JP2012241284A - Arc spraying method for forming dense layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an arc spraying method for forming a dense layer on a substrate.SOLUTION: A voltage is applied to two electrically conductive spraying wires 2 so as to generate an arc 6 between the spraying wires 2, whereby a melt 8 is formed from the spraying wires 2 in a melting region 7, and the melt 8 is acted on by a fluid 4. The fluid 4 transfers the melt 8 and deposits it onto the substrate 10 to form the layer 18 on the substrate. During the transfer of the melt 8, oxidizable particles 11 are supplied to the melt 8 and are deposited onto the substrate 10 together with the melt 8. After the arc spraying, the oxidizable particles 11 are at least partly oxidized to densify the layer 18.

Description

  The present invention relates to an arc spraying method for producing a dense layer as described in the preamble of claim 1. Furthermore, the present invention also relates to a dense layer produced by this arc spraying method.

  Coatings produced by thermal spraying are often exposed to corrosive environments. For example, coatings on ship decks are particularly susceptible to damage due to corrosion because they are exposed to severe air, including sea water. As is generally accepted, it is known to apply a corrosion protection layer, for example as a special paint or coating, but in this respect a phenomenon called subsurface corrosion often occurs. That is, corrosion occurs on the substrate under the coating. As a result of this corrosion, the coating, i.e. the protective paint or the sprayed protective layer, for example, can be removed as debris from the substrate. The cause of this subsurface corrosion can be the natural damage of the protective coating, which causes corrosion-causing materials, such as sea water, to reach the substrate and cause corrosion there. However, it is also possible for the material causing corrosion to reach the substrate through the undamaged protective layer by capillarity or diffusion processes. Thus, the protective layer is only apparent and not sufficiently dense. This action is particularly promoted when the protective layer is very rough. However, a very rough protective layer is often desirable for safety measures, for example to minimize the risk of sailors slipping on a ship deck.

  The object of the present invention is therefore to propose an inexpensive and simple method for producing a dense layer on a substrate, the dense layer being arranged under the layer, in particular against corrosion. It is possible to protect. The dense layer should be provided by the present invention.

  The subject of the invention for achieving this object is characterized by the independent claims of each category.

  According to the present invention, an arc spraying method for producing a dense layer on a substrate is proposed. That is, a voltage is applied between the two conductive spray wires, thereby generating an arc between the spray wires. A melt is formed from the spray wire in the melting region and the melt is acted on by the fluid to move the melt to the substrate where it is deposited to form a layer. Oxidizable particles are supplied to the melt and deposited with the melt on the substrate to oxidize the oxidizable particles at least partially for densification of the layer after thermal spraying is complete.

  Arc spraying, more precisely, is a spraying process often referred to as wire arc spraying, which can deposit a layer on a substrate in an inexpensive and simple manner. The oxidizable particles supplied to the melt are at least partially oxidized after the spraying process. The particles increase their volume by oxidation to densify the layer and seal the layer. In this way, the substrate placed under the layer can be protected from corrosion with very particular efficiency. Since the particles are dispersed throughout the layer, not only is the surface of the layer densified, but the entire layer is sealed within it.

  In particular, it has proven to be practically advantageous if the oxidizable particles have a volume of 3% to 20% of the volume of the layer.

  According to a first preferred process control, the oxidizable particles are mixed with a fluid, which then acts on the melt. Thus, the particles impinge with the fluid on the melting area, where they transport the melt to the substrate.

  Another preferred process control has the step of adding particles oxidizable between the melt zone and the substrate to the melt. In this variant, oxidizable particles are introduced into a “jet” downstream of the melting region, which carries the melt to the substrate.

  Furthermore, the oxidizable particles can be a component of at least one spray wire. The spray wire is then designed, for example, as a hollow wire or so-called “core wire”. That is, the oxidizable particles are incorporated into the spray wire.

  Further possible process management comprises providing a third spray wire comprising oxidizable particles.

