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
  • 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
• • 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
  • C23C8/08—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 only one element being applied
  • C23C8/20—Carburising
• • 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
  • C23C8/08—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 only one element being applied
  • C23C8/24—Nitriding

Definitions

• the present invention relates to a method for forming, by processing thermochemical without plasma, a surface layer having a hardness high and with tribological properties, on alloy parts sensitive or reactive towards nitrogen, carbon and / or oxygen.
• a titanium-based alloy or zirconium in an atmosphere which may include ammonia, a hydrocarbon and / or an oxidizing gas or even a gaseous composition including one or more of these compounds.
• thermochemical treatments of this kind In general, we know that there are currently various techniques thermochemical treatments of this kind.
• the oldest, namely the salt bath tends to disappear from the fact that it is particularly polluting and dangerous due to the release of toxic gases and rinsing water it generates.
• ion bombardment treatments involve a relative vacuum heat treatment installation specially equipped with so as to generate a luminescent discharge on the parts to be treated in a process gas atmosphere.
• This technique has the disadvantage of being relatively expensive and not suitable for complex shaped parts and, in particular, tubular in shape due to the hollow cathode.
• thermochemical treatments carried out under a gaseous atmosphere at atmospheric pressure such as gaseous nitriding, consist of carrying the parts at a temperature of the order of 500 ° C to 600 ° C and to sweep them with a gas nitriding such as ammonia.
• This treatment has the disadvantage of being long, to consume large amounts of process gas and therefore to be relatively polluting.
• This process which provides excellent results for the treatment of steel and steel alloys has the disadvantage of using a relatively expensive process gas composition and installation sophisticated to ensure uniform scanning of the parts to be treated by gases treatment.
• Another disadvantage of this process lies in the fact that in temperature and pressure conditions suitable for processing steel it does not work on titanium or zirconium alloys.
• the catalyst used is incompatible with the treatment of titanium and zirconium alloys because it would form a diffusion barrier to nitrogen (layer of Ti or Zr oxide)
• the object of the invention is a method for treating this type of alloy.
• a treatment method consisting in bringing the pieces to treat at a temperature above 500 ° C inside an enclosure whose the atmosphere is maintained at a pressure less than or equal to 0.1 mbar, at inject a treatment gas comprising ammonia and / or a hydrocarbon and / or an oxidizing gas, the pressure inside the enclosure then establishing itself at a value below atmospheric pressure, but greater than 100 bar for a period which can range from a few tens minutes to more than 24 hours, depending on the depth of treatment desired.
• This treatment makes it possible both to improve the mechanical characteristics of the parts treated, in particular as regards resistance to friction and surface hardness, and to give them a pale yellow more or less shiny appearance, particularly aesthetic.
• This aspect is a function of the initial surface state and the stoichiometry of the Ti x N y layer.
• this processing is a diffusion processing: it therefore does not generate significant modification of the initial roughness of the parts and it eliminates any risk of separation of the titanium nitride layer.
• Another advantage of this process is that the fact that it operates at low pressure (always lower than atmospheric pressure) it consumes only very little treatment gas and is therefore not polluting in relation to the processes high pressure which require the use of specific ovens and constraints of safety due to high pressure.
• the process according to the invention may also include a post-processing phase intended to dehydrogenate the treated alloy.
• This dehydrogenation treatment can be carried out by bringing the parts to a temperature of the order of 700 to 900 ° C. for a period which can range from 1 to 5 hours, in a vacuum of 10 -3 to 10 -4 mbar.
• a titanium alloy of the TH6V type, dehydrogenated at 790 ° C. for 2 hours, under vacuum of 5 10 -4 mbar will see its hydrogen content drop from 256 to 11 ppm.
