Abstract: A deposited film forming method and apparatus includes a belt-like member continuously conveyed through a film-forming chamber, one side of which is formed of the belt-like member. A reactive gas is introduced into the film-forming chamber, the interior of the film-forming chamber is evacuated, a high-frequency power induces a plasma therein, and a deposited film is formed on the belt-like member A discharge confining means is provided opposite to a deposited film forming side of the belt-like member to maintain constant contact with the belt-like member while it changes shape.

Abstract: The present invention provides a plasma transferred wire arc torch assembly that includes a monolithic block assembly that combines into a single component several features that have previously been separate components. The monolithic block of the present invention combines the functions of a wire guide, an air baffle, and a nozzle. Integration of this components allows for a reduction in size of the plasma transferred wire arc torch assembly thereby making it possible to coat smaller diameter bores with metal.

Abstract: A thermal spraying system includes thermal spray material, an electrical energy thermal spraying device atomizing and spraying the thermal spray material, a power supply supplying electrical power to the spraying device, a sensor monitoring a power characteristic of the supplied electrical power, and a feed rate control module adjusting a feed rate of the thermal spray material based on the monitored power characteristic.

Abstract: An induction plasma torch comprises a tubular torch body, a gas distributor head located at the proximal end of the torch body for supplying at least one gaseous substance into the chamber within the torch body, a higher frequency power supply connected to a first induction coil mounted coaxial to the tubular torch body, a lower frequency solid state power supply connected to a plurality of second induction coils mounted coaxial to the tubular torch body between the first induction coil and the distal end of this torch body. The first induction coil provides the inductive energy necessary to ignite the gaseous substance to form a plasma. The second induction coils provide the working energy necessary to operate the plasma torch. The second induction coils can be connected to the solid state power supply in series and/or in parallel to match the impedance of this solid state power supply.

Abstract: A method for plasma jet welding by means of a free radio frequency-induced plasma beam wherein, the rf-induced plasma beam is generated by a procedure involving a second process gas into a tube so that it has a tangential flow component and the introduction of the plasma through a metal expansion jet at the outlet.

Abstract: An ion fusion formation (IFF) system uses a plasma welding torch to create ions that heat feedstock for application at a deposition point. A plasma welding torch may use argon gas or the like in order to provide extremely hot ions that impact or collide with the feedstock in order to melt it and enabling application of the melted feedstock to a deposition point on a workpiece. By positioning the workpiece, wire feeder, and/or welding torch, parts, devices, or components can be built in almost any three-dimensional shape. Parts can be manufactured in a “just-in-time fashion” with high precision and predictable performance.

Abstract: A plasma processing system is comprised of a reaction vessel in which are provided a parallel high frequency electrode and ground electrode. The ground electrode is fixed at a ground potential portion, that is, a flange, by a conductive support column. A connection portion from the ground electrode to the ground potential portion, for example, the portions other than the surface of the ground electrode and the surface of the support column etc. are covered by an insulator serving as a high frequency power propagator while the surface of the insulator is covered completely by a conductive member except at the portion for introducing the high frequency power. In this plasma processing system, it is possible to reliably prevent undesirable discharge from occurring at the rear surface of the ground electrode when processing a substrate mounted on the ground electrode to deposit a film using a high frequency power in the VHF band.

Abstract: A torch head includes a torch body which is inserted into the tube member, a cathode tube which is arranged in the torch body such that the longitudinal axis of the cathode tube is aligned to the longitudinal axis of the torch body and which has a cathode at the distal end of the cathode tube, an anode member which is arranged on the distal end side of the cathode tube, and a spraying material supply tube which opens toward a mouth opening formed in the anode member and which is arranged outside the torch body. In the anode member, a plasma gas supply chamber in which the front end of the cathode tube is stored in a non-contact state, an orifice which communicates with the plasma gas supply chamber and in which the cathode is stored in a non-contact state, and a plasma generation chamber which communicates with the orifice, which has a longitudinal axis substantially perpendicular to the longitudinal axis of the torch body, and which has the mouth opening are formed.

Abstract: An aluminum pressure plate and flywheel, for a clutch in a vehicle drivetrain, have wear resistant surfaces applied at the clutch disc interface. The wear resistant surfaces are applied to the pressure plate and flywheel using a plasma transferred wire arc thermal spray process.

