Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C24/00—Coating starting from inorganic powder
  • C23C24/02—Coating starting from inorganic powder by application of pressure only
  • C23C24/04—Impact or kinetic deposition of particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
  • B05B7/16—Spraying 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
  • B05B7/1606—Spraying 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 the spraying of the material involving the use of an atomising fluid, e.g. air
  • B05B7/1613—Spraying 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 the spraying of the material involving the use of an atomising fluid, e.g. air comprising means for heating the atomising fluid before mixing with the material to be sprayed
  • B05B7/162—Spraying 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 the spraying of the material involving the use of an atomising fluid, e.g. air comprising means for heating the atomising fluid before mixing with the material to be sprayed and heat being transferred from the atomising fluid to the material to be sprayed
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
  • B05B7/16—Spraying 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
  • B05B7/20—Spraying 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 by flame or combustion

Definitions

• the invention relates to a Laval nozzle for thermal spraying and kinetic Spraying, especially for cold gas spraying, with a converging and with a divergent section.
• Such nozzles are used in cold gas spraying used and used for the production of coatings or moldings.
• the spray particles are at relaxation of the gas jet in the divergent part of the Laval nozzle at high speeds above the speed of sound accelerated.
• the spray particles then strike the substrate and weld due to their high kinetic energy to a very dense layer.
• the nozzle but is suitable in addition to the cold gas spraying for the other methods of thermal spraying, such as flame spraying or the High-speed flame spraying with inert or reactive spray components.
• On impact with high Speed is formed by the particles that do not melt in the "cold" gas jet, a dense and firmly adherent layer, whereby plastic deformation and therefrom resulting local heat release for cohesion and adhesion of the sprayed layer take care of the workpiece.
• a heating of the gas jet increases the Flow velocity of the gas and thus the particle velocity. It also warms the particles, thereby favoring their plasticity Deformation on impact.
• the gas temperature can be up to 800 ° C, but is well below the melting temperature of the coating material, so that a Melting of the particles in the gas jet does not take place. An oxidation and Phase transformations of the coating material can thus be largely avoid.
• Nitrogen, helium, argon, air or mixtures thereof used mainly, however, comes Nitrogen for use, higher particle velocities are using helium or Helium-nitrogen mixtures achieved.
• the nozzle described there and currently has the shape of a double cone with a total length of about 100 mm. It has an expansion ratio of about 9, In addition, a variant with an expansion ratio of 6 is also used.
• the Length of the convergent section is about 1/3, that of the divergent section 2/3 of the nozzle length.
• the nozzle throat has a diameter of about 2.7 mm.
• devices for cold gas spraying are at pressures of from about 1 MPa up to a maximum pressure of 3.5 MPa and gas temperatures up to about 800 ° C.
• the heated gas is released together with the spray particles in the Laval nozzle.
• the gas velocity increases to values up to 3000 m / s and the particle velocity to values up to 2000 m / s.
• FIG. 2a has a cylindrical shape, that of FIG. 2b has a curvature towards the outside.
• “Curvature outwards” means that the line of the boundary in Figure 2b below in Flow direction of the gas has a curvature to the right, so outward.
• the Upper boundary line has a curvature to the left, so also after Outside.
• the cross-sectional areas of the nozzle grow when going outward faster than a corresponding cone.
• the object of the invention is to provide a nozzle for the thermal and the kinetic To improve spraying so that the application effect is increased and while the tendency of the particles to deposit on the nozzle wall is reduced.
• a nozzle in which the whole diverging section or at least part of the diverging section one having bell-shaped contour.
• a nozzle in which the whole diverging section or at least part of the diverging section one having bell-shaped contour.
• Such a nozzle the comparable dimensions we use the standard nozzle described above in terms of nozzle length, aspect ratio convergent to divergent section, expansion ratio, diameter of the Nozzle neck, etc., but according to the invention has a bell-shaped contour of the divergent nozzle section shows a much better order behavior.
