CA2379902A1 - Thermal spraying equipment - Google Patents

Thermal spraying equipment Download PDF

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Publication number
CA2379902A1
CA2379902A1 CA002379902A CA2379902A CA2379902A1 CA 2379902 A1 CA2379902 A1 CA 2379902A1 CA 002379902 A CA002379902 A CA 002379902A CA 2379902 A CA2379902 A CA 2379902A CA 2379902 A1 CA2379902 A1 CA 2379902A1
Authority
CA
Canada
Prior art keywords
throat
thermal spraying
spraying apparatus
feedstock
inserts
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA002379902A
Other languages
French (fr)
Inventor
Michael Walter Seitz
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
METALSPRAY INTERNATIONAL LC
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of CA2379902A1 publication Critical patent/CA2379902A1/en
Abandoned legal-status Critical Current

Links

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B05SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05BSPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/16Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas incorporating means for heating or cooling the material to be sprayed
    • B05B7/22Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas incorporating means for heating or cooling the material to be sprayed electrically, magnetically or electromagnetically, e.g. by arc
    • B05B7/222Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas incorporating means for heating or cooling the material to be sprayed electrically, magnetically or electromagnetically, e.g. by arc using an arc
    • B05B7/224Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas incorporating means for heating or cooling the material to be sprayed electrically, magnetically or electromagnetically, e.g. by arc using an arc the material having originally the shape of a wire, rod or the like

Abstract

Thermal spraying apparatus comprises a spray head defining a nozzle with a throat (132) through which gas under pressure can be supplied. First and second guides are provided to guide feedstock wires (124) towards a point of intersection in or adjacent an end of the throat, preferably at an angle of between 45 and 90 degrees. The gas is forced through the throat at high pressure, preferably at a pressure sufficient to cause supersonic flow, thereby generating a finely atomised spray of molten feedstock material. The feedstock guides can take the form of drilled tubular inserts, or inserts with grooves which are received in cavities in body halves of the spray head.