Abstract: A method of producing nanocrystalline ceramic powder by creating a plasma stream in a reactor vessel, and physically converting a ceramic precursor material into ceramic particles suspended in the vessel, using the plasma stream. A metallic reactant may additionally be introduced into the vessel using the plasma stream, wherein the metallic reactant forms ceramic particles having the same composition as the ceramic particles of the physical converting step. The plasma stream is created using an electrothermal gun. The gun may use a ceramic barrel which is eroded by the plasma stream. Alternatively (or additionally), the ceramic precursor material may be injected as particulates into the plasma stream, wherein the ceramic precursor particulates are micron-sized or larger. A novel electrothermal gun design may optionally use a replaceable insert constructed of the ceramic precursor material.

Abstract: The invention recites a plasma-arc spray gun comprising a cathode and an anode defining a longitudinal axis. The anode further includes an external surface and an internal chamber, the internal chamber extending from a first end to a second end. At least a portion of the internal chamber is defined by revolving a non-linear curve about the longitudinal axis. The plasma-arc spray gun also includes a gun body supporting the cathode and the anode.

Abstract: A torch for powder plasma buildup welding capable of readily attaining welding in conformity to any size of a pipe material to be subjected to welding, any configuration thereof and the like. A torch head is replaceably connected to a torch body. The torch body is provided with a gap formation spacer member which is abutted against an inner peripheral surface of the pipe material to keep a distance between an opening of a convergent nozzle of the torch head and the inner peripheral surface of the pipe material substantially constant during buildup welding. Also, the torch body is provided with a deflection restraint spacer member which is abutted against the inner peripheral surface of the pipe material to prevent deflection of the torch body in the pipe material during buildup welding.

Abstract: A method for the production of a heater element on a target area. A plurality of particles having a specified size range are prepared. The plurality of particles include a metallic alloy, and the metallic alloy includes boron. The particles are applied to the target area using at least one of a plasma spray process and a flame spray process.

Abstract: A system for fine feature spray deposition includes a substrate platform for supporting a substrate on which the features are to be deposited. A spray assembly is provided which includes a spray source for providing a stream of material to be deposited on a substrate, a collimator which is positioned in a path of the stream from said spray source and an aperture assembly, which is positioned downstream of the collimator with respect to the spray source and above the substrate platform. The aperture assembly defines at least one opening to pass a portion of the stream of material onto a surface of the substrate. A drive mechanism is provided which is coupled to at least one of the spray assembly and the substrate platform for inducing relative motion there between. A controller is coupled to the spray assembly and the drive mechanism to control the relative motion and the stream of material. The system allows fine features to be printed directly on a substrate with requiring a predefined mask.

Abstract: A method and system for producing a transparent, electrically conductive coating onto a substrate. The method includes: (a) operating a twin-wire arc nozzle to heat and at least partially vaporize two wires of a metal composition for providing a stream of nanometer-sized vapor clusters of the metal composition into a chamber in which the substrate is disposed; (b) introducing a stream of oxygen-containing gas into the chamber to impinge upon the stream of metal vapor clusters and exothermically react therewith to produce substantially nanometer-sized metal oxide clusters; and (c) directing the metal oxide clusters to deposit onto the substrate for forming the coating.

Abstract: A cathode assembly 10 for an electric arc spray apparatus. The cathode assembly 10 utilizes a positive cathode retention design which provides for improved heat management characteristics, quick and easy cathode replacement and increased cathode life. The cathode assembly includes a cathode holder 14, a cathode 12 including a first portion 26 which resides within the cathode holder 14, a tip portion 28 which extends from the cathode holder, and a shoulder portion 33 which is formed on the outer surface of the cathode. The cathode assembly 10 further includes a retention member or nut 16 which removably attaches to the cathode holder 14 and which engages the shoulder portion 33, effective to positively retain the cathode 12 within the holder 14. The retention member 14 also includes an aperture through which the cathode tip 28 extends.

Abstract: A torch head includes a torch body which is inserted into the tube member, a cathode tube which is arranged in the torch body such that the longitudinal axis of the cathode tube is aligned to the longitudinal axis of the torch body and which has a cathode at the distal end of the cathode tube, an anode member which is arranged on the distal end side of the cathode tube, and a spraying material supply tube which opens toward a mouth opening formed in the anode member and which is arranged outside the torch body. In the anode member, a plasma gas supply chamber in which the front end of the cathode tube is stored in a non-contact state, an orifice which communicates with the plasma gas supply chamber and in which the cathode is stored in a non-contact state, and a plasma generation chamber which communicates with the orifice, which has a longitudinal axis substantially perpendicular to the longitudinal axis of the torch body, and which has the mouth opening are formed.