  According to a preferred embodiment, the oxidizable particles comprise iron, zinc, aluminum or magnesium or alloys of these elements. These elements or alloys can be oxidized particularly easily. With respect to iron, there are a plurality of oxidizable iron compounds or iron-based materials whose iron content is at least 50% by weight. They are suitable for the method according to the invention, for example iron-based materials with chromium and / or aluminum. Aluminum, magnesium or zinc is also suitable due to their easy oxidizability and the accompanying increase in volume. Thus, the oxidized aluminum powder has a volume that is approximately three times the volume of the unoxidized aluminum powder, for example. Furthermore, the alloy ZnAl85 / 15 containing 85% zinc and 15% Al by weight is suitable. One criterion for proper selection of oxidizable particles is that they do not have a significant tendency to alloy with the spray material. That is, oxidizable particles are greatly possible, although it is not necessary to re-solidify when they are melted or plasticized by the method according to the invention and then applied to the substrate together with the melt. In such a case, it is not desirable that the oxidizable particles form an alloy with the thermal spray material, in which case, in some cases, it can no longer be oxidised, or at least not easily oxidizable. An exception may be that the oxidizable particles form an alloy or other compound that can be readily oxidized with the components of the sprayed material. Then, it can of course be directly utilized that the oxidizable particles are formed only during the thermal spraying process, or that the oxidizable particles enter the compound and are oxidizable particles.

  It is common for oxidizable particles to be oxidized by water.

  The method according to the invention is also particularly suitable for applications where the substrate is made of steel or the surface is steel. In particular, the subsurface corrosion of the steel under the layer can be suppressed or delayed at least effectively, if not actually prevented permanently by the sealing of the layer or by the denseness of the layer.

  Furthermore, a dense layer made using the method according to the invention is proposed.

  The dense layer preferably has an internal compressive stress. The internal compressive stress of the dense layer can be generated directly by oxidation of the oxidizable particles. This is because the internal compressive stress is formed due to the volume increase associated with oxidation, which can significantly improve the durability or adhesion of the layer on the substrate.

  Further advantageous and preferred embodiments of the invention are described in the dependent claims.

  Hereinafter, the present invention will be described in more detail with reference to examples and drawings. In the schematic drawing, a part is shown by sectional drawing.

1 shows the main components of an arc spraying device for carrying out a first embodiment of the method according to the invention. FIG. 2 is a view similar to FIG. 1 but showing the main components of an arc spraying apparatus for carrying out a second embodiment of the method according to the invention. FIG. 4 shows a spray wire for another embodiment of the method according to the invention. Schematic for clarifying another Example.

  FIG. 1 schematically shows the main parts of an arc spraying apparatus suitable for carrying out a first embodiment of the arc spraying method according to the invention, which can be used to produce a dense layer 18 on a substrate 10. Shown in the figure.

  The arc spraying apparatus comprises a spray gun 1, a first supply device 3, a storage container 12 for oxidizable particles 11 (the oxidizable particles 11 are usually present in the storage container 12 in the form of a powder). 12. Includes a control unit 14 for controlling the process. The spray gun 1 comprises, in a known manner, two conductive spray wires 2 that are connected to an energy source 16 that generates an arc 6 in the melting region 7 between the spray wires 2. The electrical energy is supplied so that the arc can be maintained over a predetermined period in a stable manner. The spray wire 2 can be supplied from a storage device (not shown) of the wire guide 5. The wire guide 5 includes a wire feed 13 suitable for feeding the spray wire 2 through the guide device 17 to the melting region 7. The guide device 17 can be connected to the energy source 16 as a conductive device and is in conductive contact with the spray wire 2, so that the electrical energy required for the generation of the arc 6 is passed to the spray wire 2 via the guide device 17. It is preferable to be designed so that it can be supplied. Since the material of the spray wire 2 is continuously moved into the melt 8 during arc spraying in the melting region 7, the spray wire 2 is moved into the melting region 7 by the wire guide 5 to maintain the arc 6. Need to be fed continuously.

  The arc spray process can be performed in a controlled atmosphere, but it need not be. In this case, the method is carried out in the processing chamber 30, which is only shown in FIG. 1, and its atmosphere can be set or monitored in a known manner using a pump and gas supply (not shown). .

  The melt 8 formed by the arc 6 from the material of the spray wire 2 is acted on by the fluid 4 supplied from the gas reservoir 19 via the first supply device 3. The fluid 4 carries the melt 8 to the surface 9 of the substrate 10 to be coated, whereby a layer 18 is formed. The melt 8 is acted on by the fluid 4 at a predetermined operating pressure, which is preferably a gas, specifically oxygen, nitrogen, argon, helium, ambient air, a mixture thereof, or another gas. Thereby, the melt 8 is struck against the surface 9 of the substrate 10. The melt 8 then condenses into a solid state.

  According to the present invention, the oxidizable particles 11 are supplied to the melt 8, and the oxidizable particles 11 are deposited on the substrate 10 together with the melt 8. For this purpose, according to the first embodiment described here, the oxidizable particles 11 are mixed with the fluid 4, after which the fluid 4 acts on the melt 8.

