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
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
• • 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
  • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
  • C23C8/36—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases using ionised gases, e.g. ionitriding
  • C23C8/38—Treatment of ferrous surfaces
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/06—Surface hardening
  • C21D1/09—Surface hardening by direct application of electrical or wave energy; by particle radiation

Definitions

• the present invention relates to a method of surface treatment of steel products, of the type according to which said product is subjected to the action of a plasma generated in a rarefied gas atmosphere.
• the atmosphere consists of a rare gas, most often argon.
• the negatively polarized material attracts gaseous ions from the plasma, and ion bombardment has a pickling effect by removal of material, which leads to a high reactivity of the surface towards the atmosphere and an increase in the roughness.
• plasma surface treatment methods could be used to replace chemical treatment methods to provide the treated surfaces with the particular properties mentioned above.
• the present invention therefore relates to a plasma surface treatment process of the type indicated at the beginning of this thesis, this process being characterized in that the product to be treated is kept at low temperature, and the product is subjected to a treatment low plasma surface temperature, at a pressure of 1 to 103 Pa.
• low temperature plasma or "cold" plasma is generally meant a plasma obtained by glow discharge in a low pressure atmosphere (less than 103 Pa).
• the discharge is obtained at a voltage of several hundred volts, preferably a DC voltage and preferably still from 400 to 800 V, this voltage can in particular be applied between an anode and the negatively polarized metal product which serves as a cathode. It is also possible to superimpose on the direct voltage, a variable voltage at radio frequency.
• the current density is preferably less than 10 mA / cm2.
• the product to be treated is kept “cold", that is to say that its temperature is less than about 300 ° C.
• the temperature is generally maintained in the vicinity of the ambient temperature, below 100 ° C. This can be obtained by using a cooled cathode, for example by circulation of water.
• keeping it at a temperature close to room temperature can be ensured simply by sufficiently short treatment sequences in the treatment enclosure, and possibly supplemented by a cooling of the sheet supports, this being able to be more particularly adapted to the treatment of a moving sheet.
• a necessary condition is that the rise in temperature caused solely by the treatment (unlike certain known methods in which a plasma treatment is carried out on a product deliberately heated and brought to temperatures of several hundred ° C.) does not cause degradation of product characteristics.
• the duration of treatment is from one second to 10 minutes.
• the method according to the invention makes it possible to limit the action of the plasma treatment to a surface area of the material, and according to the nature of the gas or gases in which the plasma is generated, makes it possible for example to improve the aptitudes anticorrosion of the treated material, or adhesion to the surface thereof, by acting specifically on the causes that may affect the achievement and sustainability of these characteristics.
• the treatment is carried out by the action of a plasma at low temperature.
• a plasma in an atmosphere comprising at least one molecular gas chosen from oxygen, ozone, nitrogen, hydrogen, air, carbon dioxide, carbon monoxide, nitrogen oxides, water , combustion gases or mixtures thereof with a neutral gas, the product being kept at low temperature.
• the gas molecules Under the influence of the electric field, the gas molecules are dissociated, excited or ionized in the electric discharge thus created, a low energy plasma scans the surface of the material and the various gaseous species react with the surface atoms according to their chemical affinity .
• a large number of elements disappear from the treated surface.
• the surface After treatment, the surface is generally passive vis-à-vis the atmosphere, that is to say, conventional pollution elements C, S, P, O ...
• One of the most advantageous characteristics of a molecular plasma treatment according to the invention is to not practically not change the surface roughness of the material even on layers with low melting point. On the contrary, with rare gases, erosion is more important and can lead to a very high reactivity towards contaminants in the atmosphere.
• the gaseous atmosphere preferably comprises at least one gas chosen from hydrogen, nitrogen, chlorinated compounds and gases rare.
• the gaseous atmosphere does not contain oxygenated compounds.
• the method according to the invention makes it possible to eliminate these drawbacks and advantageously replaces chemical treatments in the preparation of products such as sheets, in particular galvanized sheets, intended to be subjected subsequently to phosphating or chromata treatments. tion, to be coated with lacquers, to be assembled by hot pressing with a polymer sheet, for example for the manufacture of "sandwich” sheets or to be assembled by gluing.
• Example 1 Surface treatment carried out on bare mild steel sheets
• the treatment was carried out under a direct voltage of 400 V, with an intensity of 200 mA, the spacing between the anode and the product (cathode) being 4 mm, the sample having a dimension of 70 x 120 mm.
• the phosphating tests in a hot bath carried out without prior alkaline degreasing have shown very good results for the N2-H2 and N2-H2 treatments followed by N2-O2: the phosphating is fine, homogeneous, in the form of small cubic blocks.
• the reference sample is simply degreased with chlorotene.
• the samples treated according to the invention underwent an N2-H2 plasma treatment for 4 min at 400 V and 200 mA.
• the bonding was carried out with a two-component epoxy adhesive polymerizing at room temperature (sold by CIBA GEIGY under the reference AW134).
• the bonded assemblies were then aged by exposure for 48 hours in a hot and humid atmosphere (65 ° C at 100% relative humidity).
• Example 2 Surface treatment performed on zinc-coated sheets (IFS galvanized steel sheets of monogal type treated on the zinc-coated side)
• the treatment was carried out under 400 V, and 200 mA the sample having the same dimensions as previously and the gases used being N2-H2 and N2-O2 respectively.
• the maximum deformation is increased by 55% after 9 min of treatment, in the non-aged state, and by 116% in the aged state.
• Example 3 Surface treatment carried out on galvanized steel sheets (of the type commonly referred to as "Galvadur")
• the sheets thus treated were all then covered with a polyester-type lacquer in two layers: 5 ⁇ m of thickness of primary layer, and 15 ⁇ m of thickness of finishing layer.
• the adhesion of the assembly thus produced is tested using the 3-point bending test before and after aging.
• the adhesive used for the 3-point bending test is a two-component epoxy adhesive polymerized for 60 min at 80 ° C.
• the maximum breaking strength (Fmax) decreases, compared to the un-aged state, by only about 20% for sheets having undergone a plasma treatment, against 50% for those having undergone the conventional cycle chromatography comprising an alkaline pickling.
• the treatment according to the invention generally makes it possible to improve the adhesion to the surface of the sheets thus treated, compared with conventional treatments by alkaline pickling in the case of phosphating or subsequent chromating, or with simple cleaning and degreasing. used in the case of bonding. Even in the case where this relative improvement is less noticeable, this plasma surface treatment method makes it possible to replace the treatments with corrosive chemicals and thus eliminate the risks associated with the use of such products.
• the process according to the invention also applies, as has already been pointed out, to improve the corrosion resistance of the products thus treated, in particular of stainless steel sheets.

Applications Claiming Priority (2)

Publications (1)

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Cited By (3)

Citations (4)

• 1989
  • 1989-10-17 FR FR8913879A patent/FR2653137B1/fr not_active Expired - Fee Related
• 1990
  • 1990-10-08 EP EP90402793A patent/EP0424211A1/de not_active Withdrawn
  • 1990-10-15 KR KR1019900016324A patent/KR910008160A/ko not_active Application Discontinuation
  • 1990-10-16 CA CA002027703A patent/CA2027703A1/en not_active Abandoned
  • 1990-10-17 JP JP2278868A patent/JPH03207872A/ja active Pending

Patent Citations (4)

Non-Patent Citations (3)

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