Description

THERMAL SPRAYING EQUIPMENT
BACKGROUND OF THE INVENTION
THIS invention relates to thermal spraying equipment and to a thermal spraying method for producing corrosion resistant and/or hard coatings on a substrate.
International patent application no. WO 98/00574 describes a thermal spraying method and apparatus of the above general kind.
It is an object of the invention to provide a method and apparatus which is a development of the known method and apparatus.
SUMMARY OF THE INVENTION
According to the invention there is provided thermal spraying apparatus comprising a nozzle defining a throat having an inlet and an outlet and a gas flow path which is aligned with the axis of the throat, so that gas under pressure can be supplied to the inlet; at least first and second guides arranged to guide respective feedstock wires via the inlet towards a point of intersection in or adjacent an end of the throat; a power supply arranged to be connected to the feedstock wires to cause an arc in the throat between the wires; and a supply of compressed air arranged to supply air to the throat, the guides being arranged to direct the feedstock wires to the point of intersection so that they define an angle of between 45° and 90°
between them.
Preferably, the guides are arranged so that the angle defined between the feedstock wires is approximately 60°.
The nozzle may be formed from first and second body halves, each defining a portion of the throat. Typically the throat is tapered between the inlet and the outlet.
The guides may comprise respective bores formed in the body halves and each intersecting the portion of the body half defining a respective portion of the throat, each bore being inclined relative to the axis of the throat.
The guides may include inserts receivable in the respective bores, each insert having an aperture therein through which a feedstock wire can pass, and having an inclined end face shaped complementally to the shape of the throat.
Alternatively, the respective bores may intersect locating cavities, inserts being receivable in the locating cavities so that they abut feedstock wires passing through the respective bores.
The inserts may be polygonal in section and define planar faces each having a locating formation for engagement with a feedstock wire in use.
Preferably, the inserts are square in section and define planar, rectangular faces with a groove formed in at least one face for engagement with a feedstock wire in use.
The inserts may comprise copper or copper/tungsten.
The body halves are preferably conductive, with a terminal or contact on each body half for connection to the power supply.
The body halves are preferably mounted on a non-conductive head which holds the body halves in a spaced-apart condition.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an exploded view of a first embodiment of a spray head of thermal spraying apparatus according to the invention;
Figure 2 is a pictorial view of the apparatus of Figure 1;
Figure 3 is a rear end view of the apparatus of Figure 1;
Figure 4 is a section on the line 4-4 in Figure 3;
Figure 5 is a partial exploded view of a second embodiment of a spray head of the apparatus; and Figure 6 is a sectional view of the second embodiment of the spray head.
DESCRIPTION OF EMBODIMENTS
The apparatus illustrated in Figures 1 to 4 comprises a thermal spraying head which is connected in use to a source of compressed air or nitrogen by means of a hose 10, and to a high current power supply 12 in use.
The general principle of operation of the apparatus is substantially similar to that described in the abovementioned international patent application no. WO
98/00574, the contents of which are incorporated herein by reference.
The spray head of the apparatus comprises first and second conductive body halves 14 and 16 which are machined from aluminium alloy and which are mounted on a non-conductive head 18 which can, for example, be moulded or machined from a suitable plastics material such as PTFE.
As shown in the exploded view of Figure 1, the body halves 14 and 16 are attached to the head 18 hingedly by means of pins, which assist in assembly of the head and in correct location of the body halves with respect to one another. An outer sleeve 56 of tough plastics material such as nylon holds the body halves in position and is located positively by a pin 58.
The front face of the head has a circular central portion 20, at the centre of which is an outlet 22 of a nozzle which has an inlet 24, and a cylindrical throat 26 extending between the inlet and the outlet. The throat is tapered from the inlet to the outlet such that it has an inlet diameter of 8mm and an exit diameter of 8.5mm.
Cavities 28 and 30 are machined into the respective body halves 14 and 16, and define respective inclined bores 32 and 34 which intersect with respective grooved portions 36 and 38 of the body halves which define the throat 26, at an angle of approximately 30° to the axis X-X of the throat, so that the included angle between the two bores 34 is 60°.
Locatable within each bore is a copper insert 40, the inserts 40 having ends 42 which are shaped complementally to the grooved surfaces 36 and 38 defining the throat of the nozzle, so that when the inserts are in position in the bores 34, their ends 42 are flush with the surface of the throat. A bore is formed in each insert which is sized to receive a metal feedstock wire 46 and to make electrical contact with the wire as the wire passes through the insert and into the throat 26.
In the prototype apparatus, the feedstock wires 46 were directed to a point of intersection at the outer end of the throat 26 essentially coinciding with the outlet 22 and the central axis X-X of the throat. In some applications, it may be desirable to move the point of intersection outside the throat, although it has been found in practice that it is generally preferred for the point of intersection to be within the throat.
Electrical terminals 48 and 50 on the respective body halves 14 and 16 are provided for connection of heavy duty conductors 52 and 54 which connect the body halves to the power supply 12, and which thus pass current to the feedstock wires 46 via the body halves and the copper inserts, causing an arc at the point of intersection of the feedstock wires in the throat. In the prototype apparatus of the invention, the power supply 12 was a constant voltage source operating at approximately 42 to 48 volts (compared with approximately 32 to 36 volts in the case of conventional apparatus). The arc current was between 150 Amperes and 300 Amperes and the gas pressure at the entrance 2 to 5 bar (g), typically 4 bar.