  For this purpose, a connection 15 is provided, whereby the oxidizable particles 11 can be moved from the storage container 12 to the supply device 3. There, oxidizable particles are carried by the fluid 4 and the particles 11 act on the melt 8 together with the fluid 4 in the melting region 7. In this way, the oxidizable particles 11 are mixed with the melt 8 in the melting region 7 and supplied to the melt 8 by the fluid 4 so as to be applied together with the melt 8 on the surface 9 of the body 10. .

  In this process, the oxidizable particles 11 can be partially melted, melted or plasticized. In this case, the material of the particles 11 should preferably be selected such that substantially no alloy or compound between the particles 11 and the material of the spray wire 2 is formed. However, it is also possible for the oxidizable particles 11 to be substantially solid during transport in the melt 8 and remain dimensionally stable. The particles 11 are usually solid particles, are not melted in the melt 8, retain their outer shape, and remain substantially in a solid state. Of course, it is possible that only a slight dissolution of the particles 11 occurs on the surface.

  After completion of the spraying process, the oxidizable particles 11 are oxidized in the layer 18. This is done by the action of the oxidation means. A possible oxidation means is water. The water can, for example, leave layer 18 in the immersion bath and can be sprayed onto layer 18 or onto layer 18 or onto substrate 10. Of course, an oxidation means different from water can be used. The volume of the oxidized particles 11 is increased compared to the unoxidized state. Thus, the particles 11 will expand to some extent, thereby closing or filling the pores, capillaries or other openings or tubes in the layer 18. Thus, layer 18 is sealed by oxidation. This sealing occurs not only at the surface of the layer 18 but also anywhere in the layer 18. This then results in that no liquid can actually penetrate anymore into the layer 18 and the substrate 10 is still very effectively protected, especially from subsurface corrosion. Since sealing or densification occurs throughout layer 18, it is possible to design the surface of layer 18 to be rough and rough without compromising quality. This is advantageous, for example, as a precaution that layer 18 is less slippery when it is a surface, for example, a deck of a ship on which personnel walk.

  Another advantageous effect that can be realized by increasing the volume of the particles 11 is the generation of internal compressive stress 18. The compressive stress is generated in the layer 18 due to the expansion of the particles 11 during oxidation, and has a beneficial effect on the durability or adhesion of the layer 18.

  If it is desired that the oxidizable particles 11 do not melt during the spraying process, the shape stability of the particles 11 in the melt 8 can be ensured by several parameters, i.e., of course, It can be ensured by a suitable choice for the material of the particles 11, on the other hand, by the size of the particles 11 or by the flow rate of the fluid 11. In addition, the melting of the particles 11 can naturally be realized by the same parameters.

  A large number of materials are suitable as oxidizable particles 11, which in particular are in the form of solid particles, which then serve to densify the layer 18. For example, zinc, aluminum, magnesium, iron, or alloys of these elements with each other or with other elements are suitable. Specifically, iron-based compounds with an iron content greater than 50% are suitable, or the alloy ZnAl85 / 15 containing 85% zinc and 15% iron is also suitable.

  In order to control or regulate the process, the arc spray device has, for example, a freely programmable control unit 14. With it, in particular, the following parameters can be adjusted or set: the working pressure at which the fluid 4 acts on the melt 8, the feed rate of the particles 11, the wire feed 13 and the spray wire 2. Is the electrical energy supplied to the. For this purpose, the control unit 14 is connected via a signal line 20 to the respective components of the device. In addition, the control unit 14 can include a sensor line 21 such that the current operating pressure, gas pressure in the processing chamber, ambient pressure, temperature, electrical source operating parameters of the energy source, or other parameters, etc. Different operating parameters can be communicated to the control unit 14 by sensors not shown.

  To produce the dense layer 18, the melt 8 formed in the melting region 7 by an arc spray process is first transported to the surface 9 of the substrate 10 by the fluid flow to which the particles 11 have been added, where Thus, the melt 8 is deposited in the form of splash or droplets. Oxidizable particles 11 are present in the form of solid particles, or in a partially melted or melted form, and are incorporated into the forming layer 18. When the desired layer thickness is reached, the spray process is terminated. In a further processing step, the oxidizable particles 11 are oxidized in the solidified layer 18 so that the layer 18 is sealed.

  FIG. 2 shows the main components of an arc spraying apparatus for carrying out a second embodiment of the arc spraying method according to the present invention. Only the differences from the first embodiment are considered below. The above description regarding the first embodiment is also applied to the second embodiment. The same reference numerals indicate the same parts, or parts that are functionally equivalent to the functions in the first embodiment.

  The main difference from the first embodiment is that in the second embodiment, oxidizable particles 11 are added behind the melting region 7 in the flow direction.