Abstract: A method for closing and/or joining a connecting joint or joining seam between two pieces of galvanized sheet metal, in which zinc or a zinc alloy whose melting point is similar to that of zinc is heated to melting temperature and is continuously introduced into the connecting joint, with the heating being performed by a plasma jet without reaching the melting temperature of the steel sheet. The use of a plasma jet allows processing zinc or, a zinc alloy without producing any disturbing zinc spatter. The zinc can be supplied as a wire, powder or granulate, whereby it is introduced under an inert-gas bell. This method can also be employed for post-galvanizing weld seams, with a second plasma jet welding set following a first one, it being mechanically coupled with the same and performing the galvanizing of the weld seam by the supply of zinc in wire form without melting the steel sheet anew. Tin foils are used in a special embodiment which are applied in the joining zone of a flanged edge.

Abstract: A thermal spray or welding apparatus including a cored wire electrode with a sheath and a multiplex powder composite. The composite comprises micron-sized particles and sub-micron sized particles, including nano-scale particles, the particles mechanically cooperating to promote smooth powder flow, which facilitates compaction of the cored wire electrode. The invention also includes a method of manufacture of the apparatus including the cored wire electrode and its method of use to deposit a low porosity coating with high levels of alloyed refractory elements that is adherent and low in oxide content.

Abstract: A method for surface working a tribological coating of a supereutectic aluminum-silicon alloy or an aluminum-silicon composite material with a coating structure includes machining the surface dry, without lubricant, in a one-step process, with a cutting tool having a cutting material containing diamond. The surface treating may be followed by a one-step finish honing or one-step texturing process.

Abstract: A shroud for a welding torch includes a hydrophilic skirt supported by a frame. The skirt is soft and pliable when wet and is self protected from the heat of welding by the water absorbed therein. The frame supports the skirt around the weld site and permits a good seal with the workpiece for excluding water during the welding process.

Abstract: In a system based on aluminum, zirconium and nitrogen at least one layer has covalent bonds of aluminum nitride or at least one layer has bonds of the aluminum nitride and zirconium nitride type. In a process for producing such a system an electrical gas discharge is fired in a vacuum chamber such as essentially to form a noble gas-enriched plasma resulting in ionization of the metal elements. To form the nitridic layer nitrogen is continuously fed as a reactive gas into the vacuum chamber and pumped away so as to set a reactive gas partial pressure which is used for process control purposes. The use of such a system for producing a coating on a surface is also described.

Abstract: A shroud for a welding torch includes a hydrophilic skirt supported by a frame. The skirt is soft and pliable when wet and is self protected from the heat of welding by the water absorbed therein. The frame supports the skirt around the weld site and permits a good seal with the workpiece for excluding water during the welding process.

Abstract: An ion fusion formation (IFF) system uses a plasma welding torch to create ions that heat feedstock for application at a deposition point. A plasma welding torch may use argon gas or the like in order to provide extremely hot ions that impact or collide with the feedstock in order to melt it and enabling application of the melted feedstock to a deposition point on a workpiece. By positioning the workpiece, wire feeder, and/or welding torch, parts, devices, or components can be built in almost any three-dimensional shape. Parts can be manufactured in a “just-in-time fashion” with high precision and predictable performance.

Abstract: An electrode for a plasma arc torch and method of fabricating the same are disclosed, wherein the electrode comprises a metallic holder defining a cavity in a forward end. An emissive element and separator assembly is positioned in the cavity. The emissive element has a layer of relatively non-emissive material on the outer surface thereof, which is preferably applied by heating the emissive element to a high temperature such that the emissive element becomes reactive, and spraying the relatively non-emissive material on the emissive element. The coated emissive element is positioned in the separator and the assembly is heated such that the relatively non-emissive material forms a strong bond between with the separator. The superior bonds between the emissive element and separator formed according to the present invention extend the life span of the electrode.