Figures 5 and 6 illustrate a second embodiment of a thermal spraying head according to the invention. The second embodiment is to a large extent similar to the first, and Figure 5 therefore illustrates only a single conductive body half 114, which corresponds to the body half 14 of Figure 1. The body half 114 mates with a complemental body half 116 (see Figure 6) and the halves are assembled to a non-conductive body in the same way as in the first embodiment.
The main difference between the first and second embodiments is that in the latter case, each body half defines a rectangular slot or cavity 118 which receives a contact tip in the form of a removable insert 120. A relatively small bore 122, which is larger in diameter than the diameter of the feedstock wires 124, extends from an upstanding head portion 126 of the body half 114, exiting the head portion 126 at the base thereof, just above the bottom of the cavity 118, and extending further through an end portion 128 of the body half as best seen in the sectional view of Figure 6. The insert 120 has a central groove 134 machined in each of its four adjacent faces, so that the grooves effectively run around the body of the insert. The function of the insert is described in more detail below. As in the first embodiment, the alignment of the bores 122 and the central groove 134 in the insert 120 is such that the feedstock wires 124 intersect at a point just within or just beyond the end 130 of a throat 132 defined between the two body halves.
The throat 132 in this embodiment is a tapered square/rectangular section channel, rather than a conical bore, since this is easier to machine and a round orifice for the outlet is not a prerequisite. The entrance to the throat is 6 mm by 6 mm, with the exit being 6 mm by 7 mm (rectangular).
The insert 120 serves the same purpose as the copper inserts 40 of the first embodiment, and typically comprises copper or copper/tungsten. A through bore 136 extends through the insert from side to side, and is provided to facilitate storage of the inserts. In the prototype, the insert was approximately 20 mm in length in the direction of the through bore 136, and the faces thereof were 12 mm square with the grooves 134 being approximately 1 mm deep. Dimples 138 are provided on each face on either side of the central groove, and serve as locators for locking balls or grub screws 140 as shown in Figures 5 and 6.
As mentioned above, the feedstock wires 124 lie within the grooves 134 in use (see Figure 6), with the insert providing the force which directs the feedstock wire to its point of intersection, thus providing sufficiently good electrical contact between the feedstock wire and the insert.
The above described inserts have a number of advantages over the tubular inserts 40 of the first embodiment. Firstly, each insert has four wear surfaces, so that it need only be rotated through 90 degrees to present a fresh surface. This means that the life of the insert is relatively long. It has been found that this insert does not clog as easily as is the case with drilled-hole inserts. The insert is easy to manufacture, and is also easily fitted into the spray gun head from the front thereof.
As described in the abovementioned International patent application, the pressure and volume of the gas supplied to the interior of the nozzle are preferably adjusted to cause sonic or choked gas flow within the throat prior to generation of an arc, so that the generation of an arc within the throat has the effect of generating supersonic flow within or just beyond the exhaust end of the nozzle, which would otherwise not be attainable. The resultant high flow velocity results in very fine atomisation of the molten feedstock particles _ g _ and very high particle speeds as the particles are emitted from the nozzle towards a substrate.
It has been found that by using a flow of gas which is sonic or supersonic and positioning the arc in the area of supersonic or sonic flow, the most effective results are obtained.
Due to the very high temperature of the arc (typically 4000°C) the arc rapidly heats and drastically expands the gas entering the arc. This rapid expansion effectively acts as a gas source in the flow field, effectively blocking the flow of gas through the arc. Due to this blockage effect, the gas tends to flow around the "obstruction", similarly to the way water flows around a concrete pillar of a bridge.
When a supersonic gas flow exists, the gas flowing towards the "obstruction"
(the arc) is not "aware" of the arc until it actually enters the arc zone and the gas is thereby forced into the arc region. The resulting high pressure, high flow situation results in very fine atomisation of the molten feedstock. Thus, where a supersonic basic gas flow is used, the arc can be positioned anywhere along the throat, up to and including the exit region of the throat and just beyond it. In the case of a supersonic output spray, the exhausting flow has a diamond shaped supersonic flow field structure.
The feedstock wires 46 can be conventional solid wires, but it has been found that the use of cored wires comprising a tubular metallic body containing a cermet powder, together with the use of nitrogen or another suitable inert gas, provides excellent results. The cermet material, typically an agglomerated and sintered mix of metal and carbide, tends to improve the deposition of carbide material from the thermal spray method, as the hard carbide material is contained within a metal binder. Use of pure nitrogen or another suitable inert gas protects the atomised metal feedstock particles _g_ from oxidation, significantly improving the quality of the coating produced.
It has been found that utilising relatively short spray distances between the outlet of the nozzle and the substrate to be coated, preferably less than 100 mm and down to as little as 5 mm, further reduces the formation of oxides which detrimentally effect the quality of the coating. In prior art devices, short spraying distances can lead to overheating of the substrate, but due to the very high gas flow through the spray device of the invention, the gas jet has a cooling effect, preventing overheating.
It is believed that the use of a relatively steep angle of intersection between the feedstock wires of at least 45°, and typically 60°, compared with the conventional angle of intersection of approximately 30°, ensures that the ends of the feedstock wires at the point of generation of the arc are more stable in the high velocity gas stream in the throat, and that the atomisation of the molten metal resulting from the arc is more uniform due to the smaller exposed surface cross section of the feedstock wires. In this regard, the design of the wire guides so as not to protrude into the throat and therefore not to disturb the gas flow in the throat is also important.

