum pump. The external vacuum pump should be designed to produce a sufficient vacuum level inside a specimen cavity, upon the proper placement of the vacuum tight seal, in order to allow vacuum coating or sealing of at least one internal surface of the specimen cavity. In case the internal cavity of the specimen has more than one aperture, e.g. the specimen is a pipe-like workpiece having two (or more) apertures then, according to some embodiments of the invention, two (or more) vacuum tight seals may be used, with at least one or those vacuum tight seals having a feed through/connection port. According to some embodiments, additional feed through vacuum ports may be connected to other vacuum tight seals or to same vacuum seal (e.g. sealing plate), for example if a stronger vacuum is required, or if the same vacuum level is to be achieved faster.

According to some embodiments the at least one vacuum tight seal has an electrical port configured to electrically connect electrical devices, e.g. an electric motor located within the sealed cavity, to an external power supply.

Typically, the electrical port is designed to be vacuum sealable to help maintain the vacuum level produced by the vacuum pump. According to some embodiments, at least some of the internal electrical elements located in the cavity are configured to work with induced energy converters without physical electrical wiring.

According to embodiments of another aspect of the present invention there is provided a reactor configured to be placed in the internal cavity of the specimen. The reactor may have a heating module and may also have a driving module (e.g. a self-contained or associated reactor transporting mechanism). The electrical port may connect the heating module or the driving module to a power supply. In some embodiments, the heating module may be an inductive heating module without any external wiring. In some embodiments, the driving module may be remotely controlled such as by magnetic elements or other driving means. In some embodiments, the driving module may include an electrical motor configured to drive/move the reactor along the cavity of the specimen with a cable or shaft. In some embodiments, the driving module is configured to move the reactor in a predefined path along the cavity of the specimen. The velocity of the reactor, among other parameters, may control the thickness of the coating or sealing layer achieved.

In one non-limiting example, if the specimen is a pipe and the cavity to be coated is the internal surface of the pipe. With such a specimen configuration, the driving module may be adapted to either (or both) concentrically or eccentrically move the reactor from one edge of the sealed pipe to the opposite edge thereof, typically at a predetermined speed.

According to some embodiments, the apparatus may be configured to hold the workpiece in a horizontal orientation and the driving module is adapted to move the reactor horizontally back and forth with a rigid shaft of the apparatus. According to some embodiments, the apparatus may be configured to hold the workpiece in a vertical orientation and the driving module is adapted to move the reactor up and down along the internal cavity of the workpiece, for example using a flexible cable.

The specimen and its internal cavity may have any geometry and be regularly or irregularly shaped. For such geometries, the reactor and driving module can be designed to allow the reactor to move within such a cavity to allow effective distribution of the coating or sealing material within the cavity and to maintain the vapor's chemical availability for an effective deposition of at least one surface of the cavity.

In some embodiments, the apparatus includes a plurality of stationary reactors positioned inside the specimen cavity and designed to effectively spread the coating vapors to all targeted internal surfaces to be coated or sealed, which can be useful in large cavities. Alternatively, a single stationary reactor may be positioned in a specimen cavity to allow the vacuum coating or sealing of at least one internal surface of a specimen cavity.

According to another aspect of the present invention there is provided a method of coating or sealing a surface of at least one cavity of a specimen -each cavity having least one aperture. The method includes sealing the at least one specimen aperture with at least one vacuum tight seal to allow creating a vacuum level, through a vacuum port, within the at least one cavity.

The method further includes positioning the vapor deposition reactor inside the at least one cavity and the placement of a volatile precursor inside the reactor. In some embodiments, the method may further include heating the reactor to create available active vapors to efficiently coat or seal a target deposition surface inside the cavity. In some embodiments, the method may further include operating a reactor transporting mechanism, through an electrical port or wirelessly, to move the reactor along the sealed cavity while keeping an appropriate vacuum level, to allow efficient distribution and availability of active vapors along the cavity to ensure functional coating or sealing.

According to some embodiments there is provided an apparatus and method of coating a specimen's cavity, which has undergone a micro arc oxidation process (known also as Plasma Electrolitic Oxidation, PEO). The specimen thus has a porous oxidation film to be sealed in order to avoid corrosive agent penetration into the pores, and which may further result in corrosion of the substrate. Such specimen may be sealed according to embodiments of the present invention by sealing the internal cavity with a vacuum tight seal, inserting a reactor into the cavity, inserting a volatile precursor into the reactor and heating the reactor to produce active vapors in the specimen cavity. The method may further include creating a vacuum in the sealed cavity, heating the reactor and moving the reactor along the cavity of the specimen to achieve effective active vapor distribution along the internal target porous cavity surface to be sealed.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the appended drawings in which: Fig. 1 is a side view of an embodiment of an apparatus for providing a vapor deposition coating to a cavity surface of a workpiece in accordance with the present invention.

The following detailed description of embodiments of the invention refers to the accompanying drawing referred to above. Dimensions of components and features shown in the figures are chosen for convenience or clarity of presentation and are not necessarily shown to scale.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Illustrative embodiments of the invention are described below. In the interest of clarity, not all features/components of an actual implementation are necessarily described.