Abstract: A method of producing nanocrystalline ceramic powder by creating a plasma stream in a reactor vessel, and physically converting a ceramic precursor material into ceramic particles suspended in the vessel, using the plasma stream. A metallic reactant may additionally be introduced into the vessel using the plasma stream, wherein the metallic reactant forms ceramic particles having the same composition as the ceramic particles of the physical converting step. The plasma stream is created using an electrothermal gun. The gun may use a ceramic barrel which is eroded by the plasma stream. Alternatively (or additionally), the ceramic precursor material may be injected as particulates into the plasma stream, wherein the ceramic precursor particulates are micron-sized or larger. A novel electrothermal gun design may optionally use a replaceable insert constructed of the ceramic precursor material.

Abstract: A cathode assembly 10 for an electric arc spray apparatus. The cathode assembly 10 utilizes a positive cathode retention design which provides for improved heat management characteristics, quick and easy cathode replacement and increased cathode life. The cathode assembly includes a cathode holder 14, a cathode 12 including a first portion 26 which resides within the cathode holder 14, a tip portion 28 which extends from the cathode holder, and a shoulder portion 33 which is formed on the outer surface of the cathode. The cathode assembly 10 further includes a retention member or nut 16 which removably attaches to the cathode holder 14 and which engages the shoulder portion 33, effective to positively retain the cathode 12 within the holder 14. The retention member 14 also includes an aperture through which the cathode tip 28 extends.

Abstract: Magnetic modules and a process for manufacturing magnetic modules are provided wherein magnetic material is deposited into one or more cavities patterned into a non-magnetic substrate die to form a plurality of magnetic cores. The patterned substrate board, which may be a composite of graphite, a composite of alumina or other non-magnetic ceramic, provides a surface for winding windows, inductor air gaps, isolations, and a mounting surface for other system components.

Abstract: The invention relates to an apparatus for coating a substrate with a plasma arc torch, and with such a plasma arc torch the powdery additive is to be heated, melted open and accelerated towards the surface with plasma gas generated in the plasma arc torch, and with an additional laser beam. In the plasma arc torch, an annular cathode is located or a plurality of individual cathodes are arranged about a longitudinal axis. Gas is supplied into a plasma space which is located between such an annular cathode or the plurality of cathodes, and such an annular anode. With the invention, coating is to be allowed to be formed with a higher speed and deposition rate, respectively, with respect to the conventional solution with the same and increased quality, respectively, and the directional independence for the formation of the coating is to be ensured.

Abstract: A cutting edge is formed by build-up welding on a die of a die assembly made of a base material of an aluminum/copper-based zinc alloy. The cutting edge comprises an underlying layer and an overlying layer. The underlying layer is made of a copper alloy that can be welded to both a zinc alloy and a nickel alloy, and the overlying layer is made of a nickel alloy. The cutting edge is of high machinability, high durability, and high hardness.

Abstract: A powder feed nozzle for laser welding applications including a multiple outlet nozzle tip for focusing a discharged powder stream. The multiple outlet nozzle tip disperses multiple outlet streams and includes a powder discharge outlet and at least one focus gas discharge outlet, radially spaced from the powder discharge outlet, for dispersing a powder stream and a gas stream. Powder flows from a powder source through a powder channel to discharge a powder stream. Focus gas flows through a focus gas channel angled relative to the powder channel to discharge a focus gas stream.

Abstract: A feedstock injector for connection to a source of heated gas comprises a first plurality of channels arranged symmetrically about a longitudinal axis, the channels leading from the upstream end to an intermediate region of the injector. A second plurality of channels, coaxial with the first plurality of channels and arranged symmetrically about the same longitudinal axis, extend from the outlet ends of the first plurality of channels towards the downstream end of the injector and converge at a convergence angle towards a common region of convergence located downstream on the longitudinal axis. Feedstock material is injected axially towards the common region of convergence.

Abstract: An automated hardfacing system useful for hardfacing roller cones is disclosed. The automated system includes a robot with an arm, a positioner, and a controller which co-ordinates the alignment of the robot and the positioner. The robot holds a hardfacing torch and is capable of movement in three axes of movement. These axes are the x, y, and z axes of the Cartesian co-ordinate system. The positioner holds a roller cone and is capable of movement in at least two axes of movement. The movement includes tilting and rotation about a Cartesian axis. The hardfacing coating produced by the automated system has improved quality and consistency as compared to the one obtained by a manual process.