Claims (11)

CLAIMS:
1. Thermal spraying apparatus comprising a nozzle defining a throat having an inlet and an outlet and a gas flow path which is aligned with the axis of the throat, so that gas under pressure can be supplied to the inlet; at least first and second guides arranged to guide respective feedstock wires via the inlet towards a point of intersection in or adjacent an end of the throat a power supply arranged to be connected to the feedstock wires to cause an arc in the throat between the wires; and a supply of compressed air arranged to supply air to the throat, wherein the nozzle is formed from first and second body halves, each defining a portion of the throat.
2. Thermal spraying apparatus according to claim 1 wherein the guides are arranged to direct the feedstock wires to the point of intersection so that they define an angle of between 45° and 90° between them.
3. Thermal spraying apparatus according to claim 1 or claim 2 wherein the guides comprise respective bores formed in the body halves and each intersecting the portion of the body half defining a respective portion of the throat, each bore being inclined relative to the axis of the throat.
4. Thermal spraying apparatus according to claim 3 wherein the guides include inserts receivable in the respective bores, each insert having an aperture therein through which a feedstock wire can pass, and having an inclined end face shaped complementally to the shape of the throat.
5. Thermal spraying apparatus according to claim 3 wherein the respective bores intersect locating cavities, inserts being receivable in the locating cavities so that they abut feedstock wires passing through the respective bores.
6. Thermal spraying apparatus according to claim 5 wherein the inserts are polygonal in section and define planar faces each having a locating formation for engagement with a feedstock wire in use.
7. Thermal spraying apparatus according to claim 6 wherein the inserts are square in section and define planar, rectangular faces with a groove formed in at least one face for engagement with a feedstock wire in use.
8. Thermal spraying apparatus according to any one of claims 4 to 7 wherein the inserts comprise copper or copper/tungsten.
9. Thermal spraying apparatus according to any one of claims 1 to 8 wherein the body halves are conductive, with a terminal or contact on each body half for connection to the power supply.
10. Thermal spraying apparatus according to claim 9 wherein the body halves are mounted on a non-conductive head which holds the body halves in a spaced-apart condition.
11. Thermal spraying apparatus according to any one of the preceding claims wherein the throat is rectangular in cross section.
CA002379902A 1999-07-29 2000-07-27 Thermal spraying equipment Abandoned CA2379902A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
ZA99/4887 1999-07-29
ZA994887 1999-07-29
PCT/IB2000/001048 WO2001008810A1 (en) 1999-07-29 2000-07-27 Thermal spraying equipment

Publications (1)

Publication Number Publication Date
CA2379902A1 true CA2379902A1 (en) 2001-02-08

Family

ID=25587832

Family Applications (1)

Application Number Title Priority Date Filing Date
CA002379902A Abandoned CA2379902A1 (en) 1999-07-29 2000-07-27 Thermal spraying equipment

Country Status (6)

Country Link
EP (1) EP1210180A1 (en)
JP (1) JP2003505599A (en)
CN (1) CN1153629C (en)
AU (1) AU5840600A (en)
CA (1) CA2379902A1 (en)
WO (1) WO2001008810A1 (en)

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100540720C (en) 2003-06-06 2009-09-16 迈克尔·沃尔特·塞茨 The composite wire material and the using method that are used for coated substrate
US8518496B2 (en) 2003-06-06 2013-08-27 Alstom Technology Ltd Preventing tube failure in boilers
JP2007107082A (en) * 2005-10-17 2007-04-26 Kurimoto Ltd Arc spraying apparatus
CN101538697B (en) * 2008-03-20 2013-04-10 林淑清 Spray coating method through non-burning smelting spray
DE102013200067A1 (en) 2013-01-04 2014-07-10 Ford-Werke Gmbh Device for thermally coating a surface
CN103263989B (en) * 2013-05-15 2015-10-21 北京意如诚科技发展有限公司 A kind of supersonic electric arc spray gun
CN104307797A (en) * 2014-09-20 2015-01-28 张家港市胜达钢绳有限公司 Device for removing liquid on surface of steel wire
US10604830B2 (en) 2016-06-06 2020-03-31 Comau Llc Wire guides for plasma transferred wire arc processes
US20180002801A1 (en) 2016-06-29 2018-01-04 General Electric Technology Gmbh Composite wires for coating substrates and methods of use
WO2023076400A1 (en) * 2021-10-28 2023-05-04 Integrated Global Services, Inc. Apparatus and system for thermal spray and related methods thereof

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1130352A (en) * 1954-11-06 1957-02-05 Arnold Otto Meyer Metallization gun operated by an electric are
EP0907760B1 (en) 1996-06-28 2000-05-03 Metalspray International LC Thermal spraying method and apparatus

Also Published As

Publication number Publication date
EP1210180A1 (en) 2002-06-05
AU5840600A (en) 2001-02-19
WO2001008810A1 (en) 2001-02-08
CN1153629C (en) 2004-06-16
CN1371307A (en) 2002-09-25
JP2003505599A (en) 2003-02-12

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