Fig. 1 shows an embodiment of an apparatus for providing a vapor deposition coating to a cavity surface of a workpiece, in accordance with the present invention. A non-limiting example of a specimen 2 in the form of a pipe is shown, and which may have a diameter of about 15 cm and a length of about 4 meters. A sealing element 1 is configured to seal the pipe cavity at one end of the pipe/specimen 2. A sealing element or seal la is configured to seal the pipe cavity at the other end of specimen 2. Sealing element is is typically an essentially vacuum tight seal and has a vacuum port 9a connectable to a vacuum pump 9. Seal la has an electrical port 8a configured to allow connection of an external power supply (not shown) in order to power internal electrical components such as an electrical motor 8, which is some embodiments is a component of a vapor deposition reactor transporting mechanism 10, described below. The apparatus further includes a vapor deposition reactor 20, also described below.

According to some embodiments, the electrical port 8a or vacuum port 9a is operably connected to wire sensors (not shown) such as position, speed, temperature, pressure, vapor density, impedance or optical sensors (e.g. a camera) located inside the cavity. In some embodiments, one or more of the sensors may be monitored by a microprocessor and controller (not shown), or by other means, to provide feedback and control in order to optimize the working parameters of the coating or sealing process.

According to some embodiments, the sublimation rate of the deposited coting vapor is monitored by the vapor pressure sensor so that a target predefined value of vapor pressure is maintained. At a known vapor pressure, the value of the deposition rate on the target deposited surface is known. By controlling the reactor temperature, the sublimation rate can be controlled and hence the vapor pressure is controlled. At any controlled vapor pressure, a controlled deposition rate may be achieved. It should be noted that, in large cavities in which the optionally moving vapor deposition reactor transporting mechanism is located, the velocity of the reactor 20 may also be controlled, among other parameters, by the diffusion rate at a certain working condition.

In some embodiments, vapor deposition reactor transporting mechanism 10 includes motor 8 connected to a spool 6a, which is configured to roll a cable 6 and move the vapor deposition reactor 20, which in some embodiments includes a reactor vapor outlet 3, pyrolysis chamber 4 and vaporizer 5. In some embodiments, the vaporizer 5 is configured to hold a volatile precursor such as Parylene. In some embodiments, vaporizer 5 includes a heating element (not shown); while in some embodiments the vaporizer is configured to be connected to an external heating source (e.g. wired through the electrical port 8a). According to such embodiments, Parylene is heated to sublime at least part of the Parylene into dimmers.

According to some embodiments, the reactor 20 may further include a pyrolysis chamber 4. In some embodiments, the pyrolysis chamber 4 may include an integral heating module (not shown), or be configured as to be connected to an external heating source, in order to provide heat to crack Parylene dimmers into monomers to be deposited on the target surface/substrate. The surface/substrate may be, for example, an oxidation porous layer in order to seal pores thereof.

According to some embodiments, the reactor outlet 3 is connected to pyrolysis chamber 4. In some embodiments, pyrolysis chamber 4 and the vaporizer 5 are connected by a connector.

The heating module may include one or more of a heater, isolation and temperature sensor; and a controller therefor. The reactor 20 may be wrapped by the heating module or heating element thereof, or the reactor can include and integral heating module/element.

In various embodiments, the reactor transporting mechanism 10 may be configured to move the vapor disposition reactor 20 along the pipe cavity 7 in such a way that monomer outlet 3 provides an effective amount of available active vapors for the target deposition surface. Optionally, outlet 3 may have a mechanism for facilitating a uniform coating distribution. In some embodiments, there might be an internal dispersion device (not shown) inside the pyrolysis chamber 4 that improves the uniformity of the coating distribution. In some embodiments, outlet 3 may have a non-uniform or directional orientation to serve specific deposition surface targets in the internal cavity of the specimen.

Parylene monomers have a spontaneous tendency to polymerize in the gas phase. Depositing polymerized Parylene provides poor sealing and coating results. This apparatus, among other things, is designed to enlarge the mean free path of the monomer, and overcome the problems encountered when costing cavities of various lengths and sizes. Maintaining a sufficient level of active vapors adjacent a deposition target surface, for example, when using Parylene, may be accomplished by keeping a sufficient level of monomers adjacent the target deposition surface to allow polymerization on the target surface with co-deposited monomers, or on-site polymerized surfaces. The mean free path of Parylene monomers limits the distance at which one can get uniform deposition to a certain distance, based on the specific parameters of each case. Therefore, according to some embodiments the reactor 20 should travel along the internal cavity 7 of (pipe) specimen 2 so that any target deposition surface is within the aforementioned "certain distance" in order to achieve an effective coating along the whole cavity.

In some embodiments, the temperature controller is adapted to facilitate temperature control along the cavity to improve coating thickness uniformity. It should be noted that different volatile surface deposition precursors may require different temperature ranges to achieve sublimation of the deposition material (e.g. Parylene). Moreover, not all precursors require an extra separate step of pyrolysis. Some polymer coatings and metallic coatings, such as titanium oxide, nitride, chrome, cadmium, gold or silver, can be evaporated and become available active vapors in a single step.

It should be understood that the above description is merely exemplary and that there are various embodiments of the present invention that may be devised, mutatis mutandis, and that the features described in the above-described embodiments, and those not described herein, may be used separately or in any suitable combination; and the invention can be devised in accordance with embodiments not necessarily described above.