Abstract: The multi-layered heat resistant metal tube is disclosed. This tube has excellent anti-coking characteristics and is suitable for use under the conditions where carbon tends to deposit and accumulate thereon due to contacting with hydrocarbons at a high temperature. The tube is made by forming weld-mounted overlaid layer of Cr—Ni alloy by building-up welding over the inner surface and/or the outer surface of a substrate tube made of a heat resistant metal. The Cr—Ni alloy comprises 35% by weight or more of Cr and satisfies the relationship: Ni(w%)≧0.5Cr(wt %). Building-up welding is preferably carried out by PPW (Plasma Powder Welding) in which the filler metal is supplied in the form of powder.

Abstract: A multi-layered heat resistant metal tube is disclosed. This tube has excellent anti-coking characteristics and is suitable for use under the conditions where carbon tends to deposit and accumulate thereon due to contacting with hydrocarbons at a high temperature. The tube is made by forming weld-mounted overlaid layer of a Cr—Ni—Mo alloy by building-up welding over the inner surface and/or the outer surface of a substrate tube made of a heat resistant metal. The Cr—Ni—Mo alloy consists essentially of, by weight %, Cr: 36-49 wt %, Ni: 35-63 wt % and Mo: 0.5-5 wt %. Building-up welding is preferably carried out by PPW (Plasma Powder Welding) in which the filler metal is supplied in the form of powder.

Abstract: Powder aerosols are introduced into a gas stream in metered form and without any aggregates. To this end, according to the invention, a powder is drawn, for example by mechanical device, from a reservoir area and is converted into a powder aerosol which is introduced within a flowing gas stream into a container to which ultrasound is applied. The ultrasound breaks down powder lumps and aggregates, and the aerosol can be fed in a uniform, fine powder distribution within the gas stream to a plasma burner. Apparatus for carrying out this invention includes a feed tube (4) connected to a mechanical powder feed device (6), so that an aerosol containing the powder enters a vessel (10) containing the ultrasound horn (2). The method and the associated apparatus are used for the coating of components, preferably for applying a protective coating to a turbine blade.

Abstract: A modular system for constructing an atmospheric pressure plasma source. A plasma torch module may be constructed by reassembling the structural components of two (2) different models of spark plugs. Each module can produce a plasma torch having a radius of about 1 cm or more, a height of about 6 cm, and a peak density exceeding 1013 cm−3. A set of modules, each connected in series, may be used with a ballasting capacitor such that an array can be operated while sharing a common power supply to produce a plasma having a relatively large volume and a relatively high density. A system having a number of plasma torch modules may be used in applications for absorbing radiation, reducing air drag and igniting fuel.

Abstract: A radial bearing and method for making the same are disclosed. Radial bearings are typically used control the direction of drilling in directional drilling operations. The cuttings flow across the surfaces of the bearings before being removed from the well. The cuttings will contain sand and other hard and/or corrosive substances that will erode the surfaces of the bearings and shorten their useful life. The bearing of this invention is provided with a wear resistant surface to inhibit such erosion. The bearing is made from a bearing blank to which is applied a first overlay of mild steel with dispersed cemented metal carbide pellets. The composition of the cemented metal carbide pellets is disclosed. The first overlay may be applied by any conventional technique. A second overlay of mild steel is applied to the first overlay utilizing a MIG welding process. As the second overlay is applied, a portion of the hard metal particles in the first overlay is dispersed in the weld puddle forming the second overlay.

Abstract: A material in powder or wire form on a nickel basis for the production of a coating with a high level of resistance to corrosion and wear by means of a thermal coating process is of the following composition (in percent by weight): C 0.005-1.0;  Cr 10.0-26.0; Mo  8.0-20.0; Fe  0.1-10.0; Si 3.0-7.0; B 1.0-4.0; Cu 0.1-5.0; Ni Balance. The material in powder form can be alloyed and sprayed out of the melt or agglomerated out of different alloyed and non-alloyed metal powders. The coating material can also be used in the form of a filling wire or an alloyed and cast bar material.

Abstract: A machine tool or die that is fabricated from thermally spray-formed steel is repaired on the factory floor by first cleaning the area to be repaired to removed all dirt and impurities. Next the surface is prepared by means of preheating the surface with propane torches at a rate not exceeding 50° Centigrade per hour to boil off the moisture in the tool. The weldment is formed by the TIG welding process and then finished by conventional machining, grinding and polishing.

