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

Definitions

• the present invention relates to a method for applying at least one adherent layer on at least one object made of aluminum-silicon casting.
• Articles made of aluminum-silicon casting are coated with a firmly adhering layer in many areas of industrial production, this layer serving, for example, as wear protection, as corrosion protection, for surface finishing, for improving electrical and thermal conductivity or for electrical and thermal insulation.
• the layer is thermally sprayed onto the object to be coated.
• Known methods for applying layers or coatings of various types by means of thermal spraying on aluminum-silicon casting materials are, for example, plasma spraying, arc spraying or flame spraying, such as, for example, high-speed flame spraying.
• Another disadvantage of the coating by means of thermal spraying method is the fact that the surface of the object to be coated pretreated before applying the layer, for example by blasting, such as by blasting or by irradiation, roughened with corundum, in order to ensure sufficient adhesion applied layer on the object to reach.
• blasting such as by blasting or by irradiation
• corundum roughened with corundum
• an aluminum-silicon alloy is applied by arc spraying with wire.
• the layer thus applied has already been applied and fulfills the required technical properties.
• a high proportion of fine dust, a so-called overspray is produced. This one does not adhere to the component. Normally, the overspray is collected by an exhaust system and separated.
• cold gas spraying in which the spray particles are accelerated to high speeds in a "cold" carrier gas.
• the coating is formed by the impact of the particles on the workpiece with high kinetic energy.
• the particles that do not melt in the "cold” carrier gas form a dense and adherent layer, with plastic deformation and resultant local heat release providing cohesion and adhesion of the sprayed layer to the workpiece. Oxidation and / or phase transformations of the coating material can thus be largely avoided.
• the spray particles are added as a powder, the powder used usually has a particle size of 1 micron to 100 microns. However, it is also possible to use powders with significantly larger particles.
• the high kinetic energy obtained the spray particles in the relaxation of the carrier gas. After the injection of the spray particles into the gas jet, the gas is expanded in a nozzle, whereby gas and spray particles are accelerated to speeds above the speed of sound.
• the nozzle used in cold gas spraying is usually a de Laval nozzle or Laval nozzle.
• the carrier gas is expanded together with the spray particles in the Laval nozzle. While the pressure in the Laval nozzle drops, the carrier gas velocity increases to values up to 3,000 meters per second and the particle velocity to values up to 1,400 meters per second.
• Laval nozzles consist of a convergent and a downstream divergent section.
• the carrier gas used is usually nitrogen, but argon, helium and mixtures of these three gases are also used.
• the final velocity of the spray particles which depends on the nozzle, the material of the spray particles, the temperature of the spray particles and the type of carrier gas, is at least 500 meters per second in almost all cases; however, it usually reaches more than 650 meters per second and often even more than 800 meters per second.
• the present invention has the object, a method of the type mentioned in such a way that the emergence of attributable to the application of the layer cracks in the article to be coated is prevented ,
• the present invention is thus based on the essential property of cold gas spraying that no appreciable heat is introduced into the article during coating.
• the base material of the article remains unaffected, and the occurrence of defects or cracks attributable to local heat supply is prevented.
• the coating method according to the invention further offers the advantage that the surface of the article for the coating does not have to be pretreated. For example, in particular in the light metal sector, the operation of surface pretreatment by blasting is eliminated, which leads to a cost reduction and to a simplification of the coating process.
• the use of the cold gas spraying method thus results in that the surface of the object to be coated, for example the surface of the engine block to be coated, is not subject to any thermal stress and, as a result, there is no melting of spray particles and substrate; this allows the abandonment of a pretreatment of the surface; Rather, a homogeneous and stable coating of the workpiece is formed by the cold gas spray particles impinge with high kinetic energy on the surface of the workpiece.
• Another advantage of the present invention is therefore that the same or a very similar material can be selected for the cold gas spray particles from which the cast article consists. By the cold gas spraying thus creates a compound of the same or similar materials, which metallurgical problems are avoided.
• a cast aluminum-silicon article for example an aluminum-silicon cast engine block
• the coated article and / or the coated engine block can then be used as a qualitatively flawless component.
• the cold gas spray particles form a homogeneous layer upon impact with the article due to their high kinetic energy.
• the applied layer is thus as good as free of pores and very dense. It is advantageous to use cold gas spray particles having a size of from about 1 micron to about 300 microns, preferably to about 100 microns, most preferably to about 50 microns. With spray particles of this size, a particularly homogeneous layer is produced, which can be applied very precisely.
• Another advantage of the present invention is the low oxide content of the layer applied by cold gas spraying; the oxide content corresponds only to that of the starting powder of the spray particles.
• AlSi17 castings are coated.
• the aluminum-silicon casting of the article thus advantageously has an aluminum content of 83% by weight (wt .-%) and a silicon content of 17 wt .-%.
• Motor blocks are particularly advantageously coated with the method according to the invention.
• the method according to the invention it is thus possible to coat engine blocks made of aluminum-silicon casting in a very simple manner with at least one layer produced by cold gas spraying, wherein the layer may be at least one intermediate layer.
• the method according to the invention it is also possible to coat other components made of aluminum-silicon casting in an advantageous manner, such as radiator parts and suspension components, such as axle, and heat exchangers.
• the present invention further relates to an engine block of an aluminum-silicon alloy, in particular of aluminum-silicon casting, for example with an aluminum content of 83 weight percent (wt .-%) and with a silicon content of 17 wt .-% (so-called AlSi17), with at least one firmly adhering layer applied by means of cold gas spraying, in particular by means of the method set forth above, for example with at least one firmly adhering intermediate layer applied by means of cold gas spraying, in particular by means of the method set forth above.
• the adhesive mechanism of the layer is a plastic deformation-based clamping, a thermal load of the engine block is eliminated. Since engine blocks are exposed to very high loads, the coatings must be very resilient. The applied by means of cold spraying layer has this property in an excellent manner. Furthermore, no defects or stresses attributable to thermal stress during the coating are also found in the coated engine block.
• the layer and the engine block are made of the same or at least one material of the same type, then no metallurgical problems arise during use during the entire operating time of the engine block. Consequently, it is advantageous if the layer is also made of an aluminum-silicon alloy. A layer of aluminum or another aluminum alloy is also possible.
• the present invention relates to an internal combustion engine with at least one engine block according to the kind set forth above.

Landscapes

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

Applications Claiming Priority (1)

Publications (1)

Family

ID=37496594

Family Applications (1)

Country Status (2)

Cited By (5)

Families Citing this family (3)

Citations (4)

• 2006
  • 2006-07-11 DE DE200610032110 patent/DE102006032110A1/de not_active Withdrawn
  • 2006-11-02 EP EP06022875A patent/EP1878813A1/fr not_active Withdrawn

Patent Citations (4)

Non-Patent Citations (4)

Also Published As

Similar Documents

Legal Events