• a standard nozzle and a bell-shaped nozzle resulted when using the same copper powder with grain size 5 to 25 microns and otherwise same process parameters with regard to gas pressure, gas temperature, gas flow, Pulveronneate, spray distance, etc. an increase in the order efficiency of 50 to 55% to 60 to 65%.
• Ordering efficiency refers to the amount of adhering powder the amount of powder sprayed per unit area during the same period.
• the whole divergent section is bell-shaped. It is enough but also out if only part of the divergent section has bell shape and the Rest is designed differently, for example as a cone or as a cylinder.
• the Beginning of the diverging section bell shape This then moves over One-third or one-half the length of the divergent section.
• the Go nozzle in another form, where it is favorable if the nozzle no Discontinuities or "kinks" in their course. Should be avoided abrupt transition from bell shape to cone or from cone to cylinder, since abrupt transitions disturb the uniformity of the gas flow.
• the bell-shaped contour is designed so that a Parallel jet nozzle is present, that is, the jet leaves the nozzle in parallel, without Expansion.
• This second variant of the invention with the same diameter in Nozzle neck, but a longer divergent section whose bell-shaped contour was designed so that a parallel gas flow is achieved, results in otherwise same process parameter even an order efficiency of 75 to 80%.
• the total length of the nozzle is between 60 and 300 mm, preferably using nozzles with overall lengths of 100 to 200 mm become.
• the cross section in the nozzle throat is 3 to 25 mm 2 , more preferably 5 to 10 mm 2 .
• nozzles in which the exit Mach number between 1 and 5, particularly favorably between 2.5 and 4 lies.
• the particle velocity depends on the type and state variables of the gas (Pressure, temperature), the particle size and the physical density of the Particle material (article by T. Stoltenhoff et al. HVOF Colloquium, 16 and 17.11.2000 in Erding, formula on page 31 below). thats why It is possible to customize the nozzle contour specifically on the process gases nitrogen, air and helium as well as the spray material.
• a powder tube is provided in the nozzle, which serves to supply the spray particles and ends in the divergent portion of the nozzle.
• Such powder tubes and nozzle geometries are shown in DE 101 26 100 A1, the disclosure of which is incorporated herein by reference.
• the divergent section of the nozzle always has at least one bell-shaped section.
• the contour is even better at nitrogen than process gas and copper was tuned as a spray material, an order efficiency of over 80% achieved.
• the optimization was then carried out by varying the nozzle contour and calculating the particle velocities achievable thereafter.
• the significant Increase of the order efficiency by the invention is due to that more or larger powder particles necessary for the adhesion of the particles Exceed minimum speed.
• the figure shows a modified scale, the inner contour of an inventive Laval nozzle, with the gas flowing from left to right.
• the converging section is conical in this embodiment along its entire length designed. In the diverging section one sees a steady decrease of the Increase, if one follows the upper boundary line from left to right and one steady increase of the slope, following the lower boundary.
• This bell shape is achieved so that the jet is practically parallel to the nozzle on the right side leaves and adverse effects such as compression shocks at the nozzle exit or pressure nodes in the free jet can be significantly reduced.
• the dimensions in mm are exemplary only and should not limit the scope of the invention.
• Bell shape means that from the taper, so from the neck of the nozzle konvexkonkaver Curve course takes place, wherein the flow-through cross section is always larger or at least stays the same, but never gets smaller.
• You can look at the curve also imagine: If you at the point (20 / 1,6) of the upper line of the figure a small Toy car sets up, whose front points to the right, so you would in the first Drive straight on, then make a left turn, to about the point (22 / 1.65). There is the turning point, from there the vehicle would turn right make a right turn until the end of the line at approx. (150 / 3,2), however, the steering angle of the steering becomes smaller and smaller.
• the first paragraph from 20 to 22 is the convex
• the larger section from 22 to 150 is the concave.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Nozzles (AREA)
• Coating By Spraying Or Casting (AREA)

Priority Applications (2)

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Publications (2)

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Cited By (5)

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Citations (5)

• 2004
  • 2004-04-29 PL PL04010236T patent/PL1506816T3/pl unknown
  • 2004-04-29 EP EP04010236A patent/EP1506816B1/fr not_active Revoked

Patent Citations (5)

Non-Patent Citations (1)

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