Abstract: The present invention relates to a method for the surface working of a tribological coating of a supereutectic aluminum-silicon alloy or an aluminum-silicon composite material with a coating structure, wherein the surface is reworked after the production of the coating. Provision is made according to the invention that the surface is machined dry, without lubricant, in a one-step process, a cutting tool with a cutting material containing diamond being used. This can be followed by an additional working process. Preferably a combination process of dry machining and one-step finish honing or one-step texturing by radiation is provided.

Abstract: An apparatus for fabricating a semiconductor device includes: a plasma torch having a hollow convey tube of which one end portion is made of a conductor so as to serve as an inner electrode, for injecting plasma generating gas through one end portion, conveying and spraying a plasma frame through the other end portion; an energy applying unit for applying a microwave to the gas conveyed through the convey tube and adds an energy thereto; an outer electrode for surrounding the other end portion of the convey tube and its extended portion coaxially; an insulation tube positioned between the convey tube and the outer electrode for electrically insulating the other end portion of the convey tube and the outer electrode and surrounding partially the convey tube coaxially; a power source for applying a voltage to the inner electrode and the outer electrode; a suscepter installed facing the plasma frame sprayed from the plasma torch; a suscepter moving unit for moving the suscepter in the vertical and horizontal dir

Abstract: A plasma arc torch includes a housing having a nozzle at one end with a central orifice. An electrode extends into the orifice for producing a plasma arc. A port is disposed in the nozzle adjacent the orifice for injecting powder into the arc. The port includes an outlet, an inlet, and a reniform manifold extending therebetween for laterally distributing the powder about the nozzle orifice. In this way, the powder may be carried to the torch underwater and is distributed circumferentially about the plasma arc while simultaneously diffusing its carrier gas.

Abstract: A plasmagenic gas comprises a ternary mixture of helium, argon and hydrogen. The gas contains less than 30% helium, at least 55% argon, and from 5.5 to 15% hydrogen. The gas is energized to form a plasma. A powder of a refractory or metallic material is introduced into the plasma.

Abstract: A process for post processing a part that has a Nitinol coating applied by plasma spraying or PVD coating gives the Nitinol desirable properties of toughness and malleability. It also produces a layer of surface material that is extremely hard, chemically non-reactive, electrically and thermally insulating. The process includes selecting a part that has a surface coating of Nitinol applied by plasma spraying or PVD coating and polishing the surface coating to give it a smooth and shiny surface. The polished surface is then cleaned to remove all polishing residue. The surface of the Nitinol coating is heated a temperature in a range of about 400° C. to 900° C.; and is rapidly cooled by forced air flow over the surface coating or by low temperature air or liquid immersion. Thereafter, the outer surfaces of the layer of surface material may be repolished and reheated as before to enhance the layer of thermally produced surface material.

Abstract: A nozzle-injector was designed and fabricated for plasma deposition of thin-film coatings using a wall-stabilized arc torch as the plasma generator. The design of the nozzle-injector controls the injection, ionization, and reaction of the reagents, and these functions, in turn, determine the coating deposition rate, coating area, coating composition, and coating quality.

Abstract: The plasma torch has a cathode supporter having a front end and a rear end, mounted on the body at the rear end thereof; a button-cathode for generating plasma arc, which is assembled to the front end of the cathode supporter; a hollow-cathode having an inner surface and an outer surface, surrounding the button-cathode, the inner surface of which is spaced from the button-cathode, being assembled to the cathode supporter, and being made of material with higher work function than material for the button-cathode. The plasma gas flows along the outer surface to accomplish low gas pressure between the inner surface of the hollow-cathode and the button-cathode. A multiple-solenoid coil is adapted to rotate arc root around the button-cathode and to move arc root axially along the surface of the button-cathode.

Abstract: The invention concerns an inductive plasma torch comprising an external tube, an intermediate tube and a central injector (16) including at least a central tube (20, 21) injecting reagent and a peripheral sheathing tube (22). A gas similar to plasma gas is injected into the space between the central tube (20, 21) and the sheathing tube (22), in conditions suited for obtaining a laminar flow, said flow remaining laminar up to the plasma torch central zone. The sheathing tube emerges substantially at the first turn of the inductor coil.