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
  • C23C12/00—Solid state diffusion of at least one non-metal element other than silicon and at least one metal element or silicon into metallic material surfaces
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12535—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.] with additional, spatially distinct nonmetal component
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12535—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.] with additional, spatially distinct nonmetal component
  • Y10T428/12576—Boride, carbide or nitride component
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12535—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.] with additional, spatially distinct nonmetal component
  • Y10T428/12597—Noncrystalline silica or noncrystalline plural-oxide component [e.g., glass, etc.]
  • Y10T428/12604—Film [e.g., glaze, etc.]

Definitions

• the technical sector of the present invention is that of surface treatments of the surface layers of steel parts in order to improve their mechanical properties. More particularly, the technical sector of the present invention relates to treatments which aim to increase the resistance to wear of structural steel parts and tool steel subjected to friction.
• coatings having good wear resistance are obtained.
• These coatings generally consist of layers based on chromium carbides M 23 C 6 and M 7 C 3 , M denoting a metal which apart from the chromium (Cr) can be iron (Fe), molybdenum (Mo) vanadium (V) etc.
• the layers obtained have a limited thickness; for example the layers obtained by chromizing treatment on steels having a carbon content of at least 0.15% have a total thickness of carbides of the order of 10 to 15 ⁇ m.
• the lifetime of a system, thus treated, and subjected to friction depends on the kinetics of wear of this layer of carbides. For a given stressing mode, this lifetime is linked, on the one hand, to the total thickness of the hard surface layer, on the other hand, to the crystallization morphology of the carbides M 7 C 3 .
• M 7 C 3 has a columnar structure which is harmful to good wear resistance. Furthermore, in the case of dry friction contact with antagonists of lesser hardness, these undergo very significant wear.
• the aim of the present invention is to produce a surface coating of steel parts which improves the wear resistance of the part subjected to friction and makes it possible to increase the service life of systems subjected to friction while limiting the wear of the antagonists in contact by friction with said parts.
• the subject of the present invention is a method of treatment against surface wear of steel parts with a carbon content of at least 0.15%, characterized in that a supply of sulfur is successively carried out on this surface of a metallic sulfide and chromium-plating in the vapor phase.
• the addition of sulfur, by depositing the metal sulphide on the surface of the steel, is preferably done by depositing a varnish based on molybdenum disulphide or by depositing an iron-molybdenum alloy sulphide of formulation ( fe Mo) 3 S 4 .
• an iron-molybdenum deposition is carried out prior to the deposition of iron-molybdenum sulfide.
• Chromization is carried out at 950 ° C for 15 hours and without the flow of hydrogen.
• hydrogen can desulfurize the deposit by the formation of H 2 S and thus prevent the formation of chromium sulfide on the surface of the substrate.
• the coating obtained by the process according to the invention is characterized in that it consists of a surface layer of chromium-molybdenum sulfide, the molybdenum being substituted in the hexagonal network of chromium sulfide at the rate of a mass content less than 18% and a layer underlying the surface layer consisting of chromium carbides M 23 C 6 and M 7 C 3 .
• the carbide layer is made up of two sublayers consisting successively of chromium carbide M 23 C 6 and chromium carbide M 7 C 3 .
• the chromium carbide underlay M 7 C 3 is recrystallized over part of its thickness at from the substrate.
• the steel used for this description is the low alloy steel 35CD4, widely used in industrial manufacturing. Any other steel with a carbon content of at least 0.15% could be used.
• the sequenced processing according to the invention comprises two parts, the order of which must be respected.
• the first part of this treatment consists of a treatment making it possible to deposit a sulphide of the iron-molybdenum sulphide or molybdenum sulphide type.