• the treatment installation used involved a vacuum treatment of conventional structure equipped with a turbine circulation of process gases.
• This oven includes a sealed enclosure containing a muffle made of a material (metal or graphite) which cannot retain polluting elements (in particular oxygen or water vapor) likely to affect the quality of treatment.
• a muffle made of a material (metal or graphite) which cannot retain polluting elements (in particular oxygen or water vapor) likely to affect the quality of treatment.
• electrical heating resistors mainly by radiation and convection
• This enclosure is connected on the one hand to pumping equipment capable of achieve a primary vacuum P ⁇ 0.1 mbar and, on the other hand, two gas sources (one nitrogen source and ammonia source) through a distribution.
• the parts to be treated (here prostheses made of alloy titanium TA6V) were placed in the muffle, preferably on a mounting titanium alloy having previously undergone the same treatment.
• the rooms On this assembly the rooms have been arranged so as to be spaced from each other by a few millimeters so that the diffusion is the most homogeneous possible on their surface.
• the temperature of the nitrogen convection oven (injected from the nitrogen source) and / or by radiation (resistances) until a temperature level between 500 ° C and 900 ° C, here of the order of 900 ° C.
• Temperature maintenance at this level was continued for a sufficient period of time to ensure the homogeneity of the room temperature.
• a primary vacuum was then applied to the enclosure to ensure elimination of the nitrogen previously injected and then at the start of the diffusion thanks to an ammonia injection at a pressure P between 100 and 900 mbar, here 300 mbar, the temperature being above 500 ° C.
• This dissemination phase was continued for approximately 7 hours so as to obtain a diffusion layer of approximately 0.040 mm in average thickness.
• the treated parts exhibited on the extreme surface a compact and homogeneous yellow layer of titanium nitride Ti x N y with a thickness of the order of 4 ⁇ m and very high hardness (> 1000 HV), and therefore very good resistance to friction. and excellent wear resistance.
• the diffusion layer (a few hundredths of a millimeter thick and hardness> 400 HV) was then likely to improve the resistance to fatigue (the hardness at the core being 339 HV)
• An important advantage of this process is that it provides a very good homogeneity of the treatment even in the case of shaped parts and complex geometries including hollow shapes.
• the treatment extends to the contact areas of the parts on their support.
• the treatment gas could be other than ammonia and could for example consist of a hydrocarbon-based atmosphere (C 2 H 2 , C 3 H 8 , CH 4 ....) in order to cement superficially these alloys.
• a surface layer of metallic gray color of great hardness and having increased tribological properties, is obtained.
• the treatment atmosphere could include an oxidizing gas such as oxygen so as to obtain a surface layer (Ti0, Ti0 2 , Ti 2 0 3 , Zr0 2 ..) having various colors (blue, green, purple ) and great hardness.
• an oxidizing gas such as oxygen so as to obtain a surface layer (Ti0, Ti0 2 , Ti 2 0 3 , Zr0 2 ..) having various colors (blue, green, purple ) and great hardness.
• This layer of Ti x O y oxide is compact and homogeneous over the entire surface of the part.
• the colors that we obtain are brilliant and very varied. It considerably improves the friction resistance of the parts.
• the appearance of the parts is a function of the initial surface condition and the stoichiometry of the layer of Ti x O y .
• the treatment atmosphere could also consist of a combination of NH 3 + CH 4 so as to obtain a surface layer of carbonitrides TiC x N y or Zr CN of pink or butter color.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
• Carbon And Carbon Compounds (AREA)

Applications Claiming Priority (2)

Publications (3)

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ID=9507313

Family Applications (1)

Country Status (4)

Cited By (4)

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Family Cites Families (7)

• 1997
  • 1997-05-23 FR FR9706518A patent/FR2763604B1/fr not_active Expired - Lifetime
• 1998
  • 1998-05-22 DE DE1998631530 patent/DE69831530T2/de not_active Expired - Lifetime
  • 1998-05-22 EP EP19980401235 patent/EP0885980B1/de not_active Expired - Lifetime
  • 1998-05-22 ES ES98401235T patent/ES2247665T3/es not_active Expired - Lifetime

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