  For this purpose, a second supply device 31 is provided which can introduce oxidizable particles 11 from the storage container 12 into the melt 8. Here, the introduction of the particles 11 is performed only between the melting region 7 and the substrate 10. For this purpose, the second supply device 31 has an opening 32 which is arranged near the melting region 7 but on the substrate side of the melting region 7. Thus, the particles 11 can be introduced from there into a coated jet formed from the melt 8 and the fluid 4. The particles 11 can also be transported through the second supply device 31 with the aid of the fluid 4 in this embodiment. For this purpose, the second supply device 31 is connected, for example, to the gas reservoir 19 or to a remote fluid reservoir (not shown in FIG. 2).

  Also, the apparatus shown in FIG. 2 has an energy source 16, the example diagram of which is omitted here for clarity.

  Further, the melt 8 formed by the arc 6 from the material of the spray wire 2 is similar to the above-described embodiment in that the base 10 is fed from the gas reservoir 19 by the fluid 4 via the first supply device 3. Applied to the surface 9. The oxidizable particles 11 move from the openings 32 into the melt 8 and are then conveyed along with the substrate 10.

  According to another embodiment of the method according to the invention, oxidizable particles can be included in one or both spray wires 2. At this time, the spray wire 2 is designed as a core wire and additionally contains oxidizable particles 11 in addition to the actual, eg metallic, coating material. FIG. 3 is a sectional view of the spray wire 2. In this embodiment, it is no longer necessary to supply oxidizable particles 11 from the storage container shown in FIGS. In this alternative embodiment, the oxidizable particles 11 are released at the melting region 7 upon melting of the spray wire 2, then move to the substrate 10 and are carried along with the melt 8 by the fluid 4. At that time, the volume ratio of the particles 11 in the layer 18 can be set by the relative ratio of the particles 11 in the spray wire 2.

  FIG. 4 schematically illustrates another embodiment. In this embodiment, at least one third spray wire 22 containing oxidizable particles 11 is provided. This third spray wire 22 is introduced into the melting region 7 where its tip is melted and oxidizable particles 11 are released by the fluid 4 so as to be transported along with the melt 8 to the substrate 10. The It should also be understood that a wire feed is provided for the third spray wire 22. The third spray wire 22 can be supplied with current or without current. When a current is passed through the third spray wire 22, it can be selectively powered as a cathode or as an anode. For example, at least one additional arc occurs. However, the third thermal spray wire can be connected to the third thermal spray wire even when no electricity is passed, such that the third thermal spray wire melts only by the heat of the melting region generated by the arc between the two thermal spray wires 2. It is possible to conduct heat.

Claims (11)

An arc spray method for producing a dense layer on a substrate, wherein a voltage is applied to two conductive spray wires (2) to generate an arc (6) between the spray wires (2), A melt (8) is generated from the spray wire (2) in the melting region (7), the melt (8) is acted on by the fluid (4), and the melt (8) is acted on by the fluid (4). In the arc spraying method, the layer (18) is formed by moving the substrate (10) to the substrate (10) and attaching the melt (8) to the substrate (10).
Supplying oxidizable particles (11) to the melt (8) to adhere the particles (11) together with the melt (8) on the substrate (10);
After the end of the arc spraying, the arc spraying method is characterized in that the oxidizable particles (11) are at least partially oxidized in order to densify the layer (18).   The method of arc spraying according to claim 1, wherein the oxidizable particles (11) occupy 3% to 20% of the volume of the layer (18).   The arc spraying method according to claim 1 or 2, wherein the oxidizable particles (11) are mixed with the fluid (4), and then the fluid (4) is applied to the melt (8). .   The oxidizable particles (11) are added to the melt (8) between the melting region (7) and the substrate (10) according to any one of claims 1 to 3. The described arc spraying method.   Arc spraying method according to any one of claims 1 to 4, wherein the oxidizable particles (11) are components of at least one spray wire (2).   The arc spraying method according to any one of claims 1 to 5, wherein a third spray wire (22) containing the oxidizable particles (11) is provided.   The arc spraying method according to any one of claims 1 to 6, wherein the oxidizable particles (11) comprise iron, zinc, aluminum, magnesium, or an alloy of these elements.   The arc spraying method according to any one of claims 1 to 7, wherein the oxidizable particles (11) are oxidized with water.   9. The arc spraying method according to any one of claims 1 to 8, wherein the substrate (10) is made of steel or has a steel surface.   A dense layer manufactured by the arc spraying method according to any one of claims 1 to 9.   11. A dense layer according to claim 10, having internal compressive stress.

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