• the treatment mode only matters with regard to the uniformity in thickness and distribution of the deposit. It is thus possible to carry out deposits of the varnish type based on molybdenum disulphide or to carry out deposits by the “sprettering-magnetron” technique of (Fe-Mo) 3 S 4 .
• the latter technique allows good control of the thickness and distribution of the initial deposit.
• a deposit of at least 5 ⁇ m is necessary to obtain good results.
• a thickness of 8 to 15 ⁇ m is best suited to the conditions of subsequent chromization.
• the chromizing treatment is carried out according to average parameters such as:
• the external sulphide layer formed from the (Cr, Mo) S phase which crystallizes in the hexagonal system, is quite heterogeneous as regards its distribution of molybdenum and sulfur.
• the iron is almost zero in content and molybdenum at a rate of at most 18%.
• the underlying carbide layer is divided into two carbide sublayers M 23 C 6 and M 7 C 3 .
• the latter carbide, rich in molybdenum, is partially recrystallized.
• the iron was therefore pumped from the initial deposit of iron-molybdenum-sulfur, to give rise to deposit of chromium.
• This last element diffusing through the whole of the initial deposit, has migrated to the substrate interface to form there with the carbon of the steel, the sequence of carbides obtained in conventional chromization, with however some different characteristics.
• the M 23 C 6 carbide sublayer is much larger here and the M 7 C 3 carbide is partially recrystallized.
• the general morphology of the layers is in the form of crystals with a spherular front. These crystals are distributed in domains separated by fairly shallow "channels".
• the coating is divided into two main layers A and B with respective thicknesses of 9 ⁇ m, for a total thickness of 18 ⁇ m.
• Layer A has a two-phase appearance with basaltic domains. These areas are generally set back from the outside surface. They correspond to channels.
• Layer B consists of two sublayers Bi and B 2 ; revealed after basic attack, these sub-layers correspond to carbides; the sublayer 8 2 has the typical morphology of the carbide M 7 C 3 with recrystallization.
• Layer A consists essentially of the elements chromium, sulfur, molybdenum.
• the two-phase aspect observed in metallography seems to be due only to relative variations in sulfur and molybdenum.
• the iron is almost zero in content, and molybdenum up to 18%.
• the hardness of this phase is 777 ⁇ 50 Hv0.02.
• Layer B is made up of two layers formed of carbides where no sulfur is detected.
• the chromium concentration levels and the shape of the carbon distribution profiles indicate that the sublayers B i and B 2 correspond respectively to the carbides M 23 C 6 and M 7 C 3 . It should be noted that the molybdenum content in these carbides is high. But molybdenum can largely replace this type of phase.
• the carbide M 7 C 3 is in this case partially recrystallized, which ensures an increase in toughness to this layer of carbide.
• the hardness of carbide M 23 C 6 is 1400 ⁇ 200 Hv0.02, that of carbide M 7 C 3 is 2700 ⁇ 500 Hv0.02, for the recrystallized domain.
• the advantage of the invention resides in the fact that it is possible to increase the overall performance of wear resistance of systems subjected to dry friction or poorly lubricated. Furthermore, this gain in quality can be acquired from various implementation techniques without fundamentally modifying the characteristics obtained. A change in technology for carrying out the conventional chromization treatment requires only a fine-tuning of the parameters, which is of obvious interest from an economic point of view.
• the economic benefit also lies in improving the service lives and reliability of the parts.
• the invention can be applied to any moving mechanical system, made of steel, in particular weapon mechanisms or engine transmission mechanisms, etc.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physical Vapour Deposition (AREA)
• Other Surface Treatments For Metallic Materials (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=9262784

Family Applications (1)

Country Status (4)

Families Citing this family (2)

Family Cites Families (6)

• 1981
  • 1981-10-06 FR FR8118780A patent/FR2514034A1/fr active Granted
• 1982
  • 1982-09-30 EP EP82401774A patent/EP0076745B1/fr not_active Expired
  • 1982-09-30 US US06/428,661 patent/US4435227A/en not_active Expired - Lifetime
  • 1982-09-30 DE DE8282401774T patent/DE3267828D1/de not_active Expired

Also Published As

Similar Documents

Legal Events